Types, Characteristics, and Applications of Zirconium Corundum Bricks

Zirconium corundum brick refers to a refractory brick containing 30~41% ZrO₂. The main mineral composition is corundum, baddeleyite, and glass phase. Zirconium corundum brick is a white solid formed by melting pure alumina powder and zircon sand containing about 65% zirconium oxide and 34% silica in an electric furnace and then pouring it into the mold for cooling. Its petrographic structure is composed of corundum. It is composed of the eutectoid of zircon plagiolite and the glass phase. From a phase perspective, it is the eutectoid of the corundum phase and the zircon plagiolite phase. The glass phase is filled between their crystals.

1. Types of zirconium corundum bricks

Fused zirconium corundum brick. Also known as fused AZS bricks. It is made of industrial alumina and selected zircon, with a small amount of Na₂CO₃ added for electrofusion. When producing zirconium corundum bricks with high ZrO₂ content, some ZrO₂ needs to be added. Molten zirconium corundum bricks are commonly known as tinplate bricks and also called corundum clinched zircon bricks. These cast materials are produced by arc melting, subsequent casting into molds, and long-term heat treatment. The main chemical components are Al₂O₃ 50%~70%, ZrO₂ 20%~40%, and the rest is SiO₂. The main mineral compositions are baddeleyite (ZrO₂), corundum (α-Al₂O₃), and glass phase. Oblique zircon crystals form the skeleton of the brick. ZrO₂ has a high melting point (2715°C), good chemical stability, and is resistant to acid and alkali media, especially glass liquids.

Sintered zirconium corundum brick. Sintered zirconium corundum bricks are also called ceramic-bonded aluminosilicon zirconium bricks. Compared with fused zirconium corundum bricks, the chemical composition of sintered zirconium corundum bricks is similar. However, it has the advantages of being carbon-free, having low glass phase content, having uniform structure, no shrinkage cavities, and good thermal shock stability, and corrosion resistance. The main raw materials are: industrial alumina is calcined at 1450~1550℃ into α-Al₂O₃, and then ground in a vibration mill until 2 μm particles account for about 50%. It uses a-Al₂O₃, ZrO_2, and zirconium corundum clinker as raw materials, and is processed in a shuttle kiln. It is made by mixing, molding, drying, and high-temperature sintering. Zirconium corundum clinker fine powder. The above three raw materials are batched according to a certain ratio, mixed, high-pressure molded, dried, and fired at 1700~1750°C.

2. Characteristics of zirconium corundum bricks

The main advantages of fused zirconium corundum bricks are their high thermal stability and corrosion resistance, allowing them to withstand extreme conditions in glass tanks for more than 10 years in industrial practice.

Sintered zirconium corundum bricks are highly resistant to erosion by glass liquid. In addition, due to the presence of partially stable tetragonal ZrO₂ (t-ZrO₂), micro-cracks are formed in the bricks with a small amount of porosity, and the thermal shock resistance is stronger than that of AZS fused-cast bricks.

3. Application of zirconium corundum bricks

The fused-cast AZS series refractory bricks for glass kilns have excellent corrosion resistance against molten glass. AZS bricks are used for glass contact surfaces (side walls, floor tiles, etc.) and superstructures (breast walls, ports, tower stones, etc.), and can also be used in other industrial kilns.

Sintered AZS bricks for glass kilns are generally used as the working layer of the glass kiln, in contact with the molten glass, to protect the kiln body and resist the erosion of the molten glass.