Seamless Precision steel tubes

DIN 2391-1 Cold Drawn or Cold Rolled Steel Tube

The seamless precision steel tubes can be used for a wide range of precision mechanical spare for car and cylinder accord to standard:

Manufacturing method: cold-rolled / cold-drawn

Delivery condition: BK,BKS,SR,GBK,NBK.


Packing: in bundles tied with steel strips.

External packing by wooden cases if the wall thickness/OD ratio is low.

Oil-coating is generally necessary especially for export.

Material: ST35,ST45,ST52.

Application: Used in hydraulic & pneumatic cylinder ,automobile and other mechanical device.


high precision and high brightness, the inner and outer surface of the tubes have high cleanness without oxid, mechanical properties of the final tubes also come out excellent, promising no leakage under high pressure, no deformation after cold-bent and no cracks when flaring and flattening, ensuring the efficient operation in all service.

NBK means protective heat-treating under the non-oxidation enviroment to get a bright and smooth surface for the tubes. ?

DIN 2391-81 Part 2 Seamless Precision steel tubes(DIN2391-81)

Standard DIN 2391 defines the technical delivery conditions for seamless precision steel tubes according to DIN 2391 Part 1 which are made from the steel grades listed in section 5.

Tubes according to this Standard are mainly used where accuracy to dimension and, possibly, small wall thicknesses and good surface condition are required.

Chemical composition(%)
Material number Mfg. Process C
St35 1.0308 S 0.17 0.35 0.4 0.05 0.05
St45 1.0408 S 0.21 0.35 0.4 0.05 0.05
St52 1.0508 S 0.22 0.55 1.6 0.05 0.05

Mechanical and technological properties
Code number Material number Cold-finished hard(BK) Cold-finished/soft (BKW) 3)
Rm(Mpa) A(%) Rm(Mpa) A(%)
St 35/E235 1.0308 480 6 420 10
St 45 1.0408 580 5 520 8
St 52/E355 1.0508 640 4 580 7

Code number Cold finished (soft)(BKW) Annealed (GBK) Normalized (NBK)
Rm(Mpa) ReH (Mpa) A(%) Rm(Mpa) A(%) Rm (Mpa) ReH (Mpa) A(%)
St 35/E235 420 315 14 315 25 340-470 235 25
St 45 520 375 12 390 21 440-570 255 21
St 52/E355 580 450 10 490 22 490-630 355 22

Quality grade

The tubes are supplied in the following quality grades :

Tech & Service of Seamless pipe

Seamless pipes are extensively applied for the nuclear device, gas, petrochemical, ship building and boiler industries. Seamless pipes dominates 65% of market share in Chinese boiler industry.

How to make seamless pipe(seamless pipe process)?
Hot Piercing Workshop
Piercing process
The cross roll piercing and pilger rolling process in the size range from approx. 250 to 660 mm outside diameter.
Precision cold drawn steel tube production process
Pipe weld cracks
often follow different mechanisms can be divided into two types of thermal cracking and cold cracking.
How to calculate a steel pipe and tube theoretic weight
Calculate a steel pipe?
Pipe fittings are necessary to join together pipes, or to change the direction of an existing pipe.
Pipe beveling
Pipe beveling is the process where an angle is formed between the edge of the end of a pipe or tube and a plane perpendicular to the surface.
Steel pipe cutting machine
Pipe cutting
Cutting tools have a grinding wheel piece cutting machine (also known as toothless saw), hand saw, cutter and other hand tools.
How to calculate a steel pipe and tube theoretic weight
Packing the steel pipes
There are probably hundreds of different methods for packing a pipe, and most of them have merit, but there are two principles that are vital for any method.

Condition on delivery:

(cold-finished as-drawn)


No heat treatment after the last cold-forming process. The tubes therefore have only low deformability.

(lightly cold-worked)
After the last heat treatment there is a light finishing pass (cold drawing) With proper subsequent processing, the tube can be cold-formed (e.g. bent, expanded) within certain limits.
After the final cold-forming process the tubes are annealed in a controlled atmosphere or under vacuum.
The tubes are annealed above the upper transformation point in a controlled atmosphere or under vacuum.

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