棒金属がピンチ効果で移行する場合の高速度写真

Abstract

With the aid of high speed motion pictures taken by the American investigators, it has now become clear that in inert gas shielded metal arc welding, the molten metal of electrode tip transfers to the base metal in a fine spray form. The same phenomenon is very likely to occur in the submerged arc welding which utilizes heavy current as well. This is to supplement to our earlier works and to show what is happening in manual open arc welding at high current densities.Fig. 1 to 4 and Fig. 6 to 8 show the case of 4mm diameter bare steel electrode at 250A and 150 or 140A DCSP respectively, the speed of pictures being 720 exposures per second. At normal welding current i. e. 140 or 150A, molten metal accumulates at the electrode tip when the arc length is held long enough to limit the mechanical contact between electrode and base metal, and it finally drops off the tip due to gravity. At higher current densities, the pinch effect-hydrostatic squeezing action generated in a liquid conductor due to electromagnetic force-become more predominant than the restraining force due to surface tension, and beyond a certain critical current, electrode metal is torn off quickly and is transfered to the base metal in fine sprays. In one of our pictures such pinching off took place 21 times in 0.4 second at 250A DCSP.These photos were taken in prewar days, and many other phenomena that were found in ordinary welding conditions were already reported in the Journal of Welding Society in Japan.