Dynamic evolution of non-metallic inclusions in a molten high-carbon Al-killed steel reacting with different magnesia-based refractories under eccentric rotation

Abstract

Dynamic interactions between high-carbon Al-killed steel and two types of industrial refractories (MgO and MgO-C) were investigated using laboratory experiments, thermodynamic, and kinetic calculations at 1873 K. After 90 min of contact, no liquid steel penetrated the MgO refractory, while some liquid steel infiltrated the MgO-C refractory reaching an invasion depth of 1 mm, primarily through the grain boundaries, due to the graphite dissolution. The cathodoluminescence optical microscope can analyse and differentiate particles in the refractory based on their distinct luminescent colours. For the MgO refractory, an approximately 5 μm thick interfacial layer, composed of Al₂O₃-MgO and CaO-SiO₂-MgO, was observed at the interface. This layer formed due to the reaction between [Al] and [O] in the steel and the exposed SiO₂-CaO-MgO and MgO at the refractory boundary, while the composition of the inclusions composition in the steel remained largely unchanged. For the MgO-C refractory, an approximately 15 μm thick interfacial layer, composed of CaS-MgO-Al₂O₃-CaO and some MgO particles, was observed between the steel and the refractory. The average MgO content in the inclusions increased from 5.05 wt.% to 100 wt.%, while the Al₂O₃ content exhibited the opposite trend. This was primarily due to the dissolution of Mg(g) generated by the reduction reaction between C and MgO in the MgO-C refractory. The experimental results agreed well with the thermodynamic and kinetic calculation results.