The straight sewing steel pipe is an important process in the production of straight steel pipes. Especially for API standards with high quality requirements and oil pipes, special pipes for machinery and equipment. These steel pipes not only have strict requirements in the quality of steel and welds, but also have high straight lines of steel pipes. It is required that because the deviation of linearity is directly related to the processing, connection, and twisting of the tube and the pipe holes of the tube and the conveyor tube. There are two types of processing of the existing tube -ending car -rotation and tool rotation. Most car silk processing uses a tube rotation, which requires higher linearity of the steel pipe.

What is the internal stress? Temperature and external forces affect the interaction between a molecule when deformation. When the steel pipe is formed and welded, the welding temperature is also affected by the influence of these external formed bending. The cross section of the steel pipe is a ring -shaped, which will generate two basic stress on this ring area: parallel to the ring -shaped force and perpendicularity of the ring -shaped shape. The parallel stress will make the tube not round; the vertical stress will make the tube bent. Therefore, there is a cold diameter process during the production process of straight steel pipes, the purpose is to eliminate the internal stress of the steel pipe and increase the intensity of the use of straight steel pipes.