Properties of alumina-zirconia-graphite refractories with particle size according to the Andreasen model

Abstract

The alumina-zirconia-graphite (AZG) refractory is one of the most important refractory for AISI 304 stainless steel strip casting especially used as slide gates or nozzles. The AZG refractories were obtained through baking techniques using fused Al2O3, partially stabilized ZrO2 and flake graphite as the starting materials with Al, Si and SiC powders as additives. A particle size distribution was designed by Andreasen model for coarse Al2O3 (250-1000 μm)/medium Al2O3 (61-250 μm)/fine Al2O3 (<61 μm) in which the contents of fine, medium and coarse Al2O3 powders were variables on the basis of constancy of other fine particles in the matrix. At the same particle size, the accumulative mass percent finer increases when the N-value decreases. The highest bulk density (3.3 g/cm3) and the lowest apparent porosity (5.70%) were obtained at N-value of 0.9 with 1000 μm Al2O3 particle. The reheat linear change fraction about 0.4 to 0.8% indicates that these materials have an acceptable volume stability. The number of air exposure cycles of thermal shock resistance decreased gradually from 8 to 6 as N-value increased from 0.6 to 0.9. The erosion fraction tended to decrease with the N-value increasing.