Refractory Casting Zirconium Mullite Brick for Steel Plant

Zirconium mullite brick is a fused cast refractory product with mullite and zirconia as raw materials. Zirconium mullite cast brick has dense crystal structure, high softening temperature under load, good thermal stability, high mechanical strength at room temperature and high temperature, good wear resistance, good thermal conductivity, and excellent resistance to erosion.

Sintered zirconium mullite brick is a high-grade refractory brick made of industrial alumina and zirconite concentrate as raw materials, and ZrO2 is introduced into the mullite matrix through the reaction sintering process. The reaction equation is as follows: 3A12O3 ten 2ZrSiO4→3 A12O3·2SiO2+2ZrO2 Mullite ceramics have many excellent characteristics, such as high temperature resistance, thermal shock resistance, high temperature creep resistance and good chemical stability.

When ZrO2 is introduced into mullite ceramics, the high temperature mechanical properties of mullite materials can be greatly improved by the phase transition toughening of ZrO2. ZrO2 can promote the sintering of mullite materials. The addition of ZrO2 can accelerate the densification and sintering process of ZrO2 materials due to the generation of low melts or the formation of vacancy. When the molar fraction of ZrO2 is 30%, the relative bulk density of the billet sintered at 1530ºC can reach 98%. The strength reaches 378MPa and the toughness reaches 4.3MPa·m1/2. The strengthening and toughening mechanisms of ZrO2 materials with different compositions are different.

When the volume fraction of ZrO2 is 15%-30%, ZrO2 is mainly toughened by stress-induced phase change. When the volume fraction of ZrO2 is greater than 30%, the ZTM material is mainly toughened by micro-cracks. The particle size of ZrO2 powder has a great influence on the mechanical properties of ZrO2 material.

ZrO2 has a large particle size, and most of the Z voles in the ZTM material matrix are in the form of M-Zro2, and the material is mainly toughened by micro-cracks. When the particle size of ZrO2 is small, the relative content of t-ZrO3 in ZTM material is higher, and the improvement of mechanical properties of the material is mainly due to the phase transition toughening of t-ZrO3.

By introducing ZrO2 into A12O3-sio2 bricks to improve the structure of mullite, it can improve the chemical erosion resistance, shock resistance and reduce the expansion coefficient of mullite, this ZRO2-containing mullite brick, commonly known as zirconium mullite brick, is generally obtained by electric melting method, but also useful sintering method production. Sintered zirconium mullite brick is a special refractory made by using industrial alumina and zircon concentrate as raw materials and introducing zirconia into mullite matrix by reaction sintering process.

It is difficult to control the process of zirconium mullite brick made of industrial alumina and zircon by reaction sintering because the reaction and sintering are carried out simultaneously. Generally, during the sintering process, it is first held at 1450ºC to densitize, and then heated to 1600ºC for reaction. ZrSiO4 is decomposed into ZrO2 and SiO2 at a temperature greater than 1535ºC, in which SiO2 and Al2O3 react to produce mullite. Due to the decomposition of ZrSiO4, some liquid phase appears. Moreover, the decomposition of ZrSiO4 can refine the particles and increase the specific surface area, thus promoting sintering.

The results show that when the addition of zircon is less than 54.7%, the microstructure of the sintered sample is gradually changed from columnar corundum to columnar mullite with the increase of the addition of zircon. The high temperature flexural strength of the sample (1400. C) It also increases with the increase of zirconia content, and a large value appears when the zirconia content is 23.7%, and then the strength decreases. The addition of zircon helps to improve the thermal shock resistance