From the welding process, the spiral steel pipe with straight seam welding method is consistent, but inevitably there will be a lot of Longitudinal welds T, so there is the probability of weld defects, which is also greatly improved, and T-weld welding residual stress is large, the weld metal are often in a three-dimensional stress state, increasing the possibility of cracks.
Moreover, according to the provisions of submerged arc welding process, and each shall have the weld arc and arc extinction at office, but in each Longitudinal seam welding ring, you can not achieve this condition, which may be in extinction at more welding defects. Withstand the internal pressure in the pipe, usually in the wall on the two main stress, radial stressδand axial stress stressδ. Weld resultant stressδ, where, α is the helix angle of the spiral weld pipe. Spiral steel pipe welds degree helix angle is generally so stress is the synthesis of spiral weld Longitudinal principal stress. At the same pressure, the same diameter spiral welded pipe wall thickness can be reduced compared Longitudinal.
Based on the above characteristics seen: Spiral welded pipe blast the weld suffered stress and the resultant stress is relatively small, blasting mouth is generally not originated in the spiral weld, its security Longitudinal high. When the presence of nearby spiral weld defects parallel thereto, spiral weld force is small, so the risk of expansion as good as straight weld large. Since the radial stress is the maximum stress in the pipe, so the weld in vertical stress in this direction when under maximum load. Ie straight seam bear the load of the ring to weld to bear the load, the spiral in between.
Post time: Dec-03-2019