Large-diameter seamless steel pipe: The main production process is hot-rolled large-diameter seamless steel pipe and heat-expanded seamless steel pipe. The maximum specification of heat-expanded seamless steel pipe is 325mm-1220mm and the maximum thickness is 120mm. Heat-expanded seamless steel pipe can be produced in non-national standard. The heat-expanded seamless pipe is what we often call the heat-expanded pipe. The steel pipe with relatively low density but strong shrinkage is a kind of waste pipe finishing rolling process in which the diameter of the pipe is enlarged by the cross-rolling method or the 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. This is the current development trend in the field of international pipe rolling.

 

GB5310 (Seamless steel pipe for high-pressure boiler) stipulates that steel pipes with outer diameter greater than or equal to 76mm and wall thickness ≥14mm should be subjected to Charpy V longitudinal impact test at 20℃; the average value of the impact energy of the three samples should not be low At 40J, the impact energy of a sample is allowed to be lower than the average value, but not less than 70% of the average value. For steel pipes with outer diameter> 219.1mm and wall thickness ≥ 25mm, transverse mechanical performance test can be used instead of longitudinal mechanical performance test. For Charpy V-shaped transverse impact test at 20℃, it is more convenient to do transverse mechanical performance test for large-diameter pipes.