1. Welding process:
In terms of the welding process, the welding methods of spiral steel pipes and straight seam welded pipes are the same, but straight seam welded pipes inevitably have many T-shaped welds, so the probability of welding defects is greatly increased, and the welding residual stress at T-shaped welds is larger. , the weld metal is often in a three-dimensional stress state. This increases the likelihood of rupture. In addition, according to the process requirements of submerged arc welding, each weld should have arc starting and arc extinguishing points. However, during circumferential seam welding, each straight seam welded pipe cannot meet this condition, so there may be arc extinguishing points. There are more welding defects.
2. Strength characteristics:
When a pipeline is subjected to internal pressure, its wall surface usually has two main stresses, namely radial stress and axial stress. The resultant stress at the weld is δ, where α is the helix angle of the spiral steel pipe weld. The helix angle of the spiral steel pipe weld is generally degrees, so the resultant stress at the spiral weld is the main stress of the straight seam welded pipe. Under the same working pressure, the wall thickness of spiral welded pipes with the same diameter is smaller than that of straight seam welded pipes.
3. Static explosion strength:
Comparative test results show that the yield pressure of spiral steel pipes and straight seam welded pipes are consistent with the measured and theoretical values of burst pressure, and the deviations are very close. The yield pressure and burst pressure of spiral steel pipes are lower than those of straight seam welded pipes. The blasting test also shows that the circumferential deformation rate of the blast hole of the spiral welded pipe is significantly greater than that of the straight seam welded pipe. The results show that the plastic deformation ability of spiral welded pipes is better than that of straight seam welded pipes. Since spiral welded pipes have a strong inhibitory effect on crack expansion, blast holes are generally limited to one pitch.
Post time: Dec-27-2023