How to deal with the weld of ERW pipe

　　ERW pipe is made by rolling low carbon structural steel or low alloy structural steel strip into tube blank according to certain helix angle, and then welding the tube seam. It can produce large diameter steel pipe with narrow steel strip. The specification is indicated by outer diameter * wall thickness, and the API 5L X52 Welded Steel ERW Pipe shall ensure that the hydrostatic test, tensile strength and cold bending performance of the weld meet the requirements.

　　The weld of ERW pipe is spiral distribution, and the weld is long, especially when it is welded under dynamic condition, the weld leaves the forming point before it cools down, which is very easy to produce welding hot cracks. The direction of the crack is parallel to the weld and forms an included angle with the steel pipe axis, generally between 30-70 °. This angle is just consistent with the shear failure angle, so its bending, tensile, compressive and torsional properties are far inferior to that of the straight submerged arc ERW pipe.

　　At the same time, due to the limitations of the welding position, the saddle shaped and fish shaped welds have an impact on the aesthetics. In addition, in the process of construction, the intersecting line weld at the joint of ERW pipe splits the spiral seam, which produces greater welding stress, thus greatly weakening the safety performance of the component. Therefore, the non-destructive testing of the ERW pipe weld should be strengthened to ensure the welding quality, otherwise, the spiral submerged arc ERW pipe should not be used in important steel structure occasions.