Effects of magnetic field on arc stability, weldability and mechanical properties of welded joints under high pressure atmosphere by TIG arc welding process were investigated. As the magnetic field, the longitudinal magnetostatic field and the alternating fields of several frequencies were used. As the result, it was made clear that arcs under high pressure were stabilized by the magnetic field and therefore sound welds can be obtained easily. Especially the alternating field seems to be better for the improvement of bead appearances in high pressure TIG welding.
Underwater dry welding for the construction and the repair of offshore structures were studied widely 1–4). The author has been studying on effects of argon and helium pressure on welding phenomena and welding results by the TIG arc welding process and the gravity arc welding process 5–10). As the result, it is made clear that relatively sound welds can be obtained using optimum welding conditions by these welding processes. However, generally the arc becomes unstable and consequently the appearances of weld beads have tendency to fluctuate under the He pressure more than 2.1MPa. Therefore, it is important to develop new processes to stabilize the arc under high pressure. On the other hand, some papers have reported that the application of magnetic field to an arc makes possible to stabilize the arc in high speed TIG welding or to improve mechanical properties of welded joints 11 – 15). Therefore, the author has tried the application of the magnetic field to the arc under high pressure atmosphere in order to stabilize it and to improve the weldability. In this report, effects of the longitudinal static and alternating magnetic field of several frequencies on arc phenomena and welding results under the pressure range up to 3.1MPa were investigated experimentally.
