Effect of Process Parameters on the Properties of Alumina-Zirconia-Graphite Refractories (Part 1) -Forming Pressure and Baking Temperature

Alumina-zirconia-graphite (AZG) refractories were obtained through a baking technique using fused Al2O3, partially stabilized ZrO2 and flake graphite as the starting materials with Al, Si, and SiC powder additives. A particle size distribution was designed by the Furnas model for coarse Al2O3 (500-1000µm), medium Al2O3 (61-125µm), and fine Al2O3 (<44µm), in which the contents of coarse, medium and fine Al2O3 powders were varied with a constant amount of fine particles in the matrix. The bulk density increased from 3.05 to 3.29g/cm³ for the sample with a mass ratio of (coarse Al2O3)/(medium Al2O3)=2.14 as the forming pressure increased from 100 to 150MPa. However, increasing the forming pressure from 150 to 170MPa caused the bulk density to gradually decrease from 3.29 to 3.26g/cm³. The lowest porosity (5.1%) was achieved by compacting the powders with a mass ratio of 2.14 at 150MPa. The average pore size decreased from 5.3-5.8 to 3.1-3.9µm as the forming pressure increased from 100 to 150MPa, and further decreased from 3.1-3.9 to 3.0-3.7µm when increasing the pressure to 170MPa. The bulk density increased with baking temperature, reaching an inflection point at 200°C above which it continued to rise up to 240°C.