A steel production process - hot rolling, as the name suggests, hot rolling is relative to cold rolling, cold rolling is rolling below the recrystallization temperature, and hot rolling is above the recrystallization temperature. rolling. To put it simply, a billet is heated and rolled several times, then trimmed and straightened into a steel plate, which is called hot rolling. Can significantly reduce energy consumption and reduce costs. During hot rolling, the metal has high plasticity and low deformation resistance, which greatly reduces the energy consumption of metal deformation. Hot rolling can improve the processing performance of metals and alloys, that is, the coarse grains in the casting state are broken, the cracks are healed significantly, the casting defects are reduced or eliminated, the as-cast structure is transformed into a deformed structure, and the processing performance of the alloy is improved.

The hot-rolled steel products of the seamless steel pipe production process are not well controlled in terms of thickness and side width. We are familiar with thermal expansion and cold contraction, because even if the length and thickness are qualified when hot rolled at the beginning, there will still be a certain negative difference after cooling. The wider the side width of this negative difference, the thicker the thickness, the more obvious on. Therefore, regarding the hot-rolled steel in the manufacturing process of seamless steel pipes, the edge width, thickness, length, viewpoint, and edge of the steel cannot be required to be too accurate.

After the defect is hot rolled through the seamless steel pipe production process, the non-metallic inclusions (mainly sulfides and oxides, and silicates) inside the steel are pressed into thin sheets, showing a delamination (interlayer) phenomenon. Delamination greatly deteriorates the ability of the steel to be pulled through the thickness, and there is a possibility of interlaminar tearing as the weld shortens. Partial strain induced by weld shortening often reaches several times the yield point strain.

Residual stress due to uneven cooling is much larger than the strain induced by the load. Residual stress is the stress of internal self-phase equilibrium without the effect of external force. Hot-rolled steel in the production process of seamless steel pipes of various sections has such residual stress. Generally, the larger the section size of the section steel, the greater the residual stress. Although the residual stress is self-balanced, it still has a certain influence on the function of the steel member under the effect of external force. Such as deformation, stability, anti-fatigue and other aspects may have unfavorable effects. The advantages can damage the casting structure of the ingot, refine the grains of the steel, and eliminate the defects of the microstructure, so that the steel structure is dense and the mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that the steel is no longer an isotropic body to a certain extent; the bubbles, cracks and porosity formed during casting can also be welded under the effect of high temperature and pressure.