The weld seam of the
spiral steel pipe is longer than that of the straight seam steel pipe. If the pipe length is L, the weld seam length is L/cos(θ). However, most of the defects of steel pipes are concentrated in the weld seam and the heat-affected zone. The long weld seam means that the probability of defects is high. Straight seam steel pipe, especially the question of who is superior compared with UOE steel pipe.
Spiral steel pipe manufacturing technology has developed to this day, we should evaluate and compare comprehensively and correctly, and re-understand the problem of the long weld seam of spiral steel pipe.
First of all, because the defect is parallel to the weld, so for the spiral steel pipe, the defect of the weld is an "oblique defect". During use, the principal stress direction of the steel pipe, that is, the equivalent defect length in the axial direction of the steel pipe is smaller than that of the straight seam steel pipe;
Secondly, since the pipeline steels are all rolled steel plates, the impact toughness has a large anisotropy, and the CVN value along the rolling direction can be 3 times higher than that perpendicular to the rolling direction.
The main stress of the straight seam steel pipe is just perpendicular to the direction of the pipe's impact resistance, while the spiral steel pipe staggers the direction of the pipe's impact resistance, turning the disadvantage of the long weld seam of the spiral steel pipe into an advantage.
