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1、BRITISH STANDARD BS 970-2:1988 Incorporating Amendment Nos. 1 and 2 Specification for Wrought steels for mechanical and allied engineering purposes Part 2: Requirements for steels for the manufacture of hot formed springs UDC 669.14-131:669-122.4:669-15:669.018.27:001.2 BS 970-2:1988 This British St
2、andard, having been prepared under the direction of the Iron and Steel Standards Committee, was published under the authority of the Board of BSI and comes into effect on 31 October 1988 BSI 12-1998 First published July 1941 First revision October 1942 Second revision March 1947 Third revision Janua
3、ry 1955 Fourth revision, as Part 5, June 1972 Fifth revision, as Part 2, October 1988 The following BSI references relate to the work on this standard: Committee reference ISM/31 Draftfor comment 87/36929 DC ISBN 0 580 16869 7 Committees responsible for this British Standard The preparation of this
4、British Standard was entrusted by the Iron and Steel Standards Committee (ISM/-) to Technical Committee ISM/31, upon which the following bodies were represented: British Chain Manufacturers Association British Coal British Forging Industry Association British Industrial Fasteners Federation British
5、Rail British Steel Industry Cold Rolled Sections Association Department of Trade and Industry (National Physical Laboratory) Engineering Industries Association Federation of British Engineers Tool Manufacturers Institution of Production Engineers Lloyds Register of Shipping Ministry of Defence Natio
6、nal Association of Steel Stockholders Road Vehicle Spring Society Society of British Aerospace Companies Limited Society of Motor Manufacturers and Traders Limited Stainless Steel Fabricators Association of Great Britain The following bodies were also represented in the drafting of the standard, thr
7、ough sub-committees and panels: Spring Research and Manufacturers Association Amendments issued since publication Amd. No.Date of issueComments 6190August, 1989 6942February, 1992 Indicated by a sideline in the margin BS 970-2:1988 BSI 12-1998i Contents Page Committees responsibleInside front cover
8、Forewordii 1Scope1 2Definitions1 3General1 4Information to be supplied by the purchaser1 5Steelmaking processes and casting methods1 6Chemical composition1 7Freedom from defects4 8Surface condition4 9Condition of material on despatch4 10Physical properties4 11Selection and testing of specimens4 12Fo
9、rm of section6 13Marking7 Appendix A Options10 Appendix B Recommended maximum dimensions for flats and rounds10 Figure 1 Positions for decarburization measurements6 Figure 2 Edge profiles for flats7 Figure 3 Dimensions of rib and groove spring steel for plates 9.52 mm thick and over8 Table 1 Steels
10、to restricted chemical composition ranges. Chemical composition2 Table 2 Composition of steels to hardenability requirements. Chemical composition2 Table 3 Limits on residual elements3 Table 4 Permitted deviations from specified range on product analysis3 Table 5 Maximum acceptable depth for longitu
11、dinal defects on hot-rolled or drawn bar4 Table 6 Maximum levels of functional decarburization for hot-rolled or drawn flats5 Table 7 Steels to hardenability requirements5 Table 8 Average maximum inclusion levels5 Table 9 Normalizing and austenitizing temperatures for hardenability tests6 Table 10 T
12、olerances on width and thickness for flats8 Table 11 Tolerances on concavity, convexity and parallelism across the width for flats8 Table 12 Diameter and ovality tolerance for round bars9 Table 13 Recommended maximum dimensions for flats and rounds10 Publications referred toInside back cover BS 970-
13、2:1988 ii BSI 12-1998 Foreword This Part of BS 970 has been prepared under the direction of the Iron and Steel Standards Committee. It forms Part 2 of a restructured BS 970 and is a revision of BS 970-5:1972, incorporating the requirements of BS 24-3A:1959. Both these standards are withdrawn. The re
14、structured BS 970 consists of three Parts. Part 1 specifies general inspection and testing procedures and specific requirements for carbon, carbon manganese, alloy and stainless steels and was published in 1983. BS 970-4 was published in 1970 and specifies requirements for valve steels. New steels h
15、ave been introduced in this Part of BS 970 to reflect changes in spring manufacture, the need for fine-grained steels and, for certain applications, closely controlled hardenability. Requirements have also been introduced for average maximum levels of non-metallic inclusions for all types of bar and
16、 for depths of decarburization and surface defects on hot rolled or drawn bar. The dimensional and decarburization tolerances in this Part of BS 970 apply only to material supplied directly to the spring maker and not to intermediate products. The carbon steels for general applications have been rem
17、oved in this revision as they are already covered in Table 2 of BS 970-1:1983 (grades 080A67 and 060A78). A number of ordering options is listed in appendix A. These should be called up by the purchaser as required. Assessed capability. Users of this British Standard are advised to consider the desi
18、rability of assessment and registration of a suppliers quality systems against the appropriate Part of BS 5750 by a third party certification body. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct
19、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 to 10, an inside back cover and a back cover. This standard has been updated (see copyrigh
20、t date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. BS 970-2:1988 BSI 12-19981 1 Scope This Part of BS 970 specifies requirements for steelmaking, chemical composition, physical properties, dimensional tolerances and testing proc
21、edures for hot-rolled flats and rounds and drawn or turned (or peeled) or ground rounds for the production of hot formed and heat treated springs. The requirements apply to eleven grades of steel supplied to restricted chemical analysis ranges and twelve grades of steel supplied to hardenability lim
22、its. Special ordering options, to be called up, as required, by the purchaser, are included in appendix A. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Part of BS 970 the following definitions apply. 2.1 d
23、rawn bar bar of circular cross section obtained, usually after annealing and descaling by drawing of hot-rolled rod on a draw bench (cold deformation without removing material) followed by straightening and cutting. This operation gives the product special features with respect to shape, dimensional
24、 accuracy and surface finish but has only a small reducing effect on decarburization and defect depth 2.2 turned (or peeled) bar bar of circular cross section having the special features of drawn products, concerning shape, dimensional accuracy and bright surface finish produced by turning on a lath
25、e (or peeling), together with the additional benefit of metal removal on decarburization and defect depth 2.3 ground bar bar of circular cross section having the special features of drawn products, concerning shape, dimensional accuracy and bright surface finish, produced by grinding or grinding and
26、 polishing, together with the additional benefit of metal removal on decarburization and defect depth 3 General The steel products shall comply with the general requirements of this standard and with the specific requirements applicable to the grade concerned. Where any of the options given in appen
27、dix A are called up at the time of the enquiry and order, the steel products shall, in addition, comply with the requirements of any such options. 4 Information to be supplied by the purchaser 4.1 General The following information shall be supplied at the time of enquiry and order. a) Details of the
28、 form of section, size and quantity (see clause 12). b) The grade of steel (see Table 1, Table 2 and Table 7). 4.2 Options A number of ordering options are given in appendix A. If the purchaser does not specify any of these options at the time of enquiry and order, the manufacturer shall supply in a
29、ccordance with the basic specification. See option A.11. 5 Steelmaking processes and casting methods 5.1 Steelmaking Steelmaking shall be by any process except the air or mixed air and oxygen bottom blown basic converter process. 5.2 Casting methods The steel shall be cast into ingots or continuousl
30、y cast. See also option A.1. 6 Chemical composition 6.1 Composition ranges The chemical composition of the steel, based on cast analysis, shall comply with the requirements of the appropriate material specification in Table 1 or Table 2. See also option A.2. NOTE 1Table 2 gives the composition range
31、s for the steels in Table 7. NOTE 2The recommended maximum section thickness for each of the steel grades is given in appendix B. 6.2 Residual elements Elements not quoted in the relevant material specification shall not be added to the steel other than for the purpose of finishing the heat. Percent
32、ages of elements up to the limits given in Table 3 shall be considered as residual. BS 970-2:1988 2 BSI 12-1998 - - - BS 970-2:1988 BSI 12-19983 Table 3 Limits on residual elements6.3 Product analysis and permitted deviations Product analysis may differ from the cast analysis (see Table 1, Table 2 a
33、nd Table 3) due to heterogeneity arising during casting and solidification. Table 4 shows the deviations from the range specified for cast analysis permitted on product analysis. The deviation may occur either above or below the individual element ranges but shall not apply both above and below the
34、specified range for any one element in any one cast of steel. Test specimens for product analysis shall be taken in accordance with the appropriate method of BS 6200-3 or BS Handbook 19. See option A.4. Table 4 Permitted deviations from specified range on product analysis ElementLess than or equal t
35、o % m/m Nickel (Ni)0.40 Copper (Cu)0.35 Tin (Sn)0.035 NOTESee also option A.3. ElementRange in which maximum of specified element fallsDeviation from specified range %Over max.Under min. % CarbonOver 0.25 up to and including 0.500.020.02 CGreater than 0.500.030.03 SiliconUp to and including 0.450.03
36、0.03 SiGreater than 0.450.050.05 ManganeseOver 0.70 up to and including 1.00.040.04 MnOver 1.0 up to and including 2.00.050.05 PhosphorusUp to and including 0.0350.004 P SulphurUP to and including 0.0350.004 S ChromiumUp to and including 0.600.030.03 CrOver 0.60 up to and including 1.250.040.04 Moly
37、bdenumUp to and including 0.500.020.02 Mo NickelUp to and including 1.00.030.03 Ni VanadiumUp to and including 0.300.030.03 V BS 970-2:1988 4 BSI 12-1998 7 Freedom from defects The procedures for casting, working, reheating and cooling and the amount of working shall ensure that the product is free
38、from piping, central unsoundness and harmful segregation. 8 Surface condition 8.1 Surface defects Hot-rolled or drawn bar shall be free from transverse defects and from longitudinal defects deeper than those given in Table 5. Turned (or peeled) or ground bar shall not exhibit surface defects. Curren
39、tly established in-process methods for the inspection of hot-rolled bar may not detect all defects resulting in some bars in a consignment containing defects in excess of the maximum acceptable depth. Bars exhibiting such defects on later processing shall be deemed not to comply with this standard.
40、8.2 Surface texture of turned (or peeled) or ground bars When assessed in accordance with BS 1134-1, bars shall exhibit a maximum Ra of 3.2 m. See also option A.6. Table 5 Maximum acceptable depth for longitudinal defects on hot-rolled or drawn bar 8.3 Decarburization Complete decarburization shall
41、not be present. The maximum depth of functional decarburization on hot-rolled or drawn bars shall be as follows, when measured in accordance with BS 6617-1 or BS 6617-2. a) For flats, the requirements of Table 6 shall be met when measured in the areas defined in Figure 1. b) For rounds, the maximum
42、depth of decarburization shall be 1.5 % of the actual bar diameter for silico-manganese steels and 1.25 % of the actual bar diameter for alloy steels. Turned (or peeled) or ground bars shall not exhibit decarburization. 9 Condition of material on despatch Bar ends shall be free from splits. NOTEFor
43、the avoidance of shearing and machining problems, a maximum hardness of 321 Brinell Hardness Number (BHN) is recommended. Subcritical annealing may be required to ensure freedom from shearing and machining problems and may also be necessary in the case of rod material requiring decoiling and cutting
44、 for the production of rounds in straight lengths. When subcritical annealing is employed, the maximum recommended hardness is 277 BHN. See also option A.5. 10 Physical properties 10.1 Hardenability Steels to hardenability requirements shall comply with the hardness values at the positions specified
45、 in Table 7. See also option A.7. 10.2 Grain size Steels in both Table 1 and Table 7 shall exhibit a grain size of 5 to 8 (see BS 4490). See also option A.8. NOTEThis applies to the grain size assessment on a laboratory test (see 11.3) and to the developed grain size in the heat-treated spring. For
46、the latter, the austenitizing temperature used for the dual hot-forming/hardening operation should not exceed 1 000C. 10.3 Inclusion content Steels shall comply with the requirements in Table 8 for the level of freedom from non-metallic inclusions. See also options A.9 and A.10. 11 Selection and tes
47、ting of specimens 11.1 General Where options A.7, A.8 or A.9 are invoked, testing shall be carried out in accordance with the relevant subclause. 11.2 Hardenability One test sample selected to represent each cast shall be reduced by forging or rolling to a size not greater than 38 mm in diameter, wh
48、ich shall represent the full cross section of the material. This test sample shall also be of sufficient size to ensure the removal of decarburization in machining to the standard test specimen of 25 mm diameter. Normalizing and austenitizing temperatures for the hardenability test shall be as given
49、 in Table 9. Tests shall be carried out in accordance with method 1 of BS 4437. Thickness/diameterMaximum acceptable depth mm Up to and including 250.25 mm Over 25 up to and including 501 % of thickness Over 50 up to and including 63.5 0.50 mm Over 63.5 up to and including 80 0.60 mm BS 970-2:1988 BSI 12-19985 Table 6 Maximum levels of functional decarburization for hot-rolled or drawn flats Tab