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GB/T 9125 consists of two parts under the general title Fasteners for steel pipe flange joints
——Part 1: PN designed;
——Part 2: Class designated.
This is Part 2 of GB/T 9125.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
This part replaces part of content of GB/T 9125-2010 Fasteners for pipe flange joints, and the following main technical changes have been made with respect to GB/T 9125-2010:
——The description of the “Scope” is modified (see Clause 1; Clause 1 of Edition 2010);
——The “Normative references” is supplemented and improved (see Clause 2; Clause 2 of Edition 2010);
——The specifications of bolts and studs are added (see Tables 1 and 2);
——The content of equal-length double end stud is deleted (see 3.2 of Edition 2010);
——The property classes A2-80 and A4-80 of hexagon head bolts and equal-length double end studs are deleted (see Tables 1 and 2 of Edition 2010);
——The material designations of full-thread studs and nuts are added (see Tables 2 and 4);
——The requirements for the tolerances of fasteners are added (see 3.4);
——The length and mass of fasteners are added (see 3.5);
——The manufacturing and heat treatment are added (see Clause 5);
——The specifications of “surface pretreatment of fastener” are modified (see 5.1.6; Clause 5 of Edition 2010);
——The inspection and test rules are modified (see Clause 6; Clauses 6 and 7 of Edition 2010);
——Annex A “Length and mass of fasteners” is added (see Annex A);
——The content of Class designated in the former Annex A is modified to Annex B (see Annex B; Annex A of Edition 2010);
——The content of the former Annex B is deleted (see Annex B of Edition 2010);
——Annex C “Classification of strength of fastener material” is added (see Annex C).
This part was proposed by the China Machinery Industry Federation.
This part is under the jurisdiction of SAC/TC 237 National Technical Committee on Pipeline Fittings of Standardization Administration of China.
The previous editions of this part are as follows:
——GB/T 9125-2003, GB/T 9125-2010.
Fasteners for steel pipe flange joints - Part 2: Class designated
1 Scope
This part of GB/T 9125 specifies the structural styles, dimensions and tolerances, materials, manufacturing and heat treatment, inspection and acceptance, product quality certificate, marking and labeling, protection and packaging requirements of fasteners for Class designated steel pipe flange joints.
This part is applicable to fasteners for steel pipe flange joints (including hexagon head bolts, full-thread studs and nuts) specified in GB/T 9124.2 and GB/T 13402.
2 Normative references
The following referenced documents are indispensable for the application 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 2 Fasteners - Ends of parts with external thread
GB/T 90.1 Fasteners - Acceptance inspection
GB/T 196 General purpose metric screw threads - Basic dimensions
GB/T 197 General purpose metric screw threads - Tolerances
GB/T 228.1 Metallic materials - Tensile testing - Part 1: Method of test at room temperature
GB/T 699 Quality carbon structure steels
GB/T 700 Carbon structural steels
GB/T 1220 Stainless steel bars
GB/T 1221 Heat-resistant steel bars
GB/T 3077 Alloy structure steels
GB/T 3098.1 Mechanical properties of fasteners - Bolts, screws and studs
GB/T 3098.2 Mechanical properties of fasteners - Nuts
GB/T 3098.6 Mechanical properties of fasteners - Stainless steel bolts, screws and studs
GB/T 3098.15 Mechanical properties of fasteners - Stainless steel nuts
GB/T 3103.1 Tolerances for fasteners - Bolts, screws, studs and nuts
GB/T 5276 Fasteners - Bolts, screws, studs and nuts - Symbols and designations of dimensions
GB/T 5779.1 Surface discontinuities of fasteners on bolts, screws and studs for general requirements
GB/T 5779.2 Fasteners - Surface discontinuities - Nuts
GB/T 5782 Hexagon head bolts
GB/T 5785 Hexagon head bolts - Fine pitch thread
3 Structural styles, dimensions and tolerances
3.1 Hexagon head bolts
3.1.1 The structural style of hexagon head bolts is detailed in Figure 1, and symbols and descriptions of dimensions shall meet the requirements of GB/T 5276.
a β=15°~30°.
b The end shall be chamfered.
c The length of incomplete thread u is less than or equal to 2 times the pitch.
d The arbitration benchmark of dw.
e The maximum arc transition.
Figure 1 Hexagon head bolt
3.1.2 When the thread specification of hexagon head bolt is less than or equal to M33, the pitch shall adopt coarse pitch thread series, and the dimensions shall comply with GB/T 5782; when the thread specification is greater than M33, the pitch shall adopt fine pitch thread series, and the dimensions shall comply with GB/T 5785. The thread specifications and property classes of hexagon head bolts shall be in accordance with those specified in Table 1.
Table 1 Thread specifications and property classes of hexagon head bolts
Standard Thread specification Property class
Carbon steel or alloy steel Stainless steel
GB/T 5782 M14, M16, M20, M24 5.6, 8.8 A2-70, A4-70
M27, M30, M33 A2-50, A4-50
GB/T 5785 M36×3, M39×3 5.6, 8.8 A2-50, A4-50
M42×3, M45×3, M48×3 As agreed As agreed
3.2 Full-thread studs
3.2.1 The structural style of full-thread studs is detailed in Figure 2, and symbols and descriptions of dimensions shall meet the requirements of GB/T 5276.
Figure 2 Full-thread stud
3.2.2 When the thread specification of full-thread stud is less than or equal to M33, the pitch shall adopt coarse pitch thread series; when the thread specification is greater than M33, the pitch shall adopt fine pitch thread series. The specifications and material designations of full-thread studs shall be in accordance with those specified in Table 2.
Table 2 Specifications and material designations of full-thread studs
Thread specification Material designation
M14, M16, M20, M24, M27, M30, M33, M36×3, M39×3, M42×3, M45×3, M48×3, M52×3, M56×3, M64×3, M70×3, M76×3, M82×3, M90×3, M95×3, M100×3 Q235A, 35, 40MnB, 40MnVB, 40Cr, 30CrMoA, 35CrMoA, 42CrMo, 35CrMoVA, 25Cr2MoVA, 40CrNiMoA, 12Cr5Mo, 20Cr13, 06Cr19Ni10, 06Cr17Ni12Mo2, 06Cr18Ni11Ti
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3.3 Hexagon nuts
3.3.1 The structural style of hexagon nut is detailed in Figure 3, and symbols and descriptions of dimensions shall meet the requirements of GB/T 5276.
a When the washer face type is required, it shall be indicated in the contract.
b β=15°~30°.
c θ=90°~120°.
Figure 3 Hexagon nut
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3.3.2 The dimensions of hexagon nuts shall be in accordance with those specified in Table 3.
Table 3 Dimensions of hexagon nuts In: mm
3.3.3 The specifications, property classes and material designations of hexagon nuts shall be in accordance with those specified in Table 4.
Table 4 Specifications, property classes and material designations of hexagon nuts
Style Specification Property class Material designation
Carbon steel or alloy steel Stainless steel
Style 1 M14, M16, M20M, M24 6, 8 A2-70, A4-70 —
M27, M30, M33, M36×3, M39×3 A2-50, A4-50
M42×3, M45×3, M48×3 As agreed As agreed
Style 2 M14, M16, M20, M24, M27, M30, M33, M36×3, M39×3, M42×3, M45×3, M48×3, M52×3, M56×3, M64×3, M70×3, M76×3, M82×3, M90×3, M95×3, M100×3 — Q235A, 25, 35, 40Mn, 30CrMoA, 35CrMoA, 35CrMoVA, 25Cr2MoVA, 40CrNiMoA, 12Cr5Mo, 20Cr13, 06Cr19Ni10, 06Cr17Ni12Mo2, 06Cr18Ni11Ti
3.4 Tolerances
3.4.1 For the bolts and studs with thread specification less than or equal to M24 and the nominal length meeting the value in Items a) and b), whichever is smaller, the unmarked dimensional tolerances and geometric tolerances shall meet the requirements of Grade A products in GB/T 3103.1:
Foreword II
1 Scope
2 Normative references
3 Structural style, dimension and tolerance
3.1 Hexagon head bolt
3.2 Full-thread stud
3.3 Hexagon nut
3.4 Tolerance
3.5 Length and mass
4 Materials
4.1 General requirements
4.2 Technical requirements
5 Manufacturing and heat treatment
5.1 Manufacturing
5.2 Heat treatment
6 Inspection and acceptance
6.1 Inspection
6.2 Acceptance
7 Product quality certificate
8 Marking and labeling
9 Protection and packaging
Annex A (Informative) Length and mass of fasteners
Annex B (Informative) Calculation of length of fasteners
Annex C (Informative) Classification of strength of fastener material
