Review

Effect of multi-phase slag on dephosphorization in BOF steelmaking

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
² Jiuquan Iron & Steel (Group) Co., Ltd., Jiayuguan 735100, China

^* e-mail: chengsusen@metall.ustb.edu.cn

Received: 18 January 2023
Accepted: 15 April 2023

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 Fe_tO concentration. The distribution of P₂O₅ (L_P2O5) 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 γ_P2O5. The increase of T.Fe content in liquid slag has no notable effect on γ_P2O5 of dephosphorization slag, but increases γ_P2O5 of decarburization slag. The partition ratio of phosphorus between slag and steel (L_P) increases with the increase of basicity, for conditions of Fe_tO content in dephosphorization slag less than 25%. In the case of basicity of 3.0, L_P reaches a maximum at Fe_tO = 15%. When the basicity is 3.5 and 4.0, L_P value is the largest at Fe_tO of 15% or 20%.