Effect of Stirring and Slag Condition on Reoxidation on Molten Steel

The kinetics of reoxidation mechanism with slag in Al killed steel were investigated in laboratory experiments at 1873K in MgO crucibles with 10kg steel. The CaO-SiO2-Al2O3-FeO-MnO slags were used to study the effect of (FeO+MnO), slag volume, Ws and stirring gas flow rate, Q on [sol.Al] reoxidation rate. Experimental results were evaluated by a coupled reaction model.Apparent rate constants of [sol.Al], αA1 increased with increase of (FeO+MnO) and Ws. Mass transfer coefficients in metal, slag and reaction rate coefficient for reduction of SiO2 were estimated to be 2.5×10-6-6.0×10-6(m/s), 1.0×10-5-2.5×10-5 (m/s) and 3.2×10-3 (kg/m2·s), respectively.Mass transfer coefficients in metal, km obtained by parameter fitting method under the various conditions of Q showed km∝U1.5, where U is mean surface velocity calculated using two dimensional flow analysis. This relationship was also obtained from turbulent flow model under the assumption that friction velocity has linearity with surface velocity.Calculated [sol.Al] in 250t ladle showed a good agreement with observed one during killing before casting. Calculated results showed that [sol.Al] in the ladle rapidly decreased in the last period during casting because slag volume ratio to molten steel increased during casting.