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Magnesite brick is widely used in metallurgy (electric furnaces, converters, mixing furnaces), non-ferrous metals (smelting furnaces), high-temperature tunnel kilns, sintered magnesia kilns, building materials (cement rotary kilns, glass melting kilns, new lime kilns), steel rolling (soaking) Furnace, heating furnace) etc.
Magnesia refractory bricks have been finished and passed inspection
Magnesia bricks are alkaline refractory materials mainly made of magnesite, and their basic component is MgCO3. After high-temperature calcination and crushing to a certain particle size, they become sintered magnesia sand, which is widely used as furnace repair materials and ramming materials. The refractoriness of magnesite bricks is above 2000℃, but the load softening point of general magnesia refractory bricks is only 1520℃~1600℃, and the load softening starting temperature is not much different from the collapse temperature. The linear expansion rate of magnesite bricks at 1000℃~1600℃ is generally 1.0%~2.0%, and is approximately linear.
Among refractory products, the thermal conductivity of magnesium bricks is second only to carbon-containing bricks, and it decreases with increasing temperature. Magnesia firebricks can resist the erosion of alkaline slags containing iron oxide and calcium oxide, but are not resistant to the erosion of acidic slags containing silicon oxide, so they cannot be directly in contact with silica bricks when used, and need to be separated by neutral bricks.
Magnesia refractory bricks are widely used in steelmaking furnace linings, ferroalloy furnaces, and mixed iron furnaces in the steel industry due to their good high-temperature performance and strong resistance to alkaline slag; glass industry regenerator lattices and civil heat exchangers; high-temperature calcining kilns in the refractory industry, such as high-temperature vertical kilns for calcining magnesia sand and high-temperature tunnel kilns for firing alkaline refractory bricks.
1. Raw material preparation
The main raw materials for refractory magnesia bricks are magnesia ore (such as magnesite) and a certain proportion of binders. First, the magnesia ore needs to be collected, screened, and crushed to remove impurities and achieve the required particle size. Usually, the magnesia ore needs to be ground into a fine powder to ensure uniform mixing in subsequent processes. At the same time, other refractory materials may be added according to specific requirements to improve the performance and refractoriness of the bricks.
2. Molding
Molding is a key step in the production process. Refractory magnesia fire bricks are usually formed by pressing or extrusion.
Pressing: The mixed raw materials are placed in a mold and a hydraulic press is used to apply high pressure to press the raw materials into bricks. This method is suitable for producing standard-sized refractory bricks with high molding accuracy and density.
Extrusion molding: The raw material mixture is placed in the extruder and the raw materials are extruded and molded by spiral propulsion. It is suitable for producing long strips or special-shaped bricks.
The brick blank after molding needs to maintain appropriate humidity to avoid cracks during the drying process.
3. Drying
The magnesia brick blank after molding generally contains a certain amount of moisture and needs to be dried. Drying can be carried out by natural drying or mechanical drying. Mechanical drying is usually carried out in a drying kiln, using hot air circulation to remove moisture. During the drying process, temperature and humidity need to be strictly controlled to ensure that the brick blank is evenly dried and prevent cracking.
4. Firing
The dried brick blank enters the firing stage. The firing process is usually carried out in a high-temperature kiln, and the temperature range is generally between 1400℃ and 1800℃. At high temperatures, the magnesium oxide in the brick blank undergoes a chemical reaction to form a dense magnesium-aluminum spinel structure, which significantly improves the strength and refractory properties of the refractory brick.
5. Cooling
The fired refractory magnesium brick needs to be gradually cooled. The cooling process can be natural cooling or forced cooling. The latter can reduce the temperature faster and reduce the deformation and cracking of the brick body. During the cooling process, the cooling speed needs to be controlled to avoid thermal stress caused by sudden temperature drop.
