Mechanism of Reaction between Refractory Materials and Aluminum Deoxidised Molten Steel.

The conditions of formation of inclusions in steel during ladle refining in MgO-C Iined ladles were investigated.Fromthe experimental results as well those of a thermodynamicstudy conducted in parallel.the following conclusions can be madeabout the reaction mechanismbetweenthe MgO-C refractory and aluminumdeoxidised molten steel:-an internal oxidation-reduction occurs in the MgO-C refractory and aluminum deoxidised molten steel during ladle refining, -the formation of a thin oxide layer at the interface is due to the reaction between magnesium vapour and aluminumdissolved into the molten steel and the CO(g) generated by the reaction between MgO and C in the crucible walls; -the oxide inclusions formed in the steel have been shownto consist mainly of MgO.Al.O. or a mixture of them; -some of the finest inclusions are believed to be formed as secondary inclusions during cooling and solidification of the steel, and are connected only with the diffusion of magnesiumfrom the crucible to the molten steel.-thermodynamiccalculations indicate that during vacuum refining, as the pressure decreases, the chemical compatibility of carbon-bonded magnesia for ladle lining decreases.