GB/T 3639 Cold-Drawn Or Cold-Rolled Precision Seamless Tubes

GB/T 3639 Grade 10、20、35、45、Cold-drawn or cold-rolled precision seamless tubes
 
Standard: GB/T 3639
This standard is applicable to the manufacture of mechanical structures, hydraulic equipment, automotive cold-drawn or cold-rolled precision seamless steel tubes with special dimensional accuracy and high surface quality requirements.
 
Main grades:
Grade 10, Grade 20, Grade 35, Grade 45
 
 
GB/T 3639 Cold-drawn or cold-rolled precision seamless tubes Quick Details
Company Name: Beite steel pipe
Country/Region: China
Main grades: Grade 10, Grade 20, Grade 35, Grade 45
FOB Price: US $900-1500 / Ton | 1 Ton/Tons (Min. Order)
Delivery Status: +BK, +BK W, +BK S, +GBK, +NBK
Port of Shipment: Tianjin, China
Payment: L/C or T/T
Delivery: 7-15 days after payment
Package:Standard export package,suit for all kinds of transport, or as required
Certificate: ISO 9001-2000, PED 97/23/EC, ASME, DNV
 
GB/T 3639 Cold-drawn or cold-rolled precision seamless tubes Dimensional Range & Specification
Outside Diameter: 4.0mm - 200.0mm
Wall thickness: 3.0mm - 12.5mm
Length: 6000mm, 12000m or specified length as required.
 

Manufacturing
The steel pipe is manufactured by cold drawn or cold rolled.
 
 
Steel pipe according to delivery status:
Cold working / hard (BK), cold working / soft (BK W), stress relief annealing after cold working (BK S), annealing (GBK), normalizing (NBK).

Delivery status	Code	Description
Cold working / hard	B K	After the final cold working, no heat treatment is performed, so that the tube can only be deformed very little.
Cold working / soft	B K W	After the final heat treatment, a small amount of cold working is performed to allow limited cold deformation (for example, bending and flaring) when the steel pipe is reworked.
Stress relief annealing after cold working	B K S	After cold working, it is annealed below the Acl point to eliminate cold working stress.
Annealing	G B K	After the final cold working, the steel tube is completely annealed under a protective gas
Normalizing	N B K	After the final cold working, the normalizing of the steel pipe under protective gas

 

 
Chemical composition of GB/T 3639

No.	Uniform numeric code	Designation	Chemical composition (mass fraction)/%
			C	Si	Mn	P	S	Cr	Ni	Cu a
						≤
2	U20102	10	0.07~0.1 3	0.17~0.37	0.35~0.65	0.035	0.035	0.15	0.30	0.25
4	U20202	20	0.17~0.23	0.17~0.37	0.35~0.65	0.035	0.035	0.25	0.30	0.25
7	U20352	35	0.32~0.39	0.17~0.37	0.50~0.80	0.035	0.035	0.25	0.30	0.25
9	U20452	45	0.42~0.50	0.17~0.37	0.50~0.80	0.035	0.035	0.25	0.30	0.25
Any element not specified in this table shall not be added without agreement of the users. Measures shall be taken to prevent steel scrap or other materials from bringing in element which influences performance of steels.
a  Copper content for steel used for hot press working shall not be greater than 0.20%;

 

Physical properties of GB/T 3639

Grade	Delivery status
	B K		B K W		B K S		G BK		N B K
	Tensile strength, Mpa	Elongation, %	Tensile strength, Mpa	Elongation, %	Tensile strength, Mpa	Elongation, %	Tensile strength, Mpa	Elongation, %	Tensile strength, Mpa	Yield Strength	Elongation, %
	≥
10	410	6	375	10	335	12	335	24	335	205	24
20	510	5	450	8	430	10	390	20	410	245	20
35	590	4	550	6	520	8	510	17	530	315	17
45	645	4	630	5	610	7	590	14	600	355	14
Note: For steel pipes with an outer diameter of not more than 30 mm and a wall thickness of more than 3 mm, the minimum yield point can be reduced by 10 MPa.

 
 

The end of Precision seamless steel pipe
The end faces of the steel pipe should be perpendicular to the axis of the steel pipe, and the burrs of the cut should be removed.
 
 
Testings:
Dimensional inspection: The size and shape of the steel pipe are measured and inspected one by one using a measuring tool that meets the accuracy.
Surface quality: The inner and outer surfaces of the steel pipe shall be visually inspected one by one under conditions of sufficient illumination.
Chemical composition: Take 1 sample per furnace number for chemical composition testing.
Tensile test: Take 1 sample per batch for tensile test.
Compactness test: The GB/T 3639 steel pipe is tested one by one
Surface roughness inspection: Each sample is taken on each of 2 steel pipes for inspection.
 


 
Tag example
Cold-rolled precision seamless steel pipe made of 20 steel with an outer diameter of 50 mm and an inner diameter of 30 mm, cold worked/hard state, marked as:
Finishing 20-∅50X ∅ 30BK-GB/T 3639- 2017

Cold-rolled precision seamless steel pipe made of 10 steel with an outer diameter of 38 mm, a wall thickness of 3 mm and a length of 5 000 mm, cold worked/soft state, marked as:
Finishing 10-∅38 X 3 X 5000BKW-GB/T 3639- 2017
 
Cold drawn precision seamless steel pipe made of 35 steel with an inner diameter of 30 mm, a wall thickness of 2 mm and a length of 1 800 mm, and a stress-relieving annealing state, marked as:
Fine extraction 35- inner ∅30 X 2 X 1 800  BKS-GB/T 3639- 2017