Study on the Occurrence of Phosphorus in the Slag of Hot Metal Dephosphorization for Stainless Steel Production

Abstract

The dephosphorization process for producing stainless steel hot metal is divided into desiliconization period and dephosphorization period, and the ability to contain phosphorus in the slag is important for the dephosphorization effect of hot metal. The phase structure of the slags during the desiliconization and dephosphorization phases is studied by X‐ray diffraction (XRD), petrographic analysis, and scanning electron microscopy (SEM). The ability of slag to contain phosphorus during the slagging process of calcium ferrite is discussed. The final slag petrographic composition in the desiliconization stage is mainly free calcium oxide, dicalcium silicate and calcium phosphate solid solution, RO phase, calcium ferrite and metallic iron. The final slag petrographic composition in the dephosphorization phase is mainly composed of tricalcium silicate, dicalcium silicate and calcium phosphate solid solution, RO phase, dicalcium ferrite and free calcium oxide. Compared with the desiliconization phase, the crystal phase obtained during the dephosphorization phase is more stable. The terminal ferrous slag phosphorus in calcium ferrite slag system mainly exists in the form of 2CaO⋅SiO2−3CaO⋅P2O5 solid solution, whereas the content in other phases is small.