Protective Properties of SF6 under Various Carrier Gases for the Protection of Molten Mg

Molten magnesium can oxidize rapidly in atmospheres containing oxygen. During the casting and handling of molten magnesium, it is essential to protect the melt from ignition. The protective gas normally contains air and/or CO2, and with a small amount of an inhibiting agent. This study examined the minimum amount of SF6 gas needed depending on the type of carrier gas, as well as the effects of the melt temperature, exposure time and SF6 concentration on the surface film of molten magnesium. The analysis methods of the surface film included the XPS/depth profile and SEM/EDS. The minimum amount of SF6 gas concentration determined over a wide a range of different carrier gases, such as air, N-2 and CO2. The surface film thickness decreased with increasing SF6 concentration under all conditions, such as the melt temperature, exposure time and different carrier gas.