Sintered zircon refractory bricks include zircon corundum bricks, sintered zircon bricks, and sintered zircon mullite bricks.

Sintered zircon corundum bricks

Sintered zircon corundum bricks use zircon and alumina as raw materials, and the ZrO2 content is generally below 20%. Zircon and alumina undergo the following solid phase reaction at 1400-1450℃: 3Al2O3+2ZrSiO4→3Al2O3·2SiO2+2ZrO2, realizing a two-phase uniformly distributed microstructure composed of mullite and baddeleyite (including some t-ZrO2). This irreversible reaction is also called in-situ reaction.

The microstructural characteristics of sintered zircon corundum bricks are that fine (less than 10um) baddeleyite particles are uniformly dispersed between the main crystal phases of mullite and corundum, forming a dense crystalline network with little glass phase. It has a certain amount of pores (porosity less than 20%), but there is no liquid phase seepage. Compared with fused zirconium corundum bricks, it has poorer resistance to glass liquid erosion, but better thermal shock resistance.

Sintered zircon bricks

In industrial production, in order to reduce costs and improve economic benefits, cheap and good zircon raw materials have been widely used to manufacture sintered zircon bricks. The zircon raw materials used to make zircon bricks require a purity of 98%~99%, of which the content of ZrO2 should be greater than 63%, and the lower the impurity content, the better. When manufacturing products, the pure zircon fine powder is first pressed into a blank, calcined at about 1600℃, then crushed, formed, and finally fired.

Since zircon is cheaper than zirconium oxide, and natural raw materials are easy to obtain, there is no structural change, the linear expansion coefficient is low, and the thermal shock resistance is also good, it is a very valuable refractory material. Zircon bricks can be used as containers and melting pool bricks for melting alkali-free glass, etc.

Sintered zirconium mullite brick

Sintered zirconium mullite brick is a high-performance refractory brick made of industrial alumina and zircon concentrate as raw materials. Through the reaction sintering process, ZrO2 is introduced into the mullite matrix. The reaction equation is: 3A12O3 + 2ZrSiO4 → 3A12O3·2SiO2+2ZrO2. Mullite has good properties such as high temperature resistance, thermal shock resistance, high temperature creep resistance and good chemical stability. Introducing ZrO2 into mullite and utilizing the phase change toughening of ZrO2 can greatly improve the high-temperature mechanical properties of mullite materials. ZrO2 has a sintering effect on mullite materials. The addition of ZrO2 can accelerate the densification sintering process of ZrO2 materials due to the production of low-melting products or the formation of vacancies.

There are two production processes for producing sintered zirconium mullite bricks: one is to complete the reaction sintering in the process of making refractory bricks to obtain a microstructure with complete phase change; the other is to partially change the phase combination while maintaining a non-equilibrium phase combination. The two production processes have their own characteristics, and both can produce refractory bricks with good performance.