As is known to all, there are many kinds of different welded pipes in the world. The welded pipe can be divided into many types according to its different material properties, technology of manufacturing and practical uses. In our daily life, the most commonly used welded steel pipes are the ordinary pipes, the ordinary carbon steel wire casing, the ssaw steel pipe, the straight seam welded steel pipes, the helical seam submerged arc welded steel pipes and the high frequency welded steel pipes.