On the Dephosphorization of Carbon-Saturated Iron by Calcium Sulfate Flux

Abstract

The effect of temperature (1250-1450°C), silicon and manganese in carbon-saturated iron (0.1% P, 0.05% S) on the dephosphorization was studied by using the flux of the CaSO₄-CaCO₃system. It was found that CaSO₄, although it is in solid state, has the strong dephosphorizing power. The following dephosphorization reaction was derived from the results of EPMA analysis for the dephosphorized reaction products;
7/2CaSO₄ (s) +2P= 3CaO·P₂O₅ (s) +1/2CaS (s) +1/3SO₂No effect of the oxidation of silicon on the degree of the dephosphorization and no reversion of phosphorus and sulfur were observed, but the remarkable sulfur increase in metal was found as a result of the reactions of CaSO₄with carbon, phosphorus and silicon. To use this flux for the dephosphorization of hot metal, all efforts were made to prevent such sulfur absorption by adding CaF₂, Na₂CO₃and CaC₂.