The spiral steel strip is formed by spiral bending of a steel strip or a spiral plate and is welded on both sides by submerged arc welding. Steel pipes are widely used in water, electricity, chemical industry and other industries for the following reasons.
1) As long as the molding angle is changed, steel pipes of various diameters can be produced using the same width of strip steel, which facilitates the type of transportation.
2) Since it is continuously curved, the length of the spiral tube is not limited, and the length can be arbitrarily set.
3) The welding spiral is uniformly distributed on the circumference of the spiral pipe, so the spiral pipe has high dimensional accuracy and strong strength.
4) Easy to change the size, suitable for small batches, more varieties of production screw.
Spiral steel pipe has the same specification length as straight welded pipe, and the wall thickness of the same specification makes the spiral steel pipe withstand the maximum pressure. Spiral steel pipe weld defects are "oblique defects." In the process of use, the direction of the principal stress of the steel pipe, that is, the equivalent defect length in the axial direction of the steel pipe is smaller than the defect length of the straight pipe. Secondly, due to the high anisotropy of impact toughness of the hot-rolled steel plate of pipeline steel, the CVN in this direction can be three times higher than the CVN value perpendicular to the rolling direction.
