In Ar arc plasma melting of metal button, metal vapor mainly generates at outer region of anode spot. To make clear the relationship between the vaporization and the convection flow in bath, spectroscopic measurements were performed for determining the space distribution of vapor pressure of metal. Then the convection flow in bath was determined by motion of Y2O3 particles added to bath surface and EPMA analysis of cross sectional area.
There were two flows with different direction of motion in bath. They collided at about 7mm from central axis that is at the same position of maximum vapor pressure. Y2O3 particles were observed in the periphery owing to the outward flow. In the center of bath, it is considered that the inward flow is driven by electro-magnetic force. This flow carried the melt with high Ar content to the vaporization spot, and then an enhanced vaporization was operated due to transition of the Ar in melt to gas phase.
