Fasteners - Mechanical properties of corrosion-resistant stainless steel fasteners - Part 2: Nuts with specified grades and property classes (ISO 3506-2:2020)

This document specifies the mechanical and physical properties of nuts, with coarse pitch thread and fine pitch thread, made of corrosion-resistant stainless steels, when tested at the ambient temperature range of 10 °C to 35 °C. It specifies property classes in relation to austenitic, martensitic, ferritic and duplex (austenitic-ferritic) steel grades for nuts.
ISO 3506‑6 provides general rules and additional technical information on suitable stainless steels and their properties.
Nuts conforming to the requirements of this document are evaluated at the ambient temperature specified in paragraph 1. It is possible that they do not retain the specified mechanical and physical properties at elevated and/or lower temperatures.
NOTE 1  Fasteners conforming to the requirements of this document are used without restriction in applications ranging from ?20 °C to +150 °C; however, fasteners conforming to this document are also used for applications outside this range down to ?196 °C and up to +300 °C. For more details, see ISO 3506-6.
Outside the temperature range of ?20 °C to +150 °C, it is the responsibility of the user to determine the appropriate choice for a given application, in consultation with an experienced fastener metallurgist and by taking into account e.g. stainless steel composition, duration of exposure at elevated or low temperature, the effect of the temperature on the fastener mechanical properties and clamped parts, and the corrosive service environment of the bolted joint.
NOTE 2  ISO 3506‑5[1] is developed in order to assist in the selection of appropriate stainless steel grades and property classes intended for use at temperatures up to +800 °C.
This document applies to nuts:
—     with ISO metric thread in accordance with ISO 68‑1,
—     with diameter/pitch combinations in accordance with ISO 261 and ISO 262,
—     with coarse pitch thread M5 to M39, and fine pitch thread M8×1 to M39×3,
—     with thread tolerances in accordance with ISO 965‑1 and ISO 965‑2,
—     with specified property classes, including proof load,
—     with different nut styles: thin nuts, regular nuts and high nuts,
—     with a minimum nut height m ≥ 0,45D,
—     with a minimum outside diameter or width across flats s ≥ 1,45D (see Annex A),
—     of any shape, and
—     able to mate with bolts, screws and studs with property classes in accordance with ISO 3506‑1.
Stainless steel grades and property classes can be used for sizes outside the diameter limits of this document (i.e. for D < 5 mm or D > 39 mm), provided that all applicable chemical, mechanical and physical requirements are met.
This document does not specify requirements for functional properties such as:
—     torque/clamp force properties,
—     prevailing torque properties, or
—     weldability.
[1] Under preparation.

Mechanische Verbindungselemente - Mechanische Eigenschaften von Verbindungselementen aus korrosionsbeständigen nichtrostenden Stählen - Teil 2: Muttern mit festgelegten Stahlsorten und Festigkeitsklassen (ISO 3506-2:2020)

Dieses Dokument legt die mechanischen und physikalischen Eigenschaften von Muttern mit Regelgewinde und Feingewinde fest, die aus korrosionsbeständigen nichtrostenden Stählen gefertigt sind, und im Bereich der Umgebungstemperatur von 10 °C bis 35 °C geprüft werden. Es legt Festigkeitsklassen in Bezug auf austenitische, martensitische, ferritische Stahlsorten und austenitisch-ferittische Duplex Stahlsorten für Muttern fest.
In ISO 3506 6 werden allgemeine Regeln und zusätzliche technische Angaben zu geeigneten nichtrostenden Stählen und ihren Eigenschaften bereitgestellt.
Muttern, die den Anforderungen dieses Dokuments entsprechen, werden bei der in Absatz 1 angegebenen Umgebungstemperatur bewertet. Eventuell ändern sich die festgelegten mechanischen und physikalischen Eigenschaften bei höheren und/oder niedrigeren Temperaturen.
ANMERKUNG 1 Verbindungselemente, die den Anforderungen dieses Dokuments entsprechen, werden ohne Einschränkung für Anwendungen im Bereich zwischen −20 °C und +150 °C eingesetzt; Verbindungselemente, die diesem Dokument entsprechen, werden jedoch auch für die Anwendung außerhalb dieses Bereiches, von −196 °C und bis zu +300 °C, eingesetzt. Für weiterführende Einzelheiten, siehe ISO 3506 6.
Außerhalb des Temperaturbereichs von −20 °C bis +150 °C liegt es in der Verantwortlichkeit des An-wenders - unter Hinzuziehung eines erfahrenen Metallurgen für Verbindungselemente - eine geeignete Wahl für eine bestimmte Anwendung zu treffen, um z. B. die Zusammensetzung des nichtrostenden Stahls, die Dauer der Beanspruchung bei einer hohen oder niedrigen Temperatur, die Auswirkung der Temperatur auf die mechanischen Eigenschaften der Verbindungselemente und eingespannten Teile und die korrosive Einsatz¬umgebung der Schraubenverbindung zu berücksichtigt.
ANMERKUNG 2 ISO 3506 5  wird erarbeitet, um die Auswahl geeigneter Sorten nichtrostender Stähle und Festigkeits¬klassen zu unterstützen, die für die Anwendung bei hohen Temperaturen bis +800 °C vorgesehen sind.
Dieses Dokument gilt für Muttern:
- mit metrischem ISO-Gewinde nach ISO 68 1;
- mit Durchmesser-Steigungs-Kombinationen nach ISO 261 und ISO 262;
- mit Regelgewinde M5 bis M39 und Feingewinde M8×1 bis M39×3;
- mit Gewindetoleranzen nach ISO 965 1 und ISO 965 2;
- mit festgelegten Festigkeitsklassen, einschließlich Prüfkraft;
- unterschiedlicher Muttertypen: niedrige Muttern, normale Muttern und hohe Muttern;
- mit einer Mindesthöhe der Mutter von m ≥ 0,45D;
- mit einem Mindestaußendurchmesser oder einer Mindestschlüsselweite s ≥ 1,45D (siehe Anhang A);
- einer beliebigen Form; und
- die mit Schrauben der Festigkeitsklassen nach ISO 3506 1 gepaart werden können.
Sorten nichtrostender Stähle und Festigkeitsklassen können auch für Größen außerhalb der in diesem Doku¬ment festgelegten Grenzen für Durchmesser (d. h. D < 5 mm oder D > 39 mm) verwendet werden, voraus¬gesetzt, alle geltenden chemischen, mechanischen und physikalischen Anforderungen werden erfüllt.
Dieses Dokument legt keine Anforderungen an Funktionseigenschaften fest, wie:
- Drehmoment/Vorspannkraft-Eigenschaften;
- Sicherungseigenschaften; oder
- Schweißbarkeit.

Fixations - Caractéristiques mécaniques des fixations en acier inoxydable résistant à la corrosion - Partie 2: Écrous de grades et classes de qualité spécifiés (ISO 3506-2:2020)

Le présent document spécifie les caractéristiques mécaniques et physiques des écrous, à filetage à pas gros et à filetage à pas fin, en aciers inoxydables résistant à la corrosion, lorsque soumis à essai à la température ambiante de 10 °C à 35 °C. Il spécifie les classes de qualité en fonction des grades d'aciers inoxydables austénitiques, martensitiques, ferritiques et duplex (austéno-ferritiques) pour les écrous.
L'ISO 3506‑6 fournit des règles générales et des informations techniques supplémentaires sur les aciers inoxydables appropriés ainsi que leurs propriétés.
Les écrous conformes aux exigences du présent document sont évalués dans la plage de température ambiante spécifiée dans l'alinéa 1. Ils peuvent ne pas conserver les caractéristiques mécaniques et physiques spécifiées à des températures élevées et/ou basses.
NOTE 1    Les fixations conformes aux exigences du présent document sont utilisées sans restriction pour des applications dans la plage de ?20 °C à +150 °C; cependant, les fixations conformes au présent document sont également utilisées pour des applications en dehors de cette plage, en températures négatives jusqu'à ?196 °C et en températures élevées jusqu'à +300 °C. Pour d'avantage d'explications, voir l'ISO 3506‑6.
En dehors de la plage de température de ?20 °C à +150 °C , il est de la responsabilité de l'utilisateur de déterminer le choix approprié pour une application donnée en concertation avec un métallurgiste expérimenté en fixations et en prenant en considération plusieurs facteurs, par exemple la composition de l'acier inoxydable, la durée d'exposition à température élevée ou basse, l'effet de la température sur les caractéristiques mécaniques des fixations et des pièces assemblées, ainsi que l'environnement corrosif d'utilisation de l'assemblage vissé.
NOTE 2    L'ISO 3506‑5[1] est développé afin d'aider à la sélection des grades d'aciers inoxydables et des classes de qualité appropriées destinés à être utilisés à des températures jusqu'à +800 °C.
Le présent document s'applique aux écrous:
—          à filetage métrique ISO conforme à l'ISO 68‑1;
—          de combinaisons diamètre/pas, conformes à l'ISO 261 et à l'ISO 262;
—          de filetage M5 à M39 pour les pas gros, et de filetage M8×1 à M39×3 pour les pas fins;
—          de tolérances de filetage conformes à l'ISO 965‑1 et à l'ISO 965‑2;
—          de classes de qualité spécifiées, comprenant la charge d'épreuve;
—          de différents styles: écrous bas, écrous normaux et écrous hauts;
—          de hauteur minimale d'écrou m ≥ 0,45D;
—          de diamètre extérieur minimal ou de surplat minimum s ≥ 1,45D (voir Annexe A);
—          de forme quelconque; et
—          conçus pour être utilisés avec des vis, goujons et tiges filetées de classes de qualité conformes à l'ISO 3506‑1.
Les grades d'aciers inoxydables et classes de qualité peuvent être utilisés pour des dimensions en dehors des limites de diamètres du présent document (c'est-à-dire pour D < 5 mm ou D > 39 mm), à condition que toutes les exigences chimiques, mécaniques et physiques applicables soient satisfaites.
Le présent document ne spécifie pas d'exigence pour des caractéristiques fonctionnelles telles que:
—          les caractéristiques de couple/tension;
—          les caractéristiques d'autofreinage; ou
—          la soudabilité.
[1] En préparation.

Vezni elementi - Mehanske lastnosti veznih elementov iz nerjavnega jekla - 2. del: Matice z določenimi razredi in razredi trdnosti (ISO 3506-2:2020)

General Information

Status
Published
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
22-Apr-2020
Completion Date
22-Apr-2020

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SLOVENSKI STANDARD
SIST EN ISO 3506-2:2020
01-julij-2020
Nadomešča:
SIST EN ISO 3506-2:2011

Vezni elementi - Mehanske lastnosti veznih elementov iz nerjavnega jekla - 2. del:

Matice z določenimi razredi in razredi trdnosti (ISO 3506-2:2020)

Fasteners - Mechanical properties of corrosion-resistant stainless steel fasteners - Part

2: Nuts with specified grades and property classes (ISO 3506-2:2020)
Mechanische Verbindungselemente - Mechanische Eigenschaften von
Verbindungselementen aus korrosionsbeständigen nichtrostenden Stählen - Teil 2:
Muttern mit festgelegten Stahlsorten und Festigkeitsklassen (ISO 3506-2:2020)

Fixations - Caractéristiques mécaniques des fixations en acier inoxydable résistant à la

corrosion - Partie 2: Écrous de grades et classes de qualité spécifiés (ISO 3506-2:2020)

Ta slovenski standard je istoveten z: EN ISO 3506-2:2020
ICS:
21.060.20 Matice Nuts
SIST EN ISO 3506-2:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 3506-2:2020
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SIST EN ISO 3506-2:2020
EN ISO 3506-2
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2020
EUROPÄISCHE NORM
ICS 21.060.20 Supersedes EN ISO 3506-2:2009
English Version
Fasteners - Mechanical properties of corrosion-resistant
stainless steel fasteners - Part 2: Nuts with specified
grades and property classes (ISO 3506-2:2020)

Fixations - Caractéristiques mécaniques des fixations Mechanische Verbindungselemente - Mechanische

en acier inoxydable résistant à la corrosion - Partie 2: Eigenschaften von Verbindungselementen aus

Écrous de grades et classes de qualité spécifiés (ISO korrosionsbeständigen nichtrostenden Stählen - Teil 2:

3506-2:2020) Muttern mit festgelegten Stahlsorten und
Festigkeitsklassen (ISO 3506-2:2020)
This European Standard was approved by CEN on 28 March 2020.

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, Turkey 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

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 3506-2:2020 E

worldwide for CEN national Members.
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SIST EN ISO 3506-2:2020
EN ISO 3506-2:2020 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 3506-2:2020
EN ISO 3506-2:2020 (E)
European foreword

This document (EN ISO 3506-2:2020) has been prepared by Technical Committee ISO/TC 2 "Fasteners"

in collaboration with 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 October 2020, and conflicting national standards shall

be withdrawn at the latest by October 2020.

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.

This document supersedes EN ISO 3506-2:2009.

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, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO 3506-2:2020 has been approved by CEN as EN ISO 3506-2:2020 without any

modification.
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SIST EN ISO 3506-2:2020
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SIST EN ISO 3506-2:2020
INTERNATIONAL ISO
STANDARD 3506-2
Third edition
2020-04
Fasteners — Mechanical properties
of corrosion-resistant stainless steel
fasteners —
Part 2:
Nuts with specified grades and
property classes
Fixations — Caractéristiques mécaniques des fixations en acier
inoxydable résistant à la corrosion —
Partie 2: Écrous de grades et classes de qualité spécifiés
Reference number
ISO 3506-2:2020(E)
ISO 2020
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SIST EN ISO 3506-2:2020
ISO 3506-2:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
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SIST EN ISO 3506-2:2020
ISO 3506-2:2020(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ..............................................................................................................................................................................................................................vii

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 2

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Symbols .......................................................................................................................................................................................................................... 3

5 Designation systems ......................................................................................................................................................................................... 4

5.1 Designation of nut styles ................................................................................................................................................................ 4

5.2 Designation system for stainless steel grades and property classes ........................................................ 4

5.2.1 General...................................................................................................................................................................................... 4

5.2.2 Designation of stainless steel grades (first block) .............................................................................. 5

5.2.3 Designation of property classes (second block) for regular nuts (style 1)

and high nuts (style 2) ................................................................................................................................................ 6

5.2.4 Designation of property classes (second block) for thin nuts (style 0) ........................... 6

6 Design of bolt and nut assemblies ...................................................................................................................................................... 6

7 Materials ....................................................................................................................................................................................................................... 7

7.1 Chemical composition ...................................................................................................................................................................... 7

7.2 Heat treatment for martensitic stainless steel nuts ................................................................................................ 8

7.3 Finish ............................................................................................................................................................................................................... 9

7.4 Corrosion resistance .......................................................................................................................................................................... 9

8 Mechanical and physical properties ................................................................................................................................................ 9

9 Inspection .................................................................................................................................................................................................................14

9.1 Manufacturer’s inspection .........................................................................................................................................................14

9.2 Supplier’s inspection ......................................................................................................................................................................14

9.3 Purchaser’s inspection ..................................................................................................................................................................15

9.4 Delivery of test results ...................................................................................................................................................................15

10 Test methods ..........................................................................................................................................................................................................15

10.1 Proof load test .......................................................................................................................................................................................15

10.1.1 General...................................................................................................................................................................................15

10.1.2 Applicability ......................................................................................................................................................................15

10.1.3 Apparatus ............................................................................................................................................................................15

10.1.4 Testing device ..................................................................................................................................................................15

10.1.5 Test procedure ................................................................................................................................................................17

10.1.6 Addition to test procedure for prevailing torque nuts .................................................................17

10.1.7 Test results and requirements ..........................................................................................................................17

10.2 Hardness test .........................................................................................................................................................................................18

10.2.1 General...................................................................................................................................................................................18

10.2.2 Test procedure ................................................................................................................................................................18

10.2.3 Test results and requirements ..........................................................................................................................19

11 Nut marking and labelling .......................................................................................................................................................................19

11.1 Nut marking ............................................................................................................................................................................................19

11.1.1 General requirements for marking ...............................................................................................................19

11.1.2 Marking of property class for nuts with full loadability (regular and high nuts) .19

11.1.3 Marking of property class for nuts with reduced loadability (thin nuts) ....................20

11.1.4 Additional marking .....................................................................................................................................................20

11.2 Manufacturer’s identification mark ...................................................................................................................................20

11.3 Marking on the nuts .........................................................................................................................................................................20

11.3.1 Hexagon nuts ....................................................................................................................................................................20

11.3.2 Other types of nuts ......................................................................................................................................................22

11.3.3 Left-hand thread marking .....................................................................................................................................22

© ISO 2020 – All rights reserved iii
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SIST EN ISO 3506-2:2020
ISO 3506-2:2020(E)

11.4 Marking of the packages (labelling) ..................................................................................................................................22

Annex A (informative) Design principles of stainless steel nuts ..........................................................................................23

Annex B (normative) Thread dimensions of the test mandrel for proof load ........................................................25

Bibliography .............................................................................................................................................................................................................................27

iv © ISO 2020 – All rights reserved
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SIST EN ISO 3506-2:2020
ISO 3506-2:2020(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 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.

This third edition cancels and replaces the second edition (ISO 3506-2:2009) which has been technically

revised.
The main changes compared to the previous edition are as follows:

— annexes common to several parts of the ISO 3506 series have been withdrawn from this document

and are now included in a new document (ISO 3506-6);

— duplex (austenitic-ferritic) stainless steels for property classes 70, 80 and 100 have been added (see

Figure 1);

— property class 100 for austenitic stainless steel grades as well as grade A8 have been added (see

Figure 1);
— information for nut styles (see 5.1) has been added;

— design of stainless steel bolt and nut assemblies (see Clause 6), and design principles of stainless

steel nuts (see Annex A) have been added;
— finish (see 7.3) has been improved;

— calculated proof load values (see Tables 5 to 8) and rounding rules have been added;

— requirements and guidance for inspection procedures (see Clause 9) have been added;

— thread dimensions of the test mandrel for proof load (see Annex B) have been added;

— operational temperature ranges (see Clause 1) have been clarified;
— test methods for proof load and hardness have been improved (see Clause 10);
© ISO 2020 – All rights reserved v
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SIST EN ISO 3506-2:2020
ISO 3506-2:2020(E)

— nut marking and labelling especially for thin nuts with reduced loadability (see Clause 11) have

been added;

— structure and content of this document have been brought in line with ISO 898-2.

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.
vi © ISO 2020 – All rights reserved
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SIST EN ISO 3506-2:2020
ISO 3506-2:2020(E)
Introduction

The ISO 3506 series consists of the following parts, under the general title Fasteners — Mechanical

properties of corrosion-resistant stainless steel fasteners:
— Part 1: Bolts, screws and studs with specified grades and property classes
— Part 2: Nuts with specified grades and property classes
— Part 3 : Set screws and similar fasteners not under tensile stress
— Part 4 : Tapping screws

— Part 5 :Special fasteners (also including fasteners from nickel alloys) for high temperature applications

— Part 6: General rules for the selection of stainless steels and nickel alloys for fasteners.

The properties of stainless steel fasteners result from the chemical composition of the material

(especially corrosion resistance) and from the mechanical properties due to the manufacturing

processes. Ferritic, austenitic and duplex (austenitic-ferritic) stainless steel fasteners are generally

manufactured by cold working; they consequently do not have homogeneous local material properties

when compared to quenched and tempered fasteners.

Austenitic-ferritic stainless steels referred to as duplex stainless steels were originally invented in the

1930s. Standard duplex grades used today have been developed since the 1980s. Fasteners made of

duplex stainless steels have been long established in a range of applications. This document was revised

to reflect their standardization.

All duplex stainless steel grades show improved resistance to stress corrosion cracking compared to

the commonly used A1 to A5 austenitic grades. Most duplex grades also show higher levels of pitting

corrosion resistance, where D2 matches at least A2 and where D4 matches at least A4.

Complementary detailed explanations about definitions of stainless steel grades and properties are

specified in ISO 3506-6.

1) It is intended to revise ISO 3506-3 and ISO 3506-4 in the future in order to include the reference to ISO 3506-6.

2) Under preparation.
© ISO 2020 – All rights reserved vii
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SIST EN ISO 3506-2:2020
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SIST EN ISO 3506-2:2020
INTERNATIONAL STANDARD ISO 3506-2:2020(E)
Fasteners — Mechanical properties of corrosion-resistant
stainless steel fasteners —
Part 2:
Nuts with specified grades and property classes
1 Scope

This document specifies the mechanical and physical properties of nuts, with coarse pitch thread and

fine pitch thread, made of corrosion-resistant stainless steels, when tested at the ambient temperature

range of 10 °C to 35 °C. It specifies property classes in relation to austenitic, martensitic, ferritic and

duplex (austenitic-ferritic) steel grades for nuts.

ISO 3506-6 provides general rules and additional technical information on suitable stainless steels and

their properties.

Nuts conforming to the requirements of this document are evaluated at the ambient temperature

specified in paragraph 1. It is possible that they do not retain the specified mechanical and physical

properties at elevated and/or lower temperatures.

NOTE 1 Fasteners conforming to the requirements of this document are used without restriction in

applications ranging from –20 °C to +150 °C; however, fasteners conforming to this document are also used for

applications outside this range down to –196 °C and up to +300 °C. For more details, see ISO 3506-6.

Outside the temperature range of –20 °C to +150 °C, it is the responsibility of the user to determine the

appropriate choice for a given application, in consultation with an experienced fastener metallurgist

and by taking into account e.g. stainless steel composition, duration of exposure at elevated or low

temperature, the effect of the temperature on the fastener mechanical properties and clamped parts,

and the corrosive service environment of the bolted joint.

NOTE 2 ISO 3506-5 is developed in order to assist in the selection of appropriate stainless steel grades and

property classes intended for use at temperatures up to +800 °C.
This document applies to nuts:
— with ISO metric thread in accordance with ISO 68-1,
— with diameter/pitch combinations in accordance with ISO 261 and ISO 262,
— with coarse pitch thread M5 to M39, and fine pitch thread M8×1 to M39×3,
— with thread tolerances in accordance with ISO 965-1 and ISO 965-2,
— with specified property classes, including proof load,
— with different nut styles: thin nuts, regular nuts and high nuts,
— with a minimum nut height m ≥ 0,45D,
— with a minimum outside diameter or width across flats s ≥ 1,45D (see Annex A),
— of any shape, and

— able to mate with bolts, screws and studs with property classes in accordance with ISO 3506-1.

3) Under preparation.
© ISO 2020 – All rights reserved 1
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SIST EN ISO 3506-2:2020
ISO 3506-2:2020(E)

Stainless steel grades and property classes can be used for sizes outside the diameter limits of this

document (i.e. for D < 5 mm or D > 39 mm), provided that all applicable chemical, mechanical and

physical requirements are met.
This document does not specify requirements for functional properties such as:
— torque/clamp force properties,
— prevailing torque properties, or
— 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 898-1, Mechanical properties of fasteners made of carbon steel and alloy steel — Part 1: Bolts, screws

and studs with specified property classes — Coarse thread and fine pitch thread

ISO 1891-4, Fasteners — Vocabulary — Part 4: Control, inspection, delivery, acceptance and quality

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 6506-1, Metallic materials — Brinell hardness test — Part 1: Test method
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 6508-1, Metallic materials — Rockwell hardness test — Part 1: Test method

ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:

Tension/compression testing machines — Calibration and verification of the force-measuring system

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 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/
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]
2 © ISO 2020 – All rights reserved
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SIST EN ISO 3506-2:2020
ISO 3506-2:2020(E)
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
martensitic stainless steel

stainless steel (3.1) with high amounts of chromium but very little nickel or other alloying elements,

which can be hardened by heat treatment for increasing strength but with reduced ductility, and with

highly magnetic properties
[SOURCE: ISO 3506-1:2020, 3.7]
3.4
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]
3.5
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
For the purposes of this document, the following symbols apply.
A nominal stress area in thread, mm
s,nom
D nominal thread diameter of the nut, mm
D basic pitch diameter of internal thread, mm
d hole diameter for the grip, mm
F proof load, N
h thickness of the grip, mm
m height of the nut, mm
P pitch of the thread, mm
S stress under proof load, MPa
s width across flats, mm
© ISO 2020 – All rights reserved 3
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SIST EN ISO 3506-2:2020
ISO 3506-2:2020(E)
5 Designation systems
5.1 Designation of nut styles

This document specifies requirements for three styles of nuts according to their height:

a) nuts with full loadability:
— regular nuts (style 1) with minimum
...

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