Precautions for fused zirconium corundum bricks in use

Electrofused zirconium corundum bricks are commonly known as white iron bricks, also known as corundum-oblique zircon bricks. The main chemical composition is Al2O3 50%~70%, ZrO2 20%~40%, and the rest is SiO2. The main mineral composition is oblique zircon (ZrO2), corundum (α-Al2O3) and glass phase. The oblique zircon crystal forms the backbone of the brick. The high melting point of ZrO2 (2715 °C) is good, and it has strong corrosion resistance to acidic and alkaline media, especially glass.

 

The following problems should be noted in the use of fused zirconia corundum bricks:

 

1.Irregular changes in thermal expansion. The expansion curve of fused zirconium corundum brick has an anomaly near 1000 °C, and the internal Zr02 crystal undergoes reversible crystal transformation, which has a large volume change. Therefore, the brick containing ZrO2 should not be used at temperatures around 1000 °C. A region that fluctuates sharply. When baking the kiln, the temperature change should not be too large at 900~1150 °C, generally it should not exceed 15 °C/h, and it is required to heat up smoothly. Some parts should be protected from blowing cold air and protected by other bricks to prevent cracking.

Zirconium corundum brick

2. Shrinkage holes. When casting, there are often shrinkage holes in the casting port. Here, the brick body has more pores and the density is poor. Therefore, when the glass is melted in the wall, the shrinkage holes are directed toward the kiln. If the casting is facing outward, when the brick is eroded to a very thin level, it will cause leakage of the glass. When used in the upper flame space of the kiln, the service life is very long, and there is no problem of running the glass. Therefore, the casting port is used outwards to extend the service life.

 

3.Common melting. The fused zirconia corundum bricks are in contact with the clay bricks. The eutectic phenomenon occurs at 1300 °C. Therefore, when refractory materials are selected, the two refractory materials with severe eutectic phenomena should be avoided, such as silica bricks. Under the fused zirconium corundum brick, it is most susceptible to erosion by fused zirconium corundum bricks.