Performance characteristics of corundum mullite castable: it has the common advantages of corundum castable and Mullite castable;High strength at high temperature, good thermal impact resistance and structural spalling resistance;Good thermal shock resistance, high softening temperature under load, low creep rate at high temperature, good chemical corrosion resistance.Can be used for anti-wear lining of large power station boiler and other high temperature kiln lining.
(1) Matrix composition.The matrix composition has important influence on the service temperature, high temperature mechanical property and sintering property of castable.The matrix should be mainly bauxite clinker with low K2O and Na2O content, the amount of cement added should be controlled, the ingredients should be optimized, and the matrix of castable should be similar to mullite (A3S2) chemical composition.In other words, the content of Al2O3 and SiO2 in the matrix is adjusted to generate mullite at high temperature and generate volume expansion, so as to improve thermal shock resistance and high-temperature strength.
(2) Binder.Pure calcium aluminate cement was chosen as the binder.Its main component is CaO·Al2O3(calcium aluminate decomposition temperature 1600℃, high activity, normal setting speed, fast hardening speed, high early strength, late strength increase is not obvious;CaO·2Al2O3(calcium dialuminate, decomposition temperature 1762℃) has slow hydration and hardening speed, low early strength and high late strength.Through the hydration condensation of the cement, the aggregate and powder are cemented together, and it is advisable to add less than 5%.
(3) Add an appropriate amount of powder.The addition of micro powder can fill the intergranular space, improve the internal structure, and produce condensing and binding effect to densify it.At the same time can significantly improve the liquidity, greatly reduce the construction water consumption.At 110℃ and 24h, the addition amount is more than 8%, the shrinkage of castable increases, more cracks, 4%~5% is appropriate, the physical properties of castable with different micro powder content.
(4) High temperature enhancer.Corundum is characterized by high melting point, stable chemical properties and good high-temperature strength, etc. Therefore, it is advisable to use powder less than 0.088mm with a dosage less than 15%.