Effects of the Alumina Particle Size and Slag Composition on the Dissolution Behavior of Alumina in Steelmaking Slags

The dissolution behavior of Al 2 O 3 inclusions in steelmaking slag is investigated at 1550 °C using the single hot thermocouple technique. The slag system is based on CaO–SiO 2 –Al 2 O 3 –MgO, with basicity (CaO/SiO 2 ratio) of 0.8, 1.0, and 1.2; Al 2 O 3 contents of 10 and 20 wt%; and initial particle radius set to 9–11, 25–35, and 50–65 μm. In 10 wt% Al 2 O 3 slags, smaller particle radius results in shorter complete dissolution times, and the dissolution behavior appears continuous. Application of the shrinking core model reveals that dissolution of larger particles is controlled by boundary layer diffusion, whereas smaller particles are controlled by surface chemical reaction. When the initial particle radius is ≈10 μm, dissolution is rapid with little dependence on slag composition. For particles larger than 25 μm, complete dissolution time varies significantly with composition. A model is established to describe the relationship between the initial particle radius and complete dissolution time, and the diffusion coefficients derived from this model are found to be within the range reported in previous studies. In 20 wt% Al 2 O 3 slags, smaller particles still dissolve faster. However, spinel formation and slag penetration cause complex, discontinuous dissolution behavior, with dissolution times up to 225 times longer than those in 10 wt% Al 2 O 3 slags.