1、BRITISH STANDARD AEROSPACE SERIES CONFIRMED AUGUST 1985 BSS157: 1976 (Superseding BS3S107) Incorporating Amendment No. 1 Specification for 3% nickel-chromium- molybdenum case-hardening steel billets, bars, forgings andparts (11801380 MPa) UDC 629.7:669.15242628:669.14.018.298.2BSS157:1976 This Briti
2、sh Standard, having been prepared under the directionof the Aerospace Standards Committee, was published under the authority ofthe Executive Board on 30April1976 BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference ACE/15 Draft for comment 75/72488 DC ISB
3、N 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 for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This doc
4、ument comprises a front cover, an inside front cover, pages i and ii, pages1 and 2 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publicat
5、ion Amd. No. Date of issue Comments 3521 August 1981 Indicated by a sideline in the marginBSS157:1976 BSI 01-2000 i Contents Page 1 Inspection and testing procedure 1 2 Manufacture 1 3 Chemical composition 1 4 Surface dressing 1 5 Condition 1 6 Heat treatment 1 7 Mechanical properties 2 8 Grain size
6、 2ii blankBSS157:1976 BSI 01-2000 1 NOTEThe specified chemical composition, heat treatment andtensile properties comply with AECMA Recommendation FE-PL71 (for material heat treated to a tensile strength of1180 1380 MPa). 1 Inspection and testing procedure 1.1 General. This British Standard shall be
7、used in conjunction with the relevant sections of the latest issue of BSS100 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 Chemic
8、al composition The steel shall contain: 4 Surface 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 treatm
9、ent shall consist of heating uniformly at a 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 and930 C. b) Hardeni
10、ng. Heat at a temperature of825 10 C, followed by cooling in oil. c) Tempering. Heat at a temperature of190 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 treatmen
11、t is used for parts, it may be necessary to agree alternative mechanical properties. Bars for machining delivered inother than the finally heat treated condition sections 1 and 2 Forging stock and billets andbars for subsequent working sections 1 and 5 Forgings sections 1 and 6 Parts finally heat tr
12、eated aftermachining sections 1 and 7 Element % min. max. Carbon 0.12 0.17 Silicon 0.15 0.40 Manganese 0.30 0.60 Phosphorus 0.025 Sulphur 0.020 Chromium 0.8 1.1 Molybdenum 0.20 0.30 Nickel 3.0 3.5 Designation Form Condition of supply S157B Black bars formachining Softened S157D Bright bars formachin
13、ing Softened and subsequently cold drawn, cold rolled, machined or ground S157A Forging stock and billets and bars for subsequent working Softened S157C Forgings SoftenedBSS157:1976 2 BSI 01-2000 7 Mechanical properties 7.1 Tensile test at room temperature and impact test. The mechanical properties
14、obtained from test pieces, machined from test samples reduced, where applicable, to 20mm diameter or square before heat treatment, shall be as follows: 7.2 Hardness test. The hardness of material heat treated in accordance with 6.1 shall be not greater than 241HB. 8 Grain size The grain size shall b
15、e 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 strength Elongation Izod impact min. min. max. min. min. MPa (= N/mm 2 ) MPa (= N/mm 2 ) MPa (= N/mm 2 ) % ftlbf 930
16、 1180 1380 8 25 NOTEInformation on SI units is given in BS 3763 “The International Systems of units (SI)” and BS 350 “Conversion factors and tables”.blankBSS157: 1976 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparin
17、g BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions BritishStandards are updated by amendment or revision. Users of BritishStandards should make sure that they possess the latest amendments or editions. It
18、is the constant aim of BSI to improve the quality of our products and services. We would be grateful if anyone finding an inaccuracy or ambiguity while using this BritishStandard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front
19、 cover. Tel:02089969000. Fax:02089967400. BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards. Buying standards Orders for all BSI, international and foreign standards publications should be addressed to
20、Customer Services. Tel:02089969001. Fax:02089967001. In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that have been published as BritishStandards, unless otherwise requested. Information on standards BSI provides a wide range of informati
21、on on national, European and international standards through its Library and its Technical Help to Exporters Service. Various BSI electronic information services are also available which give details on all its products and services. Contact the Information Centre. Tel:02089967111. Fax:02089967048.
22、Subscribing members of BSI are kept up to date with standards developments and receive substantial discounts on the purchase price of standards. For details of these and other benefits contact Membership Administration. Tel:02089967002. Fax:02089967001. Copyright Copyright subsists in all BSI public
23、ations. BSI also holds the copyright, in the UK, of the publications of the international standardization bodies. Except as permitted under the Copyright, Designs and Patents Act 1988 no extract may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, ph
24、otocopying, recording or otherwise without prior written permission from BSI. This does not preclude the free use, in the course of implementing the standard, of necessary details such as symbols, and size, type or grade designations. If these details are to be used for any other purpose than implementation then the prior written permission of BSI must be obtained. If permission is granted, the terms may include royalty payments or a licensing agreement. Details and advice can be obtained from the Copyright Manager. Tel:02089967070.
