Dissolution mechanism of alumina inclusions into CaO–SiO 2 –Al 2 O 3 –Fe t O–MgO slag via a converter tapping process

Abstract

Reducing the amount of inclusions during the steelmaking process as much as possible and much earlier plays a vital role in improving the quality of steel products. To reveal the dissolution mechanism of inclusions in slag during the converter tapping process, some comparison experiments were conducted by adding isolated spherical alumina balls as inclusions in CaO–SiO2–Al2O3–FetO–MgO slag, and FetO content up to 10% was contained in slag. The results showed that the dissolution rate of alumina balls in the slag was mainly affected by the diffusion of Al2O3, and the diffusion coefficients of Al2O3 were 4.2 × 10–11, 7.5 × 10–11, and 1.5 × 10–10 m2/s at 1500℃, 1550℃, and 1600℃, respectively. In addition, the upgraded diffusion-distance-controlled dissolution model (DDD-Model), in which FetO content was introduced and applied in the study. The results illustrated that the Al2O3 inclusion apparent dissolution rate was improved by a high FetO content, increasing CaO/SiO2 and raising the temperature as soon as possible at the early stage of the converter tapping process. It is not necessary to increase the FetO content in the slag to enhance the dissolution rate of the Al2O3 inclusion at the last tapping stage. The predicted complete dissolution time of spherical Al2O3 inclusions with 1000 µm in diameter based on the upgraded DDD-Model was approximately 1796 s during the actual converter tapping process.