Alloy pipes have hollow sections and are widely used as pipelines for transporting fluids, such as pipelines for transporting oil, natural gas, gas, water and some solid materials. Compared with solid steel such as round steel, alloy steel pipe has lighter weight when its bending and torsional strength is the same. Alloy steel pipe is an economic section steel, which is widely used to manufacture structural parts and mechanical parts, such as oil drill pipe, automobile transmission shaft, bicycle frame and steel scaffold used in construction. Making ring parts with alloy steel pipe can improve the material utilization rate, simplify the manufacturing process, save materials and processing hours, such as rolling bearing ring, jack sleeve, etc. at present, steel pipe has been widely used for manufacturing. Alloy steel pipe is also an indispensable material for all kinds of conventional weapons. Gun barrel and barrel should be made of steel pipe. Alloy steel pipe can be divided into round pipe and special-shaped pipe according to different cross-sectional area and shape. Because the circular area is the largest under the condition of equal circumference, more fluid can be transported by circular pipe. In addition, when the ring section is subjected to internal or external radial pressure, the force is more uniform. Therefore, most steel pipes are round pipes.