Spiral seam submerged arc welded steel pipe product details

The strip steel is bent into a spiral shape, and the inner and outer seams are welded by submerged arc automatic welding to make a spiral seam steel pipe. It is widely used in the production of large-diameter steel pipes for 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 fixed length of the steel pipe is not limited;

3) 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;

4) The equipment is cheap, easy to change size, and suitable for the production of small batches and multiple varieties of steel pipes. Spiral pipe weld ratio

Straight seam pipe length, if the pipe length is L, the weld length is L/cos(θ). Most of the defects in steel pipes are concentrated in the welds and heat-affected zones. Long welds mean a high probability of defects. This is the main reason that has long restricted the wider application of spiral welded pipes. It is also the long-term debate between spiral pipes and spiral welded pipes. Straight seam pipes, especially the question of who is superior compared with U0E steel pipes. With the development of spiral pipe manufacturing technology today, we should evaluate and compare comprehensively and correctly, and re-understand the problem of long spiral pipe welds. First of all, because the defects are parallel to the weld, for spiral pipes, the weld defects are "oblique defects". During use, the main stress direction of the 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; secondly, because the pipeline steels are all rolled steel plates, the impact toughness has greater anisotropy, along the rolling direction The CVN value can be 3 times higher than the Cw value perpendicular to the rolling direction. The main stress on the straight seam pipe is exactly perpendicular to the direction of the pipe with the lowest impact resistance, while the spiral pipe is staggered in the direction of the pipe with the lowest impact resistance, turning the disadvantage of the spiral pipe's long weld seam into an advantage.