How to improve the impact toughness of spiral steel pipe welds

　　How to improve the impact toughness of spiral steel pipe welds is a major problem in the technology of pipe making. On the basis of mass production practices, various factors affecting the impact toughness of spiral steel pipe welds were analyzed. It is pointed out that in order to further improve the impact toughness of welds and meet the high toughness requirements of long-distance pipelines for spiral steel pipes, it is necessary to start with the control of the quality of raw material coils, combined with the pipe-making process, and strengthen the quality control of forming, welding and on-line heat treatment after welding. .

　　The welding process of X65 DIN Carbon Welded Spiral Steel Pipe uses the principle of skin effect produced by high-frequency current to heat the edge of the hot rolled plate to the molten state, and then it is welded by the mechanical extrusion method. A white fusion line appears at the center of the weld seam of the steel pipe produced by this process, and the heat affected zone on both sides of the fusion line will generate a metal flow line extending from the middle to the inner and outer surfaces. As the spiral steel pipe uses the base metal as the welding material, the performance of the weld seam is greatly related to the performance of the base metal. In ordinary materials, there is little difference in the absorbed energy value of the Charpy impact test between the weld and the base metal. On the contrary, there is a big difference in high-toughness materials.