Abstract
In most cases, the slag used in hot metal dephosphorization exists in a solid–liquid coexisting state, containing dicalcium silicate as the solid phase. It is known that dicalcium silicate (C2S) and tricalcium phosphate (C3P) form a solid solution with a wide range of composition. A large distribution ratio of P2O5 between a solid solution and liquid slag phases has also been reported. To clarify the maximum concentration of P2O5 in this solid solution phase, the measurement of the distribution ratio of P2O5 in slag containing a high concentration of P2O5 is performed in this research, and the influence of MgO and MnO on the distribution ratio is investigated. CaO–SiO2–Fe2O3 slag containing a maximum of 18% P2O5 is melted at 1873K and cooled to 1673K at a cooling rate of 10K/min. During cooling, the solid solution of dicalcium silicate and tricalcium phosphate precipitates from the liquid slag. A good relation is found between the distribution ratio of P2O5 and (T.Fe); this relation is independent of slag composition and P2O5 content. The concentration of P2O5 in the solid solution is strongly influenced by the mixing ratio of P2O5 and the slag composition. It is clarified that if the slag composition is controlled adequately, the concentration of P2O5 in the C2S–C3P solid solution can be increased up to 100% of C3P. The change in the distribution ratio with the addition of MgO and MnO is not large.
