SIST EN ISO 898-2:2022

SLOVENSKI STANDARD
01-december-2022
Nadomešča:
SIST EN ISO 898-2:2012
Vezni elementi - Mehanske lastnosti veznih elementov, narejenih iz ogljikovega
jekla in jeklene zlitine - 2. del: Matice z določenimi razredi trdnosti (ISO 898-2:2022)
Fasteners - Mechanical properties of fasteners made of carbon steel and alloy steel -
Part 2: Nuts with specified property classes (ISO 898-2:2022)
Mechanische Verbindungselemente - Mechanische Eigenschaften von
Verbindungselementen aus Kohlenstoffstahl und legiertem Stahl - Teil 2: Muttern mit
festgelegten Festigkeitsklassen (ISO 898-2:2022)
Fixations - Caractéristiques mécaniques des fixations en acier au carbone et en acier
allié - Partie 2: Écrous de classes de qualité spécifiées (ISO 898-2:2022)
Ta slovenski standard je istoveten z: EN ISO 898-2:2022
ICS:
21.060.20 Matice Nuts
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 898-2
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2022
EUROPÄISCHE NORM
ICS 21.060.20 Supersedes EN ISO 898-2:2012
English Version
Fasteners - Mechanical properties of fasteners made of
carbon steel and alloy steel - Part 2: Nuts with specified
property classes (ISO 898-2:2022)
Fixations - Caractéristiques mécaniques des fixations Mechanische Verbindungselemente - Mechanische
en acier au carbone et en acier allié - Partie 2: Écrous Eigenschaften von Verbindungselementen aus
de classes de qualité spécifiées (ISO 898-2:2022) Kohlenstoffstahl und legiertem Stahl - Teil 2: Muttern
mit festgelegten Festigkeitsklassen (ISO 898-2:2022)
This European Standard was approved by CEN on 9 September 2022.

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

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

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 898-2:2022 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 898-2:2022) 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 April 2023, and conflicting national standards shall be
withdrawn at the latest by April 2023.
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 898-2:2012.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 898-2:2022 has been approved by CEN as EN ISO 898-2:2022 without any modification.

INTERNATIONAL ISO
STANDARD 898-2
Fourth edition
2022-09
Fasteners — Mechanical properties
of fasteners made of carbon steel and
alloy steel —
Part 2:
Nuts with specified property classes
Fixations — Caractéristiques mécaniques des fixations en acier au
carbone et en acier allié —
Partie 2: Écrous de classes de qualité spécifiées
Reference number
ISO 898-2:2022(E)
ISO 898-2:2022(E)
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 898-2:2022(E)
Contents Page
Foreword .v
Introduction .vii
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Symbols . 2
5 Designation systems .3
5.1 Nut styles . 3
5.2 Property classes . 3
5.2.1 Regular nuts (style 1) and high nuts (style 2) . 3
5.2.2 Thin nuts (style 0) . 4
6 Design of bolt and nut assemblies . 4
7 Material, heat treatment, chemical composition and steel microstructure .4
7.1 General . 4
7.2 Heat treatment. 5
7.3 Chemical composition . 5
7.4 Steel microstructure . 7
7.4.1 Non-quenched and tempered nuts . 7
7.4.2 Quenched and tempered nuts . 7
8 Mechanical and physical properties . 7
8.1 General . 7
8.2 Proof load . 8
8.3 Hardness . 9
8.4 Surface integrity . 11
9 Inspection .11
9.1 Manufacturer's inspection . 11
9.2 Supplier's inspection . 11
9.3 Purchaser's inspection . 11
9.4 Delivery of test results . 12
10 Test methods .12
10.1 Proof load test .12
10.1.1 General .12
10.1.2 Applicability .12
10.1.3 Apparatus . 12
10.1.4 Testing device .12
10.1.5 Test procedure. 13
10.1.6 Test results and requirements . 14
10.2 Hardness tests . 14
10.2.1 General . 14
10.2.2 Applicability . 14
10.2.3 Test methods . 14
10.2.4 Test procedures for routine inspection . 14
10.2.5 Hardness determined in the thread . 16
10.2.6 Hardness determined in the core . 17
10.2.7 Uniformity of hardness for quenched and tempered nuts (QT) . 18
10.2.8 Requirements for non-quenched and tempered nuts (NQT) . 18
10.2.9 Requirements for quenched and tempered nuts (QT) . 18
10.3 Steel microstructure . 19
10.3.1 General . 19
10.3.2 Applicability . 19
iii
ISO 898-2:2022(E)
10.3.3 Test method . 19
10.3.4 Test results and requirements . 19
10.4 Retempering test . 19
10.4.1 General . 19
10.4.2 Test procedure. 19
10.4.3 Test results and requirements . 20
10.5 Surface discontinuity inspection . 20
11 Marking and labelling .20
11.1 General requirements . 20
11.2 Property class marking symbols for nuts with full loadability . 20
11.3 Property class marking symbols for nuts with reduced loadability . 21
11.4 Manufacturer’s identification mark. 21
11.5 Nut marking . 21
11.6 Marking of the packages (labelling) . 23
Annex A (normative) Thread dimensions of the test mandrel .25
Annex B (informative) Design principles for nuts.27
Annex C (informative) Stress under proof load, S .29
P
Bibliography .31
iv
ISO 898-2:2022(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, Subcommittee SC 12,
Fasteners with metric internal thread, in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 185, Fasteners, in accordance with the Agreement on technical
cooperation between ISO and CEN (Vienna Agreement).
This fourth edition cancels and replaces the third edition (ISO 898-2:2012) which has been technically
revised.
The main changes are as follows:
— property class 9 has been deleted completely, and nuts with fine pitch thread and property class 5
have been deleted (see Introduction);
— nuts with fine pitch thread in style 2 and property class 12 have been added for diameters 18 mm to
39 mm (see Tables 4, 6 and 10);
— styles have been more precisely specified for standard hexagon nuts according to their minimum
height, and styles have been specified for other nuts according to their minimum design thread
height (see 5.1);
— additional statements for thin nuts and jam nuts have been added (see Clause 6);
— additional statements for hot dip galvanized nuts have been added by referencing ISO 10684;
— in relation to material, heat treatment and steel microstructure (see Clause 7):
— the minimum carbon content has been added (see Tables 3 and 4),
— the minimum manganese content has been specified to 0,25 % for all Non-Quenched and
Tempered nuts (NQT) and has been raised to 0,45 % for all Quenched and Tempered nuts (QT)
(see Tables 3 and 4),
— the table footnote for free cutting steel has been reworked (see Tables 3 and 4),
v
ISO 898-2:2022(E)
— the minimum tempering temperature has been added for QT nuts (see Tables 3 and 4), and a
reference retempering test has been added (see 10.4),
— for nuts that may optionally be quenched and tempered at the manufacturer’s discretion,
detailed specifications have been added (see 7.2),
— specifications for steel microstructure have been added for NQT and QT nuts (see 7.4.1, 7.4.2
and 10.3);
— in relation to proof load:
— the proof load values for nuts with coarse pitch thread and property classes 6 and 8 have been
raised for sizes M27 to M39 (see Introduction, Table 5, and Annex C),
— the maximum hole diameter for the grip has been corrected for diameters 5 mm and 6 mm (see
Table 11), and reference to additional proof load specifications has been added for prevailing
torque nuts (see 10.1);
— in relation to hardness:
— the reference Vickers hardness values have been recalculated, and conversion into Brinell and
Rockwell hardness has been adjusted (see Introduction and 8.3),
— hardness determined on the bearing surface (see 10.2.4 a) and hardness determined in the
transverse section at mid-height of the nut (see 10.2.4 b) have been added for routine inspection,
— the test method for hardness determined in the thread has been improved and the test force has
been specified according to the pitch dimension (see 10.2.5),
— for QT nuts, the test methods for hardness in the core (see 10.2.6) and uniformity of hardness
(see 10.2.7) have been added,
— requirements for hardness have been clarified (see 10.2.8 and 10.2.9);
— inspection documents have been referenced in accordance with ISO 16228 for fasteners (see 9.4);
— marking and labelling have been revised, and all nuts conforming to this document are to be marked
whatever their shape (see Clause 11);
— Annex B, Design principles for nuts, has been improved;
— Annex C, Nominal stress under proof load, has been added.
A list of all parts in the ISO 898 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 898-2:2022(E)
Introduction
ISO 898, the basic standard for fasteners with ISO metric thread made of carbon steel and alloy steel,
was developed in several parts, and includes diameters 5 mm to 39 mm only for nuts. Property classes
are specified in the ISO 898 series in relation to materials and mechanical properties, so that nuts in
accordance with ISO 898-2 are matching with bolts, screws and studs specified in ISO 898-1 and with
flat washers specified in ISO 898-3, as necessary, in order to design suitable assemblies for a given
application.
More parts are under development for bolts, screws, studs and nuts with sizes above 39 mm.
The nuts specified in this document result from the adequate combination of nut heights (regular,
style 1 – high, style 2 – thin, style 0), diameter ranges, coarse or fine pitch thread, and property classes
in relation to heat treatment (Non-Quenched and Tempered = NQT, or Quenched and Tempered = QT).
These combinations are based on bolt/nut compatibility, manufacturing processes and market needs.
If other combinations are needed, e.g. for nuts designed for particular applications, see ISO/TR 16224.
In order to assure the necessary material strength in relation to property classes:
— Quenched and Tempered nuts (QT) are specified with a minimum carbon content and a minimum
tempering temperature, and are characterized by a homogeneous martensitic structure;
— Non-Quenched and Tempered nuts (NQT) are also specified with a minimum carbon content but are
characterized by a non-quenched microstructure.
Some property classes (in relation to nut style, diameter and coarse or fine pitch thread) specified as
NQT may be optionally quenched and tempered as specified in 7.2, and in this case all requirements for
QT nuts apply.
For fully loadable non-standard nuts which are to meet the requirements of this document, the relevant
style 1 or style 2 is assigned in relation to their minimum design thread height.
Nut loadability is primarily checked by proof load. For nuts with coarse pitch thread and property
classes 6 and 8, proof load values have been raised for sizes M27 to M39 due to the latest calculations of
[20] [21]
Masaya Hagiwara in accordance with the Alexander's theory , see ISO/TR 16224. For those nuts
it was necessary to develop full strength in relation to the mating bolts, screws and studs specified in
ISO 898-1, the difference between the proof loads of ISO 898-2:2012 and the recalculated values being
more than 5 % (see Annex C).
The Vickers hardness values specified for each individual group (consisting of property class, style,
diameter range and pitch) have been chosen according to the same latest calculations, but adjusted to
conventional figures taken over from the former versions of Parts 2 and 6 which were merged in 2012.
ISO 18265 presents no hardness to tensile strength correlation for steel in work hardened condition,
which is typical for cold forged high volume NQT nuts: therefore, minimum hardness is just informative
for NQT nuts and does not constitute a criterion in case of dispute. The maximum hardness of 334 HV is
specified in order to prevent unexpected manufacturing processes which can lead to brittle behaviour
of the NQT nuts: this limit is therefore mandatory and valid in case of dispute. However, it should be
noted that work hardening is usually not severe enough to reach 302 HV when typical material and
forging processes are used; nevertheless, inappropriate hardness testing or scattering due to just local
properties is also covered by this specified limit of 334 HV.
Due to missing or decreasing market needs, nuts of property class 5 with fine pitch thread in style 1
and nuts of property class 9 were deleted (property class 5 or 9 can be substituted by property class 6
or 10 respectively).
vii
INTERNATIONAL STANDARD ISO 898-2:2022(E)
Fasteners — Mechanical properties of fasteners made of
carbon steel and alloy steel —
Part 2:
Nuts with specified property classes
1 Scope
This document specifies the mechanical and physical properties of nuts made of non-alloy steel or alloy
steel, when tested at the ambient temperature range of 10 °C to 35 °C.
This document applies to nuts:
— with ISO metric thread (see ISO 68-1),
— with diameter/pitch combinations according to ISO 261 and ISO 262,
— with coarse pitch thread M5 to M39, and fine pitch thread M8×1 to M39×3,
— with thread tolerances according to ISO 965-1, ISO 965-2 or ISO 965-5,
— with specified property classes 04, 05, 5, 6, 8, 10 and 12 including proof load,
— of three different nut styles (see 5.1): regular nuts (style 1), high nuts (style 2) and thin nuts (style 0),
— with a minimum outside diameter or width across flats s ≥ 1,45D,
— able to mate with bolts, screws and studs with property classes in accordance with ISO 898-1 (see
Annex B), and
— intended to be used in applications ranging from –50 °C to +150 °C, or up to +300 °C.
WARNING — Nuts conforming to the requirements of this document are tested at the ambient
temperature range of 10 °C to 35 °C and are used in applications ranging from –50 °C to +150 °C;
however, these nuts are also used outside this range and up to +300 °C for specific applications.
It is possible that they do not retain the specified mechanical and physical properties at lower
and/or elevated temperatures. Therefore, it is the responsibility of the user to determine the
appropriate choices based on the service environment conditions of the assembly (see also 7.1).
For additional specifications applicable to hot dip galvanized nuts, see ISO 10684.
For nuts designed for particular applications, see ISO/TR 16224.
This document does not specify requirements for functional properties such as:
— prevailing torque properties (see ISO 2320),
— torque/clamp force properties (see ISO 16047 for test method),
— weldability, or
— corrosion resistance.
ISO 898-2:2022(E)
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1891-4, Fasteners — Vocabulary — Part 4: Control, inspection, delivery, acceptance and quality
ISO 2320, Fasteners — Prevailing torque steel nuts — Functional properties
ISO 6157-2, Fasteners — Surface discontinuities — Part 2: Nuts
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 10684, Fasteners — Hot dip galvanized coatings
ISO 16228, Fasteners — Types of inspection documents
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Symbols
D nominal thread diameter of the nut (basic major diameter of the internal thread), mm
d hole diameter of the grip, mm
h
F force, N
F proof load, N
P
h thickness of the grip, mm
m height of the nut, mm
m design thread height of the nut, mm
th,design
P pitch of the thread, mm
s width across flats, mm
S stress under proof load, MPa
P
ISO 898-2:2022(E)
5 Designation systems
5.1 Nut styles
This document specifies three styles for nuts.
For standard hexagon nuts without flange and without prevailing torque feature, the following limits
apply:
— style 1: regular nut with minimum height 0,80D ≤ m < 0,89D, see Table B.1;
min
— style 2: high nut with minimum height m ≥ 0,89D, see Table B.1;
min
— style 0: thin nut with minimum height 0,45D ≤ m < 0,80D.
min
For other standard nuts (e.g. nuts with flange, prevailing torque nuts, non-hexagon nuts, etc.), the style
shall be addressed in the product standard together with the mechanical properties.
For nuts per drawing, the style shall be addressed in accordance with the minimum design thread
height, m , together with the mechanical properties. m is specified in Figure 1 and Table 1.
th,design th,design
m is the distance between the intersections of the nut chamfer(s) if any or the nut face(s), with
th,design
the theoretical cylinder representing the nominal thread diameter D.
Figure 1 — Design thread height, m
th,design
Table 1 — Design thread height for nuts per drawing
Regular nuts (style 1) High nuts (style 2) Thin nuts (style 0)
0,73D ≤ m < 0,83D m ≥ 0,83D 0,40D ≤ m < 0,73D
th,design,min th,design,min th,design,min
NOTE 1 Limits for m are calculated by taking into account the most critical dimensions for the nuts, i.e. minimum
th,design,min
height m , maximum diameter of the countersink d , minimum countersink angle for the chamfer (90° for regular and
min a,max
high nuts, 110° for thin nuts) and two chamfers (one on each bearing face).
NOTE 2 The resulting minimum ratios for standard hexagon nuts with diameters 12 mm to 39 mm are the basis for the
figures specified in this Table.
5.2 Property classes
5.2.1 Regular nuts (style 1) and high nuts (style 2)
The property classes of regular nuts (style 1) and high nuts (style 2) consist of a number. This number
corresponds to the left number of the appropriate highest property class of bolts, screws and studs
with which they can be mated, which is 1/100 of the nominal tensile strength of the mating bolt in
megapascals.
EXAMPLE Nut with property class 10 is a regular or high nut to be mated with a bolt of property class up to
10.9 included.
ISO 898-2:2022(E)
5.2.2 Thin nuts (style 0)
The property classes of thin nuts (style 0) consist of two digits, specified in the following way:
a) the first digit "zero" indicates the reduced loadability of thin nuts, in order to warn that these nuts
are not designed to prevent thread stripping failure mode in case of overloading;
b) the second digit corresponds to approximately 1/100 of the nominal stress under proof load, S , in
P
megapascals (MPa).
EXAMPLE Nut with property class 05 is a thin nut with a nominal stress under proof load of 500 MPa.
6 Design of bolt and nut assemblies
Explanations of basic design principles of nuts and loadability of bolted assemblies are given in Annex B.
Information for nominal stress under proof load S is given in Annex C.
P
Regular nuts (style 1) and high nuts (style 2) shall be mated with externally threaded fasteners in
accordance with Table 2. However, nuts of a higher property class may replace nuts of a lower property
class, except for prevailing torque nuts where only nuts and externally threaded fasteners with
corresponding property classes shall be combined.
Table 2 — Combination of regular nuts (style 1) and high nuts (style 2)
with bolt, screw, stud property classes
Highest property class
Nut property class
of mating bolt, screw and stud
5 5.8
6 6.8
8 8.8
10 10.9
12 12.9/12.9
Thin nuts (style 0) have a reduced loadability compared to regular nuts or high nuts and are not
designed to prevent thread stripping failure mode in case of overloading.
Thin nuts used as jam nuts shall be assembled together with a regular nut or a high nut (thin nuts of
property class 04 with regular or high nuts up to and including property class 8, thin nuts of property
class 05 with regular or high nuts of property class up to and including 12).
7 Material, heat treatment, chemical composition and steel microstructure
7.1 General
When tested at ambient temperature by the methods specified in Clause 10, nuts with specified property
class shall meet the requirements specified in Clause 7, regardless of which tests are performed during
manufacture or final inspection.
When nuts are intended to be used in applications outside the range of –50 °C to +150 °C, several
factors need to be taken into account, e.g. steel composition, duration of exposure at low or elevated
temperature, the effect of the temperature on the fastener mechanical properties and clamped parts.
NOTE Information for the selection and application of steels for use at lower and elevated temperatures is
given for instance in EN 10269, ASTM A320/A320M and ASTM A194/A194M.
The chemical composition limits of steels, the heat treatment condition (including minimum tempering
temperature for quenched and tempered nuts only) and microstructure for the specified combinations
ISO 898-2:2022(E)
of property classes, heights (styles) and thread diameters shall be in accordance with Table 3 for nuts
with coarse pitch thread, and with Table 4 for nuts with fine pitch thread.
7.2 Heat treatment
Nuts shall be manufactured in accordance with the requirements specified in Tables 3 and 4 for the
following heat treatment conditions:
— Not Quenched and Tempered (NQT),
— Quenched and Tempered (QT).
Only the following nuts are allowed to be manufactured in one or the other condition (NQT or QT) at
the manufacturer's discretion, and in both cases these nuts shall meet all applicable requirements for
the relevant heat treatment condition:
a) For nuts with coarse pitch thread and in accordance with Table 3:
— regular nuts (style 1) of property class 8 with D ≤ M16,
— high nuts (style 2) of property class 8;
b) For nuts with fine pitch thread and in accordance with Table 4:
— regular nuts (style 1) of property class 6 with D ≤ 16 mm,
— high nuts (style 2) of property class 8 with D ≤ 16 mm.
7.3 Chemical composition
The chemical composition shall be assessed in accordance with the relevant International Standards. In
case of dispute, the product analysis shall meet the limits specified in Table 3 or 4.
For nuts that are to be hot dip galvanized, the additional requirements specified in ISO 10684 shall
apply.
ISO 898-2:2022(E)
Table 3 — Chemical composition limits of steels for nuts with coarse pitch thread
a,b
Cast analysis Tempering
% temperature
Heat Property Nut Thread
treatment class height D C Mn P S °C
min. max. min. max. max. min.
d
04 Style 0 M5 ≤ D ≤ M39
Not
d
5 Style 1 M5 ≤ D ≤ M39
Quenched
d
and 6 Style 1 M5 ≤ D ≤ M39 0,06 0,58 0,25 0,060 0,150 —
Tempered
e
Style 1 M5 ≤ D ≤ M16
c
(NQT)
e
Style 2 M5 ≤ D ≤ M39
05 Style 0 M5 ≤ D ≤ M39
Style 1 M5 ≤ D ≤ M39
Quenched
Style 2 M5 ≤ D ≤ M39 0,15 380
and
Style 1 M5 ≤ D ≤ M39 0,58 0,45 0,048 0,058
Tempered
f
Style 2 M5 ≤ D ≤ M39
(QT)
Style 1 M5 ≤ D ≤ M16 0,18 410
Style 2 M5 ≤ D ≤ M39 0,15 380
a
In case of dispute, product analysis shall apply.
b
Alloying elements may be added, provided the mechanical and physical properties required in Clause 8 are met.
c
The steel structure of NQT nuts shall not consist of quenched microstructure, in accordance with 7.4.1.
d
These nuts may be manufactured from free cutting steel containing sulfur, phosphorus and lead, with the following
contents: S ≤ 0,350 %; P ≤ 0,110 %; Pb ≤ 0,350 %.
e
These nuts may be quenched and tempered at the manufacturer's discretion, and in this case all requirements for QT
nuts shall apply.
f
The microstructure of QT nuts shall show approximately 90 % martensite in accordance with 7.4.2.
ISO 898-2:2022(E)
Table 4 — Chemical composition limits of steels for nuts with fine pitch thread
a,b
Cast analysis  Tempering
% temperature
Heat Property Nut Thread
treatment class height D C Mn P S °C
min. max. min. max. max. min.
d
Not 04 Style 0 8 mm ≤ D ≤ 39 mm
Quenched
d e
6 Style 1 8 mm ≤ D ≤ 16 mm
and 0,06 0,58 0,25 0,060 0,150 —
Tempered
e
8 Style 2 8 mm ≤ D ≤ 16 mm
c
(NQT)
05 Style 0 8 mm ≤ D ≤ 39 mm
6 Style 1 8 mm ≤ D ≤ 39 mm 0,15 380
Style 1 8 mm ≤ D ≤ 16 mm
Quenched
8 Style 1 16 mm < D ≤ 39 mm 0,18 410
and
0,58 0,45 0,048 0,058
Tempered
Style 2 8 mm ≤ D ≤ 39 mm
f
(QT)
Style 1 8 mm ≤ D ≤ 16 mm 0,15 380
Style 2 8 mm ≤ D ≤ 39 mm
12 Style 2 8 mm ≤ D ≤ 39 mm 0,18 410
a
In case of dispute, product analysis applies.
b
Alloying elements may be added, provided the mechanical and physical properties required in Clause 8 are met.
c
The steel structure of NQT nuts shall not consist of quenched microstructure, in accordance with 7.4.1.
d
These nuts may be manufactured from free cutting steel containing sulfur, phosphorus and lead, with the following
contents: S ≤ 0,350 %; P ≤ 0,110 %; Pb ≤ 0,350 %.
e
These nuts may be quenched and tempered at the manufacturer's discretion, and in this case all requirements for QT
nuts shall apply.
f
The microstructure of QT nuts shall show approximately 90 % martensite in accordance with 7.4.2.
7.4 Steel microstructure
7.4.1 Non-quenched and tempered nuts
Nuts that are non-quenched and tempered (NQT) shall be supplied in the as forged or machined
condition. The steel structure shall not consist of quenched microstructure.
7.4.2 Quenched and tempered nuts
For materials of nuts to be quenched and tempered (QT), there shall be a sufficient hardenability to
ensure a homogenous microstructure consisting of approximately 90 % martensite throughout the
nuts.
The manufacturer shall ensure that the austenite transformation temperature has been exceeded
and sufficient duration allowed to achieve adequate transformation to martensite throughout the nut
during quenching to ensure uniform mechanical properties.
8 Mechanical and physical properties
8.1 General
When tested at ambient temperature by the methods specified in Clause 10, nuts with specified
property class shall meet the mechanical and physical requirements specified in Clause 8, regardless of
which tests are performed during manufacture or final inspection.
ISO 898-2:2022(E)
8.2 Proof load
When tested in accordance with 10.1, nuts with specified property class shall meet the requirements
for the proof load specified in Table 5 or 6.
Table 5 — Proof loads for nuts with coarse pitch thread
Proof load, F (N)
P
Thread Pitch
Property class
D P
a a
04 05 5 6 8 10 12
M5 0,8 5 40
...