Study on mineralogical structure of dephosphorisation slag at the first deslagging in BOF steelmaking process

The mineralogical structure of dephosphorisation slag at the first deslagging was studied by SEM–EDS, XRD and FactSage 7.0. The results show that the slag which is favourable for the enrichment of Si, Ca and P has good dephosphorisation ability. While the slag that is favourable for the enrichment of Fe and O show poor dephosphorisation ability. The main mineralogical structure in liquid slag phase is 2CaO·SiO₂ and 2CaO·SiO₂–3CaO·P₂O₅, which is favourable for dephosphorisation. The values of and increase with increasing the mole fraction of P₂O₅ in the solid solution phase and in the liquid slag phase, and increasing the temperature of the first deslagging. The value of increases with the increase of FeO content and slag basicity, but decreases with the increase of FeO content and basicity of solid solution phase.