Zirconia bricks are refractory products produced from zirconia as the main raw material. There are two main manufacturing methods: sintering and casting. There are three crystal forms of zirconia: monoclinic, tetragonal and cubic. When zirconia is heated to about 1100 °C, the crystal transformation will occur, from monoclinic to tetragonal, accompanied by 7% volume shrinkage, and vice versa. Tetragonal zirconia will appear cubic crystal form above 2300 ℃. The densities of the three crystal forms are 5.68 g/cm3 (monoclinic), 6.10 g/cm3 (tetragonal), and 6.27 g/cm3 (cubic).

①Dense zirconia brick

It is formed by isostatic pressing, and its technical indicators are ZrO2>65%, apparent porosity <2.0%, bulk density of about 4.25g/cm3, and corrosion in E glass when the temperature exceeds 1370 °C. It is used in the bottom of the melting part of the E glass unit kiln where the temperature of the molten glass is slightly lower, the bottom of the transition passage, the bottom of the forming passage, the liquid groove of the forming passage and the leakage plate support bricks, etc. In addition, dense zirconium bricks are also used as backing bricks for dense chrome bricks.

The commonly used international brands are ZS-1300, ZS-1500, ZS-835 and ZS-78 produced by CORHART Company in the United States, ZS65WA produced by VGT-DYKO Company in Germany, UC-Z, UC-CZ, UC produced by Shinagawa Co., Ltd. in Japan -CZB et al.

In recent years, my country's refractory enterprises have introduced foreign technology and equipment, and have also produced sintered dense zirconium bricks formed by isostatic pressing, which have been partially used in domestic glass and glass fiber kilns.

The German VGT-DYKO company has developed a new type of dense zirconia brick with coarse-grained structure, which greatly improves the internal structure of the brick, thereby improving the resistance to rapid cooling and rapid heating of the brick. Its bulk density is 3.75g/cm3, and its porosity is 17%. The grade of this brick is ZS65AR, which has good thermal shock resistance, and is most suitable for wire drawing troughs and bushing support bricks.

②Standard zirconium brick

The ZrO2 content of the brick is about 66%, the bulk density is 3.7g/cm3, and it has good thermal stability and peeling resistance. It is used in the breast wall and rear wall of the feeding port area where the powder erosion is more serious, the breast wall and top cover brick and burner brick of the furnace observation hole brick and the passage flame space.