Seamless steel pipe with hollow cross-section, a large number of fluid transport pipelines, such as the transport of oil, natural gas, gas, water and some solid materials pipelines. Compared with solid steel such as round steel, steel tube has the same bending and torsional strength and is lighter in weight, such as oil drill pipe, automobile transmission shaft, bicycle frame and steel scaffolding used in construction and other steel pipe manufacturing ring-shaped parts, can improve the utilization of materials, simplify the manufacturing process, save materials and processing time, steel pipes have been made widely.