Characterization of MgO-C bricks with different fused magnesia aggregates

Abstract

The influence of fused magnesia (FM) on the corrosion resistance, mechanical behavior and thermal evolution of MgO-C bricks was studied. Three qualities of electrofused magnesia were used as main raw material to form three bricks identified as A (purity 97.6 wt%), B (purity 98.2 wt%) and C (purity 98.7 wt%). Si and Al were used as antioxidants and phenolic resin was chosen as binder. Chemical resistance was evaluated through a cup test at 1600°C (2 h) using a steelmaking slag from LD converter. The mechanical evaluation was performed through compression tests at room temperature (air) and at 1400°C (argon). From the stress-strain curves different mechanical parameters were determined. Dilatometries up to 1400°C (in Ar) were performed to evaluate the thermal evolution. Microstructures were observed by optical microscopy and by SEM/EDS. The grain size of magnesia aggregates was determined. Besides, density and porosity of bricks were measured. Brick C presented a higher resistance to slag corrosion due to its highest purity and largest grain size of FM. At 1400°C, brick A presented the highest fracture strain (εF) and fracture energy (UF). Thus, the corrosion resistance increases and the fracture parameters decrease when the purity of FM grains increases.