The difference between SSAW steel pipe and LSAW steel pipe

From the point of view of the welding process, whether it is a straight seam steel pipe or a spiral steel pipe, the welding method of the two is the same. However, in the actual welding process, there are often a large number of T-shaped welds in straight seam steel pipes, and there is usually some residual stress on such welds. Although this has little effect on service, it is precisely because these residual stresses increase the likelihood of cracks in the straight seam steel pipe

Compared with SSAW the production process of straight seam steel pipes is much simpler. The production process of straight seam steel pipe is mainly divided into two types, one is high frequency welded straight seam steel pipe, and the other is submerged arc welded straight seam steel pipe. It is because of these characteristics that the production process of straight seam steel pipes is simple, and the production efficiency is very high, the cost is low, and the development speed is very fast.

The production of large-diameter straight-seam steel pipes in industry will adopt T-welding technology, that is, the short sections of the straight-seam steel pipes are spliced into a length that meets the engineering requirements, which greatly increases the possibility of T-welding defects of the straight-seam steel pipes. In addition, the welding residual stress at the T-shaped weld is relatively large. Weld metal is prone to stress effects that increase the likelihood of cracking.

Compared with straight seam steel pipes, spiral steel pipes have certain advantages in strength. The main process for producing spiral steel pipes is submerged arc welding. Spiral steel pipes can be used to produce welded pipes of different diameters from blanks of the same width, and it can also be used to produce welded pipes of larger diameters from narrower blanks. However, the length of welded pipe is increased by 30-100% compared to straight seam pipe of the same length. Due to the above reasons, the production rate of spiral steel pipe is very slow. Therefore, straight seam welding is mainly used for small diameter welded pipes, and spiral welding is mainly used for large diameter welded pipes.

In addition, different from straight seam welded pipe,according to the submerged arc welding process specification, each weld should have an arc initiation point and an extinction point. However, when welding the circumferential seam, each straight seam steel pipe cannot satisfy this condition. Therefore, there may be more welding defects at the arc extinguishing point. When a pipe is subjected to internal pressure, two principal stresses, radial stress and axial stress, usually develop on the pipe wall.

The above is the difference between the two steel pipes

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