Research And Application Of Corundum-Mullite Multiphase Ceramic-Slab Of Kiln Utensils

Corundum-mullite multiphase ceramic not only possesses many excellent properties of mullite, such as high melting point, low thermal expansion coefficient, high thermal shock resistance, high creeping resistance, but also has many merits of corundum which takes on high elasticity modulus, strong abrading endurance, high withstanding performance of chemical corrosion and oxidation. At the same time, Corundum and mullite is abundant in raw materials with high price performance ratio. Corundum-mullite multiphase ceramic is deemed to be one of the most widely used high-temperature kiln utensils materials. Corundum-mullite multiphase ceramic-slab used as assistant stuff of parts of an apparatus preparation , has widely development foreground. At present, the researches on corundum-mullite multiphase kiln mainly focus on its macroscopic properties in room temperature. Moreover, the results obtained by various researchers showed great differences, and not very good stability. Although the thermal shock resistance and creeping resistance of samples made in domestic factories are almost as good as foreign samples, the working longevity of domestic products is not as long as foreign ones. So it is necessary to study the factors that influence the performance of corundum-mullite multiphase ceramic and advance the reliability of products.In this paper, the research general situation, development trend and the problems of corundum-mullite in using course were discussed roundly. In allusion to the failure behaving of applying course, this paper was based on the theory of thermal resistance and creeping resistance, and synthetically analyzed their impacting factors that caused invalidation. On this foundation, the raw materials chosen include grains: corundum and mullite, powers: alumina and unformed quarts, coalescent reagent: silicon-aluminum gelation. Making using of the discrepancy of thermal expansion performance, the samples were sintered at 1600℃. The paper studied detailedly from the sides of choosing raw materials, preparation technics, damaging mechanism and microstructure.In the side of raw materials, the raw materials of great granule stuff were madeup of lathy corundum and mullite molten by electricity. The lathy corundum, which had high intensity and coarse surface, could have the function of framework. The mullite molten by electricity had a high purity .Its grains developed well and had lubricity surface that had better be dealed with to make it coarse. The alumina powder and quartzs powder possessed high reactivity activity that conduced to form mullite in high temperature. Moreover, this reaction enhanced the compactness of meshwork. Silicon-aluminum gelation which was prepared as coalescent reagent could reinforce the coalescent between powder and grain .Furthermore, the mullite was engendered on the condition of without other adulterations.The quality ratio of corundum and mullite was kept at 3/1.On the foundation of composing formula of granularity and continual cumuli theory, the cooperation of different sizes of granule and the content of different component was ascertained by orthogonal experiment. Then the prime content of every component was gained. The buck density and porosity quotiety of samples was 2.68g/cm3 ^P 14.97%. In the process of preparation technics, the grains and coalescent reagent were mixed firstly, and then the powder was added in order to let the powder enwrap the surface of grains and have some cushion effect among great grains. On the one hand, this situation could avoid the crash of great grains in the process of moulding, on the other hand, the pore among grains was filled. After 24 hours' placement, the samples were molded in the friction machine and sintered at 1600°C. Its rupture intensity reached 11. 3MPa. Its pressure resistance intensity reached 108. 5MPa.It could promote crystal process and engender upgrowth of granules. In the premise of the satisfaction of intensity, the size of slab needed minishing, so as to reduce the thermal stress because of temperature difference. A piece of slot was opened in the middle of slab for debasing thermal stress.Temperature and stress kept changing at all times in using course, which was a continual circulation process. In room temperature, the rupture process was dominated by crack spreading. The intensity of slab increased with the augment of loading velocity. In high temperature, the process of creeping arosed distortion of slab and gave birth to crack and spreading, which was influenced by the presence of stress. Thethermal shock resistance capacity was evaluated with thermal shock resistance index. The first thermal stress index was apt to evaluate the intensity maintenance quotiety when the samples were cooled in the cold water. When the applying condition was considered, the thermal shock damnification index was apt to evaluate the using longevity. Linked with failure rule, on the one hand, the slab contracted in the direction of paralleling tress because of glass phase after a working time, and expanded in the direction of vertical stress. On the other hand, the grains wrapped by glass and fusing substance slipped. The distortion engendered macro-crack in the direction of vertical stress. When the creeping crack spreading to some extent, with the presence of stress, he crack spreading became intense and joined with each other at last.After observation of the microstructure of corundum-mullite multiphase ceramic, it was found that the grains were surrounded by plenty of powder and combined tight with each other. This indicated that it helped to improve intensity to modified the surface of grains. In room temperature, grains and powder integrated tight. Its rupture process belonged to trans-crystal modality. In high temperature, coalescent intensity became weak, and its rupture process belonged to along-crystal modality.