High Alumina Bricks Porperties
1. One of the important working properties of high alumina refractory brick is the structure strength at high temperature. This characteristic is usually evaluated by the deformation temperature of refractoriness. In recent years, its high temperature creep has been measured to reflect its high temperature structure strength. The test results show that the refractoriness under load increased with the increase of Al2O3 content.
2. For the refractory brick with the Al2O3 content below 70%, the refractoriness under load depends on the quantitative proportion of crystal phase and liquid phase, it increase with the increase in the number of mullite. The quantity and properties of the liquid phase have a significant influence on the refractoriness under load. Therefore, the reduction of the impurity content in raw material is in favor of improving the refractoriness under load and high temperature creep properties.
3. For the mullite- corundum refractory brick with the AL2O3 content of 70% ~ 90%, the content of AL2O3 increases, but the improvement of refractoriness under load is not obvious. This is due to the partial softening of the mullite crystals at high temperature and a slight increase in the amount of flux impurities that interact with the mullite crystals. In particular, the composition of Ti02. Fe203 increases slightly with the increase of Al203 content in the raw material, which changes the quantity and properties of the high temperature liquid phase.
4. Owing to the massive increase of Ti02.Fe203 content in glass phase, so the number of glass phase increases and the viscosity decreases. This is the crucial reason of the improvement of effect on refractoriness under load and high temperature creep properties is not obvious. Only when the transition to the refractory brick which is composed almost entirely of corundum firebrick, that is to say, when the Al2O3 content is more than 95%, high strength at high temperature is obviously improved.
5. The thermal shock resistance of the high alumina refractory brick is worse than that of the clay brick, which is closely related to the mineral composition in the refractory brick. The high alumina brick, such as I, II grade is worse than the III grade high alumina brick. In production, the thermal shock resistance of refractory bricks is often improved by improving the particle structure characteristics of firebricks or adding a certain amount of synthetic cordierite (2Mg0.2AI203.5Si0z) and other minerals in the batching
6. The slag resistance of high alumina brick increases with the increase of Al2O3 content, but its corrosion resistance to alkaline slag is worse than that of alkaline refractory. The reduction of impurities content is favor of improvement of slag resistance. Meanwhile, the improvement of refractory brick density, the reduction of porosity, they are the effective measure to improve the slag resistance.
7. The high aluminum brick has higher thermal conductivity than the clay brick, which is related to the decrease of glass phase in the high alumina brick and the increase of mullite crystal or corundum crystal.
