Properties of castables

The binding agent of mullite with refractory castables is a composite binding agent, which mainly includes α-Al2O3 and SiO2 fine powders, soft soil and hydrated alumina. It is a fine powder and hydrated alumina that are bonded at low temperature. At medium and high temperature, Al2O3 reacts with SiO2 to form mullite to form a combination, so it is called the combination of mullite and refractory castables. It is well known that the use of secondary mullite in amorphous refractories to improve their properties is a commonly used technical means. Refractories, clay compositions and micro-expansion refractory castables are all manufactured using the self-reactive, self-sintering and self-expanding concepts of Al2O3 and SiO2, so they can be used in industrial furnaces below 1400 ° C for good results.

Corundum and silicon carbide are high-purity refractory raw materials used to prepare high-performance refractory castables. When aluminate cement is used as a binder, harmful impurities are introduced and its properties are reduced. At present, corundum and silicon carbide refractory castables are generally prepared with composite binders, that is, mullite is used in combination with corundum and silicon carbide refractory castables, and its properties are shown in Table 1. No. 1 and No. 2 use corundum containing Al2O3. 98% is refractory aggregate, the particle size is 8~ 1mm, and the dosage is 550. SiC > 98% silicon carbide is fine aggregate, the particle size is 2~ 1mm, and the dosage is 100. The powder is synthetic mullite powder, α-Al2O3 and SiO2 fine powder, the dosage number 1 is 15%, 14% and 6%, the number 2 is 10%, 17.5% and 7.5%, and the number 3 is SiO2 > 97% Silicon carbide is used as refractory aggregate, and the dosage is 65%. Silicon carbide with SiC > 99% is used as refractory powder, and the dosage is 10%. SiO2 ultrafine powder with β-Al2O3, α-Al2O3 and SiO2 content of 91% is used as binder and powder, and the dosage is 25%. The mass ratio of refractory aggregate to refractory powder is 65:35. It should be noted that in the design of the mixing ratio, the material in the matrix forms a mullite high temperature bonding phase, and good machinability, microstructure and thermal shock resistance can be obtained.