Advantages and disadvantages of hot rolled seamless steel pipe

The production process of general seamless steel pipes can be divided into two types: cold drawing and hot rolling. Hot rolling, as the name suggests, has high temperature, so the deformation resistance is small, and large deformation can be achieved. Take the rolling of steel plates as an example. Generally, the thickness of continuous casting billet is about 230mm, and after rough rolling and finish rolling, the final thickness is 1~20mm. At the same time, due to the small width-to-thickness ratio of the steel plate, the dimensional accuracy requirements are relatively low, and plate shape problems are not prone to occur. The main focus is to control the crown.

Hot-rolled Seamless steel pipe: Hot rolling is relative to cold rolling. Cold rolling is rolling below the recrystallization temperature, while hot rolling is rolling above the recrystallization temperature.

• Advantage of Hot Rolled Carbon Steel Pipe:

Hot-rolled carbon steel pipes can destroy the casting structure of the steel ingot, refine the grains of the steel, and eliminate defects in the microstructure, thereby making the steel structure dense and improving the mechanical properties. This improvement is mainly reflected along the rolling direction. As a result, the steel is no longer isotropic to a certain extent; bubbles, cracks and looseness are formed during pouring. It can also be welded under high temperature and pressure.

• Disadvantages of Hot Rolled Alloy Steel Pipe:

After hot rolling, the non-metallic inclusions (mainly sulfides, oxides, and silicates) inside the steel are pressed into thin sheets, resulting in delamination (sandwiching). Delamination greatly deteriorates the tensile properties of the steel along the thickness direction and may cause interlaminar tearing as the weld shrinks. The local strain induced by weld shrinkage often reaches several times the yield point strain, which is much larger than the strain caused by load;
Residual stresses caused by uneven cooling. Residual stress is the internal self-balanced stress in the absence of external force. Hot-rolled steel sections of various sections have such residual stress. Generally, the larger the cross-section size of the section steel, the greater the residual stress. Although residual stress is self-balanced, it still has a certain impact on the performance of steel components under the action of external forces. For example, it may have adverse effects on deformation, stability, fatigue resistance, etc.
Hot-rolled steel products are difficult to control in terms of thickness and edge width. We are familiar with thermal expansion and contraction. Even if the length and thickness are up to standard after hot rolling at the beginning, there will still be a certain negative difference after cooling. The wider the side width and the thicker the thickness, the more obvious this negative difference will be. . Therefore, for large-sized steel, the side width, thickness, length, angle, and edge lines of the steel cannot be too precise.