difference of hot rolled steel and cold drawn steel pipe

Hot-rolled and cold rolled steel or steel plate is a step, they have for the organization and performance of steel of great influence, rolled steel, hot-rolled mainly based, only for the production of cold rolled steel and plate trumpet. First, the hot-rolled advantages: You can destroy ingot casting organizations, grain refinement of steel, and eliminate defects microstructure, so that the steel dense tissue, the mechanical properties are improved. This improvement mainly reflected in the rolling direction, so that the steel is no longer certain extent isotropic body; forming bubbles when pouring, cracks and loose, can also be welded together under high temperature and pressure. Disadvantages: 1. After the hot-rolled steel inside non-metallic inclusions (mainly sulphide and oxide, as well as silicate) is pressed into the sheet, stratification (mezzanine) phenomenon. Layered in the thickness direction so that the steel tension performance deteriorated significantly, and there may be an interlayer tear weld shrinkage. Weld shrinkage induced local strain reaches the yield point strain often several times larger than the load caused by the strain. 2. residual stresses caused by uneven cooling. The residual stress in the absence of external force internal self-equilibrium stress, hot-rolled steel has a variety of sections such residual stress, the greater the general steel cross-sectional dimension, the greater the residual stress. Although the residual stress is self-balanced, but still has some influence on the performance of the steel members under loads. Aspects such as deformation, stability, fatigue, etc. are likely to have an adverse effect. Second, cold rolling means at room temperature, after cold drawing, cold, cold drawing and other cold plate or strip into the processing of various types of steel. Advantages: forming speed, high output, and does not damage the coating, can be made into a variety of cross-sectional form, it needs to adapt to the conditions of use; cold-rolled steel to produce a lot of plastic deformation, thereby increasing the yield of steel point. Disadvantages: 1. Although the molding process has not been hot plastic compression, but there are still residual stress within the cross-section of the overall and local buckling characteristics will inevitably have an impact steel; 2. cold-rolled Seamless pipe style is generally open section, allowing free cross-section low torsional stiffness. When flexural prone to twisting during compression prone to bending-torsional buckling, torsional performance is poor; 3. cold-formed steel wall thickness smaller, in the corner of the plate convergence and no thicker, to withstand localized concentrated load capacity is weak. Third, the main difference between a hot and cold, cold rolled steel to allow a cross-sectional partial flexion, which can make full use of the bearing capacity after buckling rods; and hot-rolled steel sectional allowed local buckling occurs. 2, for different reasons hot-rolled steel and cold-rolled steel residual stress, so the distribution of the cross section is also a great difference. Cold-formed steel residual stress distribution on the cross section is curved, and hot rolled steel or steel welding residual stress distribution on the cross section of a thin film type. 3, hot-rolled steel of freedom torsional stiffness than cold-rolled steel is high, so torsional performance is better than hot-rolled steel cold drawn.