EVOLUTION OF THE COMPOSITION OF CaO-Al_2O_3-SiO_2 INCLUSIONS DURING ADDITION OF CALCIUM OR CALCIUM-SILICON INTO LIQUID STEEL

摘要

Basing on the data of Al_2O_3 and SiO_2 thermodynamic activities in SiO_2-containing calcium aluminates of three formulae, CaO centre dot Al_2O_3, 12CaO centre dot 7Al_2O_3 and 3CaO centre dot Al_2O_3 (shortly denoted as C_1A_1, C_(12)A_7 and C_3A_1), at 1873K for the wide range of SiO_2 mole fractions [1], we propose their activities expressed as functions of CaO contents provided there is no change in SiO_2 mole fraction. The proposed relations allow to follow the change of the inclusions and steel composition during calcium treatment when calcium or calcium-silicon are added. An evolution of inclusion and steel compositions during calcium treatment was investigated starting from the partly modified inclusions C_1A_1-SiO_2 with x'_(SiO_2) = 0.10 and 0.03. It was shown that the change of calcium aluminosilicates composition is slightly different for the pure calcium and calcium-silicon additions. With the calcium treatment the mole fraction of SiO_2 in inclusions is decreasing less significant.