The manufacturer of S355J2H pipe tells you that making seamless steel pipes that have been processed into products with less tortuosity has to rely on a mechanical straightening machine to finish. Therefore, in order to eliminate the twists and turns of seamless steel pipes, all seamless steel pipes need to be cold straightened.

The manufacturer of S355J2H pipe tells you that the zigzag of seamless steel pipe is caused by improper adjustment of the rolling mill, residual residual stress during rolling, and unequal cooling along the section and length of the pipe. Therefore, it is impossible to obtain very straight pipes directly from the rolling mill. The manufacturer of S355J2H pipe tells you that only the tortuosity of the cold straightened pipe can be satisfied with the rules of technical conditions.
The manufacturer of S355J2H pipe tells you that the basic principle of straightening is to make seamless steel pipes undergo elasto-plastic twists, from large twists to small twists, so the steel pipe must be repeatedly twisted in the straightening machine. The manufacturer of S355J2H pipe tells you that the degree of repeated twists and turns of the steel pipe is mainly determined by the adjustment of the straightening machine.
The manufacturer of S355J2H pipe tells you that there are many factors that affect the quality of straightening, such as the tortuosity of the original pipe, the size of the steel pipe, the type of material straightening, and the adjustment parameters.