By testing in a 15 kg vacuum induction furnace it is obtained that there is obvious dephosphorization effect by respectively adding Li

2

O

CaF

2

Na

2

O and K

2

O in CaO base dephosphorization slag series

of them the CaO base slag containing 5% 10% Li

2

O has optimum dephosphorization results. The results of commercial pilot production of 120 t top and bottom combined blowing converter with double slag operation show that as compared with the earlier stage slag without adding lepidolite (/% : 34.58 kg/t lime

5.41 kg/t dolomite and 3.13 kg/t si

nter) in earlier stage of dephosphorization based on adding 31.46 kg/t lime

3.70 kg/t dolomite and 0.70 kg/t sinter

with adding 13.88 kg/t lepidolite mineral (/% : 56.41SiO

2

3.80FeO

4.50Na

2

O

4.17K

2

O

3. 18Li

2

O) the oxidizability of converter end slag is lower

the average dephosphorization rate and phosphorus equilibrium distribution coefficient of converter semi-steel is respectively 1.67 time and 2.81 times that without adding lepidolite

the converter end dephosphorization rate and phosphorus equilibrium distribution coefficient is respectively 1.02 times and 1.47 times that without adding lepidolite

as compared with nonadding lepidolite the converter blowing end [P

]

decreases from 0.009%-0.011% to 0.005%-0.006% to meet the requirement of ultra-low phosphorus steel.