There should be two kinds of roll welded steel pipes: one is small and medium-sized steel pipes, the wall thickness is not too large, and high-frequency straight welded pipes are usually made by high-frequency continuous welding; The other is the processing method of large diameter or large wall thickness steel pipe, in which the original steel plate is preliminarily formed step by step by hydraulic press, then submerged arc welding is adopted, and then thermal expansion forming is carried out.

Spiral welded pipe is a raw strip steel spirally formed by a forming machine, and spiral welded pipes of different specifications are produced by submerged arc welding inside and outside.

The main differences between the two are:

1, the former is a straight line, and the latter is a helix with different helix angles.

2. Every time the former produces a steel pipe with specifications, it must have a raw material strip steel or steel plate with a specific width; The latter can produce steel pipes with the same width and different diameters.

3. Because of the different weld shapes, the combined stress at the spiral weld is 60-85% of the principal stress of the straight welded pipe under internal pressure. Therefore, under the same working pressure, the wall thickness of spiral welded pipe with the same diameter can be reduced compared with that of straight welded pipe.

4. In the production of small and medium diameter welded pipes, the former has great advantages, while in the production of large diameter welded pipes, the latter has absolute advantages.

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