Effects of Spinel Formation in Al_2O_3-MgO Refractory Castables

摘要

To improve the mechanical and chemical properties of unfired Al_2O_3 refractory castables, MgO was added as an aggregate and/or a matrix powder and the degree of spinel formation was studied. Because the spinel was formed at the contact areas between Al_2O_3 and MgO particles and the volume of in-situ formed spinel was increased abnormally, the kind and amount of added MgO aggregates and matrix powder were studied. And their effects on the physical properties such as the strength and the permanent volume expansion were examined. For Al_2O_3 aggregates, high purity fused Al_2O_3(WFA) was used due to high density and high degree of spinel formation. And corrosion resistance increased with the amount of MgO added, and the finer the MgO powder added, the better the residual expansion and minute structure formation observed. But in the case of a sudden increase of spinel phases, voids would appear around the aggregates, which resulted cracks showing deteriorative effects in the anticorrosion, so the appropriate quantity and grain size of MgO should be controlled for optimal residual expansion considering its spinel formation and enhancement of corrosion resistance due to structural stability.