Application of Unburned Aluminum-Magnesia Bricks and Aluminum-Magnesia-Carbon Bricks in Ladle Lining

With the emergence of oxygen-blown converters and continuous casting, clay bricks (even high-alumina bricks) for ladle lining are no longer applicable. In the early stage of high-alumina and basic ladle lining, the successful development and application of unburned aluminum-magnesium bricks and later aluminum-magnesium carbon bricks took up a considerable period of time. Even during the promotion of pure aluminum-magnesium castable integral ladle lining, aluminum-magnesium carbon bricks were still important materials for ladle lining. Rongsheng Refractory Brick Manufacturer can provide high-quality aluminum-magnesium bricks and aluminum-magnesium carbon bricks for ladle lining. It is a powerful manufacturer and seller of refractory materials. Contact Rongsheng for detailed information.

Unburned Aluminum-Magnesium Bricks for Ladle Lining

Unburned aluminum-magnesium bricks for ladle are unburned refractory products for ladle lining made of high-alumina bauxite clinker and magnesia as raw materials. As the temperature of molten steel in the ladle increases and the residence time increases, the clay brick lining is seriously eroded. While using high-alumina bricks, aluminum-magnesium unburned bricks can replace clay bricks and low-grade high-alumina bricks. This unburned aluminum-magnesium brick is made of special or first-grade high-alumina bauxite and first-grade brick-making magnesia as raw materials, and water glass as a binder, and is mixed in a certain proportion. The fine magnesia powder and the fine alumina powder are mixed and finely ground together, mixed and formed by a brick press, dried to 200℃, and passed the quality inspection to become the finished product. The typical physical and chemical properties of this brick are: Al2O3 72%, MgO 9.8%, bulk density 2.63~2.85 g/cm3, apparent porosity 20%~21%, room temperature compressive strength 52.2~117MPa, and load softening start temperature 1420℃.

Since the amount of MgO added in the batch is calculated based on the SP composition of the entire matrix, the unburned aluminum-magnesium brick has good thermal shock resistance and alkaline slag corrosion resistance. However, due to the introduction of low-melting-point substances such as Na2O in the water glass binder, its high-temperature strength and load softening temperature is low. In addition, since the thermal conductivity of this brick is higher than that of clay bricks, it is easy to freeze cold steel and stick slag in the bag, so preheating and insulation measures should be taken during use.

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Aluminum-Magnesium-Carbon Bricks for Ladle Lining

RS refractory brick manufacturer, in a broad sense, refractory materials with alumina, magnesia, and carbon as the main components can be collectively referred to as aluminum-magnesium-carbon refractory materials. Aluminum-magnesium-carbon bricks are unfired-shaped refractory products made of high-alumina bauxite clinker (or corundum), magnesia (or magnesia-aluminum spinel SP) and graphite as the main raw materials, combined with asphalt or resin. Aluminum-magnesium-carbon refractory products can be divided into two categories according to the content of alumina or magnesia. One is aluminum-magnesium-carbon bricks with alumina as the main component, usually represented by AMC or LMC. The other is magnesium-aluminum-carbon bricks with magnesium oxide as the main component, usually represented by MAC or MLC.

With the emergence of continuous casting ladles and refining ladles outside the furnace, the temperature of molten steel in the ladle has increased and the residence time has been extended. The original lining clay bricks, high-aluminum bricks and aluminum-magnesium unfired bricks can no longer meet the use requirements. Aluminum-magnesium-carbon bricks are unfired bricks developed in the late 1980s. In order to improve the performance of unfired alumina-magnesia bricks bonded with water glass in small and medium-capacity ladles, graphite was added, which increased the service life, but it was soon replaced by resin-bonded alumina-magnesia-carbon bricks.

Aluminum-Magnesium Carbon Brick

Aluminum-magnesium carbon brick is developed on the basis of carbon-containing bricks such as magnesium-carbon brick and aluminum-carbon brick, absorbing the characteristics of aluminum-magnesium refractory materials, and has the advantages of both carbon-containing refractory materials and aluminum-magnesium refractory materials. This carbon composite unfired brick not only has excellent chemical and thermodynamic stability but also has excellent thermal and mechanical properties:

(1) High resistance to molten steel and slag penetration. Due to the reaction of MgO fine powder and alumina fine powder in the matrix during high-temperature use, SP is generated in situ with controllable volume expansion. It is conducive to the densification of bricks and prevents molten steel and slag from penetrating from the working surface and mortar joints of bricks.

(2) Excellent slag erosion resistance. In addition to the anti-erosion effect of graphite, SP generated in situ during use can absorb FeO in slag and form a solid solution. Al2O3 reacts with CaO in slag to form a high melting point CaO-Al2O3 compound. It plays a role in blocking the pores of bricks and increasing the viscosity of the melt, achieving the purpose of inhibiting slag penetration and resisting slag erosion.

(3) High mechanical strength. Compared with MgO-C bricks and Al2O3-C bricks, the amount of graphite added in aluminum-magnesium-carbon bricks is less, generally 6%~12%. Therefore, it has the characteristics of high volume density, low porosity, and high strength.

The production process of alumina-magnesia-carbon bricks is the same as that of MgO-C bricks. Taking measures to make the mixing uniform and increase the molding pressure is the basic condition to ensure the excellent performance of alumina-magnesia-carbon bricks in the process. The purity of the main raw materials of alumina-magnesia-carbon bricks has a large fluctuation range. The raw materials containing alumina can be first-grade high-alumina bauxite clinker, special-grade high-alumina bauxite clinker, brown corundum, sintered corundum, and fused corundum. The raw materials containing magnesium oxide can be sintered magnesia sand and fused magnesia sand. The carbon raw material is mainly natural flake graphite. The binder is usually synthetic aldehyde resin. The antioxidant uses SiC and Al powder.

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The raw materials containing alumina generally account for 80%-85% of the total ingredients of alumina-magnesia-carbon bricks and can be added to the ingredients in granular and fine powder form. There are many types of raw materials containing alumina, but high-alumina bauxite contains high impurities such as SiO2, which can reduce the slag resistance of the brick. Compared with fused corundum, sintered corundum has fine crystals and more grain boundaries. The slag resistance of aluminum-magnesium-carbon bricks made of sintered corundum is not as good as that of aluminum-magnesium-carbon bricks made of fused corundum under the same conditions.

Among the raw materials containing magnesium oxide, compared with sintered magnesia, fused magnesia has coarse grain size, high volume density, and high MgO content, so it has strong resistance to slag erosion. Fused magnesia is generally added to the ingredients of unfired aluminum-magnesium-carbon bricks, and it is mainly added in the form of fine powder, and the addition amount is generally controlled within 15%. With the appropriate amount of magnesia fine powder added, the volume expansion effect generated by the in-situ SP during use is conducive to blocking the pores of the brick. However, when too much magnesium oxide fine powder is added, too much SP generation causes excessive volume expansion, and excessive thermal stress and cracks will be generated inside the brick, reducing the strength of the brick.

The carbon raw material of aluminum-magnesium-carbon bricks is generally based on natural flake graphite. In order to avoid low-temperature oxidation of graphite in actual use and an excessive temperature drop of molten steel in the ladle due to the high thermal conductivity of graphite, the amount of graphite added is generally controlled within 10%.

The binder used in aluminum-magnesium-carbon bricks is the same as other carbon-containing refractory materials, mainly synthetic phenolic resin, and its addition amount is generally 4%~5% depending on the molding equipment. Resin-bonded aluminum-magnesium-carbon bricks are not only used in the melt pool of electric furnace continuous casting ladles and converter continuous casting ladles but also occupy a considerable proportion in the melt pool of large-capacity brick-built refining ladles.

Rongsheng Refractory Brick Manufacturer

Rongsheng Refractory Brick Manufacturer is a powerful manufacturer and seller of refractory bricks. Rongsheng Manufacturer can provide high-quality refractory bricks and refractory castables for the working lining of the ladle. Refractory bricks include high-alumina bricks, insulation bricks, aluminum-magnesium bricks, aluminum-magnesium-carbon bricks, etc. Rongsheng Manufacturer’s refractory castable products also provide high-quality material supply for the overall ladle lining. Contact Rongsheng to get free samples, quotes, and ladle lining solutions.