2000 Volume 40 Issue 9 Pages 827-832
Study of plant analytical data for BOS and OBM processes revealed that the iron oxide content of slag has a decisive effect on the extent of steel dephosphorisation and desulphurisation. The slag/metal distribution ratios (%P)/[%P] and (%S)/[%S] from the plant data are scattered about the calculated equilibrium values for the slag–metal reactions involving the iron oxide content of the slag. The data also revealed consistent interrelations between the concentrations of FeO, CaO and SiO2 in the slag at the end of oxygen blowing. However, there are variations in the slag composition in the interrelations between the oxide contents: 5 to 6 % FeO and 4 to 5% CaO or SiO2 between the low and high values. These unpredictable variations in slag composition from one heat to the next bring about variations in the extent of steel dephosphorisation and desulphurisation. Consequently, the observed distribution ratios (%P)/[%P] and (%S)/[%S] are scattered within a slag composition range, bordered by the equilibrium curves for the low and high iron oxide contents with the corresponding CaO and SiO2 contents of the slag.
