What are the Performance and Use of Magnesia Brick?

Magnesia bricks have good high-temperature performance and strong resistance to alkaline slag. It is widely used in steelmaking furnace lining, ferroalloy furnace, mixed iron furnace, nonferrous metallurgical industry furnace, and limestone kiln in the steel industry. Heat exchangers for lattices of regenerators in the glass industry, high-temperature calcination kilns, and tunnel kilns in the refractory industry. The performance of magnesia bricks is greatly different due to the different raw materials, production equipment, and technological measures adopted.

High-Quality Magnesia Bricks

The refractoriness of magnesia bricks is as high as 2000℃, and the load softening temperature does not change greatly with the melting point of the bonding phase and the liquid phase produced at high temperatures. Generally, the load softening starting temperature of magnesium bricks is 1520～1600℃, while the heavy softening starting temperature of high purity magnesium bricks can reach 1800℃.

The load softening start temperature of the magnesia brick is not much different from the collapse temperature, because the main phase composition of the magnesia brick is periclase.

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The brucite crystals do not crystallize the network skeleton in the magnesia brick, but are cemented by the combination. In ordinary magnesium bricks, silicate phases of low melting point, such as calcium magnesium olivine and magnesite, are generally used as a combination. Although the granite of the magnesite constituting the magnesia brick has a high melting point, there is a silicate phase melted at about 1500°C, and its liquid phase viscosity is very low at high temperature. Therefore, the load deformation temperature of ordinary magnesium bricks is not much different from the collapse temperature, but there is a big difference from the refractoriness. The load softening starting temperature of high-purity magnesium bricks can reach 1800℃. The main reason is that the combination between the perovskite grains is forsterite or dicalcium silicate. Moreover, the melting temperature of the eutectic formed with MgO is high, the lattice strength between crystals is large and the plastic deformation at high temperature is small, and the crystal particles are well bonded.

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The linear expansion rate of magnesia brick at 1000～1600℃ is generally 1.0%～2.0%, and it is approximate or linear.

In refractory products, the thermal conductivity of magnesium bricks is second only to carbon-containing bricks, which decreases with increasing temperature. Under the condition of 1100℃ water cooling, the number of thermal shocks of magnesia bricks is only 1-2. Magnesia brick has strong resistance to alkaline slag of CaO and ferrite, but weak resistance to acid slag containing SiO2. Therefore, it can't be in direct contact with silicon bricks during use. Generally, it should be separated with neutral bricks.

At room temperature, the conductivity of magnesia bricks is very low, but at high temperatures, its conductivity will not be ignored.