This standard specifies the dimensions, shapes, technical requirements, acceptance rules, test methods, packaging, marking and quality certificates of high-quality carbon structural steel and alloy structural steel cold-drawn and polished steel. This standard applies to high-quality carbon structural steel, alloy structural steel round, square and hexagonal cold-drawn steel and polished round steel. GB/T 3078-1994 Technical conditions for high-quality structural steel cold-drawn steel GB/T3078-1994 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Technical reguirements for
quality structural steel cold drawn bars1 Subject content and scope of application
GB/T3078-94
Replaces GB 307R-82
This standard specifies the dimensions, appearance, technical requirements, acceptance rules, test methods, packaging, marking and quality certificates for high-quality carbon structural steel and alloy structural steel cold drawn and polished bars. This standard applies to high-quality carbon structural steel, alloy structural steel, square and hexagonal cold drawn bars and polished round bars. 2 Reference standards
GB 225
GB 228
GB 229
GB 699
Methods for sampling samples for chemical analysis and allowable deviations of chemical composition of finished products Chemical analysis methods for steel and alloys
Method for measuring the depth of decarburized layer of steel
Method for testing the permeability of steel by end-fire test
Method for testing macrostructure and defects of steel by acid etching Metal tensile test method
Metal Charpy (U-notch) impact test method Metal Brinell hardness test method
Metal forging test method
Metal ammonium nitride test method
Technical conditions for high-quality carbon structural steel
GE/T 905
GB 1814
GR1979
GB2101
GB2975
GB 3077
Dimensions, shapes, weights and permissible deviations of cold-drawn round steel, square steel and hexagonal steelFractometry of steel
Defect rating diagram of macrostructure of structural steel
General provisions for acceptance, packaging, marking and quality certificate of steel-shaped steelSampling provisions for mechanical and process performance tests of steelTechnical specifications for alloy structural steel
GB3207
Silver bright steel
GB6394
GB6397
GB7736
GB10561
Method for determination of average grain size of metal
Metal tensile test specimen
Macrostructure and defect of steelUltrasonic inspection method for microscopic evaluation of non-metallic inclusions in steelGB/T 13298
GB/T 13299
Method for testing microstructure
Method for evaluating microstructure
Approved by the Environmental Supervision Bureau on December 22, 1994 and implemented on October 1, 1995
3 Classification and code
GE/T307894
Steel is divided into 4 categories according to the processing purpose. The processing purpose should be indicated in the order contract. If it is not indicated, it is supplied as cutting steel. Non-cutting steel
Cutting steel
Hot pressing steel
Ring or hot forging steel
4 Dimensions and shape
4. 1 The dimensions, shape and allowable deviation of cold-drawn steel shall comply with the provisions of GB/T 905. 4.2 The dimensions, shape and allowable deviation of polished steel shall comply with the provisions of GB3207. 5 Technical requirements
5.1 Grade and chemical composition
5.1.1 The grade and chemical composition of steel, high-quality carbon structural steel shall comply with the provisions of GB699, and alloy structural steel shall comply with the provisions of GB3077.
5.1.2 According to the requirements of the purchaser, the chemical composition (melting analysis) of steel for cold heading forging shall comply with the provisions of Table 1; the allowable deviation of the chemical composition of finished steel shall comply with the provisions of Table 2 of GB 222. Table 1
Chemical composition, in addition
5.2 Delivery status
0.07~~0.13
0.12-0. 1B
0.17~~Q.24
0.27-~0. 34
0.32~0.39
0.37--0.44
0.42~~0. 49
0. 340. 42
not more than ten
0.50~0.80
0. 80--1. 10
Steel is delivered in the state of drawing or heat treatment (annealing, bright annealing, normalizing, high temperature annealing, tempering after normalizing). The delivery state of the steel shall be specified in the contract. If not specified, it shall be supplied in the cold-drawn state. 5.3 Mechanical properties
5.3.1 The hardness value of the steel delivered in the cold-drawn state, annealed, tempered at high temperature or tempered after normalizing shall comply with the provisions of Table 2; the hardness value of the steel delivered in the normalized state shall be agreed upon by the supply and demand parties.
5.3.1.1 The hardness values ​​of 50Mn2, 45CrVA, 35CrMnStA, 42CrMe, and 35CrMVA delivered in the cold-drawn state for heat and pressure processing shall comply with the provisions of Table 2. The Brinell hardness value of other grades delivered in the state shall not be greater than 269. 5.3. 1.2 For steels with a cross-sectional size of less than 5 mm, no hardness test shall be conducted or the hardness test shall be agreed upon by both parties. 5.3.2 According to the purchaser's requirements and as specified in Contract 4, the mechanical properties of the finished materials in the delivery state shall comply with the provisions of Table 3. For the brands not listed in Table 3, the mechanical properties of the samples made from heat-treated rough pieces shall comply with the provisions of GB699 for high-quality plain structural steel and GB3077 for alloy structural steel.
Delivery status.HB
27SiMn
35SiMn
42SiMn
Not more than
Tempering, high temperature tempering
or tempering after normalizing
40MnVH
ZOSMnVE
4DGrVA
45CrVA
38Crsi
20CtMnSiA
25CrMnSiA
30CiMnSiA
35CrMnSiA
20CrMnFi
15CtMo
|20CrMo
30CrMo
35CrMo
42CrMo
20CrMnMo
40CrMnMo
35CrMoVA
38CrMoAIA
Hardness in delivery state.HB
Not much lower
Annealing, high temperature tempering
or tempering after normalizing
20CINi
40CtNi
45CrNi
12CrNi2A
12CrNi3A
20CrNi3A
GE/T 3078—94
Continued Table 2
Hardness in changed state, HB
Not more than
Annealing, high temperature tempering
Tempering after normalizing
Tensile strength
Elongation
Not less than
30CrNi3(A)
37CrNi3A
12Cr2Ni4A
20Cr2Ni4A
40CrNiMoA||tt ||45CrNiMoVA
18Cr2Ni4wA
25Cr2Ni4WA
Tensile strength, core
Hardness in delivery state, HB
Not greater than
Elongation after annealing, high temperature tempering
or tempering after normalizing
, product
Not less than
Reduction rate,
5.3.3 The mechanical properties of cold forging steel delivered by annealing shall comply with the provisions of Table 4. The mechanical properties of grades not listed in Table 4 shall be agreed upon by the supply and demand parties. For steel with a cross-sectional size of less than 5mm, the hardness test shall not be carried out or shall be agreed upon by both parties. No.
GB/T 3078—94
Brinell strength
Not more than
Tensile strength +o
Not more than
Elongation
Not less than
Shrinkage
Not less than
5.4 Upset
5.4.1 Cold or hot upset steel (specified in the order contract) shall be subjected to cold or hot upset test. Cold upset test is to be forged to half of the original height of the specimen, and hot upset test is to be forged to one third of the original height of the specimen. 5.5 Macrostructure
5.5.1 When checking the macrostructure on the fracture of the transverse acid immersion test piece or braided annealing test piece of steel, there shall be no shrinkage residual, bubbles, cracks, peeling, inclusions and white spots.
5.5.2 The macrostructure assessment level of steel shall comply with the provisions of Table 5. Table 5
High-quality steel
High-quality steel
Special-grade high-quality steel
General loose
Central loose
Level, not more than
5.5.2.1 The segregation of 20CrMnSiA, 25CrMnSiA, 30CrMnSiA and 35CrMnSiA steels shall not be greater than Level 2.5. 5.5.2.2 The general pitting segregation and edge pitting segregation of 38CrMoAl and 38CrMoAlA shall not exceed Level 2. 5.5.3 The steel for cutting processing is allowed to have defects such as subcutaneous bubbles and subcutaneous inclusions that do not exceed the allowable depth of surface defects. 5.6 Decarburization
5.6.1 According to the requirements of the purchaser, the total decarburization layer (ferrite + transition layer) depth of cold-drawn round steel and cold-drawn annealed round steel with a carbon content greater than or equal to 0.30% (except for steel with a silicon content greater than or equal to 0.9% or an aluminum content greater than or equal to 0.7%) shall comply with the provisions of Table 6. For cold-drawn round steel with a diameter less than 6.5 mm, the total decarburization layer depth of one side shall not exceed a.1 mm. Table 6
Total decarburization layer depth of one side. mm
Cold drawing, light fading annealing
Note: ① d is the diameter of the tree +
②When a group is required, it should be specified in the contract. If not specified, the second provision shall be followed. Not more than
Effective party agreement
The decarburization layer of cold-drawn square steel, hexagonal steel, and round steel delivered by normalization shall be agreed upon by the supply and demand parties. 5.6.2
5.6.3 For steels with silicon content greater than or equal to 0.9% or aluminum content greater than or equal to 0.7%, the depth of decarburization layer shall be determined by agreement between the two parties. GB/T 307894
5.6.4 Decarburization layer is not allowed for steels delivered after polishing. With the consent of the belt party, the total decarburization layer depth on one side of the polished steel may not exceed 1.0%d. 5.7 Surface quality
5.7.1 The surface of the steel shall be clean and smooth, and no cracks, folds, scars, inclusions, rips and scale shall be allowed. The surface of the cold-drawn steel after heat treatment is allowed to have oxidation color.
5.7.2 For materials used for cutting, the surface is allowed to have pits, scratches, pull marks, black spots, concave surfaces, cleaning oblique marks, lubricant marks and individual small hairlines with a depth of half the tolerance not exceeding the nominal size tolerance calculated from the actual size. 5.7.3 For non-cutting steel, hot pressure processing and upsetting steel, the surface is allowed to have individual scratches, pull marks, black spots, concave surfaces, pits and cleaning oblique marks with a depth not exceeding the minimum tolerance of the nominal dimension from the actual size. According to the requirements of the purchaser, the depth of the above defects may not exceed one-half of the tolerance.
5.7.4 The surface of the polished delivered materials shall not have defects. 5.7.5 The surface of the steel straightened by the inclined roller is allowed to have thread-shaped roller marks. 5.7.6 The surface quality of cold-drawn square steel and angle steel shall comply with the provisions for cutting steel. 5.8 Special requirements
According to the requirements of the purchaser, the following steels with special requirements can be supplied after agreement between the supply and demand parties, and the qualified standards shall be agreed by the supply and demand parties. 9.
Narrow the chemical composition range;
Impact toughness of steel in the delivery state
Specify the upper and lower limits of mechanical properties;
Layered fracture;
Magnetic structure:
Grain size:
Reduced permeability:
Non-metallic inclusions:
Forging flatness test for 10F, 15F, 20F materials for cold top forging: surface roughness;
Non-destructive testing.
6 Test methods
The test methods for each batch of steel products shall comply with the provisions of Table 7. Table 7
Inspection items
Chemical composition
Strength test
Tensile test
Stainless steel
Macrostructure
Fractograph
Sampling number
Upper/lower
Steel with different branches
Sampling requirements
GB2975 steel with different branches
GB2975 steel with different branches
Unsupported steel
Different steel with different branches equivalent to the head of the ingot
Different steel with different branches
GH 231
GB6397
GH 228
Test method
Sample R4
GB 226GB 7736GB1979
GB 1814
Inspection items
Decarburized layer
Grain size
Permeability
Non-disease head
Forging test
7 Inspection rules
7.1 Batch test
Sampling requirements
GB/T3078—94
Continued table 7
Sampling requirements
Steel materials with different supports
Unsupported steel
Unsupported steel
Steel materials with different supports
Unsupported steel
Unsupported steel
GR 224
Test force method
GI3/T 11298.G13/T 11209
GB6394
GB10561
Dry scale, sample
Furnace number, same size, same processing state and same heat treatment extension (same for continuous furnace). 1.1 Steels should be tested in batches, and each batch consists of steels with the same heat treatment system.
7.1.2 Electro-hydraulic steel can be batched according to the mother furnace number of electric drive furnace steel under stable process. 7.2 Sampling quantity and requirements
7.2.1 The sampling quantity and requirements of each batch of steel shall comply with the provisions of Table 7. For electro-hydraulic steel, except for 5 hardness specimens and 2 acid leaching low-magnification entanglement specimens (sampled at the head and tail of the steel key), 1 specimen shall be taken for each test. 7.2.2 When electroslag steel is batched according to the arc furnace steel mother furnace number, the sampling quantity shall be in accordance with the provisions of Article 7. 7.3 Re-inspection and judgment rules
The inspection and judgment rules for steel materials shall comply with the provisions of GB 2101. 8
Packaging, marking and quality certificates
The packaging, marking and quality certificates of steel materials shall comply with the provisions of GB2101. Additional notes:
This standard is proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard is under the jurisdiction of the Information Standards Research Institute of the Ministry of Metallurgical Industry. This standard was drafted with the funding of Chongqing Special Steel Company and the Information Standards Research Institute of the Ministry of Metallurgical Industry. The main drafters of this standard are Li Suqin, Xu Maojun, Qi Baolan and Zhang Changsen. The water grade mark of this standard: GB/T3078-9413 For non-cutting steel, hot pressure processing and upsetting steel, the surface is allowed to have individual scratches, pull marks, black spots, concave surfaces, pitting and cleaning oblique marks with a depth not exceeding the minimum tolerance of the nominal dimension from the actual size. According to the requirements of the purchaser, the depth of the above defects may not exceed one-half of the tolerance.
5.7.4 The surface of the polished delivered materials shall not have defects. 5.7.5 The surface of the steel straightened by the inclined roller is allowed to have thread-shaped roller marks. 5.7.6 The surface quality of cold-drawn square steel and angle steel shall comply with the provisions for cutting steel. 5.8. Special requirements
According to the requirements of the purchaser, the following steels with special requirements can be supplied after agreement between the supply and demand parties, and the qualified standards shall be agreed by the supply and demand parties. 9.
Narrow the chemical composition range;
Impact toughness of steel in the delivery state
Specify the upper and lower limits of mechanical properties;
Layered fracture;
Magnetic structure:
Grain size:
Reduced permeability:
Non-metallic inclusions:
Forging flatness test for 10F, 15F, 20F materials for cold top forging: surface roughness;
Non-destructive testing.
6 Test methods
The test methods for each batch of steel products shall comply with the provisions of Table 7. Table 7
Inspection items
Chemical composition
Strength test
Tensile test
Stainless steel
Macrostructure
Fractograph
Sampling number
Upper/lower
Steel with different branches
Sampling requirements
GB2975 steel with different branches
GB2975 steel with different branches
Unsupported steel
Different steel with different branches equivalent to the head of the ingot
Different steel with different branches
GH 231
GB6397
GH 228
Test method
Sample R4
GB 226GB 7736GB1979
GB 1814
Inspection items
Decarburized layer
Grain size
Permeability
Non-disease head
Forging test
7 Inspection rules
7.1 Batch test
Sampling requirements
GB/T3078—94
Continued table 7
Sampling requirements
Steel materials with different supports
Unsupported steel
Unsupported steel
Steel materials with different supports
Unsupported steel
Unsupported steel
GR 224
Test force method
GI3/T 11298.G13/T 11209
GB6394
GB10561
Dry scale, sample
Furnace number, same size, same processing state and same heat treatment extension (same for continuous furnace). 1.1 Steels should be tested in batches, and each batch consists of steels with the same heat treatment system.
7.1.2 Electro-hydraulic steel can be batched according to the mother furnace number of electric drive furnace steel under stable process. 7.2 Sampling quantity and requirements
7.2.1 The sampling quantity and requirements of each batch of steel shall comply with the provisions of Table 7. For electro-hydraulic steel, except for 5 hardness specimens and 2 acid leaching low-magnification entanglement specimens (sampled at the head and tail of the steel key), 1 specimen shall be taken for each test. 7.2.2 When electroslag steel is batched according to the arc furnace steel mother furnace number, the sampling quantity shall be in accordance with the provisions of Article 7. 7.3 Re-inspection and judgment rules
The inspection and judgment rules for steel materials shall comply with the provisions of GB 2101. 8
Packaging, marking and quality certificates
The packaging, marking and quality certificates of steel materials shall comply with the provisions of GB2101. Additional notes:
This standard is proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard is under the jurisdiction of the Information Standards Research Institute of the Ministry of Metallurgical Industry. This standard was drafted with the funding of Chongqing Special Steel Company and the Information Standards Research Institute of the Ministry of Metallurgical Industry. The main drafters of this standard are Li Suqin, Xu Maojun, Qi Baolan and Zhang Changsen. The water grade mark of this standard: GB/T3078-9413 For non-cutting steel, hot pressure processing and upsetting steel, the surface is allowed to have individual scratches, pull marks, black spots, concave surfaces, pitting and cleaning oblique marks with a depth not exceeding the minimum tolerance of the nominal dimension from the actual size. According to the requirements of the purchaser, the depth of the above defects may not exceed one-half of the tolerance.
5.7.4 The surface of the polished delivered materials shall not have defects. 5.7.5 The surface of the steel straightened by the inclined roller is allowed to have thread-shaped roller marks. 5.7.6 The surface quality of cold-drawn square steel and angle steel shall comply with the provisions for cutting steel. 5.8. Special requirements
According to the requirements of the purchaser, the following steels with special requirements can be supplied after agreement between the supply and demand parties, and the qualified standards shall be agreed by the supply and demand parties. 9.
Narrow the chemical composition range;
Impact toughness of steel in the delivery state
Specify the upper and lower limits of mechanical properties;
Layered fracture;
Magnetic structure:
Grain size:
Reduced permeability:
Non-metallic inclusions:
Forging flatness test for 10F, 15F, 20F materials for cold top forging: surface roughness;
Non-destructive testing.
6 Test methods
The test methods for each batch of steel products shall comply with the provisions of Table 7. Table 7
Inspection items
Chemical composition
Strength test
Tensile test
Stainless steel
Macrostructure
Fractograph
Sampling number
Upper/lower
Steel with different branches
Sampling requirements
GB2975 steel with different branches
GB2975 steel with different branches
Unsupported steel
Different steel with different branches equivalent to the head of the ingot
Different steel with different branches
GH 231
GB6397
GH 228
Test method
Sample R4wwW.bzxz.Net
GB 226GB 7736GB1979
GB 1814
Inspection items
Decarburized layer
Grain size
Permeability
Non-disease head
Forging test
7 Inspection rules
7.1 Batch test
Sampling requirements
GB/T3078—94
Continued table 7
Sampling requirements
Steel materials with different supports
Unsupported steel
Unsupported steel
Steel materials with different supports
Unsupported steel
Unsupported steel
GR 224
Test force method
GI3/T 11298.G13/T 11209
GB6394
GB10561
Dry scale, sample
Furnace number, same size, same processing state and same heat treatment extension (same for continuous furnace). 1.1 Steels should be tested in batches, and each batch consists of steels with the same heat treatment system.
7.1.2 Electro-hydraulic steel can be batched according to the mother furnace number of electric drive furnace steel under stable process. 7.2 Sampling quantity and requirements
7.2.1 The sampling quantity and requirements of each batch of steel shall comply with the provisions of Table 7. For electro-hydraulic steel, except for 5 hardness specimens and 2 acid leaching low-magnification entanglement specimens (sampled at the head and tail of the steel key), 1 specimen shall be taken for each test. 7.2.2 When electroslag steel is batched according to the arc furnace steel mother furnace number, the sampling quantity shall be in accordance with the provisions of Article 7. 7.3 Re-inspection and judgment rules
The inspection and judgment rules for steel materials shall comply with the provisions of GB 2101. 8
Packaging, marking and quality certificates
The packaging, marking and quality certificates of steel materials shall comply with the provisions of GB2101. Additional notes:
This standard is proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard is under the jurisdiction of the Information Standards Research Institute of the Ministry of Metallurgical Industry. This standard was drafted with the funding of Chongqing Special Steel Company and the Information Standards Research Institute of the Ministry of Metallurgical Industry. The main drafters of this standard are Li Suqin, Xu Maojun, Qi Baolan and Zhang Changsen. The water grade mark of this standard: GB/T3078-941
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