Study On The Preparation Of Refractories Used For The Submerged Entry Nozzle

With the development of the continuous casting, the submerged entry nozzle which is functional refractories for continuous casting also is quickly developing. In this paper, it introduces function of the submerged entry nozzle and discusses the development of its materials used. Zirconia is a promising high temperature refractory and high temperature insulation because of high melting temperature, good chemical erosion-resistance, oxidation resistance, thermal shock resistance, small specific heat and heat-conductivity etc. In the process of sintering, the additives play a very crucial role. CaO,MgO,Y2O3,CeO2 and other rare earth oxide is usually used for zirconia stabilizing as a stabilizer.Taking ZrOCl2·8H2O, Y(NO3)3·6H2O, Mg(NO3)2·6H2O and ammonia liquor as raw materials, Y2O3-stabilized ZrO2 and MgO-stabilized ZrO2 powders were prepared by chemical precipitation method. Then the ZrO2-C composite was prepared by adding graphite. Based on the thermodynamic analysis and experiments, the thermal stability of ZrO2 in ZrO2-C composite was studied. The effects of amount of stabilizer as well as the solid solution temperature on the stability of ZrO2 in ZrO2-C composite were also investigated. Grain size and lattice constant were calculated. The change of phase compositions caused by pH value was discussioned. Then slag erosion test by static crucible method, measure corrosion depths and penetrated depths of the crucible specimens. The mechanism of corrosion and penetrated were analysed.The experiment indicates that ZrO2 in ZrO2-C composite was unstable when Pco was latm and the temperature was above 1653℃. It related to Pco and the temperature. ZrC was restrained when stabilizers were added into ZrO2.Comparing with MgO stabilizer, Y2O3 stabilizer added into ZrO2 could increase the thermal stability of ZrO2 dramatically. Y2O3 stabilizer added into ZrO2 also has the excellent erosion resistance. In the erosion test, a decarburization layer is formed on the surface between material and steel. The structure of this area is loose, which provides a path for steel erosion and penetration.