1. The manufacturing process of the spiral tube determines that the residual stress is greater than that of the straight seam tube. Because the straight seam tube adopts the overall diameter expansion process, the residual stress is close to zero, and the spiral tube cannot do this.

2. The amount of misalignment of the spiral pipe weld is mostly in the range of 1.1~1.2mm, and the standard requirement is less than 10% of the wall thickness. For the thin-walled pipe, the amount of misalignment is difficult to meet the standard requirements, and the straight seam pipe does not exist. This problem.

3. Compared with the straight seam pipe, the spiral pipe weld seam is poor, and the stress concentration is serious.

4. The heat affected zone of the spiral pipe is larger than the straight seam pipe, and the heat affected zone is the key to the quality of the welded pipe.

5. Spiral tube geometry accuracy is poor, to the site construction, such as the counterpart, welding brings certain difficulties.

6. The same diameter, spiral welded pipe may reach a thickness much smaller than straight seam pipe, such as straight seam pipe thickness is generally 6 ~ 25mm, the thickest can reach 45mm, and the spiral pipe wall thickness can only reach 18mm.

7. Straight seam pipe welds are 60% shorter than spiral pipes, and the probability of weld defects is low.

8. Straight seam pipe base metal is a single controlled rolling steel plate, which can perform 100% non-destructive testing, while the spiral tube base material is hot rolled steel coil, which can not achieve 100% nondestructive testing.

9. Straight seam pipe adopts the process of first forming and then welding. Before the welding, it is possible to check the quality of the forming joint, the weld gap, the groove, the wrong edge, etc., and the spiral pipe adopts the process of welding while forming, even if In the welding process, it is found that there are defects such as wrong edges and slits, and it is difficult to stop the treatment at any time. It can be seen that the welding quality of the straight seam pipe is better than that of the spiral pipe.

Therefore, the overall performance of the process quality of the straight seam pipe is worried about the spiral pipe. However, the spiral tube cost is lower than that of a straight seam steel pipe rolled by a steel plate.