Effects Of Stabilizers On The Mineral Composition And Properties Of ZrO₂ Sizing Nozzle Matrix

Sizing nozzle is very critical in the refractories used in the iron and steel industry of billet continuous casting process,it impacts on the quality of steel casting and production efficiency directly,therefore,the quality and the length of life of sizing nozzle is very important,and the key factors affecting the quality and life of sizing nozzle is the raw material selection,production preparation and microstructure control.Preparation of sizing nozzle in the production process,zirconia is the most commonly used materials because of its excellent properties such as high temperature,corrosion and chemical stability.Currently,in the production of the preparation of sizing nozzle,the particle part of the formulation is mainly partially stabilized zirconia,and the matrix part usually use the monoclinic zirconia added stabilizer and then formed partially stabilized zirconia by sintering.This topic research the effect of the type and quantity of stabilizers added on the phase composition,performance and microstructure of sizing nozzle matrix.Previous group measured physical properties,phase composition and microstructure of zirconia samples which used MgO and MgO+Y₂O₃ as stabilizer by adding them to the monoclinic zirconia powder formed partially stabilized zirconia after sintering and found that the zirconia samples stabilized with composite stabilizer performance better than the samples with only one stabilizer,and the particle size of zirconia was uniform,tight binding between the particles.The topic first studied the properties,phase composition and microstructure of the zirconia samples after sintering by adding cerium oxide as a stabilizer to the monoclinic zirconia powder,and analyzed the effect of different amounts of cerium oxide on the properties of samples.Then four different stabilizer（MgO,Y₂O₃,CeO₂,TiO₂）composite stabilized zirconia with orthogonal test table,the differences of the phase composition,microstructure and properties of ZrO₂ samples of 9 groups in the orthogonal experiment were studied and the effect of the stabilizer on the stability of zirconia,and the extent of the influence on the compressive strength and thermal shock resistance of samples were analyzed using range analysis,then combined with the results of orthogonal experiment to determine the best composite stabilization program.This study can be concluded from the following five aspects:（1）All the sample mixed stabilizers after sintered at 1710℃ generated the cubic phase,and the content of monoclinic phase decreased significantly,and the content of the variation of cubic and monoclinic phasewas different because of the difference of the kinds and content of the stabilizer in raw materials.（2）When ceria stabled zirconia alone,the increase of the cubic phase and stabilization degree of the sample with 13%ceria was the highest.（3）When co-stabilizing,for the samples with 30%（in volume fraction）cubic phase,the values of compressive strength and times of thermal shock resistance were 1 times and 41 times respectively higher than the samples with too much or too little cubic phase,and the ZrO₂ particle was columnar structure which show a interlaced distribution.（4）When compound stabilizing the monoclinic zirconium,the greatest factor influenced the degree of stability and compressive strength of the samples was the content of CeO₂,and the greatest factor influenced the thermal shock resistance was the content of MgO by the range analysis.（5）In order to achieve high compressive strength and thermal shock resistance,the optimum feed ratio of stabilizer should be 3.0%（in mass fraction）CeO₂,3.0% MgO,0Y₂O₃,5.0%TiO₂.