Seamless steel tube, the very important role in the national economy, is a kind of economic cross-section steel. It is widely applied in many departments such as petroleum, chemical industry, boiler, power stations, ships, machinery manufacturing, automobile, aviation, aerospace, energy, geology, architecture and military industry and so on.
(1)According to the cross-section shape: circular cross-section pipe, special-shaped cross-section pipe.
(2)According to the material: carbon steel pipe, alloy steel pipe, stainless steel pipe, composite pipe.
(3)According to the connection ways: threaded pipe, welded pipe.
(4)According to the mode of production: hot rolling (squeeze, top, expand), cold rolling (pull out).
(5)According to utility: boiler tube,
OCTG pipe, pipeline, structural pipe, chemical fertilizer pipe.
(1) The steel chemical composition: the chemical composition of steel is one of the most main factors that affect the performance of seamless steel tube, and it is also the main basis that formulates process parameters about rolled tube and heat treatment process of steel tube.
A. Alloy elements: put them according to the purpose
B. Residual elements: put them and properly control when steeling
C. The harmful elements: strictly control (As, Sn, Sb, Bi, Pb), gas (N, H, O)
(2) The precision and shape of steel pipe geometry size
A. Precision of steel pipe outer diameter: it depends on the order (reduction) diameter method, the working condition of the equipment, technological system, etc.
Permissible deviation of outside diameter: δ=(D-Di)/Di ×100% D: maximum or minimum mm
Di: nominal outer diameter mm
B. The wall thickness precision of steel tube: it is related with pipe billet heating quality, process design and adjusting parameters of each deformation process and tool quality and the quality of lubrication and so on.
Allowable deviation of wall thickness: ρ=(S-Si)/Si×100% S: maximum or minimum wall thickness on the cross section
Si: nominal wall thickness mm
C. Ovality of steel pipe: it means the degree of out of round steel tube.
D. Length of steel tube: normal length, fixed (multiple) length, length of allowable deviation
E. Bending of steel tube: it indicates steel radial degrees: length of per meter steel tube bending, bending of the compete steel tube length
F. Transverse cutting slope of steel pipe: steel pipe end face and the level of tilt of the pipe cross section.
G. Steel pipe transverse groove angle and the blunt edge.
The surface is bright and clean.
A. Dangerous defects: crack, folding inside, folding outside, abscission, scarring, etc.
B. General defects: pockmark, scratch, bruise, roll marks, etc.
