Magnesia bricks are usually called sintered magnesia bricks, are kind of basic fire bricks with the largest output and widest applications. According to the MgO content, magnesia bricks can be divided into 3 grades: 90, 95 and 98. The corresponding minimum MgO content is 86%, 91% and 96%. By production craft, magnesia bricks can also be divided into burned magnesia brick, unburned magnesia brick, fused re-bonded magnesia brick and chemically re-bonded magnesia brick.
RS Refractory notes that, the production flow of sintered magnesia brick are: magnesia sand → grinding → dosing → mixing → molding → drying → sintering → selecting → packing.
Magnesia Bricks Characteristics
Magnesia bricks have a refractoriness of over 2000℃. But refractoriness under load temperature of MgO bricks varies hugely with the melting point of cementation facies and the quantity of high temperature liquid phase. The rupture under load temperature of ordinary magnesia brick begins at 1520~1600℃, while the high purity magnesia brick can reach to 1800℃.
Thermal conductivity rate of magnesia brick is very high, only lower than carbon bricks. Magnesia brick can resist ferric oxide containing and calcia containing basic slag corrosion, but can’t resist silica containing acid slag corrosion. So, magnesia bricks should not directly contact with silica bricks during using, and should be separated by neutral bricks.
Magnesia Bricks Properties
| Item | SMZ-89 | SMZ-91 | SMZ-93 | SMZ-95 |
| MgO %≥ | 89 | 91 | 93 | 95 |
| SiO2 %≤ | / | / | 3.5 | 2.0 |
| CaO % ≤ | 3.0 | 3.0 | 2.0 | 2.0 |
| Apparent porosity %≤ | 20 | 18 | 18 | 18 |
| Cold Crushing Stength Mpa≥ | 50 | 60 | 60 | 60 |
| Refractoriness under load ℃≥ | 1550 | 1560 | 1620 | 1650 |
| Permanent linear change (1650℃, 2h) % | -0.6~0 | -0.5~0 | -0.4~0 | -0.3~0 |
| Thermal conductivity coefficient (1000℃)(w/m.K) ≤ | / | 3 | / | 3.8 |
Magnesia Bricks Applications
Magnesia bricks have good high temperature performance and strong metallurgical slag corrosion resistance. So magnesia bricks are widely used in steel smelting furnace lining, iron alloy furnace, iron mixing furnace of steel industry, nonferrous metals smelting furnaces linings such as copper, lead, stannum, zinc and so on. Magnesia bricks are also used in lime calcining kiln, glass kiln regenerative chamber checker, high temperature sintering kiln, such as magnesia sand sintering high temperature vertical kiln, basic bricks sintering high temperature tunnel kilns, etc.
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