Mechanical properties of fasteners -Stainless steel bolts, screws and studs
1 Scope
This document specifies the mechanical and physical properties of bolts, screws and studs (hereinafter referred to as “fasteners”), with coarse pitch thread and fine pitch thread, made of corrosion-resistant stainless steels, when tested at the ambient temperature range of 10℃ to 35℃. It specifies property classes in relation to austenitic, martensitic, ferritic and duplex (austenitic-ferritic) stainless steel grades for fasteners.
GB/T 3098.25 provides general rules and additional technical information on suitable stainless steels and their properties.
Fasteners conforming to the requirements of this document are tested at the ambient temperature range of 10℃ to 35℃. 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℃ to +150℃; however, fasteners conforming to this document are also used for applications outside this range down to -196℃ and up to +300℃. For more details, see Annex A and GB/T 3098.25.
Outside the temperature range of -20℃ to +150℃, 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 fasteners mechanical properties and clamped parts, and the corrosive service environment of the bolted joint.
Note 2: GB/T 3098.24 gives the selection of appropriate stainless steel grades and property classes intended for use at temperatures up to +800℃.
This document applies to fasteners:
——with general purpose metric screw threads in accordance with GB/T 192;
——with diameter/pitch combinations in accordance with GB/T 193 and GB/T 9144;
——with coarse pitch thread M1.6 to M39, and fine pitch thread M8×1 to M39×3;
——with thread tolerances in accordance with GB/T 197 and GB/T 9145;
——with specified property classes;
——of any shape.
Stainless steel grades and property classes may be used for sizes outside the diameter limits of this document (i.e. for d<1.6mm or d>39mm), provided that all applicable chemical, mechanical and physical requirements are met.
Certain bolts, screws and studs might not fulfill the tensile or torsional requirements of this document because of the geometry of their head or unthreaded shank, thus resulting in reduced loadability (e.g. when shear area in the head is less than the stress section area in the thread; see 8.2.2).
This document does not apply to set screws and similar threaded fasteners not under tensile stress (see GB/T 3098.16).
It does not specify requirements for properties such as:
——torque/clamp force properties;
——shear strength;
——fatigue resistance;
——weldability.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions 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.
GB/T 228.1 Metallic materials - Tensile testing - Part 1: Method of test at room temperature (GB/T 228.1-2021, ISO 6892-1:2019, MOD)
GB/T 230.1 Metallic materials - Rockwell hardness test - Part 1: Test method (GB/T 230.1-2018, ISO 6508-1:2016, MOD)
GB/T 231.1 Metallic materials - Brinell hardness test - Part 1: Test method (GB/T 231.1-2018, ISO 6506-1:2014, MOD)
GB/T 3098.25 Mechanical properties of fasteners - Guidance for the selection of stainless steels and nickel alloys for fasteners
GB/T 3099.4 Terminology of fasteners - Control, inspection, delivery, acceptance and quality (GB/T 3099.4-2021, ISO 1891-4:2018, MOD)
GB/T 4340.1 Metallic materials - Vickers hardness test - Part 1: Test method (GB/T 4340.1-2009, ISO 6507-1:2005, MOD)
GB/T 12160 Metallic materials - Calibration of extensometers systems used in uniaxial testing (GB/T 12160-2019, ISO 9513:2012, IDT)
GB/T 16825.1 Metallic materials - Calibration and verification of static uniaxial testing machines - Part 1: Tension/compression testing machines - Calibration and verification of the force-measuring system (GB/T 16825.1-2022, ISO 7500-1:2018, IDT)
GB/T 39310 Fasteners - Types of inspection documents (GB/T 39310-2020, ISO 16228:2017, MOD)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
stainless steel bolt and screw with full loadability
stainless steel bolt and screw with head stronger than the threaded and unthreaded shanks (with ds≈d2 or ds>d2) or screw threaded to the head, and fulfilling the minimum tensile load
[Source: GB/T 3098.24-2020, 3.6, modified]
3.2
stainless steel stud with full loadability
stainless steel stud with unthreaded shank diameter ds≈d2 or ds>d2, and fulfilling the minimum tensile load
[Source: GB/T 3098.24-2020, 3.7, modified]
3.3
stainless steel bolt and screw with reduced loadability
stainless steel bolt and screw with head weaker than the threaded and unthreaded shanks, or with an unthreaded shank diameter ds
Foreword II
Introduction VII
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols
5 Designation system for stainless steel grades and property classes
5.1 General
5.2 Designation of stainless steel grades (first block)
5.3 Designation of property classes (second block)
6 Materials
6.1 Chemical composition
6.2 Heat treatment for martensitic stainless steel fasteners
6.3 Finish
6.4 Corrosion resistance
7 Mechanical and physical properties
8 Applicability of test methods and inspection
8.1 Applicability of test methods
8.2 Loadability of fasteners
8.3 Manufacturer's inspection
8.4 Supplier’s inspection
8.5 Purchaser’s inspection
8.6 Delivery of test results
9 Test methods
9.1 Tensile test
9.2 Tensile test for bolts and screws with reduced loadability due to head design
9.3 Tensile test for bolts, screws and studs with reduced loadability due to shank design
9.4 Wedge tensile test
9.5 Torsional test
9.6 Hardness test
10 Fastener marking and labelling
10.1 Marking
10.2 Manufacturer's identification mark
10.3 Marking on the fasteners
10.4 Marking of the packages (labelling)
Annex A (Informative) Mechanical properties at elevated temperatures - Application at low temperatures
Bibliography
