Deep Dephosphorization of Liquid Steel with CaO-CaF_2-FeO Slag

In order to produce ultra-low phosphorus steel, the deep dephosphorization experiment of steel containing phosphorus about 0.01 % outside BOF was carried out by high basic slag of CaO-CaF_2-FeO at 1 600 ℃. The effect of process factors (oxidizability, basicity, etc.) on dephosphorization was analyzed and the appropriate composition of the flux was determined. The results show that oxidizability and basicity have reverse effect on dephosphorization and the dephosphosphorization ratio of 50 % and phosphorus content of 0.005 % or 0.002 7 % can be obtained by using this kind of flux when the initial phosphorus content in the liquid steel is about 0.01 %. The primary industrial trial in 300 t converter shows that 50 % dephosphorization ratio and phosphorus content of 0.006 % in finished steel are obtained.