PHOSPHORUS PARTITION BETWEEN FE-CR-C MELTS AND BAO-BAF2 FLUXES AND THE ACTIVITY OF BAO

The phosphorus partition between BaO-BaF2 fluxes and Fe-Cr-Csatd. alloys was measured at temperatures ranging from 1 175°C to 1 300°C under a CO atmosphere. The phosphorus partition ratio increases with increasing BaO content in the fluxes and decreases with increasing chromium content in Fe-Cr-Csatd. alloys. The BaO-BaF2 system has a large phosphate capacity ranging from 1026 to 1028.5 at 1 300°C, which is larger than that for the CaO-CaF2 system. The enthalpy change for the dephosphorization reaction by BaO-bearing fluxes was -528 kJ/mol. The chromium partition ratio increases with an increase in BaO content especially in the higher BaO content range. The possibility of the removal of phosphorus from Fe-16% Cr-C alloys without much oxidation loss of chromium by using 50% BaF-50% BaF2 flux was demonstrated. The activity of BaO for the BaO-BaF2 system was determined at 1 200°C and 1 300°C and the activity of BaF2 was calculated by using the Gibbs-Duhem relationship. The phase diagram for the BaO-BaF2 system is also discussed.