Magnesia Alumina Brick
Magnesia alumina brick contains about 85% MgO, 5%~10% Al2O3, it is spinel type basic refractory brick. The main crystalline phase of magnesia alumina brick is periclase, magnesia alumina spinel is matrix material( magnesia alumina spinel replaces monticellite and becomes binding agent).
Magnesia Alumina Brick Production Process
The production process of magnesia alumina brick is basically the same as sintered magnesia brick, only certain proportion of industrial Al2O3 or special grade bauxite is added into the batch material. Industrial alumina contains lower impurities than high alumina bauxite clinker. Natural bauxite clinker can improve the plasticity of the molding mixture. The ratio of industrial alumina is usually between 5%~10%. Or pre-synthesized magnesia alumina spinel is adopted to make magnesia alumina brick. The larger the critical particle sizes, the better the thermal shock resistance of magnesia alumina brick, but the lower the bulk density and mechanical strength.
The sintering temperature of magnesia alumina brick is determined by raw material purity, usually, it is 30~50℃ higher than that of magnesia brick. High purity magnesia alumina brick sintering temperature is 1750~1800℃.
Magnesia Alumina Brick Properties
Magnesia alumina bricks has better thermal shock resistance than magnesia brick. To improve magnesia brick thermal shock resistance, Al2O3 or bauxite clinker fine powder is added into magnesia batch material to form magnesia alumina spinel matrix, so, magnesia alumina brick is produced.
Magnesia alumina bricks have high refractoriness under load temperature, good glass liquid corrosion resistance. with the increase of Al2O3 content, the apparent porosity increases accordingly. When Al2O3 content is less than 10%, magnesia alumina brick still has relatively high bulk density, apparent porosity is between 14%~18%.
Magnesia Alumina Brick physiochemical indexes
| Item |
MLZ-80 |
MLZ -85 |
MLZ-88 |
| MgO % |
85 |
88 |
90 |
| Al2O3 % |
7 |
6.5 |
6.5 |
| SiO2 % |
4 |
2.4 |
1.2 |
| CaO % |
1.5 |
1.3 |
1.2 |
| Fe2O3 % |
1.7 |
1.4 |
1.0 |
| Apparent porosity % |
17 |
17 |
17 |
| Bulk density |
2.93 |
2.93 |
2.94 |
| Crushing Strength Mpa |
50 |
50 |
55 |
| Refractoriness under load temperature ℃ |
1610 |
1650 |
1700 |
| Thermal shock resistance (1100℃, water cooling) |
3-6 |
3-6 |
3-6 |
Magnesia Alumina Bricks Applications
Earlier, magnesia alumina bricks are widely used in open hearth steelmaking furnace roof. Nowadays, Magnesia alumina bricks are widely used in steel ladle, steel smelting furnace permanent lining, glass kiln regenerator, metal mixer, copper reflector kiln top and refractory industry high temperature kilns. Magnesia alumina brick is a good replacement of magnesia chrome brick, as magnesia alumina brick has no Cr6+ environment pollution problem, it is environment friendly.
