The chemical component of magnesia brick and varies with the raw materials composition. General magnesium oxide is 55% ~ 60%, the amount of chromium trioxide is about 10%, followed by ferric oxide and a small amount of oxide such as two aluminum dioxide aluminum, silica, calcium oxide and other impurities.
The mineral composition of magnesia brick is mainly magnesium chromium spinel acid magnesium ferrite.
2. Because periclase content of magnesia brick is less than magnesia brick, magnesia chrome spinel and magnesium ferrite content is much , and their melting point of eutectic compounds is lower, so the refractoriness of magnesia chrome brick magnesia brick is low, usually only 1850 ~ 1960 ℃.
3. Refractoriness under load
Periclase crystals of magnesia brick and magnesia chrome spinel is easy to form a mesh skeleton, by filling in the Internet clearance of low melting point no quality is less, when bear high temperature load, while the low melting point material softening, but mesh skeleton still can support the load, so the magnesia brick of refractoriness under load is high, average more than 1550 ℃.A little lower than magnesia brick refractoriness, and refractoriness under load is higher than magnesia brick is a significant characteristic of magnesia chrome brick.
4. Thermal expansion and thermal shock resistance
Magnesia chrome spinel of magnesia brick and magnesium ferrite content is much and linear expansion coefficient is small, at the same time, the porosity of magnesia chrome brick is larger than magnesia brick, so, heat dilatability of magnesia chrome brick is small.
Monticellite content in magnesia brick is few, is not easy to cause differential expansion stress. Magnesium ferrite solid soluble in magnesia chrome spinel, solubility temperature range is very wide, Magnesium ferrite into and precipitation, not make a big stress, therefore, magnesia chrome brick has good thermal shock stability, water-cooled frequency can be up to among 25 times.