ISO 683-6:2023

INTERNATIONAL ISO
STANDARD 683-6
Fourth edition
2023-11
Heat-treatable steels, alloy steels and
free-cutting steels —
Part 6:
Hot-rolled steels for quenched and
tempered springs
Aciers pour traitement thermique, aciers alliés et aciers pour
décolletage —
Partie 6: Aciers laminés à chaud pour ressorts trempés et revenus
Reference number
© ISO 2023
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ii
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Classification and designation . 2
4.1 Classification . 2
4.2 Designation . 2
5 Information to be supplied by the purchaser . 3
5.1 Mandatory information . 3
5.2 Supplementary or special requirements . 3
5.3 Ordering example. 3
6 Manufacturing process . 4
6.1 General . 4
6.2 Deoxidation. 4
6.3 Heat-treatment condition at delivery . 4
6.3.1 Normal delivery condition . 4
6.3.2 Particular heat treatment condition . 4
6.3.3 Particular surface condition . 4
6.4 Traceability of the cast . 4
7 Requirements . 4
7.1 General . 4
7.2 Chemical composition . 4
7.3 Mechanical properties . 5
7.4 Shearability . 5
7.5 Surface quality . 5
7.6 Grain size . 5
7.7 Non-metallic inclusions . 5
7.7.1 Microscopic inclusions . 5
7.7.2 Macroscopic inclusions . 6
7.8 Internal soundness . 6
7.9 Surface decarburization . 6
7.10 Spheroidization of carbides . . 6
7.11 Dimensions, tolerances and shape . 6
8 Inspection . 6
8.1 Testing procedures and type of documents . 6
8.2 Specific inspection . 7
8.2.1 Verification of the hardenability and hardness . 7
8.2.2 Summary of inspection and frequency of testing . 7
8.3 Sampling . 8
8.3.1 Selection and preparation of samples for the product analysis . 8
8.3.2 Sampling for the hardenability and hardness test . 8
9 Test methods . 9
9.1 Chemical analysis . 9
9.2 Hardness test and hardenability test . 9
9.2.1 Hardness in treatment conditions +A, +S or +AC . 9
9.2.2 Verification of hardenability . 9
9.3 Retest . 9
10 Marking . . 9
Annex A (normative) Supplementary or special requirements .23
iii
Annex B (informative) Maximum dimensions for flats and rounds based on the 100 %
hardenability scatterband .25
Annex C (informative) Guidance values for the mechanical properties of quenched and
tempered test pieces .26
Annex D (informative) Designation of steels given in this document and of comparable
grades covered in various designation systems .27
Bibliography .28
iv
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
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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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO 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, ISO had not received
notice of (a) patent(s) 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 www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
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constitute an endorsement.
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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 4, Heat
treatable and alloy steels.
This fourth edition cancels and replaces the third edition (ISO 683-14:2004), which has been technically
revised.
The main changes are as follows:
— partial structure revision;
— editorial revision.
A list of all parts in the ISO 683 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.
v
INTERNATIONAL STANDARD ISO 683-6:2023(E)
Heat-treatable steels, alloy steels and free-cutting steels —
Part 6:
Hot-rolled steels for quenched and tempered springs
1 Scope
This document specifies the technical delivery requirements for round and flat bars and wire rods
manufactured from the alloyed steels listed in Table 4, intended for hot-formed and subsequently heat-
treated springs or cold-formed and subsequently heat-treated springs. The products are supplied in
one of the heat-treatment conditions given for the different types of products in Table 2 and in one of
the surface conditions given in Table 3.
NOTE 1 Table 4 only considers steels that have gained certain international importance. This does, however,
not mean that these are available in all industrial countries. In addition, a great number of other steels are
specified in regional and national standards.
NOTE 2 Non-alloy steels also for the production of springs are covered by the wire rod specification in
ISO 16120-4.
NOTE 3 International Standards relating to steels conforming with the chemical composition requirements in
Table 4, but supplied in other product forms or other treatment conditions or intended for special applications,
are given in the bibliography.
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 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 642, Steel — Hardenability test by end quenching (Jominy test)
ISO 643, Steels — Micrographic determination of the apparent grain size
ISO 3887, Steels — Determination of the depth of decarburization
ISO 4885, Ferrous materials — Heat treatments — Vocabulary
ISO 4948-1, Steels — Classification — Part 1: Classification of steels into unalloyed and alloy steels based
on chemical composition
ISO 4948-2, Steels — Classification — Part 2: Classification of unalloyed and alloy steels according to main
quality classes and main property or application characteristics
ISO 4967, Steel — Determination of content of non-metallic inclusions — Micrographic method using
standard diagrams
ISO 6506-1, Metallic materials — Brinell hardness test — Part 1: Test method
ISO 6508-1, Metallic materials — Rockwell hardness test — Part 1: Test method
ISO 6929, Steel products — Vocabulary
ISO 9443, Surface quality classes for hot-rolled bars and wire rod
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 23825, Method for evaluating the nodularity of spheroidal carbides — Steels for cold heading and cold
extruding
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 377, ISO 643, ISO 3887,
ISO 9443, ISO 4885, ISO 4948-1, ISO 4948-2, ISO 6929 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
hot-rolled steels for quenched and tempered springs
steels which are, because of their resilience in the quenched and tempered condition, particularly
suitable for the manufacture of spring-like components of all kinds
Note 1 to entry: The resilience of the steel depends on their elastic deformability, which enables them to sustain
loading within a given range without exhibiting any permanent deformation when the load is removed. The
properties required of the steels for springs are obtained by increasing carbon contents and alloying constituents
such as silicon, manganese, chromium, molybdenum and vanadium, and also by heat-treatment, i.e. hardening in
oil with subsequent tempering.
3.2
alloy steel
as defined in ISO 4948-1
4 Classification and designation
4.1 Classification
The classification of the relevant steel grades is in accordance with ISO 4948-1 and ISO 4948-2. All steel
grades covered by this document are alloy special steels.
4.2 Designation
For the steel grades covered by this document, the steel names given in the relevant tables are allocated
in accordance with ISO/TS 4949.
NOTE Designation of steels covered by this document and of comparable grades covered in various other
designation systems are given in Annex D.
5 Information to be supplied by the purchaser
5.1 Mandatory information
The following information shall be supplied by the purchaser at the time of enquiry and order:
a) quantity to be delivered;
b) designation of the product form (round bar, flat bar, wire rod, etc.);
c) either the designation of the dimensional standard and the dimensions and tolerances selected
from it (see 7.11) or the designation of the drawing or any other document covering the dimensions
and tolerances required for the product;
d) a reference to this document, i.e. ISO 683-6:2023;
e) the designation of the steel type given in Table 4 and, where appropriate, the symbols for the core
hardness grade (see 7.3 and Table 7) or the restricted hardenability grade (see 7.3 and Table 9);
f) standard designation for a test report 2.2 or, if required, any other type of inspection document in
accordance with ISO 10474 or another equivalent standard, e.g. EN 10204 or JIS G 0415.
5.2 Supplementary or special requirements
A number of options are specified in this document and listed below.
a) if a heat-treatment condition other than the untreated condition is required, see the symbol for this
other condition (see Table 2, column 2);
b) if a surface condition other than “hot-worked” or a special surface quality is required, see the
surface condition (see Table 3) and the surface quality (see 7.5);
c) product analysis (see 7.2, 8.2.2 and 9.1);
d) any requirement concerning the verification of fine grain steel, see 7.6 and A.2;
e) any requirement for the verification of the non-metallic inclusions, see 7.7.1;
f) any requirements for non-destructive testing, see 7.8 and A.3;
g) any requirements for testing the depth of decarburization, see 7.9 and A.4;
h) any requirement for the verification of the carbide spheroidization, see 7.10 and A.5;
i) any requirements concerning special or additional marking, see Clause 10 and A.6.
5.3 Ordering example
EXAMPLE 50 t hot-rolled round bars according to ISO 1035-1 with a nominal diameter of 20,0 mm and
a nominal length of 8 000 mm with a diameter tolerance of ±0,25 mm (= class S of ISO 1035-4) and a length
tolerance of 0 mm to 100 mm (= class L2 of ISO 1035-4) and all other tolerances as given in ISO 1035-4 for normal
cases, made of steel grade ISO 683-6, 51CrV4 in the heat-treatment condition soft annealed (symbol +A), surface
blast cleaned (symbol +BC); with an inspection certificate 3.1 (see ISO 10474).
50 t round bars ISO 1035 – 20,0S × 8 000L2
ISO 683-6 – 51CrV4+A+BC
ISO 10474 – 3.1
6 Manufacturing process
6.1 General
The manufacturing process for the steel and for the products is, with the restrictions given by the
requirements in 6.2 to 6.4, left to the discretion of the manufacturer.
6.2 Deoxidation
All steels shall be fully killed.
6.3 Heat-treatment condition at delivery
6.3.1 Normal delivery condition
Unless otherwise agreed at the time of enquiry and order, the products shall be delivered in the
untreated condition, i.e. as hot-worked.
6.3.2 Particular heat treatment condition
If so agreed at the time of enquiry and order, the products shall be delivered in one of the heat-treatment
conditions given in Table 2, lines 3 to 6.
6.3.3 Particular surface condition
If so agreed at the time of enquiry and order, the products shall be delivered in one of the particular
surface conditions given in Table 3, lines 3 to 6.
6.4 Traceability of the cast
The steels shall be delivered separated by casts.
7 Requirements
7.1 General
Table 2 gives a survey of combinations of usual heat-treatment conditions at delivery, product forms
and requirements in accordance with Tables 4 to 9 (chemical composition, maximum dimensions for a
minimum core hardness, maximum hardness, hardenability).
In special cases, variations in these technical delivery requirements or additions to them may form the
subject of an agreement at the time of enquiry and order (see Annex A).
In addition to the special delivery condition of this document, the general technical delivery
requirements of ISO 404 shall apply.
7.2 Chemical composition
The chemical composition determined by cast analysis shall conform with the values in Table 4.
Permissible deviations between the limiting values for cast analysis and the values for product analysis
are given in Table 5.
If specified at the time of the enquiry and order, the product analysis shall be carried out.
7.3 Mechanical properties
Where the steel is not ordered according to core hardness or restricted hardenability requirements,
i. e. where the steel type designations of Table 6 or Table 8 and not the designations given in Table 7
or Table 9 apply, the requirements for chemical composition, hardenability and maximum hardness
cited in Table 2, (column 5) shall apply as appropriate, for the particular heat-treatment condition (see
footnote b to Table 4).
Where the steel is, by using the designations given in Table 9, ordered in accordance with restricted
hardenability requirements, the values of restricted hardenability given in Table 9 shall apply, in
addition to the requirements cited in Table 2, columns 5 (1) and 5 (2).
NOTE 1 The values in Table 8 and Table 9 for normal and restricted hardenability requirements are visualized
in Figure 1.
Where the steel is, by using the designations given in Table 7, ordered in accordance with core
hardness requirements, the values of core hardenability given in Table 7 shall apply, in addition
to the requirements cited in Table 2, columns 5 (1) and 5 (2). In this case, the values of end-quench
hardenability given in Table 8 are for guidance purposes only.
NOTE 2 The maximum dimensions given in Table 7 correspond to the restricted hardenability scatterband in
accordance with Table 9. For smaller sizes (see Table B.1) the normal hardenability scatterband in accordance
with Table 8 might be sufficient.
NOTE 3 For the grades 38Si7+CH and 46Si7+CH, maximum dimensions for the minimum core hardness after
quenching cannot be delivered.
7.4 Shearability
Under suitable shearing conditions (avoiding local stress peaks, preheating, application of blades with a
profile adapted to that of the product, etc.) all steels are normally shearable not only in the condition +S
but also in condition +A (see Table 2).
7.5 Surface quality
All products shall have a workmanlike finish.
Bars and wire rod shall be delivered with surface class A in accordance with ISO 9443, unless otherwise
agreed at the time of enquiry and order. For flat bars, the details of verification shall be agreed upon at
the time of enquiry and order.
Removal of surface discontinuities by welding is not permitted.
If surface discontinuities are removed by other methods, the kind and permissible depth for removal
of surface discontinuities should, where appropriate, be agreed upon at the time of enquiry and order.
7.6 Grain size
The steel shall show an austenitic grain size of 6 or finer. For the verification of the fine grain size, see
A.2.
7.7 Non-metallic inclusions
7.7.1 Microscopic inclusions
The steels shall have a certain degree of cleanness. However, verification of the non-metallic inclusion
content requires a special agreement. If there is such an agreement at the time of enquiry and order,
the microscopic non-metallic inclusion content shall be determined to an agreed procedure and within
agreed limits in accordance with ISO 4967 or another equivalent standard.
For grades with specified minimum sulfur content, the agreement should not include sulfides.
7.7.2 Macroscopic inclusions
This requirement is applicable to the verification of the macroscopic inclusions in special steels. If
verification is agreed, the method and acceptance limits shall be agreed at the time of enquiry and
order.
7.8 Internal soundness
The steel shall be free from internal defects likely to have an adverse effect. If verification is agreed, the
method and acceptance limits shall be agreed at the time of enquiry and order, see A.3.
7.9 Surface decarburization
Bars and wire rod with as-rolled surface of steel in the untreated condition (+U), in the treated to
improve shearability condition (+S), in the soft annealed condition (+A) and in the annealed to achieve
spheroidization of the carbides condition (+AC) shall be free from complete decarburization.
The values for the admissible partial surface decarburization given in Table 10 apply for the untreated
condition (+U), for the treated to improve shearability condition (+S), for the soft annealed condition
(+A) and for the annealed to achieve spheroidization of the carbides condition
...