Ensure that seamless steel tube bending and straightening method

- Feb 11, 2019-

Seamless steel tube has been processed into a smaller degree of tortuosity also rely on mechanical things straightening machine to end.So in order to eliminate the twists and turns of seamless steel tubes, all seamless steel tubes are required to go through cold straightening.

The zigzag of seamless steel tube is caused by improper adjustment of rolling mill, residual stress during rolling and unevenness of cooling along the pipe section and length.Therefore, it is not possible to get very straight pipe directly from the mill, as long as the tortuosity of the cold straightening pipe can be satisfied with the rules of technical conditions.

The basic principle of straightening is to make seamless steel tube elasto-plastic tortuous, from large tortuous to small tortuous, so there is a need for steel tube in the straightening machine repeated tortuous.And the degree of repeated twists and turns of steel pipe is mainly determined by the adjustment of the straightener.There are many factors affecting the straightening quality, such as the original pipe tortuosity, steel pipe size and material straightening type, adjustment parameters and so on.



Cangzhou Steel Pipe Group (CSPG) Co., Ltd. is a large-sized, key metallurgic enterprise of Hebei Province in North China, whose history dates back to 1994. CSPG currently em/paces six member companies with products varying from SSAW, LSAW, ERW, seamless steel pipes to 3PE pipes, galvanized pipes, casing pipes, etc. A Joint-stock corporation, CSPG occupies an area of 600,000 square meters with a total asset of $530 million.

Specialized in the production of straight welded pipe spiral pipe galvanized pipe 3PE/3PP/FBE/TPEP internal and external epoxy powder internal and external epoxy resin cement mortar two cloth three oil buried pipeline IPN8710 non-toxic drinking water internal and external plastic coated lining plastic and other anti-corrosion pipe fittings for oil and gas pipeline water conservancy projects

Executive standard :DIN30670 DIN30678 CSA Z245 AFNOR nf49-710/711 NACE rp0394/0490 AWWAC 210/C213GB/T9711 API 5L ISO 3183Material: Q235B/Q355BGR A GR B x42-x80 l245-l555


Business scope: 21.3mm-3620mmLSAW submerged arc welded pipe 325-2020mmERW straight welded pipe 6mm-711mmSMLS seamless tube 10-1120mmSSAW spiral steel tube 219-3620mmDemand for quality suppliers and partners


Chemical composition(%)
Material numberMfg. ProcessC

Mechanical and technological properties
Code numberMaterial numberCold-finished hard(BK)Cold-finished/soft (BKW) 3)


St 35/E2351.0308480642010
St 451.040858055208
St 52/E3551.050864045807

Code numberCold finished (soft)(BKW)Annealed (GBK)Normalized (NBK)

Rm(Mpa)ReH (Mpa)A(%)Rm(Mpa)A(%)Rm (Mpa)ReH (Mpa)A(%)
St 35/E2354203151431525340-47023525
St 455203751239021440-57025521
St 52/E3555804501049022490-63035522

  • The yield point for the annealed (GBK)condition on delivery is at least 50% of the (ultimate) tensile strength.

  • Depending upon the degree of deformation in the drawing operation, the yield point of tubes delivered in the cold-finished/hard (BK)and cold-finished/soft(BKW) conditions, may be increased to a level close to the tensile strength.

  • In calculating the yield point, the following values are recommended : cold-finished/hard condition on delivery ≥ 80% of the tensile strength, cold-finished/soft condition on delivery ≥ 70% of the tensile strength.

Quality grade

The tubes are supplied in the following quality grades :

  • precision steel tubes intended primarily for mechanical stressing, without any particular quality requirement and without acceptance test certificate.

  • precision steel tubes intended primarily for mechanical stressing, with special quirement and exclusively with acceptance test certificate.

  • precision steel tubes with special requirement according to section 12. Theses requirements and corresponding tests must be agreed, with the customer having to specify his requirements at the time of enquiry and on ordering.

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.

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