Hot-rolled seamless steel pipe: Hot rolling is related to cold drawing. Hot rolling is carried out above the recrystallization temperature of rolling.


Advantages of hot-rolled seamless steel pipe:
The ingot can destroy the structure, refine the grain size of the steel, eliminate the defect microstructure, and improve the mechanical properties of the compact structure of the steel. This improvement is mainly reflected in the direction along the rolling direction to a certain extent, steel is no longer isotropic; casting bubbles, cracks and loose, can be welded under high temperature and pressure.


Defects of hot-rolled seamless steel pipe:
1. After hot rolling, non-metallic inclusions (mainly sulphides and oxides, as well as silicates) in steel are pressed into the plate, resulting in delamination (interlayer). In the direction of steel thickness, the delamination tensile properties deteriorate significantly, and there may be interlaminar tear weld shrinkage. The strain shrinkage at yield point caused by local strain of weld is often several times larger than that caused by strain.
2. Residual stress caused by uneven cooling. Residual stress in the absence of external forces from the internal equilibrium stress, hot-rolled steel cross-section such as various residual stresses, the larger the size of general steel cross-section, the greater the residual stress. Although the residual stress comes from equilibrium, it still has some influence on the performance of steel members under load. Terms such as deformation, stability and fatigue resistance may have adverse effects.
3. The edge thickness and width of hot rolled steel products are not well controlled in this respect. We are familiar with thermal expansion and shrinkage, because the beginning and even length of hot rolling are standard, and there may be some negative difference in the final cooling. The wider the edge width of the negative difference, the thicker the obvious. Therefore, for large steel with wide, thick, long and angular edges, there is no rule requiring very precise edges.


Hot-rolled seamless steel tube technology:
Tube piercing heating three-roll rolling, rolling or extrusion separation sizing (or reduction) cooling straightening hydraulic test (or test) marking storage