Effect of multi-phase slag on dephosphorization in BOF steelmaking

Abstract

In basic oxygen furnace double slag process, the slag shows a coexisting state of both liquid and solid. In order to study the effect of multi-phase slag on dephosphorization, heat experiments were conducted in this study, and the multi-phase slag was analyzed with the method of SEM-EDS. The results show that the mass fraction and size of solid solution increase with increasing basicity and decreasing FetO concentration. The distribution of P2O5 (LP2O5) between the solid solution and liquid phase increases with the T.Fe content in the liquid phase. While the increase of CaO content in liquid phase shows the opposite effect. A higher CaO content in liquid phase brought a decrease in γP2O5. The increase of T.Fe content in liquid slag has no notable effect on γP2O5 of dephosphorization slag, but increases γP2O5 of decarburization slag. The partition ratio of phosphorus between slag and steel (LP) increases with the increase of basicity, for conditions of FetO content in dephosphorization slag less than 25%. In the case of basicity of 3.0, LP reaches a maximum at FetO = 15%. When the basicity is 3.5 and 4.0, LP value is the largest at FetO of 15% or 20%.