The difference between sintered AZS bricks and fused AZS bricks

The difference between sintered AZS bricks and fused AZS bricks

Sintered AZS bricks are products made of zircon and alumina as the main raw materials and pre-synthetic materials as aggregates. Since the blank is a barren material, it is not effective to increase the density of refractory bricks by simply increasing the molding pressure. Increased pressing times for large products will also lead to spallation 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 strengthening sintering and other measures to achieve the purpose of dense sintering.

The production principle is based on the solid phase reaction between ZrSio4-AI203:

3AI203+2ZrSio4—>3AI203*2Sio2+2Zro2

This reaction is an irreversible reaction, also known as "in-situ reaction". Due to the large volume effect produced during the reaction sintering process, resulting in deformation and cracks of the green body, zirconium-mullite aggregate has to be pre-synthesized and combined with sintered or fused corundum raw materials to produce three phases of mullite, baddeleyite and corundum. Materials that will be superior to two-phase materials in terms of strength and thermal shock resistance. The microstructure of sintered AZS bricks is characterized by the uniform distribution of fine baddeleyite particles between the main crystal phases of mullite and corundum.

Electrofusion rebonded AZS bricks are made from cast AZS clinker, leftover materials or recycled residual bricks (clearly adhered glass), with a small amount of kaolin or alumina added as a binding agent. When heated to high temperatures, the fused AZS aggregate oozes out the glass phase and binding agent to form mullite, which promotes the sintering of the product. The peritectic reaction between the glass phase and the crystal phase in the electrofused AZS aggregate will also form mullite. At this time, mullite and Zr02 are in the form of wrapping and being wrapped, which is helpful for the sintering of fused cast AZS particles of different sizes. Utilizing the "white sinterability" of cast AZS aggregate is the basic principle for producing rebonded AZS bricks.

The main microstructural changes of high-temperature fired electric fusion bonded AZS bricks are:

① The coarse-grained glass phase exudes to the surface of the particles and reacts with A1203, forming a mullite shell to seal the exudation channel, allowing the peritectic reaction to proceed inside the particles;

②The cast AZS powder glass phase reacts with active A1203, and the matrix is mulliteized. The microstructure of combined AZS bricks has the structural characteristics of dense combination of mullite and corundum baddeleyite eutectic.