Magnesia brick

Alkaline refractories with magnesium oxide content of more than 90% and periclase as the main crystal phase.

1. The refractoriness of magnesia brick is as high as 2000℃, and the softening temperature under load does not change greatly depending on the melting point of the binding phase and the liquid phase produced at high temperature. Generally, the load softening starting temperature of magnesia brick is 1520～1600℃, while the high-purity magnesium has a heavy softening starting temperature up to 1800℃.

2. The load softening starting temperature of magnesia bricks is not much different from the collapse temperature. This is because the main phase composition of magnesia bricks is periclase, but the periclase crystals in the magnesia bricks do not crystallize the network framework, but are combined. Cemented. In ordinary magnesia bricks, low-melting silicate phases such as forsterite and magnesite pyroxene are generally used as the combination. Although the periclase crystal grains constituting the magnesia brick have a higher melting point, they melt at about 1500°C. The silicate phase exists, and the viscosity of its liquid phase is very small at high temperature. Therefore, it reflects that the load deformation temperature and collapse temperature of ordinary magnesia bricks are not much different, but there is a big difference from the refractoriness. The load-softening start temperature of high-purity magnesia bricks can reach 1800°C, mainly because the combination of periclase grains is forsterite or dicalcium silicate, and the melting temperature of the eutectic formed by it and MgO is high. , The lattice strength between the crystals is large and the plastic deformation at high temperature is small, and the crystal particles are well combined.

3. The linear expansion rate of magnesia bricks at 1000～1600℃ is generally 1.0%～2.0%, and it is approximately or linear. In refractory products, the thermal conductivity of magnesia bricks is second only to carbon-containing bricks. It increases with temperature. High and low. Under the condition of 1100°C water cooling, the number of thermal shocks of magnesia bricks is only 1 to 2 times. Magnesium bricks have strong resistance to alkaline slags containing CaO and ferrite, but weak to acidic slags containing SiO2. To

4. Therefore, it should not be in direct contact with silica bricks when in use, and should be separated by neutral bricks. At room temperature, the conductivity of magnesia bricks is very low, but at high temperatures, its conductivity cannot be ignored. The performance of magnesia bricks varies greatly due to the different raw materials, production equipment, and technological measures used. To

5. Magnesia bricks are widely used in steelmaking furnace linings, ferroalloy furnaces, mixing furnaces, non-ferrous metallurgical furnaces, lime kilns for building materials, and regenerator grids in glass industries due to their good high temperature performance and strong resistance to alkaline slag. Heat exchangers, high-temperature calcining kilns and tunnel kilns in the refractory industry.

6. Generally, it can be divided into two categories: sintered magnesia bricks (also known as fired magnesia bricks) and chemically bonded magnesia bricks (also known as unfired magnesia bricks). Magnesia bricks with high purity and high firing temperature are called direct bonded magnesia bricks due to the direct contact of periclase grains; bricks made of fused magnesia as raw materials are called fused combined magnesia bricks.

7. Alkaline refractory products with periclase as the main crystal phase. The product has the characteristics of high high temperature mechanical strength, good slag resistance, strong erosion resistance, and stable volume at high temperature.

8. Magnesia bricks have high refractoriness, good alkali slag resistance, high starting temperature for softening under load, but poor thermal shock resistance. Sintered magnesia brick is made of brick magnesia brick as raw material. After being crushed, batched, kneaded and shaped, it is fired at a high temperature of 1550 to 1600°C. The firing temperature of high-purity products is above 1750°C. Non-cast magnesia bricks are made by adding appropriate chemical binders to magnesia, then mixing, molding, and drying.

9. Mainly used for steelmaking alkaline open hearth, electric furnace bottom and furnace wall, permanent lining of oxygen converter, non-ferrous metal smelting furnace, high temperature tunnel kiln, calcined magnesia brick and cement rotary kiln lining, furnace bottom and furnace of heating furnace Walls, checkered bricks in the regenerator of the glass kiln, etc.

1. Classification of magnesia bricks

Generally, it can be divided into two categories: sintered magnesia bricks (also known as fired magnesia bricks) and chemically bonded magnesia bricks (also known as unfired magnesia bricks). Magnesia bricks with high purity and high firing temperature are called direct bonded magnesia bricks due to the direct contact of periclase crystal grains; bricks made of fused magnesia as raw materials are called fused combined magnesia bricks.

2. Classification and use of magnesia bricks

Magnesia bricks have high refractoriness, good resistance to alkaline slag, high starting temperature for softening under load, but poor thermal shock resistance. Sintered magnesia brick is made of brick magnesia brick as raw material. After being crushed, batched, kneaded and shaped, it is fired at a high temperature of 1550 to 1600°C. The firing temperature of high-purity products is above 1750°C. Non-cast magnesia bricks are made by adding appropriate chemical binders to magnesia, then mixing, molding, and drying.

Third, the use of magnesia bricks

Mainly used for steelmaking alkaline open hearth, electric furnace bottom and wall, permanent lining of oxygen converter, non-ferrous metal smelting furnace, high temperature tunnel kiln, calcined magnesia brick and cement rotary kiln lining, furnace bottom and wall of heating furnace, Check bricks for regenerator of glass kiln, etc.

Four, index ranking