Thermodynamic Behavior and Mass Transfer Kinetics of Boron Between Ferrosilicon and CaO-SiO2 Slag

Equilibrium distribution and transport kinetics of boron between ferrosilicon and calcium silicate slag were investigated through experimental study. A 50 pct CaO-50 pct SiO2 slag (by weight) was held for different durations at 1873 K (1600 °C) in a graphite tube furnace together with boron-doped ferrosilicon alloys in the range 50 to 85 wt pct Fe. The results indicate that the equilibrium partition ratio of boron between slag and metal is 2.4 ± 0.7 and largely independent of ferrosilicon alloy composition below 85 wt pct Fe. At 85 wt pct Fe, the equilibrium partition ratio is measured to be 6.2 ± 1.4. Although reported with a significant standard deviation, it is also found that the mass transfer rate of boron between ferrosilicon alloy and slag increases slightly with increasing iron content in ferrosilicon. These findings are discussed in terms of slag–metal bulk and interfacial properties.