Alumina-based materials for the extrusion of filter components for steel casting

A main challenge for materials in steel melt filtration is to provide an open pore structure enabling constant melt flow while simultaneously withstanding the high thermo-mechanical stresses involved in the casting process. In the present study, alumina-based extrusion materials were investigated for the purpose of manufacturing cellular filter structures for continuous casting and filter sample holders for ingot casting. The impact of adding a coarser alumina fraction and/or monoclinic zirconia, and/or carbonaceous material on the structural and mechanical properties of the material was analyzed. The extrusion capability, linear shrinkage, density, porosity, mechanical strength, Weibull modulus and thermal shock resistance were tested in detail. The results showed that coarse alumina-zirconia materials, either carbon-bonded or sintered, delivered the best compromise in terms of these properties. These materials were successfully used to extrude filter sample holders and cellular hollow-ware prototypes.