The spiral steel pipe is formed by spiral bending of strip or coil plate and is welded by double-sided submerged arc welding. Steel pipes are widely used in water, electricity and chemical industries for the following reasons.


1) As long as the forming angle is changed, steel pipes of various diameters can be produced with strips of the same width, which is convenient for transfer.
2) Because of continuous bending, the length of helical tube is unlimited and can be set arbitrarily.
3) Weld spirals are evenly distributed around the whole circumference of the spiral pipe, so the spiral pipe has high dimensional accuracy and strong strength.
4) Easy to change size, suitable for small batch, multi-variety spiral production.


The specification of spiral pipe is the same as that of straight welded pipe, and the wall thickness is the same. The spiral pipe bears the maximum pressure. The weld defect of spiral steel pipe is "oblique defect". In the course of using, the main stress direction of steel tube, that is, the equivalent defect length in the axial direction of steel tube is less than the main stress direction of straight tube. Secondly, the impact toughness of pipeline steel is anisotropic because it is rolled steel plate. The CVN value in the direction of pipeline steel can be three times that in the direction perpendicular to the rolling direction.