Seamless 316ti 316 Stainless Steel Rectangular Tube DIN17459 75 X 50 Hollow Section

Cold Drawn 201 304 304L 316 316L 316ti 310S 904L 410 430 Seamless Welded Round/ Square/ Rectangular Tube

Hot rolled

advantages

It can destroy the casting structure of steel ingot, refine the grain size of steel, and eliminate the defects of microstructure, so that the steel structure is compacted and the mechanical properties are improved. The improvement is mainly reflected in the direction of impurity rolling, which makes the steel no longer isotropic to a certain extent. Bubbles, cracks and looseness formed during casting can also be welded under high temperature and pressure.

disadvantages

After hot rolling, the non-metallic inclusions (mainly sulfides and oxides, as well as silicates) in the steel are compressed into thin sheets, resulting in fragmentation. Delamination greatly deteriorates the tensile properties of steel along the thickness direction and may cause interlaminar tearing during weld shrinkage. The local strain induced by weld shrinkage is often several times the yield point strain, which is much larger than the strain induced by load.

Uneven cooling causes residual stress. The residual stress is the internal self-phase equilibrium stress without external force. All kinds of hot rolled section steel have this kind of residual stress. The larger the section size of general section steel is, the greater the residual stress is. Although the residual stress is self-phase equilibrium, it has a certain effect on the performance of steel member under external force. Such as deformation, stability, fatigue resistance and other aspects may have adverse effects.

Cold rolled

Cold rolling refers to the processing of steel plate or strip into various forms of steel under normal temperature after cold drawing, cold bending, cold drawing and other cold processing.

advantages

Forming speed, high yield, and do not damage the coating, can be made into a variety of cross section forms, to meet the needs of the use conditions.

Cold rolling can produce large plastic deformation of steel, thus raising the yield point of steel.

disadvantages

Although there is no hot plastic compression in the forming process, there is still residual stress in the section, which will inevitably affect the overall and local buckling characteristics of steel.

Cold rolled sections are generally open section, which results in lower free torsion stiffness of section. When it is bent, it is easy to twist, and when it is pressed, it is easy to bend and twist, and the torsion resistance is poor.

The wall thickness of cold-rolled shaped steel is small, there is no thickening at the corner where the plate connects, and the ability to bear the local concentrated load is weak.

The main difference between hot rolling and cold rolling

The section of cold rolled steel is allowed to be partially buckled so that the bearing capacity of the bar after buckling can be fully utilized. Local buckling of hot rolled section is not allowed.

The causes of residual stress are different between hot - rolled and cold - rolled sections, so the distribution of residual stress on section should be very different. The residual stress distribution on cold-formed thin-wall section is flexural, while that on hot-rolled or welded section is thin film.

The free torsion stiffness of hot rolled section is higher than that of cold rolled section, so the torsion resistance of hot rolled section is better than that of cold rolled section.