Effects of additives in BaO-BaF-MnO slag on phosphate and manganese capacities

• Published in: ISIJ international 1998-01, Vol.38 (1), p.36-45
• Main Authors: Liu, X, Selin, R, Edstrom, J O
• Format: Article
• Language: English
• ISSN: 0915-1559

The effects of various additives (CaO, MgO, SiO sub 2 , CaF sub 2 and Al sub 2 O sub 3 ) in BaO-BaF sub 2 MnO slags on the distribution ratios of phosphorus and manganese between the slags and ferro manganese have been studied at 1300 deg C. The dephosphorization ability of BaO-BaCl sub 2 -MnO slag is also investigated. It is found that replacement of BaO with CaO or MgO causes a decrease in the phosphate capacity and an increase in the manganese capacity, and that substitution of BaF sub 2 with CaF sub 2 or SiO sub 2 results in a poor dephosphorizing ability and more losses of Mn from metal to slags. CaF sub 2 in BaO-BaF sub 2 -MnO slags strongly reduces the BaO activity, which diminishes the beneficial action of BaO in the slags of dephosphorization. Comparing with BaO-BaCl sub 2 -MnO slags, BaO-BaF sub 2 -MnO slags give a higher dephosphorizing capacity. Critical contents of different additives in BaO-BaF sub 2 -MnO slags to achieve an effective dephosphorization have been given. Based on the fact that the relationships between optical basicity and the phosphate and Mn capacities are only valid in a restricted range of slag compositions, the relationships between the capacities and optical basicity and slag composition have been derived by considering the interaction of slag components and analyzing a host of experimental data from different authors. These relationships are expected to be useable in a wider range of slag compositions and temperatures and to predict the phosphorus and Mn contents in metal without serious error.