IEC 60404-13:2018

IEC 60404-13 ®
Edition 2.0 2018-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Magnetic materials –
Part 13: Methods of measurement of resistivity, density and stacking factor of
electrical steel strip and sheet

Matériaux magnétiques –
Partie 13: Méthodes de mesure de la résistivité, de la masse volumique et du
facteur de foisonnement des bandes et tôles en acier électrique

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.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
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
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 21 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 16 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - webstore.iec.ch/advsearchform IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 67 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
IEC Just Published - webstore.iec.ch/justpublished

Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Catalogue IEC - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
Application autonome pour consulter tous les renseignements
Le premier dictionnaire en ligne de termes électroniques et
bibliographiques sur les Normes internationales,
électriques. Il contient 21 000 termes et définitions en anglais
Spécifications techniques, Rapports techniques et autres
et en français, ainsi que les termes équivalents dans 16
documents de l'IEC. Disponible pour PC, Mac OS, tablettes
langues additionnelles. Egalement appelé Vocabulaire
Android et iPad.
Electrotechnique International (IEV) en ligne.

Recherche de publications IEC -
Glossaire IEC - std.iec.ch/glossary
webstore.iec.ch/advsearchform
67 000 entrées terminologiques électrotechniques, en anglais
La recherche avancée permet de trouver des publications IEC et en français, extraites des articles Termes et Définitions des
en utilisant différents critères (numéro de référence, texte, publications IEC parues depuis 2002. Plus certaines entrées
comité d’études,…). Elle donne aussi des informations sur les antérieures extraites des publications des CE 37, 77, 86 et
projets et les publications remplacées ou retirées. CISPR de l'IEC.

IEC Just Published - webstore.iec.ch/justpublished Service Clients - webstore.iec.ch/csc
Restez informé sur les nouvelles publications IEC. Just Si vous désirez nous donner des commentaires sur cette
Published détaille les nouvelles publications parues. publication ou si vous avez des questions contactez-nous:
Disponible en ligne et aussi une fois par mois par email. sales@iec.ch.

IEC 60404-13 ®
Edition 2.0 2018-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Magnetic materials –
Part 13: Methods of measurement of resistivity, density and stacking factor of

electrical steel strip and sheet

Matériaux magnétiques –
Partie 13: Méthodes de mesure de la résistivité, de la masse volumique et du

facteur de foisonnement des bandes et tôles en acier électrique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20; 29.030 ISBN 978-2-8322-5869-9

– 2 – IEC 60404-13:2018 © IEC 2018
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Determination of the resistivity. 7
4.1 General . 7
4.2 Principles of measurement . 7
4.2.1 Method of determining ρ for an Epstein strip specimen (Method R1) . 7
4.2.2 Method of determining ρ for a rectangular sheet specimen (Method R2)
with supplementary remarks for strip specimen . 8
4.2.3 Determination of thickness d . 9
4.3 Test specimen . 10
4.3.1 Epstein strip specimen . 10
4.3.2 Rectangular sheet specimen . 10
4.4 Apparatus . 10
4.4.1 Common requirements for Method R1 and Method R2 . 10
4.4.2 Requirements for Method R1 . 10
4.4.3 Requirements for Method R2 . 11
4.5 Measuring procedure . 11
4.5.1 Determination of the thickness d of the test specimen . 11
4.5.2 Procedure with strip specimen (Method R1) . 11
4.5.3 Procedure with rectangular sheet specimen (Method R2) . 11
4.6 Reproducibility . 11
4.7 Test report . 12
5 Determination of the density . 12
5.1 General . 12
5.2 Method based on the measurement of resistance (Method D1) . 13
5.2.1 Principles of measurement . 13
5.2.2 Test specimen . 14
5.2.3 Measuring procedure . 14
5.2.4 Reproducibility . 15
5.3 Gas pyknometer method (Method D2) . 15
5.3.1 Principles of measurement . 15
5.3.2 Test specimen . 15
5.3.3 Test apparatus . 15
5.3.4 Measuring procedure . 15
5.3.5 Reproducibility . 15
5.4 Test report . 15
6 Determination of the stacking factor. 16
6.1 General . 16
6.2 Test specimen . 16
6.3 Measuring procedure . 16
6.4 Reproducibility . 17
6.5 Test report . 17
Annex A (informative) An example of the apparatus for the measurement of the
resistivity using a rectangular sheet specimen (Method R2) . 19

Annex B (informative) An example of the determination of density using the gas
pyknometer method (Method D2) . 20
B.1 Overview. 20
B.2 Test specimen . 20
B.3 Apparatus . 21
B.4 Calibration . 21
B.5 Measuring procedure . 21
B.6 Repeatability . 22
Annex C (informative) Calculation of density based on silicon and aluminium content

(Method D4) . 23
Bibliography . 24

Figure 1 – Circuit for the measurement of resistance of an Epstein strip specimen
(Method R1) . 7
Figure 2 – Circuit for the measurement of resistance of a rectangular sheet specimen
(Method R2) . 8
Figure 3 – Experimental data and the regression line of the density ρ against the
m
product ρ ·ρ for non-oriented electrical steel sheet [6] . 13
m
Figure 4 – Schematic diagram of stacking specimen and rams . 17
Figure A.1 – Schematic cross-sectional view of the arrangement of the contact holder . 19
Figure B.1 – Diagram illustrating the two-chamber pressure gas pyknometer . 21

Table B.1 – Number of test discs of diameter 36 mm . 20

– 4 – IEC 60404-13:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MAGNETIC MATERIALS –
Part 13: Methods of measurement of resistivity, density
and stacking factor of electrical steel strip and sheet

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 60404-13 has been prepared by IEC Technical Committee 68:
Magnetic alloys and steels.
This second edition cancels and replaces the first edition published in 1995 and constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the sequence of the density and resistivity sections is changed and the title of the
document revised to reflect this;
b) the van-der-Pauw method (Method R2) is also applicable to Epstein strip specimens;
c) the gas pyknometer method is introduced, and the liquid immersion method and the
calculation method based on the chemical composition are quoted;

d) the requirements of the stacking factor section, such as the tolerance of the dimensions of
the test specimen and the repeatability of measurement, are changed;
e) an example of the apparatus for determination of the resistivity using a rectangular sheet,
which was previously part of the main body of the text, is moved to constitute informative
Annex A;
f) an example of the determination of the density by using the gas pyknometer method is
added as an informative Annex B;
g) an example of the determination of density based on the calculation of silicon and
aluminium contents is added as an informative Annex C.
The text of this International Standard is based on the following documents:
CDV Report on voting
68/574/CDV 68/586A/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 web site.
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.
– 6 – IEC 60404-13:2018 © IEC 2018
MAGNETIC MATERIALS –
Part 13: Methods of measurement of resistivity, density
and stacking factor of electrical steel strip and sheet

1 Scope
This part of IEC 60404 specifies the methods used for determining the resistivity, density and
stacking factor of grain-oriented and non-oriented electrical steel strip and sheet. These
quantities are necessary to establish the physical characteristics of the material. Moreover,
the density is necessary to allow specified values of the magnetic polarization, resistivity and
stacking factor to be determined.
Since these properties are functions of temperature, the measurements will be made at an
ambient temperature of (23 ±5) °C except when specified in this document.
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
IEC 60050-221, International Electrotechnical Vocabulary – Chapter 221: Magnetic materials
and components
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 60404-3, Magnetic materials – Part 3: Methods of measurement of the magnetic
properties of magnetic sheet and strip by means of a single sheet tester
ISO 1183-3, Plastics – Methods for determining the density of non-cellular plastics – Part 3:
Gas pyknometer method
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-121,
IEC 60050-221 and ISO 1183-3 apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp

4 Determination of the resistivity
4.1 General
Two methods for the determination of the resistivity of a test specimen are described in this
document; Method R1 using an Epstein strip specimen, and Method R2 using a rectangular
sheet specimen.
NOTE Method R2 is based on the van-der-Pauw (VDP) method [1] which is based on the theory of conformal
mapping of two-dimensional fields. For a body of uniform thickness and arbitrary shape, an exact mathematical
formula exists for the resistivity determined from the voltage to current ratio obtained using four contacts. The
formula is simplified when specimens and contact positions are highly symmetrical. Method R2 is particularly
appropriate for rectangular sheet specimens.
The method of determination of the resistivity ρ, based on the measurement of the geometric
dimensions of the test specimen including the thickness, can be applied to all types of
material specimens. However, the method for further use to determine the density ρ in
m
accordance with 5.2 is restricted to the materials as specified in 5.1.
4.2 Principles of measurement
4.2.1 Method of determining ρ for an Epstein strip specimen (Method R1)
The circuit for the measurement of the resistance of an Epstein strip specimen shall be
connected as shown in Figure 1. Two electrical contacts A and B shall be arranged on either
end of the shorter sides of the test specimen to supply a homogeneous current through the
test specimen in the longitudinal direction. Two electrical contacts, C and D, located inside
the contacts A and B shall be arranged on a longer side edge of the test specimen to measure
the voltage over the length l . It is not necessary to remove the oxide layer or other insulating
e
coatings because the contacts are made at the cut edges of the specimen.
A
Specimen
C
A
I
AB
l
V
e
Power
S U
supply
CD
D
B
IEC
Key
A, B, C, D electrical contact I current flowing between A and B
AB
A DC ammeter S switch for current reversal
U
V DC voltmeter voltage between C and D
CD
l distance between C and D
e
Figure 1 – Circuit for the measurement of resistance of
an Epstein strip specimen (Method R1)
____________
Numbers in square brackets refer to the Bibliography.

– 8 – IEC 60404-13:2018 © IEC 2018
If a current flows homogeneously through the test specimen, the resistance R of the material
over the length l of the Epstein strip specimen shall be determined according to Ohm’s law
e
as follows:
U
CD
R = (1)
I
AB
where
R is the resistance of the material over the length l between the contacts C and D,
e
in ohms;
U is the voltage between the contacts C and D, in volts;
CD
I is the current flowing between the contacts A and B, in amperes.
AB
The resistivity ρ shall be determined from the following formula:
R ∙ b ∙ d
ρ = (2)
l
e
where
ρ is the resistivity of the material of the test specimen, in ohm metres;
b is the width of the test specimen, in metres;
d is the thickness of the test specimen without an insulation layer, in metres;
l is the distance between the contacts C and D, in metres.
e
4.2.2 Method of determining ρ for a rectangular sheet specimen (Method R2) with
supplementary remarks for strip specimen
The circuit for the measurement of the resistance of a square-shaped or rectangular sheet
specimen shall be connected as shown in Figure 2. Four electrical contacts A, B, C and D
shall be arranged symmetrically at the centre of each edge of the test specimen. The contacts
A, B, C and D shall be as small as possible. With a current flowing through the contacts A and
B, the voltage between the contacts C and D shall be measured. It is not necessary to remove
oxide layer or other insulating coatings because the contacts are made at the cut edges of the
specimens.
B
I A
AB 1
Power
S
C
supply A
Specimen
V
U
CD
D
IEC
Key
A, B, C, D electrical contact I current flowing between A and B
AB
A DC ammeter S switch for current reversal
V DC voltmeter U voltage between C and D
1 CD
Figure 2 – Circuit for the measurement of resistance of
a rectangular sheet specimen (Method R2)

The resistance R shall be calculated according to the following formula:
AB,CD
U
CD
R = (3)
AB,CD
I
AB
where
R is the resistance measured between the contacts C and D, in ohms;
AB,CD
U is the voltage between the contacts C and D, in volts;
CD
I is the current flowing between the contacts A and B, in amperes.
AB
Correspondingly, the resistance R shall be obtained from the voltage between the
BC,DA
contacts D and A and the current flowing through the contacts B and C.
On the basis of the theory of conformal mapping of two-dimensional fields [1], for a body of
uniform thickness and arbitrary shape, the following formula holds:
π ∙ d R + R
AB, CD BC, DA
ρ = ∙ ∙ F (4)
ρ
ln 2 2
where
ρ is the resistivity of the material of the test specimen, in ohm metres;
d is the thickness of the test specimen without insulation layer, in metres;
R
AB, CD
F is a function of the ratio only.
ρ
R
BC, DA
R
AB, CD
If the ratio is close to unity, the function F becomes 1, so that it can be omitted [1]. To
ρ
R
BC, DA
ensure that this ratio is close to unity, the contacts shall be arranged symmetrically at the
centres of the edges of the rectangular sheet specimen as shown in Figure 2.
Method R2 can also be applied to Epstein strip specimen offering the advantage that the
same base plate and contact holders (see Annex A) as for the rectangular sheet specimens
can be used, in this case, to obtain a reliable result of the measurement, a certain number
(e.g. > 10) of Epstein strip specimens should be tested, and the average should be taken as
the result.
NOTE It has been shown that Method R2 (van der Pauw method [1]) is equivalent to Method R1, within limits
which are lower than the dispersion between individual strip specimens of one grade of material [2]. The Method
R2 has the advantages of versatility of specimen shape [3].
4.2.3 Determination of thickness d
4.2.3.1 General
The thickness of the test specimen d used in Formulae (2) and (4) shall be determined as
specified in 4.2.3.2.
4.2.3.2 Calculating the thickness from the density ρ
m
The thickness of the test specimen d shall be calculated using the value of the density ρ
m
determined as specified in 5.3, or supplied by the manufacturer. The thickness d shall be
determined from the following formula:
m
d = (5)
ρ ∙ b ∙ l
m
– 10 – IEC 60404-13:2018 © IEC 2018
where
m is the mass of the test specimen, in kilograms;
ρ is the density of the material of the test specimen, in kilograms per cubic metre;

m
b is the width of the test specimen, in metres;
l is the length of the test specimen, in metres.
4.3 Test specimen
4.3.1 Epstein strip specimen
The Epstein strip specimen used in Method R1 (according to 4.2.1), conforming with
IEC 60404-2, shall have the following dimensions:
– width b = 30 mm ±0,2 mm;
– length 280 mm ≤ l ≤ 320 mm with a tolerance of ± 0,5 mm.
4.3.2 Rectangular sheet specimen
The dimensions of the square-shaped or rectangular sheet specimen used in Method R2
(according to 4.2.2), conforming with IEC 60404-3, shall be as follows:
– width 300 mm ≤ b ≤ 500 mm with a tolerance of ± 0,5 mm;
– length 500 mm ≤ l ≤ 610 mm with a tolerance of ± 0,5 mm.
4.4 Apparatus
4.4.1 Common requirements for Method R1 and Method R2
The following equipment is required:
– according to 4.2.3.2, a calibrated balance, capable of weighing the mass of the test
specimen to within ± 0,1 %;
– a power supply consisting of a stable low voltage DC current source capable of supplying
a current of the order 1 A to 10 A (unless a four-terminal ohm meter is used, as specified
in 4.5.2 and 4.5.3);
– a resistance measuring device (e.g. ammeter and voltmeter of accuracy ± 0,1 % or better,
or a Kelvin bridge or a four-terminal ohm meter of corresponding accuracy) capable of
measuring the resistance R of the test specimen to within ± 1 %;
– a jig for making contact with the test specimen (as specified in 4.4.2 and 4.4.3) and,
between the contacts, a supporting flat plate smaller than the test specimen (on sides
where contacts are arranged) but not by more than 5 mm (10 mm for rectangular sheet
specimens) on each side. The thickness of the support shall allow the contacts to touch
the specimen lying on the support.
4.4.2 Requirements for Method R1
The apparatus for making electrical contact with the strip specimen employs four contacts:
two voltage contacts (tips) are mounted on a removable bridge and two current contacts are
fixed to the base plate. The four contacts shall be arranged so that the two voltage contacts C
and D lie on a longer edge of the strip between the current contacts A and B (see Figure 1).
The current contacts shall be arranged symmetrically in the centre of each of the shorter
edges of the strip within ± 0,5 mm. The two voltage contacts shall have a relatively sharp
edge (e.g. with a radius of curvature of 1 mm). The distance l between the voltage contacts
e
C and D shall exceed 200 mm. The minimum distance between the voltage contacts and the
current contacts shall be not less than the width of the test specimen (the distance l between
e
the tips shall be determined within ± 0,5 mm, see Figure 1).

4.4.3 Requirements for Method R2
Four contacts with a relatively sharp edge (e.g. with a radius of curvature of 1 mm) shall each
be mounted on a holder which is fixed to the base plate. The contacts shall be arranged
symmetrically in the centre of each edge of the specimen, within ± 1 mm (or ± 0,5 mm for an
Epstein strip specimen) (see Figure 2).
NOTE 1 Annex A gives an example of the apparatus for Method R2.
NOTE 2 Other modes such as soldering electrical wires to the test specimen at the points A, B, C and D of the
rectangular test specimen (see Figure 2) can be used to provide good electrical contact.
4.5 Measuring procedure
4.5.1 Determination of the thickness d of the test specimen
The thickness d of the test specimen shall be determined as specified in 4.2.3.2. The length l
and width b of the test specimen shall be determined using the required length measuring
device, and the mass m of the test specimen shall be determined using the required balance.
4.5.2 Procedure with strip specimen (Method R1)
The circuit connections shall be made as shown in Figure 1. A current I having a value
AB
between 1 A and 5 A that depends on the thickness and properties of the material and that is
sufficient to give a value of the voltage U of the specified accuracy shall be passed through
CD
the test specimen. If a four-terminal ohm meter having the required measurement accuracy is
used, a lower value of the current is permitted. The values of the voltage U and the current
CD
I shall be recorded except when using a four-terminal ohm meter or a Kelvin bridge to
AB
measure resistance directly. To reduce contributions from thermal voltages, the current shall
then be reversed and set to the same value, the value of the voltage U recorded and the
CD
average of the two readings calculated.
The resistance R shall then be calculated using Formula (1) except when using a four-terminal
ohm meter or a Kelvin bridge to measure resistance directly.
The resistivity ρ shall be calculated using Formula (2) combined with Formula (5).
4.5.3 Procedure with rectangular sheet specimen (Method R2)
The circuit connections shall be made as shown in Figure 2. A current having a value between
2 A and 10 A, that is sufficient to give a reading of the voltage U to the specified accuracy,
CD
shall be passed via the contacts A and B through the test specimen. If a four-terminal ohm
meter having the required measurement accuracy is used, a lower value of the electric current
is permitted. The values of the voltage, U , and the current, I , shall be recorded except
CD AB
when using a four-terminal ohm meter or a Kelvin bridge to measure resistance directly. To
reduce contributions from thermal voltages, the current shall then be reversed and set to the
same value, the value of the voltage U recorded, and the average of the two readings
CD
calculated.
The resistance R shall then be calculated using Formula (3) except when using a
AB,CD
four-terminal ohm meter or a Kelvin bridge to measure resistance directly. Correspondingly,
the resistance R shall be measured following the same procedure.
BC,DA
The resistivity ρ shall be calculated using Formula (4) combined with Formula (5).
4.6 Reproducibility
According to comparing experiments [3], the reproducibility of the methods for the
determination of the resistivity in accordance with Clause 4 is characterized by a relative
standard deviation of 0,5 %.
– 12 – IEC 60404-13:2018 © IEC 2018
4.7 Test report
The test report shall refer to this document and include the following information, as
applicable:
a) all details necessary for complete identification of the specimens, such as the type or
grade of material, nominal thickness;
b) the width b, and the length l of the test specimen, in metres;
c) the mass m of the test specimen, in kilograms;
d) the test method adopted (if Method R2 is used with Epstein strip specimen, number of
specimens should be indicated);
e) the ambient temperature at which the measurement was made, in Celsius;
-8
f) the test result of resistivity ρ, in ohm metres, rounded to the nearest 0,1 × 10 Ω·m.
5 Determination of the density
5.1 General
The following four methods for the determination of the density are described in this document:
– Method D1, based on measurement of the resistivity using a specimen strip or using a
rectangular sheet specimen;
– Method D2, gas pyknometer method according to ISO 1183-3. This is a fundamental
method;
– Method D3, liquid immersion method according to ISO 1183-1:2012 [4] and ISO 2738:1999
[5];
– Method D4, theoretical calculation method based on chemical composition of the
specimen, as given in Annex C.
Method D1 is an indirect measurement method based on Methods R1 and R2 of Clause 4 on
resistivity determination. Method D1 as specified in 5.2 is applicable only to non-oriented
electrical steel with the following range of chemical compositions:
– silicon: C ≤ 4 %;
Si
– aluminium: 0,17 C – 0,28 ≤ C ≤ 0,17 C + 0,28 and C ≥ 0;
Si Al Si Al
– total of other alloy constituents: C ≤ 0,4 %,
res
where
C is the mass fraction of silicon, in percentage;
Si
C is the mass fraction of aluminium, in percentage;
Al
C is the mass fraction of total alloy constituents other than silicon and aluminium, in
res
percentage.
If the chemical composition is not known, it shall be verified before using this indirect method.
Generally, the chemical composition of electrical steel is left to the discretion of the
manufacturer.
Method D2 is a direct measurement method as specified in 5.3 and applicable for grain-
oriented and non-oriented electrical steel.
Method D3 is a direct measurement method called the liquid immersion method, according to
ISO 1183-1:2012 [4] and ISO 2738:1999 [5].
NOTE 1 For the determination of the density, the liquid immersion method was earlier considered to be a
fundamental method for use in cases of arbitration. However, experience has shown that this method is difficult to
use in the case of sheet specimens of electrical steel with a relatively large surface area because of the influence
of residual air bubbles adhering to the surface which are not easily removed. In contrast, the gas pyknometer

method according to ISO 1183-3 is more practical and can lead to higher accuracy for sheet specimens of
electrical steel.
Method D4 is an indirect measurement method based on the theoretical calculation of the
chemical composition of the test specimen, which should be used by agreement between the
parties concerned. An example of the calculation of the density, through consideration of the
silicon and aluminium content, is given in Annex C.
NOTE 2 Manufacturers can determine the density of material by the testing of thicker specimens where it is easier
to determine the volume by dimensional measurement during the manufacturing process of the material.
5.2 Method based on the measurement of resistance (Method D1)
5.2.1 Principles of measurement
7,90
7,80
7,70
7,60
100 200 300 400
–5 2
ρ × ρ , 10 Ω × kg/m
m
IEC
Key
Symbols ○ and □ are for resistivity Method R1 and Method R2 respectively. See [6] for details.
Figure 3 – Experimental data and the regression line of the density ρ against
m
the product ρ ·ρ for non-oriented electrical steel sheet [6]
m
In the case of materials specified in 5.1 for Method D1, experience has shown that the
relationship between the density ρ and the product of density and resistivity ρ ·ρ is a simple,
m m
almost linear one [6], as shown in Figure 3. Thus, it is possible to determine the density of the
material by the determination of the product ρ ·ρ, based on the measurement of the
m
resistance, mass and geometrical dimensions of the test specimen.
NOTE 1 Both the density ρ and the resistivity ρ are functions of the silicon and aluminium content.
m
3 3
ρ , 10 kg/m
m
– 14 – IEC 60404-13:2018 © IEC 2018
The linear function as shown in Figure 3, obtained by linear regression from experimental
data [6], follows the empirical relation:
ρ = 7 975 – 89 000 × (ρ ·ρ) (6)

m m
where
ρ ·ρ is the value of the product of density and resistivity of the test specimen, in
m
ohm kilograms per square meter.
NOTE 2 This relationship has been established by careful and statistical application of the liquid immersion
method [6] taking the usual impurities of non-oriented material into account. The product ρ ·ρ for the two different
m
types of test specimen used for the Epstein frame (Method R1) and the rectangular sheet test method (Method R2)
are determined in accordance with Clause 4.
5.2.2 Test specimen
5.2.2.1 Epstein strip specimen
In the case of using an Epstein strip specimen as specified in 4.2.1, the relationship between
the product ρ ·ρ and the resistance R of the test specimen is given in Formula (7) deduced
m
from Formulae (2) and (5):
R ∙ m
ρ ·ρ = (7)
m
l ∙ l
e
Then the value of the density ρ shall be calculated as follows, deduced from Formulae (6)
m
and (7):
m
ρ = 7 975 – 89 000 × ∙ R (8)
m
l ∙ l
e
5.2.2.2 Rectangular sheet specimen
In the case of using a square-shaped or rectangular sheet specimens as specified in 4.2.2,
the relationship between the product ρ ·ρ and the resistance R of the test specimen is given
m
in Formula (9) deduced from Formulae (4) and (5), with F = 1:
ρ
R + R
π ∙ m
AB, CD BC, DA
ρ ·ρ = ∙ (9)
m
l ∙ b ∙ ln 2 2
Then the value of the density ρ shall be calculated as follows, deduced from Formulae (6)
m
and (9):
π ∙ m R + R
AB, CD BC, DA
ρ = 7 975 – 89 000 × ∙ (10)
m
l ∙ b ∙ ln 2
5.2.3 Measuring procedure
When using an Epstein strip specimen, the resistance R shall be measured as specified in
4.5.2. The value of ρ shall be calculated using Formula (8). It can also be read from Figure 3
m
with the value of the product ρ ·ρ determined from Formula (7).
m
When using a rectangular sheet specimen (or Epstein strip specimen), the resistance R
AB,CD
and R shall be measured as specified in 4.5.3. The value of ρ shall be calculated using
BC,DA m
Formula (10). It can also be read from Figure 3 with the value of the product ρ ·ρ determined
m
from Formula (9).
5.2.4 Reproducibility
The reproducibility of the method, based on the product ρ ·ρ in accordance with 5.2.1, is
m
estimated to be characterized by a relative standard deviation of the density of 1,0 %.
5.3 Gas pyknometer method (Method D2)
5.3.1 Principles of measurement
The gas pyknometer method is to determine the volume (and thus the density) of solids as
specified in ISO 1183-3.
NOTE The gas pyknometer is not a particular method for magnetic materials but is widely used in industry to
determine the volume of regular or irregular forms of materials, such as porous, powdered or granular solids.
5.3.2 Test specimen
It is necessary to remove all the oxide or other insulating coating on the test specimen by
grinding or by means of an alternative suitable physical or chemical method.
The test specimen should be cut or punched to a shape convenient for the size of the
pyknometer cell used.
In order to obtain a better accuracy of measurement, the amount of the specimen selected
should be the optimum for the pyknometer cell used. The mass of the test specimen should
not be less than 200 g.
Before starting measurements, the test specimen should be free from any grease or rust.
Where pre-treatment is required, care should be taken to avoid any pollution which could
influence the measurement of the density of the test specimen. If the test specimen is heated
in order to dry it after treatment, it should be left to cool to ambient temperature before the
measurement of density is performed.
5.3.3 Test apparatus
The apparatus required to determine the volume (and thus the density) of a specimen of
electrical steel sheet should be as specified in ISO 1183-3.
5.3.4 Measuring procedure
The measuring procedure shall include the specimen preparation according to 5.3.2 and
follow the instructions as specified in ISO 1183-3.
Annex B gives an example of the determination
...