According to the production process, seamless square tube is divided into hot-rolled seamless square tube, cold-drawn seamless square tube, extruded seamless square tube and welded square tube. Among them, the welded square pipe is divided into: (a) according to the process-- arc welded square pipe, resistance welded square pipe (high frequency, low frequency), gas welded square pipe, furnace welded square pipe (b) according to weld-straight welded square pipe, spirally welded square pipe. 

Seamless square tube is a kind of long steel with no joint around the hollow section. Steel pipe has a hollow section and is widely used as a pipeline for conveying fluid, such as oil, natural gas, gas, water and some solid materials. Compared with solid steel such as round steel, steel pipe is lighter in weight when it has the same bending and torsional strength, so it is a kind of steel with economic cross-section, which is widely used in the manufacture of structural components and mechanical parts. such as oil drill pipe, automobile transmission shaft, bicycle frame and steel scaffolding used in construction and so on.Making ring parts with steel pipe can improve the material utilization rate, simplify the manufacturing process, and save materials and processing time, such as rolling bearing ring, Qianjin top sleeve and so on. At present, steel pipe has been widely used to manufacture.Steel pipe is also an indispensable material for all kinds of conventional weapons, such as gun barrel, gun barrel and so on. Steel pipe can be divided into round tube and special-shaped pipe according to the shape of cross-sectional area. Since the area of the circle is the largest under the condition of equal perimeter, more fluid can be transported with a circular tube. In addition, when the ring section is subjected to internal or external radial pressure, the force is more uniform, so the vast majority of steel pipes are circular tubes.However, the circular pipe also has some limitations, such as under the condition of plane bending, the bending strength of the circular tube is not as strong as that of square and rectangular tubes, and square and rectangular tubes are commonly used in some agricultural machinery frames, steel and wood furniture and so on.