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, W_s 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], α_A1 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 k_m^∝U^1.5, 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.