are for hot-rolled and cold rolled steel or steel plate, they have a great impact on the microstructure and properties of the steel, steel rolling to hot-rolled, cold rolled only for the production of the trumpet section steel and sheet metal.
, hot
Advantages: You can destroy the ingot casting organizations, refine the grain of the steel, and eliminate the defects of the microstructure, so that the steel organization dense, mechanical properties improved. This improvement mainly reflected in the rolling direction, so that the steel to a certain extent, is no longer isotropic; pouring the formation of bubbles, cracks and loose, but also in the high temperature and pressure welding.
Disadvantages: after after hot rolling, steel inside non-metallic inclusions (mainly sulfides and oxides, silicates) were pressed into thin slices, a layered (laminated) phenomenon. Layered steel thickness direction by the pull of the performance deteriorated significantly, and may weld contraction between layers tear. Weld contraction-induced local strain often reach several times the yield point strain, much larger than the load caused by the strain.
(2) uneven cooling caused by the residual stress. The residual stress is self-phase equilibrium stress, a variety of cross-section of hot-rolled steel has such there is no external force, internal residual stress, the greater the general steel section size, residual stress. Although the residual stress is self-phase equilibrium, but still has some influence on the performance of steel members under loads. Such as deformation, stability, anti-fatigue may adversely.
, cold
Means at room temperature, after cold drawing, cold-formed, cold drawn, cold plate or strip processed into various types of steel.
Advantages: fast forming speed, high output, and does not damage the coating, can be made into a variety of forms of cross-section to accommodate the needs of the conditions of use; cold-rolled steel to produce a lot of plastic deformation. thereby increasing the yield point of steel.
Disadvantages: Although the molding process without thermal state plastic compression, but there are still residual stress in the cross-section, characteristics will inevitably have an impact on steel as a whole and the local buckling;
(2) cold-rolled steel style with open sections, low torsional stiffness of the freedom of cross-section. Prone to torsion, flexural and compression prone to bending and torsional buckling, torsional performance is poor;
Cold-rolled steel wall thickness smaller, and no thickening in the corner of plate convergence, weak to withstand the localized concentrated load capacity.
The main difference , hot-rolled and cold-rolled
, Cold formed steel to allow cross-section local buckling, which can make full use of the rod after buckling bearing capacity; does not allow cross-section of hot-rolled steel local buckling occurs.
2, the residual stress in hot rolled and cold-rolled steel produced by different reasons, the distribution of the cross sections are quite different. The residual stress distribution in cold-formed steel section bending type and hot rolling steel or welding residual stress on the steel cross-section distribution of the film type.
Hot-rolled steel free torsional rigidity than cold-rolled steel, the torsional properties of hot-rolled steel is better than cold-rolled steel.
molding process