1、BRITISH STANDARD BS6286:1982 ISO4970:1979 Methods of Measurement of total or effective thickness of thin surface-hardened layers in steel ISO title: Steel Determination of total or effective thickness of thin surface-hardened layers UDC669.14-155:620.186+620.178.152.341.2BS6286:1982 This British Sta
2、ndard, having been prepared under the directionof the Iron and SteelStandards Committee, waspublished under the authorityof the Board of BSIandcomes into effect on 30September1982 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference ISE/72 Draft for comme
3、nt 77/80023 DC ISBN 0 580 12885 7 Cooperating organizations The Iron and Steel Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following: British Constructional Steelwork Association British Internal Combustion Engine Manufacturers
4、Association British Ironfounders Association British Railways Board* British Steel Industry* British Steel Industry (Wire Section) Concrete Society Limited Council of Ironfoundry Associations Department of Industry (National Physical Laboratory) Electricity Supply Industry in England and Wales Engin
5、eering Equipment Users Association Federation of Civil Engineering Contractors Institute of Quality Assurance Institution of Production Engineers Institution of Structural Engineers International Tin Research Institute Lloyds Register of Shipping National Association of Drop Forgers and Stampers Oil
6、 Companies Materials Association Process Plant Association Royal Institute of British Architects Society of Motor Manufacturers and Traders Limited Steel Casting Research and Trade Association Water-tube Boilermakers Association The organizations marked with an asterisk in the above list, together w
7、ith the following, were directly represented on the Technical Committee entrusted with the preparation of this British Standard: British Industrial Fasteners Federation Ministry of Defence Stainless Steel Fabricators Association of Great Britain Amendments issued since publication Amd. No. Date of i
8、ssue CommentsBS6286:1982 BSI 07-1999 i Contents Page Cooperating organizations Inside front cover National foreword ii 1 Scope and field of application 1 2 Methods of measurement 1 3 Test report 2 Figure 1 Longitudinal section obtained by machining a flat 3 Figure 2 Simple oblique section 3 Figure 3
9、 Grooved oblique section 3 Figure 4 Stepped test piece 4 Figure 5 Siting of the microhardness impressions 4 Publications referred to Inside back coverBS6286:1982 ii BSI 07-1999 National foreword This British Standard has been prepared under the direction of the Iron and Steel Standards Committee and
10、 is identical with ISO4970:1979 “Steel Determination of total or effective thickness of thin surface-hardened layers” published by the International Organization for Standardization (ISO). Terminology and conventions. The text of the international standard has been approved as suitable for publicati
11、on as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is especially drawn to the following. The comma has been used throughout as a decimal marker. In British Standards it is current practice to use a fu
12、ll point on the baseline as the decimal marker. Where the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. Cross-references. The reference to ISO2639 and ISO3754, for which there are no corresponding British Standards, constitutes informat
13、ive matter only, and since no mandatory requirements are involved, the validity of this British Standard is not affected. 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 wi
14、th 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, pagesi andii, pages1 to4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendm
15、ents incorporated. This will be indicated in the amendment table on the inside front cover.BS6286:1982 BSI 07-1999 1 1 Scope and field of application This International Standard specifies a method of measuring the total or effective thickness of thin surface-hardened layers, with thicknesses of less
16、 than or equal to0,3mm, obtained, for example, by mechanical (shot blasting, shot peening, etc.), thermal (flame or induction hardening, etc.) or thermochemical (carbonitriding, carburizing and hardening, etc.) treatment. It is not applicable to thin surface layers which are not continuous with the
17、basis metal. NOTESurface-hardened layers with thicknesses of more than0,3mm are covered by ISO2639, Steel Determination and verification of the effective depth of carburized and hardened cases; and ISO3754, Steel Determination of effective depth of hardening after flame or induction hardening. 2 Met
18、hods of measurement The two methods usually selected are: the micrographic method; the microhardness measurement method. The choice of the method and its accuracy depend on the nature of the thin layer and on its presumed thickness. Since the method used also affects the result obtained, the choice
19、has to be made by prior agreement between the parties concerned. 2.1 Micrographic method This method consists in examining the structural variations, from the periphery inwards to the centre, brought about by the treatment. The total thickness of the thin surface layer is defined as the distance fro
20、m the surface examined to the limit beyond which no visible structural variation is detected, as compared with the structure of the unaffected metal. The effective thickness is defined as the distance from the surface examined to the limit of a reference structure. 1) 2.1.1 Selection and preparation
21、 of sample The sample may be one of the following types: a) a section perpendicular to the longitudinal axis of the product, or, if the product has no longitudinal axis, a section perpendicular to the surface at a location to be agreed between the parties concerned; b) a longitudinal section obtaine
22、d by machining a1mm deep flat (this method applies only to round bars seeFigure 1); other depths of flat may be specified; c) an oblique section; the thinner the layer, the more acute the angle ! between the plane of the section and the surface must be (seeFigure 2). As it is a difficult operation t
23、o determine the angle !, it is preferable, wherever possible, to use an oblique section with a groove having a depth close to the presumed thickness of the thin layer (seeFigure 3). It is then possible to calculate the thickness of the thin layer without having to measure the angle ! (see2.1.2). Sma
24、ll samples (with a section of less than4cm 2 ) shall be examined all round their perimeter. Where samples are large, several samples shall be selected to ensure that they are fully representative. Sections taken from the corners of polygonal products, being special points, shall not be included. The
25、 number and relative position of the various samplings shall be specified by agreement between the parties concerned. Using the customary methods, micrographic polishing shall be carried out so as to avoid rounding off the sharp edges of the section, thus varying the angle of the oblique section. To
26、 ensure that this does not occur, the sample shall be mounted or shall be held in a clamp. The surface of the product may, if necessary, be protected by depositing a metal coating on it electrolytically. Etching using2 to4% nital (i.e.a2 to4% solution of nitric acid in alcohol) or another appropriat
27、e reagent, will show up the structure of the steel. 2.1.2 Measurement The total or effective thickness of the thin layer shall be measured either using a micrometer eyepiece, or directly on the ground glass screen of a projection microscope. In most cases the recommended minimum magnification is200x
28、. By a preliminary examination at low magnification it will be possible to ensure that there is no significant variation in the thickness of the surface layer along the perimeter examined. Several measurements (at least five) shall be taken on the part where the surface layer shows a uniform thickne
29、ss, and these shall be taken at regularly spaced points. The thickness of the surface layer is taken as the average of these measurements. NOTE 1In the case of the machined flat (seeFigure 1), the thickness of the layer, e, is given by the formula where 1) When, for example, the reference structure
30、is martensitic, the effective thickness is termed martensitic. b is the distance measured on the flat; f is the depth of the flat; R is the radius of the sample. e R2 R f f 2 R 2b 22b + =BS6286:1982 2 BSI 07-1999 If the flat is1mm deep, formula is simplified as follows: NOTE 2In the case of a simple
31、 oblique section (seeFigure 2), the thickness of the layer, e, is given by the formula e = l sin ! NOTE 3In the case of a grooved oblique section (seeFigure 3), the thickness of the layer, e, is given by the formula 2.2 Microhardness measurement method This method consists in determining the changes
32、 in Vickers microhardness 2)under a2,94N(300gf) load, measured from the circumference inwards to the centre of the product. Where the thickness of the hardened surface layer is not compatible with the size of the impression, other loads may be used by prior agreement between the parties concerned. T
33、he total thickness of the thin surface layer is defined by the distance from the surface to the limit beyond which the hardness of the unaffected metal is reached. The effective thickness is defined by the distance from the surface to the limit beyond which the required hardness (reference hardness)
34、 is reached. 2.2.1 Selection and preparation of sample The sample may be one of the following types: a) a section perpendicular to the longitudinal axis of the product, or, if the product has no longitudinal axis, a section perpendicular to the surface at a location to be agreed between the parties
35、concerned (this section is identical to that used in the micrographic examination); b) a longitudinal section identical to that used in the micrographic examination; c) a test piece with steps: these steps are precision-ground from the surface of the product to the part where the structure is that o
36、f the basis metal, and are0,05 or0,10mm thick (seeFigure 4); the stepped test piece is to be used when a limiting value for the thickness of the surface layer is specified; d) a simple or grooved oblique section identical to that used in the micrographic examination. The sample is prepared in exactl
37、y the same way as for the micrographic method, although the sample does not undergo etching, in order to simplify the measurement of the size of the impression. During the machining of the steps, precautions shall be taken to avoid causing any structural changes as a result of grinding. 2.2.2 Measur
38、ement The hardness impressions shall be situated along one or several parallel lines normal to the surface and inside a1,5mm wide interval, W (seeFigure 5). The first impression shall be situated at a distance from the surface equal to approximately twice the length of its diagonal. The distance bet
39、ween two adjacent impressions, S, shall not be less than2,5 times the length of the diagonal. The difference between the distances from each impression to the surface (d 2 d 1for example) shall not exceed0,1mm, and the accumulated distance shall be measured to an accuracy of 254m. The diagonals of t
40、he impressions shall be measured to an accuracy of 0,754m. The impressions shall be made under a2,94N(300gf) load and measured with the aid of an optical device providing a magnification of about400x. These determinations shall be carried out on the surface in two specific areas to be agreed between
41、 the parties concerned. For each one of these areas, the results shall provide data for plotting a graph of variations in hardness against the distance to the surface. NOTEIn the case of the machined flat or the oblique section, the thickness of the layer is calculated using the formulae in2.1.2. 3
42、Test report The test report shall contain the following information: a) the grade and the treatment of the material; b) the number and locations of samples taken from the piece; c) the method of measuring adopted, and the procedure; d) the type of thickness measured (total or effective); e) the resu
43、lts of measurements enabling the thickness of the surface layer to be defined; f) any abnormalities observed during measurement; g) any incidents occurring during measurement. where l is the distance measured; ! is the angle of the oblique section. where l is the distance measured; l9 is the length
44、of the groove on the oblique section; e9 is the depth of the groove. 2) The Knoop microhardness method may be used. eR2 R 1 R 2b 2 2 b + = ee l l - =BS6286:1982 BSI 07-1999 3 Figure 1 Longitudinal section obtained by machining a flat Figure 2 Simple oblique section Figure 3 Grooved oblique sectionBS
45、6286:1982 4 BSI 07-1999 Figure 4 Stepped test piece Figure 5 Siting of the microhardness impressionsBS6286:1982 BSI 07-1999 Publications referred to See national foreword.BS6286:1982 ISO4970:1979 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national
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