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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 1 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, 2 and 3);
——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 pitch of M52 and above thread specifications is modified from 3 to 4 (see Tables 1, 2, 3 and 4; Tables 1, 2, 3 and 4 of Edition 2010);
——The material designations of equal-length double end studs are deleted (see Table 2 of Edition 2010);
——The M64×3 and above thread specifications of studs and nuts are deleted (see Tables 2, 3 and 4 of Edition 2010);
——The material designations of full-thread studs and nuts are added (see Tables 3 and 5);
——The requirements for the tolerances of fasteners are added (see 3.5);
——The length and mass of fasteners are added (see 3.6);
——The manufacturing and heat treatment are added (see Clause 5);
——The specifications of “surface pretreatment of fasteners” are modified (see 5.1.5; 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 PN 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 1: PN 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, and protection and packaging requirements of fasteners for PN designated steel pipe flange joints.
This part is applicable to fasteners for steel pipe flange joints (including hexagon head bolts, equal-length double end studs, full-thread studs and nuts) specified in GB/T 9124.1.
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 901 Double end studs (clamping type) - Product grade B
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 type of hexagon head bolts is detailed in Figure 1, 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 bolt
Standard Thread specification Property class
Carbon steel or alloy steel Stainless steel
GB/T 5782 M10, M12, 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, M52×4, M56×4 As agreed As agreed
3.2 Equal-length double end studs
3.2.1 The structural style of equal-length double end studs is detailed in Figure 2, and symbols and descriptions of dimensions shall meet the requirements of GB/T 5276.
Figure 2 Equal-length double end stud
3.2.2 When the thread specification of equal-length double end 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, and the dimensions shall comply with GB/T 901; when the thread specification is M45×3, the length of useful thread b shall be 102mm; when the thread specification is M52×4, the length of useful thread b shall be 116mm. The thread specifications and property classes of equal-length double end studs shall be in accordance with those specified in Table 2.
Table 2 Thread specifications and property classes of equal-length double end studs
Standard Thread specification Property class
Carbon steel or alloy steel Stainless steel
GB/T 901 M10, M12, M14, M16, M20, M24 5.6, 8.8 A2-70, A4-70
M27, M30, M33, M36×3, M39×3 A2-50, A4-50
M42×3, M45×3, M48×3, M52×4, M56×4 As agreed As agreed
3.3 Full-thread studs
3.3.1 The structural style of full-thread studs is detailed in Figure 3, and symbols and descriptions of dimensions shall meet the requirements of GB/T 5276.
Figure 3 Full-thread stud
3.3.2 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 3.
Table 3 Thread specifications and material designations of full-thread studs
Thread specification Material designation
M10, M12, M14, M16, M20, M24, M27, M30, M33, M36×3, M39×3, M42×3, M45×3, M48×3, M52×4, M56×4 Q235A, 35, 40MnB, 40MnVB, 40Cr, 30CrMoA, 35CrMoA, 42CrMo, 35CrMoVA, 25Cr2MoVA, 40CrNiMoA, 12Cr5Mo, 20Cr13, 06Cr19Ni10, 06Cr17Ni12No2, 06Cr18Ni11Ti
3.4 Hexagon nuts
3.4.1 The structural style of hexagon nut is detailed in Figure 4, 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 4 Hexagon nut
3.4.2 The dimensions of hexagon nuts shall be in accordance with those specified in Table 4.
Table 4 Dimensions of hexagon nuts In: mm
3.4.3 The specifications, property classes and material designations of hexagon nuts shall be in accordance with those specified in Table 5.
Table 5 Specifications, property classes and material designations of hexagon nuts
Style Specification Property class Material designation
Carbon steel or alloy steel Stainless steel
Style 1 M10, M12, M14, M16, M20, M24 6, 8 A2-70, A4-70 —
M27, M30, M33, M36×3, M39×3 A2-50, A4-50
M42×3, M45×3, M48×3, M52×4, M56×4 As agreed As agreed
Style 2 M10, M12, M14, M16, M20, M24, M27, M30, M33, M36×3, M39×3, M42×3, M45×3, M48×3, M52×4, M56×4 — Q235A, 25, 35, 40Mn, 30CrMoA, 35CrMoA, 35CrMoVA, 25Cr2MoVA, 40CrNiMoA, 12Cr5Mo, 20Cr13, 06Cr19Ni10, 06Cr17Ni12Mo2, 06Cr18Ni11Ti
3.5 Tolerances
3.5.1 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 geometrical tolerances shall meet the requirements of Grade A products in GB/T 3103.1:
a) ≤10d;
b) ≤150mm.
3.5.2 For the bolts and studs with thread specification greater than 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 B products in GB/T 3103.1:
a) >10d;
b) >150mm.
3.5.3 The dimensional tolerances and geometric tolerances of nuts with thread specification less than or equal to M16 shall meet the requirements of Grade A products in GB/T 3103.1, and the dimensional tolerances and geometric tolerances of nuts with thread specification greater than M16 shall meet the requirements of Grade B products in GB/T 3103.1.
3.5.4 The thread tolerances of bolts and studs shall meet the requirements of 6g in GB/T 197 while those of nuts shall meet the requirements of 6H in GB/T 197.
3.5.5 The tolerances of fasteners not specified shall meet the requirements of GB/T 3103.1.
3.6 Length and mass
3.6.1 See Annex A for the length and mass of fasteners.
3.6.2 See Annex B for the calculation of the length of fasteners.
4 Materials
4.1 General requirements
4.1.1 The fastener raw materials shall be provided with quality certificate and shall be subjected to chemical composition analysis. For fasteners with the same steel grade, the same smelting furnace number, the same section dimension and the same heat treatment conditions, the sampling quantity of the fastener raw materials shall be 1% and shall not be less than one piece per batch.
4.1.2 After heat treatment or strain hardening, the blank shall be subjected to mechanical property analysis and shall meet the following requirements:
a) The blanks with the same steel grade, the same smelting furnace number, the same section dimension, the same heat treatment conditions and the manufacturing date shall form a batch, and the sampling quantity of each batch shall be one piece.
b) The sampling direction of the specimen shall be longitudinal. When the diameter of the blank is less than or equal to 40mm, the longitudinal axis of the specimen shall be located in the center of the blank. When the diameter of the blank is greater than 40mm, the longitudinal axis of the specimen shall be located at 1/2 of the radius of the blank.
c) Take a tensile specimen for each blank for full-thread stud. The tensile test shall meet the requirements of GB/T 228.1.
d) The tensile test results of full-thread stud blank shall be in accordance with those specified in Table 6.
e) When the tensile test results are unqualified, two tensile specimens shall be taken from the same blank for re-inspection and all the three properties shall be determined. If any one item in the test results is unqualified, this batch of blanks is judged as unqualified.
f) The whole batch of blanks judged as unqualified shall be subjected to heat treatment again, and then re-tested according to the above procedure.
4.1.3 Fastener materials with temperature lower than or equal to -20℃ shall be subjected to low temperature Charpy impact test, which shall meet the requirements of relevant standards.
4.1.4 The blanks of full-thread studs and Style 2 nuts shall be subjected to hardness test by batches, and no less than 3 specimens shall be taken from each batch.
4.1.5 See Annex C for the classification of strength of fastener material.
4.2 Technical requirements
4.2.1 The materials and mechanical properties of hexagon head bolts and equal-length double end studs shall meet the requirements of GB/T 3098.1 or GB/T 3098.6.
4.2.2 The materials and mechanical properties of full-thread studs shall be in accordance with those specified in Table 6.
Table 6 Materials and mechanical properties of full-thread studs
4.2.3 The materials and mechanical properties of Style 1 hexagon nuts shall meet the requirements of GB/T 3098.2 or GB/T 3098.15.
4.2.4 The materials and hardness of Style 2 nuts shall be in accordance with those specified in Table 7.
Table 7 Materials and hardness of Style 2 nuts
5 Manufacturing and heat treatment
5.1 Manufacturing
5.1.1 The basic dimensions of the threads shall meet the requirements of GB/T 196.
5.1.2 Except that the surface roughness of thread flanks and roots of bolts and studs shall not be greater than Ra 3.2 and those of nuts shall not be greater than Ra 6.3, the surface roughness of the rest shall not be greater than Ra 12.5.
5.1.3 The minimum height of the non-decarburized layer of bolt and stud threads E is 0.5 times the thread height, and the maximum depth of the fully decarburized layer is 0.015mm; the decarburization test shall be carried out according to the relevant requirements of GB/T 3098.1.
5.1.4 The thread ends of bolts and studs shall be chamfered, which shall meet the requirements of GB/T 2.
5.1.5 Fasteners made of carbon steel and structural alloy steel shall be blue treated, and fasteners made of stainless steel shall not be surface treated.
5.2 Heat treatment
5.2.1 The heat treatment requirements of hexagon head bolts or equal-length double end studs shall meet the requirements of GB/T 3098.1 or GB/T 3098.6.
5.2.2 The heat treatment requirements of full-thread studs shall be in accordance with those specified in Table 8.
Table 8 Heat treatment requirements of full-thread studs
Uniform numerical code Material designation Standard No. Heat treatment process Remarks
U12352 Q235A GB/T 700 Hot rolling —
U20352 35 GB/T 699 Normalizing —
A71402 40MnB GB/T 3077 Tempering and quenching Tempering temperature ≥550℃
A73402 40MnVB GB/T 3077 Tempering and quenching Tempering temperature ≥550℃
A20402 40Cr GB/T 3077 Tempering and quenching Tempering temperature ≥550℃
A30302 30CrMoA GB/T 3077 Tempering and quenching Tempering temperature ≥600℃
A30352 35CrMoA GB/T 3077 Tempering and quenching Tempering temperature ≥560℃
A30422 42CrMo GB/T 3077 Tempering and quenching Tempering temperature ≥580℃
A31352 35CrMoVA GB/T 3077 Tempering and quenching Tempering temperature ≥600℃
A31252 25Cr2MoVA GB/T 3077 Tempering and quenching Tempering temperature ≥620℃
A50402 40CrNiMoA GB/T 3077 Tempering and quenching Tempering temperature ≥520℃
S45110 12Cr5Mo GB/T 1221 Tempering and quenching Tempering temperature ≥650℃
S42020 20Cr13 GB/T 1220 Tempering and quenching —
S30408 06Cr19Ni10 GB/T 1220 Solid solution —
S31608 06Cr17Ni12Mo2 GB/T 1220 Solid solution —
S32168 06Cr18Ni11Ti GB/T 1220 Solid solution —
5.2.3 The heat treatment requirements of Style 1 nuts shall meet the requirements of GB/T 3098.2 or GB/T 3098.15.
5.2.4 The heat treatment requirements of Style 2 nuts shall be in accordance with those specified in Table 9.
Table 9 Heat treatment of Style 2 nuts
Uniform numerical code Material designation Standard No. Heat treatment process Remarks
U12352 Q235A GB/T 700 Hot rolling —
U20252 25 GB/T 699 Normalizing —
U20352 35 GB/T 699 Normalizing —
U21402 40Mn GB/T 699 Normalizing —
A30302 30CrMoA GB/T 3077 Tempering and quenching Tempering temperature ≥600℃
A30352 35CrMoA GB/T 3077 Tempering and quenching Tempering temperature ≥560℃
A31352 35CrMoVA GB/T 3077 Tempering and quenching Tempering temperature ≥600℃
A31252 25Cr2MoVA GB/T 3077 Tempering and quenching Tempering temperature ≥620℃
A50402 40CrNiMoA GB/T 3077 Tempering and quenching Tempering temperature ≥520℃
S45110 12Cr5Mo GB/T 1221 Tempering and quenching Tempering temperature ≥650℃
S42020 20Cr13 GB/T 1220 Tempering and quenching —
S30408 06Cr19Ni10 GB/T 1220 Solid solution —
S31608 06Cr17Ni12Mo2 GB/T 1220 Solid solution —
S32168 06Cr18Ni11Ti GB/T 1220 Solid solution —
5.2.5 The raw materials supplied in accordance with the heat treatment process in Table 8 or Table 9 may be directly processed into products for delivery under the premise of ensuring the mechanical properties of the products.
6 Inspection and acceptance
6.1 Inspection
6.1.1 The inspection shall be conducted in batches. Products with the same material designation, same smelting furnace number, same style, same thread specification, same length (except nuts) and same production process are a batch. When the length of bolts and studs is less than or equal to 100mm, those with a difference of not more than 25mm in length may be regarded as the same batch; when the length of bolts or studs is greater than 100mm, those with a difference of not more than 50mm in length may be regarded as the same batch. However, in a batch, the maximum number of bolts or studs is 3,000, and the maximum number of nuts is 5,000.
6.1.2 The dimension inspection shall meet the requirements of GB/T 90.1.
6.1.3 The surface defects of bolts and studs shall meet the requirements of GB/T 5779.1, and the surface defects of nuts shall meet the requirements of GB/T 5779.2.
6.1.4 The surface of fasteners shall not have transverse defects.
6.1.5 The outer surface of fasteners shall not have trimming burrs.
6.1.6 NDT and qualification grades of fasteners shall meet the requirements of the contract or relevant standards.
6.2 Acceptance
The acceptance of fasteners shall meet the requirements of GB/T 90.1.
Foreword II
1 Scope
2 Normative references
3 Structural styles, dimensions and tolerances
3.1 Hexagon head bolts
3.2 Equal-length double end studs
3.3 Full-thread studs
3.4 Hexagon nuts
3.5 Tolerances
3.6 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
Bibliography
