Electrical Conductivity and Melt Structure of the CaO–SiO2–Based Mold Fluxes with Different Basicity

External fields, such as magnetic and electric, are applied to the continuous casting mold to improve the quality of casting products. The performance of the mold flux should also be impacted when these external fields are applied in the mold. The extent of the impact is associated with the electrical conductivity. So, in this study, the electrical conductivity of the mold fluxes with various basicity was measured using the AC four-electrode method. The results show that the electrical conductivity of the mold flux increased while its activation energy decreased with the increase of basicity from 0.8 to 1.1, at 1423 K to 1573 K. In addition, the analyses of Fourier-transform infrared (FTIR) and Raman spectroscopies show that the complex structural units, such as Q3(Si), Si–O–Si, Si–O–Al, and Al–O0, reduced with the increase of basicity. So the melt structure of the mold flux was simplified by the addition of CaO and reduction of SiO2. From the variations of electrical conductivity and melt structure, it can be concluded that it is due to the simplification of melt structures of the mold flux by the increase of basicity, which promotes the diffusion of ions/ionic groups, and then leads to the increase of electrical conductivity.