Features of Hot-rolled Seamless Steel Pipe

With respect to hot-rolled seamless rolled seamless steel pipe is concerned, the cold-rolled seamless steel pipe is carried out at a temperature below the recrystallization rolling, but the hot-rolled seamless pipe is rolled in the recrystallization temperature or more carried out.

Advantages: ingot casting can destroy tissue, 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. The hot-rolled steel pipe manufacturers after hot-rolled seamless steel inside the 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.

3. Hot-rolled steel products, poor control of the thickness and width edge in this regard. We are familiar with thermal expansion and contraction, since the beginning of the hot rolling out even the length, thickness are standard, and finally cooled or there will be some negative difference, this negative differential edge width wider, more obvious as the thickness performance. So for large steel, steel edge for width, thickness, length, angle, and no law requires too precise edges.