SIST EN ISO 6931-1:2020

SLOVENSKI STANDARD
oSIST prEN ISO 6931-1:2020
01-junij-2020
Nerjavno jeklo za vzmeti - 1. del: Žica (ISO 6931-1:2016)
Stainless steels for springs - Part 1: Wire (ISO 6931-1:2016)
Nichtrostende Stähle für Federn - Teil 1: Draht (ISO 6931-1:2016)
Aciers inoxydables pour ressorts - Partie 1: Fils (ISO 6931-1:2016)
Ta slovenski standard je istoveten z: prEN ISO 6931-1
ICS:
77.140.25 Vzmetna jekla Spring steels
77.140.65 Jeklene žice, jeklene vrvi in Steel wire, wire ropes and
verige link chains
oSIST prEN ISO 6931-1:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 6931-1:2020

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oSIST prEN ISO 6931-1:2020
INTERNATIONAL ISO
STANDARD 6931-1
Third edition
2016-05-15
Stainless steels for springs —
Part 1:
Wire
Aciers inoxydables pour ressorts —
Partie 1: Fils
Reference number
ISO 6931-1:2016(E)
©
ISO 2016

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oSIST prEN ISO 6931-1:2020
ISO 6931-1:2016(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved

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oSIST prEN ISO 6931-1:2020
ISO 6931-1:2016(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Information to be supplied by the purchaser. 2
4 Requirements . 2
4.1 Manufacturing process. 2
4.2 Form of delivery . 2
4.3 Surface finish . 2
4.4 Chemical composition . 2
4.5 Mechanical properties . 3
4.6 Technological properties . 6
4.6.1 Coiling test . 6
4.6.2 Wrapping test . 6
4.6.3 Simple bend test . 6
4.7 Supply conditions of wire on coils/reels and spools . 6
4.7.1 General. 6
4.7.2 Coil size . 6
4.7.3 Circular wire cast . 7
4.7.4 Helix cast of wire . 7
4.8 Surface quality . 8
4.9 Inner soundness . 8
4.10 Dimensions and dimensional tolerances . 8
4.10.1 Tolerances on diameter . . 8
4.10.2 Out of roundness . . 9
4.10.3 Tolerance on the length of straightened and cut lengths . 9
5 Testing and inspection . 9
5.1 Inspection and inspection documents . 9
5.2 Extent of testing for specific testing .10
5.3 Sampling .12
5.4 Test methods .12
5.4.1 Chemical composition .12
5.4.2 Tensile test .12
5.4.3 Coiling test .12
5.4.4 Wrapping test .12
5.4.5 Simple bend test .12
5.4.6 Reverse torsion test .12
5.4.7 Wire cast .13
5.5 Retests .13
6 Marking and packaging .13
Annex A (informative) Additional information .14
Bibliography .19
© ISO 2016 – All rights reserved iii

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oSIST prEN ISO 6931-1:2020
ISO 6931-1:2016(E)

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 on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 17, Steel, Subcommittee SC 4, Heat treatable and
alloy steels.
This third edition cancels and replaces the second edition (ISO 6931-1:1994), which has been technically
revised.
ISO 6931 consists of the following parts, under the general title Stainless steels for springs:
— Part 1: Wire
— Part 2: Narrow strip
iv © ISO 2016 – All rights reserved

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oSIST prEN ISO 6931-1:2020
INTERNATIONAL STANDARD ISO 6931-1:2016(E)
Stainless steels for springs —
Part 1:
Wire
1 Scope
This part of ISO 6931 specifies the grades of stainless steels which are generally used in the cold drawn
condition in the form of wire of circular cross-section up to 10,00 mm in diameter, for the production of
springs and spring parts exposed to corrosive effects and sometimes to slightly increased temperatures
(see Annex A).
Certain steel grades covered by ISO 16143-2 are also used for springs, although to a much lesser extent.
In these cases, the mechanical properties (tensile strength, etc.) will be agreed between purchaser
and supplier. Similarly, diameters between 10,00 mm and 15,00 mm can be ordered according to the
specifications of this part of ISO 6931, in which case the parties will agree upon the required mechanical
characteristics.
In addition to the specifications of this part of ISO 6931, the general technical delivery requirements of
ISO 404 are applicable.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 377, Steel and steel products — Location and preparation of samples and test pieces for mechanical testing
ISO 404, Steel and steel products — General technical delivery requirements
ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
ISO 10474, Steel and steel products — Inspection documents
ISO 14284, Steel and iron — Sampling and preparation of samples for the determination of chemical
composition
ISO 15510, Stainless steels — Chemical composition
ISO 16143-2, Stainless steels for general purposes — Part 2: Corrosion-resistant semi-finished products,
bars, rods and sections
ISO 22034-1, Steel wire and wire products — Part 1: General test methods
ISO 22034-2, Steel wire and wire products — Part 2: Tolerances on wire dimensions
ISO/TS 4949, Steel names based on letter symbols
ISO/TR 9769, Steel and iron — Review of available methods of analysis
© ISO 2016 – All rights reserved 1

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oSIST prEN ISO 6931-1:2020
ISO 6931-1:2016(E)

3 Information to be supplied by the purchaser
The purchaser shall clearly state in his enquiry or order the product and following information:
a) the desired quantity;
b) the term spring steel wire or straightened and cut lengths;
c) the number of this part of ISO 6931: ISO 6931-1;
d) the steel grade (see Table 1) and for grade 4301-304-00-I, 4310-301-00-I and 4462-318-03-I also
the tensile strength level (see Table 2);
e) the nominal wire diameter and the class for the diameter tolerance (see Table 5) and additional for
cut length the length and the length tolerance class (see Table 6);
f) the surface finish (see 4.3, i.e. coating);
g) the form of delivery (see 4.2);
h) the type of inspection document to be supplied (see 5.1);
i) any particular agreement made.
EXAMPLE 2 t stainless steel spring wire according to this part of ISO 6931, grade 4310-301-00-I, normal
tensile strength level and nominal diameter 2,50 mm, diameter tolerance class T15, in coils with inspection
document 3.1 according to ISO 10474:
     2 t spring steel wire ISO 6931-1 – 4310-301-00-I – NS – 2,50 T15 – in coils, ISO 10474 – 3.1
4 Requirements
4.1 Manufacturing process
Unless otherwise agreed in the order, the manufacturing process used in the making of the stainless
steel wire is left to the discretion of the manufacturer. The starting condition (+AT: solution annealed)
of the wire (rod) is specified in ISO 16143-2.
4.2 Form of delivery
The wire shall be supplied in coils, on spools, on coreless spools or on carriers. Several coils may be
assembled on a carrier. Unless otherwise specified, the form of delivery shall be at the manufacturer’s
discretion. They shall, however, inform the purchaser about the form of delivery.
The delivery requirements are specified in 4.7. Wire in straight lengths is normally supplied in bundles.
4.3 Surface finish
The wire may be coated or not. The specific coating and finish for stainless steel spring wire shall be
agreed upon at the time of enquiry and order, e. g. uncoated, polished finish, nickel coated.
4.4 Chemical composition
4.4.1 The requirements for the chemical composition given in Table 1 apply to the cast analysis.
4.4.2 The permissible deviation of the product analysis from the values specified in Table 1 shall
be in accordance with the provision in ISO 16143-2. For a single heat, the deviation of an element in
the product analysis may be only below the minimum or only above the maximum value of the range
specified for the heat analysis but not both at the same time.
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oSIST prEN ISO 6931-1:2020
ISO 6931-1:2016(E)

Table 1 — Chemical composition (cast analysis)
a, b
Steel grade % by mass
c c
Name Number C Si Mn P S Cr Mo Ni Other elements
Austenitic steels
0,05
f
X10CrNi18-8 4310-301-00-I 2,00 2,00 0,045 0,015 16,0 to 19,0 0,80 6,0 to 9,5 N: 0,10
to 0,15
0,030 to 8,0 to
X9CrNi18-9 4325-302-00-E 1,00 2,00 0,045 0,030 17,0 to 19,0 - N: 0,10
0,15 10,0
N: 0,10 to 0,30
7,0 to
X5CrNiN19-9 4315-304-51-I 0,08 1,00 2,50 0,045 0,030 18,0 to 20,0 -
10,5
Nb: 0,15
8,0 to
f
X5CrNi18-10 4301-304-00-I 0,07 1,00 2,00 0,045 0,015 17,5 to 19,5 - N: 0,10
10,5
2,00 to 10,0 to
d d f
X5CrNiMo17-12-2 4401-316-00-I 0,07 1,00 2,00 0,045 0,015 16,5 to 18,5 N: 0,10
3,0 13,0
4,0 to 23,5 to N: 0,15
X1NiCrMoCu25-20-5 4539-089-04-I 0,020 0,75 2,00 0,035 0,015 19,0 to 22,0
5,0 26,0 Cu: 1,20 to 2,00
Austenitic-ferritic (duplex) steel
2, 50 to
X2CrNiMoN22-5-3 4462-318-03-I 0,030 1,00 2,00 0,035 0,015 21,0 to 23,0 4,5 to 6,5 N: 0,10 to 0,22
3,5
Precipitation hardening steel
7,0 to
X7CrNiAl17-7 4568-177-00-I 0,09 0,70 1,00 0,040 0,015 16,0 to 18,0 - Al: 0,70 to 1,50
e
8,5
a
  Maximum values unless indicated otherwise.
b
  Alternative compositions may be used by agreement.
c
  “Name” and “Number” are derived in accordance with ISO/TS 4949 and ISO 15510, respectively.
d
  Steel 4436-316-00-I may be used to provide increased corrosion resistance compared with 4401-316-00-I, with the specification of this part of
ISO 6931-1 applicable for steel 4401-316-00-I.
e
  In ISO 15510 and ISO 16143, this steel grade is given with 6,5 % to 7,8 % Ni; for spring application, these values are raised to the values in the table.
f
  These steels are given in ISO 15510 and ISO 16143 with S max. 0,030; for spring application, this value is diminished to the value in the table.
4.5 Mechanical properties
4.5.1 For the tensile strength in the as drawn condition, the data of Table 2 shall apply.
© ISO 2016 – All rights reserved 3

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oSIST prEN ISO 6931-1:2020
ISO 6931-1:2016(E)

4 © ISO 2016 – All rights reserved
Table 2 — Tensile strength in the as drawn condition
a b c d e f
Tensile strength (MPa)  for the following steel grades
g
4310-301-00-I 4325-302-00-E 4301-304-00-I 4401-316-00-I 4539-089-04-I 4462-318-03-I 4568-177-00-I
4315-304-51-I
Nominal Normal High tensile Normal High Normal tensile High tensile
diameter tensile strength tensile tensile strength strength
strength strength strength
f
mm (HS) (NS) - (HS) -
(NS) (NS) (HS)
min.
min. max. min. max. min. max. min. max.
min. max. min. max. min. max. min. max. min. max.
d ≤ 0,20 2 200 2 530 2 350 2 710 2 150 2 400 2 000 2 150 2 300 1 725 1 990 1 600 1 840 2 150 2 480 2 370 2 730 1 975 2 280
0,20 < d ≤ 0,30 2 150 2 480 2 300 2 650 2 050 2 300 1 975 2 050 2 280 1 700 1 960 1 550 1 790 2 100 2 420 2 370 2 730 1 950 2 250
0,30 < d ≤ 0,40 2 100 2 420 2 250 2 590 2 050 2 300 1 925 2 050 2 220 1 675 1 930 1 550 1 790 2 000 2 300 2 370 2 730 1 925 2 220
0,40 < d ≤ 0,50 2 050 2 360 2 200 2 530 1 950 2 200 1 900 1 950 2 190 1 650 1 900 1 500 1 750 2 000 2 300 2 370 2 730 1 900 2 190
0,50 < d ≤ 0,65 2 000 2 300 2 150 2 480 1 900 2 150 1 850 1 950 2 130 1 625 1 870 1 450 1 670 1 900 2 190 2 370 2 730 1 850 2 130
0,65 < d ≤ 0,80 1 950 2 250 2 100 2 420 1 850 2 100 1 800 1 850 2 070 1 600 1 840 1 450 1 670 1 900 2 190 2 230 2 570 1 825 2 100
0,80 < d ≤ 1,00 1 900 2 190 2 050 2 360 1 850 2 100 1 775 1 850 2 050 1 575 1 820 1 400 1 610 1 800 2 070 2 140 2 470 1 800 2 070
1,00 < d ≤ 1,25 1 850 2 130 2 000 2 300 1 750 2 000 1 725 1 750 1 990 1 550 1 790 1 350 1 560 1 800 2 070 2 090 2 410 1 750 2 020
1,25 < d ≤ 1,50 1 800 2 070 1 950 2 250 1 700 1 950 1 675 1 750 1 930 1 500 1 730 1 350 1 560 1 700 1 960 2 090 2 410 1 700 1 960
1,50 < d ≤ 1,75 1 750 2 020 1 900 2 190 1 650 1 900 1 625 1 650 1 870 1 450 1 670 1 300 1 500 1 700 1 960 2 000 2 300 1 650 1 900
1,75 < d ≤ 2,00 1 700 1 960 1 850 2 130 1 650 1 900 1 575 1 650 1 820 1 400 1 610 1 300 1 500 1 700 1 960 2 000 2 300 1 600 1 840
2,00 < d ≤ 2,50 1 650 1 900 1 750 2 020 1 550 1 800 1 525 1 550 1 760 1 350 1 560 1 300 1 500 1 550 1 790 1 900 2 190 1 550 1 790
2,50 < d ≤ 3,00 1 600 1 840 1 700 1 960 1 450 1 700 1 475 1 550 1 700 1 300 1 500 1 300 1 500 1 550 1 790 1 860 2 140 1 500 1 730
3,00 < d ≤ 3,50 1 550 1 790 1 650 1 900 1 450 1 700 1 425 1 450 1 640 1 250 1 440 1 300 1 500 1 550 1 790 1 850 2 050 1 450 1 670
3,50 < d ≤ 4,25 1 500 1 730 1 600 1 840 1450 1 700 1 400 1 450 1 610 1 225 1 410 1 250 1 440 1 450 1 670 1 750 1 950 1 400 1 610
4,25 < d ≤ 5,00 1 450 1 670 1 550 1 790 1 350 1 600 1 350 1 350 1 560 1 200 1 380 1 250 1 440 1 450 1 670 1 700 1 900 1 350 1 560
Grade 4310-301-00-I and 4462-318-03-I can be delivered in normal tensile strength (NS) or high tensile strength (HS).
For steel 4568-177-00-I, the characteristics of the springs are not only determined by the characteristics of the drawn wire but also by the heat-treatment of the spring (see A.2). Therefore, the steel should be of a quality such
that by the heat treatment after drawing the mechanical properties are met.
a
  Tensile strength calculated on actual diameter.
b
  The range of tensile strength values within a production batch of the same heat shall be a maximum of 9 % of the minimum values in this table.
c
  After straightening, it is recognized that the tensile strength may reduce by up to 10 % but the minimum values of this table have to be fulfilled.
d
  When better formability is required, lower tensile strength values may be agreed upon.
e
  The wire is supplied in the cold drawn condition. The tensile strength in the finished spring may be substantially influenced by a heat treatment; particularly, precipitation hardening of grade 4568-177-00-I results in
substantially higher tensile strength (see A.5.2 and Table A.3).
f
  Larger diameters may be specified in which case the parties shall agree the tensile strength at the time of enquiry and order.
g
When the tensile test of 4568-177-00-I is performed on test piece after precipitation hardening heat treatment (air cooling after heating at 470 ± 20 °C for up to 1 h) as agreed upon between the purchaser and supplier, the
increment in tensile strength shall be 250 MPa or over. This requirement applies for nominal diameters ≤6,0 mm.

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oSIST prEN ISO 6931-1:2020
ISO 6931-1:2016(E)

© ISO 2016 – All rights reserved 5
Table 2 (continued)
a b c d e f
Tensile strength (MPa)  for the following steel grades
g
4310-301-00-I 4325-302-00-E 4301-304-00-I 4401-316-00-I 4539-089-04-I 4462-318-03-I 4568-177-00-I
4315-304-51-I
Nominal Normal High tensile Normal High Normal tensile High tensile
diameter tensile strength tensile tensile strength strength
strength strength strength
f
mm (HS) (NS) - (HS) -
(NS) (NS) (HS)
min.
min. max. min. max. min. max. min. max. min. max. min. max. min. max. min. max. min. max.
5,00 < d ≤ 6,00 1 400 1 610 1 500 1 730 1 350 1 600 1 300 1 350 1 500 1 150 1 330 1 250 1 440 1 350 1 560 – – 1 300 1 500
6,00 < d ≤ 7,00 1 350 1 560 1 450 1 670 1 270 1 520 1 250 1 300 1 440 1 125 1 300 1 200 1 380 1 350 1 560 – – 1 250 1 440
7,00 < d ≤ 8,50 1 300 1 500 1 400 1 610 1 130 1 380 1 200 1 300 1 380 1 075 1 240 1 150 1 330 – – – – 1 250 1 440
8,50 < d ≤ 10,00 1 250 1 440 1 350 1 560 980 1 230 1 175 1 250 1 360 1 050 1 210 – – – – – – 1 250 1 440
Grade 4310-301-00-I and 4462-318-03-I can be delivered in normal tensile strength (NS) or high tensile strength (HS).
For steel 4568-177-00-I, the characteristics of the springs are not only determined by the characteristics of the drawn wire but also by the heat-treatment of the spring (see A.2). Therefore, the steel should be of a quality such
that by the heat treatment after drawing the mechanical properties are met.
a
  Tensile strength calculated on actual diameter.
b
  The range of tensile strength values within a production batch of the same heat shall be a maximum of 9 % of the minimum values in this table.
c
  After straightening, it is recognized that the tensile strength may reduce by up to 10 % but the minimum values of this table have to be fulfilled.
d
  When better formability is required, lower tensile strength values may be agreed upon.
e
  The wire is supplied in the cold drawn condition. The tensile strength in the finished spring may be substantially influenced by a heat treatment; particularly, precipitation hardening of grade 4568-177-00-I results in
substantially higher tensile strength (see A.5.2 and Table A.3).
f
  Larger diameters may be specified in which case the parties shall agree the tensile strength at the time of enquiry and order.
g
When the tensile test of 4568-177-00-I is performed on test piece after precipitation hardening heat treatment (air cooling after heating at 470 ± 20 °C for up to 1 h) as agreed upon between the purchaser and supplier, the
increment in tensile strength shall be 250 MPa or over. This requirement applies for nominal diameters ≤6,0 mm.

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oSIST prEN ISO 6931-1:2020
ISO 6931-1:2016(E)

4.5.2 In addition to the requirements of Table 2, the maximum tensile strength range within one unit
package (individual coil, spool or reel, etc.) shall satisfy Table 3.
For straightened and cut lengths, the values of Table 3 apply for the individual bundles.
Table 3 — Tensile strength range within an individual unit package (coil/spool/bundle)
Wire diameter, d Max. range
mm MPa
d ≤ 1,50 100
1,50 < d ≤ 10,00 70
4.6 Technological properties
4.6.1 Coiling test
For evaluation of uniformity of coiling and surface condition, the coiling test may be applied to wire
with a diameter of 0,50 mm to 1,50 mm. The spring coiled in accordance with 5.4.3 shall show a defect
free surface condition without splits or fracture; the coil shall have uniform pitch of the turns and a fair
dimensional regularity of its diameter.
Although the usefulness of the coiling test is not generally recognized, it has been retained since it
offers the possibility of revealing internal stresses. If doubtful test results are obtained, the wire
concerned should not be rejected immediately but efforts should be made by the parties concerned to
elucidate the cause.
4.6.2 Wrapping test
The wrapping test may be applied to wire with a diameter of 0,30 mm to 3,00 mm. The wire shall not
show any sign of cracks or surface imperfections when closely wrapped eight turns around a mandrel
of a diameter equal to the wire size (see also 5.4.4).
4.6.3 Simple bend test
Where requested, the bend test may be applied for wire with a diameter over 3,00 mm. The wire shall
withstand the test without any sign of failure (see also 5.4.5).
NOTE In some applications, the material is severely deformed by bending. Such is the case for extension
springs with tight hooks, springs with bends on legs, spring wire forms, etc. In such cases, the bend test provides
for a wire test very close to actual use.
4.7 Supply conditions of wire on coils/reels and spools
4.7.1 General
The wire of each coil shall consist of one single length of wire originating from only one heat. It shall be
wound so that there are no kinks.
Where wire is delivered on spools, spoolless cores or carriers up to 10 % of delivery number may
consist of a maximum of two wire lengths. Joints on end product diameter shall be suitably marked and
labelled, unless otherwise agreed.
4.7.2 Coil size
The internal diameter of unit packages (coil/reels or spools) shall reach at least the values given in
Table 4, unless otherwise agreed.
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oSIST prEN ISO 6931-1:2020
ISO 6931-1:2016(E)

Table 4 — Wire diameter and associated minimum coil internal diameter
Wire diameter, d Minimum internal diameter
mm mm
d ≤ 0,18 To be agreed at the time of
enquiry and order
0,18 < d ≤ 0,28 100
0,28 < d ≤ 0,50 150
0,50 < d ≤ 0,70 180
0,70 < d ≤ 1,60 250
1,60 < d ≤ 4,50 400
4,50 < d 500
4.7.3 Circular wire cast
The wire shall be uniformly cast and take a circular cast. Unless otherwise specified, the wap diameter
of the wire supplied in coils/reels may expand when the binding wires are removed but should usually
not retract to less than the unit internal diameter, other than by agreement between supplier and
purchaser. The expansion shall be approximately even within a single unit package and within all the
units in a production batch.
4.7.4 Helix cast of wire
The wire shall be dead cast, free from helix cast. The requirement shall be considered fulfilled in the
case of wire below 5,00 mm if the follo
...