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 theref
2、rom, 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 InternationalAll rights reserved. No part of this publi
3、cation 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: +1 724-776-4970 (out
4、side USA)Fax: 724-776-0790Email: CustomerServicesae.orgSAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedbackon this Technical Report, please visithttp:/www.sae.org/technical/standards/AMS6491EAEROSPACE MATERIAL SPECIFICATIONAMS6491 REV. EIssued 1976-01Revised 2014-05Supersedin
5、g AMS6491DSteel Bars, Forgings, and Tubing4.1Cr - 4.2Mo - 1.0V (0.80 - 0.85C) (M-50)Premium Aircraft-Quality for Bearing Applications, Double Vacuum Melted(Composition similar to UNS T11350)RATIONALEAMS6491E results from a Five Year Review and update of this specification.1. SCOPE1.1 FormThis specif
6、ication covers a premium aircraft-quality, low-alloy steel in the form of bars, forgings, mechanical tubing, and forging stock.1.2 ApplicationThese products have been used typically for parts, such as bearings operating under heavy loads and high speeds at moderate temperatures and subject to very r
7、igid inspection standards, but usage is not limited to such applications.2. APPLICABLE DOCUMENTSThe 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 work to a subsequent revision of a docu
8、ment 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 PublicationsAvailable from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096
9、-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.AMS2251 Tolerances, Low-Alloy Steel BarsAMS2253 Tolerances, Carbon and Alloy Steel TubingAMS2259 Chemical Check Analysis Limits, Wrought Low-Alloy and Carbon SteelsAMS2300 Steel Cleanliness, Premium Aircraft-
10、Quality, Magnetic Particle Inspection ProcedureSAE INTERNATIONAL AMS6491E Page 2 of 8AMS2370 Quality Assurance Sampling and Testing, Carbon and Low-Alloy Steel Wrought Products and Forging StockAMS2372 Quality Assurance Sampling and Testing, Carbon and Low-Alloy Steel ForgingsAMS2375 Control of Forg
11、ings Requiring First Article ApprovalAMS2806 Identification, Bars, Wire, Mechanical Tubing, and Extrusions, Carbon and Alloy Steels and Corrosion andHeat-Resistant Steels and AlloysAMS2808 Identification, ForgingsAS1182 Standard Stock Removal Allowance, Aircraft-Quality and Premium Aircraft-Quality
12、Steel Bars and Mechanical Tubing2.2 ASTM PublicationsAvailable from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959,Tel: 610-832-9585, www.astm.org.ASTM A 370 Mechanical Testing of Steel ProductsASTM A 604 Macroetch Testing of Consumable Electrode Remelted
13、Steel Bars and BilletsASTM E 45 Determining the Inclusion Content of SteelASTM E 112 Determining Average Grain SizeASTM E 350 Chemical Analysis of Carbon Steel, Low-Alloy Steel, Silicon Electrical Steel, Ingot Iron, and Wrought IronASTM E 384 Knoop and Vickers Hardness of Materials3. TECHNICAL REQUI
14、REMENTS3.1 CompositionShall conform to the percentages by weight shown in Table 1, determined by wet chemical methods in accordance with ASTM E 350, by spectrochemical methods, or by other analytical methods acceptable to purchaser.TABLE 1 - COMPOSITIONElement min maxCarbon 0.80 0.85Manganese 0.15 0
15、.35Silicon - 0.25Phosphorus - 0.015Sulfur - 0.008Chromium 4.00 4.25Molybdenum 4.00 4.50Vanadium 0.90 1.10Nickel - 0.15Cobalt - 0.25Tungsten - 0.25Copper - 0.103.1.1 Check AnalysisComposition variations shall meet the applicable requirements of AMS2259.SAE INTERNATIONAL AMS6491E Page 3 of 83.2 Meltin
16、g PracticeSteel shall be double vacuum melted, using vacuum induction melting practice followed by vacuum consumable electrode remelting.3.3 ConditionThe product shall be supplied in the following condition; hardness and tensile strength shall be determined in accordance with ASTM A 370:3.3.1 BarsBa
17、r shall not be cut from plate (Also see 4.5.2).3.3.1.1 Bars 0.500 inch (12.70 mm) and Under in Nominal Diameter or Least Distance Between Parallel SidesCold finished and sheroidized annealed, having tensile strength not higher than 120.0 ksi (825 MPa), or equivalent hardness (See 8.2).3.3.1.2 Bars O
18、ver 0.500 inch (12.70 mm) in Nominal Diameter or Least Distance Between Parallel SidesHot finished and sheroidized annealed, unless otherwise ordered, having hardness not higher than 229 HB, or equivalent (See 8.3). Bars ordered cold finished may have hardness as high as 248 HB, or equivalent (See 8
19、.3).3.3.2 ForgingsAs ordered.3.3.3 Mechanical TubingCold finished, unless otherwise ordered, having hardness not higher than 25 HRC, or equivalent (See 8.3). Tubing ordered hot finished and annealed shall have hardness not higher than 99 HRB, or equivalent (See 8.3).3.3.4 Forging StockAs ordered by
20、the forging manufacturer.3.4 PropertiesThe product shall conform to the following requirements; hardness testing shall be performed in accordance with ASTM A 370:3.4.1 MacrostructureVisual examination of transverse sections from bars, billets, tube rounds, and forging stock, etched in hot hydrochlor
21、ic acid in accordance with ASTM A 604, shall show no pipe or cracks. Porosity, segregation, inclusions, and other imperfections shall be no worse than the macrographs of ASTM A 604 shown in Table 2.TABLE 2 - MACROSTRUCTURE LIMITSClass Condition Severity1Freckles A2 White Spots A3 Radial Segregation
22、B4 Ring Pattern B3.4.2 Micro-Inclusion Rating of Each HeatNo specimen shall exceed the limits of Table 3, determined in accordance with ASTM E 45, Method D.SAE INTERNATIONAL AMS6491E Page 4 of 8TABLE 3 - MICRO-INCLUSION RATING LIMITSTypeAThinAHeavyBThinBHeavyCThinCHeavyDThinDHeavyWorst Field Severit
23、y 1.5 1.0 1.0 1.0 1.0 1.0 1.5 1.0Worst Field Frequency, maximum a 1 a 1 a 1 3 1Total Rateable Fields,Frequency, maximumb b 1b1 81a - Combined A+B+C, not more than 3 fieldsb - Combined A+B+C, not more than 8 fields3.4.2.1 A rateable field is defined as one that has a type A, B, C, or D inclusion rati
24、ng of at least No. 1.0 thin or heavy in accordance with ASTM E 45.3.4.3 Response to Heat TreatmentSpecimens as in 4.3.3 protected by suitable means or treated in a neutral atmosphere or neutral salt to minimize scaling and prevent either carburization or decarburization, shall have substantially uni
25、form hardness not lower than 60 HRC after being heated to 2025 to 2050 F (1107 to 1121 C) by any convenient means, held to equalize at temperature, and either quenched into salt bath at 1100 to 1150 F (593 to 621 C), held in salt bath for 2 minutes 0.2, and air cooled to room temperature or directly
26、 air cooled to room temperature, and tempered for 2 hours 0.25 at 1000 to 1025 F (538 to 552 C).3.4.4 Average Grain Size of Bars, Forgings and TubingShall be ASTM No. 7 or finer, determined in accordance with ASTM E 112 after austenitizing and quenching as in 3.4.3.3.4.5 Decarburization3.4.5.1 Bars
27、and tubing ordered ground, turned, or polished shall be free from decarburization on the ground, turned, or polished surfaces. Decarburization on tubing ID shall not exceed the maximum depth specified in Table 5.3.4.5.2 Allowable decarburization of bars, billets, and tube rounds ordered for redrawin
28、g or forging or to specified microstructural requirements shall be as agreed upon by purchaser and vendor.3.4.5.3 Decarburization of bars to which 3.4.5.1 or 3.4.5.2 is not applicable shall be not greater than shown in Table 4.TABLE 4A - MAXIMUM TOTAL DEPTH OF DECARBURIZATION, INCH/POUND UNITSNomina
29、l Diameter or DistanceBetween Parallel SidesInchesTotal Depth ofDecarburizationInchUp to 0.500, incl 0.015Over 0.500 to 1.000, incl 0.030Over 1.000 to 2.000, incl 0.040Over 2.000 to 3.000, incl 0.050Over 3.000 to 4.000, incl 0.065Over 4.000 to 5.000, incl 0.095SAE INTERNATIONAL AMS6491E Page 5 of 8T
30、ABLE 4B - MAXIMUM TOTAL DEPTH OF DECARBURIZATION, SI UNITSNominal Diameter or DistanceBetween Parallel SidesMillimetersTotal Depth ofDecarburizationMillimetersUp to 12.50, incl 0.38Over 12.50 to 25.00, incl 0.75Over 25.00 to 50.00, incl 1.00Over 50.00 to 75,00, incl 1.25Over 75.00 to 100.00, incl 1.
31、65Over 100.00 to 125.00, incl 2.403.4.5.4 Decarburization of all tubing to which 3.4.5.1 or 3.4.5.2 is not applicable shall be not greater than shown in Table 5.TABLE 5A - MAXIMUM TOTAL DEPTH OF DECARBURIZATION, INCH/POUND UNITSNominalOutside DiameterInchesTotal Depth ofDecarburizationInchUp to 1.00
32、0, incl 0.025Over 1.000 to 2.000, incl 0.035Over 2.000 to 3.000, incl 0.045Over 3.000 to 4.000, incl 0.055Over 4.000 to 5.000, incl 0.080TABLE 5B - MAXIMUM TOTAL DEPTH OF DECARBURIZATION, SI UNITSNominalOutside DiameterMillimetersTotal Depth ofDecarburizationMillimetersUp to 25.00, incl 0.62Over 25.
33、00 to 50.00, incl 0.88Over 50.00 to 75.00, incl 1.12Over 75.00 to 100.00, incl 1.40Over 100.00 to 125.00, incl 2.003.4.5.5 Decarburization shall be measured by the microscopic method or by the microhardness traverse method using microhardness testing in accordance with ASTM E 384. The microhardness
34、method shall be conducted on ahardened but untempered specimen protected during heat treatment to prevent changes in surface carbon content. Depth of decarburization, when measured by the microhardness method, is defined as the perpendicular distance from the surface to the depth under that surface
35、where there is no further increase in hardness. Such measurements shall be far enough away from any adjacent surface to be uninfluenced by decarburization on the adjacent surface. In case of dispute, the depth of decarburization determined using the microhardness traverse method shall govern.3.4.5.5
36、.1 When determining the depth of decarburization, it is permissible to disregard local areas provided the decarburization of such areas does not exceed the above limits by more than 0.005 inch (0.13 mm) and the width is 0.065 inch (1.65 mm) or less.3.5 QualityThe product, as received by purchaser, s
37、hall be uniform in quality and condition, sound, and free from foreign materials and from imperfections detrimental to usage of the product.SAE INTERNATIONAL AMS6491E Page 6 of 83.5.1 Steel shall be premium aircraft-quality conforming to AMS2300.3.5.2 Bars and mechanical tubing ordered hot rolled or
38、 cold drawn, or ground, turned, or polished shall, after removal of the standard stock removal allowance in accordance with AS1182, be free from seams, laps, tears, and cracks open to the machined, ground, turned, or polished surface.3.5.3 Grain flow of die forgings, except in areas that contain fla
39、sh-line end grain, shall follow the general contour of the forgings showing no evidence of reentrant grain flow.3.6 Tolerances3.6.1 BarsIn accordance with AMS2251.3.6.2 Mechanical TubingIn accordance with AMS2253.4. QUALITY ASSURANCE PROVISIONS4.1 Responsibility for InspectionThe vendor of the produ
40、ct shall supply all samples for vendors tests and shall be responsible for the performance of allrequired tests. Purchaser reserves the right to sample and to perform any confirmatory testing deemed necessary to ensure that the product conforms to specified requirements.4.2 Classification of Tests4.
41、2.1 Acceptance TestsComposition (3.1), condition (3.3), macrostructure (3.4.1), micro-inclusion rating (3.4.2), response to heat treatment (3.4.3), average grain size (3.4.4), decarburization (3.4.5), and tolerance (3.6) are acceptance tests and shall be performed on each heat or lot as applicable.4
42、.2.2 Periodic TestsFrequency-severity rating (3.5.1) and grain flow of die forgings (3.5.3) are periodic tests and shall be performed at a frequency selected by the vendor unless frequency of testing is specified by purchaser.4.3 Sampling and Testing4.3.1 Bars, Forging Stock, and Mechanical TubingIn
43、 accordance with AMS2370.4.3.2 ForgingsIn accordance with AMS2372.4.3.3 Specimens for response to heat treatment (3.4.3) shall be taken midway between surface and center of samples representing the top and bottom of each remelted ingot involved in the lot obtained from semi-finished or finished prod
44、uct. The surface to be tested shall be ground sufficiently to remove any surface condition, scale, carburization, or decarburization that might affect readings.4.3.3.1 Alternately, the specimen may be obtained from the finished lot.SAE INTERNATIONAL AMS6491E Page 7 of 84.4 ApprovalWhen specified, ap
45、proval and control of forgings shall be in accordance with AMS2375.4.5 Reports4.5.1 The producer of bars, forgings and tubing shall furnish with each shipment a report showing the producer identity, country where the metal was melted (e. g., final melt in the case of metal processed by multiple melt
46、ing operations), and the results of tests for composition, macrostructure, micro-inclusion rating for each heat and for response to heat treatment for each heat (or lot See 4.3.3.1), and for condition (hardness or tensile strength) and average grain size of each lot, and stating that the product con
47、forms to the other technical requirements. This report shall include the purchase order number, heat and lot numbers, AMS6491E, product form and size or part number, and quantity. If forgings are supplied, the size and melt source of stock used to make the forgings shall also be included.4.5.2 Repor
48、t the nominal metallurgically worked cross sectional size and the cut size, if different (Also see 3.3.1).4.5.3 The producer of forging stock shall furnish with each shipment a report showing the producer identity, country where the metal was melted (e. g., final melt in the case of metal processed
49、by multiple melting operations), and the results of tests for composition, macrostructure, micro-inclusion rating for each heat and for response to heat treatment for each heat (or lot See 4.3.3.1). This report shall include the purchase order number, heat number, AMS6491E, size and quantity.4.6 Resampling and Retesting4.6.1 Bars, Forging Stock, and Mechanical TubingIn accordance with AMS2370.4.6.2 ForgingsIn accordance wi
