The main production processes of large-diameter seamless steel pipes in China are hot-rolled large-diameter seamless steel pipes and heat-expanded-diameter seamless steel pipes. The maximum specifications of heat-expanded seamless steel pipes are 325mm-1220mm and the thickest is 200mm. The size of the national standard, thermally expanded seamless steel pipe is what we often call thermally expanded, relatively low-density but strong shrinkage steel pipes are used to expand the diameter of the pipe by the oblique rolling method or drawing method. In a relatively short period of time, thickening steel pipes can produce non-standard and special types of seamless pipes, with low cost and high production efficiency, which is the development trend of the international pipe rolling field.