Abstract: Together with the condition that the average phosphorus mass fraction is 0.16% in molten iron of Chongqing Iron & Steel （Group） Co.，Ltd., average dephosphorization rate couldn’t exceed 90% with single slag method in 80t converter. Considering that (FeO) can transfer oxygen at steel-slag interface, the effect of slag basicity and w(FeO) on the C-P selective oxidation temperature was studied through calculation. Based on dephosphorization thermodynamics and the meltability of slag which represents kinetics at the later blowing stage of BOF, the effects of two parameters on the dephosphorization rate were studied. The first is difference between the end-point temperature of BOF molten steel and C-P selective oxidation temperature, and the second is superheat of slag. In addition, the suitable slag basicity and w(FeO) were determined when the end-point temperature of BOF molten steel was given. The results show that with the temperature difference decrease a 10℃, the dephosphorization rate increase by 1.2%. When the end-point temperature of BOF molten steel is about 1640℃, basicity is controlled in the range of 4.2 to 4.55, and w(FeO) of end steel slag is between 23% and 27%, the dephosphorization rate reaches over 90%.

Key words: converter, dephosphorization, C-P selective oxidation temperature, end-point temperature