Hot rolled seamless steel tube: hot rolling is related to the cold drawn, hot rolling is performed above the recrystallization temperature of the rolling.
Hot-rolled seamless steel tube advantages:
Ingot casting can destroy tissue, grain refinement of steel and eliminate defects microstructure, so that the steel dense tissue mechanical properties are improved. This improvement is mainly reflected in the direction along the rolling direction to a certain extent, the steel is no longer isotropic; pouring formed bubbles, cracks and loose, can be welded at a high temperature and pressure.
Hot-rolled seamless stee tube disadvantages:
1. After hot rolling, the steel inside the non-metallic inclusions (mainly sulphide and oxide, and silicates) is pressed into the sheet, delamination (interlayer) phenomenon. Layered in the thickness direction of the steel tension performance deteriorated significantly, and there may be an interlayer tear weld shrinkage. Weld local strain-induced contraction of the yield point strain often reach several times larger than the load caused by the strain;
2. Residual stresses caused by uneven cooling. Residual stresses in the absence of external force from the internal equilibrium of stress, both hot-rolled steel section such various residual stress, the greater the cross-sectional size generally of steel, the residual stress is larger. Although the residual stress from equilibrium, but still has some influence on the performance of the steel members under loads. Terms such as deformation, stability, anti-fatigue effects may adversely.
3. Hot-rolled steel products, poor control of the thickness and width of the edge in this respect. 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 difference edge width wider, thicker the more obvious manifestations. So for large steel for steel edge width, thickness, length, angle, and no law requires very precise edges.
Hot-rolled seamless steel tube process:
Round tube perforation → heating → three-roll rolling, rolling or extrusion → detached → sizing (or reducing) → cooling → straightening → hydrostatic test (or testing) → mark → storage