Welded steel pipe, plates or strips for is after curly made of welded steel pipe after molding. Welded steel pipe production process is simple, high production efficiency, different specifications, equipment financing small, but the General strength of less than seamless steel tubes. Since in the 1930 of the 20th century, with high quality steel rolling production in rapid development and progress of welding and inspection technology, continuously improve weld quality, welded steel pipe specifications growing varieties, and in a growing number of areas instead of seamless steel tubes. Weld seam of welded steel pipe in the form of longitudinal welded pipe and spiral welded pipe.

Longitudinal welded pipe production process is simple, high efficiency, low cost, rapid development. High strength of spiral welded pipe than longitudinal welded pipe, can narrow the billet production of large diameter welded pipes, you can use the same width of the billet production of different diameter of the pipe. But compared with the straight seam pipe of the same length, weld length 30~100%, and lower production rate.

Therefore, most small-diameter pipe used straight seam welding, large-diameter pipe is mostly used spiral welding.