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/AMS2759/2F AEROSPACE MATERIAL SPECIFICATION AMS2759/2 REV. F Issued 1984-10 Revis
5、ed 2010-05 Reaffirmed 2014-04 Superseding AMS2759/2E Heat Treatment of Low-Alloy Steel Parts Minimum Tensile Strength 220 ksi (1517 MPa) and Higher RATIONALE AMS2759/2F has been reaffirmed to comply with the SAE five-year review policy. 1. SCOPE This specification, in conjunction with the general re
6、quirements for steel heat treatment covered in AMS2759, establishes the requirements for heat treatment of low-alloy steel parts to minimum ultimate tensile strengths of 220 ksi (1517 MPa) and higher. Parts are defined in AMS2759. 2. APPLICABLE DOCUMENTS The issue of the following documents in effec
7、t on the date of the purchase order forms a part of this specification to the extent specified herein. The supplier may work 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 spec
8、ified, the last published issue of that document shall apply. 2.1 SAE Publications Available from SAE International, 400 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 AMS2424 Plating, Nicke
9、l, Low-Stressed Deposit AMS2759 Heat Treatment of Steel Parts, General Requirements ARP1820 Chord Method of Evaluating Surface Microstructural Characteristics 2.2 ASTM Publications Available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, Tel: 610-832
10、-9585, www.astm.org. ASTM E 384 Microindentation Hardness of Materials SAE INTERNATIONAL AMS2759/2F Page 2 of 13 3. TECHNICAL REQUIREMENTS 3.1 Heat Treatment Shall conform to AMS2759 and requirements specified herein. 3.2 Equipment Shall conform to AMS2759. Furnace temperature uniformity requirement
11、s for annealing, subcritical annealing, normalizing, hardening, straightening, stress relieving, and baking shall be 25 F (14 C), and for tempering or aging shall be 10 F (6 C). 3.3 Heating Environment Parts shall be controlled by type (See 3.3.1), and heat treated in the class of atmosphere (See 3.
12、3.2), permitted in Table 1 for that type when heating above 1250 F (677 C). When heating parts at 1250 F (677 C) or below, Class A, B, or C atmosphere may be used (See 8.2). TABLE 1 - ATMOSPHERES Part Classification (1)Class A Class B Class C Type 1 Permittted Permitted Permitted Type 2 Permitted PR
13、OHIBITED (2)Permitted (3)Type 3 Permitted Permitted PROHIBITED Type 4 Permitted Permitted (3) (4)PROHIBITED NOTES: (1) See 3.5.1.2. (2) Permitted provided the atmosphere is controlled to produce no carburization or nitridingas described in 3.5.1. (3) Prohibited if a specific requirement to control t
14、he surface carbon on all surfaces isspecified. (4) Not recommended for Aermet 100.3.3.1 Types of Parts The heat treating processor shall determine the part type. Type 1: Parts with 0.020 inch (0.51 mm) or more to be machined off all surfaces after heat treatment and parts with as-forged, as-cast, or
15、 hot-finished mill surfaces at time of heat treatment with all surfaces to be machined off. Unless informed that all surfaces will have at least 0.020 inch (0.51 mm) machined off, the heat treating processor shall assume all surfaces will not and shall control the part as Type 2, 3, or 4, as applica
16、ble. Type 2: Forgings, castings, sheet, strip, plate, bar, rod, tubing, and extrusions with hot-finished surfaces at time of heat treatment and which will remain on the finished part. Type 3: Parts with finished machined surfaces or surfaces with less than 0.020 inch (0.51 mm) to be machined off any
17、 surface after heat treatment and parts with protective coating on all surfaces. Type 4: Parts that are partially machined with both unmachined (e.g., as-forged, as-cast, or hot- finished mill surfaces) and finished/near-finished surfaces (e.g., finished machined surfaces, or machined surfaces with
18、less than 0.020 inch (0.51 mm) to be machined off after heat treatment). 3.3.1.1 If part type cannot be determined, the part shall be processed as Type 3. SAE INTERNATIONAL AMS2759/2F Page 3 of 13 3.3.2 Classes of Atmospheres Class A: Argon, hydrogen, helium, nitrogen, nitrogen-hydrogen blends, vacu
19、um, or neutral salt. Nitrogen from dissociated ammonia is not permitted. Class B: Endothermic, exothermic, or carbon-containing nitrogen-base (See 8.2). Class C: Air or products of combustion. 3.3.3 Atmospheres Atmosphere furnaces shall be controlled to ensure that surfaces of heat treated parts are
20、 within the limits specified in 3.5.1. Salt baths shall be tested in accordance with AMS2759. 3.3.4 Protective Coatings A supplemental coating or plating is permitted, when approved by the cognizant engineering organization. Fine grain copper plating in accordance with AMS2418 or nickel plating in a
21、ccordance with AMS2424 may be used without approval but the surface contamination specimens in 3.6.1 shall not be plated (See 8.3). 3.4 Procedure 3.4.1 Preheating Preheating until furnace stabilization in the 900 to 1200 F (482 to 649 C) range is recommended before heating parts above 1300 F (704 C)
22、 if the parts have previously been heat treated to a hardness greater than 35 HRC, have abrupt changes of section thickness, have sharp reentrant angles, have finished machined surfaces, have been welded, have been cold formed or straightened, have holes, or have sharp or only slightly-rounded notch
23、es or corners. 3.4.2 Soaking Heating shall be controlled, as described in AMS2759, such that either the heating medium or the part temperature, as applicable, is maintained at the set temperature in Table 2 or 3 for the soak time specified herein. Soaking shall commence when all control, indicating,
24、 and recording thermocouples reach the specified set temperature or, if load thermocouples as defined in AMS2759 are used, when the part temperature reaches the minimum of the furnace uniformity tolerance at the set temperature. 3.4.2.1 Parts coated with copper plate or similar reflective coatings t
25、hat tend to reflect radiant heat shall have their soak time increased by at least 50%, unless load thermocouples are used. 3.4.3 Annealing Shall be accomplished by heating to the temperature specified in Table 2, soaking for the time specified in Table 4, and cooling to below the temperature specifi
26、ed in Table 2 at the rate shown in Table 2 followed by air cooling to ambient temperature. Isothermal annealing treatments may be used providing equivalent hardness and microstructure are obtained. Isothermal annealing shall be accomplished by heating to the annealing temperature specified in Table
27、2, soaking for the time specified in Table 4, cooling to a temperature below the critical, holding for sufficient time to complete transformation, and air cooling to ambient temperature. 3.4.4 Subcritical Annealing Shall be accomplished prior to hardening by heating in the range 1150 to 1250 F (621
28、to 677 C), soaking for the time specified in Table 4, and cooling to ambient temperature. Steel parts of the 9Ni - 4Co types shall be subcritical annealed as specified in Table 2. SAE INTERNATIONAL AMS2759/2F Page 4 of 13 3.4.5 Pre-Hardening Stress Relieving Shall be accomplished prior to hardening
29、by heating in the range 1000 to 1250 F (538 to 677 C), soaking for not less than the time specified in Table 4, and cooling to ambient temperature. 3.4.6 Normalizing Shall be accomplished by heating to the temperature specified in Table 2, soaking for the time specified in Table 4, and cooling in ai
30、r or atmosphere to ambient temperature. Circulating air or atmosphere is recommended for thicknesses greater than 3 inches (76.2 mm). Normalizing may be followed by tempering or subcritical annealing. 3.4.7 Hardening (Austenitizing and Quenching) All parts, except those made from H-11, 52100, or M-5
31、0 steels, shall be in one of the following conditions prior to austenitizing: normalized, normalized and tempered, normalized and overaged, or hardened. If such parts have been normalized only, without tempering or overaging, they shall be preheated within the range of 850 to 1250 F (454 to 677 C) b
32、efore exposure to the austenitizing temperature (See Table 2 Note 2). Welded parts and brazed parts with a brazing temperature above the normalizing temperature shall be normalized before hardening. Welded parts should be preheated in accordance with 3.4.1. Hardening shall be accomplished by heating
33、 to the austenitizing temperature specified in Table 2, soaking for the time specified in Table 4, and quenching as specified in Table 2. The parts shall be cooled to or below the quenchant temperature before tempering. 3.4.8 Tempering or Aging Shall be accomplished by heating quenched parts to the
34、temperature required to produce the specified properties. Parts should be tempered within 2 hours of quenching (See 3.4.8.1). Tempering for specific tensile strengths for each alloy is shown in Table 3. Soaking time shall be not less than 2 hours plus 1 hour additional for each inch (25 mm) of thick
35、ness or fraction thereof greater than 1 inch (25 mm). Thickness is defined in AMS2759. When load thermocouples are used, the soaking time shall be not less than 2 hours. Multiple tempering is permitted. When multiple tempering is used, parts shall be cooled to ambient temperature between tempering t
36、reatments. 3.4.8.1 Prior to final tempering parts may be snap tempered for 2 hours at a temperature, usually 400 F (204 C), that is lower than the final tempering temperature (See 8.5.1). 3.4.9 Straightening When approved by the cognizant engineering organization, straightening shall be accomplished
37、 at either ambient temperature, during tempering, or by heating to not higher than 50 F (28 C) below the tempering temperature. Ambient temperature straightening or hot or warm straightening after tempering shall be followed by stress relieving. It is permissible to retemper at a temperature not hig
38、her than the last tempering temperature after straightening during tempering. 3.4.10 Post-Tempering Stress Relieving When required by the cognizant engineering organization, parts shall, after operations which follow hardening and tempering, be stress relieved by heating the parts to 50 F (28 C) bel
39、ow the tempering temperature and soaking for not less than 1 hour plus 1 hour additional for each inch (25 mm) of thickness or fraction thereof greater than 1 inch (25 mm). When load thermocouples are used, the soaking time shall be not less than 1 hour. Stress relief is prohibited on parts that hav
40、e been peened or thread- or fillet-rolled after hardening and tempering. 3.5 Properties Parts shall conform to the hardness specified by the cognizant engineering organization or to the hardness converted from the required tensile strength in accordance with AMS2759. SAE INTERNATIONAL AMS2759/2F Pag
41、e 5 of 13 3.5.1 Surface Contamination Salt baths and the protective atmosphere in furnaces for heating parts above 1250 F (677 C), when less than 0.020 inch (0.51 mm) of metal is to be removed from any surface, shall be controlled to prevent carburization or nitriding and to prevent complete decarbu
42、rization (See 3.5.1.1). Partial decarburization shall not exceed 0.006 inch (0.15 mm) and a severity of 5 points HRC converted from Knoop. Depth and severity are described in ARP1820. Intergranular attack shall not exceed 0.0007 inch (0.018 mm). Rejection criterion for total depth of decarburization
43、 shall be the microhardness reading that has more than a 20-point Knoop, or equivalent, decrease in hardness from the core hardness. Rejection criterion for severity of decarburization is the difference between the HRC hardness (converted from Knoop) at 0.0003 inch (0.008 mm) and that of the core. R
44、ejection criterion for carburization and nitriding shall be that the microhardness shall not exceed the core hardness by 20 points Knoop or more, or equivalent, at a depth of 0.0003 inch (0.008 mm). Tests shall be in accordance with 3.6.1. The requirements of this paragraph also apply to the cumulat
45、ive effects of operations such as normalizing followed by austenitizing or austenitizing followed by reaustenitizing (See 3.5.1.4). For reheat treatments, the original specimen or a portion thereof shall accompany the parts and be tested after the reheat treatment. 3.5.1.1 Unless specifically inform
46、ed that at least 0.020 inch (0.51 mm) will be removed from all surfaces of parts, the heat treating processor shall heat treat the parts as if less than 0.020 inch (0.51 mm) will be removed from some surfaces and, therefore, shall heat treat using controlled atmosphere which will produce parts confo
47、rming to surface contamination requirements. 3.5.1.2 Parts that will be machined after heat treatment, but which will have less than 0.020 inch (0.51 mm) of metal removed from any machined surface may be reclassified as Type 1, as described in 3.3.1, and need not meet the requirements of 3.5.1 as he
48、at treated, when it is demonstrated by tests (See 3.6.1.1) on each load that all surface contamination exceeding the requirements of 3.5.1 is removable from all machined surfaces, taking into account distortion after heat treatment. 3.5.1.3 Furnaces used exclusively to heat treat parts that will hav
49、e all contamination removed shall not require testing. 3.5.1.4 The heat treating processor shall be responsible for determining whether cumulative heat treating operations at that facility, as described in 3.5.1, have caused excessive surface contamination. 3.6 Test Methods Shall be in accordance with AMS2759 and as follows: 3.6.1 Surface Contamination Testing shall be performed by the microhardness method in accor
