SIST EN ISO 643:2024

SLOVENSKI STANDARD
01-november-2024
Nadomešča:
SIST EN ISO 643:2020
Jekla - Mikrografsko določevanje navidezne velikosti kristalnih zrn (ISO 643:2024)
Steels - Micrographic determination of the apparent grain size (ISO 643:2024)
Stahl - Mikrophotographische Bestimmung der erkennbaren Korngröße (ISO 643:2024)
Aciers - Détermination micrographique de la grosseur de grain apparente (ISO
643:2024)
Ta slovenski standard je istoveten z: EN ISO 643:2024
ICS:
77.040.99 Druge metode za Other methods of testing of
preskušanje kovin metals
77.080.20 Jekla Steels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 643
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2024
EUROPÄISCHE NORM
ICS 77.040.99 Supersedes EN ISO 643:2020
English Version
Steels - Micrographic determination of the apparent grain
size (ISO 643:2024)
Aciers - Détermination micrographique de la grosseur Stahl - Mikrophotographische Bestimmung der
de grain apparente (ISO 643:2024) erkennbaren Korngröße (ISO 643:2024)
This European Standard was approved by CEN on 2 September 2024.

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 references
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 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 643:2024 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 643:2024) has been prepared by Technical Committee ISO/TC 17 "Steel" in
collaboration with Technical Committee CEN/TC 459/SC 1 “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 publication of an
identical text or by endorsement, at the latest by March 2025, and conflicting national standards shall
be withdrawn at the latest by March 2025.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 643:2020.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 643:2024 has been approved by CEN as EN ISO 643:2024 without any modification.

International
Standard
ISO 643
Fifth edition
Steels — Micrographic determination
2024-08
of the apparent grain size
Aciers — Détermination micrographique de la grosseur de grain
apparente
Reference number
ISO 643:2024(en) © ISO 2024
ISO 643:2024(en)
© ISO 2024
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 643:2024(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Grains .1
3.2 General .2
4 Symbols . 2
5 Principle . 3
6 Selection and preparation of the specimen. 5
6.1 Test location .5
6.2 Revealing ferritic grain boundaries .5
6.3 Revealing austenitic and prior-austenitic grain boundaries .5
6.3.1 General .5
7 Characterization of grain size . 6
7.1 General .6
7.1.1 Characterization methods .6
7.1.2 Formulae .6
7.1.3 Accuracy of the methods .6
7.2 Comparison method .6
7.3 Planimetric method .9
7.4 Intercept method . 13
7.4.1 General . 13
7.4.2 Linear intercept method .14
7.4.3 Circular intercept method . 15
7.4.4 Assessment of results . 15
7.5 Other methods .16
8 Test report . 17
Annex A (informative) Methods for revealing austenitic or prior-austenitic grain boundaries in
steels .18
Annex B (normative) Determination of grain size with standard comparison charts .23
Annex C (informative) Evaluation method .35
Annex D (informative) Calculation of grain size and confidence interval .37
Annex E (informative) Grains of different size indices .40
Bibliography .46

iii
ISO 643:2024(en)
Foreword
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 committees. 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 International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning
...