The steel pipe produced by the process will have a white fusion line at the center of the weld, and the heat-affected zone on both sides of the fusion line will have a metal flow line extending from the middle to the inner and outer surfaces. Since the erw pipe is made of a base material as a welding material, the performance of the weld seam has a great relationship with the performance of the base material. In ordinary materials, the ductile-brittle transition temperature curve of the weld and the base metal. In ordinary materials, the difference in absorbed energy values between the weld and the base material in the Charpy impact test is small. On the contrary, there is a big difference in the high toughness material, and the weld impact toughness is obviously inferior to the base metal, but it is obviously superior to the weld of the ordinary material. It can be seen that the impact toughness of the weld center of the high-frequency steel pipe is generally lower than that of the base material. Even if the toughness material is used, although the toughness of the weld is improved, the impact toughness of the weld center cannot be completely improved.

Factors affecting weld impact toughness
The main factors affecting the impact toughness of welds are: (1) Physical and chemical properties of raw materials; (2) Crystal materials and non-metallic inclusions of raw materials; (3) Heat treatment conditions of welds; (4) Molding conditions; and (5) Welding conditions.