Solubility of Oxygen in Iron-Silicon Melts in Equilibrium with Silica at 1873 K

Abstract

The solubility of oxygen in iron-silicon melts in equilibrium with silica was measured within the range from 0.1 up to 70mass% Si at 1873 K. The experimental procedure involved alloys melting in silica crucibles under argon atmosphere. The sampling was made by melt sucking into quartz tubes, equipped with copper chillers. The oxygen content of analytical samples was determined with inert gas fusion analysis after careful sample preparation. The results obtained were treated by thermodynamic model, which allowed to calculated the activity and solubility of oxygen in Fe-Si melts up to 100 mass% Si. The isotherm of oxygen solubility exhibits both intermediate minimum and maximum at 20 and 85 mass% Si, respectively. The corresponding values of oxygen saturated contents are as follows: 1.4 and 94 μg/g. The activity coefficient of oxygen shows alternating deviations from the additive behaviour. These are positive in the iron rich melts, containing up to 45 mass% Si. In the melts with higher silicon content the deviations from additivity are negative. The following values of interaction parameters were calculated: e S i O ( F e ) =12.9′2.7 and e F e O ( S i ) =-6.5′2.0.