Seamless steel tube with a hollow cross-section, for a large number of pipes conveying fluid, such as the transportation of oil, natural gas, coal gas, water and some solid materials pipeline. Compared to solid steel such as steel pipes and round steel in flexural torsional strength the same, lighter, is an economic section steel, widely used in the manufacture of structural parts and mechanical parts, such as drill pipe, automotive transmission, bike steel frame construction with scaffolding ring with a steel pipe manufacturing parts, improve material utilization, simplify the manufacturing process, saving material and processing time, such as rolling bearing rings, jack sets, has been widely used to make steel manufacturing. Steel pipe or a variety of conventional weapons is an indispensable material barrel, barrel must steel pipe manufacturing. The steel pipe different shape of the cross-sectional area can be divided into the tube and Yixingguan. Since the equal conditions in the perimeter area of ??a circle with a round pipe can deliver more fluid. Addition, when subjected to internal or external radial pressure, the annular cross-sectional force more uniform, therefore, most of the pipe is circular tube. http://tjdsgg.cn