Corrosion of Refractories by Soda-based Slag for Hot Metal Treatment

Abstract

The corrosion of refractories by molten soda-based slag was studied by rotating cylindrical polycrystalline specimens (φ20×35 mm) in a stationary crucible containing the slag melt prepared with mixture of Na₂CO₃ and SiO₂ at 1 400°C.
Alumina, spinel, and magnesia specimens had good corrosion resistances as compared with other specimens, especially alumina was independent of the composition of melts, while magnesia was affected by that. Zircon, mullite, carbon and silicon carbide specimens were extremely corroded for slags more than Na₂CO₃/SiO₂ mol ratio 2.
The quantity of dissolution of alumina specimen estimated from the decrease in its diameter was dependent on both the dipped time and the speed of rotation of specimen in the slag of mol ratio 3. It was also remarkably accelerated as the temperature of slag increased. Activation energy for the dissolution was estimated to be about 28 kcal/mol. Its corrosion in ternary slag decreased with increase in P₂O₅ content of Na₂CO₃-SiO₂-P₂O₅ melts. Therefore, it is shown that the process of corrosion of alumina specimen in soda-based slag within the range of this experiment is controlled by the diffusion of reaction product in the liquid boundary layer.