Effects of particle distribution of matrix on microstructure and slag resistance of lightweight Al2O3–MgO castables

Abstract

For lightweight castables containing microporous aggregates, the compacted matrix component is a key factor in determining their useable lifespan, and this matrix is influenced by both the particle packing and sintering process. In this study, the grain grading of lightweight Al2O3–MgO castable matrices was adjusted to create a particle size distribution that close to the Andreassen model with q-values of 0.25, 0.28, 0.31, and 0.34. After sintering at 1500°C for 3h, the microstructures and slag resistances of lightweight Al2O3–MgO castables with different particle packing arrangements were compared and discussed. The results show that a q-value no higher than 0.31 was needed to ensure formation of a denser matrix. For the smallest q-value that was studied (0.25), the resulting matrix had a large grain size (5–12µm) and a relatively small average pore size (D50=2.10µm), which favours the formation of Ca (Al, Fe, Mn)12O19 layer distributed within the matrix. This resulted in the highest resistance to slag corrosion observed (Ic=7.93%), whereas the cracks existing between the matrix and the aggregates due to a large volume shrinkage decreased the slag penetration resistance (Ip=45.9%). The microstructure of the matrix with a q-value of 0.28 was uniform and compacted, which reached an acceptable compromise between resistance to slag corrosion (Ic=22.4%) and resistance to slag penetration (Ip=11.5%).