Mullite bricks refers to a high alumina refractory material with mullite as the main crystal phase. Generally, the alumina content is between 65% and 75%. In addition to mullite, the mineral composition contains a small amount of vitreous phase and cristobalite with a lower alumina content, and a small amount of corundum with a higher alumina content. Mullite bricks have high refractoriness, which can reach above 1790℃. The starting temperature of softening under load is 1600~1700℃. The compressive strength at room temperature is 70~260MPa. Good thermal shock resistance. There are two types of sintered mullite bricks and fused mullite bricks. Sintered mullite

The brick is made of high alumina bauxite clinker as the main raw material, adding a small amount of clay or raw soil as a binder, and is made by molding and firing. Fused mullite bricks are made of high bauxite, industrial alumina and refractory clay, adding charcoal or coke fine particles as reducing agents, and are produced by reduction electrofusion method after molding. The crystallinity of fused mullite is larger than that of sintered mullite, and its thermal shock resistance is better than that of sintered products. Their high temperature performance is mainly determined by the alumina content and the homogeneity of the mullite phase and glass distribution.

How are mullite bricks made?

There are three methods of producing lightweight mullite bricks: foam method, additive burning method and gasification method.

The production of lightweight mullite bricks by the foam method is to mix the foaming agent, stabilizer and water in a certain proportion, first make a foam liquid, and then mix with the slurry to cast molding, curing, drying, baking and firing, etc. process to make light mullite bricks with high porosity. Although it can produce high-quality light-weight mullite bricks, it has many procedures, complex procedures, long production cycle, low production efficiency and high cost.

Additive burning method to produce light mullite brick is to add some combustible additives, such as sawdust, polystyrene, coke, etc. stomata. Such bricks with high porosity and low density become lightweight mullite bricks. The method has the advantages of simple production process, short production cycle, low cost and high production efficiency.

The production of light inlite bricks by gasification method refers to the introduction of substances that can chemically generate gas into the ingredients, and the use of chemical methods to obtain air bubbles, thereby producing bricks with high yield and low density. Compared with the foam method, the production process of this method is simpler, the production cycle is longer, the cost is higher, and it is rarely used in actual production.

According to the actual situation, some special refractory factories may consider using the additive burning method to produce lightweight mullite bricks. There are three molding methods for the production of lightweight mullite bricks by the additive burning method: vibration, pouring, and manual ramming. Vibration molding produces lightweight mullite bricks, with short cycle and high production efficiency, but it is difficult to control quality (concerned about density); casting molding cycle is long, production efficiency is low, and cost (mold cost) is high; manual ramming molding The production efficiency is low, the cost is low, the labor intensity is high, and the quality is difficult to control.