ISO/FDIS 3506-5

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

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

General Information

• Status: Published
• ICS: 21.060.99 - Other fasteners
• Technical Committee: ISO/TC 2 - Fasteners
• Drafting Committee: ISO/TC 2/WG 17 - Stainless steel fasteners
• Current Stage: 5000 - FDIS registered for formal approval
• Start Date: 27-May-2021

Standards Content (sample)

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 3506-5
ISO/TC 2
Fasteners — Mechanical properties
Secretariat: DIN
of corrosion-resistant stainless steel
Voting begins on:
2021-09-07 fasteners —
Voting terminates on:
Part 5:
2021-11-02
Special fasteners (also including
fasteners from nickel alloys) for high
temperature applications
Fixations — Caractéristiques mécaniques des fixations en acier
inoxydable résistant à la corrosion —
Partie 5: Fixations spéciales (incluant également les fixations en
alliages de nickel) pour utilisation à hautes températures
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 3506-5:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. ISO 2021
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ISO/FDIS 3506-5:2021(E)
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© ISO 2021

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ii © ISO 2021 – All rights reserved
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ISO/FDIS 3506-5:2021(E)
Contents Page

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

Introduction ................................................................................................................................................................................................................................vi

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

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

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

4 Symbols .......................................................................................................................................................................................................................... 4

5 Designation system for fasteners made from stainless steels and nickel alloys ...............................5

6 Materials and manufacture ....................................................................................................................................................................... 5

6.1 Chemical composition ...................................................................................................................................................................... 5

6.2 Heat treatment for fasteners ....................................................................................................................................................... 7

6.3 Finish ............................................................................................................................................................................................................... 8

6.4 Design of bolt/nut assemblies ................................................................................................................................................... 9

6.5 Service temperatures for fasteners ....................................................................................................................................10

7 Mechanical and physical properties .............................................................................................................................................10

7.1 Mechanical properties of bolts, screws and studs .................................................................................................10

7.2 Mechanical properties of nuts ................................................................................................................................................14

8 Applicability of test methods and inspection ......................................................................................................................15

8.1 Applicability of test methods ...................................................................................................................................................15

8.2 Manufacturer’s inspection .........................................................................................................................................................16

8.3 Supplier’s inspection ......................................................................................................................................................................16

8.4 Purchaser’s inspection ..................................................................................................................................................................16

8.5 Delivery of test results ...................................................................................................................................................................16

9 Test methods at ambient temperature .......................................................................................................................................17

9.1 Tensile test for bolts, screws and studs at ambient temperature ............................................................17

9.1.1 General...................................................................................................................................................................................17

9.1.2 Test procedure for the simultaneous determination of R , R , and A .........................19

mf pf
9.1.3 Reference test procedure for the determination of stress at 0,2 % non-

proportional elongation, R .................................................................................................................................

pf 20

9.1.4 Alternative test procedure for the determination of elongation, A ...................................21

9.1.5 Test results and requirements for tensile strength, R ................................................................

mf 22
9.1.6 Test results and requirements for stress at 0,2 % non-proportional

elongation, R ...................................................................................................................................................................

pf 23

9.1.7 Test results and requirements for elongation after fracture, A ............................................23

9.2 Hardness test for bolts, screws and studs ....................................................................................................................23

9.2.1 General...................................................................................................................................................................................23

9.2.2 Test procedure ................................................................................................................................................................23

9.2.3 Test results and requirements for hardness .........................................................................................24

9.3 Proof load test for nuts..................................................................................................................................................................24

9.3.1 General...................................................................................................................................................................................24

9.3.2 Test procedure ................................................................................................................................................................25

9.3.3 Additional testing procedure for prevailing torque nuts ...........................................................26

9.3.4 Test results and requirements for nut proof load ............................................................................27

9.4 Hardness test for nuts ....................................................................................................................................................................27

9.4.1 General...................................................................................................................................................................................27

9.4.2 Test procedure ................................................................................................................................................................27

9.4.3 Test results and requirements for nut hardness ...............................................................................28

10 Test methods at high temperature..................................................................................................................................................28

10.1 High temperature tensile test for bolts, screws, studs and nuts ...............................................................28

10.1.1 General...................................................................................................................................................................................28

10.1.2 Test apparatus .................................................................................................................................................................28

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ISO/FDIS 3506-5:2021(E)

10.1.3 Test procedure ................................................................................................................................................................29

10.1.4 Test report ..........................................................................................................................................................................30

10.2 High temperature stress rupture test for bolts, screws, studs and nuts ............................................31

10.2.1 General...................................................................................................................................................................................31

10.2.2 Test apparatus and testing device..................................................................................................................31

10.2.3 Test procedure ................................................................................................................................................................32

10.2.4 Test report ..........................................................................................................................................................................32

10.3 Relaxation test for bolts, screws, studs and nuts ....................................................................................................33

10.3.1 General...................................................................................................................................................................................33

10.3.2 Bolted joint models .....................................................................................................................................................33

10.3.3 Test apparatus and measuring devices .....................................................................................................34

10.3.4 Test procedure ................................................................................................................................................................34

10.3.5 Test results .........................................................................................................................................................................35

10.3.6 Test report ..........................................................................................................................................................................35

10.4 Creep test ..................................................................................................................................................................................................36

11 Fastener marking and labelling .........................................................................................................................................................36

11.1 General requirements for marking .....................................................................................................................................36

11.2 Manufacturer's identification mark ...................................................................................................................................37

11.3 Marking on the fasteners ............................................................................................................................................................37

11.3.1 Hexagon head bolts and screws and hexagon nuts .........................................................................37

11.3.2 Hexagon socket and hexalobular socket bolts and screws .......................................................38

11.3.3 Other types of bolts, screws and nuts .........................................................................................................38

11.3.4 Studs (one-end and double-end studs) .....................................................................................................38

11.3.5 Fully threaded studs ..................................................................................................................................................38

11.3.6 Left-hand thread marking .....................................................................................................................................39

11.4 Marking of the packages (labelling) ..................................................................................................................................39

Annex A (informative) Tempering of martensitic stainless steels ......................................................................................40

Bibliography .............................................................................................................................................................................................................................43

iv © ISO 2021 – All rights reserved
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ISO/FDIS 3506-5:2021(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.

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.
© ISO 2021 – All rights reserved v
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ISO/FDIS 3506-5:2021(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
— Part 4 : Tapping screws

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

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

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

specified in ISO 3506-6.

The properties of stainless steel and nickel alloy fasteners for high temperature applications result from

the chemical composition of the material, from the heat treatment process and from the manufacturing

process of the fasteners. Static or dynamic properties at room temperature like tensile strength,

hardness or fatigue resistance are not sufficient enough to design fasteners for high temperature

applications properly.

In fact, at high temperatures e.g. above 300 °C, additional phenomena occur, for instance:

— decrease in tensile properties and hardness,
— hot oxidation and scaling,
— stress relaxation,
— creep.

All these phenomena significantly affect the durability and service life of fasteners. Therefore:

— a proper choice of material grade is essential to avoid heavy hot oxidation,
— qualification of fasteners through dedicated tests should be performed.

Different tests are currently available to assess the behavior of machined and standardized samples

(see for example ASTM E292 or ASTM E328). In addition to these tests, this document specifies test

methods on finished fasteners: these are useful when requiring results as representative as possible of

the actual service conditions.

All fastener categories included in this document are heat-treated (see Clause 6). Heat treatment

processing is crucial to reach mechanical properties and suitable microstructure that are essential to

stand phenomena described above and to get adequate durability for the fasteners and the assembled

joint.

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.

vi © ISO 2021 – All rights reserved
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 3506-5:2021(E)
Fasteners — Mechanical properties of corrosion-resistant
stainless steel fasteners —
Part 5:
Special fasteners (also including fasteners from nickel
alloys) for high temperature applications
1 Scope

This document specifies the mechanical and physical properties of bolts, screws, studs and nuts, with

coarse pitch thread and fine pitch thread, made of corrosion-resistant stainless steels (i.e. martensitic

stainless steels and precipitation hardening austenitic stainless steels) and nickel alloys, intended for

use at high temperatures up to 800 °C.

Tests in accordance with Clause 9 are performed at the ambient temperature range of 10 °C to 35 °C,

and other tests can be performed at higher temperatures, see Clause 10.

NOTE Fasteners specified in this document are also suitable when used at low temperatures, typically down

to - 50 °C. For more information, see ISO 3506-6.

The term “fasteners” is used in this document when bolts, screws, studs and nuts are considered all

together.

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

nickel alloys as well as their properties.
This document applies to fasteners:
— 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 M3 to M39, and fine pitch thread M8×1 to M39×3,
— with thread tolerances in accordance with ISO 965-1 and ISO 965-2, and
— of any shape but with full loadability.

Stainless steel and nickel alloy fastener symbols can be used for sizes outside the diameter limits of this

document (i.e. for bolts, screws and studs with d < 3 mm or d > 39 mm and for nuts with D < 5 mm or

D > 39 mm), provided that all applicable chemical, mechanical and physical requirements are met.

Fasteners with reduced loadability (i.e. thin nuts and bolts, screws and studs with head or unthreaded

shank weaker than the threaded shank) are not dealt with in this document.
This document does not specify requirements for functional properties such as:
— torque/clamp force properties,
— shear strength,
— fatigue resistance,
— weldability,
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ISO/FDIS 3506-5:2021(E)

— properties of bolted joints and fasteners in high temperature environment (see test methods for

fasteners in Clause 10).
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

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

ISO 3506-1, Fasteners — Mechanical properties of corrosion-resistant stainless steel fasteners — Part 1:

Bolts, screws and studs with specified grades and property classes

ISO 3506-2, Fasteners — Mechanical properties of corrosion-resistant stainless steel fasteners — Part 2:

Nuts with specified grades and property classes

ISO 3506-6, 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 9513, Metallic materials — Calibration of extensometer systems used in uniaxial testing

ISO 16228, Fasteners — Types of inspection documents

EN 10319-2, Metallic materials — Tensile stress relaxation testing — Part 2: Procedure for bolted joint

models
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 https:// www .electropedia .org/
3.1
stainless steel

steel with at least 10,5 % (mass fraction) of chromium (Cr) and maximum 1,2 % (mass fraction) of

carbon (C)
[SOURCE: ISO 3506-1:2020, 3.5]
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ISO/FDIS 3506-5:2021(E)
3.2
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]
3.3
precipitation hardening austenitic stainless steel

austenitic stainless steel that can be hardened through precipitation of intermetallic phases from its

supersaturated metallic matrix
3.4
nickel alloy
alloy whose main constituent is nickel
3.5
soaking time

time that the entire part being heat-treated (throughout its cross-sections) remains at the specified set

temperature
3.6
stainless steel bolt and screw with full loadability

bolt and screw with head stronger than the threaded and unthreaded shanks (with unthreaded shank

diameter d ≈ d or d > d ) or screw threaded to the head, and fulfilling the minimum ultimate tensile

s 2 s 2
load
[SOURCE: ISO 3506-1:2020, 3.1 modified]
3.7
stainless steel stud with full loadability

stud with unthreaded shank diameter d ≈ d or d > d , and fulfilling the minimum ultimate tensile load

s 2 s 2
[SOURCE: ISO 3506-1:2020, 3.2 modified]
3.8
stainless steel or nickel alloy nut with full loadability

regular nut or high nut fulfilling the requirements for proof load and with minimum height m ≥ 0,80D

min
or m ≥ 0,73D
th,design,min

Note 1 to entry: Note to entry The limits for the minimum height m ≥ 0,80D (for standard nuts) or

min
m ≥ 0,73D (for other nuts) are explained in 6.4.
th,design,min
3.9
resistance to high temperature environment

extent to which a fastener retains required functional properties (e.g. resistance against oxidation,

relaxation, creep) during exposure to a specified temperature for a specified duration and/or to

temperature cycles
3.10
creep

time-dependent strain that occurs after the application of a force which is thereafter maintained

constant
3.11
relaxation
time-dependent stress loss for a constant strain
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ISO/FDIS 3506-5:2021(E)
4 Symbols
For the purposes of this document, the following symbols apply.
A Total elongation after fracture, mm
A Total elongation after fracture for full-size fastener at high temperature, mm
A Nominal stress area in thread, mm
s,nom
b Thread length, mm
d, D Nominal thread diameter, mm
d Basic minor diameter of external thread, mm
d Basic pitch diameter of external thread, mm
D Basic pitch diameter of internal thread, mm
d Minor diameter of external thread (for nominal stress area calculation), mm
d Hole diameter in tensile testing device, mm
d Diameter of unthreaded shank, mm
F Ultimate tensile load, N
F Ultimate tensile load at high temperature, N
mf,T
F Ultimate stripping load at high temperature for the nut, N
n,T
F Proof load for nut, N
F Load at 0,2 % non-proportional elongation for full-size fastener, N

F Load at 0,2 % non-proportional elongation for full-size fastener at high temperature, N

pf,T
h Thickness of the nut grip in tensile testing device, mm
H Height of the fundamental triangle of the thread, mm
l Nominal length of fastener, mm
L Total length of fastener before tensile test, mm
L Total length of fastener after fracture, mm
L Clamping length before tensile test, mm
l Overall length of stud, mm
l Free threaded length of fastener in testing device, mm
m Height of the nut, mm
m Design thread height of the nut, mm
th,design
P Pitch of the thread, mm
R Tensile strength for full-size fastener, MPa
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ISO/FDIS 3506-5:2021(E)
R Tensile strength for full-size fastener at high temperature, MPa
mf,T
R Ultimate nut strength at stripping load at high temperature, MPa
n,T
R Stress at 0,2 % non-proportional elongation for full-size fastener, MPa

R Stress at 0,2 % non-proportional elongation for full-size fastener at high temperature, MPa

pf,T
S Stress under proof load for nuts, MPa
5 Designation system for fasteners made from stainless steels and nickel alloys

All stainless steels and nickel alloys specified in this document belong to one of the three following

categories:
— martensitic stainless steels (3.2): CH0, CH1, CH2, V, VH, VW,
— precipitation hardening austenitic stainless steels (3.3): SD,
— nickel alloys (3.4): SB and 718.

The chemical composition and heat treatment of fasteners for these three material categories are

specified in Clause 6.
The marking, labelling and design
...