2020 Volume 38 Issue 4 Pages 438-447
In this study, to clarify effects of the rare earth metal (REM) on arc phenomena, observations of an arc appearance and a metal transfer during a gas metal arc welding using a REM added wire by a high-speed camera were conducted. Moreover, temperature measurements of the arc plasma were carried out using monochromators and high-speed cameras. As a result, the spray transfer mode was observed during the welding with the electrode negative polarity using the REM added wire when the shielding gas including CO2 gas was used. The globular transfer mode was obtained during the welding when 100%Ar gas was used as a shielding gas. These results showed the reverse tendency compared with a conventional gas metal arc welding using the electrode positive polarity. Moreover, the droplet frequency increased largely in the range of 220A to 260A during the gas metal arc welding with the electrode negative polarity using the REM added wire when the shielding gas including CO2 gas was used. From these results, it was suggested that the spray transfer mode during CO2 gas arc welding and metal active gas welding was obtained by two factors. One was the operation and stabilization of the hot cathode by the welding with the electrode negative polarity using the REM added wire, and the other was the increase of temperature of the molten metal droplet and constriction of arc and arc root by the thermal pinch effect.
