Classified by Production Methods 1. Seamless Steel Pipe - hot rolled seamless steel pipe, cold rolled seamless steel pipe, cold drawn seamless steel pipe 2. Welded Steel Pipe - longitudinal welded pipe, spiral welded pipe, electric resistance welded pipe Classified by Cross-sectional Shape 1. Simple section steel pipe - round carbon steel pipe, square carbon steel pipe, rectangular carbon steel pipe, oval carbon steel pipe ect. 2. Complex section steel pipe - hexagonal carbon steel pipe with unequal edge, five plum shaped carbon steel pipe, double convex carbon stee pipe, double concave carbon steel pipe ect. Classified by Wall Thickness 1. Thin walled carbon steel pipe 2. Thick walled carbon steel pipe Classified by the Application Carbon steel pipe can be used for thermal equipment, machinery industrial pipe, oil line pipe, geological drilling steel pipe, container steel pipe, chemical industry steel pipe, and other special purpose steel pipe.