ISO/FDIS 643
(Main)Steels — Micrographic determination of the apparent grain size
Steels — Micrographic determination of the apparent grain size
Aciers — Détermination micrographique de la grosseur de grain apparente
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FINAL DRAFT
International
Standard
ISO/TC 17/SC 7
Steels — Micrographic
Secretariat: AFNOR
determination of the apparent grain
Voting begins on:
size
2024-06-06
Aciers — Détermination micrographique de la grosseur de grain
Voting terminates on:
apparente
2024-08-01
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
ISO/CEN PARALLEL PROCESSING LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 17/SC 7
Steels — Micrographic determination
Secretariat: AFNOR
of the apparent grain size
Voting begins on:
Aciers — Détermination micrographique de la grosseur de grain
apparente
Voting terminates on:
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2024
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
ISO/CEN PARALLEL PROCESSING
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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 Reference number
ii
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
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 of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical ISO/TC 17, Steel, Subcommittee SC 7, Methods of testing (other than
mechanical tests and chemical analysis), in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 459, ECISS, European Committee for Iron and Steel Standardization, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This fifth edition cancels and replaces the fourth edition (ISO 643:2019), which has been technically revised.
The main changes are as follows:
— the test temperature of McQuaid-Ehn method has been modified for case hardening steels to 950 °C (see A.4);
— subclause 7.2 has been modified with reference to new Annex B and amended Table 2;
— Annex B from the third edition (ISO 643:2012) has been reinstated, now with new ISO grain size charts
instead of ASTM charts;
— parts of the old Annex B (evaluation method) have been revised and moved to the main body of the
standard (subclause 7.3) and the remainder of the annex has been renumbered as Annex C;
— new Annexes D and E have been added.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
FINAL DRAFT International Standard ISO/FDIS 643:2024(en)
Steels — Micrographic determination of the apparent grain size
WARNING — This document calls for the use of substances and/or procedures that may be injurious
to health if adequate safety measures are not taken. This document does not address any health
hazards, safety or environmental matters associated with its use. It is the responsibility of the user
of this document to establish appropriate health, safety and environmentally acceptable practices.
1 Scope
This document specifies micrographic methods 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, the
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
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 Grains
3.1.1
grain
closed polygonal shape with more or less curved sides, which can be revealed on a flat section through the
sample, polished and prepared for micrographic examination
[1]
Note 1 to entry: In ISO 4885 grain is defined as “space lattice formed by atoms with regular interstices".
Note 2 to entry: If any other constituent (e.g. pearlite) of similar dimensions to
...
ISO/FDIS 643:2024(en)
ISO/TC 17/SC 7
Secretariat: AFNOR
Date: 2024-0405-22
Steels — Micrographic determination of the apparent grain size
Aciers — Détermination micrographique de la grosseur de grain apparente
FDIS stage
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
EmailE-mail: copyright@iso.org
Website: www.iso.orgwww.iso.org
Published in Switzerland
ii © ISO 2024 – All rights reserved
Contents
Foreword . 5
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 . 6
6.1 Test location . 6
6.2 Revealing ferritic grain boundaries . 6
6.3 Revealing austenitic and prior-austenitic grain boundaries . 6
6.3.1 General . 6
7 Characterization of grain size . 7
7.1 General . 7
7.1.1 Characterization methods . 7
7.1.2 Formulae . 7
7.1.3 Accuracy of the methods . 7
7.2 Comparison method . 8
7.3 Planimetric method . 10
7.4 Intercept method . 17
7.4.1 General . 17
7.4.2 Linear intercept method . 19
7.4.3 Circular intercept method . 20
7.4.4 Assessment of results . 20
7.5 Other methods . 21
8 Test report . 23
Annex A (informative) Methods for revealing austenitic or prior-austenitic grain
boundaries in steels . 25
Annex B (normative) Determination of grain size with standard comparison charts . 30
Annex C (informative) Evaluation method . 53
Annex D (informative) Calculation of grain size and confidence interval . 56
Annex E (informative) Grains of different size indices . 59
Bibliography . 70
Foreword . 4
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
7 Characterization of grain size . 6
7.1 General . 6
7.2 Comparison method . 6
7.3 Planimetric method . 9
7.4 Intercept method.14
7.5 Other methods .17
8 Test report .18
Annex A (informative) Methods for revealing austenitic or prior-austenitic grain
boundaries in steels .19
Annex B (normative) Determination of grain size with standard comparison charts .24
Annex C (informative) Evaluation method.36
Annex D (informative) Calculation of grain size and confidence interval .38
Annex E (informative) Grains of different size indices .41
Bibliography .48
iv © ISO 2024 – All rights reserved
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.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 of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the World
Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical ISO/TC 17, Steel, Subcommittee SC 7, Methods of testing (other
than mechanical tests and chemical analysis), in collaboration with the European Committee for
Standardization (CEN) Technical Committee CEN/TC 459, ECISS -, European Committee for Iron and Steel
Standardization, in accordance with the Agreement on technical cooperation between ISO and CEN
(Vienna Agreement).
This fifth edition cancels and replaces the fourth edition (ISO 643:2019), which has been technically
revised.
The main changes are as follows:
— — the test temperature of McQuaid-Ehn method has been modified for case hardening steels to
950 °C (see A.4);A.4);
— — subclause 7.2subclause 7.2 has been modified with reference to new Annex BAnnex B and
amended Table 2;Table 2;
— — Annex BAnnex B from the third edition (ISO 643:2012) has been reinstated, now with new ISO
grain size charts instead of ASTM charts;
— — parts of the old Annex B (evaluation method) have been revised and moved to the main body of
the standard (subclause 7.3)(subclause 7.3) and the remainder of the annex has been renumbered as
Annex C;Annex C;
— — New Annexes D and Enew Annexes D and E have been added.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
vi © ISO 2024 – All rights reserved
www.iso.org/members.html.
vii
FINAL DRAFT INTERNATIONAL STANDARD
Steels — Micrographic determination of the apparent grain size
WARNING — This document calls for the use of substances and/or procedures that may be injurious
to health if adequate safety measures are not taken. This document does not address any health
hazards, safety or environmental matters associated with its use. It is the responsibility of the user of
this document to establish appropriate health, safety and environmentally acceptable practices.
1 Scope
This document specifies micrographic methods 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, the
meta
...
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