Sintered AZS bricks are made of zircon and alumina as the main raw materials and pre-synthesized materials as aggregates. Since the blank is a barren material, it is not effective to increase the density of the product by simply increasing the molding pressure. Increasing the number of pressings for large products will also lead to layer cracking and uneven density. It is necessary to adjust the critical particle size composition, add composite binders and a small amount of Ti02, MgO sintering aids and strengthen sintering to achieve the purpose of dense sintering.
The production principle is based on the solid phase reaction between ZrSi04-AI203:
3A1203+2Zrsi04-3A12032Si0 2+2Zr02
This reaction is an irreversible reaction, also known as "in-situ reaction". Due to the large volume effect produced during the reaction sintering process, which leads to deformation and cracks of the body, the zircon mullite aggregate can only be pre-synthesized, and combined with sintered or fused corundum raw materials, mullite, skewness and corundum three-phase materials can be produced, which are superior to two-phase materials in terms of strength and thermal shock resistance. The microstructure of sintered AZS bricks is mainly characterized by fine skewness zircon particles evenly distributed between the main crystal phases of mullite and corundum.
Electrofusion the combined AZS bricks are made of fused AZS clinker, scraps or recycled bricks (removing the adhering glass) as raw materials, with a small amount of kaolin or alumina added as a binder. When heated to a high temperature, the fused AZS aggregate oozes out the glass phase and forms mullite with the binder, 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, mullite and Zr02 are in the form of wrapping and being wrapped, which is conducive to the sintering of fused AZS particles of different particle sizes. The "self-sintering property" of AZS aggregate is the basic principle of producing rebonded AZS bricks.
The microstructural changes of high-temperature fired fused rebonded AZS bricks are mainly ①) the coarse aggregate glass phase seeps out to the surface of the particles and reacts with A1203, forming a mullite shell to close the seepage channel so that the peritectic reaction takes place inside the particles 2) the fused AZS powder glass phase reacts with the active A203, and the matrix is mullitized. The microstructure of rebonded AZS bricks has the structural characteristics of dense combination of mullite and corundum baddeleyite eutectic.
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