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/AMS2769B AEROSPACE MATERIAL SPECIFICATION AMS2769 REV. B Issued 1996-02 Revised 2
5、009-12 Reaffirmed 2014-04 Superseding AMS2769A Heat Treatment of Parts in a Vacuum RATIONALE AMS2769B has been reaffirmed to comply with the SAE five-year review policy. 1. SCOPE 1.1 Purpose This specification establishes the requirements and procedures for heat treating parts (See 8.4) in a vacuum/
6、partial pressure. 1.2 Application This process has been used typically for the heat treatment of carbon and alloy steels, tool steels, corrosion-resistant steels, precipitation-hardening steels, super alloys, titanium, and other nonferrous alloys, but usage is not limited to such applications. 1.2.1
7、 Heat treatment as used in this specification includes solution treatment, homogenizing, austenitizing, annealing, normalizing, hardening, tempering, aging, and stress relieving. This specification does not cover processes such as melting, brazing, diffusion bonding, coating, carburizing, or nitridi
8、ng. 1.2.2 The objective of this process is to produce heat treated parts which are free from surface contamination and alloy depletion. Such parts may not necessarily have a bright surface. 1.3 Safety - Hazardous Materials While the materials, methods, applications, and processes described or refere
9、nced in this specification may involve the use of hazardous materials, this specification does not address the hazards which 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 materials and to take necessary prec
10、autionary measures to ensure the health and safety of all personnel involved. SAE INTERNATIONAL AMS2769B Page 2 of 19 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 suppli
11、er 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 specified, the last published issue of that document shall apply. 2.1 SAE Publications Available from SAE Internation
12、al, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. AMS2750 Pyrometry ARP1962 Training and Approval of Heat-Treating Personnel 2.2 ASTM Publications Available from ASTM International, 100 Barr Harbor Drive, P.O.
13、 Box C700, West Conshohocken, PA 19428-2959, Tel: 610-832-9585, www.astm.org. ASTM MNL 12 Manual on the Use of Thermocouples in Temperature Measurement 2.3 National Fire Protection Association (NFPA) Available from the National Fire Protection Agency, 1 Batterymarch Park, Quincy, MA 02169-7471, Tel:
14、 617-770-3000, www.nfpa.org. NFPA 86D Standard for Industrial Furnaces Using Vacuum as an Atmosphere 2.4 CGA Publications Available from Compressed Gas Association, Inc., 4221 Walney Road, 5thFloor, Chantilly, VA 20151-2923, Tel: 703-788-2700, . CGA G-5.3 Commodity Specification for Hydrogen CGA G-9
15、.1 Commodity Specification for Helium CGA G-10.1 Commodity Specification for Nitrogen CGA G-11.1 Commodity Specification for Argon 3. TECHNICAL REQUIREMENTS 3.1 Furnace Equipment The equipment shall conform to the requirements of applicable heat treat specifications. The furnace components shall res
16、ult in no detrimental metallurgical effects on the material processed during a normal production run as a result of vaporization or chemical reaction between the furnace components and the gases used to maintain partial pressure in the furnace. 3.1.1 Vacuum System The vacuum pumping system shall hav
17、e sufficient pumping capacity to evacuate the furnace to a pressure within the recommended range indicated in Table 1 for the materials being processed, and to maintain the desired level of vacuum during the entire heat treating process, including periods when a partial pressure is maintained using
18、a controlled flow of inert gas. SAE INTERNATIONAL AMS2769B Page 3 of 19 3.1.1.1 Vacuum Sensing Equipment The vacuum furnace shall be equipped with at least one gauge capable of sensing and recording the pressure in the vacuum heating chamber of the furnace at any point within the equipment operating
19、 temperature range required for the material and processing being performed. Vacuum sensing equipment shall be calibrated or adjusted in accordance with manufacturers specification. Recommended gauges are shown in Table 2. 3.1.1.2 Vacuum Gauge Calibration The method of vacuum gauge calibration shall
20、 be in accordance with manufacturers specification and be acceptable to purchaser. For furnaces used for processing materials at pressures of 1 10-3torr (0.13 Pa) or lower, vacuum gauges shall be calibrated every three months; otherwise vacuum gauges shall be calibrated at least annually, unless con
21、ditions necessitate more frequent calibrations. 3.1.1.3 Leak Rate Leak testing shall be performed weekly at ambient or elevated temperature. The leak rate shall not exceed the maximum permissible rate specified in Table 3 at a chamber pressure of 50 microns (50 m) or lower. Initial leak rate shall b
22、e determined after closing the vessel and evacuation to at least 50 microns (50 m). After reaching the initial evacuation level setpoint for the process being performed, all valves to the vessel chamber shall be closed, the initial pressure recorded, and a second reading of pressure made not less th
23、an 15 minutes after the first reading. Leak rate is determined by dividing the rise in pressure (difference between final reading and initial reading) by the test time in hours. Leak rate is expressed as microns (m) per hour. 3.1.1.4 As an alternative to the test of 3.1.1.3 vacuum furnaces which hav
24、e an integral oil tank shall pass a surface contamination test in accordance with the following requirements: 3.1.1.4.1 Furnaces for heating steel 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
25、or nitriding or to prevent total decarburization. 3.1.1.4.2 Carbon and low-alloy steels heat treated to minimum tensile strength levels below 220 ksi (1517 MPa) shall meet the surface contamination requirements of AMS2759/1. Steels heat treated to minimum tensile strength levels of 220 ksi (1517 MPa
26、) and higher shall meet the applicable surface contamination requirements of AMS2759/2. 3.1.1.4.3 Furnaces equipped with integral oil quench tanks shall not be permitted for processing titanium and titanium alloys above 1000 F (538 C), or for processing corrosion-resistant steels above 1100 F (593 C
27、), unless appropriate tests such as a surface contamination tests as in paragraph 3.1.1.4. are conducted to ensure no detrimental surface effects are caused by such treatments. 3.1.1.4.4 Heat treated titanium and titanium alloy parts shall meet the applicable surface contamination requirements of AM
28、S2801. For heat treat loads containing small parts (e.g. fastener components) such parts may be substituted for the coupons specified in paragraph 3.1.2.2.5. 3.1.1.4.5 Heat treated precipitation hardening corrosion resistant and maraging steels shall meet the applicable surface contamination require
29、ments of AMS2759/3. Austenitic corrosion resistant steels shall meet the applicable surface contamination requirements of AMS2759/4. Martensitic corrosion-resistant steels shall meet the applicable surface contamination requirements of AMS2759/5. 3.1.1.4.6 Surface contamination tests shall be carrie
30、d out weekly unless the referenced standard requires more frequent testing. 3.1.1.5 In addition to the tests specified in paragraphs 3.1.1.3 and 3.1.1.4, test for surface contamination on damage tolerant or fracture critical parts shall be performed on each lot to the requirements stated in 3.1.1.4.
31、1, 3.1.1.4.2, 3.1.1.4.3, 3.1.1.4.5 and 3.1.1.4.6. It is the responsibility of the purchaser to inform the heat treater on the drawing, contract, or purchase order that parts are damage tolerant or fracture critical. SAE INTERNATIONAL AMS2769B Page 4 of 19 3.1.2 Pyrometry Shall conform to AMS2750. 3.
32、1.2.1 Working Thermocouples Thermocouples shall be suitably protected and be of a type compatible with the range of temperatures and vacuum conditions used. They shall be of a suitable size and located such that they receive direct radiation from the heating elements and furnace walls. 3.1.2.1.1 The
33、 thermocouple types shown in Table 4 shall not be used unprotected (base wire, i.e., other than protective sheathed) above the temperatures shown in Table 4. 3.1.2.1.2 Use of other thermocouple types shall be approved by the cognizant engineering organization. TABLE 1 RECOMMENDED VACUUM RANGE AS A F
34、UNCTION OF PROCESSING TEMPERATURE RANGE FOR VARIOUS PURE METALS AND ALLOYS Material Processing Range F Processing Range C Operating Range (Microns)(6)(7)(8)(9)Carbon and Alloy Steels(10)1000 to 1800 538 to 982 1 to 200(1)Corrosion-Resistant Steels(10)Ferritic (12 to 17% Cr) Martensitic Austenitic Pr
35、ecipitation Hardening 1200 to 1650 1200 to 2050 1750 to 2050 850 to 2150 649 to 899 649 to 1121 954 to 1121 454 to 1177 1 to 200(1)1 to 200(1)(3)1 to 200(1)1 to 200(1)(3)Super Alloys(10)Nickel Alloys Cobalt Alloys Iron Alloys 1150 to 2275 1350 to 2250 1600 to 2150 621 to 1246 732 to 1232 871 to 1177
36、 0.1 to 100(2)(3)0.1 to 100(2)(3)0.1 to 200(2)(3)Tool Steels(10)Air Hardening Cold Work Hot Work High Speed (M Series) High Speed (T Series) 1470 to 1850 1470 to 1950 1470 to 1900 1470 to 2250 1550 to 2375 799 to 1010 799 to 1066 799 to 1038 799 to 1232 843 to 1302 0.1 to 200(1)0.1 to 200(1)0.1 to 2
37、00(1)0.1 to 200(1)0.1 to 200(1)Refractory Metals Molybdenum, Tungsten Columbium (Niobium) Tantalum Above 1600 Above 871 0.01 to 0.1 0.01 to 0.1(4)0.01 to 0.1(4)Titanium and Titanium Alloys 1300 and below Above 1300 704 and below Above 704 0.1 to 100(2)(4)0.01 to 1(3)(4)Copper Alloys(5)Below 1000 100
38、0 to 2100 Below 538 538 to 1149 10 to 400 100 to 400 Notes: (1) For pressures higher than 100 microns, partial pressures of approved gases are required (See 3.2.1). (2) For pressures higher than 20 microns, partial pressures of approved gases are required (See 3.2.1). (3) Nitrogen not permitted as a
39、 partial pressure gas above 1400 F (760 C). (4) Hydrogen not permitted as a partial pressure or quench gas. (5) Alloys containing zinc - not recommended. (6) For clarity, the single vacuum term “micron” is used. See 8.2.17 for relation to other values commonly used. (7) If pressures outside the reco
40、mmended ranges are used, tests shall be performed to demonstrate that no detrimental alloy depletion/enrichment has occurred. (8) The pressures specified apply to vacuum furnaces not equipped for atmosphere circulation. (9) For furnaces equipped with atmosphere circulation, partial pressures higher
41、than those indicated may be used at temperatures below 1000 F (538 C). (10) At temperatures 2100 F (1149 C) and below, minimum pressure may be 1/10 of the value shown. SAE INTERNATIONAL AMS2769B Page 5 of 19 TABLE 2 - VACUUM LEVEL VERSUS RECOMMENDED GAUGE Vacuum Level Gauge 10-6micron to 1 micron 10
42、-4micron to 10 microns 1 micron to 103microns (1 torr) Hot filament ionization Cold cathode ionization Thermocouple or Pirani TABLE 3 MAXIMUM PERMISSIBLE LEAK RATE FOR PROCESSING OF VARIOUS METALS Material Leak Rate Microns/Hour Carbon and Alloy Steels 50 Corrosion-Resistant Steels Ferritic (12 to 1
43、7% Cr) Martensitic Austenitic Precipitation Hardening 50 50 50 50 Superalloys Nickel Alloys Cobalt Alloys Iron Alloys 20 20 20 Tool Steels Air Hardening Cold Work Hot Work High Speed (M Series) High Speed (T Series) 50 50 50 50 50 Refractory Metals Molybdenum, Tungsten Columbium (Niobium) Tantalum 2
44、0 5 5 Titanium and Titanium Alloys 10 Copper Alloys 50 TABLE 4 - BARE THERMOCOUPLE TYPES VERSUS MAXIMUM OPERATING TEMPERATURE Type Maximum Temperature F Maximum Temperature C K (Chromel-Alumel) (1)(2)N (Nicrosil-Nisil)(1)Nickel-Nickel/Molybdenum S,R (Platinum-Platinum/Rhodium) B (Platinum/Rhodium-Pl
45、atinum/Rhodium) Tungsten-Tungsten/Rhenium 2200 2200 2300 2600 3100 4000 1204 1204 1260 1427 1704 2204 Notes: (1) Bare thermocouples shall be discarded or recalibrated after being exposed to five heat treat cycles or accumulation of five hours service at or above 2100 F (1149 C), or ten heat treat cy
46、cles or accumulation of 10 hours service at 2000 to 2100 F (1093 to 1149 C). (2) Type K bare thermocouples exposed to vacuum are not recommended for use as control thermocouples for continuous service at temperatures above 1800 F (982 C).3.1.2.1.3 The recommendations of ASTM MNL 12 shall be consider
47、ed with respect to usage of thermocouples. 3.1.2.1.4 When used in metal or other sheaths, care shall be taken to ensure that no chemical reaction between the sheath and the thermocouple wire can occur. SAE INTERNATIONAL AMS2769B Page 6 of 19 3.1.3 Quenching Furnaces used for quenching shall be equip
48、ped with cooling means sufficient for the material and process being performed. 3.1.3.1 Vacuum Cooling Where there is a requirement for slow cooling after annealing or normalizing, cooling performed under vacuum or partial pressure using inert gas is permissible. Controlled cooling using a programme
49、d heat input is permitted provided load thermocouples are used to measure the actual load temperature during the cooling period. 3.1.3.2 Gas Quenching When gas quenching is specified, it shall be accomplished by backfilling the furnace with a gas which has no detrimental metallurgical effect on the material being processed or on the furnace equipment. The system and the pressure of the bac
