There are seamless steel pipes along the perimeter of its cross section. According to different production methods, it can be divided into hot-rolled pipe, cold-rolled pipe, cold-drawn pipe, extruded pipe, jacking pipe, and so on. Materials are ordinary and high-quality carbon structural steel (Q215-A ~ Q275-A and 10 ~ 50 steel), low alloy steel (09MnV, 16Mn, etc.), alloy steel, stainless steel and other acid. Divided into general purpose (for water, gas pipeline and structural parts, mechanical parts) and special (for boilers, geological exploration, bearings, acid resistance, etc.)