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 reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2010 SAE International All rights reserved. No part of this publication m
3、ay 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: +1 724-776-4970 (outside U
4、SA) 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/AMS2768C AEROSPACE MATERIAL SPECIFICATION AMS2768 REV. C Issued 2005-08 Revised 2010-07Supers
5、eding AMS2768B Heat Treatment of Magnesium Alloy Castings RATIONALE AMS2768C corrects footnotes to Table 3. 1. SCOPE 1.1 Purpose This specification covers the engineering requirements for heat treatment of magnesium alloy castings and for parts machined from castings. 1.2 Application This specificat
6、ion is applicable to castings of the following magnesium alloys: AM100A AZ63A AZ81A AZ91C AZ91E AZ92A EQ21A EV31A EZ33A QE22A ZE41A WE43A WE43B WE54A ZK51A ZK61A 1.3 When AMS2768 is specified and specific heat treat processing instructions are included in the material specification, the equipment an
7、d control requirements of AMS2768 shall apply. For alloys not specifically covered, the applicable provisions of this specification shall be invoked but temperatures, times, and quench procedures shall be as specified by the cognizant engineering organization. 1.4 It is permissible, for specific par
8、ts, to use equipment, practices and test methods which conformed to AMS-M-6857 and were previously acceptable to the purchaser. 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.
9、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 specified, the last published issue of that document shall apply. SAE AMS2768C Page 2 of 11 2.1 SAE Publica
10、tions 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. AMS2750 Pyrometry AMS3025 Polyalkylene Glycol Heat Treat Quenchant ARP1962 Training and Approval of Heat-Treating Personnel
11、 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 B 557 Methods of Tension Testing Wrought and Cast Aluminum and Magnesium Alloy Products 3. TECHNICAL REQUIREMENTS 3.1 Equipment Equi
12、pment used for thermal processing shall conform to the requirements of this specification and AMS2750, except (1) requirements for working zone controls, instruments and sensors shall apply to all heating zones and (2) recordings from instruments may be stored on magnetic or optical media providing
13、a hard copy is available on request. 3.1.1 Pyrometry Shall meet the requirements of AMS2750. 3.1.2 Furnaces 3.1.2.1 Heating Media Shall be air, protective atmosphere, combustible gases, or fluidized bed. Electrical heating elements and radiant tubes shall be shielded to prevent direct radiation from
14、 striking any part. The furnace products of combustion in the furnace, and the composition and maintenance of fluidized beds shall be such as to prevent attack or contamination of the parts, or impingement of the flame on the work. 3.1.2.2 Temperature Uniformity The design and construction of the fu
15、rnaces shall be such that the temperature in the working zone is capable of being maintained within 10 F (6 C) of the desired heat treating temperature after the charge has been brought up to temperature. At no time shall the temperature in any part of the working zone exceed the maximum permissible
16、 temperature for the alloy being heat treated (See Table 1). SAE AMS2768C Page 3 of 11 3.1.3 Quenching Unless otherwise approved by the cognizant engineering organization, the following provisions apply. Equipment shall be provided for quenching in water, air blast, spray, oil, or in polymer quencha
17、nts and for measuring quenchant temperature. Provisions shall be made for mechanical, hydraulic, or air agitation of the immersion quenching medium, or agitation of the parts, or both and for heating or cooling of the quenchant, as required. Air agitation of immersion quenchants shall be allowed, pr
18、ovided the air doesnt come in contact with the parts being quenched. Exception to the use of agitation is permitted provided that it has been demonstrated that the parts meet the specified properties in the final heat treated condition. The volume of quenching medium for immersion quenching shall be
19、 sufficient so that its temperature rise due to quenching meets the requirements of 3.2.8.3.1. Small parts heated and soaked in baskets may be quenched by dumping when basket loads are too heavy to allow adequate quenching by immersion of the full basket and provided that the parts are not damaged b
20、y dumping. Non immersion quench methods shall be documented and shall have demonstrated to produce the specified properties. 3.1.3.1 Polymer Quenchants Polyalkalene glycol shall meet the requirements of AMS3025. Other synthetics may be used provided that they have demonstrated not to be detrimental
21、to the material and that the parts meet the required specified properties in the final heat treated condition. Polymer concentration shall be established for the particular casting configuration prior to use. 3.1.4 Cleaning Equipment shall be provided to clean castings before heat treatment, and to
22、remove residual film from parts quenched in a polymer quenchant or oil from parts quenched or aged in oil baths. 3.2 Procedures 3.2.1 General Cast parts that require heat treatment to a T4X, T5X, or T6X temper shall be heat treated in accordance with Tables 1 and 2 (See 3.2.4). Heat treatment shall
23、be performed only on entire parts, never on a portion of a part. The process used to generate the necessary requirements shall be established and controlled for each part number to ensure that each lot of castings is treated in the same manner. 3.2.1.1 Rework Solution Cycles Castings requiring re-he
24、at treating may be solution heat treated using the cycles listed in Table 3 (See 8.2.2.1). 3.2.2 Racking and Spacing Product shall be supported or hung and spaced to permit flow of the heating and cooling media over all surfaces to ensure that the castings will meet the specified requirements. Writt
25、en instructions, drawings, photographs, etc. shall be used as necessary to ensure proper spacing. 3.2.2.1 Water Entrapment Racks and fixtures used for solution heat treatment shall be constructed to preclude entrapment of water. 3.2.3 Loading The furnaces shall be at or below the maximum solution tr
26、eating temperature when the parts are loaded. 3.2.4 Control instrument(s) shall be set within the temperature range specified in Table 1 for solution treating and should be set at the recommended temperature specified in Table 2 for aging. Sensor/control offsets, if used, shall comply with AMS2750.
27、SAE AMS2768C Page 4 of 11 3.2.5 Soaking Soaking time starts when all temperature control sensing elements are within 10 rF (6 C) of the set or offset temperature. 3.2.5.1 Interruptions during solution treatment are permitted provided the minimum soak time is met and at least a 2-hour soak time occur
28、s after the interruption. During aging treatments a maximum of four interruptions are permitted for removal or loading of parts. The time between door opening and furnace or load thermocouple recovery is not to be counted as part of the total aging time. 3.2.6 Logs A record (written or electronic st
29、orage media), traceable to temperature recording information (chart(s) or electronic storage media) and to shop travelers or other documentation, shall be kept for each furnace and load. The information on the combination of documents shall include: equipment identification, approved personnels iden
30、tification, date, part number or product identification, number of parts, alloy, lot identification, AMS2768C or other applicable specification, actual thermal processing times and temperatures used. When applicable, atmosphere control parameters, quench delay, quenchant type, polymer concentration
31、and quenchant temperature shall also be recorded. The maximum thickness, when process parameters are based on thickness, shall be recorded and shall be taken as the minimum dimension of the heaviest section of the part. The log data shall be recorded in accordance with the heat treaters documented p
32、rocedures. 3.2.7 Cleaning Prior to heat treatment, parts shall be cleaned to assure that there will be no adverse effects to the surfaces following heat treatment. Residue from heating and quenching media shall be removed from parts after heat treatment. 3.2.8 Solution Heat Treating 3.2.8.1 Temperat
33、ure Cast parts that require solution heat treatment shall be soaked within the temperature ranges specified in Table 1. 3.2.8.1.1 For solution heat treating AZ63A (type 1 and 2), AZ81A, AZ91C, AZ91E, AZ92A (type 1), AM100A, and ZK61A, the castings shall be heated slowly to prevent eutectic melting w
34、hich is cause for rejection. Incremental steps or a uniform heating rate, which requires at least 2 hours to raise the temperature from 640 F (338 C) to the heat treating temperature, shall be used (See 8.5). 3.2.8.1.2 AZ92A (type 2) and QE22A may be charged into the furnace which is at the heat tre
35、ating temperature. 3.2.8.1.3 Evidence of high temperature oxidation shall be cause for rejection (See 3.4.2.1). A protective atmosphere containing sufficient sulfur dioxide, carbon dioxide, or satisfactory oxidation inhibitor shall be used when solution heat treating at or above 750 F (399 C) (See 8
36、.3). 3.2.8.2 Soaking Time The castings shall be held at temperature for a sufficient time to secure adequate solution heat treatment. Recommended soaking times at temperature for castings up to 1 inch (25.4 mm) thickness are provided in Table 1. A longer soaking time may be required for castings wit
37、h heavier sections. SAE AMS2768C Page 5 of 11 3.2.8.3 Quenching Parts, after being soaked at the solution heat treating temperature for the required time, shall be quenched. 3.2.8.3.1 Immersion Quenchant Temperature During the quench, the quenchant temperature shall not rise more than 25 rF (14 C).
38、To prevent excessive warpage and possible cracking, castings may be quenched in oil or water with temperature varying from cold to hot (212 rF or 100 C) or in a polymer quenchant at room temperature providing it is substantiated that the combination of quench and solution temperature will produce me
39、chanical properties meeting the material specification. Exceptions to the temperature rise are permitted provided that it has been demonstrated by testing and documentation that the parts meet the required specified properties in the final heat treated condition. 3.2.8.3.2 Immersion Quench Delay Tim
40、e The quench delay time shall not exceed 30 seconds. The delay shall be measured from the time the furnace door of an air furnace starts to open, or the first portion of the load emerges from a fluidized bed, to complete immersion of the load in the quenchant. This delay time may be exceeded providi
41、ng that the cooling rate does not result in a loss of any mechanical property typically obtained by the established process for that casting configuration. 3.2.8.3.3 Quenchant Contact Time Castings which are quenched by immersion shall be kept immersed in the quenchant for not less than 2 minutes pe
42、r inch of thickness, or fraction thereof in the thickest section. Alternatively, castings shall be kept immersed in the quenchant for not less than 2 minutes after boiling ceases. Parts quenched in boiling water shall remain immersed for not less than 2 minutes. Castings quenched in an air blast or
43、spray shall remain in contact with the quench media until surface temperatures are reduced to 212 rF (100 C). 3.2.9 Aging Precipitation heat treatment or artificial aging, when T5 or T6 tempers are specified, shall be performed at the temperature and times required to develop the specified propertie
44、s. Aging conditions which have been used satisfactorily are shown in Table 2. No protective atmosphere is required. 3.2.10 Straightening after final aging is prohibited unless otherwise specified by the cognizant engineering organization. 3.3 Qualification 3.3.1 Suppliers Facilities performing heat
45、treatment in accordance with this specification shall be subject to approval by the cognizant quality assurance organization (See 8.2.7). 3.3.2 Personnel All responsible heat treating personnel at leadsman and foreman levels performing heat treatment in accordance with this specification shall be qu
46、alified as specified in 4.5. 3.4 Acceptance 3.4.1 The routine operation of the equipment and heat treating procedure shall be judged by the mechanical properties obtained on the test bars heat treated with every furnace charge and tested in accordance with ASTM B 557. SAE AMS2768C Page 6 of 11 3.4.2
47、 Microscopic Examination The tensile test may be supplemented by a microscopic examination of the test bars or selected castings at the discretion of the cognizant engineering organization. At least one representative sample for each of the specified tests shall be taken. If the furnace selected for
48、 routine inspection contains a load which is homogeneous as to alloy, form and size of part, two specimens shall be selected to represent the least massive and the most massive portions of the charge. In the event of a nonhomogeneous load as to type of alloy, and when the recommended heat treatments
49、 for the respective alloys differ, additional samples shall be prepared. 3.4.2.1 Eutectic Melting and High Temperature Oxidation Specimens from the heat treated samples shall be prepared for microscopic examination. The unetched surface shall be examined at 500X minimum magnification with a metallurgical microscope. The presence of eutectic melting or high temperature oxidation shall be considered evidence of improper heat tre
