Abstract: The control of dephosphorization slag is the key point in the dephosphorization stage of the new double-slag converter steelmaking process. In order to study the effect of basicity and total Fe content of the dephosphorization slag on the composition and proportion of slag phase, the industrial experiments of the new double-slag converter steelmaking process were carried out. Four dephosphorization slag samples with different basicities and total Fe contents were obtained by controlling the amount of the charged raw materials. The phase analysis and microscopic observation were carried out. The results show that the dephosphorization slag phase consists of P-rich phase and matrix phase. There is Fe-rich phase in the slag when the total Fe content is high. The P content in the P-rich phase is the highest, and the P content in the Fe-rich phase is the lowest. With the increase of basicity, the proportion of P-rich phase in the slag increases first and then decreases. The higher is the total Fe content in the slag, the higher is the proportion of the Fe_tO phase in the slag. When the P-rich phase accounts for about 40 %–50 %, the matrix phase accounts for about 13 %–35 %, and the Fe-rich phase accounts for about 23 %–35 %, it is favorable for dephosphorization in the new double-slag converter steelmaking process.

Key words: new double-slag converter steelmaking process, dephosphorization, slag phase, basicity, total Fe content