Api 5l X52 From China

The welding principle of high frequency welded steel pipe is mainly based on the skin effect and proximity effect of high frequency current. Skin effect means that when high-frequency current passes through a metal conductor, due to electromagnetic induction, the current density is mainly concentrated on the surface of the conductor, while the current density inside the conductor is small. This effect enables high-frequency electric energy to concentrate on the surface of the weldment, thus rapidly heating the weld area. The intensity of skin effect is directly proportional to the current frequency. The higher the frequency, the higher the concentration of current on the conductor surface. Therefore, high-frequency welding usually uses a current with a frequency above 300kHz to achieve efficient heating of the weld area.