In recent years, fused cast high zirconia block is introduced to decrease the number of glass defects and increase the corrosion resistance of refractories for high quality glasses and special glasses, due to its excellent corrosion resistance and no pollution to glass.
Fused cast high zirconia block is developed to operate in extreme condition and also require control of the making process. It is made of artificial synthesis high purity raw materials through special casting process.
The high zirconia fused cast refractory has a structure in which grain boundaries of relatively coarse baddeleyite crystals are filled with a matrix glass mainly composed of SiO2, Al2O3 and ZrO2 and contains a small amount of Na2O and/or K2O.
ZrO2 adopts a monoclinic crystal structure at room temperature and transitions to tetragonal and cubic at higher temperatures. The larger the content of the ZrO2 component in the refractory, the higher the corrosion resistance against molten glass.
However, when the content of ZrO2 is too much, it becomes difficult to obtain a fused cast refractory having no cracks by casting. When the zirconia crystals undergo reversible transformation between monoclinic crystals and tetragonal crystals, a rapid volume change will happen at a temperature from 1,000℃ to 1,150℃. As a result, fused cast high zirconia block is more difficult than fused cast AZS, as the volume expansion rate may cause cracks and a spalling phenomenon. The stress caused by the volume change can be absorbed by glass phase. So the SiO2 component is an essential component to avoid cracking.
The Al2O3 component plays an important role in adjusting the relation between the temperature and the viscosity of the matrix glass and provides an effect of reducing the concentration of the ZrO2 component dissolved in the matrix glass. By utilizing this effect of the Al2O3 component, it is possible to prevent precipitation of zircon in the matrix glass and to prevent the change in quality of the matrix glass, whereby it is possible to avoid the chipping off phenomenon of the refractory and cracking due to an accumulation of remaining volume increase.
Na2O and/or K2O provides a function of softening glass. They are important components which influence the viscosity of the matrix glass and also have an effect of controlling the concentration of the ZrO2 component to some extent.
Fused cast high zirconia block has wide application in a wide range of super high temperature furnaces and kilns in military industry,science research, high melting point Metallurgical, laser crystal and electronic,etc. Sunrise Refractory offers fused cast high zirconia block TY-Z88-WS and TY-Z95-WS, and are used in sidewall, throat cover, throat support, electrode block, dam block parts.