Welded steel pipe according to the welding process is divided into furnace welded pipe, electric welding (resistance welding) pipe and automatic arc welding pipe, according to the welding form is divided into straight seam welded pipe and spiral welded pipe, according to the end shape is divided into round welded pipe and special-shaped (square, flat, etc.) welded pipe. According to usage, it is divided into general welded pipe, galvanized welded pipe, oxygen blown welded pipe, wire bushings, metric welded pipe, roller pipe, deep well pump pipe, automobile pipe, transformer pipe, thin-wall welded pipe, special-shaped welded pipe and spiral welded pipe. Because of the different welding methods, there are different methods of producing welded steel tubes. The application of welded pipe is mainly used in boilers, automobiles, ships, light construction structure of doors and Windows steel, furniture, various agricultural machinery, scaffolding, wire pipe, high-rise shelves, containers and so on.