Small-caliber seamless steel pipe is a round, square and rectangular steel with a hollow section and no joints on the periphery. Seamless steel pipes are made of steel ingots or solid pipes that are perforated into capillary tubes, and then made by hot rolling, cold rolling or cold drawing. Seamless steel pipes have a hollow section and are mostly used as pipelines for conveying fluids. Compared with solid steel such as round steel, steel pipes have the same bending and torsion strength and lighter weight. They are economical cross-section steels and are widely used in manufacturing structures. Parts and mechanical parts, such as oil drill pipes, automobile rotating shafts, bicycle frames, and steel scaffolding used in construction.