1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2014 SAE International All rights reserved. No part of this p
3、ublication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-497
4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AMS2759/7B AEROSPACE MATERIAL SPECIFICATION AMS2759/7 REV. B Issued 1991-10 Revis
5、ed 2010-05 Reaffirmed 2014-04 Superseding AMS2759/7A Carburizing and Heat Treatment of Carburizing Grade Steel Parts RATIONALE AMS2759/7B has been reaffirmed to comply with the SAE five-year review policy. 1. SCOPE This specification, in conjunction with the general requirements for steel heat treat
6、ment covered in AMS2759, establishes the requirements and procedures for three classes of gas, vacuum, liquid, and low pressure (LPC) carburizing and related heat treatment of parts fabricated from carburizing grade steels. It does not cover pack carburizing. 1.1 Classification Parts to be carburize
7、d shall be processed to meet the requirements of one of the following classes: Class 1: Case depth and case hardness shall be as specified. Subsurface case hardness shall be in accordance with Table 1. Surface carbon shall be 0.70 to 1.00% (weight %). Retained austenite shall not exceed 10%. Intergr
8、anular carbides shall be scattered and discontinuous and shall not be evident in more than 40% of the grain boundaries. Class 2: Case depth and case hardness shall be as specified. Subsurface case hardness shall be in accordance with Table 1. Surface carbon shall be 0.75 to 1.10% (weight %). Retaine
9、d austenite shall not exceed 20%. Continuous carbide network shall not be evident in more than 80% of the grain boundaries. Class 3: Case depth and case hardness shall be as specified. 1.1.1 If class is not specified, parts shall be processed to meet the requirements of Class 2. 1.2 Types Type 1: Ga
10、s and vacuum carburizing Type 2: Liquid (salt bath) carburizing Type 3: Low Pressure (vacuum) carburizing (0.5 to 35 mbar) 1.2.1 If the type is not specified, Type 1 shall be used. SAE INTERNATIONAL AMS2759/7B Page 2 of 15 1.3 Safety - Hazardous Materials While the materials, methods, applications,
11、and processes described or referenced in this specification may involve the use of hazardous materials, this specification does not address the hazards that may be involved in such use. It is the sole responsibility of the user to ensure familiarity with the safe and proper use of any hazardous mate
12、rials and to take necessary precautionary measures to ensure the health and safety of all personnel involved. 2. APPLICABLE DOCUMENTS The issue of the following documents in effect on the date of the purchase order forms a part of this specification to the extent specified herein. The supplier may w
13、ork to a subsequent revision of a document unless a specific document issue is specified. When the referenced document has been cancelled and no superseding document has been specified, the last published issue of that document shall apply. 2.1 SAE Publications Available from SAE International, 400
14、Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. AMS2418 Plating, Copper AMS2750 Pyrometry AMS2759 Heat Treatment of Steel Parts, General Requirements AMS2759/1 Heat Treatment of Carbon and Low-Alloy Steel Parts Mini
15、mum Tensile Strength Below 220 ksi (1517 MPa) AMS2759/2 Heat Treatment of Low-Alloy Steel Parts Minimum Tensile Strength 220 ksi (1517 MPa) and Higher AMS2759/11 Stress Relief of Steel Parts AMS2769 Heat Treatment of Parts in Vacuum ARP1820 Chord Method of Evaluating Surface Microstructural Characte
16、ristics J423 Methods of Measuring Case Depth 2.2 ASTM Publications Available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, Tel: 610-832-9585, www.astm.org. ASTM E 3 Preparation of Metallographic Specimens ASTM E 18 Rockwell Hardness and Rockwell Sup
17、erficial Hardness of Metallic Materials ASTM E 384 Microindentation Hardness of Materials ASTM E 415 Optical Emission Vacuum Spectrometric Analysis of Carbon and Low Alloy Steel ASTM E 1019 Determination of Carbon, Sulfur, Nitrogen, Oxygen, and Hydrogen in Steel and in Iron, Nickel, and Cobalt Alloy
18、s 2.3 ASM Publications Available from ASM International, 9639 Kinsman Road, Materials Park, OH 44073-0002, Tel: 440-338-5151, www.asminternational.org. ASM Handbook Volume 09 Metallography and Microstructures (1985 Edition), ISBN 10: 0-87170-015-8 SAE INTERNATIONAL AMS2759/7B Page 3 of 15 3. TECHNIC
19、AL REQUIREMENTS 3.1 Equipment Shall conform to the requirements of AMS2759. 3.1.1 Quenching Equipment Shall be in accordance with AMS2759 and AMS2769 section on inert gas quenching. 3.1.2 Auxiliary Equipment Shall be in accordance with AMS2759. 3.1.3 Thermal Processing Equipment Pyrometry shall conf
20、orm to AMS2750. 3.1.4 Cleaning Equipment Shall be in accordance with AMS2759. 3.1.5 Carburizing Equipment The carburizing atmosphere shall be generated with mixtures of hydrocarbon compounds and gases reacting to supply the carbon. Circulation of the atmosphere shall be sufficient to provide uniform
21、 carburizing. 3.1.5.1 For Classes 1 and 2 gaseous carburizing, the process (time, temperature, gas flows (Type 1 vacuum only), carbon potential,) shall be automatically controlled, maintained and recorded. Manual equipment may be used to verify the automatic equipment. 3.1.5.2 For Types 1 and 3 vacu
22、um carburizing, precision gas flow meters (3.5%) or mass flow sensors shall record the additions of carburizing medium. The process (time, temperature, gas flows, vacuum levels, pressure, etc.) shall be automatically controlled, maintained and recorded. The carbon potential shall be determined by co
23、rrelation of the additions with the results from carbon gradient test specimens. 3.1.5.3 Other carburizing media, such as molten salt bath or fluidized beds, may be used when appropriate, except pack carburizing shall not be used. The carbon potential shall be determined by correlation with the resu
24、lts from carbon gradient test specimens. When molten salt baths are used, the medium shall be analyzed periodically for chemical composition. 3.1.5.4 Carbon potential shall be determined in accordance with 3.11.8 for Type 1 gas carburizing. 3.1.5.5 Accuracy of Atmosphere Control Instruments The accu
25、racy of instruments used for measuring and controlling carbon potential of Type 1 gas carburizing furnace atmospheres and the accuracy of instruments used for measuring and controlling pressure of Type 1 vacuum carburizing and Type 3 Low Pressure carburizing furnaces shall be checked as often as nec
26、essary to ensure that the equipment is operating properly and shall be calibrated. These activities shall be performed per manufacturers recommendations. 3.2 Sequence of Operations Shall be (1) preparation for carburizing, (2) carburizing, (3) cooling after carburizing, (4) hardening, and (5) temper
27、ing. The hardening operation may be omitted when cooling after carburizing has incorporated a quench in accordance with 3.6.4, and when the conditions of 3.2.1, 3.2.2, or 3.2.3 are satisfied. SAE INTERNATIONAL AMS2759/7B Page 4 of 15 3.2.1 Parts were quenched from the carburizing temperature and bot
28、h of the following apply: 3.2.1.1 Case depth is 0.020 inch (0.51 mm) or less. 3.2.1.2 Carburizing temperature was not higher than 1600 F (871 C). 3.2.2 Parts were furnace cooled to the austenitizing temperature, stabilized, and quenched in accordance with 3.6.4 and either of the following apply: 3.2
29、.2.1 Parts were made from a low hardenability steel (e.g., 1020, 4615, 4620, 8615, or 8620). 3.2.2.2 Parts were made from a high hardenability steel (e.g., 4320, 4820, or 9310), and were carburized to meet Class 3 requirements, or parts made to meet Class 1 or 2 requirements that have been approved
30、by the cognizant engineering organization. 3.2.3 Parts made from a low hardenability steel were quenched from the carburizing temperature and either of the following applies: 3.2.3.1 Parts were carburized to meet Class 2 or Class 3 requirements. 3.2.3.2 Parts were carburized to meet Class 1 requirem
31、ents and quenching from the carburizing temperature was approved by the cognizant engineering organization. 3.3 Preparation for Carburizing All metallurgical operations, such as brazing or welding, or stress inducing operations, such as forming or bending, should be completed prior to carburizing. P
32、arts shall be free from visible defects, contamination, and corrosion that may retard carburizing or be detrimental to the appearance or performance of the finished parts. 3.3.1 Stress Relief/Normalizing Parts may be stress relieved per AMS2759/11 or normalized prior to carburizing. Normalizing time
33、s and temperatures for commonly carburized steels are given in Tables 2 and 3. 3.3.2 Cleaning All parts shall have scale, oxides, residual oil film, and any other surface contamination removed prior to carburizing or heat treatment. Parts shall be cleaned as necessary for the process to be performed
34、. Cautionary note: Pre-oxidation following washing has proven useful in Type 3 processing providing the temperature does not exceed 500 F (260 C) 3.3.3 Masking Masking shall be copper plate, not less than 0.0008 inches (20 m) in thickness, applied in accordance with AMS2418. Other masking may be use
35、d if acceptable to the cognizant engineering organization. 3.3.4 Visual Inspection Masked or plated parts shall be visually inspected prior to and after carburizing. Parts exhibiting blistering, peeling, or porosity in the masking after carburizing shall be rejected. 3.3.5 Loading of Parts Load part
36、s to minimize distortion at temperature and assure free circulation of atmosphere and quench fluid. SAE INTERNATIONAL AMS2759/7B Page 5 of 15 3.4 Carburization 3.4.1 Carburizing Temperature Shall be at a selected temperature 25 F (14 C) consistent with the material to be carburized and the depth of
37、case required. Carburizing ranges are as follows: Type 1 - Gas Carburizing: 1450 to 1750 F (788 to 954 C) Type 1 - Vacuum Carburizing:1550 to 1900 F (843 to 1038 C) Type 2 - Liquid Carburizing: 1500 to 1750 F (815 to 954 C) Type 3 Low Pressure Carburizing: 1450 to 2100 F (788 to 1149 C) 3.4.2 Carbur
38、izing Potential The carbon potential, however controlled, shall be such as to provide the required case carbon content and case depth. 3.4.2.1 For Types 1 and 3 vacuum carburizing, the carbon potential shall be determined by correlation of the additions with the results from carbon gradient test spe
39、cimens. Cautionary note: Consideration must be given to the production operating conditions when developing a qualification/periodic testing plan for multiple chamber furnaces when evaluating carbon potential. Cautionary note: The surface area needs to be taken into consideration when establishing p
40、rocess control parameters. 3.5 Cooling after Carburizing Shall be in accordance with one of the following: 3.5.1 Quenching from the Carburizing Temperature 3.5.1.1 Cooling in a protective atmosphere or vacuum to 900 F (482 C) or lower, followed by cooling at a rate not faster than that provided by f
41、an circulated air or atmosphere. Fan cooling from the carburizing temperature is permitted. 3.5.1.2 Furnace cooling from the carburizing temperature to the austenitizing temperature in Table 2, stabilizing, and quenching, including press quenching. The press quenching procedure will require cognizan
42、t engineering approval. 3.6 Hardening Shall consist of austenitizing and quenching. It may be preceded by subcritical annealing in accordance with Tables 2 and 3, and cooling to ambient temperature. 3.6.1 Atmosphere Protective atmosphere or masking or both shall be used to protect part surfaces from
43、 decarburization, carburization, intergranular oxidation, and other surface damage during sub- critical annealing or austenitizing. Parts exhibiting blistering or peeling of the masking in the prior masked areas after exposure to elevated temperature shall be subject to rejection. 3.6.2 Rate of Heat
44、ing Hard parts (35 HRC) shall be preheated or stress relieved in accordance with AMS2929/11 prior to hardening. Preheating in air is permitted. SAE INTERNATIONAL AMS2759/7B Page 6 of 15 3.6.3 Austenitizing Temperature shall be as specified in Table 2. For steels not listed in Table 2, austenitizing
45、temperatures shall be specified by purchaser. The charge shall be held within the specified temperature range for sufficient time for necessary diffusion and transformation to take place. The soak times shown in Table 3 are recommended times. Soaking time shall commence when all control, thermocoupl
46、e(s) reach a temperature 5 F (3 C) below the austenitizing temperature or, and when the last of any other monitoring and recording thermocouples (excluding load thermocouples and thermocouples used only to monitor over-temperature) reach the minimum of the required temperature range. When soaking ti
47、me is based on one or more load thermocouples, it shall start when all load thermocouples have reached the minimum of the required temperature range. . The proper time interval will vary with the type of steel, power input to furnace and size of charge, as well as the nominal thickness and configura
48、tion of the individual parts. 3.6.4 Quenching Following austenitizing, parts shall be quenched in the media specified in Table 2 and as follows: 3.6.4.1 Oil Quenching Type 1 Gas Carburizing: Quench in circulating oil at a temperature between 60 to 160 F (16 to 71 C) at the start of the quenching ope
49、ration. The circulation of the oil shall be controlled so that the oil temperature does not exceed 200 F (93 C) at any time during the quenching operation. Parts may be quenched in a die or in an open basket, but in either case, the oil shall circulate around every part. Type 1 and Type 3 Vacuum and Low Pressure Carburizing: Oil Quenching shall be performed by transferring the parts from a heating chamber t
