ISO 23475-1:2021

Testing method for steel tyre cord - Part 1: General requirements

This document specifies test methods of steel cords which are used for tyre reinforcement. Dimension, process properties, mechanical properties and coating test method are all included.

Méthode d'essai pour les câbles de pneumatiques en acier — Partie 1: Exigences générales

General Information

• Status: Published
• Publication Date: 09-Feb-2021
• ICS: 77.140.65 - Steel wire, wire ropes and link chains
• ICS: 83.160.01 - Tyres in general
• Technical Committee: ISO/TC 17/SC 17 - Steel wire rod and wire products
• Drafting Committee: ISO/TC 17/SC 17/WG 10 - Non-parallel steel wire and cords for tyre reinforcement
• Current Stage: 6060 - International Standard published
• Start Date: 10-Feb-2021
• Due Date: 25-Sep-2021
• Completion Date: 10-Feb-2021

Overview - ISO 23475-1:2021 (Testing method for steel tyre cord - Part 1: General requirements)

ISO 23475-1:2021 specifies standardized test methods for steel cords used in tyre reinforcement. Part 1 provides the general requirements covering dimensional measurements, process properties, mechanical properties and coating characterization. The standard defines accepted test principles, apparatus, procedures, result expression and test report content to ensure consistent evaluation of steel tyre cord quality.

Key topics and technical requirements

The standard addresses a comprehensive set of test areas for steel tyre cord, including:

• Dimension

  • Cord diameter measurement methods (micrometre, profile projector)
  • Unravelled filament diameter, linear density, lay direction and lay length (trace and untwisting methods)

• Process properties

  • Straightness, arc height, flare and residual torsion with defined principles, apparatus and procedures

• Mechanical properties

  • Breaking load and elongation at fracture
  • Elongation between defined forces (EDF)
  • Loop (elasticity) test - each with test setup, execution and reporting requirements

• Coating mass and composition

  • Determination by X‑Ray fluorescence spectroscopy (WDXRFS or EDXRFS)
  • Sample preparation, reagents (e.g., acetone, ammonium persulphate, ammonia), stripping solution formulation, calibration standards, and reporting of results

The document references normative standards (for example, ISO 17832 for related terms) and follows ISO reporting conventions for traceability and reproducibility.

Practical applications and who uses this standard

ISO 23475-1 is directly applicable to organizations involved in tyre reinforcement materials and testing:

• Tyre manufacturers - for incoming material inspection and supplier qualification of steel cords.
• Steel wire and cord producers - to validate product specifications and maintain production quality.
• Independent testing laboratories - to perform accredited tests for compliance and certification.
• R&D and quality engineers - to compare materials, optimize cord designs and document test results consistently.
• Procurement and standards teams - to specify acceptance criteria and ensure conformity across suppliers.

Using ISO 23475-1 helps ensure consistent material performance, enhances interchangeability between suppliers, supports regulatory and contractual compliance, and reduces variability in tyre reinforcement performance.

Related standards

• ISO 23475 series (other parts as listed by ISO)
• ISO 17832 - referenced for terms and definitions relevant to steel wire and cords

Keywords: ISO 23475-1, steel tyre cord testing, tyre reinforcement, cord diameter, coating analysis, X‑Ray fluorescence, mechanical properties, process properties.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 23475-1
First edition
2021-02
Testing method for steel tyre cord —
Part 1:
General requirements
Méthode d'essai pour les câbles de pneumatiques en acier —
Partie 1: Exigences générales
Reference number
©
ISO 2021
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
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ISO copyright office
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Published in Switzerland
ii © ISO 2021 – All rights reserved

Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Dimension . 1
4.1 Cord diameter . 1
4.1.1 Measure with micrometre . 1
4.1.2 Measure with profile projector . 3
4.2 Unravelled filament diameter . 4
4.2.1 Principle . 4
4.2.2 Apparatus . 4
4.2.3 Procedure . 5
4.2.4 Expression of results . 5
4.2.5 Test report . 5
4.3 Linear density . 5
4.3.1 Principle . 5
4.3.2 Apparatus . 5
4.3.3 Procedure . 6
4.3.4 Test report . 6
4.4 Lay direction and lay length . 6
4.4.1 Lay direction/direction of lay . 6
4.4.2 Trace method for lay length . 6
4.4.3 Untwisting method for lay length . 8
5 Process property . 9
5.1 Straightness . 9
5.1.1 Principle . 9
5.1.2 Apparatus . 9
5.1.3 Procedure . 9
5.1.4 Test report . 9
5.2 Arc height . 9
5.2.1 Principle . 9
5.2.2 Apparatus .10
5.2.3 Procedure .10
5.2.4 Test report .10
5.3 Flare .10
5.3.1 Principle .10
5.3.2 Apparatus .10
5.3.3 Procedure .10
5.3.4 Test report .11
5.4 Residual torsion .11
5.4.1 Principle .11
5.4.2 Apparatus .11
5.4.3 Procedure .11
5.4.4 Test report .11
6 Mechanical property .12
6.1 Breaking load and elongation at fracture .12
6.1.1 Principle .12
6.1.2 Apparatus .12
6.1.3 Procedure .12
6.1.4 Test report .13
6.2 Elongation between defined forces (EDF) .13
6.2.1 Principle .13
6.2.2 Apparatus .14
6.2.3 Procedure .15
6.2.4 Test report .15
6.3 Loop test (Elasticity) .15
6.3.1 Principle .15
6.3.2 Apparatus .15
6.3.3 Procedure .16
6.3.4 Test report .17
7 Determination of mass and composition of coating by X-Ray fluorescence spectroscopy .17
7.1 Principle .17
7.2 Apparatus .17
7.2.1 WDXRFS or EDXRFS .17
7.2.2 Analytical balance, which can be read to the nearest 0,001 g. .17
7.2.3 Dispenser, with the accuracy of 25,00 ml ± 0,05 ml. .17
7.2.4 X/Y shaker, with variable frequency. .17
7.3 Reagents.17
7.3.1 Acetone or diethyl ether .17
7.3.2 Ammonium persulphate (mass fraction >98 %) .17
7.3.3 Ammonia (mass fraction >25 %, not more than “d=0,91” at temperature 20 °C) 17
7.3.4 Stripping solution, for 1 l: weigh 16 g ammonia persulphate into a
beaker of 600 ml and dissolve in 400 ml demineralized water. Transfer
quantitatively into a 1 l volumetric flask. Add 120 ml ammonia. Fill up to
the mark with demineralized water. Shake well. .17
7.3.5 Standard, the matrix and range should cover the sample range. Prepare
the calibration standards according to the XRFS user’s manual or
according to an example in Table 1. .17
7.4 Preparation of test samples .18
7.5 Procedure .18
7.6 Expression of results .18
7.7 Test report .19
iv © ISO 2021 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 17, Steel, Subcommittee SC 17, Steel wire
rod and wire products.
A list of all parts in the ISO 23475 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
INTERNATIONAL STANDARD ISO 23475-1:2021(E)
Testing method for steel tyre cord —
Part 1:
General requirements
1 Scope
This document specifies test methods of steel cords which are used for tyre reinforcement. Dimension,
process properties, mechanical properties and coating test method are all included.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 17832, Non-parallel steel wire and cords for tyre reinforcement
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 17832 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Dimension
4.1 Cord diameter
4.1.1 Measure with micrometre
4.1.1.1 Principle
Hold the sample between two parallel circular faced anvils of a micrometre. Close the movable anvil
gradually and gently until it is in contact with the specimen. Read the value on the micrometre.
4.1.1.2 Apparatus
4.1.1.2.1 Micrometre
A precision disk micrometre with non-rotate spindle is suggested. This micrometre may have a hole
(maximum 8 mm) in the centre of the anvils (see Figure 1).
Measuring range is from 0 mm to 25 mm. Resolution is 0,001 mm.
Anvil type: the diameter of the anvils shall be greater than one lay length (min. 20 mm in diameter).
Measuring force range: <10 N. It is suggested from 3 N to 5 N.
The anvils shall be plane within 0,002 mm and parallel within 0,005 mm.
Figure 1 — Disk micrometre
4.1.1.2.2 Fusing machine
4.1.1.3 Procedure
a) Clean the surface of the anvils with clean paper. Verify whether the micrometre reads 0,000 when
the anvils are closed for each measurement.
b) Fuse a specimen to a length about 150 mm and ensure that cord end is well secured with no
unravelling. Place the sample in the centre of the anvils.
c) Close the movable anvil gradually and gently until it is in contact with the specimen. For normal
cords, stop rotating the spindle when 3 ‘click’ are heard and for HE, HI and OC constructions only 1
“click” is heard.
d) Axially rotate the sample between repeated measurements in order to find the maximum diameter
(D ) and minimum diameter (D ).
1 2
Figure 2 — Diameter test diagram
4.1.1.4 Expression of results
Calculate the average diameter (D) with Formula (1):
DD+
D= (1)
2 © ISO 2021 – All rights reserved

where
D is the maximum diameter, expressed in millimetres (mm);
D is the minimum diameter, expressed in millimetres (mm);
D is the average diameter, expressed in millimetres (mm).
4.1.1.5 Test report
Report the average diameter to the nearest 0,001 mm.
4.1.2 Measure with profile projector
4.1.2.1 Principle
Specimens of a cord sample are successively put on the optical microscope. A silhouette of the cord is
projected on the screen. The thickness of the specimen is measured by moving the abscissa axis of the
projector.
4.1.2.2 Apparatus
4.1.2.2.1 Profile projector, with
— magnification possibility: × 10 or × 20;
— micrometre stage table: resolution 0,001 mm.
4.1.2.2.2 Sample holder, a frame on which two magnets are fixed in order to position the test
specimen.
4.1.2.2.3 Fusing machine
4.1.2.3 Procedure
a) Fuse a specimen to a length about 100 mm, ensure that fuse is securely tied in order to prevent the
cord ends from any unravelling. Put the specimen on the sample holder and ensure that is fixed by
magnets.
b) Bring the sample into sample holder and adjust the focal distance. Make the sample being projected
on the screen.
c) Rotate the sample until the maximum profile is being projected on the screen. Move the micrometre
table until the horizontal reference line contacts two consecutive waves (see Figure 3).
Figure 3 — X-axis contacts the two consecutive waves
d) Reset the micrometre. Move the stage until the X-axis contacts the opposite wave (see Figure 4).
Record the reading as maximum diameter (D . If there are two waves on the opposite side, measure
1)
the bigger one.
Figure 4 — X-axis contacts the other side wave
e) Turn the specimen through 90° until a minimum diameter is obtained, record the minimum
diameter D . Repeat the steps c) and d) and record the reading as minimum diameter (D ). If there
2 2
are two waves on the opposite side, measure the bigger one (see Figure 5).
Figure 5 — Minimum diameter
4.1.2.4 Expression of results
Calculate the average diameter (D) of the two readings with For
...