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1、BRITISH STANDARD AEROSPACE SERIES CONFIRMED AUGUST 1985 BS S 157: 1976 (Superseding BS 3S 107) Incorporating Amendment No. 1 Specification for 3 % nickel-chromium- molybdenum case-hardening steel billets, bars, forgings and parts (11801380 MPa) UDC 629.7:669.15242628:669.14.018.298.2 Licensed Copy:
2、London South Bank University, London South Bank University, Sat Dec 09 02:58:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS S 157:1976 This British Standard, having been prepared under the direction of the Aerospace Standards Committee, was published under the authority of the Executive Board on 3
3、0 April 1976 BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference ACE/15 Draft for comment 75/72488 DC ISBN 0 580 09443 X A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible
4、 for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 and 2 and a back cover. This standard has been updated (see copyright d
5、ate) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No.Date of issueComments 3521August 1981Indicated by a sideline in the margin Licensed Copy: London South Bank University, London South Ban
6、k University, Sat Dec 09 02:58:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS S 157:1976 BSI 01-2000i Contents Page 1Inspection and testing procedure1 2Manufacture1 3Chemical composition1 4Surface dressing1 5Condition1 6Heat treatment1 7Mechanical properties2 8Grain size2 Licensed Copy: London Sou
7、th Bank University, London South Bank University, Sat Dec 09 02:58:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:58:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS S 157:1976 BSI 01-20001 NOTEThe speci
8、fied chemical composition, heat treatment and tensile properties comply with AECMA Recommendation FE-PL71 (for material heat treated to a tensile strength of 1 180 1 380 MPa). 1 Inspection and testing procedure 1.1 General. This British Standard shall be used in conjunction with the relevant section
9、s of the latest issue of BS S 100 as follows: 1.2 Sulphur printing or deep etching tests. One sample shall be taken from each ingot for sulphur printing or deep etching tests. 2 Manufacture The material shall be manufactured by an electric process. 3 Chemical composition The steel shall contain: 4 S
10、urface dressing The material shall be overall dressed. 5 Condition 5.1 The material shall be supplied in the appropriate condition stated below: 5.2 Parts shall be supplied finally heat treated. 6 Heat treatment 6.1 Softening treatment. The softening treatment shall consist of heating uniformly at a
11、 temperature of not less than 630 C. 6.2 Final heat treatment 6.2.1 Except as provided in 6.2.2, the final heat treatment shall consist of the following: a) Carburizing or blank carburizing. Heat uniformly at a temperature between 880 C and 930 C. b) Hardening. Heat at a temperature of 825 10 C, fol
12、lowed by cooling in oil. c) Tempering. Heat at a temperature of 190 5 C, followed by cooling in air. 6.2.2 Alternatively to 6.2.1, the final heat treatment of parts shall be agreed between the manufacturer and the purchaser. NOTEIf an alternative heat treatment is used for parts, it may be necessary
13、 to agree alternative mechanical properties. Bars for machining delivered in other than the finally heat treated condition sections 1 and 2 Forging stock and billets and bars for subsequent working sections 1 and 5 Forgingssections 1 and 6 Parts finally heat treated after machining sections 1 and 7
14、Element % min.max. Carbon0.120.17 Silicon0.150.40 Manganese0.300.60 Phosphorus0.025 Sulphur0.020 Chromium0.81.1 Molybdenum0.200.30 Nickel3.03.5 DesignationFormCondition of supply S157BBlack bars for machining Softened S157DBright bars for machining Softened and subsequently cold drawn, cold rolled,
15、machined or ground S157AForging stock and billets and bars for subsequent working Softened S157CForgingsSoftened Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:58:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS S 157:1976 2 BSI 01-2000 7 Mechanical properti
16、es 7.1 Tensile test at room temperature and impact test. The mechanical properties obtained from test pieces, machined from test samples reduced, where applicable, to 20 mm diameter or square before heat treatment, shall be as follows: 7.2 Hardness test. The hardness of material heat treated in acco
17、rdance with 6.1 shall be not greater than 241 HB. 8 Grain size The grain size shall be determined in accordance with BS 4490 “Methods for the determination of the austenitic grain size of steel”, method 1, and shall be not coarser than no. 5. 0.2 % proof stress Tensile strengthElongation Izod impact
18、 min.min.max.min.min. MPa (= N/mm2) MPa (= N/mm2) MPa (= N/mm2) %ft lbf 9301 1801 380825 NOTEInformation on SI units is given in BS 3763 “The International Systems of units (SI)” and BS 350 “Conversion factors and tables”. Licensed Copy: London South Bank University, London South Bank University, Sa
19、t Dec 09 02:58:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI blank Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 02:58:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS S 157: 1976 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI i
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