Welded steel pipe and welded pipe, is to use steel plate or steel strip after crimp molding made of welded steel pipe. Welded steel pipe production technology is simple, high production efficiency, varieties, specifications, less equipment investment, but the general strength is lower than the seamless steel tube. Since the 1930 s, with the rapid development of high quality strip steel rolling production and the progress of welding and inspection technology, constantly improve the weld quality, increasing varieties of welded steel pipe specifications, and in the field of more and more instead of seamless steel tube. In the form of welded steel pipe according to the weld seam welded pipe and spiral welded pipe.

Straight seam welded pipe production technology is simple, high production efficiency, low cost, rapid development. The strength of the spiral welded pipe is generally higher than straight seam welded pipe, use a narrow billet production of larger diameter welded pipe, you can also use the same width of billet in the production of different pipe diameter welded pipe. But compared with the same length of straight seam pipe, weld length by 30 ~ 100%, and the production speed is low.

As a result, a small diameter welded pipe are mostly with straight seam welding, large diameter welded pipe for the most part adopts spiral welded.