Electrofused zircon corundum brick in the production will produce a variety of defects, resulting in the use of poor quality products. The physical and chemical inhomogeneity of zirconium corundum bricks is often the main reason for the defects of the products. Particles that are not melted through in the batch and gas inclusions that have not been discharged from the melt in time are all physical inhomogeneities. The difference in the composition of the melt along the depth of the furnace is a chemical inhomogeneity.

In fact, the common cause of defects is due to the destruction of the temperature regime. When AZS bricks are hardened in a closed container (if there is no subsequent melt to supplement them), shrinkage cavities will occur due to shrinkage, which is the main defect of electrofused zirconium corundum bricks. The main way to overcome shrinkage in the production of fused zirconium corundum bricks is to add risers to the upper part of the mold to supplement the casting of AZS bricks, while cooling the bottom of the mold to allow the melt to crystallize from bottom to top. In order to ensure the formation of such crystals, it is necessary to maintain a high temperature at the upper level of the AZS brick and a low temperature at the bottom of the mold. With the help of bottom-up heat evolution, uniform directional crystallization is possible, so that dense AZS bricks with low porosity can be obtained. However, to get rid of the AZS brick in the shrinkage cavity, the riser should have the following conditions: there should be sufficient, the temperature is higher than the temperature of the AZS brick melt, the correct choice of the riser and the location of the riser is very important. The above conditions are based on the rich experience of metal casting and the production experience of 33# fused zirconium corundum brick, and the riser in each specific case must be calculated. There are many basic methods for calculating risers, some of which have been proposed under purely experimental conditions and some of which have been derived theoretically. The difficulty of using a large riser is that it is not easy to remove it from a cured AZS brick, and a considerable amount of diamond cutting tool must be used to cut it. Based on experience with metal casting, an easily removable riser has been used in the production of zirconium corundum bricks. That is, a perforated graphite sheet is installed between the riser and the AZS brick. This sheet has "small wings" that are easily broken or cut off after the melt solidifies. The use of such a material to make a sheet of such thickness is intended to avoid difficulties when refilling the paving: pieces through the riser. In addition to shrinkage, cracks and cracks are also defects that form when electrofused zirconium corundum bricks are cast and cooled from the melt. The study of the cracking properties of tested AZS bricks shows that there is a clear relationship between the increase of temperature drop on the cross-section of AZS bricks, the cooling rate and the cracking and cracking. Therefore, it can be determined that the temperature in the range from safety to cracking is reduced to 230°C, and when the temperature is reduced to 180°C, the product can be guaranteed to not produce cracks. The calculation of the temperature field and thermal stress of the AZS brick, the calculation of the heat exchange between the AZS brick and the mold and the diatomite insulation material in the insulation box under different conditions, all prove that the compressive stress generated on the surface of the AZS brick is about 60-200 MPa, which has exceeded the strength index of the AZS brick under any conditions, while the strength index of the AZS brick is 30-160 MPa. The tensile stress generated in the central part of the AZS brick, depending on the cooling conditions, is 5.2-12 MPa, which exceeds the strength index of the AZS brick cast in the graphite mold, but does not exceed the ultimate strength value of the AZS brick when cooled in the sand mold. Therefore, microcracks (cracks) that are not too deep on the surface of the AZS brick will appear in any case, while the melt cast in the graphite mold is extremely likely to produce internal deep cracks.