Both hot-rolling and cold-rolling of spiral pipes are processes for shaping steel sections or plates, which have a significant impact on the microstructure and properties of the steel. In steel rolling, mostly hot-rolling is used, while cold-rolling is mainly utilized for manufacturing small-sized sections and sheets.

First, hot-rolling can disrupt the casting structure of ingots, refine the grain size, and eliminate defects in the microstructure, thereby making the steel texture denser and enhancing mechanical properties. This improvement mainly manifests in the rolling direction, making the steel to a certain extent no longer isotropic; bubbles, cracks, and porosities formed during pouring can also be welded under the action of high temperature and pressure.

Second, cold-rolling refers to processing plates or strips into various forms of steel through cold-working methods such as cold-drawing, cold-bending, and cold-extrusion at room temperature. It features rapid forming speed, high output, no damage to the coating, and can be made into various sections to meet the requirements of use; cold-rolling can also cause large plastic deformation of the steel, thereby increasing the yield point of the steel.

Third, the main differences between hot-rolling and cold-rolling are:

Cold-formed steel allows local buckling of the section, thereby being able to fully utilize the bearing capacity after the member buckles; while hot-rolled sections do not allow local buckling of the section.

The causes of residual stress in hot-rolled sections and cold-rolled sections are different, so the distribution on the section also varies greatly. The residual stress distribution on the section of cold-formed thin-walled sections is in a curved shape, while that on the section of hot-rolled or welded sections is in a thin-film shape.

The torsional stiffness of hot-rolled sections is higher than that of cold-rolled sections, so the torsional performance of hot-rolled sections is better than that of cold-rolled sections of spiral pipes.

Hot-rolling and cold-rolling of spiral pipes are both forming processes for sections or plates, which have a considerable impact on the structure and properties of the steel. The rolling of steel mainly relies on hot-rolling, and cold-rolling is only used for manufacturing small-sized sections and thin plates.