Formulation of MgO-Zirconia Powders for the Production of Metering Nozzles or other Refractory Materials via Improved Granulation Process

摘要

In this paper, we present the results of studies on making MgO-Zirconia sintered parts (intended to be used as metering nozzles in continuous casting of steel) from monoclinic Zirconia and MgO powders via a granulation process. Regarding the powder formulation, special care was taken in the selection of the additives and the raw materials (e.g. chemistry and particle size) in order to optimize the pressing and the sintering behaviour for the realization of large refractory parts. The produced ready-to-press powders show excellent behaviour during the uniaxial pressing stage, thanks to the binding system (PVA-based), the optimization of the particle size distribution and the morphology of the granules. After sintering at temperatures in the range 1,600 to 1,700°C, a homogeneous microstructure could be observed. Depending on the particle size of the monoclinic Zirconia powder used in the blend, it was also possible to produce sintered parts having different porosities. Here, the granulation process offers some cost-saving perspectives compared to traditional spray drying as it requires significantly less water and additives, and necessitates lower energy consumption.