Advantages And Disadvantages Of Hot-Rolled Steel Beams And Cold-Rolled Steel Beams

In general, the mechanical properties of hot-rolled than cold-rolled better, after heat treatment of steel, its tensile strength, plasticity, toughness will be improved, in addition, the important point, heat treatment to eliminate residual stress, and Cold rolling may produce residual stresses due to uneven deformation of the steel yield during processing, and this residual stress has a great influence on the stability. 

Hot-rolled and cold-rolled steel or steel forming process, they have a great impact on the organization and performance of steel. 

Steel rolling mainly is hot-rolled, cold rolled only for the production of small steel and sheet. 

The advantages of hot rolling

Can damage the ingot casting organization, refine the grain of steel, and eliminate the defects of microstructure, so that the steel structure compact, mechanical properties are improved. This improvement is mainly reflected in the direction along the rolling, So that the steel to some extent is no longer isotropic body; pouring the formation of bubbles, cracks and loose, but also in high temperature and pressure welding. 

Hot rolling shortcomings: 

First, after hot rolling, the steel within the non-metallic inclusions (mainly sulfide and oxide, as well as silicate) is pressed into thin slices, layered (sandwich) phenomenon. Delamination deteriorates the tensile properties of the steel material in the thickness direction, and there is a possibility that interlaminar tearing occurs when the weld is contracted. Weld shrinkage-induced local strain often reaches several times the yield point strain, much larger than the load-induced strain. 

Second, the residual stress caused by uneven cooling. Residual stress is no external stress in the internal self-phase equilibrium stress, a variety of cross-section of the hot-rolled steel have such residual stress, the general section size of the larger steel, the greater the residual stress. Although the residual stress is self-phase equilibrium, but under the external force of steel components in the performance or have some impact. Such as deformation, stability, anti-fatigue and other aspects may have a negative effect. Cold rolling 

Cold-rolled refers to at room temperature, after cold drawing, cold bending, cold drawing and other cold processing of steel or strip processed into various types of steel. 

The advantages of cold rolling are high forming speed, high output, and no damage to the coating, and can be made into various cross-sectional forms so as to meet the requirement of using conditions. Cold-rolled steel can produce a lot of plastic deformation, thereby improving the yield point of steel. 

Cold rolling shortcomings: 

First, although the process of forming has not been hot plastic compression, but there are still residual stress within the cross-section, the whole steel and local buckling characteristics must have an impact.

Second, cold-rolled steel section is generally open cross-section, making the free section of the lower torsional stiffness. In the bend prone to twist, compression prone to bending torsional buckling, torsional performance is poor. 

Third, cold-formed steel wall thickness is smaller, in the corner of the convergence of the board and there is no thickening, to bear the local concentration of the weak capacity. 

The main differences between hot and cold rolling are: 

1, cold-formed steel to allow cross-section of local buckling, which can take full advantage of the buckling after the bearing capacity; and hot-rolled steel section does not allow local buckling. 

2, hot-rolled section steel and cold-rolled steel residual stress caused by different reasons, so the distribution of the cross-section is also very different. The distribution of residual stresses on the cold-formed thin-walled sections is curved, while the residual stress distribution on the cross-sections of the hot-rolled sections or welded sections is a thin film type.