Advantages and disadvantages of large diameter hot-rolled seamless steel pipe

Large-diameter rolled seamless steel tube in terms relative to the cold, cold rolling is carried out at a temperature below the recrystallization rolling, the hot rolling is carried out at a temperature above the recrystallization rolling.

Benefits:
Large-diameter hot-rolled seamless steel pipe can damage the ingot casting organizations, grain refinement of steel and eliminate defects in the microstructure, so that the dense tissue steel, mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that the steel is no longer certain extent isotropic; pouring bubbles formed cracks and porosity, but also in under the action of high temperature and pressure welding.

Disadvantages:
1 After hot rolling, the steel inside the non-metallic inclusions (mainly sulfides and oxides, and silicates) is pressed into the sheet, delamination (interlayer) phenomenon. Layered in the thickness direction of the steel in tension performance deteriorated significantly, and may occur in the weld shrinkage interlayer tear. Weld shrinkage-induced local strain reaches the yield point strain often several times larger than the strain caused by the load;
2 the residual stress caused by uneven cooling. Residual stresses in the absence of external force equilibrium of internal stress from a variety of hot-rolled steel has a cross-section of such residual stress, generally the larger beam cross-sectional size, the greater the residual stresses. Although the residual stress is self-equilibrium, but the steel members under loads or have a certain impact on the performance. Such as deformation, stability, fatigue, etc. are likely to produce adverse effects.
3 hot-rolled steel products, thickness and edge width for poor control in this regard. We are familiar with thermal expansion and contraction, since the beginning of the hot rolled out even the length, thickness are achieved and finally cooled or there will be some negative difference, this negative difference edge width is wider, thicker the performance of the more obvious. So for large steel, for steel edge width, thickness, length, angle, and no law requires very precise edges.