At present, there are mainly two types of corundum on the market: sintered and fused. Fused corundum mainly includes fused white aluminum oxide, fused pink aluminum oxide, fused dense corundum, etc. However, the varieties of sintered fused alumina are relatively simpler than those of fused corundum. With the increase in electricity prices, the production cost of fused corundum will increase, and the sintered fused alumina market will be further expanded. Therefore, the research and development of various sintered fused alumina has become one of the current research hotspots. The following are several sintered fused alumina and their uses.
1. Lightweight sintered fused alumina is a porous refractory material with a core-shell structure made from transition phase alumina using foaming technology. The pores of this porous corundum are mostly closed pores, and its density can be controlled by controlling the amount of foaming agent added. Lightweight sintered corundum is mainly used in ladle castables, and its closed pores can significantly reduce thermal conductivity and improve thermal shock resistance.
2. Microporous sintered fused alumina is a refractory material with lower bulk density than ordinary tabular alumina. It has more intracrystalline and intercrystalline pores, and the pore size is maintained at the micron level, but its chemical composition is the same as that of sintered tabular alumina. The pores of microporous sintered corundum make it have the characteristics of low bulk density, low thermal conductivity and high strength. Based on this property, it can partially replace sintered tabular alumina and be used in the ladle to reduce heat loss.
3. Dense sintered fused alumina is a new type of high-density sintered corundum. Compared with ordinary sintered tabular alumina, the volume density of dense sintered corundum is >3.65g/cm3, and the apparent porosity is <3.0%, which is a significant improvement compared with the original standard value. It will effectively improve the performance of sintered corundum and extend its service life. The higher density gives it better wear resistance and erosion resistance. For refractory products with harsh use conditions, such as skateboards, three large pieces, air-permeable bricks, and ladle impact zone castables, which have high requirements for erosion resistance, the use of dense sintered corundum can greatly improve their service life and safety factor.
4. Sintered titanium corundum is a special corundum prepared by introducing TiO2 into alumina and calcining at high temperature. Since the lattice constants of Al2O3 and TiO2 are close, Ti4+ and Al3+ will undergo limited substitution, causing lattice distortion, activating the lattice, significantly improving sintering activity, and reducing its sintering temperature. Sintered titanium corundum has high mechanical strength and good anti-ballistic performance. It can be used together with β-corundum in the molten pool of the glass kiln to improve toughness under high temperature conditions.
Therefore, it has become the current development trend to study different types of sintered fused alumina, give full play to its excellent properties, reduce its sintering temperature, improve its post-sintering properties, and further increase its application.
