2021 年 107 巻 10 号 p. 785-795
A series of Al deoxidation mechanisms from the nucleation and growth of Al2O3 nuclei immediately after the addition of Al to the growth, agglomeration, and removal of Al2O3 inclusions after the deoxidation equilibrium has been analyzed in light of the kinetics taking into consideration the influences of the interfacial properties on the basis of Al deoxidation experiments of molten steel. The nucleation number density of Al2O3 is (0.72 to 1.62) × 1014 m−3 and increases as the degree of supersaturation increases and the interfacial tension between the nuclei and molten steel decreases. These tendencies can be explained by the homogeneous nucleation theory, and the average interfacial tension, frequency factor, nucleation time, and average nucleation rate are respectively estimated to be 1.43 N·m−1, 4.27 × 1035 m−3·s−1, 0.01 s, and 1.96 × 1016 m−3·s−1 for the nucleation of Al2O3. Al2O3 nuclei rapidly grow to Al2O3 single inclusions having diameters of 2.0 to 2.6 µm through diffusion growth of supersaturated O in molten steel within 2.2 to 3.7 s after the addition of Al, and the molten steel reaches the deoxidation equilibrium. In the subsequent deoxidation equilibrium, the growth rate of Al2O3 single inclusions increases as the O concentration in molten steel increases, and their growth mechanism can be explained by Ostwald ripening. Meanwhile, Al2O3 cluster inclusions grow with the increase in the agglomeration force while agglomerating not only with single inclusions dispersed in molten steel but also with other cluster inclusions existing in the floating paths.
