Thick-walled spiral steel pipe is a method of arc welding under the flux layer, which is formed by using the heat generated by the arc burning between the flux and the welding wire under the flux layer, the base metal, and the molten wire flux.
During use, the principal stress direction of the thick-walled spiral 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; if the pipe length is L, the weld length is L/cos(θ). The spiral steel pipe and the straight seam pipe that has been debated for a long time, firstly, because the defect is parallel to the weld, so for the spiral steel pipe, the weld defect is an "oblique defect". Secondly, because the pipeline steel is rolled steel plate, the impact toughness has a large anisotropy, the CVN value along the rolling direction can be 3 times higher than the CVN value perpendicular to the rolling direction, the weld of the spiral steel pipe is longer than that of the straight seam pipe, especially compared with UOE steel pipe The problem of superiority, the manufacturing technology of spiral steel pipe 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.
The main stress of the thick-walled spiral steel pipe is just perpendicular to the direction of the pipe's impact resistance. The spiral seam submerged arc welded steel pipe is formed by bending the hot-rolled strip steel in a spiral shape, and the inner seam and the outer seam are welded by automatic submerged arc welding. Spiral seam steel pipe, 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. It can be widely used in the production of large-diameter steel pipes for the following reasons:
1) Because it is continuous bending and forming, the length of the steel pipe is not limited;
2) As long as the forming angle is changed, the steel strip of the same width can be used to produce steel pipes of various diameters;
3) It is easy to change the size, suitable for the production of small batches and multiple varieties of steel pipes;
4) The welds are spirally and evenly distributed on the entire circumference of the steel pipe, so the steel pipe has high dimensional accuracy and high strength.