Precision steel tube is a kind of seamless steel tube with high precision and high brightness produced by cold drawing or cold rolling. Its inside and outside diameter size can be accurate to less than 0.01mm, and it is widely used in the manufacture of precision machinery parts and engineering structure when the bending resistance and torsion strength are the same. It is also used to produce all kinds of conventional weapons, guns, shells, bearings and so on.

General use seamless steel pipe is with 10, 20, 30, 35, 45 and other high-quality carbon steel, 16Mn, 5MnV and other low-alloy structural steel or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other composite steel hot-rolled or cold rolled. 10, 20 and other low carbon steel seamless steel pipe, mainly used for fluid transmission pipeline. 45. Seamless tubes made of medium carbon steel such as 40Cr, used for the manufacture of mechanical parts, such as parts of automobiles and tractors. General use of seamless steel pipe to ensure the strength and flattening test. Hot rolled steel tubes are delivered in hot rolling or heat treated conditions. Cold rolled is delivered in hot and heat treated conditions. Low and medium pressure boiler seamless pipe: used in the manufacture of a variety of low and medium pressure boiler, superheated steam pipe, water pipe, superheated steam pipe, water wall tube and locomotive boiler flue tube, pipe and pipe arch bricks.

Advantages: it can destroy the casting structure of steel ingot, refine the grain of steel, and eliminate the defects of microstructure, so that the steel structure is compact and the mechanical properties are improved. This improvement is mainly reflected along the rolling direction, so that steel is no longer a certain extent, isotropic body; casting formed when bubbles, cracks and loose, can also be welded under high temperature and pressure.

Disadvantages: 1., after hot rolling, the non-metallic inclusions (mainly sulfide and oxide, and silicate) inside the steel are compressed into flakes, and delamination (interlayer) occurs. Delamination results in deterioration of the tensile properties of the steel in the thickness direction and is likely to occur as a result of interlaminar tearing when the weld is contracted. The local strain induced by weld shrinkage often reaches several times of the strain at the yield point, much larger than the strain caused by the load; 2., the residual stresses due to uneven cooling. The residual stress in the external force is no internal stress self balanced, hot-rolled steel section with the residual stress, general steel section size is larger, the greater the residual stress. Although the residual stress is self balanced, it has certain influence on the performance of steel members under external force. Such as deformation, stability, fatigue and other aspects may have an adverse effect. 3. hot-rolled steel products, for the thickness and width of this aspect is not good control. We are familiar with expansion and contraction, because the beginning of the hot-rolled out, even if the length and thickness are up to standard, and finally cooling down or there will be a certain negative difference.