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1: Generally, the delivery status of hot rolled seamless steel pipes is hot rolling and delivery after heat treatment. For pipes with small diameter, large size, high precision and large wall thickness change, hot extrusion technology is generally used.
2; The technological process of precision seamless steel pipe includes blank making, blank heating, piercing, pipe rolling, reheating waste pipe, reducing diameter, straightening, pipe cutting and finishing.
3; The dimensional accuracy and outer diameter deviation of precision seamless steel pipe mainly depend on the temperature before secondary heating, piercing speed and secondary heating temperature before reducing diameter.
4; The uneven wall thickness of steel pipe is mainly caused by the uneven reheating temperature and reducing temperature before reducing, and the movement of steel pipe in the pass during reducing.
5; The production process of cold-drawn precision seamless steel pipe is generally as follows: heat treatment normalizing, pickling, internal grinding, cold drawing, straightening, internal and external diameter and wall thickness inspection.
6; The dimensional accuracy and surface roughness of cold-drawn precision seamless steel pipe depend on the temperature and time of heat treatment, the quality of pickling, the roughness of cold-drawn die hole and the effect of mechanical straightening in the whole process.
7; The mechanical properties of carbon structural steel pipes generally meet the requirements of GB3087-87 Seamless Steel Pipe for Medium and Low Pressure Boilers and GB53 10-95 Seamless Steel Pipe for High Pressure Boilers. Alloy structural steel pipe conforms to GB8 162-87 Seamless Steel Pipe for Structure, and high-pressure steel pipe for high-pressure fertilizer equipment conforms to GB6479-2000 Seamless Steel Pipe for High-pressure Fertilizer Equipment.
8; The dimensional accuracy, wall thickness deviation range and allowable deviation of outer diameter of hot-rolled precision seamless steel pipe shall comply with the provisions in Table 1. The dimension accuracy, wall thickness deviation range and allowable deviation of outer diameter of cold-drawn precision seamless steel pipe shall comply with the provisions in Table 2.