The present work has as objective to identify and to characterize the responsible mechanisms for the degradation of magnesia-carbon refractory bricks of a metallurgical ladle, due to the attack of the SiO2-CaO-Al2O3-MgO slag. For that, MgO-C refractory bricks used in the slag line were compared with bricks after the use (post mortem). The microstructure of the interfacial region refractory brick/slag was evaluated by mineralogical analyzes (X-rays diffraction), scanning electronic microscopy (SEM) and thin sections for petrography analyses (optic microscopy). It was possible to evidence that the brick post mortem presents, beyond the existing phases already in natura, new phases such as alumina, calcium silicate and gelenite, due to its reaction with the slag. The results suggest that the main way of degradation of the brick was the infiltration of the slag in the matrix and grains boundaries of the refractory brick. This causes to the pulling out of grains, compromising the original microstructure of the refractory material, diminishing its time of useful life.
MgO-C refractory bricks; slag attack; microstructure
