It is found that strong basic oxides including Li2O, Na2O, K2O and BaO, which are used to replace a part of CaO in CaO-based fluxes, can lower the melting point and the viscosity and enhance the dephosphorizing ability. The mechanism was analysed and the addition of Li2O to CaO-based fluxes was recommended.
The oxygen potential of ferromanganese melt can be measured by oxygen concentration cell using ZrO2 solid electrolyte stabilized by CaO (Mo-MoO2 as contrast electrode). The converted formula of oxygen potential and electromotive force is as follows: ln pO2=20.03-(69 548.8+46 427.7×E)/T. The temperature of desiliconization is 1 350 ℃. BF ferromanganese was desiliconized by the flux 1 which contents of BaCO3, MnO2 and (Fe2O3+CaF2) are 70 %, 5 % and 25 % respectively. When the treatment time is 15 min, Fe2O3 content is 12 % for obtaining maximum rate of desiliconization. The relation of oxygen potential and activity of carbon is as follows: pO2,m/TPa=35.812-0.106×aC. The relation of oxygen potential and manganese loss is as follows: pO2,m/TPa=6.238+0.679×ΔW［Mn］. When the flux 2 which contents of BaCO3, MnO2, BaF2 and Fe2O3 are 60 %, 15 %, 10 % and 15 % respectively is used to desiliconize ferromanganese, the time corresponding to maximum rate of desiliconizaion and maximum oxygen potential is 15 min. The experimental results show that oxygen potential is controlled by C-O reaction, and that oxygen potential for desiliconization and protecting manganese are 6.238 TPa.
