The Difference between Sintered AZS Brick and Fused Recombinded AZS Brick

Sintered AZS Brick

Sintered AZS brick is a product made of zircon and alumina as main raw materials and pre-synthetic materials as aggregates. Since the billet is a barren material, only relying on increasing the forming pressure to increase the density of the refractory brick is not good. The increased number of pressings of large products can also lead to the phenomenon of spalling and uneven density. Measures such as adjusting the critical particle size composition, adding a composite binder and a small amount of Ti02, MgO sintering aid and strengthening sintering are needed to achieve the purpose of dense sintering.

3AI₂O₃+2ZrSiO4 —> 3AI₂O₃·2SiO₂+2ZrO₂

The production principle is based on the solid phase reaction between ZrSiO₄ - AI₂O₃:

3AI₂O₃+2ZrSiO₄ —> 3AI₂O₃·2SiO₂+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, only 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.

Sintered AZS bricks should have a relatively stable and uniform phase composition, to avoid long-term non-uniform interphase reactions under the action of high-temperature glass solutions, so that they can operate stably in high-temperature glass solutions for a long time. For this reason, in the sintered AZS brick, the performance indicators and crystal phase structure of the raw materials, the proportion of ingredients and the required particle size composition of the ingredients must be strictly controlled, so that the product can achieve more satisfactory performance indicators and phase structure.

Fused and Recombined AZS Bricks

Fused and recombined AZS bricks are based on melting and casting AZS clinker, scrap or recycled residual bricks (clearly adhered glass) as raw materials, adding a small amount of kaolin or alumina as a binder. When heated to a high temperature, the fused AZS aggregate seeps 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, mullite and Zr02 are in the form of being wrapped and wrapped, which is helpful for the sintering of fused cast AZS particles of different grain sizes. Using this "white sinterability" of fused cast AZS aggregate is the basic principle of producing recombined AZS bricks.

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

1. The glass phase of the coarse-grained material exudes to the surface of the particles and reacts with A1203, forming a mullite shell to close the exudation channel, so that the peritectic reaction proceeds inside the particles.
2. The glass phase of fusion cast AZS powder material reacts with active A1203, and the matrix is mulliteized. Combined with the microstructure of AZS bricks, the eutectic structure of mullite and corundum oblique zircon is densely combined.
3. The dialysis of the glass phase in the coarse particles is exhausted, leaving voids and gaps.

Combining the product with the electric fusion product, the phenomenon of glass phase exudation is greatly reduced, and the exudation temperature is increased, with good thermal shock resistance and high high-temperature mechanical properties. Especially the creep resistance and the glass erosion resistance are also good.