SIST EN ISO 3506-7:2026

SLOVENSKI STANDARD
01-januar-2026
Vezni elementi - Mehanske lastnosti korozijsko odpornih nerjavnih jekel - 7. del:
Ploščate podložke z določenimi razredi in razredi trdnosti (ISO 3506-7:2024)
Fasteners - Mechanical properties of corrosion-resistant stainless steel fasteners - Part
7: Flat washers with specified grades and property classes (ISO 3506-7:2024)
Mechanische Verbindungselemente - Mechanische Eigenschaften von
Verbindungselementen aus korrosionsbeständigen nichtrostenden Stählen - Teil 7:
Flache Scheiben mit festgelegten Stahlsorten und Festigkeitsklassen (ISO 3506-7:2024)
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
(ISO 3506-7:2024)
Ta slovenski standard je istoveten z: EN ISO 3506-7:2025
ICS:
21.060.30 Podložke, varovalni elementi Washers, locking elements
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 3506-7
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2025
EUROPÄISCHE NORM
ICS 21.060.30
English Version
Fasteners - Mechanical properties of corrosion-resistant
stainless steel fasteners - Part 7: Flat washers with
specified grades and property classes (ISO 3506-7:2024)
Fixations - Caractéristiques mécaniques des fixations Mechanische Verbindungselemente - Mechanische
en acier inoxydable résistant à la corrosion - Partie 7: Eigenschaften von Verbindungselementen aus
Rondelles de forme plane de grades et classes de korrosionsbeständigen nichtrostenden Stählen - Teil 7:
qualité spécifiés (ISO 3506-7:2024) Flache Scheiben mit festgelegten Stahlsorten und
Festigkeitsklassen (ISO 3506-7:2024)
This European Standard was approved by CEN on 24 November 2025.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 3506-7:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
The text of ISO 3506-7:2024 has been prepared by Technical Committee ISO/TC 2 "Fasteners” of the
International Organization for Standardization (ISO) and has been taken over as EN ISO 3506-7:2025 by
Technical Committee CEN/TC 185 “Fasteners” the secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by May 2026, and conflicting national standards shall be
withdrawn at the latest by May 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 3506-7:2024 has been approved by CEN as EN ISO 3506-7:2025 without any
modification.
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 3506-7:2024(en) © ISO 2024

ISO 3506-7:2024(en)
© ISO 2024
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 below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 3506-7:2024(en)
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
ISO 3506-7:2024(en)
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
ISO 3506-7:2024(en)
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 3506-7:2024(en)
ISO 3506-2, Fasteners — Mechanical properties of corrosion-resistant stainless steel fasteners — Part 2: Nuts
with specified grades and property classes
ISO 3506-6, Fasteners — Mechanical properties of corrosion-resistant stainless steel fasteners — Part 6: General
rules for the selection of stainless steels and nickel alloys for fasteners
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 16228, Fasteners - Types of inspection documents
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
stainless steel
steel with at least 10,5 % (mass fraction) of chromium (Cr) and maximum 1,2 % (mass fraction) of carbon (C)
[SOURCE: ISO 3506-1:2020, 3.5]
3.2
austenitic stainless steel
stainless steel (3.1) with high amounts of chromium and nickel, which usually cannot be hardened by heat
treatment, providing excellent resistance to corrosion, good ductility, and usually low or non-magnetic
properties.
[SOURCE: ISO 3506-1:2020, 3.6]
3.3
ferritic stainless steel
stainless steel (3.1) containing less than 0,1 % carbon and typically 11 % to 18 % chromium, which usually
cannot be hardened by heat treatment, and with highly magnetic properties.
[SOURCE: ISO 3506-1:2020, 3.8]
3.4
duplex stainless steel
stainless steel (3.1) with a micro-structure that includes both austenitic and ferritic phases, providing
excellent resistance to corrosion, containing a higher amount of chromium and a reduced quantity of nickel
compared to austenitic steel, with high strength, and with magnetic properties.
[SOURCE: ISO 3506-1:2020, 3.9]
4 Symbols
F test force for Vickers hardness determination, N
t nominal thickness of washer, mm
nom
t effective thickness of the material measured on the washer, mm
eff
ISO 3506-7:2024(en)
5 Designation system for stainless steel grades and property classes of washers, and
combination with bolts, screws, studs and nuts
5.1 General
The designation system for stainless steel washers consists of two blocks, separated by a hyphen: the
stainless steel grade and the property class, as specified in Figure 1.
The standard combinations in Figure 1 shall be considered together with Table 1, which shows thickness
limits for each combination.
This designation system may be used for sizes outside the limits specified in this document, provided that
all applicable chemical, mechanical and physical requirements are met. For non-standard fasteners, it is
recommended that a fastener expert be consulted.

a
Washers made of cold worked material which are subjected to tensile stresses (e.g. when they are used on slotted
or enlarged holes) in service environment with chloride are more sensitive to stress corrosion cracking (SCC). For
information regarding resistance to str
...