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International
Standard
ISO 3506-7
First edition
Fasteners — Mechanical properties
2024-07
of corrosion-resistant stainless steel
fasteners —
Part 7:
Flat washers with specified grades
and property classes
Fixations — Caractéristiques mécaniques des fixations en acier
inoxydable résistant à la corrosion —
Partie 7: Rondelles de forme plane de grades et classes de qualité
spécifiés
Reference number
© ISO 2024
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 2
5 Designation system for stainless steel grades and property classes of washers, and
combination with bolts, screws, studs and nuts . 3
5.1 General .3
5.2 Designation of stainless steel grades (first block) .4
5.3 Designation of property classes (second block) .4
5.4 Combination of washers with bolts, screws, studs and nuts.4
5.4.1 Stainless steel grade combination .4
5.4.2 Property class combination .4
6 Materials . 5
6.1 Chemical composition .5
6.2 Surface condition (finish and/or coating) .6
6.3 Corrosion resistance .7
6.4 Magnetic properties .7
7 Requirements for mechanical and physical properties . 7
8 Inspection . 7
8.1 Manufacturer’s inspection .7
8.2 Supplier’s inspection .8
8.3 Purchaser’s inspection .8
8.4 Delivery of test results .8
9 Hardness test . 8
9.1 General .8
9.2 Test procedure .8
9.3 Requirements .9
10 Marking and labelling . 9
10.1 General .9
10.2 Marking on the washers .9
10.2.1 General .9
10.2.2 Marking of the property class on the washers .10
10.2.3 Examples of marking on the washers .10
10.3 Marking of the packages (labelling) .11
Annex A (informative) Selection of standardized materials for stainless steel washers .12
Bibliography . 14
iii
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 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.
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 2, Fasteners.
A list of all parts in the ISO 3506 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.
iv
Introduction
This document is issued as an addition to the ISO 3506 series to provide a single point of reference for
flat stainless steel washers, in order to standardize market expectations for users, distributors and
manufacturers.
For mechanical properties of flat washers made of carbon steel and alloy steel, see ISO 898-3.
v
International Standard ISO 3506-7:2024(en)
Fasteners — Mechanical properties of corrosion-resistant
stainless steel fasteners —
Part 7:
Flat washers with specified grades and property classes
1 Scope
This document specifies the mechanical and physical properties of flat washers made of corrosion resistant
austenitic, ferritic and duplex stainless steels, designed to be used in bolted joints in combination with
bolts, screws, studs and nuts with specified grades and property classes in accordance with ISO 3506-1 and
ISO 3506-2.
These types of washers are also used with other stainless steel fasteners such as screws forming their own
mating thread (see e.g. ISO 3506-4).
ISO 3506-6 provides general rules and additional technical information on suitable stainless steels and their
properties (detailed properties of stainless steel grades, corrosion behaviour with regards to pitting, crevice
and intergranular corrosion, magnetic properties, etc.)
WARNING — Washers conforming to the requirements of this document are tested at the ambient
temperature range of 10 °C to 35 °C and are used in applications ranging from –20 °C to +150 °C. However,
these washers are also used outside this range down to –196 °C and up to +300 °C for specific applications.
It is possible that they do not retain the specified mechanical and physical properties at lower and/
or elevated temperatures. Therefore, it is the responsibility of the user to determine the appropriate
choices based on the service environment conditions of the assembly (see also Clauses 6 and 7).
This document applies to the following flat non-captive and captive washers with thickness 0,2 mm to 6 mm
(see 5.1):
— plain washers and flat washers (with or without knurls, ribs or chamfers),
— square washers,
— square hole washers,
— shaped plates.
The term “washer” is used in the following for all types of washers and plates within the scope of this
document.
This document does not specify requirements for functional properties such as weldability.
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 1891-4, Fasteners — Vocabulary — Part 4: Control, inspection, delivery, acceptance and quality
ISO 3506-1, Fasteners — Mechanical properties of corrosion-resistant stainless steel fasteners — Part 1: Bolts,
screws and studs with specified grades and property classes
ISO 3506-2, Fasteners — Mechanical properties of corrosion-resistant stainless steel fasteners — Part 2: Nuts
with specified grades and property classes
ISO 3506-6
...