CaO-Al2O3-FetO-MgO-SiO2 슬래그로의 Al2O3 용해 거동과 용해 속도 해석

Abstract

The demand for clean steels is increasing due to product and process developments. In a secondary refining process (RH process), FetO component in the molten slag plays important roles on the clean of the steel through alumina inclusion removal, because the steel can be polluted by the FetO through re-oxidation. At the same time, the Al2O3 inclusion can be removed into the molten slag by FetO concentration control, which affects the inclusion absorption into molten slag. For this reason, it is important to optimize the FetO concentration to derive an optimum slag condition. A series of experiments were carried out in order to identify the effect of FetO and C/A (CaO/Al2O3 ratio) in the molten slag on the dissolution rate of alumina. The dissolution behavior of alumina was observed by the reaction between an alumina crucible and the molten slag. After the experiments, obtained samples were analyzed by applying the dissolution rate equation. And in some runs, alumina crucibles were collected after each experiment and the interface between the crucible and the slag was analyzed by SEM-EDS to inspect the formation of inhibition layer such as spinel (MgAl2O4) or CA2 (CaO·2Al2O3). The results showed that the dissolution rate increased as FetO and C/A increased. FetO in the molten slag significantly reduced the viscosity of the slag and facilitated mass transfer of Al2O3. Likewise, the C/A not only lowered viscosity of the slag but also increased concentrational driving force to increase the dissolution rate. It was possible to utilize the present results in the prediction of a dissolution time of the actual inclusion into the FetO-containing slag by applying the modified invariant interface approximation. By applying the modified invariant interface approximation, it is now possible to estimate the dissolution time of alumina inclusion into the FetO containing slag for which a conventional Confocal Scanning Laser Microscope (CSLM) experiment cannot be carried out.