A method for the improvement of the sulfidic and oxidic degree of purity of deoxy, which is oxidized and / or with desulfurizing agent treated steel melts

摘要

The sulphide and oxide contents of molten steel are reduced, where the steel has been deoxidised and/or treated with an agent to remove sulphur. After deoxidn. and/or desulphurisation, the fine suspended particles in the melt are coagulatd and removed by blowing a mineral mixt. of CaO, SiO2 and Al2O3 into the molten steel. The mineral mixt. may also contain MgO and pref. has a m.pt. of 1300-1400 degrees C.; it should only have a low content of iron and manganese oxides. The mixt. is pref. made by melting the constituents, then solidifying and milling to max. size 0.5 mm. Pref. 0.75-2.5 kg of the mixt. is used per tonne of steel, the pref. mixt. contg. 42% CaO, 35% SiO2, 11.5% Al2O3, balance MgO and 3-4% of other constituents. The mixt. is neutral, and coagulates the fine inclusions without detriment to the quality of the steel. The operation can be conducted in a ladle in 4-12 minuts and combined with sulphur removal.