Magnesium chromite brick is a special refractory material which is made of high chromium ore by sintering. It consists of free SiO2 and 50% of MgO and the rest exists in the form of $theta$-Cr2O3 phase. It has good resistance to acid and alkaline slags and is an ideal material for blast furnace and converter linings.
Magnesium chromite brick has high refractoriness, strong acid and alkali resistance and high thermal shock resistance. Its service temperature can reach up to 1700-1800 ℃. It has good resistance to rapid cooling and thermal shock resistance, and has the advantages of low thermal conductivity and high apparent porosity. Magnesium chromite brick also has good hot strength, corrosion resistance and anti-spalling oxidation resistance.
The raw materials used to make magnesium chromite brick include high-chromium oxide, yellow phosphorus oxide, silicon dioxide, magnesium oxide, etc. The production process of magnesium chromite brick is mainly composed of grinding and batching of raw materials, pressing and blanking of greenbodies, calcination of greenbodies, watercooling, aging and packing.
The production of magnesium chromite brick follows certain technical conditions. First, the chemical composition should be properly controlled. The raw material should be required to have stable chemical composition, and the chemical composition of calcined bricks should meet the requirements of national standards. Second, the calcination temperature should be strictly controlled. Magnesium chromite brick is required to be fired twice, and the temperature in the first firing is rather high. If the temperature is too high, it will reduce the apparent porosity, increase the thermal conductivity, reduce the refractoriness of the brick, and cause the SiO2 to crystallize, hurting the physical and mechanical properties of the bricks. Therefore, the temperature should be strictly controlled within the specified range.
In conclusion, magnesium chromite brick has the advantages of high refractoriness, strong acid and alkali resistance, high thermal shock resistance and corrosion resistance. To get good refractory bricks, it is necessary to strictly control the production process and technical conditions.
