Second, because the pipeline steel is a rolled steel plate, the impact toughness has a greater anisotropy. 3 times higher. The vast majority of steel pipe defects are concentrated in the weld and heat affected zone. During use, the main stress direction of the steel pipe, that is, the steel equivalent defect length in the pipe axis direction is shorter than that in the straight seam pipe.
It can be 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 calibers can be produced from strips of the same width;2) Because it is continuously bent, the fixed length of the steel pipe is not limited;3) The weld 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 high;4) The equipment cost is cheap, easy to change the size, suitable for the production of small Pipe Fittings Flanges Wholesalers batches and multiple varieties of steel pipes. First of all, because the defect is parallel to the weld, the defect of the weld of the spiral tube is an "inclined defect". This is the main reason that has restricted the wider application of spiral welded pipes for a long time.
The length of the weld means that the probability of the occurrence of the defect is high. The main stress on the straight seam pipe is exactly perpendicular to the direction of the lowest impact resistance of the pipe, while the spiral pipe staggers the direction of the lowest impact resistance of the pipe, which turns the disadvantage of the weld length of the spiral pipe into an advantage. The CVN value in the rolling direction can be greater than the CVN value perpendicular to the rolling direction.The strip is formed in a spiral shape, and the inner and outer seams are welded by submerged arc welding to make a spiral seam steel pipe.To date, the development of spiral tube manufacturing technology should be comprehensively and correctly evaluated and compared to re-understand the problem of long spiral tube welds. Rotary tube and straight seam tube, especially who is superior to UOE steel pipe. If the pipe length is L, the weld seam length is L / cos (θ).
.The weld seam of the spiral pipe is longer than that of the straight seam pipe