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 melting wire flux.
In the process of use, the principal stress direction of the thick-walled spiral steel pipe, that is, the equivalent defect length in the axis 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, have been debated for a long time, firstly, because the defect is parallel to the weld, so for the spiral steel pipe, the defect of the weld is "oblique defect", and secondly, because the pipeline steel is all 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 more superior problem, the 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 welding seam of the spiral steel pipe.
The principal stress on the thick-walled spiral steel pipe is just perpendicular to the direction of the impact resistance of the pipe. Spiral seam steel pipe, while the spiral steel pipe staggers the direction of the impact resistance of the pipe, which turns 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 formed by continuous bending, the fixed length of the steel pipe is not limited; 2. As long as the forming angle is changed, the steel pipe of various diameters can be produced from the strip of the same width; 3. It is easy to change the size, suitable for small batches and multiple varieties The production of steel pipes; 4. The spiral shape of the welding seam is evenly distributed on the entire circumference of the steel pipe, so the dimensional accuracy of the steel pipe is high and the strength is also high.