Hot rolled strip steel of SSAW (Spiral seam submerged arc welding steel pipe) is bent according to the spiral shape. Then, spiral seam welded steel pipe which is also called spiral welded pipe, spiral pipe, spiral steel tube is made by the inseam and outer seam of automatic submerged arc welding. For the following reason, it can be widely used in the production of large diameter steel pipe:

 

1) As long as changing the forming angle, various diameter of steel pipe can be produced by using the same width of steel strip.

2) Because it is bent to from into shapes continuously, the length of steel tubes is not restricted;

3) Weld spiral shape is evenly distributed on the circumference of the whole steel tube, so the steel tube has high precise size and high intensity.

4) It is easy to change size, which is suitable for steel tube production with small batch and many varieties.

For the spiral welded steel pipe, its defect is inclined defects. In the operation process, the equivalent defect length of the principal stress direction of steel tube, namely the direction of steel tube axis is smaller than that of seam steel pipe. Second, the pipeline steel all belongs to rolling steel plate. So, the impact toughness has larger anisotropy. The CVN value along the rolling direction is perpendicular to the CVN value of the rolling direction. Moreover, the CVN value along the rolling direction is three times higher than that of the rolling direction. Principal stress seam steel pipe suffers is just perpendicular to the lowest direction of pipe impact resistant ability. While, the spiral tube staggers the lowest direction of the pipe impact resistant ability, which turns the disadvantage of the length of spiral pipe welding line into its advantage.