Hot rolled carbon square tube and cold formed steel hollow section square pipe is a process, they have a great impact on the microstructure and properties of steel, rolled steel, hot-rolled mainly based, only for the production of cold-rolled trumpet steel and sheet.

Hot-rolled

Pros: You can destroy ingot casting organizations, 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.

Disadvantages: After hot rolling, the hot rolled square hollow section steel pipe inside the non-metallic inclusions (mainly sulphide and oxide, and silicates) is pressed into the sheet, delamination (interlayer) phenomenon. Layered in the thickness direction of the steel tension performance deteriorated significantly, and there may be an interlayer tear weld shrinkage. Weld local strain-induced contraction of the yield point strain often reach several times larger than the load caused by the strain.

Cold-rolled

Advantages: forming speed, high yield, and does not damage the coating, can be made into a variety of cross-sectional form, needs to adapt to the conditions of use; cold-rolled steel to produce large plastic deformation, thereby increasing the yield of steel point.

Disadvantages: 1 Although the molding process without thermal plastic compression, but there are still residual stress within the cross-section of the overall and local buckling characteristics of steel will inevitably have an impact;

2 Cold formed square steel pipe style is generally open section, so that the free section. low torsional stiffness. When flexural prone to twisting, bending and torsion when the pressure is prone to buckling, torsional performance is poor;