Magnesia–carbon refractory dissolution in Al killed low carbon steel

Abstract

The effects of rotation speed, steel temperature and steel composition on the rate of dissolution of MgO–C refractory into Al deoxidised molten steel were investigated using the rotating cylinder method. Cylinders or rods of MgO–C refractory material were immersed in an Al deoxidised molten steel. Experiments were performed for steel temperatures between 1873 and 1973 K and rotation speeds between 100 and 800 rev min⁻¹ as well as for different immersion times. For each case, the dissolution rate of MgO–C material was determined from measurement of the decrease in the rod radius. The experimental results showed that the dissolution rate of the MgO–C refractory material increased with an increase in steel temperature and rotation speed. The findings strongly suggest the diffusion of magnesium through the slag layer formed around the refractory rods to be a rate determining step. This thin oxide layer at the steel/refractory interface was found to be owing to reaction between magnesium vapour and CO generated by the reaction between MgO and C in the refractory. Oxide inclusions were also found in the steel melt and they were shown to mainly consist of MgO and Al₂O₃ or a mixture of the two.