Thick-walled spiral steel pipe is a method of arc welding under the flux layer. It 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 melted welding wire flux.

During use, the main stress direction of thick-walled spiral steel pipes, that is, the equivalent defect length in the axis direction of the steel pipe, is smaller than that of straight seam pipes; if the pipe length is L, the weld length is L/cos(θ). There has been a long-standing debate between spiral steel pipes and straight seam pipes. First, because the defects are parallel to the welds, for spiral steel pipes, the defects in the welds are “oblique defects”. Secondly, pipeline steels are all rolled steel plates. , the impact toughness has 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 seam of spiral steel pipe is longer than that of straight seam pipe, especially compared with UOE steel pipe A more superior problem, with the development of spiral steel pipe manufacturing technology today, we should evaluate and compare comprehensively and correctly, and re-understand the problem of long spiral steel pipe welds.

The principal stress on thick-walled spiral steel pipes is exactly perpendicular to the direction of the pipe’s impact resistance. Spiral seam submerged arc welded steel pipes are formed by bending hot-rolled strip steel in a spiral shape, and the inner and outer seams are welded by automatic submerged arc welding. It is formed into a spiral seam steel pipe, and the spiral steel pipe staggers the direction of the pipe’s impact resistance, turning the disadvantage of a 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 continuously bent and formed, the fixed length of the steel pipe is not limited;
2) As long as the forming angle is changed, steel pipes of various diameters can be produced from strip steel of the same width;
3) Easy to change size, suitable for the production of small batches and multiple varieties of steel pipes;
4) The welds are spirally distributed evenly over the entire circumference of the steel pipe, so the steel pipe has high dimensional accuracy and high strength.