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GB/T 3098.23-2020 English PDF

GB/T 3098.23-2020_English: PDF (GB/T3098.23-2020)
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GB/T 3098.23-2020English559 Add to Cart 6 days [Need to translate] Mechanical properties of fasteners -- M42~M72 bolts, screws and studs Valid GB/T 3098.23-2020


BASIC DATA
Standard ID GB/T 3098.23-2020 (GB/T3098.23-2020)
Description (Translated English) Mechanical properties of fasteners -- M42��M72 bolts, screws and studs
Sector / Industry National Standard (Recommended)
Classification of Chinese Standard J13
Classification of International Standard 21.060.10
Word Count Estimation 30,361
Date of Issue 2020-03-31
Date of Implementation 2020-10-01
Drafting Organization China Machinery Productivity Promotion Center, Shanghai Shenguang High Strength Bolt Co., Ltd., Dingxi High Strength Fastener Co., Ltd., Beijing Jinfeng Kechuang Wind Power Equipment Co., Ltd., Shandong High Strength Fastener Co., Ltd., Hebei Xinde Electric Power Parts Co., Ltd., Zhejiang Haili Co., Ltd., Jiangsu Zhongcheng Fastening Technology Development Co., Ltd., Zhejiang Dite High Strength Bolt Co., Ltd., Jinyi Industrial Co., Ltd., Lengshuijiang Tianbao Industrial Co., Ltd., Hunan Feiwo New Energy Technology Co., Ltd. , Ningbo Jinding Fastener Co., Ltd., Ningbo Kunyuan Fastener Co., Ltd., Shanghai Qunli Fastener Manufacturing Co., Ltd., Shanghai High Strength Bolt Factory Co., Ltd., General Parts Product Quality Supervision and Testing Center for Machinery Industry, Zhejiang National Inspection Testing Technology Co., Ltd., Hunan Shenyi Machinery Application Research
Administrative Organization National Fastener Standardization Technical Committee (SAC/TC 85)
Proposing organization China Machinery Industry Federation
Issuing agency(ies) State Administration for Market Regulation, National Standardization Administration


GB/T 3098.23-2020 Mechanical properties of fasteners--M42 ~ M72 bolts, screws and studs ICS 21.060.10 J13 National Standards of People's Republic of China Fastener mechanical properties M42 ~ M72 bolts, screws and studs 2020-03-31 release 2020-10-01 implementation State Administration of Market Supervision and Administration Issued by the National Standardization Management Committee Contents Foreword I 1 Scope 1 2 Normative references 1 3 Terms and definitions 2 4 Code 2 5 Marking system for performance levels 3 6 Material 3 7 Mechanical and physical properties 4 8 Applicability of test methods 7 9 Test method 10 10 Logo 24 References 27 Foreword GB/T 3098 "Mechanical Properties of Fasteners" includes the following parts. --- GB/T 3098.1 Mechanical properties of fasteners Bolts, screws and studs; --- GB/T 3098.2 Fastener mechanical performance nut; --- GB/T 3098.3 Fastening screws for mechanical properties of fasteners; --- GB/T 3098.5 Self-tapping screws for mechanical properties of fasteners; --- GB/T 3098.6 Mechanical properties of fasteners Stainless steel bolts, screws and studs; --- GB/T 3098.7 Fastener mechanical properties self-extruded screws; --- GB/T 3098.8 Mechanical properties of fasteners-Bolt connection parts used at.200 ℃ ~ 700 ℃; --- GB/T 3098.9 Effective mechanical properties of fasteners, torque-type steel lock nuts; --- 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 self-tapping screws; --- GB/T 3098.12 Mechanical properties of fasteners Nut-conical guaranteed load test; --- GB/T 3098.13 Mechanical properties of fasteners Torque test and failure torque of bolts and screws nominal diameter 1 ~ 10mm; --- GB/T 3098.14 Fastener mechanical performance nut 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 Fastener mechanical properties check hydrogen embrittlement preload test parallel bearing surface method; --- GB/T 3098.18 Fastener mechanical properties blind rivet test method; --- GB/T 3098.19 Fastener mechanical properties core pulling rivets; --- GB/T 3098.20 Fastener mechanical performance butterfly nut guaranteed torque; --- GB/T 3098.21 Fastener mechanical properties stainless steel self-tapping screws; --- GB/T 3098.22 fastener mechanical properties ultra-fine grain 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; --- GB/T 3098.25 Mechanical properties of fasteners Selection guide for stainless steel and nickel alloy fasteners. This part is Part 23 of GB/T 3098. This section was drafted in accordance with the rules given in GB/T 1.1-2009. This part is proposed by China Machinery Industry Federation. This part is under the jurisdiction of the National Fastener Standardization Technical Committee (SAC/TC85). This section was drafted by. China Machine Productivity Promotion Center, Shanghai Shenguang High Strength Bolt Co., Ltd., Dingxi High Strength Fastener Co., Ltd. Co., Ltd., Beijing Goldwind Kechuang Wind Power Equipment Co., Ltd., Shandong Gaoqiang Fastener Co., Ltd., Hebei Xinde Power Parts Co., Ltd., Zhejiang Haili Co., Ltd., Jiangsu Zhongcheng Fastening Technology Development Co., Ltd., Zhejiang Dite High Strength Bolt Co., Ltd., Jinyi Industrial Co., Ltd. Co., Ltd., Lengshui Jiang Tianbao Industrial Co., Ltd., Hunan Fewo New Energy Technology Co., Ltd., Ningbo Jinding Fastener Co., Ltd., Ningbo Kunyuan Fastener Co., Ltd., Shanghai Qunli Fastener Manufacturing Co., Ltd., Shanghai High Strength Bolt Factory Co., Ltd., General Machinery Industry Parts Product Quality Supervision and Inspection Center, Zhejiang National Inspection and Testing Technology Co., Ltd., Hunan Shenyi Machinery Application Research Institute Co., Ltd., Meishan CRRC Fastener Technology Co., Ltd. and Zhejiang New Oriental Auto Parts Co., Ltd. This part is interpreted by the National Fastener Standardization Technical Committee. Fastener mechanical properties M42 ~ M72 bolts, screws and studs 1 Scope This part of GB/T 3098 stipulates that the screw The mechanical and physical properties of bolts, screws and studs. Fasteners that meet the requirements of this part within this ambient temperature range Within the scope, the specified mechanical and physical properties may not be achieved. Note 1. The applicable temperature of fasteners produced according to this section is -50 ℃ ~ 150 ℃. When the use temperature exceeds -50 ℃ ~ 150 ℃, even up to At 300 ℃, users need to consult with relevant parties. Note 2. For the selection and application of low-temperature and high-temperature steel, refer to GB/T 150.2, EN10269, ASTMF2281 and ASTMA320/A320M. Note 3. This part does not apply to some fasteners where the head shear area is small due to the head geometry, which may not meet the tensile or torque requirements of this part fastener. Fasteners applicable to this part. a) made of alloy steel; b) Ordinary thread conforming to GB/T 192; c) Performance level 8.8, 10.9, coarse thread M42 ~ M68, fine thread M45 × 3 ~ M72 × 6 d) The combination of diameter and pitch in accordance with GB/T 193; e) Comply with the tolerances specified in GB/T 197 and GB/T 9145. This section does not specify the following performance requirements. --- Solderability; --- corrosion resistance; --- Shear stress resistance; --- Torque-clamping force performance; --- Fatigue resistance. 2 Normative references The following documents are essential for the application of this document. For dated references, only the dated version applies to this article Pieces. For the cited documents without date, the latest version (including all amendments) applies to this document. GB/T 90.3 fastener quality assurance system (GB/T 90.3-2010, ISO 16426..2002, IDT) GB/T 192 basic thread basic tooth profile (GB/T 192-2003, ISO 68-1..1998, MOD) GB/T 196 basic dimensions of common thread (GB/T 196-2003, ISO 724..1993, MOD) GB/T 197 General thread tolerance (GB/T 197-2018, ISO 965-1..2013, MOD) GB/T 228.1 Tensile test of metal materials Part 1. Room temperature test method (GB/T 228.1-2010, ISO 6892-1. 2009, MOD) GB/T 229 Charpy pendulum impact test method for metallic materials (GB/T 229-2007, ISO 148-1..2006, MOD) GB/T 230.1 Rockwell hardness test of metal materials Part 1. Test method (GB/T 230.1-2018, ISO 6508-1. 2016, MOD) GB/T 231.1 Brinell hardness test of metallic materials Part 1. Test method (GB/T 231.1-2018, ISO 6506-1. 2014, MOD) GB/T 3098.1 Mechanical properties of fasteners Bolts, screws and studs (GB/T 3098.1-2010, ISO 898-1..2009, MOD) GB/T 4340.1 Vickers hardness test of metal materials Part 1. Test method (GB/T 4340.1-2009, ISO 6507-1. 2005, MOD) GB/T 5267.1 plating for fasteners (GB/T 5267.1-2002, ISO 4042..1999, IDT) GB/T 5267.2 Non-electrolytic zinc sheet coating for fasteners (GB/T 5267.2-2017, ISO 10683..2014, MOD) GB/T 5267.3 hot-dip galvanized layer of fasteners (GB/T 5267.3-2008, ISO 10684..2004, IDT) GB/T 5276 fasteners bolts, screws, studs and nuts size code and marking (GB/T 5276-2015, ISO 225..2010, MOD) GB/T 5277 through holes for fastener bolts and screws (GB/T 5277-1985, eqvISO 273. 1979) GB/T 5779.1 General requirements for surface defects of bolts, screws and studs (GB/T 5779.1-2000, idtISO 6157-1. 1988) GB/T 5779.3 Particular requirements for bolts, screws and studs on surface defects of fasteners (GB/T 5779.3-2000, idtISO 6157-3. 1988) GB/T 16825.1 Inspection of static uniaxial testing machine Part 1. Inspection and calibration of tensile and/or compression testing machine force measuring system (GB/T 16825.1-2008, ISO 7500-1..2004, IDT) 3 Terms and definitions The terms and definitions defined in GB/T 3098.1 apply to this document. 4 Code The codes given in GB/T 5276 and GB/T 197 and the following codes apply to this document. A Elongation after break of mechanically processed test pieces,% Af Fastener elongation after breaking As, nom nominal thread cross-sectional area, mm2 b Thread length, mm bm stud (screw into metal end) thread length, mm d Thread nominal diameter, mm d0 Diameter of the machined test piece, mm d1 Basic diameter of external thread, mm d2 Basic diameter of external thread, mm d3 Small diameter of external thread, mm da Diameter of transition circle (inner diameter of bearing surface), mm dh Aperture of wedge pad or gasket, mm ds unthreaded rod diameter, mm dt Nominal thread diameter of machined test piece, mm E Height of thread not decarburized, mm Fm ultimate tensile load, N Fm, min Minimum tensile load, N Fp guaranteed load, N G Depth of thread decarburization layer, mm H Thread original triangle height, mm H1 Tooth height of external thread under maximum solid condition, mm k head height, mm KV V-notch specimen impact energy absorption, J l Nominal length, mm l0 Total length of fastener before applying load, mm l1 The total length of the fastener after the first load is removed, mm l2 The total length of the fastener after removing the second load, mm ls Length of unthreaded shank, mm lt Total length of stud, mm lth Length of unthreaded fasteners in the test fixture, mm Lc Length of the straight section of the machined test piece, mm L0 The initial measured length of the machined test piece, mm Total length of Lt machined test piece, mm Lu The final measured length of the machined specimen, mm P pitch, mm r Fillet radius, mm Rm tensile strength, MPa Rp0.2 The stress at the specified plastic elongation of the machined specimen is 0.2%, MPa s width of opposite side, mm S0 Cross-sectional area of mechanically processed test piece before tensile test, mm2 SP Guaranteed stress, MPa Su The cross-sectional area of the machined test piece, mm Z Cross-section shrinkage of mechanically processed test pieces,% α Wedge angle for wedge load tensile test, (°) 5 Marking system for performance levels The marking system for performance levels in this part is in accordance with the provisions of GB/T 3098.1. 6 Materials Table 1 specifies the chemical composition limits and minimum tempering temperatures of steels for various performance levels. The chemical composition of the material should comply with the relevant material standards Regulations. Note. Certain chemical elements are restricted or prohibited by the laws and regulations of some countries. When related countries or regions are involved, attention should be paid. Table 1 Materials Performance grade materials and heat treatment Chemical composition limit /% (melting analysis) a CPSB min max max max max Tempering temperature min 8.8c Alloy steel quenched and tempered b 0.20 0.55 0.025 0.025 0.003 500 10.9c quenched and tempered alloy steel b 0.30 0.55 0.025 0.025 0.003 500 a When there is a dispute, implement the analysis of the finished product. b These alloy steels should contain at least one of the following elements, and their minimum contents are. chromium 0.30%; nickel 0.30%; molybdenum 0.20%; vanadium 0.10%. When When there are two, three or four composite alloy components, the content of alloy elements cannot be less than 70% of the total content of individual alloy elements. c For materials with these performance levels, there should be sufficient hardenability to ensure that the core of the thread section of the fastener obtains about 90% martensite structure. 7 Mechanical and physical properties Fasteners with specified performance levels shall meet the mechanical and physical properties specified in Table 2 to Table 6 at ambient temperature. Chapter 8 provides applicable test methods to verify whether the fasteners meet the requirements of Table 2 to Table 6. Table 2 Mechanical and physical properties of bolts, screws and studs No. Mechanical or physical properties Performance level 8.8 10.9 1 Tensile strength Rm/MPa Nominal a 800 1000 min 830 1040 2 The stress Rp0.2/MPa when the specified plastic elongation is 0.2% Nominal b 640 900 min 660 940 Guaranteed stress SPc/MPa Nominal 600 830 Guaranteed stress ratio SP, nominal/Rp0.2, min 0.91 0.88 4 Elongation after break of mechanically processed specimens A /% min 12 9 5 Cross-section shrinkage of mechanically processed specimens Z /% min 52 48 6 The rigidity of the head shall not be broken or cracked 7 Vickers hardness HV F≥98N min 255 320 max 335 380 8 Brinell hardness HBW F = 30D2 min 250 316 max 331 375 9 Rockwell hardness HRC min 23 32 max 34 39 10 Surface hardness HV0.3 max dd, e Table 2 (continued) No. Mechanical or physical properties Performance level 8.8 10.9 Height of undecarburized layer of thread E/mm min 1/2H1 2/3H1 Depth of thread decarburization layer G/mm max 0.015 12 Hardness reduction value after tempering HV max 20 13 Absorbed energy KVf/J min 27 27 14 Surface defects GB/T 5779.1 a stipulates the nominal value, only the performance grade mark system needs, see Chapter 5. b Measure the stress Rp0.2 when the specified plastic elongation is 0.2%. c Tables 4 and 6 specify the guaranteed load values. d When using HV0.3 to measure the surface hardness and core hardness, the surface hardness of the fastener should not be higher than the core hardness (measured at 1/2 radius) by 30HV unit. e The maximum surface hardness is not greater than 390HV. f Test temperature is measured at -20 ℃, see 9.9. Table 3 Minimum tensile load coarse thread Thread specification (d) Thread nominal cross-sectional area As, nominal a/mm2 Performance level 8.8 10.9 Minimum tensile load Fm, min (As, nominal × Rm, min)/N M42 1120 929600 1164800 M45 1310 1087300 1362400 M48 1470 1220100 1528800 M52 1760 1460800 1830400 M56 2030 1684900 2111200 M60 2360 1958800 2454400 M64 2680 2224400 2787200 M68 3060 2539800 3182400 aAs, nominal calculation see 9.1.6.1. Table 4 Guaranteed load coarse thread Thread specification (d) Thread nominal cross-sectional area As, nominal a/mm2 Performance level 8.8 10.9 Guaranteed load FP (As, nominal × SP, nominal)/N M42 1120 672000 929600 M45 1310 786000 1087300 M48 1470 882000 1220100 M52 1760 1056000 1460800 M56 2030 1218000 1684900 M60 2360 1416000 1958800 M64 2680 1608000 2224400 M68 3060 1836000 2539800 aAs, nominal calculation see 9.1.6.1. Table 5 Fine-pitch thread with minimum tensile load Thread specification (d × P) Thread nominal cross-sectional area As, nominal a/mm2 Performance level 8.8 10.9 Minimum tensile load Fm, min (As, nominal × Rm, min)/N M45 × 3 1400 1162000 1456000 M52 × 4 1830 1518900 1903200 M56 × 4 2144 1779520 2229760 M60 × 4 2490 2066700 2589600 M64 × 4 2851 2366330 2965040 M72 × 6 3460 2871800 3598400 aAs, nominal calculation see 9.1.6.1. Table 6 Guaranteed load fine thread Thread specification (d × P) Thread nominal cross-sectional area As, nominal a/mm2 Performance level 8.8 10.9 Guaranteed load FP (As, nominal × SP, nominal)/N M45 × 3 1400 840000 1162000 M52 × 4 1830 1098000 1518900 M56 × 4 2144 1286400 1779520 M60 × 4 2490 1494000 2066700 M64 × 4 2851 1710600 2366330 M72 × 6 3460 2076000 2871800 aAs, nominal calculation see 9.1.6.1. 8 Applicability of test methods 8.1 General FF and MP two test series (group), you can test the mechanical and physical properties of the fasteners specified in Table 2. FF group for fastening The finished product is tested, and the MP group is used for fastener material performance testing. The FF and MP groups are further divided into. FF1, FF2 and MP1. 8.2 Bearing capacity of fasteners Fasteners with full load capacity (standardized or non-standardized) shall be subjected to tensile tests on the finished fasteners according to FF1 and FF2. a) The fracture should occur within the length of the unthreaded thread; b) The minimum tensile load (Fm, min) should meet the requirements of Table 3 or Table 5. 8.3 Manufacturer's control Fasteners produced in accordance with this section, when using the "implementable tests" specified in Tables 7 to 9, shall comply with the techniques in Tables 2 to 6. Claim. This part does not require the manufacturer to implement tests for each production batch, but the manufacturer's responsibility is. you can choose your own method, such as work Sequence control or inspection to ensure that each production batch meets all technical requirements. In case of dispute, the test method specified in Chapter 9 shall be followed. 8.4 Supplier control The supplier can choose its own method to control the fasteners provided by it to meet the mechanical and physical properties specified in Table 2 to Table 6. In case of dispute, the test method specified in Chapter 9 shall be followed. 8.5 Demand side control The buyer can choose the appropriate test series from 8.6 to control the quality of the delivered fasteners according to the test method in Chapter 9. In case of dispute, the test method specified in Chapter 9 shall be followed. 8.6 Tests that can be carried out on fasteners and machined test pieces 8.6.1 General According to the test method specified in Chapter 9, Table 7 ~ Table 9 specifies the applicability of FF1 ~ FF2, MP1. Table 7 and Table 8 provide the FF1 and FF2 test series for the finished fastener test. FF1. used to determine the standard head and standard rod or thin rod (full load capacity), that is, ds> d2 or ds≈d2 finished bolts and screws For performance, see Table 7. FF2. It is used to determine the performance of the standard or thin rod (full load capacity) that is ds> d2 or ds≈d2 finished stud, see Table 8. Table 9 provides MP1 test series for fastener material performance tests and/or improved process tests. FF1 and FF2 can also be used For this purpose. MP1. Used to test the performance of fastener materials and/or improved processes on mechanically processed test pieces, see Table 9. 8.6.2 Applicability The applicability of various test methods to fasteners is in accordance with Table 7 ~ Table 9. 8.6.3 Delivery test results When the purchaser requests the delivery of a report (special order) including the test results, they shall select from Table 7 to Table 9 as specified in Chapter Take the test method. Special tests prescribed by the purchaser shall be agreed upon when ordering. Table 7 FF1 test series bolts and screws with full bearing capacity No. (See Table 2) Performance test method Performance level 8.8, 10.9 l < 2.5d or b < 2.0d l≥2.5d and b≥2.0d 1 Minimum tensile strength Rm, min Wedge load tensile test 9.1 NF a Tensile test 9.2 NF a 3 Nominal guaranteed stress SP, nominal guaranteed load test 9.3 NF 6 Head robustness 9.1 7 or 8 or 9 Hardness hardness test 9.5 10 Maximum surface hardness carbon increase test 9.7 11 Maximum decarburization layer decarburization test 9.6 12 Hardness reduction value after tempering and tempering test 9.8 bb 14 Surface defects Surface defects inspection 9.10 Can be implemented. the test can be carried out according to Chapter 9, but in case of dispute, it should be carried out according to Chapter 9. It can only be carried out when there is a clear provision. the test can be carried out in accordance with Chapter 9. In case of dispute, this test is an arbitration test. NF cannot be carried out. the test cannot be carried out due to the shape and/or size of the fastener (e.g. the length is too short to be tested, headless), or because Applicable to special types of fasteners (such as high-temperature treatment fastener test). al ≥ 2d and b < 2d, see 9.1.5 and 9.2.5. b In case of dispute, this test is an arbitration test. Table 8 Finished studs with full bearing capacity of FF2 test series No. (See Table 2) Performance test method Performance level 8.8, 10.9 lt < 3d or b < 2.0d lt≥3d and b≥2.0d 1 Minimum tensile strength Rm, min Tensile test 9.2 NF a 3 Nominal guaranteed stress SP, nominal guaranteed load test 9.3 NF 7 or 8 or 9 Hardness hardness test 9.5 10 Maximum surface hardness carbon increase test 9.7 11 Maximum decarburization layer decarburization test 9.6 Table 8 (continued) No. (See Table 2) Performance test method Performance level 8.8, 10.9 lt < 3d or b < 2.0d lt≥3d and b≥2.0d 12 Hardness reduction value after tempering and tempering test 9.8 bb 14 Surface defects Surface defects inspection 9.10 Can be implemented. the test can be carried out according to Chapter 9, but in case of dispute, it should be carried out according to Chapter 9. It can only be carried out when there is a clear provision. the test can be carried out in accordance with Chapter 9. In case of dispute, this test is an arbitration test. NF cannot be carried out. the test cannot be carried out due to the shape and/or size of the fastener (e.g. the length is too short to be tested, headless), or because Applicable to special types of fasteners (such as high-temperature treatment fastener test). a If the stud breaks within the thread length bm screwed into the metal end, the minimum hardness can be substituted for Rm, min, or it can also be measured with a mechanically processed test piece according to 9.4 Set the tensile strength Rm. b In case of dispute, this test is an arbitration test. Table 9 Mechanical properties of MP1 test series to determine material properties No. (See Table 2) Performance test method Performance level 8.8, 10.9 d0 \u003cd3min And b≥d And l≥6.5d b≥d And l≥ d 26mm d0≥0.75ds and b≥d and l≥5.5d 8mm 1 Minimum tensile strength Rm, min The specified plastic elongation is 0.2% The stress at time Rp0.2min 4 Minimum elongation after breaking Amin 5 Minimum shrinkage rate Zmin Mechanical processing test Pull test 9.4 aaa b, cd, ef, g 7 or 8 or 9 Hardness hardness test 9.5 10 Maximum surface hardness carbon increase test 9.7 11 Maximum decarburization layer decarburization test 9.6 13 Minimum absorbed energy KV, min Impact test lh or lt≥55mm 9.9 Can be implemented. the test can be carried out according to Chapter 9, but in case of dispute, it should be carried out according to Chapter 9. It can only be carried out when there is a clear provision. the test can be carried out in accordance with Chapter 9. In case of dispute, this test is an arbitration test. NF cannot be carried out. the test cannot be carried out due to the shape and/or size of the fastener (e.g. the length is too short to be tested, headless), or because Applicable to special types of fasteners (such as high-temperature treatment fastener test). a If the stud is measured, the minimum total length should be increased by 1d in the length formula. b For bolts and screws, when measuring Zmin, l≥5d. c For studs, when Zmin is determined, lt≥6d d For bolts and screws, when determining Zmin, l≥d 20mm. e For studs, when measuring Zmin, lt ≥ 2d 20mm. f For bolts and screws, when measuring Zmin, l≥4d 8mm. g For studs, when measuring Zmin, lt≥5d 8mm. h Head height can be included. 9 Test method 9.1 Bolt and screw (excluding stud) finished wedge load test 9.1.1 General This test can simultaneously determine. --- Tensile strength of finished bolts and screws Rm; --- The firmness of the junction between the head and the unthreaded shank or threaded part. 9.1.2 Scope of application This test is applicable to bolts and screws that meet the following requirements. --- Flat bearing surface or zigzag surface; --- Head bearing capacity is stronger than threaded rod; --- Head bearing capacity is stronger than non-threaded rod; --- Unthreaded rod diameter ds> d2 or ds≈d2; --- Nominal length l≥2.5d; --- Thread length b≥1.5d; --- Thread length of bolted structure b < 2d; --- 42mm≤d≤72mm. 9.1.3 Equipment The tensile testing machine should meet the requirements of GB/T 16825.1. The self-centering device cannot be used because of the requirements for Figure 1 and Table 12 The angle of the wedge pad has a greater influence. 9.1.4 Test device Fixtures, wedge pads and threaded clamps shall be as follows. --- Hardness. ≥45HRC; --- Threads of internally threaded fixtures. according to Table 10; --- Through hole diameter dh. according to the provisions of Table 11; --- Wedge pad. According to Figure 1, Table 11 and Table 12. Table 10 Threads of internal thread clamp Fastener surface treatment Thread tolerance Thread of fastener before surface treatment Without surface treatment 6h or 6g 6H According to GB/T 5267.1 electroplating 6g or 6e or 6f 6H According to GB/T 5267.2 non-electrolytic zinc flake coa... ......

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