There are many reasons for the bending of the steel pipe, such as the heat effects of welding seams during welding, the eccentricity of the formation, as well as compression, the imbalance of the bending power, and so on. But fundamentally, bending is the role of stress in the steel pipe. Simply put, bending is the uneven stress. So, is there no internal stress on straight steel pipes? no. The straight steel pipe also has internal stress, but the internal stress of the direct tube is less.
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.
