ISO/TS 7705:2017

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

General Information

• Status: Published
• Publication Date: 18-Jul-2017
• ICS: 77.080.20 - Steels
• Technical Committee: ISO/TC 17/SC 20 - General technical delivery conditions, sampling and mechanical testing methods
• Drafting Committee: ISO/TC 17/SC 20 - General technical delivery conditions, sampling and mechanical testing methods
• Current Stage: 9093 - International Standard confirmed
• Start Date: 16-Aug-2024
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO/TR 7705:1991 - Guidelines for specifying Charpy V-notch impact prescriptions in steel specifications
• Effective Date: 21-Dec-2013

Overview

ISO/TS 7705:2017 - "Guidelines for specifying Charpy V‑notch impact prescriptions in steel specifications" provides practical guidance for including Charpy V‑notch impact requirements in steel product standards and delivery documents. The Technical Specification explains the role of Charpy testing as a reproducible, low‑cost delivery control and classification tool for notch toughness, describes the information obtainable from impact testing (energy vs temperature curves), and gives recommendations on specifying tests, sample selection and interpretation.

Key topics

• Purpose and scope: guidance for specifying Charpy V‑notch test prescriptions in steel specifications.
• Notch toughness vs fracture toughness: distinguishes small‑scale notch tests (Charpy, drop‑weight) from fracture‑mechanics tests (e.g., CTOD - ISO 12135) and focuses on notch tests suitable for delivery control.
• Charpy test fundamentals: description of the absorbed‑energy versus temperature curve with upper shelf, transition range and lower shelf, and emphasis that energy results are reported in joules (J).
• Historical and practical reference values: commonly used reference levels (27 J for many unalloyed steels; higher levels such as 40 J for certain fine‑grain or quenched‑and‑tempered steels) are discussed.
• Factors affecting impact results: material thickness, stress state, temperature, steel type, loading rate, surface condition, residual stresses, yield strength, specimen orientation, notch sharpness, specimen position and striker type.
• Subsize test pieces: standard specimen is 10 mm × 10 mm; standardized subsize specimens include 10 mm × 7.5 mm, 10 mm × 5 mm and 10 mm × 2.5 mm. The document cautions that subsize specimens shift the transition to lower temperatures and reduce upper‑shelf energy; empirical corrections exist but there is no simple mathematical conversion.
• Specification practice: recommendations cover selection and preparation of samples, cutting and machining, number and location of test pieces, and interpretation of results.

Applications

ISO/TS 7705:2017 is intended for people who prepare or apply steel product specifications and quality control procedures:

• Standards writers and product committees specifying mechanical delivery conditions
• Steel producers and mill QA teams establishing acceptance criteria
• Welding engineers and structural designers using impact requirements for fabrication and service temperature considerations
• Inspection and testing laboratories implementing Charpy V‑notch testing for delivery control

Related standards

• ISO 12135 (CTOD fracture toughness testing) - referenced as a complementary fracture‑mechanics approach for design rather than routine delivery testing.

Keywords: Charpy V‑notch, impact test, impact energy, transition temperature, subsize test pieces, ISO/TS 7705:2017, steel specifications, notch toughness.

Standards Content (Sample)

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
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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
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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 p
...