Degradation mechanisms of magnesia-carbon refractories in radiation heat-affected wall of steel electric arc furnace

This study investigates the mechanisms underlying microstructural deterioration in processed MgO-C refractories from the radiation heat-affected wall of a steel EAF. X-ray tomography and scanning electron microscopy with energy-dispersive spectroscopy were employed to identify the thermally activated chemical, physical, and mechanical degradation phenomena and to evaluate their impact on microstructural evolution during the process. The results reveal that degradation is primarily driven by the development of a porous network surrounding coarse MgO grains (>∼3 mm), with a strong correlation observed between MgO grain size and damage evolution. Larger grains tend to promote more extensive porous networks, which in turn facilitate oxygen ingress and accelerate carbon oxidation. The pronounced mismatch in thermal expansion coefficients between MgO grains and the carbon matrix contributes to crack formation and grain detachment. These findings provide deeper insight into the failure mechanisms of MgO-C refractories and inform strategies for optimizing refractory design to extend service life and enhance performance.