EN ISO 3506-2:2020
(Main)Fasteners - Mechanical properties of corrosion-resistant stainless steel fasteners - Part 2: Nuts with specified grades and property classes (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)
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
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
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
77.140.20 Visokokakovostna jekla Stainless steels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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.
Contents Page
European foreword . 3
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.
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
ISO 3506-2:2020(E)
© 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
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CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
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Published in Switzerland
ii © ISO 2020 – All rights reserved
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 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
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 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
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
1)
— Part 3 : Set screws and similar fasteners not under tensile stress
1)
— Part 4 : Tapping screws
2)
— 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.
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.
3)
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 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
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
h
F proof load, N
p
h thickness of the grip, mm
m height of the nut, mm
P pitch of the thread, mm
S stress under proof load, MPa
p
s width across flats, mm
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 height 0,80 D ≤ m < 0,89 D, see Annex A,
min
— high nuts (style 2) with minimum height m ≥ 0,89 D, see Annex A;
min
b) nuts with reduced loadability: thin nuts (style 0) with minimum height 0,45 D ≤ m < 0,80 D.
min
5.2 Designation system for stainless steel grades and property classes
5.2.1 General
The standardized combinations of stainless steel grades and property classes are specified in Clause 8,
Table 3 or 4.
The designation system for stainless steel grades and property classes for nuts consists of two blocks,
separated by a hyphen, as specified in Figure 1. The first block designates the stainless steel grade, and
the second block the property class of the nut.
4 © ISO 2020 – All rights reserved
ISO 3506-2:2020(E)
a
For low carbon austenitic stainless steels with carbon content not exceeding 0,030 %, nuts can additionally be
marked or designated with the letter "L" just after the grade. Example: A4L-80.
b
For information only.
Figure 1 — Designation system for stainless steel grades and property classes for nuts
The marking, labelling and designation of nuts with stainless steel grade and property class shall be as
specified in Clause 11. For thin nuts with reduced loadability, the digit “0” shall precede the property
class as specified in 11.3.
The designation system of this document may be used for sizes outside the diameter limits specified in
Clause 1 (i.e. D < 5 mm or D > 39 mm), provided that all applicable chemical, mechanical and physical
requirements are met.
5.2.2 Designation of stainless steel grades (first block)
The designation of the stainless steel grade (first block) consists of one letter which specifies the
stainless steel group:
— A for austenitic,
— C for martensitic,
— F for ferritic,
ISO 3506-2:2020(E)
— D for duplex (austenitic-ferritic),
and
— a digit which specifies the range of chemical compositions within this stainless steel group.
The chemical compositions of stainless steel groups and grades classified in Figure 1 are specified in
Table 2.
5.2.3 Designation of property classes (second block) for regular nuts (style 1) and high nuts
(style 2)
The designation of the property class (second block) consists of a number corresponding to 1/10 of the
stress under proof load of the nut in accordance with Table 3 or 4; it also corresponds to the appropriate
stainless steel property class of the bolt, screw and stud with which it should be mated.
EXAMPLE 1 A2-70 specifies an austenitic stainless steel nut, work hardened, with stress under proof load of
700 MPa, for nuts with full loadability (m ≥ 0,8D).
EXAMPLE 2 C1-110 specifies a martensitic stainless steel nut, quenched and tempered, with stress under
proof load of 1 100 MPa, for nuts with full loadability (m ≥ 0,8D).
5.2.4 Designation of property classes (second block) for thin nuts (style 0)
The designation of the property class (second block) for thin nuts (style 0) consists of a digit and a
number, specified in the following ways:
— the first digit is zero, indicating that the loadability of the thin nuts is reduced in comparison with
the loadability of a regular or high nut in accordance with 5.2.3, and therefore thread stripping can
occur when overloaded,
— the following number corresponds to 1/10 of the stress under proof load of the nut on a hardened
test mandrel in megapascals; it also corresponds to half of the appropriate property class of the
stainless steel fastener with which the thin nut should be mated.
EXAMPLE A4-040 specifies an austenitic stainless steel thin nut, with the same material and manufacturing
process (work hardened, high strength) as a regular nut A4-80, but with stress under proof load of 400 MPa
(reduced loadability) because of its height (m < 0,80 D).
6 Design of bolt and nut assemblies
Property class combinations of nuts to bolts, screws and studs shall be in accordance with Table 1.
Table 1 — Property class combination of nuts to bolts, screws and studs
Minimum property class of the mating nuts
Property class of
Regular and high nuts Thin nuts
bolts, screws and studs
(style 1 and style 2) (style 0)
45 45 022
50 50 025
60 60 030
70 70 035
80 80 040
100 100 050
110 110 055
For full loadability, regular nuts (style 1) and high nuts (style 2) shall be used.
6 © ISO 2020 – All rights reserved
ISO 3506-2:2020(E)
As example, a bolt A4-70 is usually mated with a nut A4-70, however it may be mated with a nut A4-80.
For all-metal prevailing torque nuts, only the same bolt and nut property class shall be combined.
Thin nuts (style 0) have a reduced loadability and are not designed to provide resistance against thread
stripping. A thin nut used as jam nut shall be assembled together with a regular nut or a high nut.
For other combinations than those specified in Table 1, it is recommended to check the compatibility of
the fasteners before installation in the application.
Explanations of basic design principles of nuts and loadability of bolted assemblies are given in Annex A.
7 Materials
7.1 Chemical composition
Table 2 specifies the limits for chemical composition of the stainless steel grades for fasteners. The
chemical composition shall be assessed in accordance with the relevant International Standards.
The final choice of the chemical composition within the specified stainless steel grade is at the discretion
of the manufacturer, unless otherwise agreed between the purchaser and the manufacturer.
The required appropriate stainless steel grade suitable for an application shall be selected in accordance
with the specifications defined in ISO 3506-6.
ISO 3506-2:2020(E)
Table 2 — Stainless steel grades — Chemical composition
a
Chemical composition
Stainless
b Other elements
(cast analysis, mass fraction in %)
steel
and notes
grade
C Si Mn P S Cr Mo Ni Cu N
0,15 to 16,0 to 5,0 to 1,75 to
c,d,e
A1 0,12 1,00 6,5 0,020 0,70 —
0,35 19,0 10,0 2,25
15,0 to 8,0 to
f g,h
A2 0,10 1,00 2,00 0,050 0,030 — 4,0 —
20,0 19,0
17,0 to 9,0 to 5C ≤ Ti ≤ 0,80 and/or
f
Austenitic A3 0,08 1,00 2,00 0,045 0,030 — 1,00 —
19,0 12,0 10C ≤ Nb ≤ 1,00
16,0 to 2,00 to 10,0 to
h,i
A4 0,08 1,00 2,00 0,045 0,030 4,0 —
18,5 3,00 15,0
16,0 to 2,00 to 10,5 to 5C ≤ Ti ≤ 0,80 and/or
A5 0,08 1,00 2,00 0,045 0,030 1,00 —
i
18,5 3,00 14,0 10C ≤ Nb ≤ 1,00
19,0 to 6,0 to 17,5 to
A8 0,030 1,00 2,00 0,040 0,030 1,50 — —
22,0 7,0 26,0
0,09 to 11,5 to
i
C1 1,00 1,00 0,050 0,030 — 1,00 — —
0,15 14,0
0,17 to 16,0 to 1,50 to
Martensitic C3 1,00 1,00 0,040 0,030 — — — —
0,25 18,0 2,50
0,08 to 0,15 to 12,0 to
c,i
C4 1,00 1,50 0,060 0,60 1,00 — —
0,15 0,35 14,0
15,0 to
f j
Ferritic F1 0,08 1,00 1,00 0,040 0,030 — 1,00 — —
18,0
19,0 to 0,10 to 1,50 to 0,05 to Cr+3,3Mo + 16N ≤ 24,0
D2 0,040 1,00 6,0 0,040 0,030 3,00
k
24,0 1,00 5,5 0,20
21,0 to 0,10 to 1,00 to 0,05 to 24,0 < Cr+3,3Mo + 16N
Duplex D4 0,040 1,00 6,0 0,040 0,030 3,00
k
25,0 2,00 5,5 0,30
21,0 to 2,50 to 4,5 to 0,08 to
D6 0,030 1,00 2,00 0,040 0,015 — —
23,0 3,5 6,5 0,35
24,0 to 3,00 to 6,0 to 0,20 to
D8 0,030 1,00 2,00 0,035 0,015 2,50 W ≤ 1,00
26,0 4,5 8,0 0,35
a
According to material standards, values are maximum unless otherwise indicated and the number of digits shown is in accordance with usual rules;
see e.g. EN 10088 (all parts).
b
In case of dispute, product analysis applies.
c
Selenium can be used to replace sulphur; however, restrictions may apply to its use.
d
If the nickel content is below 8,0 %, the minimum manganese content shall be 5,0 %.
e
There is no minimum limit to the copper content provided that the nickel content is greater than 8,0 %.
f
Molybdenum may be present at the discretion of the manufacturer. However, if for some applications limiting of the molybdenum content is essential,
this shall be stated at the time of ordering by the purchaser.
g
If the chromium content is below 17,0 %, the minimum nickel content should be 12,0 %.
h
For austenitic stainless steels having a maximum carbon content of 0,030 %, nitrogen may be present but shall not exceed 0,22 %.
i
At the discretion of the manufacturer the carbon content may be higher as necessary in order to obtain the specified mechanical properties for larger
diameters, but shall not exceed 0,12 % for austenitic steels.
j
Titanium and/or niobium may be included to improve corrosion resistance.
k
This formula is used solely for the purpose of classifying duplex steels in accordance with this document (it is not intended to be used as a selection
criterion for corrosion resistance).
For the choice of the appropriate stainless steel grade suitable for a specific application, see ISO 3506-6.
Examples of stainless steels in accordance with Table 2 are also given in ISO 3506-6.
7.2 Heat treatment for martensitic stainless steel nuts
Regular and high nuts of grades and property classes C1-70, C3-80 and C4-70, and thin nuts of grades
and property classes C1-035, C3-040 and C4-035 shall be quenched and tempered.
Regular and high nuts of grade and property class C1-110 and thin nuts of grade and property class C1-
055 shall be quenched and tempered, with a minimum tempering temperature of 275 °C.
8 © ISO 2020 – All rights reserved
ISO 3506-2:2020(E)
7.3 Finish
Unless otherwise specified, nuts in accordance with this document shall be supplied clean and bright.
For maximum corrosion resistance, passivation is recommended. Nuts that are passivated in accordance
with ISO 16048 may additionally be referenced on the label with the letter “P” immediately after the
property class symbol (see 11.4).
NOTE 1 Passivated nuts do not always show a bright surface finish.
Nuts are often used in bolted joints where the preload is achieved by torque tightening. Therefore,
lubrication of stainless steel nuts is strongly recommended in order to avoid galling during tightening.
NOTE 2 Several parameters can increase the risk of galling for stainless steel nuts in bolted assemblies during
tightening such as thread damage, high preload, high tightening speed.
NOTE 3 For the time being, requirements concerning surface discontinuities, torque/clamp force and
prevailing torque properties are not specified in International Standards for stainless steel fasteners.
A controlled torque/clamp force relationship can be obtained for stainless steel fasteners by means
of an adequate finish, either just with a lubricant or with a coating, top coat and/or sealer including
lubricant. In this case, the designation and/or labelling should include the letters “Lu” immediately
after the symbol of the property class, e.g. A4-80Lu. In conjunction, appropriate measures and means of
tightening should be selected in order to achieve the required preload.
When specific requirements are necessary, it shall be agreed between the supplier and the purchaser at
the time of the order.
7.4 Corrosion resistance
For corrosion resistance purpose, nuts should be mated with bolts, screws, studs and washers of the
same stainless steel grade (e.g. nuts A2 with bolts A2, etc.). Other combinations are possible (e.g. nuts
A4 with bolts D4), providing that:
— the component with the lowest corrosion resistance shall always be taken into account,
— the risk of galling should be considered, and
— it is strongly recommended that an experienced fastener metallurgist be consulted.
When using stainless steel fasteners with non-stainless steel parts in bolted joints, e.g. galvanized
steels, it is advised that the use of isolation components be considered in order to avoid galvanic
corrosion.
8 Mechanical and physical properties
When tested by the methods specified in Clause 10, the nuts of the specified stainless steel grade and
property class shall meet, at ambient temperature, the requirements for the proof load and for the
hardness specified in Tables 3 to 8, regardless of which tests are performed during manufacture or
final inspection.
Although a great number of stainless steel grades and property classes are specified in this document,
this does not mean that all combinations are appropriate due to the properties of the material in
conjunction with the fastener geometry. Nevertheless, some combinations of grades and property
classes may not be available on the market. For non-standard fasteners, it is recommended that a
fastener expert be consulted.
ISO 3506-2:2020(E)
Table 3 — Mechanical properties for nuts — Austenitic and duplex grades
Regular nuts and high nuts Thin nuts
(style 1 and style 2) (style 0)
Stainless steel Property class Stress under Property class Stress under
a b
grade designation proof load designation proof load
and symbol S and symbol S
p p
MPa MPa
50 500 025 250
A1 A2
70 700 035 350
A3
80 800 040 400
50 500 025 250
Austenitic 70 700 035 350
A4 A5
80 800 040 400
100 1 000 050 500
70 700 035 350
A8 80 800 040 400
100 1 000 050 500
70 700 035 350
D2 D4
Duplex 80 800 040 400
D6 D8
100 1 000 050 500
a
Proof load values for regular and high nuts (full loadability) are specified in Table 5 for coarse pitch thread, and in
Table 6 for fine pitch thread.
b
Proof load values for thin nuts (reduced loadability) are specified in Table 7 for coarse pitch thread, and in Table 8 for
fine pitch thread.
Table 4 — Mechanical properties for nuts — Martensitic and ferritic grades
Regular nuts and high nuts Thin nuts
All nuts
(style 1 and style 2) (style 0)
Stainless steel Property class Stress under Property class Stress under Hardness
a b
grade designation and proof load designation and proof load
min. to max.
symbol S symbol S
p p
MPa MPa HV HRC HBW
50 500 025 250 155 to 220 — 147 to 209
C1 70 700 035 350 220 to 330 20 to 34 209 to 314
c c
110 1 100 055 550 350 to 440 36 to 45 —
Martensitic
C3 80 800 040 400 240 to 340 21 to 35 228 to 323
50 500 025 250 155 to 220 — 147 to 209
C4
70 700 035 350 220 to 330 20 to 34 209 to 314
45 450 022 225 135 to 220 — 128 to 209
d
Ferritic F1
60 600 030 300 180 to 285 — 171 to 271
a
Proof load values for regular and high nuts (full loadability) are specified in Table 5 for coarse pitch thread, and in Table 6 for fine pitch thread.
b
Proof load values for thin nuts (reduced loadability) are specified in Table 7 for coarse pitch thread, and in Table 8 for fine pitch thread.
c
Hardened and tempered at a minimum tempering temperature of 275 °C.
d
Only for nominal thread diameters D ≤
...
SLOVENSKI STANDARD
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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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.
Contents Page
European foreword . 3
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.
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
ISO 3506-2:2020(E)
© 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
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Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
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Published in Switzerland
ii © ISO 2020 – All rights reserved
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 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
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 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
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
1)
— Part 3 : Set screws and similar fasteners not under tensile stress
1)
— Part 4 : Tapping screws
2)
— 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.
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.
3)
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 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
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
h
F proof load, N
p
h thickness of the grip, mm
m height of the nut, mm
P pitch of the thread, mm
S stress under proof load, MPa
p
s width across flats, mm
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 height 0,80 D ≤ m < 0,89 D, see Annex A,
min
— high nuts (style 2) with minimum height m ≥ 0,89 D, see Annex A;
min
b) nuts with reduced loadability: thin nuts (style 0) with minimum height 0,45 D ≤ m < 0,80 D.
min
5.2 Designation system for stainless steel grades and property classes
5.2.1 General
The standardized combinations of stainless steel grades and property classes are specified in Clause 8,
Table 3 or 4.
The designation system for stainless steel grades and property classes for nuts consists of two blocks,
separated by a hyphen, as specified in Figure 1. The first block designates the stainless steel grade, and
the second block the property class of the nut.
4 © ISO 2020 – All rights reserved
ISO 3506-2:2020(E)
a
For low carbon austenitic stainless steels with carbon content not exceeding 0,030 %, nuts can additionally be
marked or designated with the letter "L" just after the grade. Example: A4L-80.
b
For information only.
Figure 1 — Designation system for stainless steel grades and property classes for nuts
The marking, labelling and designation of nuts with stainless steel grade and property class shall be as
specified in Clause 11. For thin nuts with reduced loadability, the digit “0” shall precede the property
class as specified in 11.3.
The designation system of this document may be used for sizes outside the diameter limits specified in
Clause 1 (i.e. D < 5 mm or D > 39 mm), provided that all applicable chemical, mechanical and physical
requirements are met.
5.2.2 Designation of stainless steel grades (first block)
The designation of the stainless steel grade (first block) consists of one letter which specifies the
stainless steel group:
— A for austenitic,
— C for martensitic,
— F for ferritic,
ISO 3506-2:2020(E)
— D for duplex (austenitic-ferritic),
and
— a digit which specifies the range of chemical compositions within this stainless steel group.
The chemical compositions of stainless steel groups and grades classified in Figure 1 are specified in
Table 2.
5.2.3 Designation of property classes (second block) for regular nuts (style 1) and high nuts
(style 2)
The designation of the property class (second block) consists of a number corresponding to 1/10 of the
stress under proof load of the nut in accordance with Table 3 or 4; it also corresponds to the appropriate
stainless steel property class of the bolt, screw and stud with which it should be mated.
EXAMPLE 1 A2-70 specifies an austenitic stainless steel nut, work hardened, with stress under proof load of
700 MPa, for nuts with full loadability (m ≥ 0,8D).
EXAMPLE 2 C1-110 specifies a martensitic stainless steel nut, quenched and tempered, with stress under
proof load of 1 100 MPa, for nuts with full loadability (m ≥ 0,8D).
5.2.4 Designation of property classes (second block) for thin nuts (style 0)
The designation of the property class (second block) for thin nuts (style 0) consists of a digit and a
number, specified in the following ways:
— the first digit is zero, indicating that the loadability of the thin nuts is reduced in comparison with
the loadability of a regular or high nut in accordance with 5.2.3, and therefore thread stripping can
occur when overloaded,
— the following number corresponds to 1/10 of the stress under proof load of the nut on a hardened
test mandrel in megapascals; it also corresponds to half of the appropriate property class of the
stainless steel fastener with which the thin nut should be mated.
EXAMPLE A4-040 specifies an austenitic stainless steel thin nut, with the same material and manufacturing
process (work hardened, high strength) as a regular nut A4-80, but with stress under proof load of 400 MPa
(reduced loadability) because of its height (m < 0,80 D).
6 Design of bolt and nut assemblies
Property class combinations of nuts to bolts, screws and studs shall be in accordance with Table 1.
Table 1 — Property class combination of nuts to bolts, screws and studs
Minimum property class of the mating nuts
Property class of
Regular and high nuts Thin nuts
bolts, screws and studs
(style 1 and style 2) (style 0)
45 45 022
50 50 025
60 60 030
70 70 035
80 80 040
100 100 050
110 110 055
For full loadability, regular nuts (style 1) and high nuts (style 2) shall be used.
6 © ISO 2020 – All rights reserved
ISO 3506-2:2020(E)
As example, a bolt A4-70 is usually mated with a nut A4-70, however it may be mated with a nut A4-80.
For all-metal prevailing torque nuts, only the same bolt and nut property class shall be combined.
Thin nuts (style 0) have a reduced loadability and are not designed to provide resistance against thread
stripping. A thin nut used as jam nut shall be assembled together with a regular nut or a high nut.
For other combinations than those specified in Table 1, it is recommended to check the compatibility of
the fasteners before installation in the application.
Explanations of basic design principles of nuts and loadability of bolted assemblies are given in Annex A.
7 Materials
7.1 Chemical composition
Table 2 specifies the limits for chemical composition of the stainless steel grades for fasteners. The
chemical composition shall be assessed in accordance with the relevant International Standards.
The final choice of the chemical composition within the specified stainless steel grade is at the discretion
of the manufacturer, unless otherwise agreed between the purchaser and the manufacturer.
The required appropriate stainless steel grade suitable for an application shall be selected in accordance
with the specifications defined in ISO 3506-6.
ISO 3506-2:2020(E)
Table 2 — Stainless steel grades — Chemical composition
a
Chemical composition
Stainless
b Other elements
(cast analysis, mass fraction in %)
steel
and notes
grade
C Si Mn P S Cr Mo Ni Cu N
0,15 to 16,0 to 5,0 to 1,75 to
c,d,e
A1 0,12 1,00 6,5 0,020 0,70 —
0,35 19,0 10,0 2,25
15,0 to 8,0 to
f g,h
A2 0,10 1,00 2,00 0,050 0,030 — 4,0 —
20,0 19,0
17,0 to 9,0 to 5C ≤ Ti ≤ 0,80 and/or
f
Austenitic A3 0,08 1,00 2,00 0,045 0,030 — 1,00 —
19,0 12,0 10C ≤ Nb ≤ 1,00
16,0 to 2,00 to 10,0 to
h,i
A4 0,08 1,00 2,00 0,045 0,030 4,0 —
18,5 3,00 15,0
16,0 to 2,00 to 10,5 to 5C ≤ Ti ≤ 0,80 and/or
A5 0,08 1,00 2,00 0,045 0,030 1,00 —
i
18,5 3,00 14,0 10C ≤ Nb ≤ 1,00
19,0 to 6,0 to 17,5 to
A8 0,030 1,00 2,00 0,040 0,030 1,50 — —
22,0 7,0 26,0
0,09 to 11,5 to
i
C1 1,00 1,00 0,050 0,030 — 1,00 — —
0,15 14,0
0,17 to 16,0 to 1,50 to
Martensitic C3 1,00 1,00 0,040 0,030 — — — —
0,25 18,0 2,50
0,08 to 0,15 to 12,0 to
c,i
C4 1,00 1,50 0,060 0,60 1,00 — —
0,15 0,35 14,0
15,0 to
f j
Ferritic F1 0,08 1,00 1,00 0,040 0,030 — 1,00 — —
18,0
19,0 to 0,10 to 1,50 to 0,05 to Cr+3,3Mo + 16N ≤ 24,0
D2 0,040 1,00 6,0 0,040 0,030 3,00
k
24,0 1,00 5,5 0,20
21,0 to 0,10 to 1,00 to 0,05 to 24,0 < Cr+3,3Mo + 16N
Duplex D4 0,040 1,00 6,0 0,040 0,030 3,00
k
25,0 2,00 5,5 0,30
21,0 to 2,50 to 4,5 to 0,08 to
D6 0,030 1,00 2,00 0,040 0,015 — —
23,0 3,5 6,5 0,35
24,0 to 3,00 to 6,0 to 0,20 to
D8 0,030 1,00 2,00 0,035 0,015 2,50 W ≤ 1,00
26,0 4,5 8,0 0,35
a
According to material standards, values are maximum unless otherwise indicated and the number of digits shown is in accordance with usual rules;
see e.g. EN 10088 (all parts).
b
In case of dispute, product analysis applies.
c
Selenium can be used to replace sulphur; however, restrictions may apply to its use.
d
If the nickel content is below 8,0 %, the minimum manganese content shall be 5,0 %.
e
There is no minimum limit to the copper content provided that the nickel content is greater than 8,0 %.
f
Molybdenum may be present at the discretion of the manufacturer. However, if for some applications limiting of the molybdenum content is essential,
this shall be stated at the time of ordering by the purchaser.
g
If the chromium content is below 17,0 %, the minimum nickel content should be 12,0 %.
h
For austenitic stainless steels having a maximum carbon content of 0,030 %, nitrogen may be present but shall not exceed 0,22 %.
i
At the discretion of the manufacturer the carbon content may be higher as necessary in order to obtain the specified mechanical properties for larger
diameters, but shall not exceed 0,12 % for austenitic steels.
j
Titanium and/or niobium may be included to improve corrosion resistance.
k
This formula is used solely for the purpose of classifying duplex steels in accordance with this document (it is not intended to be used as a selection
criterion for corrosion resistance).
For the choice of the appropriate stainless steel grade suitable for a specific application, see ISO 3506-6.
Examples of stainless steels in accordance with Table 2 are also given in ISO 3506-6.
7.2 Heat treatment for martensitic stainless steel nuts
Regular and high nuts of grades and property classes C1-70, C3-80 and C4-70, and thin nuts of grades
and property classes C1-035, C3-040 and C4-035 shall be quenched and tempered.
Regular and high nuts of grade and property class C1-110 and thin nuts of grade and property class C1-
055 shall be quenched and tempered, with a minimum tempering temperature of 275 °C.
8 © ISO 2020 – All rights reserved
ISO 3506-2:2020(E)
7.3 Finish
Unless otherwise specified, nuts in accordance with this document shall be supplied clean and bright.
For maximum corrosion resistance, passivation is recommended. Nuts that are passivated in accordance
with ISO 16048 may additionally be referenced on the label with the letter “P” immediately after the
property class symbol (see 11.4).
NOTE 1 Passivated nuts do not always show a bright surface finish.
Nuts are often used in bolted joints where the preload is achieved by torque tightening. Therefore,
lubrication of stainless steel nuts is strongly recommended in order to avoid galling during tightening.
NOTE 2 Several parameters can increase the risk of galling for stainless steel nuts in bolted assemblies during
tightening such as thread damage, high preload, high tightening speed.
NOTE 3 For the time being, requirements concerning surface discontinuities, torque/clamp force and
prevailing torque properties are not specified in International Standards for stainless steel fasteners.
A controlled torque/clamp force relationship can be obtained for stainless steel fasteners by means
of an adequate finish, either just with a lubricant or with a coating, top coat and/or sealer including
lubricant. In this case, the designation and/or labelling should include the letters “Lu” immediately
after the symbol of the property class, e.g. A4-80Lu. In conjunction, appropriate measures and means of
tightening should be selected in order to achieve the required preload.
When specific requirements are necessary, it shall be agreed between the supplier and the purchaser at
the time of the order.
7.4 Corrosion resistance
For corrosion resistance purpose, nuts should be mated with bolts, screws, studs and washers of the
same stainless steel grade (e.g. nuts A2 with bolts A2, etc.). Other combinations are possible (e.g. nuts
A4 with bolts D4), providing that:
— the component with the lowest corrosion resistance shall always be taken into account,
— the risk of galling should be considered, and
— it is strongly recommended that an experienced fastener metallurgist be consulted.
When using stainless steel fasteners with non-stainless steel parts in bolted joints, e.g. galvanized
steels, it is advised that the use of isolation components be considered in order to avoid galvanic
corrosion.
8 Mechanical and physical properties
When tested by the methods specified in Clause 10, the nuts of the specified stainless steel grade and
property class shall meet, at ambient temperature, the requirements for the proof load and for the
hardness specified in Tables 3 to 8, regardless of which tests are performed during manufacture or
final inspection.
Although a great number of stainless steel grades and property classes are specified in this document,
this does not mean that all combinations are appropriate due to the properties of the material in
conjunction with the fastener geometry. Nevertheless, some combinations of grades and property
classes may not be available on the market. For non-standard fasteners, it is recommended that a
fastener expert be consulted.
ISO 3506-2:2020(E)
Table 3 — Mechanical properties for nuts — Austenitic and duplex grades
Regular nuts and high nuts Thin nuts
(style 1 and style 2) (style 0)
Stainless steel Property class Stress under Property class Stress under
a b
grade designation proof load designation proof load
and symbol S and symbol S
p p
MPa MPa
50 500 025 250
A1 A2
70 700 035 350
A3
80 800 040 400
50 500 025 250
Austenitic 70 700 035 350
A4 A5
80 800 040 400
100 1 000 050 500
70 700 035 350
A8 80 800 040 400
100 1 000 050 500
70 700 035 350
D2 D4
Duplex 80 800 040 400
D6 D8
100 1 000 050 500
a
Proof load values for regular and high nuts (full loadability) are specified in Table 5 for coarse pitch thread, and in
Table 6 for fine pitch thread.
b
Proof load values for thin nuts (reduced loadability) are specified in Table 7 for coarse pitch thread, and in Table 8 for
fine pitch thread.
Table 4 — Mechanical properties for nuts — Martensitic and ferritic grades
Regular nuts and high nuts Thin nuts
All nuts
(style 1 and style 2) (style 0)
Stainless steel Property class Stress under Property class Stress under Hardness
a b
grade designation and proof load designation and proof load
min. to max.
symbol S symbol S
p p
MPa MPa HV HRC HBW
50 500 025 250 155 to 220 — 147 to 209
C1 70 700 035 350 220 to 330 20 to 34 209 to 314
c c
110 1 100 055 550 350 to 440 36 to 45 —
Martensitic
C3 80 800 040 400 240 to 340 21 to 35 228 to 323
50 500 025 250 155 to 220 — 147 to 209
C4
70 700 035 350 220 to 330 20 to 34 209 to 314
45 450 022 225 135 to 220 — 128 to 209
d
Ferritic F1
60 600 030 300 180 to 285 — 171 to 271
a
Proof load values for regular and high nuts (full loadability) are specified in Table 5 for coarse pitch thread, and in Table 6 for fine pitch thread.
b
Proof load values for thin nuts (reduced loadability) are specified in Table 7 for coarse pitch thread, and in Table 8 for fine pitch thread.
c
Hardened and tempered at a minimum tempering temperature of 275 °C.
d
Only for nominal thread diameters D ≤ 24 mm.
10 © ISO 2020 – All rights reserved
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