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GB/T 3098.2-2025: Mechanical properties of fasteners - Part 2: Nuts
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GB/T 3098.2-2025: Mechanical properties of fasteners - Part 2: Nuts

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ICS 21.060.20 CCSJ13 National Standards of the People's Republic of China Replaces GB/T 3098.2-2015 Fastener Mechanical Properties Part 2.Nuts Published on 2025-10-31 Implemented on February 1, 2026 State Administration for Market Regulation The State Administration for Standardization issued a statement.

Table of contents

Preface III Introduction VI 1.Scope 1 2 Normative References 1 3.Terms and Definitions 2 4 Symbols 2 5.Marking System 2 6.Design of Bolt and Nut Connection Pairs 3 7.Materials, heat treatment, chemical composition, and metallographic structure 4 8 Mechanical and physical properties 6 9.Check 10 10 Test Methods 10 11.Signs and Labels 17 Appendix A (Normative) Mandrel Thread Dimensions for Bearing Load Test 21 Appendix B (Informative) Nut Design Guidelines 23 Appendix C (Informative) Guarantee Stress SP 25 References 27

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1.Structure and Drafting Rules of Standardization Documents". Drafting. This document is Part 2 of GB/T 3098 "Mechanical Properties of Fasteners". GB/T 3098 has already published the following parts. ---GB/T 3098.1 Mechanical properties of fasteners. bolts, screws and studs; ---GB/T 3098.2 Mechanical properties of fasteners – Part 2.Nuts; ---GB/T 3098.3 Mechanical properties of fasteners - Set screws; ---GB/T 3098.5 Mechanical properties of fasteners—Part 5.Self-tapping screws; ---GB/T 3098.6 Mechanical properties of fasteners - Stainless steel bolts, screws and studs; ---GB/T 3098.7 Mechanical Properties of Fasteners - Self-Extruding Screws; ---GB/T 3098.8 Mechanical properties of fasteners - Bolted connections for use at -200℃~700℃; ---GB/T 3098.9 Mechanical Properties of Fasteners - Effective Torque Type Steel Locknuts; ---GB/T 3098.10 Mechanical properties of fasteners – Bolts, screws, studs and nuts made of non-ferrous metals; ---GB/T 3098.11 Mechanical Properties of Fasteners - Self-Drilling and Self-Tapping Screws; ---GB/T 3098.12 Mechanical properties of fasteners - Tapered proof load test for nuts; ---GB/T 3098.13 Mechanical properties of fasteners - Torque test and breaking torque of bolts and screws (nominal diameter 1-10 mm); ---GB/T 3098.14 Mechanical properties of fasteners - Nut hole expansion test; ---GB/T 3098.15 Mechanical Properties of Fasteners - Stainless Steel Nuts; ---GB/T 3098.16 Mechanical properties of fasteners - Stainless steel set screws; ---GB/T 3098.17 Preload test for hydrogen embrittlement of fasteners—parallel bearing surface method; ---GB/T 3098.18 Test methods for mechanical properties of fasteners, specifically blind rivets; ---GB/T 3098.19 Mechanical Properties of Fasteners - Blind Rivets; ---GB/T 3098.20 Mechanical properties of fasteners - Guaranteed torque for wing nuts; ---GB/T 3098.21 Mechanical Properties of Fasteners - Stainless Steel Self-Tapping Screws; ---GB/T 3098.22 Mechanical properties of fasteners - Fine-grained non-quenched and tempered steel bolts, screws and studs; ---GB/T 3098.23 Mechanical properties of fasteners M42~M72 bolts, screws and studs; ---GB/T 3098.24 Mechanical properties of fasteners - Stainless steel and nickel alloy bolts, screws, studs and nuts for high temperature applications; ---GB/T 3098.25 Mechanical Properties of Fasteners - Guidelines for the Selection of Stainless Steel and Nickel Alloy Fasteners; ---GB/T 3098.26 Mechanical properties of fasteners - flat washers. This document replaces GB/T 3098.2-2015 "Mechanical Properties of Fasteners and Nuts". Compared with GB/T 3098.2-2015, except for structural adjustments... Aside from integration and editorial changes, the main technical changes are as follows. a) Fine-pitch threads and Grade 5 nuts have been removed (see Table 1,.2015 edition); b) Two types of fine threads, performance grade 12, and nominal diameter 18mm≤D≤39mm have been added (see Tables 4, 6 and 10); c) The minimum height range for three standard hexagonal nuts has been changed, and other nuts have been added based on the minimum thread design height specification. Requirements (see 5.1,.2015 edition 4.1); d) Added descriptions of the condition of thin nuts and lock nuts (see Chapter 6); e) Additional requirements for hot-dip galvanized nuts have been added according to GB/T 5267.3 (see Chapters 7, 8 and 11); f) Regarding materials, heat treatment, and metallographic structure (see Chapter 7). ---Added minimum carbon content requirements for materials (see Tables 3 and 4, Table 3 in the.2015 edition); ---For unquenched and tempered nuts (NQT), the minimum manganese content is specified as 0.25%; for quenched and tempered nuts (QT), the minimum manganese content is specified as... The minimum manganese content is set at 0.45% (see Tables 3 and 4); ---The notes for free-cutting steel have been revised (see notes d in Table 3 and d in Table 4, and note b in Table 3 of the.2015 edition); ---The minimum tempering temperature for quenched and tempered nuts (QT) has been increased (see Tables 3 and 4), and a re-tempering test has been added (see 10.4); ---Added a manufacturer-selectable quenched and tempered nut (QT) specification (see 7.2); ---Added metallographic specifications for non-quenched and tempered nuts (NQT) and quenched and tempered nuts (QT) (see 7.4.1, 7.4.2). and 10.3); g) Regarding the guaranteed load. ---Changed the guaranteed load values for coarse threads, performance grades 6 and 8, and thread sizes M27~M39 (see Table 5,.2015 edition). Table 4); ---The diameters of the 5mm and 6mm fixture holes have been changed (see Table 11, Table 8 in the.2015 edition); ---Add a load guarantee specification for effective torque type locknuts (see 10.1); h) Regarding hardness. ---The Vickers arbitration hardness, Brinell hardness, and Rockwell hardness values have been changed (see 8.3, Tables 6 and 7 of the.2015 edition); ---The determination of hardness at the bearing surface and half-nut height cross-section has been added as a routine inspection method [see 10.2.4a] and 10.2.4b)]; ---The method for determining hardness at threaded joints has been revised, stipulating that the hardness test load is determined based on the thread pitch (see 10.2.5,.2015 edition). 9.2.3.3); ---Added test methods for the core hardness and hardness consistency of quenched and tempered nuts (QT) (see 10.2.6 and). 10.2.7); ---Hardness requirements have been changed (see 10.2.8 and 10.2.9,.2015 versions 9.2.4.1 and 9.2.4.2); i) A fastener inspection document has been added according to GB/T 39310 (see 9.4); j) The marking and labeling have been changed to require that any nut conforming to this document be marked (see Chapter 11, Chapter 10 of the.2015 edition). This document modifies and adopts ISO 898-2.2022 "Fasteners - Mechanical properties of fasteners made of carbon steel and alloy steel - Part 2.Specifications". Nuts of performance grade. The technical differences between this document and ISO 898-2.2022, and the reasons therefor, are as follows. ---ISO 16228 has been replaced with the normatively referenced GB/T 39310 to adapt to my country's technical requirements (see 9.4); ---ISO 7500-1 has been replaced with the normatively referenced GB/T 16825.1 to adapt to my country's technical requirements (see 10.1.3); ---ISO 6892-1 has been replaced with the normatively referenced GB/T 228.1 to adapt to my country's technical requirements (see 10.1.5); ---ISO 2320 has been replaced with the normatively referenced GB/T 3098.9 to adapt to my country's technical requirements (see 10.1.1); ---ISO 6507-1 has been replaced with the normatively referenced GB/T 4340.1 to adapt to my country's technical requirements (see 10.2.3); ---ISO 6506-1 has been replaced with the normatively referenced GB/T 231.1 to adapt to my country's technical requirements (see 10.2.3); ---ISO 6508-1 has been replaced with the normatively referenced GB/T 230.1 to adapt to my country's technical requirements (see 10.2.3); ---ISO 1891-4 has been replaced with the normatively referenced GB/T 3099.4 to adapt to my country's technical conditions (see 11.6); ---ISO 10684 has been replaced with the normatively referenced GB/T 5267.3 to adapt to my country's technical requirements (see 7.3 and 8.2); ---ISO 6157-2 has been replaced with the normatively referenced GB/T 5779.2 to adapt to my country's technical requirements (see 8.4 and 10.5); --- Formula (C.3) has been deleted. In formula (C.2), d3 conforms to GB/T 196 (see Appendix C). The following editorial changes have been made to this document. ---Change the standard name to "Mechanical Properties of Fasteners Part 2.Nuts"; ---Referencing GB/T 90.3, GB/T 192, GB/T 193, GB/T 196, GB/T 197, and GB/T 1800.2. GB/T 3098.1, GB/T 3098.26, GB/T 6170, GB/T 6175, GB/T 9144, GB/T 9145, GB/T 16823.3, GB/T 22028, GB /Z 32564, and GB/T 33362 replace ISO 16426 and ISO 68-1. ISO 261, ISO 724, ISO 965-1, ISO 286-2, ISO 898-1, ISO 898-3, ISO 4032, ISO 4033, ISO 262, ISO 965-2, ISO 16047, ISO 965-5, ISO /T R16224 and ISO 18265. Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents. This document was proposed by the China Machinery Industry Federation. This document is under the jurisdiction of the National Fastener Standardization Technical Committee (SAC/TC85). This document was drafted by. China Machinery Productivity Promotion Center Co., Ltd., Yuxing Fasteners (Jiaxing) Co., Ltd., and Dingxi High Strength Fasteners Co., Ltd. Firmware Co., Ltd., Beijing Shouhang Science and Technology Development Co., Ltd., Ningbo Ningli High Strength Fasteners Co., Ltd., Shanghai Jiyoubiao No. 5 High Strength Fasteners Co., Ltd., Ningbo Jiulong Chuangzhan Fasteners Co., Ltd., Zhejiang Yutai Auto Parts Co., Ltd., Wuxi Standard Parts Factory Co., Ltd., Jinyi Industrial Co., Ltd., Shenzhen Aviation Standard Parts Co., Ltd., Zhejiang Guojian Testing Technology Co., Ltd. Shandong Gaoqiang Fasteners Co., Ltd., Hebei Xinde Electric Power Accessories Co., Ltd., Lengshuijiang Tianbao Industry Co., Ltd., Zhejiang Haili Co., Ltd. The company, Ningbo Dazhi Machinery Technology Co., Ltd., Zhejiang Dite High Strength Bolt Co., Ltd., and Shandong Tengda Fastening Technology Co., Ltd. Company, Dongtai Qinbiao Stainless Steel Co., Ltd., Zhejiang Guosheng Automotive Technology Co., Ltd., Shanghai High Strength Bolt Factory Co., Ltd., Hunan Zhong Jishenyi Testing Technology Co., Ltd., Hunan Shenyi Machinery Application Research Institute Co., Ltd., Ningbo Zhongji Machinery Parts Testing Co., Ltd. Jiangsu Baote Auto Parts Co., Ltd., Quzhou Tianli Fasteners Co., Ltd., Ningbo Kunyuan Fasteners Co., Ltd., and Jingjiang Feitian Fasteners Co., Ltd. Manufacturing Co., Ltd., Hebei Zhanyu Electromechanical Technology Co., Ltd., and Liaoning Zhongke Lile Testing Technology Service Co., Ltd. This document is subject to interpretation by the National Fastener Standardization Technical Committee. The release history of this document and the document it replaces is as follows. ---First published in 1982 as GB/T 3098.2-1982, and revised for the first time in.2000; ---In the second revision in.2015, it was incorporated into GB/T 3098.4-2000 "Mechanical Properties of Fasteners, Nuts with Fine Threads" (The previous versions of GB/T 3098.4-2000 are. GB/T 3098.4-1986, GB/T 3098.4-2000); ---This is the third revision.

Introduction

GB/T 3098 "Mechanical Properties of Fasteners" specifies the mechanical properties for different categories of fasteners, providing guidance for fastener design and manufacturing. It provides a basis for construction, acceptance inspection and use, and is proposed to consist of 28 parts. ---GB/T 3098.1 Mechanical properties of fasteners. bolts, screws and studs; ---GB/T 3098.2 Mechanical properties of fasteners – Part 2.Nuts; ---GB/T 3098.3 Mechanical properties of fasteners - Set screws; ---GB/T 3098.5 Mechanical properties of fasteners—Part 5.Self-tapping screws; ---GB/T 3098.6 Mechanical properties of fasteners - Stainless steel bolts, screws and studs; ---GB/T 3098.7 Mechanical Properties of Fasteners - Self-Extruding Screws; ---GB/T 3098.8 Mechanical properties of fasteners - Bolted connections for use at -200℃~700℃; ---GB/T 3098.9 Mechanical Properties of Fasteners - Effective Torque Type Steel Locknuts; ---GB/T 3098.10 Mechanical properties of fasteners – Bolts, screws, studs and nuts made of non-ferrous metals; ---GB/T 3098.11 Mechanical Properties of Fasteners - Self-Drilling and Self-Tapping Screws; ---GB/T 3098.12 Mechanical properties of fasteners - Conical proof load test for nuts; ---GB/T 3098.13 Mechanical properties of fasteners - Torque test and breaking torque of bolts and screws (nominal diameter 1~ 10mm; ---GB/T 3098.14 Mechanical properties of fasteners - Nut hole expansion test; ---GB/T 3098.15 Mechanical Properties of Fasteners - Stainless Steel Nuts; ---GB/T 3098.16 Mechanical properties of fasteners - Stainless steel set screws; ---GB/T 3098.17 Preload test for hydrogen embrittlement of fasteners—parallel bearing surface method; ---GB/T 3098.18 Test methods for mechanical properties of fasteners, specifically blind rivets; ---GB/T 3098.19 Mechanical Properties of Fasteners - Blind Rivets; ---GB/T 3098.20 Mechanical properties of fasteners - Guaranteed torque for wing nuts; ---GB/T 3098.21 Mechanical Properties of Fasteners - Stainless Steel Self-Tapping Screws; ---GB/T 3098.22 Mechanical properties of fasteners - Fine-grained non-quenched and tempered steel bolts, screws and studs; ---GB/T 3098.23 Mechanical properties of fasteners M42~M72 bolts, screws and studs; ---GB/T 3098.24 Mechanical properties of fasteners - Stainless steel and nickel alloy bolts, screws, studs and nuts for high temperature applications; ---GB/T 3098.25 Mechanical Properties of Fasteners - Guidelines for the Selection of Stainless Steel and Nickel Alloy Fasteners; ---GB/T 3098.26 Mechanical Properties of Fasteners - Flat Washers; ---GB/T 3098.27 Mechanical properties of fasteners—Part 27.Stainless steel flat washers; ---GB/T 3098.28 Mechanical properties of fasteners - Part 28.M42~M100 nuts. GB/T 3098 has been converted to ISO 898 series of mechanical properties of carbon steel and alloy steel fasteners and ISO 3506 series of mechanical properties of stainless steel fasteners. Performance, and mechanical properties of self-tapping screws, self-extruding screws, effective torque steel lock nuts, non-ferrous metal fasteners, self-drilling self-tapping screws, etc. International standards; independently formulated mechanical performance standards for blind rivets, fine-grained non-quenched and tempered steel fasteners, and M42~M72 external thread fasteners; incorporated into The test methods include. nut hole enlargement test, preload test for hydrogen embrittlement using the parallel bearing surface method, blind rivet test method, and guaranteed torque test for wing nuts. Legal standards. The standards for the mechanical properties of various materials and types of products, along with related testing methods, are incorporated into the GB/T 3098 series. For use. Nuts conforming to this document are compatible with bolts, screws, and studs conforming to GB/T 3098.1 and flat nuts conforming to GB/T 3098.26. Washer matching refers to the appropriate combination designed for specific applications. This document specifies appropriate combinations of different parameters for nuts. nut height (standard nut, type 1; high nut, type 2; thin nut, type 0), and diameter. Diameter range, coarse or fine thread, and performance grade related to heat treatment [non-quenched and tempered nuts (NQT) or quenched and tempered nuts] [Mother (QT)]. These combinations are based on bolt/nut compatibility, manufacturing processes, and market demand. Other combinations may be available if needed, such as for specific situations. For the design of nuts used in the following applications, see GB /Z 32564. To ensure the corresponding performance level, the material should have a certain strength. ---Quenched and tempered nuts (QT) specify a minimum carbon content and a minimum tempering temperature, characterized by a uniform martensitic structure; ---Non-quenched and tempered nuts (NQT) specify a minimum carbon content and are characterized by an unquenched microstructure. Some performance grades (related to nut type, diameter, coarse or fine thread) specify that nuts should not be quenched and tempered (NQT). 7.2 specifies the option of quenching and tempering; in this case, all quenching and tempering requirements apply to this nut. Non-standard nuts with full load capacity that meet the requirements of this document are classified as Type 1 or Type 2, and their classification is related to the minimum design thread height. The load-bearing capacity of a nut is primarily verified through its guaranteed load capacity. This applies to coarse threads, performance grades 6 and 8, and sizes M27 to M39. The nut, according to the latest calculations by Masaya Hagiwara[19] based on Alexander's theory[20], has increased the guaranteed load value (see GB /Z 32564). For these nuts, when the guaranteed load value in GB/T 3098.2-2015 differs from the recalculated guaranteed load value by more than [a certain percentage]... When the strength exceeds 5% (see Appendix C), it is necessary to study the strength of bolts, screws and studs that are matched with nuts as specified in GB/T 3098.1. The Vickers hardness values for each group (including performance grade, type, diameter range, and pitch) are selected and adjusted according to the same latest calculation results. The values shown below replace those in GB/T 3098.2 and GB/T 3098.4 before the.2015 merger and revision. GB/T 33362 currently lacks a specific relationship between hardness and tensile strength under cold work hardening conditions for steel, such as the widely used cold heading steel. The minimum hardness of steel used for quenched and tempered nuts (NQT) is for reference only and should not be considered as controversial. The criteria for determining the hardness at that time; the maximum hardness of 334HV is specified to prevent nuts from not being quenched and tempered due to unpredictable manufacturing processes. The brittle nature of (NQT) is a mandatory constraint, and this is a criterion for judgment in cases of controversy. However, it is worth noting the use of typical materials and Cold work hardening achieved through forging is unlikely to fully reach 302 HV, but the 334 HV limit covers inappropriate hardness testing or only due to... The hardness values are discrete due to local characteristics. Due to reduced or decreased market demand, Grade 5 fine thread Type 1 nuts and Grade 9 nuts have been removed. Grade 5 or Grade 9 nuts can be replaced by Grade 6 or Grade 10 nuts, respectively. Fastener Mechanical Properties Part 2.Nuts

1 Scope

This document specifies the requirements for coarse-pitch threads made of carbon steel or alloy steel when tested under ambient temperatures ranging from 10°C to 35°C. Mechanical and physical properties of fine-pitch thread nuts. Nuts applicable to this document. a) Ordinary thread conforming to GB/T 192; b) The diameter and pitch combination conforms to the specifications of GB/T 193 and GB/T 9144; c) Coarse thread specifications. M5~M39, fine thread specifications. M8×1~M39×3; d) Thread tolerances shall conform to GB/T 197, GB/T 9145, or GB/T 22028; e) Performance classes 04, 05, 5, 6, 8, 10, and 12, including guaranteed loads; f) Three types of nuts (see 5.1). standard nuts (Type 1), high-strength nuts (Type 2), and thin nuts (Type 0); g) Minimum outer diameter or width across sides s ≥ 1.45D; h) Compatible with bolts, screws and studs conforming to performance class GB/T 3098.1 (see Appendix B); i) Operating temperature range. -50℃ to 150℃ or up to 300℃. Warning. When tested at ambient temperatures between 10°C and 35°C, the nut must meet the requirements of this document; the applicable operating temperature of the nut is... The temperature range is -50℃ to 150℃. Under special application conditions, the nut can also exceed this temperature range, up to a maximum of 300℃. At high or low temperatures, the nut may not maintain its specified mechanical and physical properties. Therefore, the user should consider the service environment conditions of the connection. Make an appropriate choice (see 7.1). For the technical requirements of hot-dip galvanized nuts, see GB/T 5267.3. For special purpose nut designs, see GB /Z 32564. The following functional characteristics are not specified in this document. ---Effective torque type locking performance (see GB/T 3098.9); ---Torque-clamping force performance (test method see GB/T 16823.3); ---Weldability; ---Corrosion resistance.

2 Normative references

The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included. For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies. This document. GB/T 228.1 Metallic materials—Tensive testing—Part 1.Tests 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 methods (GB/T 230.1-2018, ISO 6508-1. 2016, MOD) GB/T 231.1 Metallic materials – Brinell hardness test – Part 1.Test methods (GB/T 231.1-2018, ISO 6506-1) 2014, MOD) GB/T 3098.9 Mechanical properties of fasteners - Effective torque type steel locknuts (GB/T 3098.9-2020, ISO 2320. ...