1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN ISO 643:2012Steels Micrographic determination of the apparent grain sizeBS EN ISO 643:2012 BRITISH STANDARDNational forewordThis British Standard is the UK implementation o
2、f EN ISO 643:2012. It supersedes BS EN ISO 643:2003 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee ISE/101/7, Methods of physical and metallographic testing.A list of organizations represented on this committee can be obtained on request to its secret
3、ary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2013. Published by BSI Standards Limited 2013ISBN 978 0 580 78671 6 ICS 77.040.99 Compliance with a British Standard canno
4、t confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 January 2013.Amendments issued since publicationDate T e x t a f f e c t e dEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 643 December 2012
5、 ICS 77.040.99 Supersedes EN ISO 643:2003English Version Steels - Micrographic determination of the apparent grain size (ISO 643:2012) Aciers - Dtermination micrographique de la grosseur de grain apparente (ISO 643:2012) Stahl - Mikrophotographische Bestimmung der scheinbaren Korngre (ISO 643:2012)
6、This European Standard was approved by CEN on 10 December 2012. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical re
7、ferences concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a
8、CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedo
9、nia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROP
10、ISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2012 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 643:2012: EBS EN ISO 643:2012EN ISO 643:2012 (E) 3 Foreword This document (EN ISO 643:2012) has
11、 been prepared by Technical Committee ISO/TC 17 “Steel“ incollaboration with Technical Committee ECISS/TC 101 “Test methods for steel (other than chemical analysis)”the secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publicati
12、on of an identicaltext or by endorsement, at the latest by June 2013, and conflicting national standards shall be withdrawn atthe latest by June 2013. Attention is drawn to the possibility that some of the elements of this document may be the subject of patentrights. CEN and/or CENELEC shall not be
13、held responsible for identifying any or all such patent rights. This document supersedes EN ISO 643:2003. According to the CEN/CENELEC Internal Regulations, the national standards organisations of the followingcountries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croat
14、ia, Cyprus, CzechRepublic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the U
15、nited Kingdom. Endorsement notice The text of ISO 643:2012 has been approved by CEN as a EN ISO 643:2012 without any modification. BS EN ISO 643:2012ISO 643:2012(E) ISO 2012 All rights reserved iiiContents Page Foreword iv 1 Scope1 2 Normative references1 3 Terms and definitions .1 4 Symbols and abb
16、reviated terms 2 5 Principle2 6 Selection and preparation of the specimen4 6.1 Test location 4 6.2 Revealing ferritic grain boundaries .5 6.3 Revealing austenitic and prior-austenitic grain boundaries.5 7 Characterization of grain size 9 7.1 Characterization by an index .9 7.2 Characterization by th
17、e intercept method 11 8 Test report14 Annex A (informative) Summary of methods for revealing ferritic, austenitic or prior-austenitic grain boundaries in steels15 Annex B (normative) Determination of grain size Standard charts taken from ASTM E11216 Annex C (normative) Evaluation method .31 BS EN IS
18、O 643:2012ISO 643:2012(E) iv ISO 2012 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committee
19、s. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the Inter
20、national Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International St
21、andards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the sub
22、ject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 643 was prepared by Technical Committee ISO/TC 17, Steel, Subcommittee SC 7, Methods of testing (other than mechanical tests and chemical analysis). This third edition cancels and replaces the
23、 second edition (ISO 643:2003), of which it constitutes a minor revision. A note was added after the first paragraph of 7.1.2. BS EN ISO 643:2012INTERNATIONAL STANDARD ISO 643:2012(E) ISO 2012 All rights reserved 1Steels Micrographic determination of the apparent grain size 1 Scope This Internationa
24、l Standard specifies a micrographic method of determining apparent ferritic or austenitic grain size in steels. It describes the methods of revealing grain boundaries and of estimating the mean grain size of specimens with unimodal size distribution. Although grains are three-dimensional in shape, t
25、he metallographic sectioning plane can cut through a grain at any point from a grain corner, to the maximum diameter of the grain, thus producing a range of apparent grain sizes on the two-dimensional plane, even in a sample with a perfectly consistent grain size. 2 Normative references The followin
26、g referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 3785, Steel Designation of test piece axes ISO 14250, Ste
27、el Metallographic characterization of duplex grain size and distributions ASTM E112, Standard Test Methods for Determining Average Grain Size 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 grain closed polygonal shape with more or less curve
28、d sides, which can be revealed on a flat cross-section through the sample, polished and prepared for micrographic examination A distinction is made between: 3.1.1 austenitic grain crystal with a face-centered cubic crystal structure which may, or may not, contain annealing twins 3.1.2 ferritic grain
29、 crystal with a body-centered cubic crystal structure which never contains annealing twins1)1) Ferritic grain size is generally estimated for non-alloy steels with a carbon content of 0,25 % or less. If pearlite islands of identical dimensions to those of the ferrite grains are present, the islands
30、are then counted as ferrite grains. BS EN ISO 643:2012ISO 643:2012(E) 2 ISO 2012 All rights reserved3.2 index positive, zero or possibly negative number G which is derived from the mean number m of grains counted in an area of 1 mm2of the section of the specimen NOTE By definition, G = 1 where m = 1
31、6; the other indices are obtained by the formula 82Gm = 3.3 intercept N number of grains intercepted by a test line, either straight or curved See Figure 1. NOTE Straight test lines will normally end within a grain. These end segments are counted as 1/2 an interception. N is the average of a number
32、of counts of the number of grains intercepted by the test line applied randomly at various locations. N is divided by the true line length, T,L usually measured in millimetres, in order to obtain the number of grains intercepted per unit length, .LN 3.4 intersection P number of intersection points b
33、etween grain boundaries and a test line, either straight or curved See Figure 1. NOTE P is the average of a number of counts of the number of grain boundaries intersected by the test line applied randomly at various locations. P is divided by the true line length, T,L usually measured in millimetres
34、, in order to obtain the number of grain boundary intersections per unit length, .LP 4 Symbols and abbreviated terms The symbols used are given in Table 1. 5 Principle The grain size is revealed by micrographic examination of a polished section of the specimen prepared by an appropriate method for t
35、he type of steel and for the information sought. NOTE If the order or the International Standard defining the product does not stipulate the method of revealing the grain, the choice of this method is left to the manufacturer. This average size is characterized either a) by an index obtained usually
36、 by comparison with standard charts for the measurement of grain size; or by counting to determine the average number of grains per unit area; b) or by the mean value of the intercepted segment. BS EN ISO 643:2012ISO 643:2012(E) ISO 2012 All rights reserved 3Interception, N, counts for a straight li
37、ne on a single-phase grain structure where the arrows point to 6 intercepts and two line segments ending within grain (2 1/2 = 1 N) and N = 7 Intersection, P, counts for a straight test line placed over a single-phase grain structure where the arrows point to 7 intersection points and P =7 Figure 1
38、Examples of intersection, P, and interception, N BS EN ISO 643:2012ISO 643:2012(E) 4 ISO 2012 All rights reservedTable 1 Symbols Symbols Definition Value a Mean area of grain in square millimetres 1am= AFApparent area of the test figure in square millimetres d Mean grain diameter in millimetres 1dm=
39、 D Diameter of the circle on the ground glass screen of the microscope or on a photomicrograph enclosing the image of the reference surface of the test piece 79,8 mm (area = 5 000 mm2) g Linear magnification (to be noted as a reference) of the microscopic image In principle 100 G Equivalent index of
40、 grain size K Conversion factor from linear magnification g to linear magnification 100 100gK = l Mean lineal intercept length, generally expressed in millimetres 1/ 1/ LLlN P= LTTrue length of the test line divided by the magnification, in millimetres m Number of grains per square millimetre of tes
41、t piece surface in the area examined m = 2 n100(magnification 100) m = 2 K2ng(magnification g) M Number of the closest standard chart picture where g is not 100. ngTotal equivalent number of grains examined on the image of diameter D (with a magnification g) n1Number of grains completely inside the
42、circle of diameter D n2Number of grains intersected by the circle of diameter D n100Total equivalent number of grains examined on the image of diameter D (with magnification 100) 2100 12nnn=+ N Mean number of grains intercepted per unit length L LN Mean number of grains intercepted per unit length o
43、f the line T/LNNL= NxNumber of intercepts per millimetre in the longitudinal direction a NyNumber of intercepts per millimetre in the transverse direction a NzNumber of intercepts per millimetre in the perpendicular direction a P Mean number of counts of the number of grain boundaries intersected by
44、 the test line applied randomly at various locations LP Mean number of grain boundary intersections per unit length of test line T/LP PL= aThe method for designating the direction conforms to ISO 3785. 6 Selection and preparation of the specimen 6.1 Test location If the order, or the International S
45、tandard defining the product, does not specify the number of specimens and the point at which they are to be taken from the product, these are left to the manufacturer, although it has BS EN ISO 643:2012ISO 643:2012(E) ISO 2012 All rights reserved 5been shown that precision of grain size determinati
46、on increases the higher the number of specimens assessed. Therefore, it is recommended that two or more sections be assessed. Care shall be taken to ensure that the specimens are representative of the bulk of the product (i.e., avoid heavily deformed material such as that found at the extreme end of
47、 certain products or where shearing has been used to remove the specimen etc.). The specimens shall be polished in accordance with the usual methods. Unless otherwise stated by the product standard or by agreement with the customer, the polished face of the specimen shall be longitudinal, i.e., para
48、llel to the principal axis of deformation in wrought products. Measurements of the grain size on a transverse plane will be biased if the grain shape is not equiaxial. 6.2 Revealing ferritic grain boundaries The ferritic grains shall be revealed by etching with nital (ethanolic 2 % to 3 % nitric aci
49、d solution), or with an appropriate reagent. 6.3 Revealing austenitic and prior-austenitic grain boundaries 6.3.1 General In the case of steels having a single-phase or two-phase austenitic structure (delta ferrite grains in an austenitic matrix) at ambient temperature, the grain shall be revealed by an etching solution. For single phase austenitic stainless steels, the most commonly used chemical etchants are glyceregia, Kallings reagent (No. 2) and Marbles reagent. The best electrolytic etch for
