Fused zirconium corundum bricks are commonly known as white iron bricks or fused zirconium corundum bricks. It is the most important refractory material to ensure the normal operation of glass melting furnaces. At present, the improvement of melting rate, extension of kiln life and reduction of fuel consumption in glass melting furnaces at home and abroad are mainly achieved by using this refractory material.
Fused zirconium corundum bricks can also be called corundum-badgeolith products. Its main chemical composition is Al2O3 of 50%-70%, ZrO2 of 20%-40%, and the rest is SiO2. The main mineral composition is baddeleyite (ZrO2), corundum (α-Al2O3) and glass phase. Baddeleyite crystallization forms the backbone of the brick body. ZrO2 has a high melting point (2715℃), good chemical stability, and strong ability to resist acidic and alkaline media, especially glass liquid corrosion.
As the content of ZrO2 in fused-cast zirconium corundum brick increases, its performance also improves. Generally, zirconium corundum bricks are divided into several grades according to the amount of ZrO2, such as 33%, 36%, and 41%, and there are also grades of 30%, 40X, and 50%, which are not yet unified. At present, the most commonly used products are those containing 33% zirconium, with a density of 3.65-3.7g/cm3 and a maximum operating temperature of about 1700℃.
Cast zirconium corundum bricks are used in industrial furnaces such as glass melting furnaces. The parts used in glass melting furnaces are the upper pool wall, small furnace arch, small furnace stack, tongue arch and breast wall.
The following issues should be noted during use:
(1) Irregular changes in thermal expansion The expansion curve of cast zirconium corundum bricks has an abnormal section near the surface. The ZrO2 crystals inside it undergo reversible crystal transformation and have a large volume change. Therefore, products containing ZrO2 should not be used in parts where the left and right temperatures often fluctuate sharply. When baking the furnace, the temperature change at 900~ cannot be too large, generally not more than /h, and steady heating is required. Certain parts should be protected from cold wind and need to be protected with other bricks to prevent cracking.
(2) Shrinkage holes often appear at the casting mouth during casting. The brick body here has many pores and poor density. Therefore, when laying the wall of the glass melting part, the shrinkage holes are all facing the kiln. If the casting mouth faces outward, when the brick body is eroded to a very thin layer, it will cause glass leakage accidents. When used in the flame space above the tank kiln, the service life is very long and there will be no glass leakage problem. Therefore, the casting mouth is used outward to extend the service life.
(3) Eutectic fused-cast zirconium corundum bricks and clay refractory bricks will be eutectic at high temperatures. Therefore, when selecting refractory materials, avoid contacting two refractory materials with serious eutectic phenomena. For example, silica bricks are under fused-cast zirconium corundum bricks, which are most susceptible to erosion by fused-cast zirconium corundum bricks.
Glass kiln fused-cast zirconium corundum products are divided into three grades according to their zirconium oxide content. AZS-33: The product contains 33% zirconium oxide; AZS-36: The product contains 36% zirconium oxide; AZS-41: The product contains 41% zirconium oxide. The products are divided into two grades: Y (first-class product) and H (qualified product) according to their physical and chemical indicators, dimensional tolerances and appearance indicators.
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