Advantages and disadvantages of hot rolled seamless steel pipe

Advantages and disadvantages of hot rolled seamless steel pipe

Hot-rolled seamless steel pipe: Hot-rolling is related to cold-drawing, and hot-rolling is performed above the recrystallization temperature of rolling.

Advantages of hot rolled seamless steel pipe:
The ingot can destroy the structure, refine the grains of the steel, and eliminate the defects in the structure, thereby improving the mechanical properties of the dense structure of the steel. This improvement is mainly reflected to a certain extent along the rolling direction, the steel is no longer isotropic; bubbles, cracks and porosity are formed during pouring, which can be welded at high temperature and pressure.

Disadvantages of hot rolled seamless steel pipe:
1. After hot rolling, the non-metallic inclusions (mainly sulfides and oxides, and silicates) inside the steel are pressed into the sheet, resulting in a delamination (interlayer) phenomenon. The tensile properties of the layered steel in the through-thickness direction deteriorate significantly, and interlaminar tear weld shrinkage may occur. The shrinkage yield point strain caused by the local strain of the weld often reaches several times the strain caused by the load;

2. Residual stress caused by uneven cooling. Residual stress is balanced by internal stress in the absence of external force. Regardless of various residual stresses such as hot-rolled steel sections, generally the larger the section size of the steel, the greater the residual stress. Although the residual stress is out of balance, it still has a certain influence on the performance of the steel member under load. Terms such as deformation, stability, fatigue resistance, etc. may have adverse effects.

3. Hot-rolled steel, in this aspect, the thickness and width of the edge are not well controlled. We are familiar with thermal expansion and cold contraction. Since the beginning of hot rolling, even the length and thickness are standard, and there will still be some negative differences in the final cooling. The wider and thicker the negative difference, the more obvious the performance. Therefore, for large steel, there is no rule that requires a very precise edge for the width, thickness, length, and angle of the steel edge.

Hot-rolled seamless steel pipe process:
Round tube piercing → heating → three-roll rolling, rolling or extrusion → separation → sizing (or diameter reduction) → cooling → straightening → hydraulic test (or inspection) → marking → storage

Note: Cold-Drawn Seamless (CDS) is a cold-drawn 1018/1026 steel pipe that offers uniform tolerances, enhanced machinability, and higher strength and tolerances compared to hot-rolled products.

Read more ：seamless carbon steel pipe 

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