減圧下CaO-CaF-AlOフラックス粉体上吹き時の窒素濃度変化に対する硫黄濃度および酸素濃度変化の影響 (鉄と鋼)

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To examine the change of the rate of nitrogen desorption with sulfur concentration and low oxygen concentration change, the rates of nitrogen desorption from molten steel were measured with 60mass%CaO-40mass%CaF2 flux powder or 35mass%CaO-50mass%CaF2-15mass%Al2O3 flux powder blowing onto 1500kg heats of molten steel through a top lance under the reduced pressure by using the high frequency induction furnace. Temperature of molten steel (<0.001%C, 0.5%Mn, 0.2%Si, 0.04-1.0%Al, 0.0011-0.0071%S) was held at 1873K.Whereas concentrations of sulfur and nitrogen were decreased by the flux powder blowing, concentration of calcium was increased. The apparent rate constant of desulfurization was increased with increasing aluminum concentration regardless of flux composition. However the rate constant of nitrogen desorption was depended on activity of surface activity elements and flux composition. It was estimated that the increase of rate constant was caused by decrease of oxygen activity in molten steel that was determined by reaction between Al2O3 in flux and aluminum in molten steel.