ISO 24497-2:2020

INTERNATIONAL ISO
STANDARD 24497-2
Second edition
2020-03
Non-destructive testing — Metal
magnetic memory —
Part 2:
Inspection of welded joints
Essais non destructifs — Mémoire magnétique des métaux —
Partie 2: Examen des assemblages soudés
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Basic principles . 1
5 Requirements for the inspected object . 2
6 Testing equipment requirements . 2
7 Preparation for testing . 2
8 Test procedure . 2
8.1 General . 2
8.2 Manual inspection of welded joints . 2
8.3 Inspection of welded joints using a scanning system . 3
9 Processing of test results . 4
Annex A (informative) Test report . 6
Annex B (informative) Example of manual stray field measurements . 7
Annex C (informative) Example of stray field measurements using a scanning system .10
Bibliography .13
Foreword
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electrotechnical standardization.
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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
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iso/ foreword .html.
This document was prepared by IIW, International Institute for Welding, Commission V, NDT and Quality
Assurance of Welded Products.
This second edition cancels and replaces ISO 24497-3:2007, which has been technically revised.
The main changes are as follows:
— Clauses 2 and 3 have been updated;
— the scope has been modified, MMM is a technique of the MT method;
— Clause 4 has been modified;
— Clauses 5, 6 and 7 have been replaced by references to ISO 24497-1;
— figures and annexes have been modified for more exact descriptions.
A list of all parts in the ISO 24497 series can be found on the ISO website.
Any feedback, question or request for official interpretation related to any aspect of this document
should be directed to IIW via your national standards body. A complete listing of these bodies can be
found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 24497-2:2020(E)
Non-destructive testing — Metal magnetic memory —
Part 2:
Inspection of welded joints
1 Scope
This document specifies general requirements for the application of the non-destructive (NDT) metal
magnetic memory (MMM) testing technique of the magnetic testing method for quality assurance of
welded joints.
This document can be applied to welded joints in any type of ferromagnetic products: pipelines, vessels,
equipment, and metal constructions, as agreed with the purchaser.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 17635, Non-destructive testing of welds — General rules for metallic materials
ISO 24497-1:2020, Non-destructive testing — Metal magnetic memory — Part 1: Vocabulary and general
requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 24497-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Basic principles
4.1 ММM testing is based on measurement and analysis of the distribution of stray fields (SF) on the
material of welded joints reflecting their technological past. Residual magnetization, induced during the
welding process, for example, is the main driving force for the SF inspection.
4.2 ММM testing permits the detection of stray field indications (SFI) and gives recommendations for
additional non-destructive testing in critical zones of vessels, pipelines, equipment, and construction
welded joints.
4.3 ММM testing allows the inspection of welded joints of any size and configuration (butt, tee, fillet,
lap, edge, intermittent, etc.) on all types of ferromagnetic and metastable austenitic steels and alloys, as
well as on cast irons.
NOTE The evaluation of SFI of metastable austenitic steels is restricted to ferromagnetic phases.
4.4 ММM testing can be carried out on the weld after construction, during operation, or after repair.
4.5 The following indications can be found during MMM testing:
— zones of probable location of all types of micro- and macro-defects (pores, slag inclusions,
discontinuities, cracks, ruptures);
— SFIs caused by the welding process and SFIs along the welded joints.
4.6 MMM testing can be used for inspection of the weld properties:
— the degree of quality degradation of welds by defects, and the presence of developing defects;
— the quality of welded joints for selection, acceptance and optimization of welding technology.
4.7 The MMM testing temperature range shall be from −20 °C to +60 °С, limited only by the conditions
of the operators and sensors operational range.
4.8 Following MMM testing, conventional non-destructive testing methods shall be applied in zones of
SFIs and probable locations containing micro- and macro-defects. ISO 17635 shall be used for selection
of suitable NDT methods.
4.9 Weld seams are sources of local SF due their geometry, welding process and changes of the
magnetic properties in the heat affected zone (HAZ), weld metal (WM) and parent metal (PM). For more
information, see Bibliographic references [1], [2], [3] as well as the bibliography of ISO 24497-1.
5 Requirements for the inspected object
The requirements for the inspected object (IO) are defined in ISO 24497-1.
6 Testing equipment requirements
The requirements for the test equipment are defined in ISO 24497-1.
7 Preparation for testing
Preparation for testing is described in ISO 24497-1.
8 Test procedure
8.1 General
The mathematical basics of the MMM technique are described in ISO 24497-1.
8.2 Manual inspection of welded joints
Sequences of manual scanning with the sensor of the instrument for evaluation of several types of
welded joints are shown in Figure 1.
2 © ISO 2020 – All rights reserved

Dimensions in millimetres
a) Scanning sequence parallel to the welded joint
b) Scanning sequence perpendicular to the welded joint
Key
1, 2, 3 inspection zones
4 parent metal
5 heat affected zone of welded joint
6 weld material
30-50 width (in mm) of HAZ to be inspected
Figure 1 — Manual scanning sequences of the sensor for evaluation of several types of
welded joints
The magnetic sensor (e.g. flux-gate transducer) is placed perpendicular to the inspection surface. It is
then moved by the operator manually and sequentially:
— first along the entire perimeter of a weld (separately along a weld material and along the heat-
affected zones on both sides of the weld);
— then perpendicular to the weld, with a distance from the edge of the weld of 30 mm to 50 mm on
both sides of the parent material of a pipe, see Figure 1.
The operator records the inspection data in a logbook: magnetic stray field indications with positive
or negative amplitudes of SF (H in A/m). The discontin
...