Spiral welded steel pipes all adopt the submerged arc welding process, straight seam welded steel pipes have submerged arc welded straight seam steel pipes for short UOE, and straight seam high-frequency resistance welding for short ERW.
Compared with submerged arc welding, the high-frequency resistance welded steel pipe (ERW steel pipe) does not add any welding materials during the welding process. Therefore, the formed weld is completely consistent with the chemical composition of the base metal. After the steel pipe is welded, it is annealed to make the internal stress of cold working, and the internal stress of the welding is improved, so the comprehensive mechanical properties of the ERW steel pipe are better. But at present, the manufacturers represented by Shanghai Ellison and Guangdong Panyu Zhujiang Steel Pipe Factory only produce pipes below φ355mm, and large-diameter gas pipelines cannot be selected. Longitudinal submerged arc welding (UOE steel pipe) uses the post-weld cold expansion process to expand the pipe, so the geometric size of the UOE steel pipe is relatively accurate, and the quality of the counterpart when the UOE steel pipe is connected is good to ensure the welding quality. Part of the internal stress is eliminated. In addition, multi-wire welding (three-wire, four-wire) is used for UOE steel pipe welding. This welding process generates less line energy during welding and has less influence on the heat-affected zone of the base metal. The post-pass welding wire of multi-wire welding can play a role in eliminating the stress generated during welding to the previous welding wire, thereby improving the mechanical properties of the steel pipe.
Compared with the spiral welded pipe, the length of the weld seam of the straight seam submerged arc welded steel pipe is shorter, so the welding defects and influences are relatively small. In the high-pressure pipeline, the base metal of the straight seam pipe can achieve 100% ultrasonic flaw detection of steel plates one by one, meeting the requirements of the high-pressure pipeline for the base metal. However, although the comprehensive performance of UOE steel pipe is better than other steel pipes, its high price makes users who are short of funds discouraged. The welds of the spiral steel pipe are distributed in a spiral shape. Generally speaking, the weld area of the steel pipe, including the heat-affected zone of the weld, is the part with poor mechanical properties of the steel pipe, while the maximum internal stress of the pressure pipe is distributed along the axial direction, and the spiral welded pipe will The weaker parts avoid the direction of maximum internal stress, thereby improving the performance of the steel pipe. In addition, due to the welding seam forming of the spiral steel pipe and the height of the welding seam, it is more difficult to do external anti-corrosion, and a gap may be formed between the two welding seams. The technology can solve the anti-corrosion of the spiral steel pipe.
Post time: Nov-02-2022