Spiral Seam Submerged Arc Welded Steel Pipe

Introduction of commonly used steel pipes-spiral seam submerged arc welded steel pipe The strip steel is bent into a spiral shape, and the inner and outer seams are welded by automatic submerged arc welding to make spiral seam steel pipe. It can be widely used in the production of large diameter steel pipes due to the following reasons:

1) As long as the forming angle is changed, steel pipes of various diameters can be produced from strip steel of the same width;

2) Because it is continuously bent and formed, the cut-to-length length of the steel pipe is not limited;

3) The welding seam is evenly distributed in the spiral shape of the entire steel pipe circumference, so the steel pipe has high dimensional accuracy and high strength;

4) The equipment cost is cheap and the size is easy to change, which is suitable for the production of small batches and multiple varieties of steel pipes. The weld seam of the spiral pipe is longer than the straight seam pipe. If the pipe length is L, the weld seam length is L/cos(θ). The vast majority of steel pipe defects are concentrated in the weld seam and heat-affected zone. The long weld seam means that the probability of occurrence of defects is high. This is the main reason that has restricted the wider application of spiral welded pipe for a long time. Straight seam pipe, especially the question of who is superior to the UOE steel pipe. With the development of spiral pipe manufacturing technology today, we should comprehensively and correctly evaluate and compare, and re-understand the problem of long spiral pipe welds. First of all, because the defect is parallel to the weld, so for the spiral pipe, the defect of the weld is "oblique defect". During use, the main 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 pipe; secondly, because the pipeline steel is a rolled steel plate, the impact toughness has a larger anisotropy, and it is along the rolling direction. CVN value can be 3 times higher than the CVN value perpendicular to the rolling direction. The principal stress of the straight seam pipe is exactly perpendicular to the direction of the lowest impact resistance of the pipe, while the spiral pipe is staggered in the direction of the lowest impact resistance of the pipe, which turns the disadvantage of the long weld seam of the spiral pipe into an advantage.