The authors investigated the change in the interfacial tension with time for various combinations of molten slag and liquid Fe to elucidate the mechanism of the change in interfacial tension between liquid Fe alloy and molten slag over time accompanying reduction/oxidation reactions. The behavior of the change in the interfacial tension over time can be explained by the adsorption of oxygen at the interface and the diffusion of oxygen from the interface into the bulk of the liquid Fe and molten slag. In addition to that, we found that the interfacial tension decreases slowly and greatly from its initial value to a minimum point and then increases slowly to the final equilibrium state when molten silicate slag with low viscosity is brought into contact with liquid Fe without Al content and some of its SiO 2 decomposes and dissolves into the liquid Fe. From these results, we suggest that the detachment of oxygen adsorbed at the interface into the liquid Fe is very slow and may be the rate-limiting step.

No abstract

No abstract

The surface tension of liquid Fe-16 mass%Cr alloys and its wettability with alumina substrate at 1823 K were determined as a function of oxygen activity which was less than 0.0070 using the sessile drop technique. Oxygen was found to be strongly surface active in liquid Fe-16 mass%Cr alloys. The variation of surface tension of Fe-16 mass%Cr alloys with oxygen activity can be described by the following equation:

It is well known that the composition of inclusions is determined by alloying elements and by reaction with slag. For example, MgO·Al2O3 spinel-type inclusions form, even though Mg is not added, due to the supply of Mg through the reaction between slag and metal. To clarify the mechanism of compositional changes in inclusions, the authors have developed a kinetic model to simulate the reactions during the ladle refining process. In this study, experiments were conducted using an induction furnace, and the compositional changes in molten steel, slag, and inclusions were investigated. The inclusions were analyzed by P-SEM, which incorporates an automatic analysis system. By the application of the developed simulation model to these experiments, the validity of the model was evaluated. The inclusion composition gradually changed from Al2O3 to MgO·Al2O3 after the addition of Al, and the inclusions originating from slag were also observed at all times. The compositional change of the deoxidation product by the model calculation corresponded well to the observed variation in the composition of inclusions, and the calculated composition of inclusions originating from slag also agreed with the experimental results. The rate of compositional change increased with increasing Ar gas flow rate, and this tendency was captured well by the model. Therefore, the validity of the developed model is considered to be confirmed.