高電流・高速MIG溶接における溶融池現象に関する研究

Abstract

The authors have studied the mechanism of formation, taking note of the discontinuous bead, particularly humping bead at high current and high speed welding. Following facts are clarified.1. In high current and high speed welding, the difference of temperature between the front part and the rear part of the molten pool is much greater than that in ordinary welding and this temperature difference causes strong surface-tension-stream directing from the front to the rear part of the pool resulting in the discontinuity of the bead.2. The authors have investigated some methods to prevent the formation of the discontinuous at high speed welding. The basic conceptions are as follows:a. Gravity control of the streamb. Decrease of temperature difference between the front and the rear part of the molten poolc. Decrease of surface tension of the molten poolThese methods aim to repress the strong stream from the front to the rear of the molten pool.For example, by elongating wire extension the arc takes the form of so-called rotating arc, which heats the molten pool uhconcentratively different from concentrative heating of spray arc and acts to prevent discontinuity of the bead. Fig. 5 shows the critical relation to get continuous at high speed welding. This curve is applicable to every diameter of wire.3. The authors analized (see equ. 4) of the and clarified the relation between efficiency and character. The results show that the welding speed at maximum melting efficiency is the limit to form the continuous bead.