1996 Volume 36 Issue Suppl Pages S109-S112
The conditions of formation of inclusions in steel during ladle refining in MgO-C lined ladles were investigated. From the experimental results as well those of a thermodynamic study conducted in parallel, the following conclusions can be made about the reaction mechanism between the MgO-C refractory and aluminum deoxidised 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 aluminum dissolved 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 shown to consist mainly of MgO, Al2O3 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 magnesium from the crucible to the molten steel.
- thermodynamic calculations indicate that during vacuum refining, as the pressure decreases, the chemical compatibility of carbon-bonded magnesia for ladle lining decreases.
