The difference between sintered AZS brick and fused AZS brick

What is Sintered AZS brick?

Sintered AZS brick is made of zircon and alumina as main raw materials and pre-synthetic materials as aggregates. Since the blank is a barren material, it is not good to only increase the molding pressure to increase the density of the product. The increase in the number of pressings for large products will also cause the phenomenon of spalling and uneven density. It is necessary to adjust the critical particle size composition, add a composite binder and a small amount of TiO2 , MgO sintering aid and strengthening sintering measures to achieve the purpose of dense sintering.

The production principle of Sintered AZS bricks

It is based on the solid phase reaction between ZrSiO4-Al2O3:

3Al2O3+2ZrSiO4→3Al2O3·2SiO2+2ZrO2

This reaction is irreversible and is also called "in-situ reaction". Due to the large volume effect produced during the reaction sintering process, which leads to deformation and cracks of the green body, the pre-synthesized zirconium mullite aggregates can be prepared with sintered or fused corundum raw materials to produce mullite, oblique zircon and corundum. The material is superior to two-phase materials in terms of strength and thermal shock resistance. The microstructure of sintered AZS bricks is mainly characterized by fine zirconia particles uniformly distributed between the main crystalline phases of mullite and corundum

How fused AZS bricks are formed？

Fused AZS bricks are based on fusion-casting of AZS clinker, scrap or recycled residual bricks as raw materials, adding a small amount of kaolin or alumina as the binder. When heated to a high temperature, the fused AZS aggregate oozes out of the glass phase and the binder to form mullite, which promotes the sintering of the product. The peritectic reaction of the glass phase and the crystal phase in the fused AZS aggregate will also form mullite. At this time, the mullite and ZrO2 are in the form of wrapping and wrapping, which is helpful for the sintering of fused cast AZS particles of different sizes. Utilizing the "self-sintering property" of fused cast AZS aggregate is the basic principle of producing Fusedd AZS bricks.

The main changes in the microstructure of fused AZS bricks after firing at high temperature:

① The glass phase of the coarse-grained material exudes to the surface of the particles and reacts with Al2O3 to form a mullite shell to close the exudation channel so that the peritectic reaction proceeds inside the particles;

②The glass phase of fused cast AZS powder reacts with active Al2O3, and the matrix is mulliteized. Combined with the microstructure of AZS bricks, the eutectic structure of mullite and corundum oblique zircon is densely combined.