Seamless Precision tube

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

DIN 2391-1 Cold Drawn or Cold Rolled Steel Tube

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.

Main characteristics of precision seamless pipe:

inside and outside wall of steel pipe with high-precision, high-quality finish, after heat-treated, steel pipe without oxide layer, the inner wall with cleanliness, steel to withstand high pressure, not deformation of the cold bending, flaring, flattening without cracks, for a variety of complex deformation and machiningtreatment.

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 :

Precision seamless tubes features and usage

Piercing is the first step of hot-rolled seamless steel pipe deformation, and its role is to solid hollow tube billet dressed as capillary.

"The whole concept of finned tubes is to
increase the outside surface area of the tube.”

The rate at which such heat transfer can occur depends on three factors:

(1) the temperature difference between the two fluids;

(2) the heat transfer coefficient between each of the fluids and the tube wall;

(3) the surface area to which each fluid is exposed. In the case of a bare (unfinned) tubes, where the outside surface area is not significantly greater than the inside surface area, the fluid with the lowest heat transfer coefficient will dictate the overall heat transfer rate.

U-tube heat exchanger

Piercing is the first step of hot-rolled seamless steel pipe deformation, and its role is to solid hollow tube billet dressed as capillary.

Due to wear a capillary surface defects or eccentric (uneven thickness) is difficult to eliminate or reduce the deformation process, therefore, the quality of perforated capillary has a very important impact on the quality of hot-rolled seamless steel pipe. Way pressure tube perforation punching, pushing rotary piercing and piercing. Thick-walled seamless steel mainly used in petroleum geology drilling pipe, petrochemical used in cracking tubes, boiler tubes, pipes and automotive bearings, tractors, aviation and other precision tube structure, its manufacturing process: hot rolled seamless steel tube round → heating → three perforated roll rolling, rolling or extrusion → detached → sizing (or reducing) cooling → straightening → ​​hydrostatic test (or testing) logo → storage.

Hot-rolled seamless steel ingot casting can destroy tissue, grain refinement of steel and eliminate defects microstructure, so that the steel dense tissue mechanical properties are improved. This improvement is mainly reflected in the direction along the rolling direction to a certain extent in the steel is no longer isotropic; pouring formed bubbles, cracks and loose, can be welded at a high temperature and pressure.

After hot-rolled seamless steel tube round baked to go through the pressure puncher piercing. Generally more common punch is tapered roller punching machine, punching machine such high production efficiency, product quality, perforated expanding capacity, can be worn a variety of steel. After perforation, round tube has been three-roll rolling, rolling or extrusion. To squeeze off the pipe after sizing. Sizing mill into high-speed rotating cone drill through perforated steel embryo formed steel. Pipe inside diameter is determined by the outside diameter sizing mill drill length.

After sizing the pipe into the cooling tower through spray cooling pipe after cooling, it is necessary to be straightened. After straightening the steel conveyor belt to the metal detection machine (or pressure test) for internal testing. If the internal pipe cracks, bubbles and other issues, will be detected. After the selection of steel but also through strict quality control manual.

After the steel quality, spray paint on number, size, batch number and so on. By a crane into the warehouse.

Drawing process of precision seamless tube

Ultrasonic detector gas leak detection system is different from the specific design of the sensor to sense that it is limited to a specific gas, but rather to detect sound.

Ultrasonic focusing on industrial leak detection, leak detection and predictive maintenance, products and solutions in steel and non-ferrous metals, tobacco and food and beverage, automotive, chemical and oil and gas, mining and cement, glass manufacturing, electricity and cleaning system, military, paper and printing, rail transport, water treatment, infrastructure, subway fan and large air conditioning systems, port automation, and many other industries are widely used.

Drawing process of precision seamless tube detection method can leak air, gas, steam and liquids pipeline and a variety of equipment to be checked. If the ultrasonic generator and attached with the use, but also on the refrigerator, sealed container, air conditioning systems, tires, compressor and various fluids, such as sealed state pipeline inspection, improving the environment, a powerful tool for saving energy.

Steel Tube

Steel tube is including seamless steel tube and seamed steel tube. Steel tube which has a hollow cross-section is widely used for transportation of fluids, such as oil, gas, water, some solid materials and so on.

Steel tube is lighter than steel bar if both of them have the same torsional strength in bending. Steel tube is a kind of economic steel which has a hollow cross-section. It is widely used for transportation of fluids, such as oil, gas, water, some solid materials and so on as well as the manufacture of structural parts and mechanical parts, such as oil drill pipe, automotive drive shafts, bicycle frame, bearing sleeves, etc.

Seamless pipe Specification, standard and identification

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.


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