Estimation of escape rate of volatile components from slags containing CaF₂ during viscosity measurement

Abstract

In continuous casting process, the viscosity of the mould powder/flux has direct impact on the size of the gap between the mould wall and the solidified shell, which in turn affect the heat transfer characteristics between the metal and the mould. Numerous experiments have been conducted to determine the viscosity of various mould powders using rotation cylinder method. The pre‐melting of the mould powder as well as the viscosity measurement are carried out in a cylindrical crucible placed in a tubular furnace with constant argon flow to maintain inert atmosphere. One of the main difficulties encountered during viscosity measurement is the liberation of volatile fluorides, which in turn changes the flux composition, and consequently the viscosity of the flux. Thermodynamic calculations have shown that SiF 4 and HF are major constituents of the volatile matter. Present study aims to estimate the liberation rate of SiF 4 and HF from flux samples during viscosity measurement by computing the detailed gas flow pattern inside the tubular furnace. The gas flow pattern is computed by solving momentum and continuity of equations. Further, the effect of argon gas flow rate and slag level in the crucible on liberation rate has been studied to arrive at proper experimental conditions during viscosity measurement.