IEC 60404-8-8:2017

• Abstract:

  IEC 60404-8-8:2017(E) defines the grades of thin non-oriented electrical steel strip and sheet in nominal thicknesses of 0,05 mm, 0,10 mm, 0,15 mm, 0,20 mm, 0,25 mm, 0,30 mm and 0,35 mm and of thin grain-oriented electrical steel strip and sheet in nominal thicknesses of 0,05 mm, 0,10 mm, 0,15 mm and 0,18 mm. In particular, it gives general requirements, magnetic properties, geometric characteristics and tolerances, technological characteristics, as well as inspection procedures.; NOTE For thin non-oriented electrical steel strip and sheet, other nominal thicknesses (i.e. 0,12 mm, 0,18 mm, 0,23 mm and 0,27 mm) can be agreed between the manufacturer and the purchaser.; This document applies to electrical steel strip and sheet supplied in the finally annealed condition in coils or sheets and intended for the construction of magnetic circuits predominantly used at frequencies in the range from 100 Hz to 10 kHz.; This edition includes the following significant technical changes with respect to the previous edition:; - extension of the range of electrical steels to include the improved grades.

• Status: Published
• Publication Date: 25-Jun-2026
• ICS: 29.030 - Magnetic materials
• Technical Committee: TC 68 - Magnetic alloys and steels
• Drafting Committee: JWG 1 - TC 68/JWG 1
• Current Stage: PPUB - Publication issued
• Start Date: 19-Sep-2017
• Completion Date: 06-Oct-2017

• Amended By: IEC 60404-8-8:2017/AMD1:2026 - Amendment 1 - Magnetic materials - Part 8-8: Specifications for individual materials - Thin electrical steel strip and sheet for use at medium frequencies
• Effective Date: 15-Nov-2024

Overview

IEC 60404-8-8:2017 - "Magnetic materials - Part 8-8: Specifications for individual materials - Thin electrical steel strip and sheet for use at medium frequencies" - defines grades, requirements and inspection rules for thin electrical steel intended for magnetic circuits operating predominantly in the 100 Hz to 10 kHz range. The standard covers both non‑oriented (NO) and grain‑oriented (GO) thin electrical steel supplied in the finally annealed condition as coils or sheets, and it extends the family of materials to include improved grades.

Key product ranges:

• Non‑oriented electrical steel nominal thicknesses: 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35 mm (additional thicknesses may be agreed).
• Grain‑oriented electrical steel nominal thicknesses: 0.05, 0.10, 0.15, 0.18 mm.

An example designation format defined by the standard: NO 20‑13 = non‑oriented, 0.20 mm, maximum specific total loss 13 W/kg at 1.0 T.

Key Topics and Technical Requirements

The standard specifies practical and testable attributes including:

• Magnetic properties: classification by maximum specific total loss at 1.0 T (W/kg) and magnetic polarization characteristics for medium‑frequency applications.
• Geometric characteristics and tolerances: thickness, width, edge camber, residual curvature and burr height tolerances for strip and sheet.
• Technological characteristics: density, stacking factor, number of bends (ductility indicator), and insulation coating resistance.
• Production and delivery requirements: production process, form of supply (coils/sheets), final annealed condition, and surface requirements.
• Inspection and testing procedures: sample selection, specimen preparation and referenced test methods for magnetic, geometric and technological tests (see related IEC measurement parts).

Practical Applications and Users

IEC 60404-8-8 is intended for stakeholders involved in design, manufacture and procurement of magnetic components used at medium frequencies:

• Motor and generator designers specifying thin electrical steel for rotors/stators.
• Transformer and inductor manufacturers for medium‑frequency magnetic circuits.
• Steel producers and suppliers who classify and mark thin NO/GO electrical steel grades.
• Quality, testing and inspection laboratories performing magnetic loss, thickness and stacking factor measurements.
• Purchasing engineers negotiating thicknesses, tolerances and coating/stacking requirements.

Using this standard ensures consistent material performance, traceable acceptance tests and compatibility between purchaser requirements and supplier delivery for medium‑frequency magnetic applications.

Related Standards

IEC 60404-8-8 references measurement and test methods in the IEC 60404 series and relevant ISO/IEC delivery and test documents, including standards for:

• Magnetic property measurement at medium frequencies
• Geometrical characteristics and stacking factor tests
• General technical delivery requirements for steel

Keywords: IEC 60404-8-8, thin electrical steel, non‑oriented electrical steel, grain‑oriented electrical steel, medium frequencies, magnetic properties, specific total loss, thickness tolerances, stacking factor, inspection procedures.

IEC 60404-8-8 ®
Edition 2.0 2017-09
INTERNATIONAL
STANDARD
Magnetic materials –
Part 8-8: Specifications for individual materials – Thin electrical steel strip and
sheet for use at medium frequencies

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

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Switzerland www.iec.ch
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IEC 60404-8-8 ®
Edition 2.0 2017-09
INTERNATIONAL
STANDARD
Magnetic materials –
Part 8-8: Specifications for individual materials – Thin electrical steel strip and

sheet for use at medium frequencies

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.030 ISBN 978-2-8322-4805-8

– 2 – IEC 60404-8-8:2017  IEC 2017
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Classification . 7
5 Designation . 7
6 General requirements . 7
6.1 Production process . 7
6.2 Form of supply . 7
6.3 Delivery condition . 8
6.4 Surface condition . 8
6.5 Suitability for cutting . 8
7 Technical requirements . 9
7.1 Magnetic properties . 9
7.1.1 Magnetic polarization . 9
7.1.2 Specific total loss . 10
7.2 Geometric characteristics and tolerances . 10
7.2.1 Thickness . 10
7.2.2 Width . 12
7.2.3 Edge camber . 12
7.2.4 Residual curvature . 12
7.2.5 Burr height . 13
7.3 Technological characteristics . 13
7.3.1 Density . 13
7.3.2 Stacking factor. 13
7.3.3 Number of bends . 13
7.3.4 Insulation coating resistance . 13
8 Inspection and testing . 13
8.1 General . 13
8.2 Selection of samples . 14
8.3 Preparation of test specimens . 14
8.3.1 Magnetic properties . 14
8.3.2 Geometrical characteristics and tolerances . 15
8.3.3 Technological characteristics . 15
8.4 Test methods . 15
8.4.1 General . 15
8.4.2 Magnetic properties . 15
8.4.3 Geometrical characteristics and tolerances . 16
8.4.4 Technological characteristics . 16
8.5 Retests . 17
9 Marking, labelling and packaging . 17
10 Complaints . 17
11 Information to be supplied by the purchaser . 17
Annex A (informative) Optional stacking factor for non-oriented coated products . 18
Annex B (informative) Optional magnetic specifications . 19

Annex C (informative) Calculation of density values . 20
Bibliography . 21

Table 1 – Magnetic and technological characteristics of non-oriented electrical steel
strip and sheet . 9
Table 2 – Magnetic and technological characteristics of grain-oriented electrical steel
strip and sheet . 10
Table 3 – Thickness tolerances . 11
Table 4 – Width tolerance of non-oriented strip and sheet . 12
Table 5 – Width tolerance of grain oriented electrical steel products . 12
Table A.1 – Optional stacking factor for non-oriented coated products . 18
Table B.1 – Optional magnetic specifications for non-oriented electrical steel strip and
sheet . 19

– 4 – IEC 60404-8-8:2017  IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MAGNETIC MATERIALS –
Part 8-8: Specifications for individual materials –
Thin electrical steel strip and sheet for use at medium frequencies

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60404-8-8 has been prepared by IEC technical committee 68:
Magnetic alloys and steels.
This second edition cancels and replaces the first edition published in 1991.
This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
– extension of the range of electrical steels to include the improved grades.

The text of this International Standard is based on the following documents:
CDV Report on voting
68/546/CDV 68/562/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 60404 series, under the general title Magnetic materials, can
be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

– 6 – IEC 60404-8-8:2017  IEC 2017
MAGNETIC MATERIALS –
Part 8-8: Specifications for individual materials –
Thin electrical steel strip and sheet for use at medium frequencies

1 Scope
This part of IEC 60404 defines the grades of thin non-oriented electrical steel strip and sheet
in nominal thicknesses of 0,05 mm, 0,10 mm, 0,15 mm, 0,20 mm, 0,25 mm, 0,30 mm and
0,35 mm and of thin grain-oriented electrical steel strip and sheet in nominal thicknesses of
0,05 mm, 0,10 mm, 0,15 mm and 0,18 mm. In particular, it gives general requirements,
magnetic properties, geometric characteristics and tolerances, technological characteristics,
as well as inspection procedures.
NOTE For thin non-oriented electrical steel strip and sheet, other nominal thicknesses (i.e. 0,12 mm, 0,18 mm,
0,23 mm and 0,27 mm) can be agreed between the manufacturer and the purchaser.
This document applies to electrical steel strip and sheet supplied in the finally annealed
condition in coils or sheets and intended for the construction of magnetic circuits
predominantly used at frequencies in the range from 100 Hz to 10 kHz.
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.
IEC 60050-121, International Electrotechnical Vocabulary – Part 121: Electromagnetism
(available at http://www.electropedia.org/)
IEC 60050-221, International Electrotechnical Vocabulary – Chapter 221: Magnetic materials
and components (available at http://www.electropedia.org/)
IEC 60404-2, Magnetic materials – Part 2: Methods of measurement of the magnetic
properties of electrical steel sheet and strip by means of an Epstein frame
IEC 60404-9, Magnetic materials – Part 9: Methods of determination of the geometrical
characteristics of magnetic steel sheet and strip
IEC 60404-10, Magnetic materials – Part 10: Methods of measurement of magnetic properties
of magnetic steel sheet and strip at medium frequencies
IEC 60404-13, Magnetic materials – Part 13: Methods of measurement of resistivity, density
and stacking factor of electrical steel strip and sheet
ISO 404, Steel and steel products – General technical delivery requirements
ISO 7799, Metallic materials – Sheet and strip 3 mm thick or less – Reverse bend test
ISO 10474, Steel and steel products – Inspection documents

3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-121 and
IEC 60050-221 and the following apply.
3.1
number of bends
number of alternate bends possible before the appearance of the first crack in the base metal
visible to the naked eye
Note 1 to entry The number of bends constitutes an indication of the ductility of the product.
3.2
edge camber
greatest distance between a longitudinal edge of a length of strip or a sheet and the line
joining the two extremities of the measured length of this edge
Note 1 to entry: See IEC 60404-9.
4 Classification
The grades covered by this document are classified according to the maximum value of the
specific total loss in watts per kilogram and according to the nominal thickness of the product
(0,05 mm, 0,10 mm, 0,15 mm, 0,20 mm, 0,25 mm, 0,30 mm and 0,35 mm for non-oriented
electrical steel; 0,05 mm, 0,10 mm, 0,15 mm and 0,18 mm for grain-oriented electrical steel).
5 Designation
The steel name comprises the following in the order given:
a) the characteristic letters:
• NO for non-oriented electrical steel;
• GO for grain-oriented electrical steel;
b) one hundred times the nominal thickness of the product, in millimetres;
c) the specified value of the maximum specific total loss at 1,0 T and the given frequency for
non-oriented electrical steel grades.
EXAMPLE: NO 20-13: non-oriented strip or sheet in nominal thickness of 0,20 mm with a maximum specific total
loss of 13 W/kg at 1,0 T and 400 Hz.
6 General requirements
6.1 Production process
The production process of the steel and its chemical composition are left to the discretion of
the manufacturer.
6.2 Form of supply
The product is supplied in coils in the case of strip and in bundles in the case of sheets.
The mass of the coils or the bundles of sheets shall be agreed between the manufacturer and
the purchaser at the time of enquiry and order.
___________
In the rest of the document, the word “product” is used to mean “strip and sheet”.

– 8 – IEC 60404-8-8:2017  IEC 2017
The recommended value for the internal diameter of coils is 508 mm; however, another value
(e.g. 400 mm) may be agreed for the internal diameter of coils between the manufacturer and
the purchaser.
The strip shall be of constant width and wound in such a manner that the edges are
superimposed in a regular manner and that the side faces of the coil are substantially flat.
The coils shall be sufficiently tightly wound in order that they do not collapse under their own
weight.
The strip may exhibit welds or interleaves resulting from the removal of defective zones,
subject to prior agreement between the manufacturer and the purchaser at the time of enquiry
and order. The value of the additional thickness due to the weld shall be the subject of an
agreement. If necessary, the marking of welds or interleaves may form the subject of a
special agreement.
For coils containing repair welds or interleaves, each part of the strip shall be of the same
grade.
The edges of parts welded together shall not be so much out of alignment as to affect the
further processing of the product.
Sheets which make up each bundle shall be stacked so that the side faces are substantially
flat and approximately perpendicular to the top face.
6.3 Delivery condition
Products according to this document are delivered without coating or with a coating on one or
both sides. Different types of coating can be provided (see IEC 60404-1-1).
6.4 Surface condition
The surfaces shall be smooth and clean, free from grease and rust . Dispersed defects such
as scratches, blisters, cracks, etc. are permitted if they are within the limits of the tolerances
on thickness and if they are not detrimental to the correct use of the supplied products.
The insulation coating present on the surface of the product shall be sufficiently adherent so
that it does not become detached during cutting operations or heat treatment under conditions
specified by the supplier.
If the product is to be immersed in a fluid, an agreement between the manufacturer and the
purchaser, initiated by the purchaser, should be reached to ensure compatibility between the
fluid and the coating.
6.5 Suitability for cutting
The product shall be suitable for cutting accurately into the usual shapes at any point when
appropriate cutting tools are used.
___________
Not to be confused with some coloration of the insulating coating inherent to the manufacturing process.

7 Technical requirements
7.1 Magnetic properties
7.1.1 Magnetic polarization
The specified minimum values of magnetic polarization for a magnetic field strength of
5 000 A/m (peak value) and at 50 Hz for non-oriented electrical steel shall be as given in
Table 1.
Table 1 – Magnetic and technological characteristics
of non-oriented electrical steel strip and sheet
Maximum specific Minimum
total loss at 1,0 T magnetic
Nominal Conventional
b,c
Minimum
Minimum
and polarization
e
thickness density
Steel name s
...

IEC 60404-8-8 ®
Edition 2.1 2026-06
INTERNATIONAL
STANDARD
CONSOLIDATED VERSION
Magnetic materials -
Part 8-8: Specifications for individual materials - Thin electrical steel strip and
sheet for use at medium frequencies
ICS 29.030 ISBN 978-2-8327-1368-6
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or
by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either
IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC copyright
or have an enquiry about obtaining additional rights to this publication, please contact the address below or your local
IEC member National Committee for further information.

IEC Secretariat Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
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CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Classification . 6
5 Designation . 6
6 General requirements . 6
6.1 Production process . 6
6.2 Form of supply . 6
6.3 Delivery condition . 7
6.4 Surface condition . 7
6.5 Suitability for cutting . 7
7 Technical requirements . 8
7.1 Magnetic properties . 8
7.1.1 Magnetic polarization . 8
7.1.2 Specific total loss . 9
7.2 Geometric characteristics and tolerances . 9
7.2.1 Thickness . 9
7.2.2 Width . 11
7.2.3 Edge camber . 11
7.2.4 Residual curvature . 11
7.2.5 Burr height. 12
7.3 Technological characteristics . 12
7.3.1 Density . 12
7.3.2 Stacking factor . 12
7.3.3 Number of bends . 12
7.3.4 Insulation coating resistance . 12
8 Inspection and testing. 12
8.1 General . 12
8.2 Selection of samples . 13
8.3 Preparation of test specimens . 13
8.3.1 Magnetic properties . 13
8.3.2 Geometrical characteristics and tolerances . 14
8.3.3 Technological characteristics . 14
8.4 Test methods . 15
8.4.1 General . 15
8.4.2 Magnetic properties . 15
8.4.3 Geometrical characteristics and tolerances . 15
8.4.4 Technological characteristics . 16
8.5 Retests . 16
9 Marking, labelling and packaging . 16
10 Complaints . 16
11 Information to be supplied by the purchaser . 16
Annex A (informative) Optional stacking factor for non-oriented coated products . 18
Annex B (informative) Optional magnetic specifications . 19
Annex C (informative) Calculation of density values . 20
Annex D (informative) Number of test strips for magnetic property testing . 21
Bibliography . 22

Table 1 – Magnetic and technological characteristics of non-oriented electrical steel
strip and sheet . 8
Table 2 – Magnetic and technological characteristics of grain-oriented electrical steel
strip and sheet . 9
Table 3 – Thickness tolerances . 10
Table 4 – Width tolerance of non-oriented strip and sheet . 11
Table 5 – Width tolerance of grain oriented electrical steel products . 11
Table A.1 – Optional stacking factor for non-oriented coated products . 18
Table B.1 – Optional magnetic specifications for non-oriented electrical steel strip and
sheet . 19
Table D.1 – Number of test strips for magnetic property testing for non-oriented
products . 21

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Magnetic materials -
Part 8-8: Specifications for individual materials -
Thin electrical steel strip and sheet for use at medium frequencies

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC
Publication(s)"). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC 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, IEC had not received notice of a patent, 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 https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
This consolidated version of the official IEC Standard and its amendment has been prepared
for user convenience.
IEC 60404-8-8 edition 2.1 contains the second edition (2017-09) [documents 68/546/CDV and
68/562/RVC] and its amendment 1 (2026-06) [documents 68/795/CDV and 68/803/RVC].
In this Redline version, a vertical line in the margin shows where the technical content is
modified by amendment 1. Additions are in green text, deletions are in strikethrough red text.
A separate Final version with all changes accepted is available in this publication.

International Standard IEC 60404-8-8 has been prepared by IEC technical committee 68:
Magnetic alloys and steels.
This second edition cancels and replaces the first edition published in 1991.
This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
– extension of the range of electrical steels to include the improved grades.
The text of this International Standard is based on the following documents:
CDV Report on voting
68/546/CDV 68/562/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 60404 series, under the general title Magnetic materials, can
be found on the IEC website.
The committee has decided that the contents of this document and its amendment will remain
unchanged until the stability date indicated on the IEC website under webstore.iec.ch in the
data related to the specific document. At this date, the document will be
– reconfirmed,
– withdrawn, or
– revised.
1 Scope
This part of IEC 60404 defines the grades of thin non-oriented electrical steel strip and sheet
in nominal thicknesses of 0,05 mm, 0,10 mm, 0,15 mm, 0,20 mm, 0,25 mm, 0,30 mm and
0,35 mm and of thin grain-oriented electrical steel strip and sheet in nominal thicknesses of
0,05 mm, 0,10 mm, 0,15 mm and 0,18 mm. In particular, it gives general requirements,
magnetic properties, geometric characteristics and tolerances, technological characteristics,
as well as inspection procedures.
NOTE For thin non-oriented electrical steel strip and sheet, other nominal thicknesses (i.e. 0,12 mm, 0,18 mm,
0,23 mm and 0,27 mm) can be agreed between the manufacturer and the purchaser.
This document applies to electrical steel strip and sheet supplied in the finally annealed
condition in coils or sheets and intended for the construction of magnetic circuits
predominantly used at frequencies in the range from 100 Hz to 10 kHz.
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.
IEC 60050-121, International Electrotechnical Vocabulary – Part 121: Electromagnetism
(available at http://www.electropedia.org/)
IEC 60050-221, International Electrotechnical Vocabulary – Chapter 221: Magnetic materials
and components (available at http://www.electropedia.org/)
IEC 60404-2, Magnetic materials – Part 2: Methods of measurement of the magnetic
properties of electrical steel sheet and strip by means of an Epstein frame
IEC 60404-9, Magnetic materials – Part 9: Methods of determination of the geometrical
characteristics of magnetic steel sheet and strip
IEC 60404-10, Magnetic materials – Part 10: Methods of measurement of magnetic properties
of magnetic steel sheet and strip at medium frequencies
IEC 60404-13, Magnetic materials – Part 13: Methods of measurement of resistivity, density
and stacking factor of electrical steel strip and sheet
ISO 404, Steel and steel products – General technical delivery requirements
ISO 7799, Metallic materials – Sheet and strip 3 mm thick or less – Reverse bend test
ISO 10474, Steel and steel products – Inspection documents
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-121 and
IEC 60050-221 and the following apply.
3.1
number of bends
number of alternate bends possible before the appearance of the first crack in the base metal
visible to the naked eye
Note 1 to entry The number of bends constitutes an indication of the ductility of the product.
3.2
edge camber
greatest distance between a longitudinal edge of a length of strip or a sheet and the line
joining the two extremities of the measured length of this edge
Note 1 to entry: See IEC 60404-9.
4 Classification
The grades covered by this document are classified according to the maximum value of the
specific total loss in watts per kilogram and according to the nominal thickness of the product
(0,05 mm, 0,10 mm, 0,15 mm, 0,20 mm, 0,25 mm, 0,30 mm and 0,35 mm for non-oriented
electrical steel; 0,05 mm, 0,10 mm, 0,15 mm and 0,18 mm for grain-oriented electrical steel).
5 Designation
The steel name comprises the following in the order given:
a) the characteristic letters:
• NO for non-oriented electrical steel;
• GO for grain-oriented electrical steel;
b) one hundred times the nominal thickness of the product, in millimetres;
c) the specified value of the maximum specific total loss at 1,0 T and the given frequency for
non-oriented electrical steel grades.
EXAMPLE: NO 20-13: non-oriented strip or sheet in nominal thickness of 0,20 mm with a maximum specific total
loss of 13 W/kg at 1,0 T and 400 Hz.
6 General requirements
6.1 Production process
The production process of the steel and its chemical composition are left to the discretion of
the manufacturer.
6.2 Form of supply
The product is supplied in coils in the case of strip and in bundles in the case of sheets.
The mass of the coils or the bundles of sheets shall be agreed between the manufacturer and
the purchaser at the time of enquiry and order.
The recommended value for the internal diameter of coils is 508 mm; however, another value
(e.g. 400 mm) may be agreed for the internal diameter of coils between the manufacturer and
the purchaser.
___________
In the rest of the document, the word “product” is used to mean “strip and sheet”.
The strip shall be of constant width and wound in such a manner that the edges are
superimposed in a regular manner and that the side faces of the coil are substantially flat.
The coils shall be sufficiently tightly wound in order that they do not collapse under their own
weight.
The strip may exhibit welds or interleaves resulting from the removal of defective zones,
subject to prior agreement between the manufacturer and the purchaser at the time of enquiry
and order. The value of the additional thickness due to the weld shall be the subject of an
agreement. If necessary, the marking of welds or interleaves may form the subject of a
special agreement.
For coils containing repair welds or interleaves, each part of the strip shall be of the same
grade.
The edges of parts welded together shall not be so much out of alignment as to affect the
further processing of the product.
Sheets which make up each bundle shall be stacked so that the side faces are substantially
flat and approximately perpendicular to the top face.
6.3 Delivery condition
Products according to this document are delivered without coating or with a coating on one or
both sides. Different types of coating can be provided (see IEC 60404-1-1).
6.4 Surface condition
The surfaces shall be smooth and clean, free from grease and rust . Dispersed defects such
as scratches, blisters, cracks, etc. are permitted if they are within the limits of the tolerances
on thickness and if they are not detrimental to the correct use of the supplied products.
The insulation coating present on the surface of the product shall be sufficiently adherent so
that it does not become detached during cutting operations or heat treatment under conditions
specified by the supplier.
If the product is to be immersed in a fluid, an agreement between the manufacturer and the
purchaser, initiated by the purchaser, should be reached to ensure compatibility between the
fluid and the coating.
6.5 Suitability for cutting
The product shall be suitable for cutting accurately into the usual shapes at any point when
appropriate cutting tools are used.
___________
Not to be confused with some coloration of the insulating coating inherent to the manufacturing process.
7 Technical requirements
7.1 Magnetic properties
7.1.1 Magnetic polarization
The specified minimum values of magnetic polarization for a magnetic field strength of
5 000 A/m (peak value) and at 50 Hz for non-oriented electrical steel shall be as given in
Table 1.
Table 1 – Magnetic and technological characteristics
of non-oriented electrical steel strip and sheet
Maximum specific Minimum
total loss at 1,0 T magnetic
Nominal Conventional
b,c
Minimum Minimum
and polarization
e
thickness density
Steel name stacking number of
at 50 Hz
a
W/kg d
factor bends 3
for 5 000 A/m
mm kg/dm
at 400 Hz at 1 000 Hz
T
NO 5-45 0,05 – 45 1,50 0,88
2 7,60
NO 10-13 0,10 13 – 1,55 0,91
NO 15-11 11 – 1,55
0,15 0,92 2 7,60
NO 15-14 14 – 1,55
NO 20-13 13 – 1,58
0,20 0,93 2 7,60
NO 20-15 15 – 1,59
NO 25-14 14 – 1,59
0,25 0,94 2 7,60
NO 25-17 17 – 1,60
NO 30-16 16 – 1,59
0,30 0,94 2 7,60
NO 30-19 19 – 1,60
NO 35-19 19 – 1,60 7,60
0,35 0,95 2
NO 35-22 22 – 1,60 7,65
a
Values determined on test specimens without coating. For coated products, the values given in Annex A,
Table A.1 apply.
b
For some steel grades in nominal thicknesses of 0,20 mm; 0,30 mm and 0,35 mm values for the optional
maximum specific total loss at 1,0 T and 700 Hz are given in Annex B and may be agreed between the
manufacturer and the purchaser at the time of enquiry and order.
c
For some steel grades in nominal thicknesses of 0,25 mm and 0,30 mm, values for the optional maximum
specific total loss at 1,0 T and 1 000 Hz are given in Annex B and may be agreed between the manufacturer
and the purchaser at the time of enquiry and order.
d
The values of minimum magnetic polarization at 50 Hz for 2 500 A/m and 10 000 A/m may be agreed
between the manufacturer and the purchaser at the time of enquiry and order (see Annex B).
e
Other values may be agreed between the manufacturer and the purchaser, see Annex C.

The specified minimum values of magnetic polarization for a magnetic field strength of
800 A/m (peak value) and at 50 Hz for grain-oriented electrical steel shall be as given in
Table 2.
Table 2 – Magnetic and technological characteristics
of grain-oriented electrical steel strip and sheet
Steel name Nominal Maximum specific total loss Minimum magnetic Minimum Minimum
thickness polarization stacking number of
W/kg at
at 50 Hz for factor bends
mm
a
H = 800 A/m
1,0 T 1,5 T Frequency T
Hz
GO 5 0,05 24 – 1 000 1,60 0,88 1
GO 10 0,10 – 15 400 1,70 0,91 1
GO 15 0,15 – 16 400 1,70 0,92 1
GO 18 0,18 – 17 400 1,80 0,93 1

NOTE The difference between B and J at 800 A/m amounts up to 0,001 T.
a
It has been common practice for many years to give values of magnetic flux density in tables such as the one
above. In fact the Epstein frame is used to determine magnetic polarization (intrinsic flux density) which is
defined as:
J = B – µ H
where
J is the magnetic polarization;
B is the magnetic flux density;
H is the magnetic field strength;
µ is the magnetic constant.
7.1.2 Specific total loss
The specified values of the maximum specific loss shall be as given in Table 1 and Table 2
and reflect the aged conditions (see 8.3.1).
For grain-oriented electrical steel, they also apply to test specimens that have received, after
cutting, a stress relief heat treatment under conditions specified by the manufacturer.
Depending on the nominal thicknesses, the values are specified at 1,0 T for non-oriented
electrical steel grades and at 1,0 T or 1,5 T for grain-oriented electrical steel grades and at
the frequency specified in Table 1 and Table 2.
7.2 Geometric characteristics and tolerances
7.2.1 Thickness
7.2.1.1 Non-oriented electrical steel products
The nominal thicknesses are 0,05 mm, 0,10 mm, 0,15 mm, 0,20 mm, 0,25 mm, 0,30 mm and
0,35 mm.
For thickness tolerance, a distinction is made between:
• allowable tolerance on the nominal thickness within the same acceptance unit;
• difference in thickness in a sheet or in a length of strip in a direction parallel to the
direction of rolling;
• difference in thickness in a direction perpendicular to the direction of rolling. This
tolerance applies only to materials with a width greater than 25 mm.
At any point the allowable tolerance on the nominal thickness within the same acceptance unit
shall not exceed the values given in Table 3. The additional thickness due to welds, with
respect to the measured thickness of the steel strip shall not exceed 0,050 mm.
The difference in thickness in a length of strip (see 8.3.2) in a direction parallel to the
direction of rolling shall not exceed 10 % for nominal thicknesses of 0,05 mm, 0,10 mm,
0,15 mm, 0,20 mm, 0,25 mm and 8 % for nominal thicknesses of 0,30 mm and 0,35 mm.
The difference in thickness in a direction perpendicular to the direction of rolling shall not
exceed the values given in Table 3.
7.2.1.2 Grain-oriented electrical steel products
The nominal thicknesses are 0,05 mm, 0,10 mm, 0,15 mm and 0,18 mm.
For thickness tolerance, a distinction is made between:
• the allowable tolerance on nominal thickness within the same acceptance unit;
• the difference in thickness in a direction parallel to the direction of rolling;
• the difference in thickness in a direction perpendicular to the direction of rolling. This
tolerance applies only to material with a width greater than 150 mm, the measurement
being made at least 40 mm from the edges.
At any point, the allowable tolerance on the nominal thickness within the same acceptance
unit shall not exceed the values given in Table 3.
The difference in thickness in a length of strip (see 8.3.2) in a direction parallel to the
direction of rolling shall not exceed 0,020 mm.
The difference in thickness in a direction perpendicular to the direction of rolling shall not
exceed the values given in Table 3.
Table 3 – Thickness tolerances
Permitted variation on the nominal Maximum difference in thickness
thickness within the same acceptance unit in a direction perpendicular
to the direction of rolling
Nominal
thickness
mm mm
mm
Non-oriented Grain-oriented Non-oriented Grain-oriented
electrical steel electrical steel electrical steel electrical steel
products products products products
+ 0,010 + 0,010
0,05 0,008 0,008
– 0,005 – 0,005
0,10 ± 0,010 ± 0,010 0,010 0,010
0,15 ± 0,015 ± 0,015 0,020 0,020
0,18 – ± 0,025 – 0,020
0,20 ± 0,020 – 0,020 –
0,25 ± 0,025 – 0,020 –
0,30 ± 0,030 – 0,020 –
0,35 ± 0,030 – 0,020 –
7.2.2 Width
7.2.2.1 Non-oriented electrical steel products
The tolerances given in Table 4 shall apply.
Table 4 – Width tolerance of non-oriented strip and sheet
a
Nominal width l Tolerance
mm mm
+ 0,4
l ≤ 150
+ 0,6
150 < l ≤ 500
+ 1,5
500 < l ≤ 1 250
NOTE By agreement between the manufacturer and the purchaser at the time of
enquiry and order, the tolerances on the nominal width can be all minus values.
a
For nominal width greater than 1 250 mm, the tolerances shall be agreed
between the manufacturer and the purchaser at time of enquiry and order.

7.2.2.2 Grain-oriented electrical steel products
The tolerances given in Table 5 shall apply.
Table 5 – Width tolerance of grain oriented electrical steel products
a
Tolerance
Nominal width l
mm mm
l ≤ 150
– 0,2
150 < l ≤ 400
– 0,3
400 < l ≤ 750
– 0,5
l > 750
– 0,6
a
By agreement between the manufacturer and the purchaser, at the time of
enquiry and order, the tolerances on the nominal width can be all positive.

7.2.3 Edge camber
The verification of edge camber applies only to non-oriented electrical steel in nominal
thicknesses of 0,20 mm, 0,25 mm, 0,30 mm and 0,35 mm and width greater than 150 mm.
The edge camber shall not exceed 1 mm over the measuring length of 1 m.
7.2.4 Residual curvature
A requirement concerning the residual curvature may be specified by agreement between the
manufacturer and the purchaser at the time of enquiry and order for products of width greater
than 150 mm.
7.2.5 Burr height
The measured burr height shall not exceed 0,025 mm for grain-oriented electrical steel
products and 0,03 mm for non-oriented electrical steel products in nominal thicknesses of
0,20 mm, 0,25 mm, 0,30 mm and 0,35 mm, for products supplied with slit edge.
7.3 Technological characteristics
7.3.1 Density
The density of the electrical steel is not specified.
The conventional value of density serving as a basis for the calculation of magnetic properties
and the stacking factor is given in Table 2 for non-oriented electrical steel. For grain-oriented
electrical steel, the density shall be 7,65 kg/dm .
7.3.2 Stacking factor
The specified minimum values for products without coating shall be as given in Table 1 and
Table 2.
For coated non-oriented electrical steel products, informative values of the stacking factor are
given in Table A.1.
7.3.3 Number of bends
7.3.3.1 General
The specified minimum number of bends shall be as given in Table 1 and Table 2.
7.3.3.2 Non-oriented electrical steel products
The value applies to test specimens cut perpendicular to the direction of rolling.
7.3.3.3 Grain-oriented electrical steel products
The value applies to test specimens cut parallel to the direction of rolling.
7.3.4 Insulation coating resistance
The value of the insulation coating resistance may be agreed between the manufacturer and
the purchaser at time of enquiry and order.
8 Inspection and testing
8.1 General
The products defined by this document can be ordered with or without specific inspection in
accordance with ISO 404. However, as a dispensation from ISO 404, in the case of an order
without inspection, the manufacturer shall supply a certificate giving the specific total loss of
the supplied product.
In the case of an order with specific inspection, the type of inspection document in
accordance with ISO 10474 shall be specified when ordering. In this case, the delivery is
divided into acceptance units.
Each acceptance unit shall comprise:
• 10 t for non-oriented electrical steel products in nominal thicknesses of 0,20 mm and
greater;
• 3 t for grain-oriented electrical steel products in nominal thickness of 0,18 mm;
• 1 t for other products;
or the remaining fraction thereof of the same grade and the same nominal thickness. Different
acceptance units can be adopted by special agreement between the manufacturer and the
purchaser at the time of enquiry and order.
For coils of more than the values given above, each coil shall constitute an acceptance unit.
Except by special agreement, the same rules apply to the inspection of the verified
characteristics.
When the products are delivered in the form of slit coils, the test results applying to the parent
unit of acceptance shall apply.
8.2 Selection of samples
Test samples for the acceptance inspection shall be taken from each acceptance unit. The
first internal turn and last external turn of the coils shall be considered as wrapping and not as
representative of the quality of the rest of the coil. The selection shall be made from the first
internal or external turns, excluding the wrapping turn. The selection shall be made away from
weld zones or interleaves.
By choosing a suitable order for the execution of the tests, the same sample shall serve to
check the various properties.
8.3 Preparation of test specimens
8.3.1 Magnetic properties
For the measurement of the magnetic polarization and specific total loss using the 25 cm
Epstein frame in accordance with IEC 60404-2 and IEC 60404-10, the test specimen shall
have a minimum active mass of 240 g for strips of 280 mm long (IEC 60404-2). The test
specimen shall consist of a minimum of 24 Epstein strips or, for the non-oriented products,
the number of test strips related to the steel strip or sheet thickness may be as defined in
Annex D. The Epstein test strips having have the following dimensions:
– length 280 mm to 320 mm, the lengths being equal within a tolerance of ± 0,5 mm;
– width 30 mm ± 0,2 mm.
The number of Epstein strips for the magnetic measurements shall fulfil the requirements of
IEC 60404-2 and IEC 60404-10 as appropriate.
For non-oriented electrical steel products, half the test strips shall be cut parallel to the
direction of rolling and the other half perpendicular giving an even distribution across the
width of the product.
For grain-oriented electrical steel products, all the test strips shall be cut parallel to the
direction of rolling. As far as possible, the selection of test strips shall be made uniformly
across the width of the product.
The test strips shall be carefully cut without deformation. Cutting or punching shall be carried
out only with well-sharpened tools.
The allowable tolerance for the angle between the direction of rolling and the direction of
cutting is:
• ± 5° for non-oriented electrical steel products;
• ± 1° for grain-oriented electrical steel products.
For grain-oriented electrical steel products, before the measurements, the test pieces shall be
subject to the stress relief heat treatment as defined in 7.1.2. For measuring of the specific
total loss on aged pieces, these shall be heated at (225 ± 5) °C for 24 h and shall be cooled
to ambient temperature before testing.
For non-oriented electrical steel products, no further heat treatments such as stress relief
annealing of the test specimen are allowed.
8.3.2 Geometrical characteristics and tolerances
For the measurement of thickness, width, residual curvature and edge camber, the test
specimen shall consist of a 1 m length of strip. However, for the measurement of residual
curvature, a test specimen of 500 mm long may alternatively be used.
8.3.3 Technological characteristics
8.3.3.1 Stacking factor
The test specimen shall consist of strips of the same size, their number being the same as for
the determination of the magnetic properties (see 8.3.1) for the products with a thickness of
0,20 mm or above. Annex D may also be applied for stacking factor testing for the products
with a thickness of 0,20 mm or above.
For thinner grades, equivalent stack heights for the stacking factor test require 32 strips of
0,15 mm thickness, 48 strips of 0,10 mm and 92 strips of 0,05 mm.
The strips shall be have a width of at least 20 mm wide, with and a surface area of at least 5
000 mm , the tolerance on the width and length of strip being respectively equal to ± 0,2 mm
and ± 0,5 mm. The widths and lengths of the strips shall be equal within the tolerances of
±0,2 mm ±0,5 mm respectively.
The test strips shall be carefully deburred before the test.
8.3.3.2 Number of bends
8.3.3.2.1 General
The test specimens shall be carefully cut without deformation.
8.3.3.2.2 Non-oriented electrical steel products
Two test specimens at least 20 mm wide shall be cut perpendicular to the direction of rolling,
at a distance of at least 40 mm from the edge and from the middle and outside any weld
zones.
If the width of the product is not great enough for transverse test specimens of the prescribed
length to be taken, the test specimens shall be taken in the direction of rolling. In this case,
the values in Table 2 also apply.
8.3.3.2.3 Grain-oriented electrical steel products
Five test specimens at least 20 mm wide shall be taken from outside the welding zones,
parallel to the direction of rolling with a view to making the bend perpendicular to the direction
of rolling. The edge of the product shall not constitute one side of the test specimen.
8.4 Test methods
8.4.1 General
For each specified property, one test shall be carried out per acceptance unit. Unless
otherwise specified, the tests shall be made at a temperature of (23 ± 5) °C.
8.4.2 Magnetic properties
The test shall be made using a 25 cm Epstein frame in accordance with IEC 60404-2 or
IEC 60404-10, as appropriate.
8.4.3 Geometrical characteristics and tolerances
8.4.3.1 Thickness
8.4.3.1.1 Non-oriented electrical steel products
For the thickness variation perpendicular to the rolling direction, two thickness measurements
shall be made as follows:
• for products of width over 100 mm (inclusive), at any point located more than 30 mm from
the edges;
• for products of width less than 100 mm, the measurement of thickness shall be made at
any point located more than 10 mm from the edges.
For products of width less than or equal to 25 mm, the measurement shall be made only in the
longitudinal axis of the product.
This measurement shall be made by using a micrometre with an accuracy of 0,001 mm.
8.4.3.1.2 Grain oriented electrical steel products
The measurement of thickness shall be made at any point located more than 40 mm from the
edges.
For products of a width less than 80 mm, the measurement of thickness shall be made along
the longitudinal axis of the product.
This measurement shall be made using a micrometre with an accuracy of 0,001 mm.
8.4.3.2 Width
The width shall be measured perpendicular to the longitudinal axis of the product.
8.4.3.3 Residual curvature
The residual curvature in the longitudinal direction of the strip shall be determined in
accordance with IEC 60404-9.
8.4.3.4 Edge camber
The edge camber shall be determined in accordance with IEC 60404-9.
8.4.3.5 Burr height
The burr height shall be determined in accordance with IEC 60404-9.
8.4.4 Technological characteristics
8.4.4.1 Stacking factor
The stacking factor shall be measured in accordance with IEC 60404-13.
8.4.4.2 Number of bends
The test consists of bending the test specimen through 90° alternately to each side of its
initial position, following the method of bending defined by ISO 7799. The radius of bending
chosen shall be 5 mm.
A bend of 90° from the initial position with return to the initial position counts as one bend.
The test shall be stopped on the appearance in the base metal of the first crack visible to the
naked eye. The last bend shall not be counted.
The test may be stopped when the number of bends is greater than a value agreed between
the manufacturer and the purchaser at the time of enquiry and order.
8.5 Retests
When a test does not give the specified result, this test shall be repeated on double the
number of test specimens from other lengths of strip or sheets of the acceptance unit. The
delivery shall be considered to conform to the order if all the results of the additional tests are
in accordance with the requirements of this document.
After re-treatment, the manufacturer has the right to present again for test acceptance units
which had not been found to comply with the order.
9 Marking, labelling and packaging
Marking, labelling and packaging of the products may be agreed between the manufacturer
and the purchaser at the time of enquiry and order.
10 Complaints
Internal or external defects shall justify a complaint only if they are clearly prejudicial to the
method of working or the judicious use of the product.
The purchaser shall give to the manufacturer the opportunity of convincing himself of the
fairness of the claim by presenting the product in dispute and evidence for the complaint.
In all cases, the terms and conditions of complaints shall be in accordance with ISO 404.
11 Information to be supplied by the purchaser
For a product to comply adequately with the requirements of this standard, the purchaser
shall include the following information in his enquiry and order:
a) the quantity;
b) the type of product (strip or sheet);
c) the number of this standard (IEC 60404-8-8);
d) the steel name or number (see Clause 5);
e) the dimensions of strips or sheets required (including any limitations on the external
diameter of a coil) (see 6.2);
f) any limitations on the mass of coils or bundles of sheets (see 6.2);
g) any special requirement about residual curvature (see 7.2.4);
h) the inspection procedure required including the nature of the related documents (see 8.1).

Annex A
...