Dephosphorization in New Double Slag Converter Steelmaking Process with High-Temperature Laboratorial Experiments

The dephosphorization of hot metal with low basicity slag at 1623 K is investigated for new double slag converter steelmaking process (NDSP) using high-temperature laboratorial experiments. When the dephosphorization time is 15 min, the dephosphorization ratio reaches the highest value of 83.2%. When the dephosphorization times are 3 and 6 min, the main phases of dephosphorization slag are black phosphorus(P)-rich phase and white Fe-rich phase. When the dephosphorization times are 9, 12, and 15 min, the main phases are the P-rich phase, the Fe-rich phase, and the matrix phase. When the dephosphorization time is 18 min, the main phases are the Fe-rich phase, the matrix phase, and spinel phase containing MgO and Al2O3, but without the P-rich phase. With increasing the dephosphorization time, the area fraction of the Fe-rich phase in slag is continuously decreased and the area fraction of matrix phase is increased. The area fraction of the P-rich phase is first increased, then decreased until it is disappeared, due to its dissolution into the matrix phase at the low basicity of about 1.4.