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National standard for precision seamless steel pipes for cold drawing or cold rolling
1. Scope
This standard specifies the classification and code, size, shape, weight and allowable deviations, technical requirements, experimental methods, inspection rules, packaging, marking and quality certificates of cold or cold-rolled precision seamless steel pipes.
This standard is applicable to the manufacture of cold-drawn or cold-rolled precision seamless steel pipes with special dimensional accuracy and high surface quality requirements for mechanical structures, hydraulic equipment, and automobiles.
2. Reference standards
3. Classification and code name
Steel pipes are divided according to delivery status (codes in parentheses): cold worked/hard (BK), cold worked/soft (BKW), stress relief annealed after cold working (BKS), annealed (GBK), and normalized (NBK).
4. Dimensions, appearance, weight and allowable deviations
4.2 Length
4.2.1 Common length
The general length of steel pipe is 2000-7000mm.
4.2.2 Fixed length and multiple lengths
The fixed length and multiple lengths of the steel pipe should be within the normal length range, and the allowable deviation of the full length must comply with the following regulations:
Length 5000mm
Length 5000mm
For steel pipes delivered in multiple lengths, a notch margin should be left for each multiple length in accordance with the following provisions:
Outer diameter 159mm 5-10mm
Outer diameter 159mm 10-15mm
4.2.3 According to the requirements of the buyer, other steel pipes with acceptable deviations can be provided after negotiation between the supplier and the buyer, and it is specified in the contract.
4.3 Curvature
The curvature of steel pipes in the cold worked/hard (BK) state and cold worked/soft (BKW) state should not be greater than 3.0mm/m; the curvature of steel pipes in the stress relief annealed (BKS) state, annealed (GBK) state, and normalized (NBK) state after cold working should not be greater than 1.5mm/m.
4.4 Terminal shape
The end faces of both ends of the steel pipe should be perpendicular to the axis of the steel pipe, and the cut burrs should be removed.
4.5 Oval and uneven wall thickness
4.5.1 The ovality of the steel pipe should not be greater than 80% of the outer diameter tolerance
4.5.2 According to the requirements of the buyer, the uneven wall thickness of the steel pipe shall be negotiated by the supplier and the buyer.
 High precision cold drawn tube Click to view product details |
 Honing tube Click to view product details |
4.6 Weight
The delivery weight of steel pipes should comply with the regulations of GB/T17395. The density of steel is 7.85kg/dm.
When the steel pipe is delivered with a theoretical weight, according to the requirements of the buyer, after negotiation between the supplier and the buyer, and indicating in the contract, the allowable deviation between the actual weight of the delivered steel pipe and the theoretical weight should comply with the following regulations:
Single steel pipe ; Each batch of steel pipes is at least 10 tons
4.7 Mark list
Cold-rolled precision seamless steel pipes made of No. 20 steel with an outer diameter of 50mm and an inner diameter of 30mm, cold-worked/hardened, are marked: Finish-rolled 20-50*30BK-GB/T3639-2008
Cold-rolled precision seamless steel pipes made of No. 10 steel with an outer diameter of 38mm, wall thickness of 3mm, fixed length of 5000mm, cold working/soft state, are marked:
Finish rolling 10-38*3*5000BKW-GB/T 3639-2008
Cold-drawn precision seamless steel pipes made of No. 35 steel with an inner diameter of 30mm, a wall thickness of 2mm, and a multi-scale length of 1800mm in a stress-relieving annealed state are marked: fine drawn 35-inner 30*2*1800 times BKS-GB/T3639-2000
5 Technical requirements
5.1 Steel grades and chemical composition
5.1.1 Steel pipes are made of 10/20/35 and 45 steel, and their chemical composition should comply with the regulations of GB/T 69. Steel pipes are accepted according to their melting composition.
5.1.2 When the purchaser requires finished product analysis, it should be stated in the contract. The allowable deviation of the chemical composition of finished steel pipes shall comply with the provisions of GB/T 222.
5.1.3 According to the requirements of the buyer and through negotiation between the supplier and the buyer, other grades of high-quality carbon structural steel and alloy structural steel pipes are available.
5.2 Manufacturing method
5.2.1 The smelting method of steel is selected by the manufacturer.
5.2.2 Round tube blanks should comply with the requirements of YB/T 5222.
5.2.3 Steel pipes are manufactured by cold drawing or cold rolling. When the demander specifies a certain method for manufacturing steel pipes, it should be stated in the contract.
5.3 Delivery status