1、BRITISH STANDARD AEROSPACE SERIES CONFIRMED JUNE 1999 BS S 156:1976 Incorporating Amendment No. 1 Specification for 4% nickel-chromium- molybdenum case-hardening steel (vacuum arc remelted) billets, bars, forgings and parts (13201520 MPa) UDC 629.7:669.15242628-194-4:669.14.018.298.2 BSS 156:1976 Th
2、is British Standard, having been prepared under the directionof the Aerospace Industry Standards Committee,was published underthe authorityofthe Executive Boardon 30 June1976 BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference ACE/15 Draft for comment 75
3、/72482 DC ISBN 0 580 09104 7 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 p
4、ages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 and 2 and abackcover. 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 si
5、nce publication Amd. No. Date of issue Comments 3522 August 1981 Indicated by a sideline in the marginBSS 156:1976 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
6、ii blankBSS 156:1976 BSI 01-2000 1 1 Inspection and testing procedure 1.1 General. This British Standard shall be used in conjunction with the relevant sections of the latest issue of BS S 100 as follows: 1.2 Sulphur printing or deep etching tests. Onesample shall be taken from each end of each ingo
7、t for sulphur printing or deep etching tests. 1.3 Ultrasonic examination. Billets and bars and, where practicable, forgings shall be subjected to ultrasonic examination. 2 Manufacture The material shall be manufactured by consumable electrode vacuum arc remelting. 3 Chemical composition The steel sh
8、all 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 Normalizing treatment. The normalizing treatment shall consist of he
9、ating uniformly at a temperature between910 C and 930 C, followed by cooling in air. Bars for machining delivered inother than the finally heat treated condition sections 1 and 2 Forging stock and billets and bars for subsequent working sections 1 and 5 Forgings sections 1 and 6 Parts finally heat t
10、reated aftermachining sections 1 and 7 Element % min. max. Carbon 0.14 0.18 Silicon 0.10 0.35 Manganese 0.25 0.55 Phosphorus 0.015 Sulphur 0.012 Chromium 1.0 1.4 Molybdenum 0.20 0.30 Nickel 3.8 4.3 Designation Form Condition of supply S156B Black bars formachining Normalized and softened S156D Brigh
11、t bars for machining Normalized and softened and subsequently cold drawn, cold rolled, machined or ground S156A Forging stock and billets and barsfor subsequent working Softened S156C Forgings Normalized and softenedBSS 156:1976 2 BSI 01-2000 6.2 Softening treatment. The softening treatment shall co
12、nsist of heating uniformly at a temperature of not less than 630 C, followed by cooling in air. 6.3 Final heat treatment 6.3.1 Except as provided in 6.3.2, the final heat treatment shall consist of the following: a) Carburizing or blank carburizing. Heat uniformly at a temperature between 880 C and
13、930 C. b) Hardening. Heat at a temperature of 825 10 C, followed by cooling in oil. NOTEA sub-zero treatment at 60 C to 80 C is recommended before tempering. c) Tempering. Heat at a temperature of 190 5 C, followed by cooling in air. 6.3.2 Alternatively to 6.3.1, the final heat treatment of parts sh
14、all be agreed between the manufacturer and the purchaser. NOTEIf an alternative heat treatment is used for parts, it may be necessary to agree alternative mechanical properties. 7 Mechanical properties 7.1 Tensile test at room temperature and impact test. The mechanical properties obtained from test
15、 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 accordance with 6.1 and 6.2, or 6.2, as appropriate shall be not greater than 277 HB. 0.2% proof stress T
16、ensile strength Elongation Reduction of area Izod impact min. min. max. min. min. min. MPa (= N/mm 2 ) MPa (= N/mm 2 ) MPa (= N/mm 2 ) % % ft lbf 1 030 1 320 1 520 11 40 30 NOTEInformation on SI units is given in BS 3763 “TheInternational System of units (SI)” and BS 350 “Conversion factors andtable
17、s”.blankBS S 156:1976 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions
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