Phase equilibrium for the CaO-SiO₂-FeO-P₂O₅ system at 1673 K for dephosphorization with multi phase flux

Development of the efficient hot metal dephosphorization processes during steelmaking process is one of the most essential topics for the production of high grade clean steels. Since the formation of solid solution composed of tricalcium phosphate and dicalcium silicate could obtain a considerable mass transfer of phosphorus from liquid slag into solid phase during hot metal dephosphorization, it could obviously sustain a high phosphate capacity of the liquid slag without huge consumption of lime or addition of fluxes, such as fluorite. The above outlines are the main idea of multi phase flux dephosphorization. For the last few decades, many studies have been done towards the scientific principles and the commercial utilization of this technique. However, the reaction mechanism by using multi phase fluxes remains unclear even by now due to lack of evidence. Based on those previous works, providing a reliable and available phase diagram for the fundamental understanding of the reaction mechanism of multi phase flux dephosphorization has become the main purpose of present research. As well known, the CaO-SiO₂-FeO-P₂O₅ slag is the main component of current steelmaking process. Hence the CaO-SiO₂-FeO-P₂O₅ system at equilibrium has been studied at 1673 K with low oxygen partial pressure. The solid phase coexisting with liquid flux is approved to be the solid solution composed of CaO, SiO₂ and P₂O₅. Phosphorus distributes mainly in solid solution rather than liquid phase.