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ABSTRACT
Laser-arc hybrid welding is divided into laser-based and arc-based welding. In the arc-based welding, the laser beam irradiation provides the guiding effect to the arc plasma. Some studies have reported that an unstable arc plasma becomes stable due to this guiding effect. This is considered as the influence of metal vapour generation by laser beam irradiation; however, there are few reports on the measurement of metal vapour and arc plasma state during the guiding process. Therefore, the mechanism has been still not fully understood. In this study, the fundamental study of the guiding arc phenomenon was conducted in TIG arc welding (60 A) with laser beam irradiation (170 W) under relatively low-power condition. When the base metal was stainless steel, the guiding arc by the laser beam irradiation was observed which did not happen with mild steel. Spectroscopic measurement for the guiding arc phenomenon in stainless steel showed that the metal vapour was composed of manganese and chromium, and was widely distributed near the irradiation point, but not concentrated. We also observed a reduction of plasma temperature, thought to be caused by distributed metal vapour and the resultant reduction of the current density.