Aluminum carbon brick belongs to the range of aluminum carbon refractory materials. The so-called aluminum-carbon refractory refers to the carbon composite refractory formed by combining alumina raw materials and carbon raw materials, and in most cases, other raw materials such as silicon carbide and metal silicon, bonded with an organic binder such as asphalt or resin material.
Broadly speaking, refractory materials with Al₂O₃+C as the main component are called aluminum-carbon refractory materials. According to the production process, aluminum-carbon refractory materials can be divided into two categories: unburned aluminum-carbon refractory materials and fired aluminum-carbon refractory materials. The performance characteristics are strong erosion resistance, good thermal shock stability, high strength, and high thermal conductivity.
Classification of aluminum carbon brick:
Aluminum-carbon bricks include two types, one is aluminum-carbon bricks containing alumina and graphite, written Al₂O₃-C bricks; the other is aluminum-carbon bricks containing alumina, silicon carbide, and graphite, written Al₂O₃-SiC-C brick. The production processes of the two types of aluminum carbon bricks are different. Al₂O₃-C bricks are fired at high temperature, that is, Al₂O₃-C bricks are fired. Al₂O₃-SiC-C bricks are non-fired bricks that have not been fired at high temperatures. The fired Al₂O₃-C brick has high strength. The typical use is to cast steel skateboard. The non-burning Al₂O₃-SiC-C brick can be added with a variety of special additives, especially with the special properties of anti-alkali, anti-slag, and anti-oxidation. Its typical use is torpedo tank-type hot metal car lining.
Selection of raw materials for aluminum-carbon bricks: refractory aggregates and powders are mainly made of super-grade and first-grade bauxite clinker, and white corundum, brown corundum, and other materials can also be used; carbon materials mainly use flake graphite and medium temperature asphalt; silicon carbide Special grade or first-grade products can also be used dense SiC; phenolic resin used as a binder, its solid content ≥75%, free phenol ≤6%, residual carbon content ≥43%, moisture content ≤2%, density 1.1g/cm³ about. Its general mixing ratio: coarse aggregate 40%~60%, fine aggregate 5%~20%, flake graphite 8%~15%, SiC4%10%, refractory powder 15%~25% and binder 4%~ 6%. In addition, admixtures such as ultrafine powder, anti-alkali agent, and swelling agent are added as needed.
Mixing, forming and heat treatment are similar to magnesium carbon bricks.
Aluminum-carbon bricks are significantly better than magnesium-carbon bricks due to their oxidation resistance and excellent corrosion resistance to Na₂O-based slag, so they are widely used in hot metal pretreatment equipment. The fired aluminum-carbon refractory material (referred to as fired aluminum-carbon brick) belongs to the ceramic combined type or ceramic-carbon composite combined type. It is widely used as a sliding nozzle slide for continuous casting, a long nozzle, an immersed nozzle, bricks for the upper and lower nozzles, and integral plugs. Fired aluminum-carbon bricks become long-life ingot refractories due to their high strength, high erosion resistance, and high thermal shock resistance.
In addition, the modern refractory material used in the blast furnace tapping trench is also an amorphous refractory material made of SiC and C with Al₂O₃ as the main raw material. Although there are many types of iron trench materials, such as ramming materials, plastics, casting materials, vibrating materials, etc., in addition to asphalt or resin, there are chemical bonding, cement, and clay bonding, but they also belong to aluminum-carbon fire The category of materials.
Blast furnace aluminum carbon brick is a good material for blast furnace liner replacement. Its performance is better than that of blast furnace lined traditional refractory bricks. Its performance is similar to silicon nitride combined silicon carbide bricks, and the cost is reduced by 2/3. Therefore, since the advent of aluminum-carbon bricks, it has been used in blast furnaces and has achieved good results.
Because its oxidation resistance is significantly better than that of magnesia-carbon bricks and excellent corrosion resistance to Na₂O slag, it has been widely used in hot metal pretreatment equipment. The fired aluminum-carbon refractory material (referred to as fired aluminum-carbon brick) belongs to the ceramic combined type or ceramic-carbon composite combined type. It is widely used as a sliding nozzle slide for continuous casting, a long nozzle, an immersed nozzle, bricks for the upper and lower nozzles, and integral plugs. Fired aluminum-carbon bricks become long-life ingot refractories due to their high strength, high erosion resistance, and high thermal shock resistance.
In addition, the modern refractory material used in the blast furnace tapping trench is also an amorphous refractory material made of SiC and C with Al₂O₃ as the main raw material. Although there are many types of iron trench materials, such as ramming materials, plastics, casting materials, vibrating materials, etc., in addition to asphalt or resin, chemical bonding, cement, and clay, etc., but also belong to aluminum carbon refractory The category of materials.
Some key factories also use aluminum zirconium carbon skateboards for ladle and tundish, which works well. The use times of aluminum zirconium carbon skateboard in the ladle are more than 3~5 times, and the use times in the tundish can reach 5~10 times. Aluminum-carbon long nozzle and aluminum-carbon zirconium-carbon composite immersion nozzle can be used for continuous pouring 8~12 furnaces.
Damage mechanism of aluminum carbon brick
For the ability of aluminum carbonaceous materials to resist the erosion of slag, Shen Jiyao, and others believe that it has a great relationship with the slag CaO/SiO₂ or Na₂O/SiO₂, the total iron oxide content, particle size, and material matrix phase, and the microstructure of aggregate According to the microstructure analysis of different aluminum carbon materials after use under various slags, the process of slag corrosion damage is considered as the following types:
One is that the carbon-containing matrix phase erodes before the aggregate. If the material has high porosity, high matrix phase content, and poor oxidation resistance: dense aggregate structure, good corrosion resistance, or strong slag oxidation, it may lead to oxidative decarburization of the carbon-containing matrix phase before aggregate, slag Erosion along the decarburization area of the depression, the aggregate is gradually melted in the slag, even falling off This form of erosion is caused by the large difference between the antioxidant and erosion resistance properties of the matrix phase and the aggregate. This small continuous erosion speed is faster.
The second is the simultaneous melting loss of the carbon-containing matrix phase and the aggregate. When the structure of the material is dense and the porosity is low, the oxidation of the slag on the matrix phase and the melting loss of the aggregate are balanced, a simultaneous and uniform corrosion phenomenon of the matrix and the aggregate occurs. In this form of melting loss, each part of the material fully exerts its ability to resist the erosion of the slag, so that the material is continuously and slowly eroded and eliminated.
The third is the peeling and damage of the material working surface, When the carbon-containing refractories are used for a long time at high temperature, oxidative decarburization near the surface layer. Impurities or fine particles promote sintering and densification at this location. The difference between the surface layer and the internal elastic modulus, thermal expansion coefficient, etc., under the effect of thermal shock, the surface of the material is prone to cracks and peeling and damage.
Fourth, the refractory material at the interface between molten slag and molten steel is subject to severe melt loss under the alternating action of molten steel and molten slag.