Electrical Conductivity of Molten Slags for Electro-slag Remelting

A four electrodes method with alternative current has been developed for measurement on the electrical conductivity of ionic melts at high temperatures, especially for that of CaF2-based slags for electro-slag remelting (ESR). The electrical conductivity was measured systematically for CaF2-based slags containing MgF2, BaF2, CaO, BaO, Al2O3, TiO2, ZrO2, and CaS. From the results, the conduction mechanism of those slags was discussed in terms of molar conductivity. The molar conductivity of CaF2 melt was changed with the addition of alkaline-earth oxides and fluorides, such as MgO, CaO, BaO, MgF2, and BaF2 in accordance with the intensity of cation-anion attraction. It suggests that those additives have a tendency to behave as ionic pairs in the melt. The remarkable decrease on the electrical conductivity of the melts was observed by the addition of some oxides, such as Al2O3, TiO2, SiO2, and ZrO2 into the melts. It suggests that those additives have a tendency to form oxyfluoride complex ions. An empirical equation was proposed for the calculation of the conductivity of multi-component slags for the ESR process.