Chemical action is more complex and severe for the corrosion of fused cast zirconium corundum bricks. The reasons for the serious corrosion of fused zirconium corundum bricks in glass electric melting furnaces can be divided into four aspects:
1. Precipitation of glass phase
The fused zirconium corundum bricks on the pool wall are subjected to the action of high-temperature glass liquid for a long time (>1500℃). On the one hand, the glass phase in the brick will gradually melt and precipitate (the lowest precipitation temperature is about 1150℃); on the other hand, the alkaline glass liquid containing Na2O will invade the brick along the pores and cracks of the brick body, diffuse and penetrate each other with the precipitated glass phase, thereby reducing the viscosity of the precipitated glass liquid and increasing its fluidity, thereby intensifying the corrosion behavior and extending in depth.
2. Damage to the skeleton
As the corrosion of the glass liquid intensifies in depth, the skeleton minerals that constitute fused cast zirconium corundum bricks body are gradually infiltrated and surrounded by the glass liquid containing Na2O, and the skeleton begins to be corroded. First, the dissolved mullite decomposes into α-Al2O3 and SiO2, which in turn promotes the conversion of α-Al2O3 into β-Al2O3. As the temperature rises, β-Al2O3 is completely dissolved in the glass liquid, and the baddeleyite and corundum lattices are also destroyed, and then broken, disintegrated, and partially melted. β-Al2O3 gradually dissolves in the glass at high temperature, and very little is retained. As the glass continues to diffuse and penetrate, the baddeleyite microcrystals become free, part of which is taken away with the glass liquid and may become glass stones, and part of which is retained. Although baddeleyite can be dissolved in glass, its solubility is very small. As the temperature fluctuates, ZrO2 quickly crystallizes from the glass liquid to form skeleton-like or beaded baddeleyite crystals.
3. Crystallization of new minerals
Because the skeleton minerals of the brick body are partially melted in the glass liquid, the composition of the original glass liquid is changed. Therefore, when the ratio of SiO2-Al2O3-Na2O in the glass liquid is close to the theoretical composition of nepheline, a large amount of nepheline crystals will precipitate.
4. Nepheline damage
Since the density of nepheline is less than that of the brick body, the precipitation of nepheline crystals is accompanied by a large volume expansion, making fused cast zirconium corundum bricks body structure loose. Although the melting of part of the crystalline phase in the brick at this time will increase the viscosity of the glass liquid and have a certain bonding and protective effect on the loose structure, it still cannot completely block the airflow, material and glass liquid scouring and gravity in the kiln, and cracks and peels into the glass liquid to form glass stones. The wound surface after peeling continues to be eroded and scour by the glass liquid and continues to peel. The result will inevitably lead to the erosion and disintegration of the fused zirconium corundum brick.
