MODIFICATION PURITY OF THE OXIDES AND SULPHIDES IN MOLTEN STEEL TREATED WITH DEOXIDATION AGENT AND OR DESULPHRIZING AGENT

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.