ANSI-AGMA-2004-B89-Gear-Materials-and-Heat-Treatment-Manual.pdf

ANSI/AGMA 2004---B89(Revision of AGMA 240.01) January 1989 Reaffirmed October 1995 AMERICAN NATIONAL STANDARD Gear Materials and Heat Treatment Manual Gear Materials and Heat Treatment Manual Gear Materials And Heat Treatment Manual AGMA 2004---B89 (Revision of AGMA 240.01) [Tables or other self---supporting sections may be quoted or extracted in their entirety. Credit lines should read: Extracted from AGMA 2004---B89, Gear Materials and Heat Treatment Manual, with the permission of the publisher, the American Gear Manufacturers Association, 1500 King Street, Suite 201, Alexandria, Virginia 22314.] AGMA Standards are subject to constant improvement, revision or withdrawal as dictated by experience. Any person who refers to an AGMA Technical Publication should be sure that the publication is the latest avail- able from the Association on the subject matter. ABSTRACT The Gear Materials and Heat Treatment Manual provides information pertaining to engineering materials and material treatments used in gear manufacture. Topics included are definitions, selection guidelines, heat treatment, quality control, life considerations and a bibliography. The material selection includes ferrous, non- ferrous and nonmetallic materials. Wrought, cast, and fabricated gear blanks are considered. The heat treat- ment section includes data on through hardened, flame hardened, induction hardened, carburized, carboni- trided, and nitrided gears. Quenching, distortion, and shot peening are discussed. Quality control is discussed as related to gear blanks, process control, and metallurgical testing on the final products. Copyright E, 1989 Reaffirmed October 1995 American Gear Manufacturers Association 1500 King Street, Suite 201 Alexandria, Virginia 22314 February 1989 ISBN: 1---55589---524---7 ANSI/AGMA ii 2004---B89 Gear Materials and Heat Treatment Manual FOREWORD [The foreword, footnotes, and appendices, if any, are provided for informational purposes only and should not be construed as part of AGMA Standard 2004---B89 (Formerly 240.01), Gear Materials and Heat Treatment Manual.] The Standard provides a broad range of information on gear materials and their heat treatment. It is in- tended to assist the designer, process engineer, manufacturer and heat treater in the selection and processing of materials for gearing. Data contained herein represents a consensus from metallurgical representatives of mem- ber companies of AGMA. This Standard replaces AGMA 240.01, October 1972. The first draft of AGMA 240.01, Gear Materials Manual, was prepared in October 1966. It was approved by the AGMA membership in March 1972. Reprinting of AGMA 240.01 for distribution was discontinued in 1982 because it had been decided in 1979 by the Metallur- gy and Materials Committee to revise its format. The initial draft of AGMA 2004---B89 (formerly 240.01) was completed in April, 1983. Work continued on the Standard with numerous additional revised drafts within the Metallurgy and Materials Committee until it was balloted in 1988. It was completed and approved by the AGMA Technical Division Executive Committee in September 1988 and on January 23, 1989 it was approved as an American National Standard. Suggestions for the improvement of this standard will be welcome. They should be sent to the American Gear Manufacturers Association, 1500 King Street, Suite 201, Alexandria, Virginia 22314. ANSI/AGMA iii 2004---B89 L. Houck (Mack Trucks) T. I. L. Bonnet (WesTech) R. Abney (Fairfield Manufacturing) N. Smith (Invincible Gear) W. B. Burrell (Metal Improvement Co. E.) W. R. M. Berndt (C and M of Indiana) P. L. D. Wiskow (Falk) ACTIVE MEMBERS M. Partridge (Lufkin) H. Jr. Horvath (G. Vaglia (Farrel Connecticut) L. Lemanski (Sikorsky) ANSI/AGMA iv 2004---B89 .Muncie) D. J. Tipton (Caterpillar) J. E. L. K. Cunningham (Boeing) M. Winterrowd (Cummins Engine) A.Seattle) ASSOCIATE MEMBERS T. Gear Materials and Heat Treatment Manual PERSONNEL of the AGMA Committee for Metallurgy And Materials Chairman: L. Chevrolet --. S. G. (Gleason) A. Arnold (Xtek. Leslie (SPECO Corporation) J. Hillman (Westinghouse. Swiglo (IPSEN) A. Craig (Cummins Engine) H. Witte (General Motors) D. Olson (Cleveland) P. Black (General Motors) B. C. Milano (Regal Beloit Corporation) R. R. Giammarise (General Electric) S. E. Starozhitsky (Outboard Marine) P. Rivart (CLECIM) J. K.) Vice Chairman: G. Glew (Prager) R. Gayley (IMO Delaval) E. Inc. P. Guttshall (IMO Delaval) L.Seattle) E. H. Shoulders (Reliance Electric) (Deceased) R. H. Inc. J. Early. McVittie (The Gear Works --. R. Shapiro (Arrow Gear) N. L. J.) D. J. Carrigan (Emerson Electric) G. E. J. Bergquist (Western Gear) R. P. M. Rickt (Auburn Gear) J. Sanderow (Supermet) T. Vukovich (Eaton) J. Bruce Kelly (General Motors) L. Inc. Hoffmann (Dresser) R. L. Heller (Peerless Winsmith) Y. F. Air Brake) M. L. A. Schwettman (Xtek. Milburn (The Gear Works --. Cary (Metal Finishing) J. D. A. Andreini (Earle M. Mumford (Alten Foundry) E. Jorgensen) A. Sueyoshi (Tsubakimoto Chain) D. Tanaka (Nippon Gear) B. W. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4. . . . . 25 5. . . . . . . . . . . . . . . . .8 Mechanical Property Test Bar Considerations . . . . . . . . . . . . . . . . . . . . Mechanical and Non---Destructive Tests and Inspections . . . . . . . . . . . . . . .11 Other Non---Ferrous Materials . . . . . . . . . . . . . . . . . .1 Through Hardening Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Ferrous Gearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 Information Sources . 9 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Carbonitriding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. . . .6 Hardenability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 6. . . . . . . . . . . . . . . 7 4. . . . . . . . . 47 5. . . . . . . . . . . . . . . . . . . . .5 Nitriding . . . . . . . . . . . . . . . . . 1 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 5. . . . . . . . 52 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 5. . .6 Metallurgical. . . . . . . . . . . . . . . . Metallurgical Quality Control . . . . . . . . . . . . . 25 5. . . . . . . . 6 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 6. . . . . . . . . . . . . . . . . . . . . . . Materials Selection Guidelines .10 Residual Stress Effects . . .4 Dimensional Stability . . . . . . . . . . . . . . . . . . . . . . .3 Incoming Material Mechanical Tests . . . .9 Selection Criteria for Wrought. . . . . .1 Incoming Material Quality Control . . . . 5 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 Incoming Material Hardness Tests . . . . . . . .12 Non---Metallic Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . or Fabricated Steel Gearing . . . . . 56 6. . . 53 6. . . . . . . . . .2 Grade and Heat Treatment . . . . . Cast. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 Mechanical Properties . . . . . . . . . . . . . . . . . . . . . . . . .8 Distortion . . . . . . . . . .7 Microstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 Carburizing . . . . . . . . . . . . . . . . . . . 53 6. 5 4. . . . . . . . . . .5 Part Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 6. . . . . . . . 51 6. . . . . . . . . . . . . . . . . . . 39 5.1 References . . . . . . . . . . . . . . . .6 Other Heat Treatments . . . . . . . . . . . . Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heat Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 5. . . . . . . . . . . . . . . . . .7 Machinability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 Cost and Availability . . . . . . . . . . . . . . . 61 6. . . . . . . . . . . . . . . . . . . 42 5. . . . . . . . . . . . 63 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2. . . . . . . . . . . . . . . . . . . . . . . . . . 2 4. . . . . . . . . . . . References and Information . . . . . . . 42 5. . . . . . . . . . . . . . . 1 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 5. . .9 Shot Peening . . . . . . . . . . . 19 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 ANSI/AGMA v 2004---B89 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4. . . . . . . . . . . . . Gear Materials and Heat Treatment Manual Table of Contents Section Title Page 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Heat Treat Process Control . . .3 Cleanliness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 Flame and Induction Hardening . . . . . . . . . . . . . . . .10 Copper Base Gearing . . . . . 38 5. . . . . . . . . . . . . . . . .7 Quenching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Table 5---4 Approximate Minimum Surface Hardness --. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Table 4---11 Typical Mechanical Properties of Wrought Bronze Alloy Rod and Bar . . . . 38 Table 5---3 Approximate Minimum Core Hardness of Carburized Gear Teeth . . . . . . . . . . . . . . . . . . . . 69 Appendix D Service Life Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Appendix C Case Hardenability of Carburizing Steels . . . . . . . . . . . . . . . . . 23 Table 4---13 Mechanical Properties of Cast Bronze Alloys . . . . 50 ANSI/AGMA vi 2004---B89 . . . . . . . . . . . . 10 Table 4---5 Mechanical Property Requirements --. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Table 5---5 Commonly Used Quenchants for Ferrous Gear Materials . . . . . Stress Relieved Steel Bars (Special Cold Drawn. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Table 5---1 Test Bar Size for Core Hardness Determination . . . . . . . . . . . . . . . . . . . 7 Table 4---3 Typical Brinell Hardness Ranges and Strengths for Quenched and Tempered Steel Gearing . . . . . . . . . . . . . . . . . . Gear Materials and Heat Treatment Manual Table of Contents Section Title Page Appendices Appendix A Plastic Gear Materials . . . . . . . . . . . . . . . . . . . . . . . . .Cold Drawn. . . . . . . . . . . . . . . . . . 17 Table 4---10 Chemical Analyses of Wrought Bronze Alloys . . . . . . . . . . . . . . . . . . . . . . . . High Tensile) . . . . . . . . . . . . . . . . . . . . . . . . . 8 Table 4---4 Machinability of Common Gear Materials . . . . . . . . . . . . . . . . . . Normalized & Tempered Steel Gearing . . . . . . . . 14 Table 4---8 Minimum Hardness and Tensile Strength Requirements for Gray Cast Iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Table 4---7 Tensile Properties of Through Hardened Cast Steel Gears . . . . . . . . . . . . . . . . . . . . . . 22 Table 4---12 Chemical Analyses of Cast Bronze Alloys . . . . . . . . . . . . . . . . 35 Table 5---2 Typical Effective Case Depth Specifications for Carburized Gearing . . . . . 16 Table 4---9 Mechanical Properties of Ductile Iron . . . . . . . . . . . . . 43 Table 5---6 Typical Shot Size and Intensity for Shot Peening . . . . . . 11 Table 4---6 Typical Chemical Analyses for Though Hardened Cast Steel Gears . . . . . . . . . . .Nitrided Steels . . . . . . . . . . . . . . . . . 6 Table 4---2 Typical Brinell Hardness Ranges and Strengths for Annealed. . . . 65 Appendix B Approximate Maximum Controlling Section Size Considerations for Through Hardened Gearing . . . . . . . . . . . . . . . . . . . . . . .Wrought Steel . . . . 70 Tables Table 4---1 Typical Gear Materials --. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Fig 5---7 Residual Stress by Peening 1045 Steel at 62 HRC with 330 Shot . . . 62 ANSI/AGMA vii 2004---B89 . . . . . . . . . . . . . . . . . . . . Gear Materials and Heat Treatment Manual Table of Contents Section Title Page Figures Fig 4---1 Typical Design of Cast Steel Gears . . . . . . . . . . . . 50 Fig 6---1 Circular (Head Shot) Magnetic Particle Inspection . . . 29 Fig 5---2 Variations in Hardening Patterns Obtainable on Gear Teeth by Induction Hardening . . . . . . . . . . . . . . . . 58 Fig 6---2 Coil Shot Magnetic Particle Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Fig 6---4 Distance---Amplitude Reference Line for Ultrasonic Inspection . . 20 Fig 5---1 Variation in Hardening Patterns Obtainable on Gear Teeth by Flame Hardening . . . . . . . . . . . . . . . . . 59 Fig 6---3 Ultrasonic Inspection Oscilloscope Screen . 46 Fig 5---6 Shot Peening Intensity Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Fig 5---8 Depth of Compressive Stress Versus Almen Intensity for Steel . . . . 30 Fig 5---3 Recommended Maximum Surface Hardness and Effective Case Depth Hardness Versus Percent Carbon for Flame and Induction Hardening . . . . 45 Fig 5---5 Typical Distortion Characteristics of Carburized Gearing . . . . . . . . . . . . 33 Fig 5---4 General Design Guidelines for Blanks for Carburized Gearing . . . . . . . . . . . . . . . . . . . . 13 Fig 4---2 Directionality of Forging Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gear Materials and Heat Treatment Manual (This page is intentionally left blank) ANSI/AGMA viii 2004---B89 . Specification for Ductile Iron provisions of this document. Recommended Prac. Special Brasses and Bronzes ings ASTM E112---84. Test Methods for Rockwell Hard- Worm Speed Reducers ness and Rockwell Superficial Hardness of Metallic ASNT---TC---1A (June 80). Gear Materials and Heat Treatment Manual 1. Indentation Hardness of Metal- ject to revision. Alloy. lar) Iron Castings leable Iron Castings SAE J461---Sept 81.1 References. burizing Steels for Anti---Friction Bearings neers. and Stainless Steel Castings for Steam Turbines ASTM A370---77. And Other Methods. ASTM A534---87. constitute ASTM A536---80. Plastics Gearing --. The abbreviations for Selection of Steel Bar Compositions According to include: AGMA. and the users of this Standard are en. Steel Castings. Recommended Practice for Ul- 2. Scope ASTM A290---82. Castings tion. tallic Materials sion Gear Units. Specification for Gear Bronze the State of the Art Alloy Castings AGMA 2001---B88. Specification for Copper---Base and Calculation Methods for Involute Spur and Helical Alloy Continuous Castings Gear Teeth ASTM E8---83. Low but. Practice for Single and of Metallic Materials Double Reduction Cylindrical ---Worm and Helical --. ASTM. are covered in AGMA rating standards. Standard Specification for Spe- The following documents contain provisions cial ---Quality Ball and Roller Bearing Steel which. and other considerations related to the ASTM A311---79. Method for Chemical Analysis of ASTM A48---83. Carbon and Low Alloy Ultrasonic Examinations AGMA 141. At the time of publica. Recommended Practice cific documents in this Standard. Cast Copper Alloys ANSI/AGMA 1 2004---B89 . their treat- ments. Methods for Determining Aver- ASTM A148---84. References and Information Mechanical Testing of Steel Products ASTM 388---80. ASNT. Fundamental Rating Factors ASTM B505---84. Society of Automotive Engi. Method for End---Quench Test Alloys for Hardenability of Steel SAE J462---Sept 81. Carbon and Alloy Steel Forg- ings for Rings for Reduction Gears This Manual was developed to provide basic in- ASTM A310---77. Cold Drawn Carbon Steel Bars Subject to Mechanical Property Requirements Metallurgical aspects of gearing as related to rat- ing (allowable sac and sat values) are not included. Methods and Definitions for formation and recommend sources of additional in- Mechanical Testing of Steel Products formation pertaining to gear materials. Standard Specification for Car- ing Materials. Machined. ASTM A833---84. Test Method for Brinell Hardness ANSI/AGMA 6034---A88. through reference in this Standard. lic Materials by Comparison Hardness Testers couraged to investigate the possibility of applying the ASTM A609---83. Thereof Molded. Heavy---Walled Carbon. High age Grain Size Strength. Methods of Tension Testing of Me- AGMA 6033---A88. the editions were valid. Materials tice by American Society for Nondestructive Testing ASTM E54---80. All publications are sub. for Structural Purposes SAE J434---June 86. ASTM A535---85. Methods and Definitions for 2. Part 1 Materials ASTM E10---78. American Society of Nonde- structive Testing. Specification for Gray Iron Cast. Wrought and Cast Copper ASTM A255---67. Standard for Marine Propul. American Gear Manufacturers Section Association.01---1984. ASTM A356---84. SAE. most recent editions of the publications listed. American Society for Test. trasonic Examination of Heavy Steel Forgings Abbreviations are used in the references to spe- ASTM A400---69(1982). Automotive Ductile (Nodu- ASTM A220---76. A Report on ASTM B427---82. Specification for Steel Castings. Specification for Stress Relieved manufacture and use of gearing. ASTM E18---79. Specification for Pearlitic Mal. sufficiently high to prevent high temperature trans- signer use a source of metallurgical knowledge of ma. Manual on Shot Peen. ANSI/AGMA 2 2004---B89 . Shot Peening of Metal Parts American National Standards Institute MIL---STD---271F. assumed to mean full annealing. technical societies.Spheroidizing. range is below the pearlitic range. Austenite in ferrous alloys is a micro- ASM Heat Treaters Guide structural phase consisting of a solid solution of car- ASM Metals Reference Book bon and alloying elements in face---centered cubic ASM Standard crystal structured iron. Austempering.4. Magnetic Particle Examination Military Standards and Specifications ASTM E125. Unless otherwise stated. Requirements for Nondestruc. large industrial users. Magnetic Particle In- microstructure for machinability of low and medium spection. formation products.8. some of whom are: more recently in the development stage for ductile ASM International iron gearing (refer to 4. Society of Automotive Engineers. but is intended to be a basic tool to assist in the selection and metallurgical processing of gear mate. Standard Reference Radio. ANSI Standards tive Testing Methods Naval Publications and Forms Center ASTM E709---80. Design of gears is concerned with the selection This heat treatment results in the best machinability of materials and metallurgical processing. and maintaining the alloy tem- terials and processing. annealing is ANSI/SAE AMS 3201 G. Definitions Fracture Toughness of Metallic Materials Annealing --. spection. Premium Aircraft ---Quality Steel Cleanliness carbon steels. The material information and metallurgical cess consisting of quenching a ferrous alloy (steel or processes contained herein are based on established ductile iron) from a temperature above the trans- data and practices which can be found in the ap. This treatment forms coarse lamellar pearlite. tise. Full annealing consists of ASTM E446---81. generally below 600_F (316_C). perature within the bainitic range until desired trans- formation is obtained. Standard Reference Radio- graphs for Heavy Walled (4 1/2 to 12 inch)(114 to 305 Steel Founders’ Society mm) Steel Castings Steel Castings Handbook ASTM E399---83. Standard Reference Radio. heating steel or other ferrous alloys to 1475---1650_F graphs for Steel Castings Up to 2 inch (51 mm) in (802---899_C) and furnace cooling to a prescribed Thickness temperature. ing SAE Handbook American Iron and Steel Institute MIL---S---13165 B (31 Dec 66 Amendment 2---25 AISI Steel Products Manuals June 79).2 Information Sources. and tensitic range. Copper Development Association graphs for Heavy Walled (2 to 4 1/2 inch)(51 to 114 CDA Data books mm) Steel Castings Iron Castings Society Gray and Ductile Iron Castings Handbook ASTM E280---81. Magnetic Particle In. annealing is a process of heating and cooling steel that produces a globular carbide in a ferritic matrix.Full. Austempering is a heat treat pro- rials. Inc.60 percent carbon or higher) and Manual cannot substitute for metallurgical exper- alloy steels.3). Gear Materials and Heat Treatment Manual SAE J463---Sept 81. It is necessary that the de. Reference Photographs for Magnet. The bainitic transformation Material specifications are issued by agencies. ASM Metals Handbooks Austenite. Wrought Copper and Copper American Society for Testing and Materials Alloys ASTM Standards SAE J808a---SAE HS 84. the best ANSI/SAE AMS 2300 F. This for high carbon (0. Metal Powder Industries Federation ic Particle Indications on Ferrous Castings MPIF Standard 35 ASTM E186---8. formation range in a medium having a rate of cooling propriate publications. Spheroidize 2. Austempering is applied to steels and. Test Method for Plain ---Strain 3. but above the mar- including the government. Aircraft ---Quality Steel Cleanliness Annealing --. lyzing the carbon level. etched tal form. This consists of an aggregate of ferrite and iron carbide. tion of complex nitrides in a high carbon case. total case depth. depth to which the carbon level of the case has de- sulting from the transformation of austenite. The temperature at case. tural phase transformation to austenite.I. The carburized case depth referred to in tooth design purposes is the hardness at the intersec- this Manual will be effective case depth. (1) Effective case depth. Case Hardness is the micro--- tained at the surface). Ideal critical di- depth is the hardened depth to HRC 50 at 0. in a microstructure consisting of 50 percent marten- (2) Etched case depth. Its appearance is feathery if formed in the upper por. Nitrided Carburizing--. This is defined as the depth at which the atmosphere. The effective case D. crohardness tester and measured normal to the tooth sphere. Carbon is the principal hardening ele. (4) Case depth to 0. The total case depth is the Bainite. and measuring the depth of the darkened tion in surface carbon content of a gear or test piece area. and is not as accurate a measurement as directly ana- crease. This results in simultaneous absorption hardness is 10 HRC points below the minimum speci- of carbon and nitrogen. or slow cooled and reheated to phase otherwise known as iron carbide (Fe3C) and 1475---1550_F (802---843_C) and quenched.70---1.5 tooth height and mid face width. Decarburization.40 percent carbon. will result face. This depth may be measured Carbon. by analyzing the carbon content or estimating based ment in steel. infinite quench severity (such as ice brine). Cementite is a hard microstructure quenched.Gas. in which steel (typically plain carbon and very low alloy) is heated between 1450---1650_F Case Depth of Flame or Induction Harden Com- (788---899_C) in an ammonia enriched carburizing ponents.5 times the effective case depth. Core Hardness. A modified form of gas carbu- gradients using this method. termined by etching a sample cross---section with ni.5 tooth height and mid face width. Carburized tion of the root diameter and the centerline of the case depth terms are defined as follows: tooth at mid face width on a finished gear. The Combined Carbon. on microstructure. Case Depth of Carburized Components. tensile strength and wear resistance in. Estimating based on microstruc- mum hardness obtainable. and depth to 0. Gas carburizing consists of case depth is defined as the depth at which the hard- heating and holding low carbon or alloy steel (less ness is equivalent to 105 percent of the measured than 0. rizing. when quenched in an height and mid face width.40 per. and creased to the carbon level of the base material.002 to 0. and it’s amount determines the maxi. are either cooled to 1475---1550_F (802---843_C) and held at this temperature to stabilize and then direct Cementite. parts mm) at 0. Generally as carbon is in. poses. ductility and weldability decrease. The amount of carbon in case depth for carburized gearing may be defined in steel or cast iron that is present in other than elemen- several ways including effective case depth. the part (0. (Ideal Critical Diameter). Temperatures above 1800_F hardness measured perpendicular to the tooth sur- (982_C) may be ultilized in specialized equipment face at a depth of 0. Decarburization is the reduc- tric acid. Gear Materials and Heat Treatment Manual Austenitizing Temperature. to 0. Effective tion of the bainite transformation range. which results in the forma. ANSI/AGMA 3 2004---B89 . The case depth is determined by a mi- (899---982_C) in a controlled carbonaceous atmo. fied surface hardness. which results in the diffusion of carbon into surface at 0.30 percent carbon) at 1650---1800_F core hardness. however. There is poor correlation be- tween microstructure readings and material strength Carbonitriding.004 inches (0. Case Depth of Nitrided Components. characterized by an orthorhombic crystal structure. ture ignores the hardenability of the base material creased. After carburizing. The etched case approximates the effective during thermal processing. site of the center of the bar. Etched case depth is de. Bainite is a microstructural phase re.10 such as vacuum carburizers. Core Hardness for AGMA cent carbon. and acicular case depth is less frequently referred to as the depth if formed in the lower portion. is approximately 1. (3) Total case depth.00 percent carbon is typically ob.40 percent carbon.5 tooth ameter is the diameter which. normal to the tooth sur. Case Hardness. Hardness survey is preferred for contral pur- which ferrous alloys undergo a complete microstruc.05 to 0. case depth. ductile. Maximum stress relief gonal structure. body centered cubic crystal structure. cold working. ture. and viewed at 100X or higher magnifi. 1275_F (690_C) to reduce hardness and increase trogen and carbon in varying concentrations are ab. hardenability range. or malleable. toughness. The test consists of heating a standard (802---899_C). or transformation of austenite to a body centered tetra. Surface hardening process in Grain Size. Pearlite is a microstructure consisting tance through the use of a coil or single tooth induc. Surface Hardness. needle---like appearance. Nitriding (Gas). cooling achieve the desired mechanical properties for the the specimen to room temperature. Pearlite. gearing involves oxyfuel burner heating to These processes are used mainly for improved wear 1450---1650_F (788---899_C) followed by quenching resistance and fatigue strength.Band Steels. other fabricating techniques. of lamellar layers of ferrite and cementite. machining.6 mm) in. The quench and temper Jominy End Quenching Hardenability Test. perature below the austenitizing temperature acterized with a body centered cubic structure. Flame Hardening of steel gas stirred and activated molten chemical salt bath. part to a specified temperature. fatigue properties. and tempering. Gear Materials and Heat Treatment Manual Ferrite (alpha). the austenite transformation state at 1475---1650_F ability of steel. Stress relief is a thermal cycle used tervals starting at the quenched end. Tempering. gear application. Grain size is specified as either which alloy steel. process on ferrous alloys involves heating a part to The standard method for determining the harden. Stress Relief. determined according to ASTM E112.6). [1000---1150_F (538---621_C)]. and is char. Microstructure is the material hardness measured directly on the surface. characterized by an acicular is achieved at 1100_F (593_C) minimum. Induction hardening of crostructure. placing the specimen in a fixture so cific temperature generally below 1275_F (690_C) to that a stream of water impinges on one end. and measuring the hardness at 1/16 inch (1. Surface Hardness is the Microstructure. Normalizing consists of heating H--. This term in. is subjected to a cracked ammonia through 8). Tempering is reheating a hardened Nitriding (Aerated Salt Bath). to relieve residual stresses created by prior heat Martensite. gearing is the selective heating of gear teeth profiles to 1450---1650_F (788---899_C) by electrical induc. generally below cludes a number of heat treat processes in which ni. ANSI/AGMA 4 2004---B89 . Normalizing is used primarily to obtain a uniform mi- Induction Hardening. cation. The part is then reheated (tempered) to a spe- temperature. spheroid. heat treatment in which both nitrogen and carbon Hardenability. An indication of the depth to are absorbed into the surface of a ferrous material at which a steel will harden during heat treatment (see a temperature below the austenitizing temperature 4. Graphite is carbon in the free state causing nitrogen to be absorbed into the surface. perficial test must be used. Ferrite is a microstructural sorbed into the surface of a ferrous material at a tem- phase consisting of essentially pure iron. or forming hard iron nitrides. welding. followed by rapid cooling (quench- one inch (25 mm) diameter test bar to a specified ing). after machining following quench coarse (grain size 1 through 4) or fine (grain size 5 and tempering. typically through heating and cooling. with a tor to obtain the proper heat pattern and tempera. furnace atmosphere at 950---1060_F (510---571_C) Graphite. Martensite is the diffussionless treatments. with a shape described as either flake. Quench and Temper. etched. nodule. while submerged in a Flame Hardening. grinding flats. Nitrocarburizing is a gaseous cast iron as either gray. followed by quenching and tempering. The graphite shape classifies the type of Nitrocarburizing. [1000---1150_F (538---621_C)]. The process of increasing hardness. Nitrocarburizing is done mainly for antiscuffing and to improve surface Hardening. a su- finish. Normalizing. To obtain structure observed on a sample polished to a mirror accurate results on shallow case hardened parts. H---Band steels are steels which steel or other ferrous alloys to 1600---1800_F are produced and purchased to a specified Jominy (871---982_C) and cooling in still or circulated air. tensile ductility and/or fracture normalizing and tempering) and quenching and tem- toughness testing.1. treatment of steel other than surface hardening tech- 4. as the gear it represents. forgings and barstock have a surface layer tigue strengths are used to predict. Gear blanks can also be ness is an important consideration for bending and quenched and tempered.1. Toughness is determined by niques. Through hardening is a the stress level above which permanent deformation term used to collectively describe methods of heat occurs.3 Tensile Strength. level. material cleanliness. which homogenizes AGMA gear rating practice. pickled. It is not hardenability limits. (2) Improper heat treatment or microstruc--- Transformation Temperature. should be removed from critical gearing surfaces. cold rolled. mi. Yield strength determines Through Hardening.1. Minimum ANSI/AGMA 5 2004---B89 . Contact and bending fa. seams. and quenched and tem- 4. material defects. annealed. gear(s) it represents. The recommended for use in gear manufacturing specifi- test coupon should be heat treated along with the cations. the number of cycles that gearing can be ex. cold drawn. It is necessary for the Round and flat stock can be purchased in numerous gear designer to know the application and design combinations of mechanical and thermal processing. impact strength. It should be of the same speci. etc.2 Fatigue Strength. Contact and bending fatigue strengths are in. Most wrought ferrous (7) Machinability and Other Manufacturing materials used in gearing are heat treated to meet Characteristics hardness and/or mechanical property requirements.1 Hardness. Surface hardness is an the micro--. (6) Hardenability and Size Effects 4. Gear blanks are generally given an annealing closely related to material hardness. The strength properties are pered. A test coupon is an appropriately crostructure. small fillet radii.1.7 Stock Removal. 4. The minimum surface stock removal varies with fluenced by a variety of factors such as hardness. tool (4) Dimensional Stablility marks. castings. Core hard. lieved. Depth of hardening is depen- in gear rating.1. All rough ferrous gear 4.4 Yield Strength. (3) High sulfur (4) High phosphorus and embrittling type 4. Gear Materials and Heat Treatment Manual Test Coupon.. considerations. These factors include: nickel. stress re- selection can begin. Toughness of steel gearing is adversely affected by a NOTE: Through hardening does not imply that variety of factors such as: the part has equivalent hardness throughout the en. loads and to calculate the stresses before the material such as hot rolled.1). which act as (5) Availability and Cost stress concentrators).1. The temperature ture at which a change in microstructure phase occurs. (1) Low temperature tire cross section. This layer pected to endure before pitting or fracture occurs. cal property uniformity. stock size and type of mechanical working.structure for machinability and mechani- important consideration for gear wear. at a given stress containing decarburization.1. which is used in or normalizing heat treatment. Tensile strength predicts fied material grade. (1) Mechanical Properties NOTE: Gear toughness is adversely af- (2) Grade and Heat Treatment fected by design or manufacturing consider- (3) Cleanliness ations (such as notches. Although not directly considered pering (refer to 5.6 Heat Treatment. normalizing (or impact strength. section size and heat treat impact or low temperature applications or both. surface conditions sized sample(often a bar) used generally for surface and residual stresses. toughness may be important for high dent upon hardenability. and the relative importance of each can (7) Absence of alloying elements such as vary. nonmetallic inclusions. Material Selection Guidelines residual elements (5) Nonmetallic inclusions Many factors influence the selection of materials (6) Large grain size for gears. These include: annealing. 4. and other surface imperfections. 4.5 Toughness. hardening treatments. with regard to composition and the stress level above which fracture occurs.1 Mechanical Properties. 4. I---H. F---H.Wrought Steel Common Alloy Common Heat 1 General Remarks/Application Steel Grades Treat Practice 1045 T---H. T---H&N Special Heat Treatment Nitralloy G T---H&N Special Heat Treatment 4150 I---H. I---H. Excellent Hardenability in Heavy Sections 1020 C---H Very Low Hardenability 4118 C---H Fair Core Hardenability 4620 C---H Good Case Hardenability 8620 C---H Fair Core Hardenability 4320 C---H Good Core Hardenability 8822 C---H Good Core Hardenability in Heavy Sections 3310 @ C---H Excellent Hardenability (in Heavy 4820 C---H Sections) for all three grades 9310 C---H 1 C---H = Carburize Harden F---H = Flame Harden I---H = Induction Harden T---H = Through Harden T---H&N = Through Harden then nitride 2 Recognized. I---H. such as quench and temper or case hardening. F---H.2 Grade and Heat Treatment. The specific gear Tables 4---1. T---H. T---H&N. 4---2. and 4---3 for grades and recom- design will usually dictate the grade of material re. mended heat treatments. TH&N Quench Crack Sensitive Good Hardenability 4142 I---H. T---H&N. T---H&N. but not current standard grade. F---H Low Hardenability 4130 T---H Marginal Hardenability 4140 T---H. F---H Medium Hardenability 8640 T---H. T---H&N Used when 4140 exhibits Marginal Hardenability 4350 @ T---H. I---H. and materials handbooks. See 4. Gear Materials and Heat Treatment Manual stock removal tables can be found in most machining quired as a function of subsequent heat treatment. Table 4---1 Typical Gear Materials --. F---H Fair Hardenability 4145 T---H. F---H Quench Crack Sensitive. T---H&N. ANSI/AGMA 6 2004---B89 . F---H Good Hardenability in Heavy Sections Nitralloy 135 Mod. F---H Medium Hardenability 4340 T---H. I---H. I---H. 4. ations such as: added stock. improved properties for other than critical gearing ert atmosphere (argon) shielded and bottom poured applications. 3.015 percent. etc. but machinability may be reduced. Improved A534 and A535. sible cracking (see 5. etc. Hardness and strengths able to be obtained by normalize and tempering are also a function of controlling section size and tempering temperature considerations. Normalized and Tempered Steel Gearing Annealed Heat Treatment @ Normalized & Tempered # Typical Brinell Tensile Yield Brinell Tensile Yield Alloy Steels 1 Hardness Strength Strength Hardness Strength Strength Specified Range min min Range min min HB ksi (MPa) ksi (MPa) HB ksi (MPa) ksi (MPa) 1045 159---201 80 50 159---201 80 50 (550) (345) (550) (345) 4130 156---197 80 50 167---212 90 60 8630 (550) (345) (620) (415) 4140 4142 187---229 95 60 262---302 130 85 8640 (655) (415) (895) (585) 4145 197---241 100 60 285---331 140 90 4150 (690) (415) (965) (620) 4340 212---255 110 65 302---341 150 95 4350 Type (760) (450) (1035) (655) 1. factors such as standard industry alloys and procure- ty steel for critical gearing applications. to improve cleanliness and reduce objectionable gas NOTE: For more information see ASTM content (hydrogen. selection is often determined by cost and availability proved fatigue strength to produce the highest quali. 2. however.3 Cleanliness. increase in cost and reduced machinability. impact. restricted Vacuum degassed steel may be further refined by hardenability. in. oxygen and nitrogen).. for ex. The process to achieve strength. Significant ment time. die steps. to minimize distortion and pos- vacuum arc remelting (VAR) or electroslag remelt. cleanliness (reduced nonmetallic inclusion content) results in improved transverse ductility and impact 4. ing (ESR) of the steel. 4. with sulfur content less than 0. ANSI/AGMA 7 2004---B89 .5 Cost and Availability. See Table 4---3 for quench and tempered gearing. Alloy steel manufactured with elec. i. The specific material ther reduce gas and inclusion size and content for im. Gear Materials and Heat Treatment Manual Table 4---2 Typical Brinell Hardness Ranges and Strengths for Annealed. Steels shown in order of increased hardenability.4 Dimensional Stability. the blueprint design may require material consider- ample. and AMS 2301 and 2300.e. tric furnace practice for barstock and forged steel must be fully evaluated with respect to the need for gear applications is commonly vacuum degassed. These refining processes fur. ductility. Hardening by quench and tempering results in a combination of properties generally superior to that achieved by anneal or normalize and temper.8). engineering drawings should allow optional materi. 4320. such as 1020. determined by the Jominy End Quench Test (ASTM When specifying parts with small quantity re. A255) or can be predicted by the Ideal Diameter quirements. which is largely deter- “mill quantities” (several thousand pounds) and long mined by the alloy content of the steel grade. ture.1 Determination. (4340 and 4350 provide advantage due to higher tempering temperatures and microstructure considerations) w High specified hardness is used for special gearing. SAE and ASTM designations should first normalized then uniformily heated to a standard be used wherever possible. but costs should be evaluated due to reduced machinability. Gear Materials and Heat Treatment Manual Table 4---3 Typical Brinell Hardness Ranges and Strengths for Quenched and Tempered Alloy Steel Gearing Alloy Hardness Tensile Yield Steel * Strength Strength Heat Treatment Range minimum minimum Grade HB [ ksi (MPa) ksi (MPa) 4130 Water 212---248 100 (690) 75 (515) Quench & up to 8630 Temper 302---341 145 (1000) 125 (860) 4140 Oil 241---285] 120 (830) 95 (655) 8640 Quench & up to Temper 341---388 4142 4145 341---388 170 (1170) 150 (1035) 4150 4340 Oil 277---321 135 (930) 110 (760) Quench & up to 4350 Temper 363---415w 180 (1240) 145 (1000) * Steels shown in order of increased hardenability. Hardenability of steel is the prop. Service centers can usually furnish these mate.6. The depth to which a particular hard- rials in small quantities and with short delivery time ness is achieved with a given quenching condition is a from their inventories. 4820. ] It is difficult to cut teeth in 4100 Series steels above 341 HB and 4300 Series steels above 375 HB.1. standard alloys should be specified or (DI) concept. delivery time. The standard wrought carbon and alloy steels by quenching from the austenitizing temperature. and non---standard steels can 4. In the case of steel and iron castings and nonfer.6 Hardenability. ANSI/AGMA 8 2004---B89 . The bar is placed in a fix- 4. 4350 being the highest. the mill quantity cost may be substantially lower.1 Jominy Test Method. 8620. Steel mill purchases require function of the hardenability. 9310. austenitizing temperature. 4150 and The as quenched surface hardness is dependent pri- 4340 are available from service centers and steel marily on the carbon content of the steel part and mills. Hardenability is normally be supplied on special request. [ Hardness range is dependent upon controlling section size (refer to appendix B) and quench severity. However. four inches (102 mm) in length is rous materials. 4140. A one inch (25 als. cooling rate. then quenched by spraying room temperature erty that determines the hardness gradient produced water against one end face. 4. These steels can be ordered to “H” Band hardenability ranges. mm) diameter bar.6. The mechanics of the cutting operation intervals. or restricted H---Band.6. Bands are published by ASTM. Metallic oxides from the water quenched end. Gear Materials and Heat Treatment Manual 4. quenched end face. Fac. chinability of materials and in turn affect the econo. part size. and other hardenabil- ity reference publications. Several factors influence the ma. cast steel hardenability must be increased in order to iron and ductile irons. and are available in a wide range of rigidity. Rockwell C hardness (4) Characteristics of the cutting fluid used. selenium. practices. the hardness obtained at any location on a part will depend on car.6. Forgings reduce ma- (3) Condition of machine tools. including chining time. hardenability.4 Ideal Critical Diameter. 4. and economic considerations. a fair rating would add 20 to 30 percent to the above the specified hardness so that toughness and machining cost. power.2 Jominy Analysis. the include carbon and alloy wrought and cast steels. SAE. fair.8. With good machinability as a characteristic that will yield an as quenched hardness base. stock. stock depending upon service. These factors forms include wrought steel. hardness.2 Application. These irregular inclusions and can also benefit machining. since of 40 HRC at a distance of 5/16 inch (8 mm) they affect properties and structures. when high strength levels are being specified. quantity. Therefore. sizes and grades.3 H--. when used in high stress gear cal Diameter Method (DI) is based on chemical anal- and shaft applications. The standard wrought steel forms are round (2) Cutting speeds. De- 4. These my and feasibility of manufacturing. size. availability. may significantly reduce fa- ysis described in AISI. Carbon content over 0. AISI. etc. ANSI/AGMA 9 2004---B89 .8 Ferrous Gearing. Elements such been applied to standard steels. particularly castings. Chemical composition and microstructure of Example: J5 = 40 is interpreted as a hardness steel have major influences on machinability. machinability can be attained through appropriate 4. precision. specifications. Only metallurgical fac- obtained at each interval starting at the water tors will be discussed. shape. Typically a listed in Table 4---4 on the basis of good. design. alloys vary with the cooling rate. and tellurium form soft in- tion the Jominy hardenability data falls within a pre- clusions in the steel matrix and can benefit machin- dicted range. and poor would add 40 to 50 percent. higher manga- a given steel composition. Calcium additions (in steel making) form hard.1. Ferrous materials for gearing tempering. particularly in the transverse direction. The more common gear materials are quench media.7 Machinability. chinability. For a given composi. lead.Band Steel. feeds and cutting tools. and steel composition is selected with a hardenability poor machinability. configuration. sulfur. Steels purchased to predicted harden- ing. As the section thickness increases. Wrought steel is the gener- tors influencing machinability are: ic term applied to carbon and alloy steels which are (1) Material being cut.6 mm) chinability.1 Wrought Steel.30 percent de- creases machinability due to increased hardness. flat stock and forgings. as sulfur. and SAE.1. Jominy hardenability is expressed in HRC will not be considered here. and quenching conditions. The Ideal Criti- Calcium treated steel. In general. hardness will nese also decreases machinability. however. tions.1. ability ranges are called H---Band steels. mechanically worked into form for specific applica- microstructure. Hardenability is constant for pendent on carbon and sulfur levels. Modern Steels and Their tigue life compared to conventional steelmaking Properties by Bethlehem Steel.6. lead and calcium inclusions which Steels can be purchased to H---Band. However. which increase hardness and toughness decrease ma- bon content. like alumina and silica form hard oxide inclusions 4. weld fabrications and must be considered at the design stage. Jominy hardenability has and contribute to poor machinability. Gearing of alloy and carbon maintain a given hardness in the part section. and size. steel is manufactured from different forms of rough 4. improve machinability can decrease mechanical properties. 4. including composition. measurements are made along the length of the bar There is abundant material published on ma- on ground flats in one sixteenth of an inch (1.6. machinability may decrease appreciably. The economics of the pretreatments must be considered. as rolled. Inadequate (slack) quench can seriously affect machinability in these steels. annealed or 4320 quenched and tempered. However. and distortion during heat treatment is reduced. Increasingly cleaner steels are now also being specified for gearing. Inadequate cooling during normalizing can result in gummy 8620 material. as rolled. reduced tool life and poor surface finish. 4118 Good machinability. Gear Bronzes All gear bronzes and brass have good machinability. Austenitic All austenitic stainless steel grades only have fair machinability. normalized is 4620 preferred. machinability is fair. gear steels are generally used in the fine grain condition since mechanical properties are improved. ANSI/AGMA 10 2004---B89 . Above 363 HB. if sulfur content is low.Remarks 1020 Good machinability. However. Sulfur additions aid the 4340 machinability of these grades. 4345. Gear Materials and Heat Treatment Manual Table 4---4 Machinability of Common Gear Materials Material Grades Low--. NOTE: Coarse grain steels are more machinable than fine grain. the 4150 higher carbon results in lower machinability. Quench and temper 8822 as a prior treatment can aid machinability. less than 0. or normalized. The very high and Brasses strength heat treated bronzes [above 110 ksi (760 MPa) tensile strength] have fair machinability. 1141 1541 4130 Good machinability if annealed. Quenched and tempered ductile iron has good machinability up to 285 HB and fair machinability up to 352 HB. Ductile Irons Annealed or normalized ductile cast iron has good machinability. but produces a mixed microstructure which results in poor machinability.Carbon Carburizing Steel Grades --.Remarks 1045 Good machinability if normalized. Material Grades Other Gear Material --. 4150. Higher strength gray cast irons [above 50 ksi (345 MPa) tensile strength] have reduced machinability. 4145 Remarks for medium carbon alloy steel (above) apply. Over 321 HB. machinability is poor. However. as forged. Normalizing without tempering results in 4820 reduced machinability. The higher carbon level in 4145. and 4350 makes 4350 them more difficult to machine and should be specified only for heavy sections. or as forged. Because Stainless Steel of work hardening tendencies. Above 352 HB. However. machinability is poor. The “as cast” (not heat treated) ductile iron has fair machinability. or normalized and tempered to 4140 approximately 255 HB or quenched and tempered to approximately 4142 321 HB. 9310 Material Grades Medium Carbon Through Hardened Steel Grades --.Remarks Gray Irons Gray cast irons have good machinability. 4340 machinability is good up to 363 4345 HB. feeds and speeds must be selected to minimize work hardening.015 percent. Inadequate (slack) quench with subsequent low tempering temperature may produce a part which meets the specified hardness. 3310 Fair to good machinability if normalized and tempered. 001 (76. ANSI/AGMA 11 2004---B89 .500 (89) 3. but show no improvement in ing applications. Stress Relieved Steel Bars (Special Cold Drawn. are manufactured to a size larger than can be formed chased in various diameters for standard carbon and with rolling dies or rolls.001 (76. depending upon steel mill ca- may be subsequently annealed. Forged round bars are forged round Hot Rolled: 8. They are typically available as hot purchased in a variety of heat treat conditions de- rolled. Additional requirements: Hardness. min HRCw 1137 SR * 95 (655) 90 (620) 11 24 1045 SR 115 (795) 100 (690) 10 24 0.5 in (64 mm). Hot rolled bars are mechanically worked at Approximate maximum diameter of the various approximately 2100---2400_F (1150---1315_C) and types of round stock.000 (102) 1144 SR 105 (725) 90 (620) 9 24 * Stress Relieved. w Typical value. Rockwell C 30. ] Special steel. ished and forged rounds. 4145 SS not available above 3. ground and/or polished) for produce densification and quality bar for many gear- improved size control.1) 1045 SR 105 (725) 90 (620) 9 24 to 1141 SR 105 (725) 90 (620) 9 24 4. continuous cast steel bar manufactured with continu- erties (higher hardness and yield strength). High Tensile) Size Mechanical Properties for Rounds.1 Round Stock.000 (76) 1144 SS[ 140 (965) 125 (860) 10 w 30 4145 SS] 150 (1035) 130 (895) 10 w 32 3. [ Special steel.0 inch (100 mm) temperature as hot rolled bars (higher temperature Cold Finished: 5.Cold Drawn.8.1. Additional requirements: Hardness Rockwell C 32. is as follows: stress relieved. min.375 (10) 1141 SR 115 (795) 100 (690) 11 24 to 1144 SR 115 (795) 100 (690) 10 24 3. hot rolled---cold fin. Hot rolled---cold finished bars area (7 to 1 minimum) during hot deformation to are machined (turned. not a requirement. straightened and pacity. NOTE: Some cold finish steel companies furnish many of the above steels under various trade names. pending upon application. Cold drawing produces a Hot rolled bars are also now manufactured from close tolerance bar with improved mechanical prop. Continuous cast bar is subsequently hot medium carbon steels are normally available as cold rolled with sufficient reduction in cross sectional drawn bar for gearing. Squares and Hexagons included Steel Minimum Minimum Designation Elongation in Nominal inch (mm) Tensile Strength Yield Strength 2 inches (50 mm) Hardness ksi (MPa) ksi (MPa) percent. Forged round bars can be alloy grades.0 inch (205 mm) under a press or hammer at the same approximate Cold Drawn: 4. hot rolled---cold drawn. Round bars can be pur.1) to 4145 SS] 150 (1035) 130 (895) 10 w 32 3. 1144 SS not available above 2. Gear Materials and Heat Treatment Manual 4. min. mechanical properties over hot rolled or annealed bar. Low to ous casters.0 inch (405 mm) Table 4---5 Mechanical Property Requirements --.0 inch (125 mm) for lower carbon content carbon or alloy steel) and Forged Round: 16.5 in (89 mm). Gear Materials and Heat Treatment Manual 4. Commercial flat or plate (3) Rolled Ring Forging. can result in improved transverse ate preheat and postheat temperatures. generally smaller than an for gear assembly and mounting purposes. (510---675_C) depending upon the previous temper- sures due to dissolved gases during the forging pro. ref- deformation is done while the billet is at tempera. (254 mm) outside diameter with a 2. manufactured by electric furnace specified hardness (mechanical properties) prior to practice using part or all of the cleanliness techniques weld assembly. The rim or tooth section is heat treated to obtain Alloy steel. Forgings are made by hot me. Typically. Weld fabricated gears are produced.2 Weld Fabrications. This method produces steel of numerous carbon and alloy grades is avail. to split ring gears about Open die forgings may be specified to be upset 480 inch (12 192 mm) outside diameter with a 40 inch forged to increase center densification. much like steel castings 4. An upset (1016 mm) face. and then is rotated 90 de. are now also bottom poured as well as conven.8. ASTM A290 should be refer- enced for ring forgings for fabricated gears. erence should be made to the following sources: tures generally above 1900_F(1038_C). Still which develop high centrifugal stress at the center. action deforms the metal to fill the die cavity. a donut---shaped work piece. split hub.3 Cast Steels. This method produces a are used for a wide variety of through hardened gear- rough dimensioned piece by mechanical deforma. ing and. 4. larger ring gears are solid or split ring design with bolt (2) Closed Die Forging. electric arc.3 Forgings. Cast steel is manufactured ducing a more exact contoured forging. After weld assembly. tween the mandrel and the press anvil. from which blooms and billets are manufactured prior to forming forgings and bar. greater than sign. Larger gears are grees and hot worked again. This method produces a holes at the splits and on the inside diameter flange closer toleranced piece. with possible cored holes in the worked in one direction. The size of cast gearing varies from 10. by the open hearth. Smaller gears generally have a solid forging is produced when the billet is initially hot web and hub design. web or flange for weight reduction. which incorporate cast arms rather than the 30. Bottom poured ingots are poured Forging Industry Handbook. Flat stock is typically available in hot drel and shaping the ring by a hammer action be- rolled or hot rolled and annealed conditions.8. for case hardened applica- tion between an upper and lower die (hammer and tions. Split gears open die forging. Typically the process in- able in standard thicknesses in a wide range of widths volves piercing a pancake---shaped billet with a man- and lengths.000 feet/minute (152 m/sec) pitch line velocity. Bottom poured ingots show improved generally consist of rolled or forged rings. plate or castings for the rim (tooth) section.2 Flat or Plate.0 inch (51 mm) face width for solid rim gears. Large diame- 4. Typical cast gear de- steel billet in a closed (confined) cavity and the press signs are shown in Fig 4---1.1 Manufacture.8.1.0 inch anvil) in an open frame press or hammer.1.3.3. American Iron and Steel Institute (AISI). heavier solid web design used for smaller gears. Carbon and alloy steel castings (1) Open Die Forging. specific form) which densifies the structure. Metal Handbooks Cast ingots. and may For additional information on wrought steel provide improved inclusion orientation. Products Manual tional top poured. or induction furnace ANSI/AGMA 12 2004---B89 . ing temperature used to obtain the specified hard- cess. ter rings are rolled on a roller press from circular bil- chanical deformation (working of a steel billet into a lets containing a central hole. to a lesser degree. pro. dustry Association ten steel to the ingot mold. Steel stock. ness of the rim section. The upper and lower dies trap the are cast in two or four segments.8. using appropri- discussed in 4. Upset forgings are often usually solid hub. a forged got metal after conventional cropping or removal of or cast hub and mild steel plate for the web or arm the top pipe cavity and bottom discard of top poured support sections. ingots). manufacture and steel making refining practices.8. or split hub and rim de- used for critical high speed gearing. welded as- ductility and impact strength. by the Forging In- with a bottom ingate and runner which provides mol. The standard forging classifications are: 4. Forging stock is always semblies are furnace stress relieved at 950---1250_F fully killed steel to minimize the occurrence of fis. formed macro---cleanliness and ingot yield (more usable in. American Society for Metals (ASM Internation- al). care cesses can be used for reducing the gas.3.8. Secondary refining pro.2 Material Grades of Cast Steel. ifications (silicon. nace steel making practices. 8630. and 4340 4---6 and 4---7. 4135. respectively. sis for through hardened gearing has sufficient 4.) Fig 4---1 Typical Design of Cast Steel Gears ANSI/AGMA 13 2004---B89 . hardenability to obtain the specified minimum hard- terial grades used for cast gearing are generally mod. 4140. phosphorus. 8640. etc) of standard AISI or SAE des. Gear Materials and Heat Treatment Manual melting processes. must be taken to ensure that the specified cast analy- and sulfur levels of cast steel. type steels. SOLID WEB CORED WEB SMALLER GEARS SOLID RING SPLIT RING SOLID HUB SPLIT HUB SPLIT HUB AND RING LARGER GEARS INCLUDING OPEN GEARING (NOTE: Each design above can be made by forging or weld fabrication. The ma. Through hardened gearing applications of through hardened cast steels are shown in Tables generally use 1045. 8620 and 4320 types. using both acid or basic lined fur. Typical chemical analyses and tensile properties ignations. ness. As with wrought steel. Carburizing grades are usually 1020. 80---1. 2.00 0.60 0. Vanadium content of 0.0 26.43 Manganese 0.040 0.--.45 0. depending upon specified hardness (mechanical properties).0 18.040 Silicon.60---1.30 GENERAL NOTES: 1.30---0. type of heat treatment and controlling section size (hardenability) considerations. When basic steel making practice.0 F 321---363 145 (1000) 120 (830) 8.00 Phosphorus. 0.37---0.030 0.60 0.0 G 331---375 150 (1030) 125 (860) 7.70---1. 0.60---0.00 Chromium --.0 28.60---0.38---0. 6. Part 1 Materials. Table 4---7 Tensile Properties of Through Hardened Cast Steel Gears! Minimum Percent Percent AGMA@ Brinell Minimum Yield Minimum Minimum Hardness Tensile Strength Elongation Reduction 6033---A87 Strength Class Range 0.90 1.90 0. 0. 0.040 0.70---1.0 20. max.40---0. Source: AGMA 6033---A88.70---1.00 0.90 0.--.50 0. ANSI/AGMA 14 2004---B89 .60 Nickel --. max.27---0.0 24. 0.70---1.60 0.2 percent Offset in 2 in in Area ksi (MPa) ksi (MPa) (50 mm) A 223---269 100 (690) 75 (480) 15.050 0. ladle refining or AOD (argon oxygen decarburization) processing are used. Above tensile requirements for seven classes are modifications of three grades of ASTM A148 (Grades 105---85 through 150---135). 0.60 0.10 percent may be specified for grain refinement.70---0. --.15---0. max.00 0.60---0.50 0.030 0.38---0. Other AISI Type and proprietary chemical analyses are used for carbon and low alloy cast gears according to ASTM A148 or customer specifications.65---2.0 NOTES: 1. lower phosphorus and sulfur contents to less than 0. Gear Materials and Heat Treatment Manual Table 4---6 Typical Chemical Analyses for Through Hardened Cast Steel Gears Alloy Percent for Cast Steel Types Element 1045 Type 4140 Type 8630 Type 8642 Type 4340 Type Carbon 0.20---0.0 31.025 percent maximum may be specified for low alloy cast steel (per ASTM A356) for ladle deoxidation to improve toughness. Part 1 Materials.0 E 302---352 140 (970) 115 (790) 9. Standard for Marine Propulsion Gear Units.25 0.020 percent are commonly achieved.060 0.--.06---0.90 Molybdenum --.0 D 285---331 130 (900) 100 (690) 10.90 0.60---0.0 35. Source: AGMA 6033---A88.040 0.0 C 262---311 118 (810) 90 (620) 11.--. 5. cleanliness and machinability.40---0.00 0. 4. Aluminum content of 0.030 0.0 B 241---285 110 (760) 80 (550) 13. Type designations indicate non---conformance to exact AISI analysis requirements.030 Sulfur. 3.10 0.37 0. 2. Standard for Marine Propulsion Gear Units.40 0.43 0. ASTM E125---63 (1980).4. Volume 5. are heat treated to either a specified hardness or to Steel Founder’s Society of America (SFSA) Publica- specified hardness and minimum mechanical prop. Non- quired on both rim faces of gear castings is generally destructive Inspection and Quality Control based on the outside diameter. Repair Recommended ASTM specifications for nonde- welding of castings prior to heat treatment is rou.3 for additional information. 4140 and ASTM A609---83. Repair ASTM E186---80.8. if allowed after heat treatment. fect machining. close dimensional tolerances.8. cooled to below 600_F (315_C). Castings must meet the nondestructive test re. 8th edition. All welds should be inspected ASTM E446---81.8. Cast iron castings are gener- tions are routinely performed to meet specified sur.3. iron alloys.6 Additional Information for Cast Steel.1 Gray Iron. Reference Photographs ing locations should be performed only prior to heat for Magnetic Particle Indications on Ferrous Castings treatment. graphs for Heavy Walled [4 1/2 to 12 inch(114 to 305 favorable residual tensile stress or high hardness in mm)] Steel Castings the heat affected zone. and unfused chaplets in the rim sec. It is characterized by the gray color occurring ages.3. ANSI/AGMA 15 2004---B89 . (1) Material considerations. Standard Reference Radio- post heat are recommended to avoid or minimize un.3. (538---593_C). Other nondestructive Stress relieving may be deemed necessary to hold testing. gas on a fracture surface.2 and gories. The quality specified ity. shall be fol. and repair welding which could adversely af. Castings ASM Handbook series. Magnetic Particle Examination the rim (tooth) portion and other critical load bear. graphs for Heavy Walled [2 to 41/2 inch) (51 to 114 lowed by reheat treatment. require notification of the purchaser. gas holes. Dry or wet fluorescent magnetic particle inspec. (2) Heat Treating. Castings should be over 3. flakes. chills. Methods of testing. entrapped sand and hard areas in the in other than the rim (tooth) section is often less tooth portion. The (tensile and impact) are generally required only family of cast irons is classified by the following cate- when specified. such as radiograph and ultrasonic inspection. Standard Reference Radio- welding. and acceptance standards are estab. The number of tests 4. Mechanical property tests the family of high carbon. Thickness NOTE: Weld repair in the tooth portion may 4. 6. graphs for Steel Castings Up to 2 inch (51 mm) in ing. whenever possible. Volume 11. Minor discontinuities in finish machined Repair welds in areas to be machined should teeth. ally furnished as cast unless otherwise specified. if present. with the approval of the gear purchaser.3. Standard Reference Radio- to the same quality standard used to inspect the cast. Cast Iron is the generic term for increases with OD size. have machinability equivalent to the casting. Refer to Gray and Ductile Iron cutting. If re. Casting should also be free of cracks. Ultrasonic Examination of 4340 Types) should be used for repairing prior to Carbon and Low Alloy Steel Castings heat treatment in order to produce hardness equiva- lent to the base metal after heat treatment. are made by the electric arc furnace. hour per inch of maximum section and furnace lished between the purchaser and manufacturer. extraneous append. silicon. mm)] Steel Castings heat treatment is not possible. 4.8. localized preheat and ASTM E280---81. or in- tion. face quality requirements. ASM Handbook. scale. It is recommended is performed to evaluate internal integrity of the rim that castings be heated to 1000 to 1100_F (tooth) section when specified. stringent. in preference to cosmetic weld repair.4 Cast Iron.5 Quality of Cast Steel. cupola.8.0 percent) carbon. Cast irons for gears hot tears. Ap. 8th edition. Reference should be made to 6. structive inspection test procedures are: tinely performed by the casting producer. The minimum number of hardness tests re.3 Repair Welding of Cast Steel. which is present as graphite furnished free of sand.8. Castings Handbook for additional information. Gray iron contains (typically 4. and hard areas resulting from arc---airing. welds in the tooth portion should only be performed proval by the customer may be required. poros- quirements in the rim section. tion erties. Gear Materials and Heat Treatment Manual 4. duction practice and should be free of shrink. are often contour ground for re. Information is available in: 4.4 Heat Treatment of Cast Steel. Repairs in ASTM E709---80. holding at temperature up to one test locations. Repair moval. Heat treatable electrodes (4130. thickness of the tooth portion of the casting as fol.8) may be as agreed upon by the gear manufacturer and NOTE: See ASTM A48 for tolerances on as casting producer. and testing should be performed in accordance rosity.25 C (4) Mechanical Properties. the chemical analysis is left to the discretion of (6.51---1. Repair welds in areas to be machined should Tensile test coupons are cast in separate molds in have equivalent machinability as the casting. Hardness tests should be made in accordance 4.0) 1. 1 fied.) mensions for acceptance. in (mm) martensitic structures.4) (12. 2. Gear Materials and Heat Treatment Manual (3) Chemical Analysis. Other properties (25.00 1. (Refer to ness must be maintained to the finish machined di- Gray and Ductile Iron Handbook.5---50. ASTM A48 These heat treatments produce ferritic. is characterized by the the mid rim thickness or mid face width of the tooth spheroidal shape of the graphite in the metal matrix. Specified minimum hard- ments and subsequent heat treatments. Ductile iron.01---2 incl.20 0. Standard Specifications for Gray in the tooth portion. the chemical analysis is left to the discretion of ASTM Brinell Tensile Class Hardness Strength the casting supplier as necessary to produce castings Number ksi (MPa) to the specification. Cast iron gears are 30 180 30 (205) rated according to AGMA practice based on hard. 20 155 20 (140) (4) Mechanical Properties. po- 4---8. 35 205 35 (240) ness.50 A (3) Chemical Analysis.88 0. The welding in the tooth portion should only be per- size of the cast test coupon is dependent upon the formed with the approval of the gear purchaser. of Tooth Diameter. Hardness tests should be made on ferred to as nodular iron. gas holes and entrapped sand and hard areas with ASTM A48. (1) Material Considerations. (12. Tensile test coupons should be poured from the siderations if bar fails to meet requirements. Minimum Hardness and Tensile Strength Size of the Y---block mold. cast and machined diameter and retest con.4.2 Ductile Iron. 50 250 50 (345) 60 285 60 (415) Minimum hardness requirements for the classes of cast iron are shown in Table 4---8. A wide range of mechanical proper- should be made to verify that the part meets the mini- ties are produced through control of the alloying ele- mum hardness specified. At least one hardness test should produced by innoculation with magnesium and rare be made on each piece. portion diameter.8) (31.8---25. normalizing and temper- ing or quenching and tempering or as---cast as re- Thickness As Cast Machined quired to meet the specified mechanical properties. Typical mechanical properties are shown in Table 4---9. Test coupon mold design shall be in accordance with ASTM A536. hardness determines the rating of 40 220 40 (275) the gear. same ladle or heat and be given the same heat treat- Table 4---8 ments as the castings they represent.7) the casting supplier as necessary to produce castings 0. and sufficient hardness tests earth elements. Therefore. (2) Heat Treating. Diameter. 1 See ASTM A48 for additional information.8. ANSI/AGMA 16 2004---B89 . Repair accordance with the provisions of ASTM A48. Unless otherwise speci- fied. Unless otherwise speci. if used.7) (22.5) (19. Tensile test requirements are shown in Table induction practice and should be free of shrink. 0. sometimes re- with ASTM E10.25---0.50 0. cupola or fied. pearlitic or Section.4---12. in (mm) in (mm) Test Bar.8) (50. Iron Casting. Ductile iron castings shall be lows: heat treated by annealing. Ductile iron cast- Tensile tests should only be required when speci.00 1. ings are made by the electric arc furnace.4) (30.750 B to the specification. is at the option of Requirements the producer unless specified by the gear manufac- for Gray Cast Iron turer. The yield strength For solid cylindrical pieces. in(mm) Hardness Tests single furnace load. 1 od of Test for Brinell Hardness of Metallic Materials. in(mm) Hardness Tests dance with ASTM Designation E10. achieved. This treatment results in a unique away between risers. NOTE: Other tensile properties and hardnesses should be used only by agreement between gear manufacturer and casting producer. Over 3 (76) to 6 (152) incl. 2 Hardness tests should be made on the mid rim thick.4. with length over di- is normally determined by the 0. diameter of the casting as follows: When many small pieces are involved.0 100---70---03 A---7---d Quench & Tempered Pearlitic 241---302 100 (690) 70 (485) 3. When four hardness tests are microstructure of bainitic ferrite and larger amounts required. With variation in aus- one over a riser and the other approximately 180 de. such as automotive ring gears and pinions. refer to ASTM A536. made 90 degrees apart on both cope and drag side. For required retesting. a sample testing plan is generally used with the approval of the To 12 (305 ) 1 gear manufacturer. all poured Outside Diameter Number of from the same ladle or heat. but is still an emerging technology. and two tests on the drag several ranges of engineering properties can be side 90 degrees away from the tests on the cope side. To 3 (76) incl. Over 12 (305) to 36 (915) 2 Over 36 (915) to 60 (1525) 4 4.0 Ferritic---Pearlitic 80---55---06 A---7---c Normalized Ferritic---Pearlitic 187---255 80 (550) 55 (380) 6. of carbon stabilized austenite.0 Martensitic Specified 1 See ASTM A536 or SAE J434 for further information.8. if tensile bar fails to should be as follows: meet requirements.0 65---45---12 A---7---b As---Cast or Annealed 156---217 65 (450) 45 (310) 12. more costly forgings for certain applications. 60 (415) 40 (275) 18. they shall be with ASTM Designation E8. Gear Materials and Heat Treatment Manual Tensile tests should be performed in accordance When eight hardness tests are specified. Over 6 (152) 4 ness or mid face width of the tooth portion diameter. ADI permits low- ANSI/AGMA 17 2004---B89 . one irons.0 120---90---02 A---7---e Quench & Tempered Range 120 (830) 90 (620) 2. Tooth Portion. Table 4---9 Mechanical Properties of Ductile Iron 1 Elongation ASTM Former Recommended Brinell Min. the number of hardness tests method. ADI has been utilized in several significant ap. Diameter of Number of Hardness tests should be performed in accor. sion Testing of Metallic Materials. Yield Grade AGMA Strength Strength in 2 inch Heat Treatment Hardness Range (50 mm) Designation Class ksi (MPa) ksi (MPa) percent min 60---40---18 A---7---a Annealed Ferritic 170 max. er machining and heat treat cost and replacement of plications. NOTE: The hardness tests shall be spaced Number of hardness tests per piece is based on the uniformly around the circumference. tempering temperature and transformation time.2 percent offset ameter of one or more. Standard Method of Ten. and heat treated in a of Casting. Austemp- Over 60 (1525) 8 ered Ductile Iron (ADI) is a ductile iron with higher strength and hardness than conventional ductile When two hardness tests are required.3 Austempered Ductile Iron. Tensile Min. Standard Meth. grees away between risers. two tests should be made on the cope side. The higher properties of ADI are achieved by should be made on the cope side over a riser and the closely controlled chemistry and an austempering other on the drag side approximately 180 degrees heat treatment. e.5 Powder Metal (P/M). sity. Parts processed in this manner have strengths rate dimensional control over large production runs.0 the blind end. surement techniques.8. and The ductility of powder metal parts is substan.8 g/cm# will not develop a definite ASTM A220. lubricating part. Although this process is tain by other methods. Carburizing and the alloying practice and heat treatment. miter. al process. ratchets. Powder metal preforms are heated to forging tem- The powder metal process is used to reduce cost perature and finished forged to final shape and den- by eliminating machining operations. ing on density and alloy selected. However. This has carbonitriding can be performed. permits their impregnation with oil to provide a self plications. and other particle hardness and porosity. especially for the internal type of “As sintered” alloy steels have a tensile strength gears. and ease of ejection of the preform from the die cav- ther HRB or HRC) is a combination of the powder ity before sintering. cy over long runs. (3) Powder metal gears can be made with blind i. (2) Retention of some porosity contributes to Density is the most significant characteristic of quietly running gears and allows for self---lubrica- powder metal materials. Although several powder metal materials are The controlled porosity in powder metal parts available. to metallurgically bond the powder particles.8. depend. but treated white (chilled) iron which can be produced must be processed in a controlled atmosphere to pre- with a range of mechanical properties depending on vent changes in surface chemistry. Salt baths and cavity and heating (sintering) the resultant compact water quench systems should be avoided. Gear Materials and Heat Treatment Manual Test programs are currently underway which will rately determined using special microhardness mea- more clearly define operational properties of ADI. but products with a generally been replaced by ductile iron. however. but are formed by compressing metal powders in a die parts will achieve a file hard surface. assorted components. mechanical properties are proportional to density. high production quantities are usually nec. alloy steel is usually specified for gear ap.0 percent or less and an apparent hardness production of gears for several reasons: of HRB 60---85. tion. range of 40---80 ksi (275---550 MPa). Penetration hardness 4. True involute apparent hardness reading and can be more accu. possible in powder of the powder metal material will be higher than the metal with sufficient development.. with an elonga. and mechanical properties approaching the proper- and obtain characteristics and shapes difficult to ob. The actual hardness special gear forms are.4 Malleable Iron. tially lower than for wrought steels.4 g/cm# can be achieved using secondary opera- tions.4. helical. (4) Powder metal gears can be combined with other parts such as cams. Heat treated powder metal alloys have tensile strengths of 100 to 170 ksi (690---1170 (1) Carbide dies provide consistent part accura- MPa) with elongations of 1.) case due to the ease of diffusion through the more porous lower density material. other gears. Powder metal parts testing cannot be correlated to material strength. thus eliminating undercut relief that is need- levels. Sec- ondary operations such as repressing or sizing may be Further improvements in strength can be used to obtain precise control of shape and size or to achieved by the use of hot forming powder metal. higher strengths are achieved at higher density corners. it can still be cost effective for high pro- essary to realize savings. powder metal processes have ed with cut gears. The powder metal process is well---suited to the tion of 4. (Refer to density under 6. duction parts requiring higher mechanical properties than achievable using the standard process. Malleable iron is a heat Parts can be heat treated after sintering. ties of wrought materials. 4. Bevel. For a given composition. improve mechanical properties. gears are less difficult and may be less costly to pro- ANSI/AGMA 18 2004---B89 . Hardness specifi- Spur gears are the easiest to produce out of pow- cations can be developed for powder metal parts. In recent years.0 percent or less. to 7. provide accu. because of molding much more costly than the conventional powder met- die costs. and have extra support strength at improved to the point where a typical density of 7. but must be specified as “apparent hardness” since the der metal because of the vertical action of the press hardness value obtained using a standard tester (ei. die costs. Critical application gearing.9 Selection Criteria for Wrought. or rolled rings. achieve mechanical properties through alloying tionality of properties). but not equal. (2) Manganese Bronzes. meaning that the mechanical properties (tensile duc. ladle refined. aluminum. less frequently. Gear rims are normally forged gears. They have good wear resistance but do not possess trolled steel making. down time costs and safety con- tion of inclusions for gearing. Hardenability of the gear rim steel must be ade- pitation hardening stainless steels. Gear rims used in the an- cated Steel Gearing. mainly because of their “wear resistance” character- ing forming (see Fig 4---2). worked. be stress relieved at 950_F(510_C) minimum [50_F(28_C) below the 4. 4. gearing. further refined at premium cost by vacuum arc re- melt (VAR) or electroslag remelt (ESR) processing. Non---ferrous gears are These and other more economical refining processes made from alloys of copper. Improved steel cleanli. barstock. therefore. severe wear applications. etc. This alloy is the basic gear NOTES: Mechanical properties in the trans. and zinc. Casting quality involves con. Al- (AOD. They are measured in the longitudinal direction. when sound in the rim tooth without heat treatment. ations must justify the increased development and monly manufactured of vacuum degassed alloy steel. and ultrasonic or radiograph) practices. istics for withstanding a high sliding velocity with a ness has the effect of improving the transverse and steel worm gear. with quality becoming increasingly impor- to the profile of teeth. alloy and is commonly designated as SAE C90700 verse direction will vary with inclusion type (obsolete SAE 65) and is referred to as tin bronze. the longitudinal properties.1 Gear Bronzes. etc. to the direction of hot working or inclusion flow dur. This is the name given Mechanical property data is normally to a family of high strength yellow brasses. tangential properties of forged steel in order to ap. Wrought steel is anisotropic. These bronzes have the section. rolled sess excellent rubbing characteristics and wear resis- rings and plate are perpendicular to the root radius tance which permits use in gears and worm wheels for or profile of machined gear teeth. austenitic. or Fabri. tempering temperature]. These include hot work tool steel (H series). They pos- Inclusions in wrought steel forgings. sembly should. In addition to Fabricated (welded) gears are generally materials used for gears which are described in this manufactured when they are more economical than Manual there are other ferrous materials used for forged or cast gears. Gear Materials and Heat Treatment Manual duce in sufficient quantities than by other methods and non---destructive inspection (magnetic particle because tooth configuration is not a limitation. 4. high speed steels. molding. can provide comparable mechanical proper. however.6 Other Ferrous Materials. (1) Phosphor or Tin Bronzes. The welded as- high strength requirements. 4.10. ties to those of forgings. Cast. Most of these are used in worm gearing where the reduced coefficient of friction between Wrought or forged steel is generally considered dissimilar materials and increased malleability are more sound than castings because the steel is hot desired. nealed condition can be stress relieved at 1250_F (675_C). and material form. A family of four bronzes tility and fatigue and impact strength) vary according accounts for most of the nonferrous gear materials. cast. casting. characterized by high strength and hardness and are the toughest materials in the bronze family. heat treating the same degree of corrosion resistance. because quantities or critical application consider- such as for aerospace and special high speed.10 Copper Base Gearing. Selection of the gear blank producing method Forged or hot rolled die generated gear teeth. or. for most applications is primarily a matter of eco- with the direction of inclusion (metal) flow parallel nomics. They Castings generally being isotropic (non---direc. These bronzes are proach. same strength and ductility as annealed cast steel. wearability ANSI/AGMA 19 2004---B89 .8. Application is limited siderations increase.) improve cleanliness and loys of copper are in wide use for power transmission produce higher quality steel. formed alloy plate. result in the optimum direc- tant as tooth loads. tough and have good corrosion resistance. martensitic and preci. Special gear quate to enable a 1000_F (540_C) minimum temper- analyses are frequently used in applications with very ing temperature to obtain hardness. is com. but are inferior to the phosphor bronzes. Silicon bronzes are com- ness. low brass. characteristics are better than for manganese bronze (3) Aluminum Bronze. Wear resistance of these brasses is somewhat lower tant properties.10. ductility is properties. used because of its good machinability. As the plications because of their low cost and nonmagnetic strength of aluminum bronze is increased. (4) Silicon Bronzes. Aluminum bronze mate. Gear Materials and Heat Treatment Manual or bearing quality as phosphor and aluminum has low coefficient of friction against steel. rials are similar to the manganese bronzes in tough. er strength. monly used in lightly loaded gearing for electrical ap- chanical properties through heat treatment.2 Gear Brasses and Other Copper Alloys. This bronze has good wear resistance and DIRECTION OF METAL AND INCLUSION ROLLED FLOW RING FORGING TRANSVERSE LONGITUDINAL TENSILE TENSILE TEST BAR TEST BAR OR PROPERTIES DIRECTION OF METAL AND INCLUSION FLOW TRANSVERSE TENSILE TEST BAR LONGITUDINAL TANGENTIAL PINION FORGING TENSILE TEST BAR TENSILE TEST BAR NOTE: ASTM E399 may be used if impact testing is required. Bearing bronzes. but are lighter in weight and attain higher me. reduced. The most common gear brass is yel. Other brass materials are used because of their high- ANSI/AGMA 20 2004---B89 . but they are more difficult to machine. Gear brasses are selected for their corrosion resis. than for the higher strength manganese bronzes. Fig 4---2 Directionality of Forging Properties 4. 10. ASTM Designation E54. heat treating. (4) Casting Hardness. Additional information regarding manufactur- cified are made in accordance with ASTM E8. while analysis for chemistry. 4. gas holes and entrapped sand in the tooth portion. mechanical properties. group of gear materials includes bronzes. may be performed by the casting supplier. including phosphor Hardness tests are to be made on the tooth por- or tin bronze. hardness and hardness control. dard Methods of Chemical Analysis of Special Brasses and Bronzes. mon cast copper bronze alloys. Copper base castings are specified by melting method.4 Cast Copper Base. Tensile test bars for ties. chemical analysis. In the event of disagreement Table 4---11 presents typical mechanical properties of in chemical analysis. leaded tin bronze (improved machin. Tensile tests are 4. mally made in accordance with ASTM E10.4. Mechanical properties of sepa. Repair welds in the tooth area should be performed only Three test coupons shall be poured from each with the approval of the gear manufacturer. Specifications de. Tensile tests when spe- ings. obtained in the casting. Tensile test bars for centrifugal castings materials may be melted by any commercially recog. tensile proper- sion Testing of Metallic Materials. Stan- these wrought bronze alloys in rod and bar form.3 Wrought Copper Base.10. load in kilograms force listed in Table 4---13 should be Refer to Table 4---12 for chemical analyses of com. rate cast test specimens are shown in Table 4---13. may be used as the referee method. Table 4---10 presents chemi. Hardness tests are nor- analysis or type.10. ANSI/AGMA 21 2004---B89 . used. The properties in the casting are dependent upon the size and de- Repair welding in other than the tooth portion sign of the casting and foundry practice.1 Cast Worm Bronzes. Chemical analy. of Test for Brinell Hardness of Metallic Materials. Wrought copper as agreed to by the gear manufacturer and casting base materials is a general term used to describe a producer.10. Gear Materials and Heat Treatment Manual 4. ability) and higher strength manganese bronze and The number of hardness tests made should be speci- aluminum bronze. tion of the part after final heat treatment. Method 4. Copper Base castings where the individual casting weighs more than 1000 are heat treated as required to obtain the specified lbs (454 kg). heat treatment. (5) Casting Tensile Properties.4. porosity. Ten- ing. brasses. may be cast in a separate centrifugal mold for test nized melting method for the composition involved. hardness and tensile properties. group of mechanically shaped gear materials in The chemical analysis shall be determined from which copper is the major chemical component. cast structure sand castings may be attached to casting or cast sepa- and supplementary data for cast copper alloys is as rately. Castings NOTE: An integral or separately cast test bar should also be furnished free of sand and extraneous does not necessarily represent the properties appendages. fied by the gear manufacturer. pons heat treated in the same furnace loads as the sis shall be in conformance with the type specified or casting they represent. The scribe type of bronzes according to chemical analysis.2 General Information for Copper Cast- only required when specified. and other copper alloys. Castings should be free of shrink. Heat treated castings should have the test cou- (3) Casting Chemical Analysis. melt of metal or per 1000 lbs (454 kg) of melt except (2) Casting Heat Treating. This a sample obtained during pouring of the heat. Cast copper base gear bar mold. Tensile test bars for static chill castings may be follows: cast separately with a chill in the bottom of the test (1) Casting Manufacture. The gear manufacturer may perform a product cal analyses of common wrought bronze alloys. bars or cast in a chill test bar mold. if required. --. Percent Maximum (unless shown as a range or minimum) Bronze Former Alloy 1 AGMA Cu Ni (incl Ag) Pb Fe Sn Zn Al As Mn Si (incl Co) UNS NO.0 --. see SAE Information Report SAE J461.--. 58.--. 2 Unified Numbering System. --.2 C67300 --. For cross reference to SAE.6 2. 90 (620) 45 (310) 25 180HB (1000kgf) C62400 --.0 to to 4.60 --. 0. Rem. Type ksi (MPa) ksi (MPa) percent. Table 4---11 Typical Mechanical Properties! of Wrought Bronze Alloy Rod and Bar Former Elongation in Bronze2 Alloy Tensile Strength Yield Strength Hardness AGMA 2 in (50 mm) UNS NO. Gear Materials and Heat Treatment Manual Table 4---10 Chemical Analyses of Wrought Bronze Alloys Composition. also see SAE J463. 1. former SAE & ASTM.50 0.--.0 C62400 --. Type C62300 --.--. see SAE Information Report SAE J461.0 11.0 0. 70 (485) 40 (275) 25 70 HRB 1 Typical mechanical properties vary with form.25 to to to to 63.50 0. temper.0 0.25 to to 7. and section size considerations. 10.0 to to to 4.5 0.25 --.20 0. 2.--.0 --. --.0 11. --.20 0. 2.30 0. 95 (655) 50 (345) 12 200HB (3000kgf) C63000 ALBR 6 90 (620) 45 (310) 17 100 HRB C64200 ALBR 5 93 (640) 60 (415) 26 90 HRB C67300 --.5 11. 2.5 1 Unified Numbering System.0 3. min. Rem.0 0.--.50 0.50 6.25 4.0 3.20 --. 0.30 9.25 --.--.10 1.50 0.25 1.30 Rem.--- to to 4.0 0.5 1.15 0. former SAE & ASTM.--.05 0. also see SAE J463.--.40 0. For added copper alloy information. 0. 8.5 --. For cross reference to SAE. 0.3 0.5 C63000 ALBR 6 Rem.0 5. HB and HRB C62300 --. 2.5 C64200 ALBR 5 Rem.--.--. ANSI/AGMA 22 2004---B89 .--.0 0.--.--.30 0. For added wrought copper alloy information. --.25 0.5 C95500 ALBR 4 78.--.20 0.--. --.0 9.0 0.--.0 42.--.5 --.0 --.0 --.0 4.20 0. 3.0 --.005 0.5 percent maximum.5 min to to to 5.--.0 --.0 0.--.20 0. For cross reference to SAE.005 0.--.5 min to to 5. --. 1.5 --.8 0.05 0.005 0.0 12. --. --. 0.005 0.--- min to to 1.005 --.10 to to to to to 60. 1.0 --. Gear Materials and Heat Treatment Manual Table 4---12 Chemical Analyses of Cast Bronze Alloys Bronze Former Composition. --. 0.2 4. --. --.5 C95300 ALBR 2 86. 3.0 --.0 1. { For continuous castings.0 7.005 --.8 --. 0. 1.0 1.--.5 1. 10. --.--.0 11.--- min to to 4.5 to to to to to 66.0 10.0 0. 82.0 C86300 MNBR 4 60.0 --.0 2. 0.0 --.--.5 C92700 MNBR 3 86.005 --.0 9.5 0. --. also see SAE J462.--.0 C95200 ALBR 1 86.5 11.--.0 2.--. --.8 0.25 1.0 2.50 0.0 --.0 --.30{ 0.5 11.--.0 0.20 22.--.50{ 8. ANSI/AGMA 23 2004---B89 .--.0 0.0 C86500 MNBR 2 55. 3.--.--. --.0 --.30{ 0.0 --.0 C92500 MNBR 5 85.0 1.25{ 0. Percent Maximum (unless shown as a range or minimum) Alloy * AGMA Ni UNS NO.50 0. 2. 2. --. For added copper alloy information.--- to to to 89.--.--.--.--.20 0. --.5 --.5 5.--.--.0 3.0 28.5 C90700 MNBR 2 88.0 11.05 0.5 to to to to to 66.--.0 28.--- to to 90. --.0 4.0 9.0 12.--.05 0.5 C92900 --.--.5 * Unified Numbering System.--.0 0.--.0 5. see SAE Information Report SAE J461.50 0.70 0. 9.30 0. 2.0 2.--.0 0.5 1.--- to to to to 88.--.--.25 2.0 0. former SAE & ASTM.0 --. phosphorus shall be 1.--.25 0.4 --.--. --. 0.--.9 5.--.15 0.0 --.--.0 10.0 1. Type Cu Sn Pb Zn Fe Sb (incl Co) S P Al Si Mn C86200 MNBR 3 60. 10.25{ 0.20 22.0 C95400 ALBR 3 83. --. 3.--. 2.0 11.05 0.--. 5.005 --.40 36.0 4.--. 3.0 1.--- to to to to 86.0 --. --.--.0 0.5 --.0 --.0 2.--.0 --.20 0. --. --. --. 160 C95400 ALBR 3 Sand. the Materials Factor. 2 Unified Numbering System. Centrifugal 80 (550) 40 (275) 12 --. Sand. --. 190 C95400 ALBR 3 Continuous (HT) 95 (655) 45 (310) 10 --. --. Centrifugal 90 (620) 40 (275) 6 --.--- C86500 MNBR 2 Continuous 70 (485) 25 (170) 25 112 --. 200 1 For rating of worm gears in accordance with AGMA 6034---A87. Continuous 45 (310) 25 (170) 8 90 --.--- C92900 --.--- C90700 BRONZE 2 Continuous 40 (275) 25 (170) 10 80 --. Centrifugal 65 (450) 25 (170) 20 --.--- C92500 BRONZE 5 Sand 35 (240) 18 (125) 10 70 --. 190 C95500 ALBR 4 Sand. 225 Continuous 110 (760) 62 (425) 14 --.--- C92500 BRONZE 5 Continuous 40 (275) 24 (165) 10 80 --.--- C92700 BRONZE 3 Sand 35 (240) 18 (125) 10 70 --. Gear Materials and Heat Treatment Manual Table 4---13 Mechanical Properties of Cast Bronze Alloys! Copper Minimum Typical Hardness % Former Minimum Minimum Percent Alloy Casting Method 4 4 AGMA Tensile Strength Yield Strength Elongation HB HB UNS. 125 C95300 ALBR 2 Sand. 160 C95400 ALBR 3 Sand. Centrifugal 65 (450) 25 (170) 20 112 --. 140 C95300 ALBR 2 Continuous 70 (485) 26 (180) 25 --.--. For added copper alloy information. 225 C86500 MNBR 2 Sand. 160 C95300 ALBR 2 Continuous (HT) 80 (550) 40 (275) 12 --. 190 C95500 ALBR 4 Continuous 95 (655) 45 (290) 10 --. Centrifugal 110 (760) 60 (415) 12 --. --. k s . 5 BHN at other load levels (1000 kgf or 1500 kgf) may be used if approved by purchaser. Centrifugal 65 (450) 25 (170) 20 --. --. --. Centrifugal 90 (620) 45 (310) 18 --. 160 C95400 ALBR 3 Continuous 85 (585) 32 (220) 12 --. also see SAE J462. 200 C95500 ALBR 4 Continuous (HT) 110 (760) 62 (425) 8 --. Centrifugal (HT) 75 (515) 30 (205) 12 --. 125 C95200 ALBR 1 Continuous 68 (470) 26 (180) 20 --. Table 3 footnote). ANSI/AGMA 24 2004---B89 . 180 Continuous C86300 MNBR 4 Sand. will depend upon the particular casting method employed.--.--.--- C90700 BRONZE 2 Centrifugal 50 (345) 28 (195) 12 100 --. For cross reference to SAE. --.--. --. see SAE Information Report SAE J461. 4 Minimum tensile strength and yield strength shall be reduced 10% for continuous cast bars having a cross section of 4 inch (102 mm) or more (see ASTM B505. former SAE & ASTM. --. --. (50 mm) kgf kgf C86200 MNBR 3 Sand.--.--- C92700 BRONZE 3 Continuous 38 (260) 20 (140) 8 80 --. 3 Refer to ASTM B427 for sand and centrifugal cast C90700 alloy and sand cast C92900.2 & Condition # Type ksi (MPa) ksi (MPa) in 2 inch 500 3000 NO. 190 C95500 ALBR 4 Sand. Centrifugal (HT) 110 (760) 60 (415) 5 --.--- C95200 ALBR 1 Sand. Centrifugal (HT) 90 (620) 45 (310) 6 --. --.--- C90700 BRONZE 2 Sand 35 (240) 18 (125) 10 70 --.--. --. 140 C95300 ALBR 2 Sand. properties such as low friction. particu- should consist of all gears produced from one melt of larly those used to transmit motion rather than pow- metal. It does not express the specific proper. (2) Heat treatments--- per base alloys is determined per ASTM E112 at 75X Through harden (anneal. development of engineering ure of any gear to meet hardness requirements speci. shall be 80 HB for static chill and centrifugal chill Plastics are being used at a rapidly increasing castings. Gear Materials and Heat Treatment Manual One test specimen should be tested from each castings and. the purchaser and gear manufacturer. Details of this sup. advances in gear mold design and upon by the purchaser and the casting producer. the lot should be accepted. using a 500 kg load. The following supple. The av- 4. Determination of hardness at or near the root er. and 70 HB for sand castings. The lot 4. and mentary requirement should apply only when speci. the producer ment of certain plastics as engineering material suit- should furnish specified microspecimens or photo. in particular. Heat Treatment (a) With proper foundry technique. AGMA 141.070 mm in the Stress relief web and 0. bars should be the same. Anneal ries as a function of cooling rate and section thick. normalize and temper. If this bar meets the be advisable to specify by use of photomicrographic tensile requirements. Heat treatment is a heating and cooling process ties of static chilled and centrifugal cast separate test used to achieve desired properties in gear materials. Normalize and temper ness. Common heat ties and characteristics of the casting which are great. (See Appendix A and fied by contractual agreement. Be- diameter is optional and should be agreed upon by cause of the wide range of non---metallic materials. quietness of operation. engineering data on the various types of non---metals The minimum hardness. treatments for ferrous materials include: ly dependent on design. Ferrous gearing may be through hardened or surface (b) An integral or a separate test bar simply sig.035 mm in the rim. the proper. molding technology. The minimum rate as gear materials in the fine pitch range. several wrought aluminum and beryllium cop- (6) Casting Hardness Control.Ferrous Materials. and mechanical properties. is usually most easily available from the producers.120 mm in the hub. data. 5. size.11 Other Non--. normalize. (1) Preheat treatments--- (c) The grain size of cast copper base alloys va. 0. are produced from non---metallic materials. gears. It may group of three test coupons cast. able for fine pitch gears. Quench and temper ugal castings is 0.) plementary requirement should be agreed upon by the casting producer and gear manufacturer. no lubricant. chemistry. The gear per alloys are occasionally used. or magnification. or within 1 inch (25mm) of the cast OD or as indi- cated on gear manufacturer’s drawing. Fail. phase distributions in the gear rim section. Im- hardness at or near the root diameter shall be agreed proved materials. and foundry technique. Many gears. should be mutually agreed upon by the consumer and Surface harden profile heated (flame and producer with reference to the various sections of the induction harden) and profile chemistry ANSI/AGMA 25 2004---B89 . Specifications are manufacturer can select at random any number of specialized and should be resolved between the user castings from a given lot to determine the hardness at and supplier. The grain size for cop.Metallic Materials. fatigue strength or wear resistance. Recommended maximum grain size for centrif. the two remaining specimens shall be tested. micrographs for each melt with the certificate of Non---metallic gears are usually selected for hardness. If standards both acceptable and non---acceptable the first bar fails to meet the specified requirements. resistance to water absorbtion. the tooth section. hardened when gear rating or service requirements nifies the melt quality poured into the mold to make warrant higher hardness and strength for improved the casting. and the successful use of plastic gears in many fied is subject to rejection. applications have all contributed to the establish- (7) Cast Structure. ability to operate with (8) Supplemental Data. In addition to erage properties of these two bars must meet speci- the more common non---ferrous materials used for fied requirements for acceptance of the lot. When required. and quench and (d) The grain size of static cast copper base alloys temper).12 Non--. The quench and temper ing.4 Quench and Temper. The normalizing and annealing pro- Specialized heat treatment for nonferrous mate.1 Annealing.3 Normalizing and Annealing for Metallurgical Stress relieve Uniformity. The tempered hardness va- treatment applied to the cast or wrought gear blank ries inversely with tempering temperature. per process on ferrous alloys involves heating to form however.” It results in low hardness and pro. Parts are in the “rough. Austempering is used. Table 4---3 gives hardness guidelines for some steel bility (minimum residual stress). fol- annealing. to part. and the hardness requirements permit) or is typically a pre.2 Normalizing. carbonitride. regardless of section dicates that the hardness and mechanical properties size. Annealing consists of heating ing reduces the material hardness and mechanical steel or other ferrous alloys to 1475---1650_F strength but improves the material ductility and (802---899_C). cesses are frequently used. normally air cooled from tempering temperatures.1. occur infrequently for steel gearing and 5. dimensional stability and im. with plain tions: carbon steels containing up to about 0.1. for through hardened (approximately 300 austenite at 1475---1600_F (802---871_C). The quench and tem- are.1. annealed gearing is shown in Table 4---2. normalizing (or normalizing and temper- lowed by a 1200_F (649_C) temper with controlled ing). Through hardening may be used before or after working. and ni. 1000---1250_F (538---677_C) after normalizing for (2) When the hardness and mechanical proper- uniform hardness. Normalizing consists of achieved from the quench and temper process are heating steel or other ferrous alloys to 1600---1800_F higher than those achieved from the normalize or an- (871---982 _C) and cooling in still or circulated air. However. 5. The gear is then tempered to a specific equal hardness through all sections of the temperature.1 Applications. of quench hardening. (1) When the gear application stress analysis in- cantly more than annealing. gas or liq- torted crystaline microstructures from mechanical uid.4. pering temperature must be based upon the speci- Annealing may be the final treatment (when low fied hardness range. generally below 1275_F(691_C). by rapid quenching. Modifications cooling to 600_F (316_C). as a homogenizing heat treatment for alloy steels. and quenching and tempering.1 Through Hardening Processes. followed to 480 HB) ductile cast iron gears. as quenched hardness. The hardness and mechanical properties 5. Cycle annealing is a term applied to a special There are generally three methods of heat treat- normalize/temper process in which the parts are rap- ing through hardened gearing. See 4. achieve the desired mechanical properties. vides improved machinability and dimensional sta.6 for discussion of hardenability. Through hard- steel to reduce metallurgical non---uniformity such as ened gears are heated to a required temperature and segregated alloy microstructures (banding) and dis- cooled in the furnace or quenched in air. Gear Materials and Heat Treatment Manual modified (carburize. Typical hardness for grades. either singularly or in rials should be recommended by the producer. normalizing at 1600---1750_F (871---954_C). normalizing does not increase hardness signifi. These processes are used in wrought 5. and furnace cooling to a prescribed toughness (impact resistance). neal process.1. therefore. The rapid cooling causes the gear to become harder and stronger by formation of NOTE: Through hardening does not imply martensite. material composition. In ascending order of idly cooled to 800---1000_F (427---538_C) after hardness for a particular type of steel they are. such as austempering and mar- tempering.4 percent car- bon. Temper- 5. (3) Post heat treatment--. for the specified material grade can best be achieved Alloy steels are normally tempered at by the quench and temper process. the gear teeth are formed. Typical specified hardness ranges for normalized tride) and tempered steels are shown in Table 4---2. ties required for a given gear application can be proved machinability. Selection of the tem- temperature [generally below 600_F (316_C)]. combination. Normalizing results in higher hardness than anneal- 5. not discussed. achieved more economically by quench and temper ANSI/AGMA 26 2004---B89 .1. with hardness being a function of grade of steel process should be specified for the following condi- and the part section thickness. which improves ductility and toughness 5. Specifying both tempering tem- (3) Section size peratures and hardness ranges on a drawing causes (4) Time at temperature an impractical situation for the heat treater. than by normalizing or anneal. achieving specified hardness on these sur- as guidelines for the effect of tempering temperature faces may not necessarily insure hardness at the roots on hardness. The ASM Handbook. should specify the following on the drawing. The major The hardness range should be a 4 HRC or 40 HB factors of the quench and temper process that influ. Parts are normally air cooled from the pends upon grade of steel (hardenability). care should be taken to avoid and unsuitable for service if tempered in the needlessly increasing material costs by changing to a temperature range of 800---1200_F higher hardenability steel where service life has been (425---650_C). However. particle inspection or dye penetrant inspection.1.4. 5. investigate the specific section for various gear configurations whose teeth material’s susceptibility to temper brittleness are machined after heat treatment. The tempering temperature ness of through hardened gearing is generally mea- must be carefully selected based upon the specified sured on the gear tooth end face and rim section.6 Maximum Controlling Section Size. and la. gear rating purposes.50 percent has been shown to formation. hardenability of alloy steel for through hardened If the part under consideration must be tem. His- hardness range. Molybdenum con. of teeth. flame hardening. signers often interpret this to mean that minimum taining the specified hardness range. gear blanks.25---0. and strength. control- tempering temperature. (3) Any testing required. The optimum tempering tempera.7 Additional Information. consult the following: eliminate temper brittleness in most steels. 5. duction hardening. with the tempering embrittlement phenome- ing. ing below 900_F(482_C) should be approved by the mum surface hardness which can be achieved. non from tempering in a lower range (3) When it is necessary to develop mechanical (500---600_F) often referred to as “500_F or properties (core properties) in sections of the part A---Embrittlement. while purchaser.2 Processing Considerations. the quenched hardness of the part. ANSI/AGMA 27 2004---B89 .1.1. De- ture is the highest temperature possible while main. Refer tests.4. “temper brittleness” and is generally consid- ered to be caused by segregation of alloying 5. For more in- tent of 0. or any non---destructive tests such as magnetic to 4.6 for more information on hardenability.4. (1) Grade of steel ser hardening).1. Heat Treating. in- 5. Temper- The steel carbon content determines the maxi. Hardness after hardness is to be obtained at the roots of teeth for tempering varies inversely with the tempering tem. Gear Materials and Heat Treatment Manual of a lower alloy steel.1. in. The designer ments (for example nitriding. It is best to specify a hardness range and allow the heat treater (1) Material chemistry and hardenability to select the tempering temperature to obtain the (2) Quench severity specified hardness.1. Since depth of hardening de- perature used. Volume 4. ling section size (refer to Appendix B) and heat treat Tables in the appropriate reference are available practice. The designer should not specify a tem- ence hardness and material strength are: pering temperature range on the drawing.5 Specified Hardness. the gear tooth root hardness should CAUTION: Some steels can become brittle be specified. Appendix B illustrates the controlling pered in this range. specified hardness must be met at this location. The elements or precipitation of compounds at maximum controlling section size is based upon the ferrite and prior austenite grain boundaries.3 Tempering. Tempering lowers hardness cluding the frequency of testing. For example. hardness dient which can be achieved through the part.4 Designer Specification.4. this has been interpreted to mean that the and the material. and proceed accordingly.” which will not be altered by subsequent heat treat. This phenomenon is called successful. (2) Quench and temper to a hardness range. If gear root hardness is critical to a specific design criteria. torically. The specified hard- or impact resistance. point range. electron beam hardening.4.4. Temper brittleness should not be confused 8th or 9th edition. 5. the alloy composition determines the hardness gra. 2. detrimental. duce hardness below the specified minimum. Stress relief is a thermal cycle Gearing is removed from the heat source and im- used to relieve residual stresses created by prior heat mediately hardened by the quenchant. Stress relief below ther to pass in the root diameter between flanks of 900_F(482_C) is not recommended. the gear element within the heat source (flame or in- STD---1684. finer pitch gearing (finer than Spin hardening of gearing involves heating all of 10 DP). An inductor or teeth to 1450---1600_F(788---871_C) followed by flame head which encompasses only top lands of quench and tempering. Gearing may also be tooth to tooth. The heat source (593---691_C). adjacent teeth. while the gear element is sub- 5. tion and heat treat condition prior to flame or induc. These pro. Cold Drawn. Stress Relieved site flanks of adjacent teeth. or gearing can also be progressively spin hardened by other fabricating techniques. to heat the root diameter and oppo- 5. An oxyfuel burner is used for teeth and adjacent flanks followed by quenching pro- flame hardening. Size limita. progressive- tion hardening significantly affects the hardness and ly hardened by passing the inductor between the uniformity of properties which can be obtained. ations. is time consuming and is not ening. cold drawn. Only the non---critical top duction hardening of gearing involves heating of gear lands of teeth are not hardened. therefore. Gear Materials and Heat Treatment Manual Military specification MIL---H---6875 and Mil--. economical for small. recommended that both quired depth. progressively temperatures with longer holding times are some- hardened by passing the flame or inductor and fol- times used. Shafting and treatments. Lower temperatures are sometimes and quench head traverse axially along the length to used when 1100_F (593_C) temperatures would re. but endurance or inductor is used for induction hardening. cold working.6 Heavy Draft. Material selec.2 Flame and Induction Hardening. or may fit or encompass Steel Bars. hardening techniques. only the surface is hardened during the designer and heat treater know what type of quenching (see Figs 5---1 and 5---2). An encircling coil or tooth by tooth vide wear resistance to the flanks. lowing quench head between the roots of teeth. machining. teeth followed by quenching are desirable from both tions and mechanical properties are listed in Table endurance or bending strength and wear consider- 4---5. welding. Spin hardening is more economical for the teeth across the face simultaneously by spinning smaller gears.5 Stress Relief. be hardened.1 Methods of Flame and Induction Harden. merged in a synthetic quench (termed “Delapena ing. Flame or in. roots of adjacent teeth. However. For further details see ASTM A---311. Both of these methods of surface hardening can Process”). This process. ANSI/AGMA 28 2004---B89 . In- NOTE: Stress relief below 1100_F(593_C) re.1. The ideal temperature spinning the shaft or tooth section within the heat range for full stress relieving is 1100---1275_F source and following quench head. duction coil) which envelopes the entire face width. ductor or flame heads or burner may be designed ei- duces the effectiveness. Heavy draft. bending strength in the roots is not enhanced. like other tooth to tooth be done by spin hardening. Lower Gearing can also be tooth to tooth. 5. stress relieved the top land to heat the top land and opposite flanks bars may be used as an alternative to quench and of each tooth. hardening pattern is desired. ameter are hardened. It is. fatigue properties of this steel may not be equivalent to quench and tempered Heat sources designed to pass between adjacent steel with the same tensile properties. tempered steel. or by tooth to tooth hard. because both the flanks of teeth and root di- 5. Resid- cesses develop a hard wear resistant case on the gear ual tensile stress in the roots of teeth may also prove teeth.1. When only the surface is heated to the re. Gear Materials and Heat Treatment Manual SPIN FLANK FLAME HARDENING FLAME HEAD FLAME HEAD FROM THIS TO THIS FLANK FLAME HARDENING FLAME HEAD FLAME HEAD FROM THIS TO THIS FLANK AND ROOT FLAME HARDENING FLAME HEAD FLAME HEAD FROM THIS TO THIS FLAME HEAD FLAME HEAD FROM THIS TO THIS THE HARDENING PATTERNS SHOWN ARE NOT POSSIBLE FOR ALL SIZES AND DIAMETRAL PITCHES OF GEARING. Fig 5---1 Variation in Hardening Patterns Obtainable on Gear Teeth by Flame Hardening ANSI/AGMA 29 2004---B89 . AND ARE DEPENDENT UPON THE CAPACITY OF THE EQUIPMENT. Gear Materials and Heat Treatment Manual SPIN HARDENING INDUCTION COIL INDUCTION COIL OR FLAME HEAD OR FLAME HEAD FLANK HARDENING INDUCTOR OR FLAME HEAD INDUCTOR OR FLAME HEAD FLANK AND ROOT HARDENING INDUCTOR OR FLAME HEAD Fig 5---2 Variations in Hardening Patterns Obtainable on Gear Teeth by Induction Hardening ANSI/AGMA 30 2004---B89 . 2. 5. Oil. These processes are also a more severe quench which increase the chance of ANSI/AGMA 31 2004---B89 .g.. Parts are rotated when encir- cling coils are used. for example. NOTE: AGMA quality level will be reduced approximately one level (from the green Wide faced gearing is heated by scanning type condition) after flame or induction hardening equipment while more limited areas can be heated by unless subsequent finishing is performed. Generally. reducing machined from solid copper combined with lami- core ductility of teeth and increasing distortion (see nated materials to achieve the required induced elec- Fig 5---2). martensitic stain- trolled by frequency. For more consistent ing have been used successfully on most gear types. in addition to air. the greater the frequency (AF) of 1---15 kHz and higher (radio) fre. ductor. used in place of more costly nitriding which cannot which include MAPP. followed by high radio frequency to develop the ing can affect the magnitude and repeatability of profile heated pattern. lizes encircling coils with power provided by high fre- quency vacuum tube units. Gear Materials and Heat Treatment Manual Three basic gases are used for flame heating. etc. A wide variety of materials can be flame or induction hardened. depending upon hardenabil. flame and induction hardening. shape of the in.4 Prior Heat Treatment. annealed structures can be hardened. high operator skill is required. itself to carburizing and quenching the entire part. The general applica- control of this process.2 Application. These of leaner alloy steels receive a quench and temper processes are used when gear teeth require high sur. tendency for cracking. spur. vides the best hardening response and most repeat- ity of the steel and hardening requirements. but size or configuration does not lend coarser than 3 DP. require longer heating cycles and burizing is not required. water or polymer solutions can be terial condition or preheat treatment. or separate by using an immersion tion from cold working. able distortion. herringbone. cold drawn material because of densifica- following spray.2. power density. Alloy steels of 0. pretreatment. bevel. root hardness and closer control of case depth is re- Simple torch type flame heads are also used to quired.5 percent car- 4---12 D. ductile.2. The higher spin coil induction heating using both low (audio) the alloy content with high carbon. however. In both carbon and alloy steels. however. Initial. The spin flame Induction hardening employs a wide variety of process generally hardens below the roots. mately 0.55 percent are suitable for flame or Contour or profile hardened tooth patterns for induction hardening. wrought) carbon and alloy steels. acetylene and propane. followed by quenching. stationary inductors. trical currents. steels with carbon content of approxi- ing heated. but hard- inductors ranging from coiled copper tubing to forms ens teeth through the entire cross section. Hot rolled material Quenching after flame or induction heating can exhibits more dimensional change and variation than be integral with the heat source by use of a separate hot rolled. normalized or These processes may also be used when the maxi. less steels. are burned under pressure to generate the flame Contour induction is preferred over flame when which the burner directs on the work piece. Contour flame hardening of the flanks and manually harden teeth. A quench and tempered ma- quench tank. tendency for cracking. Cast irons also have a high quency (RF) of approximately 350---500 kHz. except when spin flame hardening is applied. These economically generate some of the deeper cases re- gases are each mixed with air in particular ratios and quired. workpiece geometry and workpiece area be. Since there is no automatic roots is not generally available. results. including (cast and Induction heating depth and pattern are con.P.3 Material. Finer pitch gearing generally uti- gearing. tion of flame hardening is to the flanks only.35---0. malleable and gray cast irons. 5. If high root hardness is not required. 4140 steel with teeth face hardness. flame hard- Coarser pitch teeth generally require inductors ening is more available and more economical than in- powered by medium frequency motor generator sets duction hardening for herringbone and spiral bevel or solid state units. pro- used. gearing can be obtained by dual frequency bon or higher are susceptible to cracking. tures do. Flame and induction harden. it is recommended that coarser pitched gears e. ly low audio frequency is used to preheat the root Selection of the material condition of the gear- area. 5. helical. These struc- mum contact and bending strength achieved by car. to maintain the base metal near ambient tempera- These bending strength ratings are lower at the roots ture so the part mass can absorb heat from the heated of teeth when only the tooth flanks are hardened. Equipment varies from hand held 5. quickly and uniformly to obtain desired hardness. 5. induction hardened with lower kW capacity equip- ment by having the coils scan the length of the part Parts heated in an induction coil are usually while the part is rotating in the coil. When The allowable durability and root strength rating localized or air quenching is used. 5.2 Heating with Flame or Induction. polymer. Gas pressure and mix- the resultant hardening patterns. Repeatabiltiy becomes more difficult with flame hardening. heat input capacity of the equipment limits the pattern which and cycle time must be closely controlled. with care. a coolant is used for the different hardening patterns should be ob. of the quench media must be considered. The induction coil method is generally limited to 5. zone. Some of the more critical requirements are outlined below. pressure velocity and direction flame burners. oil and pacity of the equipment. structure.2. Repeatable process con- bon in the matrix. For coarser 5. Under- can be attained. spin trolled movement of burner heads. these methods are not recommended. Gear Materials and Heat Treatment Manual cracking.1 Repeatability. on a portion of the metal away from the heating zone tained from appropriate AGMA rating practices. yet minimize cracking. soluble oil. The quenchant should produce acceptable as ing single shot induction coil hardened is determined quenched hardness. The combined carbon in pearlite trol is essential for acceptable results.5 Hardening Patterns.6. With induc- will readily dissolve at the austenitizing temperature.2. nickel or tics.2. Quen- by the area of the outside diameter and the kW ca. Successful induction hardening of either gray or ductile cast iron is dependent on the amount of car. tained equipment since electrical power characteris- moting alloy additions such as copper. Root flame hardening by the tooth heating results in less than specified hardness and by tooth process is difficult and should be specified case depth.2. See Figs be such that heating rates across the burner face are 5---1 and 5---2 for variations of these processes and consistent from cycle to cycle.3 Quenching.6 Process Considerations. Flank hardened teeth usually have an integral pacity. Heat must be removed gears of approximately 5 DP and finer. ing in a coil. ing of heating gases must be uniform. the kW or power critical step. When the part is scanned while rotat- Flank or root and flank induction scan harden. There are two basic torches to tailor made machine tools with well con- methods of flame or induction hardening gears. hardening in an induction coil is recommended. mum diameter and face width of gears capable of be. chants used are: water. The hardening patterns shown are not possible for all sizes and diametral pitches. Several areas tive to flame or induction hardening. requirements should be worked out with the rate heating to the proper surface temperature is a supplier. Pearlite pro.6. Burner or inductor design. with appropriate supporting equipment and kW ca. Overheating can result in cracking. Spin Quench time and temperature are critical and hardening of finer pitches is also required when using in---spray quenching. inductor movement and integral quench intensi- molybdenum may be necessary to form this micro.6. Accu- pitches. must be considered when processing. ANSI/AGMA 32 2004---B89 . The annealed structure is the least recep. Spin merged in liquid during heating. quenched in an integral quench ring or in an agitated quench media. or the gear is sub- and finer. Burner head location must be precise from cycle to cycle. Long slender parts can be air.2. The maxi. this is usually not a problem with properly main- Pearlite microstructures are desirable. tin. For induction hardening. Equipment must hardening and tooth to tooth hardening. a spray quench usually follows behind ing (contour) can be applied to almost any tooth size the coil. ty can be readily controlled. for pitches of approximately 16 DP quench following the inductor. Flame hardening may also cause burning or melting of tooth surfaces. However. tion. 1 Heat Affected Zone. heating time. the difference between pitchline and root case When a tooth is through hardened. judgment should be exercised before omitting tem- 5. specified tempering temperature. It is good practice to temper after quenching aware that AGMA decreases load ratings for gears to increase toughness and reduce residual stress and which do not have hardened roots. Hardness may be lower as a result of prior flank from the critical root fillet or well below the heat treatment.70 0. (704_C---760_C) but does not get the hardness measured on the immediate surface hardened and thus has lower strength.5 Surface Hardness. the depth at the pitchline due to mass quench and mally defined as the distance below the surface at the hardenabiltiy effect. Contour induction hardening results in case 5. heat affected zone (HAZ) is a region that is heated to 5.50 0.6. mass and quenching considerations. depth of hardening. 60 MAXIMUM SURFACE HARDNESS 50 ∆ H= 10 40 EFFECTIVE CASE DEPTH HARDNESS 30 0. Flame hardened parts which are air quenched are self tempered.5 tooth height where hardness drops 10 HRC pitched gearing using a submerged quench decreases points below the surface hardness (see Fig 5---3).2.60 0.40 0. for particular processes. Surface hardness is 1300---1400_F. This zone and is primarily a function of the carbon content (see should be located either a minimum of 1/8 inch up the Fig 5---3). When root is also to be hard- when specified. depth of case at the root may be specified.30 0.2. Tempering should be for a suffi- ing standards should be consulted for appropriate cient time to insure that hardened teeth reach the stress numbers. ened. and 5. AGMA gear rat- crack susceptibility.7. alloy content. the separate tempering is unnecessary.20 0. However. Tempering is mandatory only depth does not apply. Gear Materials and Heat Treatment Manual 5.6 Effective Case Depth. effective case depth.2. Designers should be pering.7 Rating Considerations.2.PERCENT Fig 5---3 Recommended Maximum Surface Hardness and Effective Case Depth Hardness Versus Percent Carbon for Flame and Induction Hardening ANSI/AGMA 33 2004---B89 . Effective case depth at the root to be approximately 60 percent of depth for flame and induction hardened gears is nor.6. In flame hardening.4 Tempering.6. Profile hardening of fine 0.2. root diameter.80 CARBON CONTENT --. For tooth by and holding low carbon alloy steel (0. Gear Materials and Heat Treatment Manual 5. ations. dimensional hardening. hardness pattern and depth can be checked by polishing end faces of teeth Gear blanks to be carburized and hardened are and nitric acid etching. and suitable core properties based on selection (6) Depth of hardening required and the loca.1 Applications. Gearing may be atmosphere cooled after 5. quently given a refrigeration treatment to transform (3) Hardening pattern required. high speed and aerospace tion specified when destructive tests are required. number of pieces inspected. held at temperature to stabilize while not be accurately measured. or writ. Case depth should be deter. Carburized gearing is also used for ANSI/AGMA 34 2004---B89 .9 Documentation.28 per- tooth hardening. causes additional carbon to diffuse into the steel ate superficial or micro---hardness tester. instances. Although it is not always practical. power is lowered and travel is stability and possible grain refinement consider- sometimes increased as the inductor ap. and direct quenched. carburizing to below approximately 600_F (315_C) ten specification should include the following in. 300---375_F (149---191_C). a segment of a gear can be hard. gear cannot be sectioned. gearing is used when optimum properties are re- ened parts). normalize. High surface hardness. normalize and temper or quench and temper to specified hardness before carburize hard- NOTE: During tooth by tooth induction ening. gear- tence of a hardness pattern can be demon. quired. The drawing. Improved load distribution can be obtained by subse- (9) Magnetic particle inspection. if tern).2.2 Case Depth Evaluation (Hardness Pat.3. on larger gearing. mill applications. Grit blasting is also occasion.7. the only positive way to check case 5. After carburizing for the appropriate time. particularly at the root area. (3) Results of magnetic particle inspection. if required. of the appropriate carburizing grade of steel. In these sidual stress from rough machining. (899---982_C) in a controlled atmosphere which mined on a normal tooth section.2.3 Carburizing. Hardness can also be checked on end faces critical anneal at 1100_F---1250_F (590---675_C). This is to prevent chining before carburizing may be used to remove re- edge burning and cracking. in the highest AGMA gear tooth ratings for contact (7) Whether destructive tests are to be used for stress. result tion(s) at which the depth is to be obtained. precision gear units and also large open gearing for and the number of pieces inspected. fa- (5) Those areas where the surface hardness is to vorable compressive residual stress in the hardened be measured and the frequency of inspection.2. case. Conventional hard gear 5. hardness may be lower at the ends. The heat treater should finishing (skiving and grinding) results in some sacri- submit the following information: fice of beneficial compressive stress at the surface (1) Surface hardness range obtained and the and substantially increases costs. ing will usually be cooled to 1475---1550_F strated by acid etching. at flank and root areas. When a (typically 0. retained austenite and retempered.07---0. pitting resistance and root strength (bending). gearing is usually tempered at designation. and then reheated in controlled atmosphere to formation: 1475---1550_F (802---843_C) and quenched. An intermediate stress relief before final ma- proaches the end faces. for through hardened and other types of surface (8) Tempering temperature. Gas carburizing consists of heating depth is by sectioning an actual part. This is done for machinability. order. 5. Carburized and hardened (Maximums may be specified for induction hard. particularly required. generally preheated after the initial anneal by a sub- ally used. After (1) Chemical analysis range of the material or quenching. Carburized gearing is used in enclosed gear units (2) Depth of hardening obtained at each loca. Gearing may be subse- (2) Prior heat treatment. exis. (4) Minimum surface hardness required. using an appropri.10 percent carbon at the surface). cent Carbon) at normally 1650---1800_F ened and sectioned. hardened gearing because of higher fatigue strength. but actual depth can. if required.8 Specifications. quent hard gear finishing. (802---843_C). determining the depth of hardening and the frequen. In this case. high case strength. for general industrial use.70---1. Carburized gear ratings are higher than the ratings cy of such inspection. maintaining the carbon potential. structure can be determined at the center of the rack gears. present manufacturing problems. Gear Materials and Heat Treatment Manual improved wear resistance. ¢ 7. The bar length should be Some gearing does not lend itself to carburize 2---3 times the diameter.25 inch (57 mm) carburize gearing is currently in the 120 inch (3048 to less than D. The minimum inscribed diameter on a wear resistance. at mid length of a test bar). Most of this large gearing re- quires tooth finishing (skiving and/or grinding) after 1 1/2 DP 3. hibitive. pitting bar diameter. approximate the inscribed diameter at mid height of the tooth cross section. mum thickness is 70 percent of the appropriate test tivity. the following: toughness. notch sensi. performance.0 inch (50 mm) long bar may the available equipment and controls make it a reli. Specified finish opera.25 inch (32. 4 1/2 DP 1.5 able process.3. and the quality can be audited.5 inch (89 mm) on the basis of material hardness and hardenability. (16 mm) diameter by 2 inch (50 mm) long. case depth. or can be machined after carbu. obtained on the test bar and the parts. 5. complex shapes. core hardness and core micro- torts and cannot be straightened without cracking. Press quenching after carburizing can be used to minimize Table 5---1 distortion. in order that the hardness moved during tooth finishing.0 inch (76 mm) long difficult to carburize due to the limited number of available furnaces for processing. Performance criteria include. hardening because of distortion. test disc (or plate dimensions) should be a minimum Reference should be made to Table 4---1 for a list of of three times its thickness.3. and core DP. core properties meet specifications. through all heat treatments. to less than D. fatigue strength. Surface hardness. Test Bar Size for Core Hardness tected from carburizing (masked) to permit machin. Consideration should be given to measured with microhardness testers which produce evaluation of that portion of the case that is not re.3. Those testers which produce Dia- (normal.5 DP gear- hardness can be specified to reasonably close toler. One inch Carburizing technology is well established and (25 mm) diameter ¢ 2. is considered mond Pyramid or Knoop hardness numbers (500 satisfactory for determining effective case depth of gram load) are recommended. values obtained are representative of the surfaces or A section. thin sections. typical carburizing materials and Appendix C for The recommended test bar diameter for bevel case hardenability considerations.0 inch 4 1/2 DP (130 mm) long mm) diameter range.0 mm) Gearing beyond 80 inch (2032 mm) diameter is and finer D. The size of the bar for coarser than 1. Determination ing after hardening. When measuring di- ANSI/AGMA 35 2004---B89 . and economical considerations. Test bars are used diameter of the normal tooth thickness at mid face to show that the case properties and. carburized helical and spur gearing to 4 1/2 DP. when required. DP BAR SIZE rizing and slow cooling before hardening. gearing is to be approximately equal to the inscribed 5. be used for coarser pitch carburized gearing to 1.3. an actual part sarily the same heat. The tions after hardening depend upon accuracy and con. Gearing which dis- When specified. and coarser D.2 Materials. ¢ 3. ¢ 8. and operational characteristics. width. but are Test discs or plates may also be used whose mini- not limited to.3 Control With Test Bars. ¢ 5. Maximum size of 2 1/2 DP 2. Case hardness should be ening treatments.0 inch (76 mm) carburizing and hardening. Selection should be made 1 1/2 DP 3. Test bars should When disagreement exists as to the properties be of the same steel type as the gear(s). and should ances. with a ground and polished surface area being tested. small shallow impressions. cleanliness. Selected areas of gearing can be pro. including all post hard.0 inch 2 1/2 DP (180 mm) long 5. bending strength.1 Case Hardness. Material selection is an integral part of the design process. test bar should have minimum dimensions of 5/8 inch tact requirements for all applications. but not neces.0 inch (205 mm) long chemistry. ing should be mutually agreed upon. Bars should accompany gearing may be sectioned for analysis. parts not round bar size shown in Table 5---1 according to di- designed for finishing or where finishing is cost pro- ametral pitch. 005 inch Care must be taken to ensure that the turnings are ANSI/AGMA 36 2004---B89 .2 Core Hardness. 5. height case depths.004 quent machining. Microhardness tests for surface hardness should When steels of high hardenability such as 4320. 4820. section (refer to 5. The mi. if secondary transforma- core hardness equals 47 HRC.25 mm) beyond the depth at which Test specimens must be clean and machined dry. Gear Materials and Heat Treatment Manual rectly on the surface of a case hardened part or test (0. when core hard- case. Effective case depth at or Equotip are also used when penetration hardness roots are typically 50---70 percent of mid tooth height testers can not be used. sive tooth distortion and a loss of core ductil- ity can also occur. if bar ence.002 to 0. Grinding in steps through the case would be 5.004 inch (. 50 HRC is obtained.002 to crohardness tester. direct surface checks will not necessarily indicate their pres.10 mm) from the edge on a pol. Parts of this type should be 5. case. Section 3.25 mm) increments through the not fall below the minimum.005 inch (0.05 to . Surface carbon Section 3.010 inch (0. Exces- the surface.0015 inch (0. content may be determined from a round test bar by taking turnings to a depth of 0. When required.13 mm). Care must be taken during grinding and of the steel may prevent obtaining a hardness less polishing not to round the edge being inspected and than 50 HRC across the tooth section. integrity during cooling or in tempering for subse- crohardness traverse should be started 0. However.3. NOTE: See definition of case depth of carbu- Low readings can be obtained when the indentor rized components. NOTES: See definition of core hardness.05 to . the high through hardening characteristics the surface. 8627. and tips may be 150 percent of mid tooth to the case depth relative to the depth of the impres.3. hardness. Care should also be exercised in bar.3.05 to 0. depth should then be determined in the following manner: Measure the base material hardness at mid NOTE: Direct surface hardness readings tooth height at the mid face. discussed in 5. This type of inspection may be necessary have several disadvantages.3 Case Depth --. depending on accuracy desired and depth of ness is specified. The procedures used with spectrographic techniques.10 mm) below the surface and extend to in 0.3. 9310. can cause varia- for this purpose. sion made by the tester. tions and for use of lower hardenability steels giving consideration to the size of the specimen as such as 4620 and 8620.4 Case Carbon Content.01 inch (.3.05 to .3. effective case depth tion products are present below the first sev- should be measured at 52 HRC). ished cross section of the tooth is more accu. Favorable com- for accurate micro---hardness readings near pressive surface stresses are lowered. parts. Occasionally banding. Case depth in these eral thousandths of the case. Care should be exercised to maintain surface pare the specimen for case depth evaluation. and 3310 are used for fine a depth of 0.002 to 0. Microhardness inspection 0. For each one HRC point (ASTM E18---79) or file checks at the tooth above 45 HRC.3) should be used to pre. which results from Spectrographic techniques have also been developed the steel melting practice. used to prepare the cross sectioned specimen for Test specimens should be carburized with the case hardness (refer to 5. penetrates entirely or partially through the case.002 to 0. The case not to temper or burn the ground surface. Bar should be straightened to with- inch (.13 mm) is used. Other instruments such as Scleroscope when starting the traverse.3.3. one HRC point should be added to tip or flank will generally confirm the case the 50 HRC effective case depth criterion (example. Carbon gradient can also be deter- tions in core hardness during testing with a mi- mined on the bar by machining chips at 0.10 mm) below pitches. Consideration must be given case depths.004 size has been previously correlated to the gear tooth inch (.3. at least 0. core carefully reviewed for case depth specifica- hardness may be determined by any hardness tester.038 mm) (TIR) before machining. superficial or standard Rockwell A or C scale establishing the perpendicular to the mid tooth point may be used. instances may also be measured on a test bar. NOTE: Through carburized fine pitch teeth rate. be made on a mounted and polished cross---section at 4327. These variations should 0.Effective.3). Usually an interval of 0.3. reduce fatigue strength of the material. Use of refrigeration may require When additional characteristics are required. (---7_C) to ---120_F (---84_C). reduce fatigue strength to a moderate de- (3) Surface hardness range. The microstructure may (3) Subzero Treatment (Retained Austenite be determined on a central normal section of the test Conversion Treatment).3. but may not show discernible pable of maintaining a carburizing atmosphere with ferrite. Microcracks can result which can (2) Case depth range (refer to Table 5---2). above characteristics. Partial decarburization will result in a lighter (2) Atmosphere Control.13 mm) be- stop---off compounds. and break up the excess carbide. ANSI/AGMA 37 2004---B89 . Gear Materials and Heat Treatment Manual free of any extraneous carbonaceous materials prior continuous atmosphere control is preferred. 5. but oth- to analysis. Furnaces should be ca. low the specified minimum. and accuracy of temperature recording and con.3. shade of martensite. This is characterized by 5. after being prop. when the peak carbon content is subsur- cluding: face. Surface decarburization as (6) Areas to be free of carburizing by appropri.60 percent carbon.4 Specifications. (5) Decarburization. Furnace equipment Gross decarburization can be readily detected with temperature uniformity. gree. close temperature con. Carbide networks (3) Case microstructure. (5) Subzero treatment. for example. Instrumentation for bon content falls below approximately 0. (1) Temperature Control.005 inch (. whole or part: (4) Carbide Control. agreement between the customer and sup- the following additional items may be specified in plier. should be avoided whenever possible as they tend to (4) Surface carbon content. When the surface hardness bar or tooth. the heat treater should be giv- en the following as a minimum: NOTE: Caution should be exercised in the use of refrigeration treatment on critical (1) Material. er approved methods may be used. defined for carburized gearing is a reduction in the ate masking by copper plating or use of commercial surface carbon in the outer 0. microstructure. parts should be tempered before and after 5. which can be obtained from outer portion of the case. Hardness in this area trol instruments. typically 1650_F(900_C)in a lower carbon potential tated oil quenching. are shown in Table 5---3.60 percent. gearing. Precision an increase in carbon content with increasing depth. Controls should be checked and will be substantially lower. typically 0. atmosphere. is low due to excessive retained austenite in the case erly polished and etched. Approximate minimum results in a heavy continuous carbide network in the tooth core hardness. to diffuse (2) Core microstructure. preferably mounted.3. microscopically as a lighter shade of martensite and trol. carburizing requires close control of many factors in. it may be necessary to refrigerate the Microstructure will vary with the core hardness parts to transform the retained austenite to marten- as related to steel hardenability. section size and site.5 Carburizing Process Control. parts should be reheated to some typical carburizing grades of steel and good agi. It will result in reduced hardness if the car- controllable carbon potential. To aid in obtaining the refrigeration.5 Microstructure. To minimize micro- cracking. clearly defined ferrite grains. When high surface carbon (1) Core hardness. The refrigeration treatment may vary from 20_F quench severity.3. calibrated at regular intervals. 030 12 0.256 1.0.105 0.480 --.400 0.7 --. 0.075 3.075 --. 5 For gearing requiring maximum performance. 0.025 --.7.13. heavier case depth than shown in table may be required. 0.075 --.676 --.0.628 2.9 1.2.300 --.5 0. 2 Gears with thin top lands may be subject to excessive case depth at the tips. 3 Case at root is typically 50---70 percent of case at mid tooth.0. Shallower case tions).205 0.075 --.0.3 on carburizing will generally triding.180 --.120 --.026 --.075 --.314 5.200 --.2 1.5 --.3.6.1.040 0.25 1.7 --. 0. multiply values given by 25.050 --.2.076 to 0.10.040 --.170 --.5 --.400 0.090 2.976 0.070 --.1.1.090 2. 0.140 0.180 0.0. It is limited to shallower cases for finer than is usual for production carburizing.035 --.030 inch (0.131 13.1.090 0.0.060 0.4.0.090 1.0 0.571 2.1 & less 2.2.198 8.400 --.3 --.6 1.2 --.155 0.75 0.0.125 0.010 --.600 --.200 --. One of the ANSI/AGMA 38 2004---B89 .393 4. 0.020 0.2.040 0.5 0.251 6.0.010 --.080 --.060 --. Its effect on pitch gearing since the process must be conducted at steel is similar to liquid cyaniding and has replaced lower temperatures than carburizing.370 0.026 --.020 --.325 & more 0.6 --.3 1.13.040 --.020 --.2 0.0.157 10.090 2.090 0. For further details refer to AGMA 2001---B88.860 --.045 --.0. and for 5.0.180 --.676 0.003 apply to carbonitriding.1.230 0.300 0.200 0.428 --.75 0.0. Information in 5.5 --.1.0. to 0.145 --.7 0.075 --.6 1.047 1.0.0.040 --.170 --. 0.570 1.045 --.976 --. Un---ground worm gear cases may be decreased accordingly.230 --.1.5 --.698 2.5 to 5 percent anhydrous ammonia is establish methods for specifying carbonitrided gear.020 --. Helical Worms with Pitch 1 Thickness Diametral Circular Bevel & Mitre 6 Ground 7 Pitch Pitch Threads 16 0.728 --.449 3.1. depths require prohibitive time cycles.090 --.5 0. 0. The purpose of this Section is to Normally 2.5 --. 0.860 0.3 1. 0.200 0.1 2.828 0. 0.224 7.2. with noted exceptions.0 0.1.025 0.5.015 --.090 1.020 0.76 mm) maximum.090 0.25 0.480 0. For very heavily loaded coarse pitch ground thread worms.0.050 8 0.828 & more 0. 7 Worm and ground---thread case depths allow for grinding.030 14 0.0.205 0.1 0.897 1.094 1.0.9 --.090 1.3.080 --.370 --.3 --. 5.1.090 1. Specified case depths are usually from 0. loading and manufacturing procedures to determine the required effective case depth.112 17.028 0.5 0.070 --.8.090 2.055 6 0.030 0.3 --.0.105 0.1. Land width should be calculated before a case is specified.4 Carbonitriding. Typically carbonitriding is carried out at lower temperatures.0.523 3.045 --.0. All other pitch measurements should be converted before specifying a case depth. 0.5 --.2.075 --. 0.105 --. 0. 0.5 0.1 & less 2.300 0. 6 To convert above data to metric.030 --.075 --. 0.75 2.5 0.0.075 --.6 --.4 5 Normal Normal Range of Range of Diametral Tooth 2 Normal Normal Spur.060 5 0. 0.0.070 0. added to the carburizing atmosphere when carboni- ing.8 1.370 --.0.785 2.060 3. 0.728 0.480 0.0 1.400 0.0. Use of carbonitriding is more restricted than depths are generally specified for carbonitriding carburizing. 1550---1650_F (843---899_C). Gear Materials and Heat Treatment Manual Table 5---2 Typical Effective Case Depth Specifications for Carburized Gearing Effective Case Depth (inches) to RC 50 3.2.060 4 0.080 0.7 0.055 7 0.4.0.3 0.098 17.040 10 0.7 0. Deep case cyaniding because of cyanide disposal problems.090 1 All case depths are based on normal diametral pitch.1 Applications (Advantages and Limita- shorter times than gas carburizing. 0.075 --.600 0. 4 The case depth for bevel and mitre gears is calculated from the thickness of the tooth’s small end.075 --.4 to determine mm equivalent.060 --.1 --.025 --.2 --.0. 0.8 --.050 0.5 1.025 --. detailed studies must be made of the application. . The car. Nitrided gears are used particular material. microstructure.001 inch 8620 18 24 26 28 (0. 4118 and 8620 high hardness cases can withstand applied loads. are required in order to specified and measured as effective or total. hardnesses ob- bonitrided case has better wear and temper resis. if higher core hardening can also be achieved with the ion nitriding hardness and deeper case depths are required for process. Use of H band steel is the of distortion. Nitride tooth growth and distortion. means of specifying. selection and processing of materials. is present.4. the Nitralloy grades. and definitions and inspection of depth of tance than a straight carburized case. This section covers the ability in lower alloy or plain carbon steels.treatments.2 Materials. N will develop higher case hardness. and when through hardened gears do normal method of hardenability control. steels such as 1018. tainable.3 Pre--. parts can all be specified and evaluated as prescribed vanadium.4. 18 22 25 pound layer to a depth of 0. which requires a thor- Approximate Minimum Core Hardness of ough stress analysis (for other than wear applica- Carburized Gear Teeth tions) of the effectiveness of the case for coarse pitch 1 gearing. 1022. 5. for carbonitrided 5. The practical limit on case depth is about Table 5---3 0. involves heating and quench techniques and still achieve hardness. Case depth.3 Specification and Inspection.025 mm) or less. 1 Depending upon the Jominy curve of the 5.020 inch 1020 --. Parts to be nitrided must provide information. and in. Gear Materials and Heat Treatment Manual advantages of carbonitriding is better case harden.2 Materials. thus reducing mosphere (10 to 30 percent dissociation). Case depth is gularly or in combination. and steels with chro- depth. sorbed into the surface to form hard iron and alloy ni- cable. These processes result 8822 25 30 32 34 4320 23 27 30 33 in a wear resistant surface layer of 0. maximum hardness will when gear geometry and tolerances do not lend typically be 8---10 points higher than the themselves to other case hardening methods because minimums listed. 4340.00 percent. Aluminum herein should be fully understood before specifying containing grades such as Nitralloy 135 and Nitralloy carbonitriding for industrial gearing. Ni- steels are used for carbonitriding.50 mm) which enhances fatigue strength.0 mm) maximum. 5. with a nitrogen com- 4620 --. carbonitriding may not be appli. spection of nitrided gearing. trided gears should not be specified if shock loading 5.5 Nitriding. aluminum. be quenched and tempered to produce the essential- ANSI/AGMA 39 2004---B89 . Carbonitriding hardening. However. either sin- in the section for carburized gearing. These holding at a temperature between 950---1060_F facts.0 hours in an aerated salt 4820 27 33 35 36 bath or atmosphere. During nitriding. etc. The advantages and limitations as described mium contents of 1. depend.4 and 5.5. and molybdenum.38---0. Steels containing chromium.040 inch (1. hardness.010 Typical steels suitable for nitriding are 4140.5 to 4. gearing because lower austenitizing and quenching which has had a quench and temper pretreatment temperatures can be used along with less severe and is usually finish machined.015---0.5. The purpose of this section is to 5.00 to 3. nitrogen atoms are ab- bending resistance. 1117. can be used to minimize distortion in finer pitch Conventional gas nitride hardening of gearing. result in the lower (510---571_C) in a controlled cracked ammonia at- core hardness mentioned previously.5) Pitch 2---3 4 5---6 7 & UP should not be confused with aerated salt 3316 34 36 37 38 bath nitriding or nitrocarburizing in which 9315 32 34 36 37 nitrogen is absorbed into the steel surface at 3310 31 33 35 36 approximately 1060_F(570_C) for short 9310 28 31 33 34 cycles of 2. inch (0. 4022. due to inherent brittleness of the case. ing upon application. 14 16 18 (0. trides. Typically carbon and low alloy Nitrided gears are used on applications where thin.1 Applications.5. not provide sufficient wear and pitting resistance.25 mm) are generally specified as total case 4150. along with lower alloy steels. Cases shallower than 0. Hardness HRC Minimum Grade NOTE: The above processes (5. form stable nitrides at the nitriding temperature. (14---28_C) below the tempering temperature may also be required prior to finish machining to relieve A two stage nitriding process (two temperatures machining stresses before nitriding. such as blind holes and ing. The nitride process is restricted by and spe- rization. The process can provide flexibility in nitriding process should be considered. nitrided ing.001 inch trided hardness is lessened appreciably by decreased (0.0005---0.005 inch vide sufficient strength to support the case under (0. This must be consid.5. ni. the newer ion bombardment. However.013---0. ness is also dependent upon the analysis of steel. small orifices.0007 inch (0.5. core hardness and material selection constraints. and time of nitriding. Core hard- etary paints specifically designed for this purpose. causing distortion.008 to 0. This face contamination. The amount and direction of 50_F (28_C) above the nitriding temperature.5 Specific Characteristics of Nitrided Gear- case which may spall under load. Microstructure must be free of pri. with increased percent of ammonia dissociation at the second higher temperature) generally reduces In alloys such as series 4140 and 4340 steels. surface hardness. Core hardness obtained plated with dense copper 0.1 Material Selection. growth or movement should be determined for each Approximate core hardness ANSI/AGMA 40 2004---B89 . degree of ammonia dissociation. Selection of the chipping during handling and service. In order to guarantee nitrogen should be avoided by tempering at approximately adsorption it may be necessary to remove surface ox- 50_F (28_C) minimum above the intended nitrided idation by chemical or mechanical means. tin plate 0.13 mm) thick.5.0003 to 0. nitriding. or by coating with propri- load and tooth bending and rim stresses. in 5. The white layer thick- core hardness prior to nitriding. face condition.5. range with a tempering temperature that is at least cess are held constant. Variables in normalizing. to effect nitrogen penetration of the surface by ion If distortion control is very critical. mary ferrite. temperature after quenching. plication.4 Nitriding Process Procedures. Nitriding over decarburized steel causes a brittle 5.5. form increase in size.2. ered when selecting tempering or stress relieving The ion nitride process uses ionized nitrogen gas temperatures. grade of steel is limited to those alloys that contain metal elements that form hard nitrides as discussed Where it is desired to selectively nitride a part. ing of geometric problems. Sharp corners or edges become brittle when ni- trided and should be removed to prevent possible 5.5. such as is produced by annealing and 5. The nitriding process will cause a slight uni.5. In order to minimize The nitriding process affects the rate of nitrogen distortion of certain gearing designs. the thickness of the white layer to 0.026 mm) maximum. cified by case depth. which produces a brittle case prone to the nitriding process are the combined effects of sur- spalling. residual stresses temperature. Nitriding does not lend itself to every gear ap- surfaces subject to stress should be free of decarbu. Nitriding determining the type of compound produced.018 mm) in the quench and temper pretreatment must pro- minimum thickness. intermediate adsorption and the thickness of the resultant brittle stress relieving after rough machining at 25---50_F white layer on the surface. Gear Materials and Heat Treatment Manual ly tempered martensitic microstructure required for part by dimensional analyses both prior to and after case diffusion. The can be accomplished at lower temperatures with ion process can also be tailored to better control nitrid- nitriding than those used for conventional gas nitrid. Therefore. ness requirements limit material selection to those Nitrided parts will distort in a consistent manner steels that can be tempered to the core hardness when all manufacturing phases and the nitriding pro.2 Core Hardness. the surfaces to be protected from nitriding can be 5. Nitrogen adsorp- from quench and tempering may be relieved at the tion in the steel surface is affected by oxide and sur- nitriding temperature. At least three hardness tests should 4150 30 be made beyond the depth at which core hardness is 4340 32 obtained to assure that the case depth has been Nitralloy 135 34 reached. stimulated emission of radiation) or electron (kinet- tion.4 Case Depth. commercial heat treaters. Steel Type Hardness. hardness will result from less alloy. Lower core hardness does not support the hard. Lower core cessed in the same manner as the parts it represents. if --. (3) Minimum surface hardness Table 5---4 (4) Minimum total case depth Approximate Minimum Surface Hardness (5) Maximum thickness of white layer. including laser heat treating and electron beam heat treating.Nitrided Steels required (6) Areas to be protected from nitriding by Minimum Surface masking. or the surface hard- hardness nitrided case. surface. specified chemical analysis range and must be pro- thin case as well as higher core hardness. Gear Materials and Heat Treatment Manual obtained on typical nitrided steels are as follows: most specifications only specify a minimum case Minimum Surface depth requirement. disc or limited by the concentration of hard nitride forming plate section. respectively process. larger section size. if required Steel Type Hardness (7) Nitriding temperature R15N HRC! (8) Metallurgical test coupons 4140 85 48 4150 85 48 5.5. while the underlying ence the design’s minimum required case depth. can be used for determining case depth elements in the alloy and the core hardness of the of nitrided parts. should have the following specified: Approximate minimum surface hardness which (1) Material grade can be obtained on nitrided steel is shown in Table (2) Preheat treatment (see 5.2) 5---4. for example 1/2 to 1 inch (13 to 25 5. Nitralloy (contains Al) 90 60 Both laser and electron beam surface hardening of gears are selective in nature and are generally ap- 2 1/2 percent Chrome 89 58 (EN 40B & 40C and plied to gears smaller than those routinely hardened 31CrMoV9)@ by other methods. Use of electron beam heat treating for gear ANSI/AGMA 41 2004---B89 . A test bar.6 Specifications. Surface hardness and core hardness will influ. The test section must be of the same gear. ic energy of electrons) beam. tive industry. Gearing may also be 4340 84 46 heat treated by other means.6 Other Heat Treatments.5. Lower core hardness results depth need only be performed when the results of the in a microstructure which causes a lower surface test bar are cause for rejection. surface hardness of the test bar. such as quantity production for the automo- NOTE: Data infers a 269HB minimum core hard.5.5. Parts which are to be nitrided nitride case depth. reduced quench severity and a greater degree of Sectioning of an actual part to determine case martensite tempering.5. The production quantity of any gear must be sufficient to justify the cost of capital 1 Converted to HRC equipment and set---up to surface hardened by either 2 British and German analyses. HRC Case depth should be determined using a micro- 4140 28 hardness tester.3 Surface Hardness. Surface hardness is mm) diameter with a length 3 ¢ the diameter. Surface hardness will also increase with increasing 5. since it limits the ability to ness of the part(s) is not within 3 HRC points of the form high concentration of hard metallic nitrides.5. Thermal energy for heat- 5. These processes are not available from ness. mass provides the heat sink to quench harden the Since the diffusion of nitrogen is extremely slow.5. The specified case depth for ing the surface to the austenitizing temperature is nitrided gearing is determined by the surface and supplied by either the laser (light amplification by sub---surface stress gradient of the design applica. resulting from heat treatment occur principally when but slow enough to reduce distortion and avoid steel is quenched. brine and hardened with a beam impingement angle of at least gases. and is better suited for flat than curved sur. parts can easily crack annealing. steel from a suitable elevated temperature. hardness. to full gear tooth con. These changes occur in both cracking. and diffusion controlled sur- if made of high---carbon. The geometry Tempering of the hardened structure reduces the will affect how quickly and uniformly the quenchant volume. mechanical and thermal stresses and microstructural The main factors which control the quench rate transformations.8. 9th Edition. Each variety is available with a wide range of 25 degree (25---90 degrees impingement angle quench characteristics. water.8. be avoided. The preferred microstructure after must consider movement during heat treatment. Quenching the structure to marten- are: part geometry. Each quenchant should be 5. that influences the microstructure. por bubbles and restrict the flow of quenchant should tours. Gear Materials and Heat Treatment Manual teeth is restricted. Section size modification may be required along with added stock The designer’s or heat treater’s responsibility is for grinding or machining after heat treatment. However. The quench needs to be fast 5. how severe the quench has to be for a particular part Distortion is due to mechanical and thermal stresses geometry. Thermal processes such as with perfectly uniform sections. and phase transformation. The The temperature of a water quenchant is more criti- quenching process is one of the major operations cal than that of an oil. however. molten salt. High induced stress can result or substantial section size changes. especially if tions than processes that require liquid quenching. improperly tempered or stress relieved. degree of site prior to tempering results in steel growing in size. Agitation is externally produced movement of ing of gear teeth. high---hardenability steels face hardening processes such as nitriding. Distortion of gearing during heat chanical properties and residual stress distribution. for flank and root contour surface harden. Volume 4 on Heat Treating pumps in the quench tank or by moving the parts for additional information on laser and electron through the quenchant. 5.7 Quenching. It is good 5. me. normalizing. as well as other modifications of heat treatments applied to gearing.1 Causes. tempering still result in a volume and size increase. Dual laser beam optics have been developed.8 Distortion. The temperature of the quenchant may affect its ability to extract heat. Delayed quench cracks not require liquid quenching.2 Quenching and Tempering. beam heat treating. which do and the quench is too severe. Dimensional changes of gearing enough to avoid secondary transformation products. the quenchant past the part. Quenching is the rapid cooling of used within its appropriate range of temperature. agitation and quench temperature. Tol- quenching is primarily martensite. polymer. Table 5---5 associates some range). Process variables and de- sign considerations have a significant effect upon the Quench cracks usually originate at sharp corners amount of distortion. This is true because the stream of electrons There are a variety of quenchants to choose from must have line of sight access to the surface to be such as: oil. The material hardenability will determine quenched and tempered and surface hardened gears. The degree and unifor- mity of agitation greatly influences its rate of heat re- Reference should be made to the ASM Metals moval. Pockets which trap va. even in quench cracking. Quenched and practice to immediately temper after quenching if tempered gearing changes size and distorts due to quench crack problems are a concern. type of quenchant. erancing must consider these changes. treatment is inevitable and varies with the hardening assuming the gear has been properly heated before process. ANSI/AGMA 42 2004---B89 . however. but the combined effects of quenching and will circulate around the part. to select the quench variables to obtain the required properties in the gear. material grades and their normally used quenchants. result in less distor- can occur hours or days after quenching. faces. The part design and manufacturing process the quench. Agitation can be provided by propellers or Handbook. For 8620 finer pitched gearing. Gear Materials and Heat Treatment Manual Table 5---5 Commonly Used Quenchants for Ferrous Gear Materials Material Grade Quenchant Remarks 1020 Water or Brine Carburized and quenched with good quench agitation. Smaller sections can be processed in well agitated oil. These are high hardenability steels which can be crack sensitive in moderate to thin sections. 4150 Oil or Polymer If conventional oil is used. 4345 4350 Crack sensitivity applies also to flame or induction hardened parts with high concentration polymer being the usual quenchant. High alloy Ductile or Air irons can be air quenched to moderate hardness levels. air quench can be used for flame hardened parts. Iron Unalloyed or low alloy irons require oil or polymer. 1045 Water. thin sections or sharp corners 4142 can represent a crack hazard. This is the preferred quench. Hot oil should be 4145 considered in these cases. however. Large sections normally require water or low 8630 concentration polymer. Induction or flame hardened parts normally quenched in polymer. ANSI/AGMA 43 2004---B89 . In this section parts and flame or induction hardened surfaces can be crack sensitive. Oil or Type of quenchant depends upon chemistry and section 4130 Polymer size. Oil is sometimes used and air quench can be applied for flame hardening with proper equipment. Gray or Oil. 4140 Oil or Polymer Same as above. Some loss in core 4320 hardness will also result from hot oil quench. Hot oil is often used. With proper equipment. 9310 In larger sections. High concentration polymer should be used with caution. 4118 Oil Carburized and quenched in well agitated conventional 4620 oil at 80---160_F(27---71_C) is normally required. parts are often removed warm 4340 and tempered promptly after quench. Polymer Quench media depends upon alloy content. 3310 Oil Carburized and quenched in hot oil at 275---375_F (135---190_C). hot oil at 275---375_F(135---190_C) 8822 may be used to minimize distortion. conventional oil can be used. 1141 Oil or Polymer Good response in well agitated conventional oil or 1541 polymer. processing techniques should be optimized flame and induction hardening results essentially in to make distortion consistent. rough machining. and a second stress relief (4) Carbon potential of the carburizing atmo- prior to finish machining may all be necessary to keep sphere. (refer to 4. (7) Quenchant type. case depth. Pinions become bowed. skiving. ANSI/AGMA 44 2004---B89 . Gear Materials and Heat Treatment Manual Distortion of quenched and tempered gearing 5. when tooth accuracy requirements dic. distortion. case. amount of chant temperatures than those conventionally used retained austenite. Amount of distortion in.18 mm) per tooth surface or 20 percent of the case compared to profile hardened tooth patterns. such as of agitation. thermal stress ing quenching. tate. controlled and made predictable quenched gears. redesign of only distortion of the teeth because only the teeth are components may be required to reduce distortion. Transformation in the amount of bowing increasing with higher length/di. or greater. used for stress relief. Stress relief temperature is de. and exhibit tortion results from microstructural transformation. (6) Time between quench and temper for richer pendent upon specified hardness and temper resis.1 Carburized Gearing. (1) Geometry. Dis- (b) Side faces become warped. the pinion dimensionally stable during finish ma- chining. uneven (2) Pinions. rough gear blanks (forging. the quench temperature before hardening. mal stress relief prior to finish machining.8. or casting) have sufficient stock provided so distor.8. Surfaces other than the tooth flanks and rizing. NOTE: Direct quenching generally results in 5. Distortion of car- occurs generally as follows: burized gearing makes it one of the least repeatable (1) Gears of surface hardened processes. Exception may be made for tortion is not limited to gear teeth. Dis. alloys. reduces distortion and (8) Resultant metallurgical characteristics of the forms a modified hardened structure at higher quen.3 Surface Hardened Gearing.007 inch more of the tooth cross section is hardened. At times. straightening. heated and quenched. growth. required.8. barstock. depth. and residual stress include: Normally. (2) Hardenability (carbon and alloy content) of tion can be accommodated by machining. This stress is balanced by corre- of bowing or radial runout is often confined to jour. Close control is. Higher hardenability increases ratio pinions may require straightening and a ther. Sequence of manufacture is dependent (5) Carburizing temperature and temperature upon design considerations and the temperature prior to quenching. Stock removal by grinding after carburize hard- creases with case pattern depth and increases as ening should be limited to approximately 0. Once a component is designed to minimize dis- Selective surface hardening of gear teeth by tortion.) considerations. austempering of ductile iron. whichever is less. etc. therefore. carbides. roots may tolerate greater stock removal. etc. with the cooling. reheated and must be minimized. In some (3) Fixturing techniques in the furnace and dur- exceptional instances. when coarser pitch gearing with cases 0. nal diameters and shaft extensions for integral shaft Principal variables affecting the amount of pinions. Lack of repeatability (a) Outside and bore diameters grow larger is due to the greater number of variables which affect and go out of round. however.4. growth and distortion. temperature and amount Modified methods of quench hardening. case results in growth which sets up residual surface ameter ratios and smaller journal diameters.3).3. and residual stress (from thermal shock. Distortion less distortion than slow cooled. runout. (0. amount compressive stress. tance of the steel. relief. High L/D the base material. providing gears are properly to minimize costly stock removal (lapping.080 inches (2 mm) the entire gear is heated and quenched as with carbu. sponding residual tensile stress beneath the case. or cooled from the carburizing temperature to grinding). distortion. such as carbon content. Near solid “pancake” gear blanks. (6) Cantilever pinions. distort less. whenever possible. de. or fixtured in the vertical position (axes vertical) to ishing standpoints. wind”). with teeth on the end of the shaft. 90 degrees apart. Gear Materials and Heat Treatment Manual General design considerations of carburized Distortion of carburized gearing also exhibits the fol- gearing related to distortion include the following lowing typical characteristics (refer to Fig 5---5): (refer to Fig 5---4): (1) Reduction in tooth helix angle (“helix un- (1) Larger teeth (lower DP) distort more. face due to increased case depth (carburizing from sion gears. cur due to non---uniform growth of teeth across the face and non---uniform shrinking of the bores. CANTILEVER PINION BLIND ENDED TEETH HIGH L/D RATIO CONCENTRIC BLANKS Fig 5---4 General Design Guidelines for Blanks for Carburized Gearing ANSI/AGMA 45 2004---B89 . gral shaft pinions should. Inte- the adjacent diameter is larger than the root diame. bore clean---up. followed by im- signed with moderate recess on both sides of the web proved quench action for the same reason) may ap- section. (3) Eccentricity (radial run---out) of gears and (5) High length/diameter ratio pinions distort their bores is dependent upon how they are fixtured more. Web support section wind---up” after hardening. smaller face width gears may exhibit “helix should be centrally located. Journals may be required to be masked in or. compensate for reverse crown or are chamfered at (4) Holes in the web section close to the rim. thickness under the rim is recommended to be not (2) End growth on gear teeth at both ends of the less than 40---50 percent of the face width for preci. der to prevent carburizing and then be finish ma- chined after hardening with sufficient stock for (4) Taper across the face (tapered teeth). The recess is provided to enable pear as reverse tooth crowning on narrow face gear- clean---up grinding of the rim and hub end faces after ing. Teeth on larger diame- (3) Radial web support section under the rim ter. Teeth are often crown cut prior to hardening to hardening. and “blind ended” teeth on pinions. cause collapsing of the rim section over the holes. two directions. where (5) Bowing of the integral shaft pinions. which often requires an increased helix angle (2) Rim thickness should be the same at both end to be machined into the element prior to carburizing faces. Teeth may also be both crown cut reduce the weight or provide holes for lifting. (more prevalent in pinions). to the ends of teeth. in the furnace. present problems from both distortion and fin. minimize bowing. Masking can also be used for ease of taper and “hour---glassing” of the gear bore can oc- straightening. may and chamfered. be hung ter. CAUTION: Deep spin hardening of gear ening. as with burizing.3.3 Nitrided Gearing. etc. Larger ring gears are positioned horizontally across the face dependent upon the heat pattern. However. involves more manual set---up factors. Gear Materials and Heat Treatment Manual STRAIGHT HELICAL UNWIND TAPER HOURGLASSING END GROWTH BOWING (REVERSE CROWN) ECCENTRICITY Fig 5---5 Typical Distortion Characteristics of Carburized Gearing Gears may be fixtured vertically through the (2) Increased growth of the teeth (greater than bores or web holes on a support rod (axes horizon. Parts are also flame and spin induction hardening generally pro. Distortion increases as a temper heat treatment.8. the roots of the teeth because of residual tensile flame.3. spin flame hardening. Spin flame hardening teeth are heated and subsequently quenched. carburized pinions. as occurs during car- (1) Helical unwinding of the gear teeth. and are not quenched. nitrided gear teeth are not generally required to be ANSI/AGMA 46 2004---B89 . ing. spin flame hardening can be engineered with special ods. for carburized gearing) because the entire tooth tal). it is not 5. (4) Taper of teeth due to varied heat pattern and Thin section gears. and induction hardening. teeth may cause excessive tooth growth and ened to the specified depth below the roots of teeth. For high bending strength applications. to minimize distortion. During both spin flame and spin induction hard. compared to carburize. and enable subsequent machining. flame heads and fixtures for required control. such as bevel ring gears. Nitriding of gearing desirable to have the hardening pattern terminate in results in less distortion. is greater cross---section of a tooth is hardened. Con. depending on size and face (3) Crowning or reverse crowning of the teeth width. be press quenched to minimize distortion. the entire tooth cross section is often hard. which include tour induction hardening of tooth profiles produce positioning of the flame. or fixtured horizontally (individually or stacked) cross section may be hardened in finer pitch gearing. gas flows. because of fewer human error Flame and induction hardened gearing generally dis. Therefore. Bores Crowning is more desirable from a tooth loading and web sections can be masked to prevent carburiz. less distortion and growth than spin hardening meth.2 Flame and Induction Hardened Gearing. factors involved during machine and inductor set--- tort less than carburized gearing because only the ups with induction hardening. standpoint. Distortion of the teeth from spin induction hard- ening is often considered more repeatable than with 5. may affect bore size. Spin done before machining and nitriding. Prior quench and stress considerations. which results in distortion. flame or induction hardening. with sufficient stock for clean---up of the teeth. may case depth across the face.8. not heated above the transformation temperature or duce the following distortion characteristics: previous tempering temperature of the steel during nitriding. saturation of the Almen strip.0. although centrifugal 5.001 inch (0. A. achieve more uniform intensity along the and separated to restore size and shape integrity as toothform.4 mm) respectively. hardened and tempered to 40---50 at the surface. Coverage refers to wheel equipment is often used for very high volume the percentage of indentation that occurs on the sur- production.051 inch (1. the strip will bow convexly on size may shrink up to 0. but Whenever a processing procedure is developed quantitative data to substantiate this condition is for a new part. face of the part. Figure 5---6 also shows the dimensions cent. which are cleaning operations.025 mm).0015 inch (0. Flatness tolerance is + --.04 mm) depend. should be provided. at in- strength. 0. This energy controls the depth of the peen- 50_F(28_C) below the prior tempering temperature ing effect. which have thicknesses of 0. Strips are SAE 1070 cold layer of high magnitude residual compressive stress rolled spring steel. hard- to relieve rough machining residual stress prior to ened steel strip called an Almen Strip.031 process performed by bombarding the surface of a inch (0. Because it is difficult to sional tolerance requirements. One hundred percent coverage is de- ANSI/AGMA 47 2004---B89 .9. This stress may improve the bending HRC. It is becoming an accepted practice to specify shot peening on carburized and other heat treated for the Almen strips and holding fixture.2 Shot Control. Because the process increases bending fatigue determination must be made at the beginning. There are three classifications of Almen 5. 5. in inches with a gauge and is called the arc height (see Fig 5---6).9.9. The strip is held flat on an Almen block placed in the representative During nitriding.013---0. the shot should be classified therefore. the particles can cause surface damage. Contact fatigue strength may also be each production run. en the time to reach a specified peening intensity. and C. nozzle riodic inspection of the shot is required to control type equipment is generally preferred because of the shot size and shape within specification limits. location during the peening operation. gearing can kinetic energy with which the peening media strikes be rough machined and stress relieved at the part. 5. Bearing diameters of directly measure the effects of shot peening on a shaft extensions are often ground after nitriding with part.0015 inch fatigue strength of a gear tooth as much as 25 per- + ( --. outer surfaces grow approxi. an intensity curve must be developed limited.2. for high performance gearing. When ability to vary the angle of shot impingement and. Shot peening is a cold working Strips.0005---0. Mechanical means for moving the more than a 10 percent increase in arc height. it may be used either to salvage or upgrade tervals of no more than four hours and at the end of a gear design.2. these limits are reached.9 Shot Peening.3 Coverage Control. as a result gear must be rotated on its axis while exposed to the of lower mass. masked for subsequent machining. It is measured by shot peening a flat. N. Bores leased from the block. Pe- For optimization of shot peening of gears. Saturation is defined as that point at propelling shot by air pressure or centrifugal force which doubling the time of exposure will result in no against the work. a high degree of process control is essential to only minimum stock provided. work through the shot stream by either translation or rotation. the peened surface. This is accomplished by shot peening several strips at various times of ex- 5.8 mm).3 mm) and 0. cess. Machinery used for shot posure to the shot stream and plotting the resulting peening should be automatic and provide means for arc heights.2. or both.1 Intensity Control. Shot peening should not be confused with which establishes the time required to reach peening grit and shot blasting.1 Equipment. This type of equipment is generally used shown in MIL---S---13165B.0938 part with small spherical media which results in a thin inch(2. An intensity gears. These fragmented Regardless of the type of equipment used. fragmented shot particles will length- shot stream.9. Gear Materials and Heat Treatment Manual ground or lapped after hardening to meet dimen.9. Intensity refers to the When close tolerances are required. When re- mately 0. improved in some instances by shot peening. Machinery 5.04mm).2 Process Control. Also. manner as the part will be peened. to minimize the number of fragmented particles caused by fracturing of the shot. in the same finish machining and nitriding. The amount of bow is measured ing upon size. Surfaces can also be assure repeatability.0. Shot size and shape must must be capable of consistently reproducing the shot be carefully controlled during the shot peening pro- peening intensity and coverage required. Shot types avail. monly referenced shot peening specification is Coverage must be related to the part. the harder shot glass bead. and 55---62 HRC. not the Al. conditioned cut wire (CW).32 (102 to 152 mm) SCREWS ALMEN TEST STRIP HARDENED BALL SUPPORTS 0.4mm) 0. The time re. The peening time required to obtain 100 Manual on Shot Peening.3. full 5.3. The actual part must be examined for ment requirements. 3.001 in (0. and ceramic.031 + + ---0.30 0. in a shot peening specification.0 mm) SHOT STREAM MEASURING DIAL 4 to 6 in 10--. dye in a scanning process.750 in (18. The SAE peened. percent coverage should be recorded.1 Governing Process Specification. A com- peened part.79 0. and quality control complete coverage in all areas specified to be shot requirements for effective shot peening. 45---55 HRC.2 Shot Size and Type.015 in (76+--. selection depends upon the material.001 in (2.02mm) --- 0.).5 in (38.051 + + ---0.0 in 3. A mini. equip- men strip. SAE---J808a---SAE HS84.02mm) --- A STRIP PEENING NOZZLE C STRIP ALMEN STRIPS 0. hardness.75 in (19.9. Gear Materials and Heat Treatment Manual fined as uniform dimpling of the original part surface quired to obtain multiples of 100 percent coverage is as determined by either visual examination using a that multiple times the time to reach 100 percent cov- 10X magnifying glass or by using a fluorescent tracer erage (200 percent. higher in hardness than 50 HRC. The following sec- coverage has been achieved when no traces of the dye tions describe items that the designer should include remain when viewed under ultraviolet light.0938 + + ---0. RESIDUAL STRIP MOUNTED FOR PEENING TEST STRESSES INDUCE ARCHING HEIGHT MEASUREMENT (a) (b) (c) Fig 5---6 Shot Peening Intensity Control 5.0 + ---0.0 in ARC HEIGHT (76 mm) (76 mm) 1. Most shot peening of fer- ANSI/AGMA 48 2004---B89 . may also be used.38 0.001 in (1. and Cast steel shot is available in two hardness ranges: geometry of the part to be peened.9.0. In the latter process.9 to 19.0 mm) 3. etc. mum of 100 percent coverage is required on any shot 5.1mm) 0. Shot type and size rous materials is accomplished with cast steel shot.02mm) --- N STRIP 0. When peening gears able are cast steel (S).75 in (19. 300 percent.745 to 0. MIL---S---13165B which identifies materials. procedures.9.0 mm) HOLDING FIXTURE STRIP REMOVED.3 Design Consideration. 012 0.4 Coverage. Gear Materials and Heat Treatment Manual should be specified to achieve higher magnitudes of 5.3. with masked area toler- The range of arc height is generally 0.010---0. 100 percent minimum tion is “100 percent minimum coverage. mm) wide.004 0. Mask area(s) indicated (if necessary).50 --.008 0. C. but it can be specified to a closer tolerance 5. A typical statement in a blueprint specifica. it is desirable to mask compressive stress (refer to Fig 5---7).9. Other tempt to achieve more blending of a poorly machined areas optional. A typical example of for more repeatable results. 0 0 HRC 46 SHOT --.9. Shot peen area(s) indicated with S170 cast steel 5. surface.3.004 inch (0. desirable to specify multiples of 100 percent in an at.9.016 DEPTH IN INCHES Fig 5---7 Residual Stress by Peening 1045 Steel at 62 HRC with 330 Shot ANSI/AGMA 49 2004---B89 . it may be MIL---S---13165B. finished machined areas of the part from shot im- pingement. Figure 5---8 illustrates drawing or blueprint specification for shot peening the depth of the compressive layer on steel at 31 and would be as follows: 52 HRC hardness according to intensity.3.500 ---100 ---1000 ---150 HRC 61 SHOT ---200 ---1500 ---250 0 0.9. Use 55---62 HRC shot. this depth of the compressive layer and must be specified should be stated in the shot peening requirements as the arc height on the A. If masking is required.3 Intensity.6 Drawing Example.” coverage. At times. The intensity governs the bores or bearing surfaces.10 ances given. or N strip (see 5.9.5 Masking. In most cases.3.2. In some instances.1). 100 percent shot to an intensity of 0.014A per coverage is adequate. and defined on the drawing. Typical masked areas would be finished 5. 0.16 S110 0.020 . Additional com.040 1. Currently this must be measured should be considered typical and not manda. 0.025 A Fig 5---8 Depth of Compressive Stress Versus Almen Intensity for Steel Table 5---6 gives shot size and intensity for vari. or pol- 2 1/2 --. it is desirable to achieve an intensi- 5.2 S330 0. if material removal is limited to 10 percent of 1 3/4 --. Diametral Shot Size Intensity (3) Generally all machining of areas to be Pitch peened are complete prior to shot peening.018A ishing. Portable units are under development. mark.020 .006 --.010C INTENSITY 0 . hard. unit.002 . 0. Variables such as gear geometry.9. It is pos- sible to restore surface finish in peened areas (and 8 --. honing. shot diameter should not exceed 50 spections should be performed before shot peening.008 .014 --. ty sufficient to produce a depth of compressive stress ments for shot peening include the following: to negate the stress riser effect of the machining (1) All magnetic particle or dye penetrant in.25 . (5) When there are significant machining marks in the tooth roots. 0.005 .010 . percent of the fillet radius.006 --.7 General Comments.008C (4) Compressive residual stress levels produced by shot peening can be quantitatively measured by NOTE: The values for shot size and intensity X---ray diffraction.010A 4 --.75 .005 0 0 0 .025 .010 .004 .50 HRC 52 .0 HRC 31 .015 .3.035 . ness. ANSI/AGMA 50 2004---B89 .016 --.020A the depth of compressive layer. 3/4 --.1 S550 0.006 . and surface condition in the root may make other specifications more desirable.015 .3 1/2 S230 0. Gear Materials and Heat Treatment Manual . will tend to obscure minute cracks. Table 5---6 (2) All heat treating operations must be per- formed prior to shot peening as high temperatures Typical Shot Size and Intensity for Shot [over 450_F(232_C)] will thermally stress relieve the Peening peening effects. 0. The plastic flow of the surface as a result of peening ous diametral pitches.010 --.7 S170 0.014A retain beneficial effects) by lapping. on a cut sample in a laboratory X---ray diffraction tory.030 . However. face chemistry (such as by nitriding). while the center will ting and surface bending fatigue resistance.1 Mechanically Induced Residual Stresses. will serve as a good example of these 5. although quite dif. When the sum of these two variables is face of the gear which can adversely affect perfor. Residual stresses play induced. CBN grinding may also induce surface tem. Under extreme grinding conditions. Gear Materials and Heat Treatment Manual 5. Lapping. The most common type of ing). heat treatment must be light enough so as not to create significant residual stresses. machining stresses and finishing operation turn creates a compressive stress at the center. particularly fast or unfavorable) are induced mechanically. skiving) will need to be individu. quenching to form martensite. The thermal contraction termediate stress relief heat treatments in order to exceeds the expansion of the transformation to mar- prevent significant distortion during the final heat tensite. ual stress because modification of surface chemistry pering residual tensile stresses. can affect the degree of in---process distortion residual stress pattern in small diameter bars is a ten- and the residual stress state present in the finished sile stress at the surface and a compressive stress at parts.2 Residual Stresses by Modification of have a favorable effect on the residual stresses in the Surface Chemistry. thermally. setting up residual tensile stress at the center treatment.10 Residual Stress Effects. types of residual stresses. and heating can introduce thermal ishing methods (e. the ther- also impart beneficial compressive residual stresses mal contraction can not overcome the expansion when properly controlled.1 Thermal and Phase Transformation much of the distortion that occurs during manufac- Stresses. In quenched carburized The other types of residual stress. with residual tensile stress at the center and residual pressive residual stresses. ing and heat treating operations are responsible for 5. one type of gears can determine whether or not the gears will thermal stress. can all be categorized as being metallurgically to martensite in the core occurs at a much higher ANSI/AGMA 51 2004---B89 . This in stresses.10. Machining stresses are created by the cut. cation of surface chemistry stresses result from heat mance of gears. two types of residual stress patterns can form on singularly and in combination (such as by carburiz- quenching of a round bar. Each of these. extended period of time. Quenching. and hobbing minimized by in. rizing. the most common type of surface chemistry modification. large. Other hard gear fin. Thermal stresses result from the heating ture. size of the bar and speed of since it can create residual tensile stresses in the sur. face of a bar cooling faster than the center. from the martensitic formation and residual tensile cally performed on finished gears to improve the pit. When the cooling as shot peening (refer to 5. the stress pattern will be of the second type after final heat treatment maintains beneficial com. Finishing operations such compressive stress at the surface. Residual stresses created by machin. can also be considered a phase trans- survive in service. stress will form at the surface. In this situation.2 Metallurgically Induced Residual Stress. The phase 5. for example large diameter bar with a fast mance. The following sections briefly discuss the the center. This type of residual stress must finished gear. Parts given a final heat treatment after bars. generates both ther- by phase transformation. Thermal. phase transformation and modifi- an important role in the manufacture and perfor.10. turning. the transformation temperature of austenite ferent.9) and roller burnishing rates of the surface and center are similar. consist of residual compressive stress. The second and opposite type of residual stress ting of the gear shape and can be either beneficial or pattern occurs during quenching of large diameter detrimental. These two types of stress patterns are deter- nal heat treatment must be performed very carefully mined by two variables.10. Residual stresses (either favorable formation stress. treatment of steel.2.2. honing or careful grinding of gears quench. which must be taken into account. stresses.10. or by modification of sur- mal and phase transformation stresses. also be considered in conjunction with thermal resid- however.g. Grinding after fi. the quench. Machining cuts taken just prior to final and residual compressive stress at the surface. The residual stress distribution in finished and cooling of materials. Use of cubic boron nitride (CBN) grinding may 5. These operations are typi. the surface hardens but the finish machining may have the gross residual stresses center remains at an elevated temperature for some from milling. Quenching. transformation to martensite creates volume expan- There are two types of mechanically induced residual sion producing tensile stress at the surface. steels. Carbu- ally evaluated as to effect on residual stress levels. For example. This stress pattern results from the sur- causes of each type of induced residual stress. requires heating. stresses. They help counteract tensile cepted method of control.2 Incoming Material Hardness Tests. two tests cost for ferrous materials: shall be on the cope side. (two over risers Iron casting grades are identified by their me- approximately 180 degrees apart. must be made with calibrated instruments with Compressive stresses in the case help reduce surface data substantiated and documented to insure reli- pitting caused by tooth contact stress above and be. (one over a riser and the other approximately 180 degree away between ris- (1) Spectrographic Analysis ers) and the other two tests shall be on the drag side (2) X---Ray Analysis 90 degrees away from the tests on the cope side. eight tests shall be on the drag side equally spaced cepted for analysis certification. and elongation. Material each segment per agreement between the customer hardness tests. Hardness tests are made Metallurgical information should be available on the rim edge at mid rim thickness after final heat regarding: treatment. often specified in accordance with and supplier.40 (1020) 2 (7) test coupon considerations Over 40 _ 80 (1020 to 2030) 4 Over 80 _ 120 (2030 to 3050) 8 Refer to Appendix D on Service Life Consider. Gear Materials and Heat Treatment Manual temperature than the case. four between risers around the gear). using any method or instru- parting beneficial compressive stresses in the case. and the other NOTE: Source certification is commonly ac. ability. two between risers chanical properties such as tensile strength. Recommended number of (2) incoming material hardness and hardness tests are as follows: mechanical tests (3) heat treat process control Outside Number of Tests Diameter. Material be on the cope side. Metallurgical Quality Control gear blanks is generally based on the outside diame- ter and increases with size. When two hardness tests are specified. yield also approximately 180 degrees apart. ANSI/AGMA 52 2004---B89 . Hardness may be specified away from tests over the risers) and the other four but cannot be used to identify grade. preferably over a riser. and as discussed in the ASTM A370. the austenite to martensite trans. Therefore. around the gear. using chemical analysis and hardness tests. made using: formation creates a volume expansion. destructive process. Statistical process control (SPC) is an ac- low the pitchline. The following types of tests are commonly used and are listed in ascending order of When four hardness tests are specified. (1) Rockwell as the part is cooling. tests shall also be on the drag side. Hardness testing. Over 120 (3050) 16 ations. four tests shall be on the cope side. the other grade is certified by chemical test. are normally surface hardness tests previous section.2. approximately 180_ away. ment. Minimum number of hardness tests on both rim or edge faces of through hardened cast and forged 6. Generally this is a on the drag side. (1) incoming material grade information 6. transformation begins in the (2) Brinell core and moves outward toward the case setting up (3) Rebound Tests (Equotip & Shore) tensile stresses in the core. The expansion of the case is opposed by the previously transformed core im. When sixteen hardness tests are specified. 90 degrees strength. stresses caused by bending in the root. 90 degrees Bronze material grades are normally qualified apart.1 Incoming Material Quality Control. Large segmented gears shall be hardness inspected on the cope and drag rim edge of 6. (3) Atomic Absorption (4) Wet Chemistry When eight hardness tests are specified. eight Brass material grades are identified by chemical tests shall be on the cope side (four over risers and analysis. Recommended (4) part characteristics inches (mm) (Rim Face) (5) metallurgical testing (final product) (6) microstructure 0 --.1 Cast Gears. one shall 6. (1) A minimum of four hardness tests shall be taken on the major (tooth) diameter of forgings up to (4) When a total of eight hardness tests are speci- fifteen inches. they shall be made 90 degrees apart on each shall be taken at the center of the length of the major rim edge. they all shall be made 180 degrees apart on the heat treatment of gear materials are as follows: ANSI/AGMA 53 2004---B89 . 180 degrees quently impact testing. forging. condition of process Over 80 to 120 6 (120_ apart) equipment. One 6.2 Disc Shape Forging. evaluation techniques. Forged pinions each ring edge. A291 and A148.3 Incoming Material Mechanical Tests.2 Forged Pinions and Gears. 180 degrees apart. shown in Tables 4---2. (38 ¢ 127 ¢ 152 mm) long.5 ¢ 5 ¢ 6. Number of Tests 6. fied. forgings and bar stock are normally obtained from a grees apart. and any cosmetic change. Mechani- reading shall be taken approximately 1 inch (25 mm) cal property test bars. shall be taken at the Test bar stock should remain attached to or ac- mid radius on forgings over 18. (3) When a total of six hardness tests are speci- 6. Test bar stock for gearing manufactured from ches (380 mm) in diameter. are characteristics of a specific the ring edge and the other on the opposite ring edge. diameter (center of tooth section at mid face).2. fied. shall be taken at the drag (bottom) rim edge of the casting or are cast the mid radius on forgings of up to 18. 180 degrees apart. One reading shall be taken approximately component and the direction of metal flow during 2 inches (50 mm) from each end of the major diame. two on each side 180 degrees apart. Test bar stock. in the of the major diameter (center of the tooth section at axial or longitudinal direction with respect to the mid face).0 inches (457 mm) in company the rough stock until all thermal treatment diameter. 6.3 Forged Rings (Reference ASTM A290). shall be taken at the center of the length prolongation or extension of the rough stock. 6.2. Refer to 6. 180 de. rate of heating and cool- Over 40 to 80 4 (180_ apart) ing. (2)A minimum of four hardness tests. disc shapes and the other. and part geome- (2032 to 3048) try. fied. process control.8 for merits and limitations of me- (2) A minimum of five hardness tests shall be chanical test bars. one on or surface texture. certification of forged gearing. Gear Materials and Heat Treatment Manual 6. 4---3 and 4---7. Refer to ASTM A291 for mechanical test ter. Over 120 8 (90_ apart) Heat treat processes change the microstructure (3048) and mechanical properties of the gear material. temperature. cooling media. are normally attached to grees apart with one on each side. Refer to ASTM A148 for mechanical test certifica- tion of cast gearing. growth. are only required when speci- apart. Diameter of Ring. Minimum tensile properties for steel gearing are Recommended number of hardness tests is as fol.2. (1016 to 2032) base material composition.1 Cylindrical Shaped Forgings.0 inches (457 as separate test blocks from the same heat of steel. and also in lows: ASTM A290.2. approximately 1. inclusive. Process parameters used to control fied. mm) in diameter.0 inch (1) A minimum of two hardness tests. they shall be 120 degrees apart on each rim edge. for tensile testing and less fre- from each end of the major diameter.4 Heat Treat Process Control. Process variables in- (1016) clude: time. 120 de. is completed. The many variables in (mm) Recommended involved in the heat treatment of gear materials Up to 40 2 (180_ apart) makes process control complex. Three readings. taken on the major diameter of forgings over 15 in. Any dimensional change. types of controls. Two readings. rings. such as coloration fied.2. such as distortion or part (1) When a total of two hardness tests are speci. but are not primary factors for (2) When a total of four hardness tests are speci.2. 90 degrees apart from one edge to and gears include cylindrical shapes. heating media. heat treat process. they shall be made 180 degrees apart. The duration of each segment of the gen concentration is measured with an oxygen probe heat treat process is critical to achieving the desired positioned in the furnace heat chamber.4. It is easier and more nace atmosphere is critical to carburizing and the cost effective to retemper a part that is too hard.4. suring that the quenchant stays at the proper temper- perature. the centrations of carbon dioxide and carbon monoxide uniformity of the temperature within the working di. There are several methods available to monitor ing is generally 0. that the tempering temperature be controlled to 6. The concentration of This is usually accomplished with strip chart record. For example. in a furnace atmosphere at a given temperature are mensions of the furnace equipment should be mea.4 mm) of sec. the part in the chamber may not be up to tem. and en- heat. cell or dew pointer. side of the tempering range. Time at temperature for through harden. These include the standard nickel ball test. If a steel gear is cooled too quickly. ature (refer to 5. the core ma- on quenching). perature long enough for the entire part to be at tem- perature. The rates of heating and cooling are parts or test coupons can also be used as long as the important considerations.4. tion during the hardening process.1. Since the properties obtained in gear materials are dependent (2) Carbon Dioxide Concentration. The con- on the temperatures at which they are treated. Hardness and mechanical prop. concentration in the furnace atmosphere at a given temperature and carbon monoxide level. magnetic test. For example. the rate of diffusion into steel is dependent on tem. it will have 6.75 hour per inch (25. related to the carbon concentration on the surface of sured.6 Tempering Temperatures.4. The amount of variation allowed is depen. ling carbon potential in a furnace atmosphere: ment of gear materials.4. It is advisable to make as a percentage. centration (if applicable) of the quenchant. material properties.4.1 Temperature Uniformity.4 Atmosphere Control.2 Thermal History.5 Part Characteristics. the carbon concentration on the sur- atmosphere is also temperature dependent. cess. reharden and retemper a soft part. centration (dew point) in a furnace atmosphere. The ous grades of steel.2 Time. operation involves monitoring the variables which ature. the depth of car- bon penetration during carburizing is dependent on 6.4.7 tion hardened part is heated too slowly. Gear Materials and Heat Treatment Manual 6. an initial tempering temperature which is on the low cess control. For a given perature. (1) Water Vapor Concentration.1. and quantify the cooling rate of the quenching pro- tion. In carburizing and nitriding. carbon on the part surface is related to the oxygen ers. cleanliness and con- When the furnace temperature instrument indi.5 Quench Control. Specific face of the part is related to the water vapor con- temperature ranges are required to harden the vari. It is important that the part be held at tem. hot wire test and interval test. dent on the type of heat treatment and the material The carbon dioxide concentration is measured properties desired. The carbon concentration in the furnace temperature. if an induc- test piece hardenability is accounted for (refer to 5. There are three 6. Temperature selection and commonly used methods for measuring and control- control is an important parameter in the heat treat. The composition of achieve the desired hardness. with an external infrared gas analyzer and expressed 6. It is prudent to select the furnace atmosphere is an important part of pro. the part.7). (3) Oxygen Concentration. Control of carbon potential in the fur. the prop- cates that the furnace chamber has recovered its er operation of any device used for agitation.4.3 Rate. ANSI/AGMA 54 2004---B89 . expressed as the atmosphere dew point measured in degrees fahrenheit.1 Temperature. affect the rate and uniformity of part cooling. 6. terial will get too hot and lose its mechanical proper- ties. water vapor concentration is measured using a dew erties of a material grade are dependent on the tem. The water vapor concentration is pering temperature after hardening. It is important high internal stresses and possibly crack. Control of the quenching how long the part was held at the carburizing temper. The oxy- 6. than protection of surfaces from carbon pickup or deple. a time temperature plot of the heat treat processes as a monitoring device and as process documentation. Sample 6. This in- cludes inspecting the condition. 1 Tempered Martensite. If the results from one or more of many factors such as de. It is recommended until the hardness indentation is removed. Low as quenched hardness usually 6. or low surface carbon. has been correctly hardened and tempered. If the part However. quate quenching.2. 6.1. and then that a trained metallographer or metallurgist per- make another hardness measurement near the origi. inade- its own application limits and must be used correctly. crostructure will be composed primarily of tempered mine the depth of decarburization. that the hardness below the decarburized zone meets blue print requirements. part has an excessively high carbon concentration.2. this 6.4 Undissolved Carbides. micro--. If a surface has been surface hardness improves after freezing.1 As Quenched Hardness. a test coupon or martensite provided that the hardenability of the part that was run with the load should be sectioned. If the part hardness testing devices which can be used. mounted.1. All carburized case mainly type of steel and as quenched hardness.6). Retained austenite can be transformed to martensite by freezing the carburized part. method to insure reliability using hardness testing.2 Decarburization. specified range between pieces in a furnace load. ANSI/AGMA 55 2004---B89 . 6.5. As quenched case depth is typically measured by making a micro- hardness of a part is a good indicator of the heat treat hardness traverse across a sectioned part or test cou- process. that in most cases decarburization is not 6. too high tempering temperature.5.2. burized case. pearance if severely under quenched. malfunctioning quench agita.5. Carburized 6.3 Post Temper Hardness Examination. If a gear has been improperly permissible. If the 6.6 Retained Austenite Examination.2 Bainite. or a darker Tempering parts reduces hardness. tained austenite is characterized by a white back- ficient soak time. the mi- creases.5. surface hardness of a carburized part is low. or too low an austenitizing temperature. Re- metal is removed. A microstructures will contain some retained auste- hardness measurement technique can be used to nite. 6. un- Statistical process control (SPC) is an accepted dissolved carbides. The composition of the should be made using the following sequence: grind various phases in the microstructure of a gear will tell surface for hardness measurement. it is advisable that two hardness indicator of high surface carbon concentration or too checks be made on a qualifying test part to insure high of a quench temperature. polished and etched.1 Hardness. there was decarburized. which is characterized by a feathery ap- 6. There are numerous types of hardness part was satisfactorily quenched.5.1. it may be teriorating quenchant. are used to monitor the carburizing process. or if the hardness increases as surface will be present and will reduce the case hardness. If the hardness in.5. but each type has is low. Hardness is the most common core hardness of a part is within the expected range characteristic used to measure results of the heat regardless of the other hardness measurements. the microstructure might be interspersed with bainite. monitor furnace soak time and uniformity. there is possible decarburization. It should be noted.5. due to the presence of retained austenite in the car- tors.5. If a hardened gear there is no decarburization. Surface hardness and core hardness measurements able information.5 Case Depth Examination. if the carbon content of the carburized hardness is greater in a heavy section compared to a case is high.1. nite. If both measurements are the same.1.4 Carburize and Harden Examination. quenched.5. Many factors determine the as quenched pon to find the depth from the surface where the hardness such as decarburization and retained auste- hardness is equivalent to Rockwell C 50. structure and test coupon results can provide valu.1. High as quenched hardness is the result of good heat treatment. Gear Materials and Heat Treatment Manual Part characteristics such as hardness. this is an indication of decarburization. a larger percentage of retained austenite light section. If the 6.5. If the part hardness varies from the ground in a matrix of other structures (see 6. temperature increases.5. As tempering acicular pattern for marginal quenching.5. 6. the treat process. Temper- ing temperature is determined by many factors. inadequate case depth.2 Microstructure. hardness will be low. To deter. form the microstructure analysis. hardness decreases. steel was adequate. If a carburized is a good indication of a processing problem.5. If the surface retained austenite in the carburized case which is an hardness is low. The two hardness checks 6. regrind surface a lot about the heat treat process. excessive retained austenite.2.1. usually less than 5 to 30 percent by volume. however. nal location.3 Retained Austenite. these are good indicators of insuf. generally 64 microin- structure will consist of light. Mechanical and Non--. the test speci. used to hardness inspect surface hardened gearing old to the upper threshold is approximately 100 to 1 when size of the gearing permits and where a visible wide. This can be done by and the unknown workpiece with a hardened ball be- running the test at some overload ratio and evaluat. Gear Materials and Heat Treatment Manual the microstructure will contain undissolved carbides table Brinell and Rockwell test machines provided usually populating the case. ness testers can be improved when the instrument Through hardened finish machine gearing can be can be fixed for perpendicularity to the test surface. while a structure of excessively high carbon concentration will have carbides contained in a net. surface temper hardness at these locations. In low cycle fa. Tests and inspections of teeth or in root radii because hardenability of the which may be made on the final or near final product steel selected should insure obtaining the specified are fatigue testing. it is necessary for about half the test units to those tempered to lower hardness than 60---64 HRC. where size permits. This would constitute a Miner’s scratch test (Reference SAE J---864). top lands of teeth and hardness testing of test coupons can be corre.2 Hardness Testing on the Gear Product. Comparison is made of ing the damage with time for the test conditions. tigue where most high overload and damage frac. so as not to equals the damage value of the design. or: lar carbide network is not desirable for gearing. Hardness measurement in the roots of teeth may not ANSI/AGMA 56 2004---B89 . Other portable instruments measure design conditions.Destruc- gearing is rarely inspected for hardness on the flanks tive Tests and Inspections. to simultaneously impact a known hardness test bar taining validity of the test data. non---destructively. the hardness on the flanks of surface hardened coarse gearing with non---destructive portable hard- 6. available (ASTM A833). One tester uses a hammer It is desirable to expedite this testing while main. tive geometry are frequently used for destructive Through hardened gearing is commonly in- testing in lieu of destroying gearing. (2) If the size of the hardness impression on the work at the grain boundary. conventionally hardness tested by standard and por. hardness testing. test surface is permitted. and ultra- are not available for accurate measurement at roots sonic inspection. This comparison must be made the recoil or rebound height or velocity of a dropped for both the beam strength and the surface durability hardened ball. leave an objectionable impression. When hardness testers inspection. load. of teeth. Portable testers men survived the minimum specified product life. Hardened files. Miner’s Rule is a widely accepted meth.6.6. the final product is the proof of the suitability of the Other portable hardness testing instruments are design for the intended purpose. Conventional Rockwell test machines can be tures occur. may be used. including function. od of making these comparisons.3 Test Coupons. scattered pinpoint car. Fatigue (life) testing of quired. tivated indenter to measure hardness. destructive sectioning and testing may be re- 6. ches (5 microns). or: bides.6 Metallurgical. or use a high ultrasonic frequency ac- of the teeth. Undissolved carbides that the following are met: are characterized by blocky white regions in a matrix (1) Surface to be inspected provides access and of martensite and retained austenite. Since the distribution may be considered a log impression is permitted. A normal has the required surface finish. Continuous intergranu. which measure the rebound height or velocity of a Due to the statistical nature of fatigue failure dropped hardened ball or use a high ultrasonic fre- there is a wide distribution of data.5. quency activated hardness indenter. this scatter band from the lower thresh. gap of herringbone (double heli- lated to gearing characteristics. cal) gearing and on adjacent diameters of pinions other than bearing journals. the ball diameter on each to determine hardness of Damage can be compared with that for the product the unknown. Inspection of Rule damage of ten. (3) Mass of the test surface will support the test 6. magnetic particle inspection. run at ten times the threshold life to validate the can also be used to approximate hardness by the product design. Test coupons of representa. tween the two test surfaces. Through hardened 6.1 Fatigue Testing. It is desired that surface hardened gearing be When damage value accumulated on the test hardness inspected. Microstructure spected on the faces of gear rims. Gear Materials and Heat Treatment Manual be reliable due to accessibility in the radius of curva- be used in some instances. Caution should be exer- ture and surface roughness. cised if the heavier load C scale is used. For improved accuracy and where permitted, through hardened steel and cast iron gearing should 6.6.4 Magnetic Particle Inspection. Magnetic be hardness inspected directly in Brinell (not con- particle inspection is a non---destructive testing verted). Hardness of surface hardened gearing method for locating surface and near surface discon- should be directly measured in Rockwell (C or A tinuities in ferromagnetic material. When a magnet- scale) or converted to Rockwell with suitable porta- ic field is introduced into the part, discontinuities ble instruments. laying approximately transverse to the magnetic field will cause a leakage field. Finely divided ferromag- Portable instruments vary in accuracy and reli- netic particles, dry or in an oil base or water base sus- ability. Users, therefore, should take precautions to pension, are applied over the surface of the material insure accurate calibration and test results. under test. These particles will gather and hold at the Hardness testing equipment manufacturers leakage field making the discontinuities visible to the should be contacted and literature searched for addi- naked eye. tional information on principles of hardness inspec- tion, available test equipment and their capabilities. Use of electric current is, by far, the best means Statistical process control is a useful tool to be used for magnetizing parts for magnetic particle inspec- with hardness testing. tion. Either longitudinal or circular fields may be introduced into parts. There are basically two types 6.6.3 Surface Temper Inspection. Surface tem- of electric current in common use, and both are suit- per inspection is used to detect and classify localized able for magnetizing purposes in magnetic particle overheating on ground surfaces by use of a chemical testing. The two types of current are direct current etch method. Details of the process are covered in and alternating current. The magnetic fields pro- AGMA 230.01, Surface Temper Inspection Process. duced by direct and by alternating currents differ in Inspection criteria includes a class designation many characteristics. The main difference, which is for critical and non---critical areas. To evaluate the of prime importance in magnetic particle testing, is severity of surface temper, grinding burns are classi- that fields produced by direct current generally pene- fied by intensity of color from light gray to brown to trate the entire cross section of the part, whereas the black. Severe burning or re---hardening is indicated fields produced by alternating current are confined by patches of white in the darkened areas. Cracking to the metal at or near the surface of the part under may also be present. Re---hardening or cracking are test. From this, it is evident that when deep penetra- cause for rejection. tion of field into the part is required, direct current must be used as the source of magnetizing force. By Tables I and II in AGMA 230.01 cover temper far, the most satisfactory source of D.C. is the rectifi- classes ranging from Class A (Light temper) to Class cation of alternating current. Both single phase and D (Heavy temper). Class C (Moderate temper) for a three phase A.C. are furnished commercially. By the limited area and hardness reduction may be per- use of rectifiers, reversing A.C. is rectified and the mitted. delivered direct current is entirely the equivalent of straight D.C. for magnetic particle testing purposes. Rework for excessive temper is generally per- mitted by mutual agreement between customer and Sources of alternating current are single phase supplier. stepped down to 115, 230, or 460 volts. This is accom- plished by means of transformers to the low voltages Case depth shall be determined on a normal required. At these low voltages, magnetizing cur- tooth section. Hardness testers which produce small rents up to several thousand amperes are often used. shallow impressions should be used in order that the The trend in Europe is to use A.C. current for mag- hardness values obtained will be representative of netic particle testing because the intent of their test- the surface area being tested. Microhardness testers ing is location of surface discontinuities only. Subsur- which produce Diamond Pyramid or Knoop Hard- face discontinuities are best detected by radiography ness number are recommended, although other tes- or ultrasonic non---destructive test methods. A.C. ters such as Rockwell superficial A or 15 N scales can currents tends to give better particle mobility, and ANSI/AGMA 57 2004---B89 Gear Materials and Heat Treatment Manual demagnetization is more complete than with a D.C. (7) For prod magnetization with direct current, a field. minimum of 60 amperes per inch of prod spacing will There are two essential components of magnetic produce a minimum magnetizing force of 20 oersteds particle testing, each of equal importance for reliable at the midpoint of the prod line for plate 3/4 inch results. The first is the proper magnetization of the thick or less. A safer figure to use, however, is 200 part to be tested, with proper field strength in the ap- amps per inch, unless this current strength produces propriate direction for the detection of defects. The an interfering surface power pattern. Prod spacing second is the use of the proper magnetic particles for practical inspection purposes is limited to about type to secure the best possible defect indications un- eight (8) inches maximum, except in special cases. der prevailing conditions. (8) All parts should be demagnetized after mag- 6.6.4.1 General Principles. Some general prin- netic particle inspection. ciples and rules on magnetizing means, field strength, current distribution and strength require- ments are listed below (refer to Figs 6---1 and 6---2). FIELD (1) Fields should be at 90 degrees to the direc- HEAD tion of defects. This may require magnetizing in two directions. BATH (2) Fields generated by electric currents are at 90 degrees to the direction of current flow. (3) When magnetizing with electric currents, CURRENT pass the current in a direction parallel to the direc- tion of expected discontinuities. DISCONTINUITY (4) Circular magnetization has the advantage over longitudinal magnetization in that there are HEAD SHOT few, if any, local poles to cause confusion in particle CIRCULAR MAGNETIZATION LOCATES patterns, and it is preferred when a choice of meth- DISCONTINUITIES OCCURRING 45 --- 90 ods is permissible. DEGREES TO THE DIRECTION OF THE FIELD. (5) Circular magnetization specifications gener- INSPECT FOR PARTICLE INDICATIONS ally require from 100 to 1000 amps per inch of part SHOWING LONGITUDINAL DISCONTINUITIES --- MARK DISCONTINUTIES. diameter. Amperage requirements should be incor- porated into the magnetic particle procedure. Fig 6---1 Circular (Head Shot) Magnetic (6) For coil magnetization, a widely used formu- Particle Inspection la for amperage calculations is: 6.6.4.2 Magnetic Particles. The particles used are finely divided ferromagnetic material. Properties NI = 45 000 (Eq 6.1) vary over a wide range for different applications in- L/ D cluding magnetic properties, size, shape, density, mobility and visibility or contrast. Varying require- where ments for varying conditions of test and varying NI = ampere turns required, properties of suitable materials have led to the devel- L/D = length to diameter ratio. opment of a large number of different types of avail- NOTE: The 45 000 constant may vary with able materials. The choice of which one to use is an specifications. important one, since the appearance of the particle ANSI/AGMA 58 2004---B89 Gear Materials and Heat Treatment Manual patterns at discontinuities will be affected, even to methods is in the range of 60 to 40 microns. Particles the point of whether or not a pattern is formed. larger than this tend to settle out of suspension rapid- ly. In general, wet method materials exhibit a greater FIELD CURRENT THROUGH sensitivity than dry powders. Fluorescent particles COIL have the greatest contrast of the wet method materi- als. Although fluorescent wet particles have the greatest sensitivity and contrast, they can provide a confusing background on surfaces with a finish great- er than 250 RMS. BATH 6.6.4.3 Documented Procedures. Written proce- dures for magnetic particle testing should as a mini- mum include: DISCONTINUITY (1) Which ASTM, ASNT or agency specifica- COIL SHOT tions the procedure meets. LONGITUDINAL MAGNETIZATION LOCATES TRAVERSE DISCONTINUITIES. (2) Qualifications--- INSPECT FOR PARTICLE INDICATIONS (a) Indicate that the operators are qualified SHOWING TRANSVERSE DISCONTINUITIES. and tested to ASNT---TC---1A Level II, MIL--- STD---271F, etc. NOTE: EFFECTIVE LENGTH MAGNETIZED BY (b) Indicate type of equipment used for in- COIL SHOT IS A FEW INCHES ON EITHER spection, A.C. and D.C. full wave rectified, etc. SIDE OF COIL. MAXIMUM LENGTH OF (c) Indicate type of particles used for inspec- ARTICLE COVERED BY ONE SHOT IS 18 INCHES (46 CM). ON LONG ARTICLES, tion, fluorescent or black visible, wet or dry particle. REPEAT SHOTS AND BATHS DOWN THE For the wet method, particle concentration should LENGTH OF ARTICLE. PLACE ARTICLES also be indicated. CLOSE TO THE COIL BODY. (3) General--- Fig 6---2 Coil Shot Magnetic Particle (a) State when inspection is to be done; after Inspection heat treat, finish machining, etc. (b) State what the surface will be; for exam- (1) Dry Powders. It is evident that size plays an ple, 250 RMS, black forge, etc. important part in the behavior of magnetic particles. A large, heavy particle is not likely to be arrested and (c) State amps per inch of diameter for cir- held by a weak field when such particles are moving cular magnetization and the formula used for cal- over the surface of the part. On the other hand, very culation of longitudinal magnetization. fine powders will be held by very weak fields, since (d) State what method will be used for deter- their mass is very small. Extremely fine particles may mining field magitude; such as pie gage, etc. also adhere to the surface where there are no discon- (e) State demagnetization, if required, and tinuities, especially if it is rough, and form confusing level of demagnetization required. backgrounds. Most dry ferromagnetic powders used (4) Standard of Acceptance for detecting discontinuities are careful mixtures of (a) Indicate maximum size and density of particles of all sizes. The smaller ones add sensitivity indications permitted. and mobility, while the larger ones not only aid in lo- (b)Indicate reporting procedures if cating large defects, but by a sweeping action, coun- needed. teract the tendency of fine powders to leave a dusty For further information on magnetic particle background. Thus, by including the entire size range, testing, refer to: a balanced powder with sensitivity over most of the Principles of Magnetic Particle Testing, C.E. Betz range of sizes of discontinuities is produced. Metals Handbook Volume II Eighth Edition (2) Wet Method Materials. When the ferromag- Nondestructive Inspection and Quality Control netic particles are applied as a suspension in some Nondestructive Testing Handbook, Edited by liquid medium, much finer particles can be used. The Robert C. McMasters for the Society for Nonde- upper limit of particle size in most commercial wet structive Testing ANSI/AGMA 59 2004---B89 for addi- tional information. (2) ASTM A609. loscope screen as illustrated in Fig 6---4. As an exam- Very short sound waves of a frequency greater than ple. Ultrasonic inspec. tire tooth surface. both expressed in a percent 125---250 micro---inch maximum surface roughness. sensitivity may be adjusted to establish the speci- 20. or at The tooth mass will have a significant effect on the the sensitivity to obtain an indication of specified resulting microstructure and hardness throughout height from a flat bottom hole drilled into test blocks.” provides a Castings: measure of distance or depth in the work piece. the pulse echo technique. test block requirements. Steel Castings. fications and interpretation of test results. the instrument must be cali. (1) AGMA 6033---A88. Scanning sensitivity and indication limitations tion is a nondestructive test method to determine the are often determined using test blocks by establish- internal soundness and cleanliness of gearing by ing a distance---amplitude reference line on the oscil- passing sound (ultrasound) through the material. Carbon and Low Alloy. with the transducer and work ety for Metals (ASM) Metals Handbook. brated according to the test specification. The sweep line can be calibrated by use of a test block or section of known thickness in the work piece in or. or to the American Soci- water as the couplant. Hardened steel gearing micro- ning surface can. The returning signals are subsequently mon. reflecting off of the back surface and in the middle is (2) ASTM A388. for coupling the ultrasonic transduc. The American Society for Testing Materials and The indication to the left of the oscilloscope screen in AGMA specifications which follow may be used for Fig 6---3 is caused by the sound wave entering the ultrasonic inspection of wrought and cast gearing. The heat treatment variables will ANSI/AGMA 60 2004---B89 . to just obtain a specified back reflection height. The second method uses manufacturer’s literature. lated to the rate of travel of sound in the material. Forgings and bar stock: ence. on “Non---Destructive Testing” (SNDT). as re. depending between the two points. horizontal line. application limita- transducer both emits sound waves and receives the tions. namely. Untreated coarse erence line. the requirements and qualification. such as the out. The Heavy Steel Forgings. Ultrasonic Examination of the signal reflecting from any defects shown. Important considerations in- With the most common technique of ultrasonic clude appropriate transducer frequency. Also. be determined. Any indication noted must upon the media. glycerin or a commercial paste spread evenly on Reference can be made to the equipment the surfaces to be inspected. The major function of the mate- der that each marker shown on the sweep line repre. of the back reflection height established during cal- This provides improved contact for the transducer ibration for scanning sensitivity. steel and is called “initial pulse” or “contact interfer. Section 11. not exceed the determined distance---amplitude ref- er to the heat treated work piece. called the “sweep line. Scanning The microstructure will vary around the gear sensitivity is often established as either the sensitivity tooth flank and throughout the tooth cross section.” The indication to the right is caused by sound (1) AGMA 6033---A88. structure should be tempered martensite at the en- Before testing. the indication from the sound waves are transformed into voltage and moni. 6. with the work piece.6. therefore. Ultrasonic Examination Thereof. In the method most often used. work piece requirements (grain size). rial selection and heat treating process is to achieve the desired microstructure at the critical locations so sents a standard distance or depth. grained structures do not lend themselves to ultra. on the oscilloscope screen. A straight line is drawn There are two test methods used. indications are often specified not to ex- sonic testing. test speci- defects. instru- returning signals from the back surface and possible ment calibration. operator inspection.5 Ultrasonic Inspection. flat bottom hole (FBH) in the 4 inch (102 mm) block. same size FBH in the 12 inch (305 mm) block is noted tored on an oscilloscope screen. ducer.7 Microstructure. Gear Materials and Heat Treatment Manual 6. Surfaces to be scanned. Section 10. One method uses a couplant: oil. itored on an oscilloscope screen as shown in Fig 6---3. Depth of the de- that the part will have the desired contact and bend- fect from the transducer contact point on the scan- ing strength capacity. ceed a certain magnitude and length on the scanning side diameter and ends or end faces of cylindrical or surface or result in loss in back reflection height ex- disc shaped rough stock are generally machined to ceeding specified limits. returning and at the same sensitivity.000 cycles per second (audible limit) are voltage fied indication height [2 1/2 inch (63 mm)] from the generated and transmitted into the part by a trans. Volume 11 piece submerged in a tank. the tooth section. ture considerations as well as hardness control. Gear Materials and Heat Treatment Manual significantly effect the microstructure achieved. Gear tooth quality control must include microstruc- TRANSDUCER SUITABLE COUPLANT ON SURFACE X Y DEFECT BACK REFLECTING SURFACE INITIAL PULSE BACK REFLECTION Y X 3 in (76 mm) DEFECT MARKERS Fig 6---3 Ultrasonic Inspection with Oscilloscope Screen ANSI/AGMA 61 2004---B89 . carbide always exist at the ends of the hardened pattern. Bainite. Dis- at the gear tooth surface and at core positions. pearlite. and ferrite are undesirable at erations. ANSI/AGMA 62 2004---B89 . concern. forms and distribution are an area of microstructure Microstructure evaluation must include the exis. within limits. width and location of heat effected zones which will In carburized and hardened steel gears. nite will exist in the case after the heat treating op. retained auste. Some research has shown that micro- duction hardened steel gears must also consider the cracks are produced by subzero treating. Subzero treatment is These structures will exist in core microstructures of specified for some applications to reduce retained coarse tooth gearing. Continuous network carbide is generally tence of structures other than tempered martensite considered to be unacceptable microstructure. In continuous carbide network is generally allowed carburized and hardened steel gears. austenite.Amplitude Reference Line for Ultrasonic Inspection Control of the microstructures in flame and in. Data and opinions vary as to the allowable the gear tooth surface of surface hardened gearing. limits for retained austenite. Gear Materials and Heat Treatment Manual INDICATION FROM FBH IN 4 in (102 mm) BLOCK INDICATION D ---A REFERENCE LINE FROM FBH IN 12 in (306 2 1/2” mm) BLOCK (63 mm) 3 in 11 in (76 mm) (279 mm) TEST BLOCKS: 12 AND 4 in (306 AND 102 mm) TEST BLOCKS CONTAINING SAME SIZE FLAT BOTTOM HOLE DRILLED TO A DEPTH OF 1 in Fig 6---4 Distance --. The indication of the quality of gear materials. Mechani- Mechanical properties of forgings and bar stock are cal properties obtained from test coupons. the smaller section of the standard in- Smaller section test coupons are typically spe. causes variance in mechanical properties. (e.8.9) which means that proper. gearing. chanical properties of gearing for the reasons cited in Location or depth of the test coupon from the 6. measured and actual properties of gearing. design of gearing to accommodate variance between regation is increased and degree of mechanical work. from the outside diameter. are generally higher for test respect to direction of metal flow and inclusion coupons than for actual forged or cast gearing. lated to improved solidification mechanism (re- ment testing limitations. In addi- ing is reduced towards the center of hot worked or tion to test coupons providing indications as to the wrought sections. area measured after tensile testing). Small section of the test bar provide a comparison of steel quality between differ- being tested. 6.8. Also. as compared to larger used for gearing. smaller section test bars NOTE: It should be realized. not typ- section or from the center) and its effect with respect ical properties. however. metallurgical quality of gear materials. bet- otherwise specified. and the smaller section of the gearing ent orders and can often help identify problems in from which the test coupon may have been obtained steel making and heat treating. tensile ductility (percent elongation and reduction of ties vary in the longitudinal and transverse (or tan.1 and 6. however. such as standard impact test bars.1 Reasons for Mechanical Property Vari- chanical property variance compared to larger cast ance. duced micro---segregation and micro---unsoundness) and increased response to heat treating. test coupons should be minimum properties. forged sections.8. Mechanical properties ob- vides optimum properties compared to properties tained from test coupons should be considered as an from the transverse (or tangential) direction. cast iron (a) Mass effect. pro- 6. especially anisotropic (refer to 4. causes me- 6.g.2.8. impact strength gential) directions.3 Interpretation. tained from test coupons not being equivalent to (b) Location of the test coupon.g. This variance is due mainly to the in- standards for evaluating mechanical properties of creased degree of mechanical working and increased wrought and cast steel and non---ferrous materials response to heat treating. re- the actual properties of gearing from which sults in improved properties compared to larger cast the test coupons were obtained or associated. that and sections show improved mechanical properties. mid--. but should transverse (or tangential) direction is more repre- not be interpreted as representing the precise me- sentative of gear teeth depending upon helix angle. Seg. Small section of the test bar and non---ferrous alloys are not equivalent to being tested. Generally. The reasons for mechanical properties ob- sections. Test coupon those of gearing include the following consider- may be better located during heat treatment. test coupons (b) Mass effect. however. shaft extension). provided hardness of the test coupons is reported by forging manufacturers for solid on shaft within the specified range. has an effect on mechanical Test coupons are specified by company and industry properties. Gear Materials and Heat Treatment Manual 6. (a) Test coupon orientation and location. The longitudinal direction. Unless sile and yield strengths of test coupons. Designers should incorporate ap- to the degree of mechanical working and segrega. Specified mechanical properties for forged section (e. ANSI/AGMA 63 2004---B89 . test results from shaft exten.2 Mechanical Properties Affected. mechanical properties obtained from test (2) Castings--- coupons for wrought and cast steel. ter represent actual corresponding properties of sions in the longitudinal direction are those typically gearing. propriate factors of safety based on experience for tion. These directions are defined with and fatigue strength. sections.8. tegral or separate cast test coupons. and its effect re- cified for economic considerations and instru. Ten- orientation induced by mechanical working. causing ations: increased response to heat treating and improved (1) Wrought Forgings and Bar stock--.8 Mechanical Property Test Bar Considerations. mechanical properties. Standard Reference Radiographs for Heavy Walled (2 to 4 1/2 inch)(51 to 114 mm) Steel Castings ASTM E280---81. 105 College Road East\Princeton. Reference Photographs for Magnetic Particle Indications on Ferrous Castings ASTM E186---80. Specification for Steel Castings. for Steam Turbines ASTM E125---63 (1980). PA 19103 (215) 697---3321 (215) 299---5400 Military Standards ASTM Standards Metal Powder Industries Federation Society of Automotive Engineers. Specification for Carbon and Alloy Steel Forgings for Pinions and Gears for Reduction Gears ASTM A356---83. PA 19120 Philadelphia. Ultrasonic Examination of Carbon and Low Alloy Steel Castings ASTM E709---80. Heavy---Walled. 20036 Metals Handbooks (202) 452---7100 Heat Treaters Guide AISI Steel Products Manuals Metals Reference Book Naval Publications and Forms Center American Society for Testing and Materials 5801 Tabor Avenue 1916 Race Street Philadelphia. Magnetic Particle Examination MIL---H---6875G (Feb 86). OH 44073 1000 16th Street. Standard Reference Radiographs for Heavy Walled (4 1/2 to 12 inch)(114 to 305 mm) Steel Castings ASTM E446---81. Standard Reference Radiographs for Steel Castings Up to 2 inch (51 mm) in Thickness ASTM E609---83. D.C. Gear Materials and Heat Treatment Manual Bibliography ASTM A148---83. NJ 080540 400 Commonwealth Drive (609) 542---7700 Warrendale. Inc. Specifications for Steel Castings for High Strength Structural Purposes ASTM A291---82. PA 15096 MPIF Standard 35 (412) 776---4841 Other: SAE Handbook Gray and Ductile Iron Castings Handbook AMS Standards Cast Steel Handbook Modern Plastics Encyclopedia ANSI/AGMA 64 2004---B89 . NW (216) 338---5151 Washington. Process for Heat Treatment of Steel Reference Addresses American Society for Metals American Iron and Steel Institute Metals Park. Carbon and Low Alloy. Purpose. lightly loaded gear applications. Under certain operating conditions. have been known to out. mineral fillers. as well as one version with fibrous PTFE. ability to better dampen moderate shock or impact A5. The maximum load erally used with the addition of glass fiber and/or carrying capacity of most plastic gears decreases as PTFE lubricant and is a fine. with and without lubricants. wear equivalent metal gears. testing. Polycarbonate is gen- A4. to appropriate product standards. gears.6 Polyester (T/P). and quality level higher temperatures are encountered. Load Carrying Capacity. The inherent resiliency of some of 40---65 percent fiber glass reinforced and has good the plastic used may result in better conjugate action. and are finding their way lose approximately 50 percent of their rated into more markets as a molded gearing material in strength. Polyimide is usually in metal gearing. when operating at low stress lev. Gear Materials and Heat Treatment Manual Appendix A Plastic Gear Materials [This Appendix is provided for informational purposes only and should not be construed as part of AGMA Standard 2004---B89. Acetal has a lower water ab- brication. high efficiency performance. Tolerances. therefore. Phenolics are gener- mance. and when manufacturing. and such lubricants as PTFE and Many plastic gearing materials have inherent lu.2 Polyimide (T/S). Many different plastics are stable. with the latter being by vide information on plastic materials which have far the most prevalent. plastic 6/6. Polyesters are both un- plastic gears is 250_F(121_C) at which point they filled and with glass fiber. refer A5. specifications should be utilized in plastic gearing as A5. Generally. mineral. Polyurethane is gener- Very little degradation of mechanical properties in ally noted for its flexibility and. Nylon may be compounded with various eration. Operating Characteristics. The upper temperature limit of most thermo.3 Nylon(T/P --. For physical properties. is more posed to many chemicals which have a corrosive ef- stable after molding or machining. low shrinkage material and is used in some now used for gearing.7 Polyurethane (T/P). are used unfilled or filled. ability to absorb shock and deaden sound. trafluorethylene) and graphite. The purpose of this Appendix is to pro. been used for gearing. types and amounts of glass reinforcing materials. Phenolics are invariably compounded with various A2. bricity so that gears require little or no external lu- A5. A5. The most plastics materials. measuring. They can perform satisfactorily when ex- sorption rate than nylon and. A5. Ny- type loads within the capabilities of the particular lon is a family of thermoplastic polymers. sisal. ANSI/AGMA 65 2004---B89 . SAN is a A5. with glass and minerals Plastic gearing. the tolerances for plastic gears may be less critical chopped cloth.] A1. Gear Materials and Heat Treatment Manual. strength retention when used at high operating tem- The resiliency of many plastic gears gives them the peratures. such as PTFE and els in certain environments. but nylon 6 and nylon 12 are also used. fillers such as woodflour.5 Polycarbonate (T/P). the same care in ally used in applications requiring stability. moplastic material are used. Ordinarily. tures up to 450_F(232_C). Plastic Materials.4 Acetal (T/P). A5. thermosetting gears now exceeds 400_F(250_C). and such lubricants as PTFE (polyte- than for metal gears for smooth and quiet perfor. The upper operating temperature limit of competition with nylon and acetal. low shrinkage material the temperature increases more than with metal for producing consistently accurate molded gears. Some ny- gearing materials are noted for low coefficient of lons absorb moisture which may cause dimensional friction. and quiet op. Acetal polymers fect on metal gears. widely used of any molded gearing material is nylon A3. MoS2 (molybdenum disulfide). has the certain thermosetting materials occurs at tempera. glass. therefore.1 Phenolic(T/S --. A5. instability. however.indicates thermosetting).indicates thermoplastic).8 SAN (Styreneacrylonitrile) (T/P). Both thermosetting and ther. MoS2. 1 Industrial Laminated Thermosetting tomer is a newcomer to the gearing field. than an equivalent machined gear. Lower chines and with standard tools. Asbestos---phenolic grades have excellent ther- chined gears may be generally better than their mal and dimensional stability. paper. because of the flow of the material into the tooth cav. A9. Plastic Gearing References. Several plastic gears can be pregnated or coated with a phenolic resin and con- molded together as a gear cluster. whether in sheet or rod cellent sound deadening qualities and resistance to form.9 Polyphenylene Sulfid (T/P). Fabric base grades are chosen to withstand se- A7. Gears of linen base phenolic quantity warrants the cost of the mold. Gear Materials and Heat Treatment Manual A5. A9. among other advan- materials such as cellulose. Many of these plastic materials. ANSI/AGMA 66 2004---B89 . Machined tion. These materials are im- A6. or mat. it has been found in certain gear er means. high resiliency. even at bly contribute to noise during operation. sprockets. A9. Machined Plastics Gears. fabric. molded counterparts. and Other Methods. and creep. Gear cutting is done on standard ma. It should be noted that all grades have chined parts. Final tooth strength is generally better in a molded gear. no. Combinations of solidated under high pressures and temperatures gears. squares. Plastics Gearing --.10 Polymer Elastomer (T/P). asbestos. my. Feather edge burrs. The use of controlled load check- finish machining to meet most commercial quality ing equipment is almost mandatory to avoid errors in requirements. Phenolics are used for fine pitch gears due to econo- ity of the mold. but the molded tooth surface is The glass fabric base grades have good heat re- superior to the machined surface in smoothness and sistance and very high tensile and impact strength. The linen grades rectangles of various sizes from which gears can be made with finer textured lightweight fabrics will ma- machined. gearing. and less brittle than paper base grades. pulleys.1 Inspection. The modulus of elasticity is so Chopped fabric impregnated with phenolic resin is low in plastics that errors in measurements are very capable of being molded as a gear but may require difficult to control. vere shock loads and repeated bending stresses. A8. glass fabric. These products. The following consid. weight ratios.2 Performance Characteristics. Fabric base grades are tougher and dard extruded shapes. into various grades which have properties useful for duced as a single part. contain laminations or plies of fibrous sheet flex fatigue. will impair inspection of gearing and possi- applications to have much greater strength. and high wear resistance. impact. Gears can be molded at less cost if large chine with less trouble. Laminated Phenolics Plastics.01. toughness. such as rounds. When com. A8.Molded. A8.2 Tools. Gear Blanks. measurements. and thus may require a hardened steel mate and adequate lubrication. density than metals often provides higher strength to erations will assist in obtaining higher quality ma. and tably unfilled nylon and acetal. A8. cotton tageous characteristics. The quality of ma. and has ex- Products. Part Combinations. some dimensional change due to humidity.3 Burrs.3 Chopped Fabric Molding Compound. if not elimi- pounded with 40 percent glass fiber with or without nated by back up discs or subsequent removal by oth- internal lubricants. AGMA 141. A5. Polymer elas- A9. elevated temperatures. are available in stan. avoid tooth profile and size variation due to deflec. Sharp cutting tools are necessary to A10. to resist wear. and cams can also be pro. are abrasive. than most materials pre- viously available. ] B1. Maximum recommended sizes for flame or induction hardening gearing would be same as above. in (mm) Specified Brinell Hardness AISI 4140 AISI 4340 4350 Type [ 223---262 To 8.0 (203) included No restriction 363---415 w ** Not recommended To 3. mize distortion during heat treatment must mum controlling section size for steel is based princi. illustrations as to how B3.75 (95) included To 23. Definition. maximum controlling size. but costs should be evaluated due to reduced machinability. [ 4350 Type Steel is generally considered equivalent to AISI 4340 for chemical analysis. ANSI/AGMA 67 2004---B89 . Figure B---1 illustrates controlling maximum controlling section size is determined for sections for quenched gear configurations whose gearing. NOTE: Evaluation of the controlling section terials. Illustrations. ] “No restriction” indicates maximum controlling section size is not anticipated to provide any restrictions for conventional size gearing w 900_F(482_C) minimum temper may be required to meet these hardness specifications.5(115) included No restriction No restriction 285---311 To 4. except that carbon is 0. Ma.0 (76) included To 15. section sizes for several low alloy steels from AGMA 6033---A88.48---0. quenching and tempering temper- ations for through hardened (quench and tempered) ature considerations. The controlling section of a part of steel and/or specified hardness need not is defined as that section which has the greatest effect include consideration of standard rough in determining the rate of cooling during quenching stock machining allowances. NOTES: * Maximum controlling section sizes higher than those above can be recommended when substantiated by test data (heat treat practice). ** Higher specified hardnesses (e.0 (640) included No restriction 302---352 To 3.0(203) included No restriction ] No restriction ] 248---293 To 5. Part 1. Also presented are factors which affect 4.5(140) included No restriction No restriction 262---311 To 4. desired hardness. Reference should be made to gearing. Other special at the location (section) where the specified mechan. The maxi.0(102) included To 25. This Appendix presents approxi. depth of mate maximum controlling section size consider.6 of the Standard for hardenability considerations. Purpose.55 percent. specified hardness. Table B---1 Approximate Maximum Recommended Controlling Section Size* Alloy Controlling Section Size.5). Gear Materials and Heat Treatment Manual. dependent upon specified core hardness.0 (380) included No restriction 321---363 Not recommended To 12. 375---415 HB.g. Marine Propulsion Gear Units. Gear Materials and Heat Treatment Manual Appendix B Approximate Maximum Controlling Section Size Considerations for Through Hardened Gearing [This Appendix is provided for informational purposes only and should not be construed as part of AGMA Standard 2004---B89. stock allowances such as those used to mini- ical properties (hardness) are required. Maximum recommended controlling section sizes for nitrided gearing are less than those above for the same hardness range because of higher tempering temperature required for nitriding gearing (refer to 5. be considered. size for the selection of an appropriate type B2. pally on hardenability. and recommended maximum controlling teeth are machined after heat treatment.0 (305) included No restriction 341---388 w Not recommended To 8. 388---321 HB and 401---444 HB) are used for special gearing.0 (585) incl. --.--. may also require maximum controlling section size tion sizes versus specified hardness for section sizes considerations if the design does not permit liquid to 8.--.5) of several low alloy steels based on specified greater than 8. Recommendations. Table B---1 provides approx.--- 4 inch (102) 8 inch 32 36 inch (203) inch --.--. In---house normalized and tem- Practical Data for Metallurgists by Timkin Steel Co. (254) 6 inch (152) Controlling Section: 8 in (203 mm) Controlling Section: 2 in (50 mm) Diameter Face width TEETH TEETH --.--.--. sizes for oil quenched and tempered gearing (H = Maximum controlling section sizes for rounds 0. and published tempering response/hardenability imate recommended maximum controlling section data.--. the roots of teeth.--.--.. Maximum controlling sec. (914) (813) 36 inch (914) 12 inch (304) Controlling Section: 2 in (50 mm) Wall Thickness (If the bore diameter is less Controlling Section: 2 in (50 mm) than 20% of the length of the bore. pered/hardness testing experiments are required. Gear Materials and Heat Treatment Manual B4.--.0 inch (203 mm) diameter rounds can also be quenching.--.--. General Comments. generally re- hardness range.--. Normalized and tempered heavy section gearing B5.--. however.--- 8 1.--.--. quire in---house heat treat experiments of larger sec- ening. and higher hardenability steel Round Bars from Jominy Test Results” published in may be required. normal stock allowance before hard.--. then the Rim Thickness outside diameter) Fig B---1 Illustrations of Controlling Section Size ANSI/AGMA 68 2004---B89 .--. TEETH TEETH 2 inch (50) --. minimum tempering temperature of tions followed by sectioning and transverse hardness 900_F(482_C) and obtaining minimum hardness at testing. Specified hardnesses able to be obtained approximated by use of the “Chart Predicting with the same type steel (hardenability) is consider- Approximate Cross Section Hardness of Quenched ably lower.--.5 inch inch (38) 10 (203) inch --.--.D.--.0 inch (205 mm) O.--. To ensure that the steel under ing. It may be used in conjunction with design and consideration has sufficient case hardenability to be other considerations to select the appropriate grade capable of satisfactorily hardening the case in the of steel. The controlling section size of carbu. can be evaluated by hardened gearing. heat removed during quench hardening. chined prior to carburize hardening. ASM Text (1980) AISI 4118 0 5 10 15 20 25 30 35 40 45 50 55 60 Approximate Controlling Section Size. This Appendix assists in the selection can be used for carburized gearing considerations of a grade of carburizing steel to insure that the car. The same examples solid line in Fig C---1).] C1. Steels not eral principles described in Appendix B for through shown on Fig C---1. Approximate Controlling Section Size. inch Fig C---1 Effect of Controlling Section on the Case Hardenability of Carburizing Grades of Steel ANSI/AGMA 69 2004---B89 . Figure C---1 is based on hardenability and controlling section size C2. Method. Figure B---1 in Appendix B de. Purpose. Fig C---1 should be used. Gear Materials and Heat Treatment Manual. Selection of Steel. Gear Materials and Heat Treatment Manual Appendix C Case Hardenability of Carburizing Steels [This Appendix is provided for informational purposes only and should not be construed as part of AGMA Standard 2004---B89. roots of teeth. The controlling ble of hardening roots of teeth to meet specified sur. section size in both instances is the section related to face hardness requirements. C3. dard hardening procedures used for carburized gear. mm 0 200 400 600 800 1000 1200 1400 AISI 9310 AISI 4820 ADEQUATE CASE HARDENABILITY AISI 4320 AISI 8822 CASE MAY OR MAY NOT AISI 8620 HARDEN NO CASE HARDENABILITY Source: The Influence of Microstructure on the of Case ---Carburized Components by Geoffrey Parrish. Steels are presented in order of rized gearing can be determined using the same gen. considerations. hardenability on the ordinate of Fig C---1. comparing hardenability to those steels presented to scribes examples of how the controlling section size is determine the approximate maximum recom- determined for through hardened gearing when the mended controlling section size (as indicated by the teeth are cut after heat treating. therefore. The method used is the location of gear teeth which governs the rate of based on steel hardenability considerations and stan. without regard to the fact that gear teeth are ma- burized case has sufficient hardenability to be capa. microstructure. Nomenclature of Gear Tooth sembly and installation are major contributors to Failure Modes. D2. vibration due to inade. Improper selection shorter than expected life is obtained. D3. porosity. abrasive scoring. cold shuts. cracks. Pitting modes are initial pitting. wear. Service conditions cessive sliding and rolling contact stresses. D2. stock removal can leave undesirable surface defects. Gears are generally removed from ser. and bearings. Failures related to inade. secondary transformation products. If quate grounding. improper hard. decarburization.5 Maintenance.] D1. D3.e. pitting. cracks.7. insufficient or excessive stock removal after D2. carburized case and core. Steels can be ness. When with the design and application. flaking. ANSI/AGMA 70 2004---B89 . an in---depth in. These factors are gear face or subsurface) and toughness. assembly and crostructure after heat treatment. corrosion. service conditions and als such as hot rolled bars can have serious banding.3 Heat Treatment. the required combination of properties compatible D2. Although materials rare- vestigation should be initiated. and D2. loss of lubrication. tion criticals in the system causing vibration.6 Service Conditions. maintenance. pressure angle.2 Manufacture. and bursts from insuffi- which could shorten service life include grinding cient forging temperature. inadequate quench. improper weld repair. Pitting re- which could adversely effect gear life are excessive sistance is influenced by surface finish.7. Improper as- pictured in AGMA 110. etc. surface hard- temperatures. etc. destructive pitting. D3. cessive forging temperature.1 Wear. or improper mi- design. and misalignment. inadequate reduction. surface residual stress. specified to varying cleanliness levels. etc. heat treatment. Banding can affect properties. sand. Wrought materi- installation. Heat treat factors which could affect service life include under or over heat. inade- vice due to wear.3 Inclusions. faulty gaskets.4 Assembly and Installation. sions which relate to melting practices. particularly in a D2. shock or impact loading. material causes. surface de. Manufacturing practices improper grain flow. tooth thickness. Casting defects heat treatment. seals. Types of gear failure are D2. depth. Types of Gear Failures. An infrequent cause of ing. premature failures and manifest themselves in exces- sive loading. Purpose. and corrosion. a number of of material can result in inadequate hardness (sur- factors should be reviewed. shrinkage. slag. vibra. quate rigidity. stress risers which can contribute to premature failure include (tool marks and surface finish). Causes of Lower than Expected Life. fracture initiation is internal non---metallic inclu- carburization. D2. poor radii.7. plastic flow. ness. Gear Materials and Heat Treatment Manual. and spalling. and core hardness. etc. and result from ex- D2. or breakage.. the service life is less than expected. These usually occur at or above the pitch quate maintenance include: contamination of the line. flakes. D2.2 Casting Defects. chemical deviation. Failures related to gear de. microstructure.7 Material Causes. manufacture. they can contrib- briefly with the causes of gear failures and the types ute to failure if material selection results in less than of failures encountered. core shift. straightening.1 Gear Design. Inadequate and quench cracks. Gear Materials and Heat Treatment Manual Appendix D Service Life Considerations [This Appendix is provided for informational purposes only and should not be construed as part of AGMA Standard 2004---B89.1 Forging Defects. crostructure. D2. sign may be due to improper geometry or tolerances. This Appendix deals ly are the principal cause of failure. improper lubrication. overload. case depth. which is alloy and carbon segregation in banded form. corrosion. The most common wear failure modes are adhesion. gear class or which can contribute to premature failure include ex- type. burns. case contaminants. Wear is influenced by surface hardness and mi- system.2 Pitting. Forging defects i. Plastic flow modes are rolling. Gear Materials and Heat Treatment Manual D3. The majority of breakage fail- peening. and ridging. D3. Overload failures result from misapplication.4 Breakage. in heat affected zones of welds or in notch sensitive materials. Bending plastic flow ures (90 percent) are due to low and high cycle fa- occurs when the load exceeds the yield strength of tigue. and impact loading. rippling. Brittle failures may occur in low temperature the material. ANSI/AGMA 71 2004---B89 .3 Plastic Flow. service. misalignment.