EFFECT OF STIRRING AND SLAG CONDITION ON REOXIDATION ON MOLTEN STEEL

The kinetics of reoxidation mechanism with slag in Al killed steel wer e investigated in laboratory experiments at 1873K in MgO crucibles wit h 10kg steel. The CaO-SiO2-Al2O3-FeO-MnO slags were used to study the effect oi (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],rr,, inc reased with increase of (FeO+MnO) and Ws. Mass transfer coefficients i n metal, slag and reaction rate coefficient for reduction of SiO2 were estimated to be 2.5 x 10(-6)-6.0 x 10(-6) (m/s), 1.0 x 10(-5) -2.5 x 10(-5)(m/s) and 3.2 x 10(-3) (kg/m(2.)s), respectively. Mass transfer coefficients in metal, k(m) obtained by parameter fitting method under the various conditions of Q showed k(m)infinity U-1.5, where U is mea n surface velocity calculated using two dimensional flow analysis. Thi s relationship was also obtained from turbulent flow model under the a ssumption that friction velocity has linearity with surface velocity. Calculated [sol.Al] in 250t ladle showed a good agreement with observe d one during killing before casting. Calculated results showed that [s ol.Ai] in the ladle rapidly decreased in the last period during castin g because slag volume ratio to molten steel increased during casting.