ISO/TS 7705:2017
(Main)Guidelines for specifying Charpy V-notch impact prescriptions in steel specifications
Guidelines for specifying Charpy V-notch impact prescriptions in steel specifications
ISO/TS 7705:2017 gives guidelines for specifying Charpy V-notch impact prescriptions in steel specifications.
Lignes directrices pour la spécification des prescriptions d'énergie de rupture sur éprouvette Charpy à entaille en V dans les normes d'acier
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TECHNICAL ISO/TS
SPECIFICATION 7705
First edition
2017-07
Guidelines for specifying Charpy
V-notch impact prescriptions in steel
specifications
Lignes directrices pour la spécification des prescriptions d’énergie de
rupture sur éprouvette Charpy à entaille en V dans les normes d’acier
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General features of Charpy V-notch impact test . 1
4.1 Toughness testing methods in design codes and in steel specifications . 1
4.2 Historical background to the Charpy V-notch impact test . 1
4.3 The Charpy V-notch impact test in relation to other tests . 2
4.4 Factors influencing impact properties . 2
4.5 The Charpy V-notch impact test as a powerful tool for delivery control in
steel specifications . 3
5 Information to be gained from the impact test . 3
6 Subsize test pieces . 6
7 Recommendations for specifying impact strength requirements in steel specifications .7
7.1 Selection and preparation of samples and test pieces . 7
7.1.1 Selection and preparation of samples . 7
7.1.2 Cutting and machining . 7
7.2 Number of test pieces to be taken per sample and specific requirements . 7
7.3 Location of test pieces . 7
7.4 Interpretation of test results . 8
Bibliography . 9
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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 17, Steel, Subcommittee SC 20, General
technical delivery conditions, sampling and mechanical testing methods.
This first edition of ISO/TS 7705 cancels and replaces ISO/TR 7705:1991, which has been technically
revised.
iv © ISO 2017 – All rights reserved
TECHNICAL SPECIFICATION ISO/TS 7705:2017(E)
Guidelines for specifying Charpy V-notch impact
prescriptions in steel specifications
1 Scope
This document gives guidelines for specifying Charpy V-notch impact prescriptions in steel
specifications.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 General features of Charpy V-notch impact test
4.1 Toughness testing methods in design codes and in steel specifications
Tests for evaluating the toughness of steel can be divided into two categories: notch toughness tests
and fracture toughness tests based on fracture mechanics.
Notch toughness tests are used to measure the ability of a material to absorb energy and deform
plastically in the presence of a mechanical notch. The Charpy V-notch impact test and the drop weight
test are typical examples of small scale tests which are used for evaluations of notch toughness. They
are often used to determine the ductile to brittle transition temperature of a material and to give a
qualitative estimate of the material’s toughness. Due to relatively good reproducibility and low cost
these methods are highly suitable for use as delivery tests for steel consignments.
Fracture toughness tests such as the crack-tip opening displacement (CTOD) test (see ISO 12135) are
fracture mechanics tests which are generally concerned with the determination of critical crack sizes
which can appear without causing fracture in a material loaded to a specific stress level. Fracture
mechanics tests are very complicated and expensive to carry out. They are primarily used to examine
the behaviour of pressurized or structural components with respect to safety rules, etc. Therefore,
fracture mechanics testing is primarily connected with design codes and not with steel specifications.
For these reasons, only notch toughness tests are dealt with in these guidelines for steel specifications.
4.2 Historical background to the Charpy V-notch impact test
When welded structures, especially heavy ones such as bridges and ships, were first developed on an
industrial scale, and especially when the fabrication methods called for joining heavy segments by
welding, problems with brittle fractures became more common. This was especially evident during the
Second World War when the USA began to produce welded ships of the Liberty and Victory type, where
a large number of failures occurred due to brittle fractures.
An empirical relationship based on many tests was found between the Charpy V-notch impact energy
and service fractures. The work initiated by the USA was continued by the International Institute of
Welding (IIW) who provide recommendations and a classification system for steels according to their
susceptibility to brittle fracture after welding.
Originally the USA required an impact energy value of 15 footpounds (ft lb) for a standard
10 mm x 10 mm V-notch impact test piece. This was later increased to 20 ft lb. The IIW converted these
figures into metric units and referred the impact energy value to the cross-section under the notch,
which gave a figure of 3,5 kg m/cm corresponding to 20 ft lb. Later the units were transformed into SI
units. This gave the value of 27 J (20 ft lb).
In 1953 Pellini compared the Charpy V-notch impact test with an explosion crack starter test intended
to simulate the service performance of higher quality steels. Pellini recommended impact energy of
20 ft lb (27 J) instead of the earlier used 15 ft lb.
Wells also simulated service conditions at the starting point of a brittle fracture crack by using a
wide plate test. The intention of this test, which could not be used as an acceptance test for a steel
consignment, was to include in a big plate specimen the stresses existing in a weld, the influence of
plate thickness, the type of defect, etc. The results of wide plate tests were also compared with Charpy
V-notch impact values.
Today 27 J is generally used for unalloyed steels. In some cases, for instance for fine grain steels or
quenched and tempered steel grades, this level can be 27 J or alternatively fixed to a higher level (40 J)
according to the requirements for specific steels and intended applications. Impact test requirements
are included in the product standard.
4.3 The Charpy V-notch impact test in relation to other tests
Originally the Charpy impact test was performed with a “keyhole” or U-notch test bar. Its purpose was
to check that the material was sound as to cleanliness, rolling and heat treatment. In the 1950s interest
was concentrated on the risk of brittle fracture in welded structures and the V-notch test bar was
introduced as the V-notch test indicates transition behaviour more clearly than the U-notch test.
In addition to the Charpy impact test other impact test methods (e.g. Mesnager, lzod, Schnadt) have also
been used.
The drop weight test is a material test which is intended to measure the highest temperature at which
steel exhibits brittle fracture. This test can be an alternative or can be required in addition to the
Charpy V-notch impact test.
4.4 Factors influencing impact properties
The behaviour of a steel structure subject to impact is not only dependent on the material. It is also
dependent on the following:
— material thickness;
— stress state;
— temperature;
— steel type;
— loading rate;
— surface conditions;
— residual stresses;
— yield strength.
2 © ISO 2017 – All rights reserved
In addition, the Charpy V-notch test result is influenced by the following:
— orientation of test piece;
— orientation of notch;
— sharpness of notch;
— specimen position in the product;
— steel type;
— type of impact machine striker.
For these and other reasons the impact energies or transition temperatures determined under the
well-defined conditions of an impact test cannot, without any further considerations, be regarded as
determinant with respect to temperature and/or thickness for the application of the material.
4.5 The Charpy V-notch impact test as a powerful tool for delivery control in steel
specifications
The Charpy V-notch impact test can be used as a means of expressing, in a specification, the susceptibility
of a steel to brittle fracture. It is an inexpensive and easily reproducible test method which is empirically
related to the susceptibility to brittle fracture and therefore to the weldability of a steel.
Impact test requirements are included in many ISO steel specifications.
For specimen and notch orientation consult the relevant product standard.
5 Information to be gained from the impact test
Independent of the size of the test piece, the thickness of the material and the type of notch, the
impact test carried out for a specified steel of given thickness at different temperatures gives a curve
of absorbed energy versus temperature (see Figure 1). This curve can be separated into three parts:
one part at higher temperatures and higher energies (upper shelf); one part at lower temperatures and
lower energies (lower shelf); and a transition range in between. The scatter of results on the upper and
lower shelves is relatively small but the scatter in the transition part of the curve is relatively large.
Because of this scatter, the requirement of testing three test pie
...
TECHNICAL ISO/TS
SPECIFICATION 7705
First edition
2017-07
Guidelines for specifying Charpy
V-notch impact prescriptions in steel
specifications
Lignes directrices pour la spécification des prescriptions d’énergie de
rupture sur éprouvette Charpy à entaille en V dans les normes d’acier
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General features of Charpy V-notch impact test . 1
4.1 Toughness testing methods in design codes and in steel specifications . 1
4.2 Historical background to the Charpy V-notch impact test . 1
4.3 The Charpy V-notch impact test in relation to other tests . 2
4.4 Factors influencing impact properties . 2
4.5 The Charpy V-notch impact test as a powerful tool for delivery control in
steel specifications . 3
5 Information to be gained from the impact test . 3
6 Subsize test pieces . 6
7 Recommendations for specifying impact strength requirements in steel specifications .7
7.1 Selection and preparation of samples and test pieces . 7
7.1.1 Selection and preparation of samples . 7
7.1.2 Cutting and machining . 7
7.2 Number of test pieces to be taken per sample and specific requirements . 7
7.3 Location of test pieces . 7
7.4 Interpretation of test results . 8
Bibliography . 9
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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 17, Steel, Subcommittee SC 20, General
technical delivery conditions, sampling and mechanical testing methods.
This first edition of ISO/TS 7705 cancels and replaces ISO/TR 7705:1991, which has been technically
revised.
iv © ISO 2017 – All rights reserved
TECHNICAL SPECIFICATION ISO/TS 7705:2017(E)
Guidelines for specifying Charpy V-notch impact
prescriptions in steel specifications
1 Scope
This document gives guidelines for specifying Charpy V-notch impact prescriptions in steel
specifications.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 General features of Charpy V-notch impact test
4.1 Toughness testing methods in design codes and in steel specifications
Tests for evaluating the toughness of steel can be divided into two categories: notch toughness tests
and fracture toughness tests based on fracture mechanics.
Notch toughness tests are used to measure the ability of a material to absorb energy and deform
plastically in the presence of a mechanical notch. The Charpy V-notch impact test and the drop weight
test are typical examples of small scale tests which are used for evaluations of notch toughness. They
are often used to determine the ductile to brittle transition temperature of a material and to give a
qualitative estimate of the material’s toughness. Due to relatively good reproducibility and low cost
these methods are highly suitable for use as delivery tests for steel consignments.
Fracture toughness tests such as the crack-tip opening displacement (CTOD) test (see ISO 12135) are
fracture mechanics tests which are generally concerned with the determination of critical crack sizes
which can appear without causing fracture in a material loaded to a specific stress level. Fracture
mechanics tests are very complicated and expensive to carry out. They are primarily used to examine
the behaviour of pressurized or structural components with respect to safety rules, etc. Therefore,
fracture mechanics testing is primarily connected with design codes and not with steel specifications.
For these reasons, only notch toughness tests are dealt with in these guidelines for steel specifications.
4.2 Historical background to the Charpy V-notch impact test
When welded structures, especially heavy ones such as bridges and ships, were first developed on an
industrial scale, and especially when the fabrication methods called for joining heavy segments by
welding, problems with brittle fractures became more common. This was especially evident during the
Second World War when the USA began to produce welded ships of the Liberty and Victory type, where
a large number of failures occurred due to brittle fractures.
An empirical relationship based on many tests was found between the Charpy V-notch impact energy
and service fractures. The work initiated by the USA was continued by the International Institute of
Welding (IIW) who provide recommendations and a classification system for steels according to their
susceptibility to brittle fracture after welding.
Originally the USA required an impact energy value of 15 footpounds (ft lb) for a standard
10 mm x 10 mm V-notch impact test piece. This was later increased to 20 ft lb. The IIW converted these
figures into metric units and referred the impact energy value to the cross-section under the notch,
which gave a figure of 3,5 kg m/cm corresponding to 20 ft lb. Later the units were transformed into SI
units. This gave the value of 27 J (20 ft lb).
In 1953 Pellini compared the Charpy V-notch impact test with an explosion crack starter test intended
to simulate the service performance of higher quality steels. Pellini recommended impact energy of
20 ft lb (27 J) instead of the earlier used 15 ft lb.
Wells also simulated service conditions at the starting point of a brittle fracture crack by using a
wide plate test. The intention of this test, which could not be used as an acceptance test for a steel
consignment, was to include in a big plate specimen the stresses existing in a weld, the influence of
plate thickness, the type of defect, etc. The results of wide plate tests were also compared with Charpy
V-notch impact values.
Today 27 J is generally used for unalloyed steels. In some cases, for instance for fine grain steels or
quenched and tempered steel grades, this level can be 27 J or alternatively fixed to a higher level (40 J)
according to the requirements for specific steels and intended applications. Impact test requirements
are included in the product standard.
4.3 The Charpy V-notch impact test in relation to other tests
Originally the Charpy impact test was performed with a “keyhole” or U-notch test bar. Its purpose was
to check that the material was sound as to cleanliness, rolling and heat treatment. In the 1950s interest
was concentrated on the risk of brittle fracture in welded structures and the V-notch test bar was
introduced as the V-notch test indicates transition behaviour more clearly than the U-notch test.
In addition to the Charpy impact test other impact test methods (e.g. Mesnager, lzod, Schnadt) have also
been used.
The drop weight test is a material test which is intended to measure the highest temperature at which
steel exhibits brittle fracture. This test can be an alternative or can be required in addition to the
Charpy V-notch impact test.
4.4 Factors influencing impact properties
The behaviour of a steel structure subject to impact is not only dependent on the material. It is also
dependent on the following:
— material thickness;
— stress state;
— temperature;
— steel type;
— loading rate;
— surface conditions;
— residual stresses;
— yield strength.
2 © ISO 2017 – All rights reserved
In addition, the Charpy V-notch test result is influenced by the following:
— orientation of test piece;
— orientation of notch;
— sharpness of notch;
— specimen position in the product;
— steel type;
— type of impact machine striker.
For these and other reasons the impact energies or transition temperatures determined under the
well-defined conditions of an impact test cannot, without any further considerations, be regarded as
determinant with respect to temperature and/or thickness for the application of the material.
4.5 The Charpy V-notch impact test as a powerful tool for delivery control in steel
specifications
The Charpy V-notch impact test can be used as a means of expressing, in a specification, the susceptibility
of a steel to brittle fracture. It is an inexpensive and easily reproducible test method which is empirically
related to the susceptibility to brittle fracture and therefore to the weldability of a steel.
Impact test requirements are included in many ISO steel specifications.
For specimen and notch orientation consult the relevant product standard.
5 Information to be gained from the impact test
Independent of the size of the test piece, the thickness of the material and the type of notch, the
impact test carried out for a specified steel of given thickness at different temperatures gives a curve
of absorbed energy versus temperature (see Figure 1). This curve can be separated into three parts:
one part at higher temperatures and higher energies (upper shelf); one part at lower temperatures and
lower energies (lower shelf); and a transition range in between. The scatter of results on the upper and
lower shelves is relatively small but the scatter in the transition part of the curve is relatively large.
Because of this scatter, the requirement of testing three test pie
...
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