Fluid pipe is a hollow cross section, from start to finish without welds. Steel hollow cross section, petroleum, natural gas, coal gas, water pipes and other large pipe for transporting fluids transportation and some solid materials. Compared to other steel and solid steel bar in bending torsional strength, lighter weight, is an economic cross-section steel, widely used in the manufacture of structural parts and mechanical parts, such as drill pipe, automotive drive shafts, bicycle rack and construction using steel scaffolding. Ring with a steel pipe manufacturing parts, can improve material utilization, simplify the manufacturing process, saving materials and processing time, such as bearing rings, jack sets, has been widely used to manufacture steel pipe. Steel or a variety of conventional weapons indispensable material, barrel, barrel, etc. to make steel. Steel shapes of different cross-sectional area can be divided into tube and shaped tubes. Because in the perimeter of equal conditions, the largest area of ??a circle with a circular tube can carry more fluid. In addition, the circular cross section to withstand internal or external radial pressure, the force is uniform, so the vast majority of the pipe is pipe.