Magnesia alumina brick is a spinel-type alkaline refractory material having a MgO content of about 85%. It can be used as a lattice in place of magnesia chrome bricks and has good corrosion resistance in glass furnace regenerators. RS cheap refractory fire brick for sale supplier, can provide more details about the Magnesia Alumina Brick for Glass Kiln.
Characteristics of Magnesia Alumina Brick
Compared with magnesia bricks, magnesia-aluminum bricks have the following characteristics:
- Magnesia Alumina Bricks have good thermal shock resistance and can withstand water cooling for 20 to 25 times or even higher. This is its most prominent advantage, much better than ordinary magnesia bricks. The study believes that the thermal shock stability of magnesium-aluminum bricks is good because both magnesium-aluminum spinel and periclase belong to the cubic system, and the thermal expansion along the direction of each crystal axis is the same, so the expansion and contraction are relatively uniform when the temperature fluctuates. The resulting thermal stress is small.
- The main properties of Magnesia Alumina Bricks are also slightly stronger than those of magnesia bricks. Since the melting point of the magnesium aluminate spinel itself is higher, the load softening temperature of the magnesium aluminum brick is improved compared to the magnesium brick, reaching 1620 to 1690 °C.
In addition, the ability of magnesium-aluminum spinel to protect the cristobalite particles from slag erosion is stronger than that of calcium-magnesium olivine, so the ability of magnesium-aluminum bricks to resist alkaline slag and iron oxide slag is stronger than that of magnesia.
In summary, the magnesium-aluminum brick has the above excellent performance, so it has been widely used as a masonry material for the top of a high-temperature melting furnace such as a steel-making flat furnace and a copper-refining reverberatory furnace in China, and has achieved the effect of prolonging the life of the furnace. The large open hearth can reach about 300 furnaces, and the small and medium-sized open hearth furnaces are more than 1000 furnaces.
Composition of Magnesia Alumina Brick
Magnesia Alumina Brick is a spinel type or alkaline refractory material having a MgO content of about 85%. The crystal phase composition of the magnesia-aluminum brick is dominated by periclase, and the magnesia-alumina spinel is the matrix (magnesium-aluminum spinel replaces the calcium-magnesium olivine in the magnesia brick to become a binder of periclase). The spinel aggregates to form a network of crystals after crystallization, thereby making the brick structure compact. Since the coarse aggregate particles are not used in the production, the entire brick structure is uniform and the pores are dispersed.
Magnesia Alumina Brick Production Process
The production process of Magnesia Alumina Brick is roughly the same as that of calcined magnesia bricks, except that a certain proportion of industrial alumina or extra-grade bauxite clinker is added to the ingredients. Industrial alumina has a lower impurity content than high alumina bauxite.
The addition of natural bauxite clinker to the ingredients can improve the plasticity of the mud. Under the same conditions, the bulk density of the bricks is higher.
The industrial alumina is generally added in an amount of 5% to 10%, and is usually finely ground with magnesia in a certain proportion, and then added as a fine powder, which is favorable for forming a uniform distribution of the magnesium-aluminum spinel new crystal phase in the matrix of the product.
There are also production methods using pre-synthesized magnesium aluminum spinel for batching bricks.
The critical particle size during the batching is beneficial to improve the thermal shock resistance of the product, but it is not conducive to the density and strength of the product, and generally adopts 3 mm. The particle size is generally 3~1mm and 1~0.088mm and the ratio of 3~2mm coarse particles to less than 0.088mm fine powder should be controlled to improve the thermal shock resistance of the product.
The firing temperature of the Magnesia Alumina Brick is determined according to the purity of the raw material, generally higher than the firing temperature of the magnesium brick by 30 to 50 ° C, and the firing temperature of the high-purity Magnesia Alumina Brick is 1750 to 1800 ° C.
Physical and Chemical Properties of Magnesia Alumina Brick
|MgO (%) ≥||80||80|
|Al2O3 (%) ≥||5 ~ 10||5 ~ 10|
|Apparent Porosity (%) ≤||18||20|
|Cold Crushing Strength (MPa) ≥||40||30|
|0.2 MPa Refractoriness Under Load (℃) ≥||1600||1580|
|Thermal Shock Resistance
(1100℃, water quenching, cycle) ≥
Precautions for the Use of Magnesia Alumina Bricks
Since the thermal shock resistance of the Magnesia Alumina Brick is better than that of the magnesia brick, the softening temperature of the load is higher than 1580 °C. The softening temperature of high-purity magnesium-aluminum bricks (MgO, Al2O3 content greater than 97.5%) can reach 1600~1750 °C. The starting temperature of the load-softening of magnesium-aluminum bricks is generally related to the content of impurities in the bricks, and generally increases with the increase of Al2O3 content. When the content of Al2O3 is 3%~10%, it has a higher value; when the content of Al2O3 exceeds 10%, it begins to decrease. Below 1000 ° C, the modulus of elasticity of the Magnesia-aluminum brick increases with increasing temperature, and after 1000 ° C, the drop is significant. In addition, when the Al2O3 content in the brick is less than 15%, the magnesia-aluminum brick will not expand when it encounters iron oxide. When the content of Al2O3 is 20%, it is more obvious, and at 28%, it will be seriously expanded, causing the brick to crack until it is damaged.
Magnesia Alumina Brick Supplier
RS refractory bricks manufacturer, is of high reputation among the peer industry. Our magnesia bricks production line is with advanced equipment. Our refractory brick products such as magnesia alumina bricks, magnesia chrome bricks, etc. Our refractory technical engineers can solve a variety of refractory problems for you. If you need to buy magnesium aluminum bricks, please contact us.