Research Of Zirconia's Metering Nozzle

Zirconia's metering nozzle has been widely applied in small square billets of tundish, and the performance of metering nozzle directly impact on time of continues casting. It is very important for the reliable service performance of metering nozzle to achieve high-quality molten steel and more effective process of continues casting. It not only improved service life, but also increased effetely production coefficient. In a short, it is very important for metering nozzle to hold higher abrasion resistance, erosion-resisting characteristics and better performance of thermal shock resistance, which not occurr any problems during being used, such as plugging, splitting, expanded diameter, and so on.At present, calcium or magnesia as a stabilizer is widespread added into high-purity zirconium to product metering nozzle all over the world, and in general zirconia's content is about 95%. However, it is not remarkable for the former to resistance abrasion and erosion performance of molten steel, and the latter is prone to be produced the precipitated phenomenon used under high temperature long period. The product properties had been improved by using fused magnesium partial-stabilized zirconia (PMD), fused calcium partial-stabilized zirconia (PCD) and baddeleyite as raw materials, adding a certain of additives and agents, rationally choosing grain composition, optimizing craft parameter and adjusting zirconia's stabilization rate of specimen in the research. The results showed the fine shaping of specimen came true with greater bulk density, smaller apparent porosity and no any cracks when molding pressures reached to 300MPa around. The greater bulk density and lower apparent porosity have been gotten when proportion of grain composition among coarse, medium and fine particles was 40:10:50. Better general performance of specimen has been achieved adopted by agents II combined. Y₂O₃ additives can promote sintering character, and help to increase bulk density and decrease apparent porosity rate of specimen. In contrary, CeO₂ additives can significantly improve thermal shockresistance of specimen. When the contents of Y2O3 and CeO2 additives are 0.6% and 0.4% respectively, the product has been gained which characterized by apparent porosity lower, bulk density over 4.8g-cm³ and thermal shock resistance over 5 times. The performance of thermal shock resistance reached top with about 70% stabilization rate of zirconia and containing a certain of micro-crystallite of m-ZrO2.