Fused zirconium corundum brick (AZS) are mostly used in the highest temperature part of the kiln and the most seriously eroded part by the glass liquid.

The main composition of fused zirconium corundum brick

Different brick types are usually marked by the amount of ZrO2 contained. The brick is mainly composed of two crystal phases and glass phase of α-corundum and baddeleyite. Except for the eutectic with α-corundum, the baddeleyite zircon is free. The more ZrO2 contained in the brick, the more free baddeleyite. The corrosion resistance of these two crystal phases is very good, and the two crystal phases are closely combined, and the structure is uniform and dense, so the corrosion resistance is stronger. Due to the introduction of a small amount of Na2O into the brick, the mullite crystallization area is reduced, and the mullite crystal phase is difficult to precipitate, and the glass phase is formed to fill the above crystal phases. This glass phase is eroded by high temperature glass liquid to form albite glass with higher viscosity, which is more viscous due to a certain amount of ZrO2 dissolved in it. This layer of high-viscosity glass stays on the surface of the brick and is not easy to spread, thus protecting the brick body. If the brick body has coarse crystals, it is not easy to form a high viscosity layer after being eroded, and the glass liquid will easily penetrate into the brick body and erode the brick body faster.

Alteration process of zirconium corundum brick

The alteration process of fused zirconium corundum brick, first of all, the molten glass bricks interact with the glass phase originally existing in the bricks, and gradually diffuse and dissolve. After that, the α-corundum and monoclinic zircon in the brick slowly dissolve in turn. The viscosity of the glass liquid near the surface of the brick body increases, forming a protective layer against erosion. At the same time, the metasomatism reaction will produce α-corundum, nepheline, skeleton-like baddeleyite and so on.

Usually, for the bricks near the liquid level on the upper part of the pool wall, the glass liquid in the metamorphic layer has obviously penetrated into the brick body, but the eutectic of corundum and baddeleyite zircon is still connected by the remaining glass phase. The surface of the brick at the lower part of the pool wall is α-corundum, baddeleyite zircon residue and turbid glass phase. Due to the reaction between the glass phase in the brick and the glass liquid, a nepheline liquid phase is formed, which dissolves a part of the zircon and forms a nepheline liquid phase. High viscosity metamorphic layer.

When the temperature is lowered, the dissolved ZrO2 will precipitate out star-shaped or dendrite crystals, which is the secondary crystallization of baddeleyite. In the high-viscosity layer at the lower part of the pool wall, the secondary crystals of baddeleyite zircon and nepheline crystals coexist. With the prolongation of use time, these two crystalline phases may be taken away by the glass liquid flow, and then further diffuse into the glass liquid. The harder-to-melt baddeleyite may partially dissolve and remain in the glass liquid as stones appear in the finished product.

Fused zirconium corundum brick is now produced by the oxidation method, which can improve their performance and prevent the occurrence of the above-mentioned defects.