Aluminum carbon refractory

For refractory products with long continuous casting time and high temperature, the content of Al2O3 must be increased and the content of SiO2 must be decreased. At present, aluminum-carbon refractories are mainly made of electrofused corundum, sintered corundum or sintered plate-shaped corundum. The raw material of electrofused or sintered alumina is expensive and hard, so it is difficult to make al2o3-c slide brick smooth. Therefore, based on the characteristics of resources in our country, choose premium grade or Ⅰ high-quality bauxite clinker as grain, corundum powder production Al2O3 - C brick, can raise the Al2O3 content of matrix, and can be appropriately improve thermal shock resistance and erosion resistance of the product, the actual use effect is good.
So, particulate material in the aluminum carbonaceous ingredients are mainly sintered corundum, fused corundum, sintered tabular corundum (skateboard material), super, Ⅰ grade bauxite clinker; Corundum fine powder or electrofused mullite, sintered mullite fine powder, or zirconium mullite fine powder can be used. Adding a certain amount of carbon into the products is beneficial to improving the properties of the products and prolonging the service life. Carbon has high melting point, small linear expansion coefficient and good thermal conductivity. Carbon can penetrate into the pores of the particles in the products or form a vein-like network of carbon chains between the particles, forming a "carbon bond", thus reducing the porosity of the products and improving the high-temperature strength of the products. Carbon can also form surfaces that are resistant to metals and slag, improving the corrosion resistance and heat resistance of products. In addition, the presence of carbon creates conditions for the reduction of iron and silicon oxide, and the resulting metal and refractory do not react chemically. When the oxide is reduced by carbon, the resulting gas prevents the molten oxide from penetrating into the refractory. Carbon can also improve the thermal conductivity of products, to avoid the individual parts of products because of temperature overheating uneven and lead to brick peeling, fracture.
So, the carbon raw material in aluminium carbon brick is given priority to with flake shape natural graphite, also can use hot connect high pure graphite, still join carbon black normally.
Antioxidants are metal Al, Si powder and SiC powder. Adding a small amount of antioxidant can delay the oxidation of the carbon layer and improve the service life of the product. Figure 13-9 and figure 13-10 are the production process flow charts of aluminum carbonaceous slide plate and aluminum carbonaceous continuous casting, respectively.

Aluminum carbon skateboards brick USES a function is continuous casting refractory material, widely used in electric furnace, converter, ladle refining outside the furnace and continuous casting tundish slide gate system, it as a switch to control the molten steel flow and flow velocity, has high temperature strength, good erosion resistance, erosion resistance and thermal shock resistance, but also requires a high dimensional accuracy. Two or more kinds of carbon raw materials are generally used in the batching. The total carbon content in the skateboard fluctuates between 5% and 15%. The forming equipment of slide plate brick is large friction press brick machine, oil press brick machine. Due to the inevitable existence of a certain number of pores and micro-cracks in the aluminum carbon slide brick during molding, it is impossible to eliminate these pores and cracks during firing due to the different linear expansion coefficients of solid phase components in the product and the small amount of liquid phase. These uneven pores and microcracks affect the thermal shock resistance of the products. When in contact with molten steel, the blowhole is eroded first, causing accelerated damage to the product. In order to overcome the above disadvantages, the asphalt impregnated with medium temperature asphalt was used to fill the pores, and the carbon content of the products was further increased, the strength of the products was increased and the corrosion resistance of the products was improved.
In order to improve the erosion resistance and erosion resistance of the edge of the sliding plate brick casting hole, the sliding plate brick should be formed as a whole, and the required size of the casting hole should be drilled with the diamond bit after firing, so as to make the density around the casting hole uniform. Impregnate after drilling. In order to prevent the sliding plate brick from cracking or crack expanding during use, iron band is used around the sliding plate to improve the safety of use.
The finished product can be obtained after the molding brick is reduced and fired with buried carbon, oil immersion treatment, heat treatment and machining with vacuum oil immersion equipment. In the aluminum carbon slide, the organic binder is carbonized and coking in the reduction firing to form carbon bond. When the additive Si is reduced and fired at 1300℃, it generates beta SiC with carbon and forms ceramic binding in the brick body. Therefore, there are two kinds of binding systems in aluminum-carbonaceous refractories, which can significantly improve the strength of aluminum-carbonaceous refractories and maintain sufficient residual strength even after carbon has been burnt out in use due to the action of ceramic binding system.
Aluminum carbon long nozzle is usually in the ladle moved to the tundish above the suit, most of the long nozzle is not through preheating or preheating is not fully connected directly to the ladle, which requires the long nozzle has excellent thermal shock resistance, therefore, long nozzle carbon content is higher, generally 20%~40%.
Aluminum carbonaceous immersion nozzle is a weak link in the continuous casting process, and its service life determines the time of continuous casting and the quality of steel. Therefore, immersion nozzle has been studied most among the three large pieces of continuous casting, and its carbon content is generally about 30%.
Aluminum carbon brick commonly used binder: resin, tar, asphalt, etc. Practice shows that thermoplastic phenolic resin binder and ulotropin [(CH7) N4] hardener are used to form insoluble and insoluble solidified materials.
For long nozzle, submerged nozzle and integral plug rod, CIP (Cold Isostatic Pressing) is generally adopted for molding equipment due to the particularity of appearance. CIP works by placing the product in an airtight container and applying equal pressure in each direction to the product. Under the action of high pressure, the product can be shaped and densified.
Long nozzle and immersion nozzle after firing (or before firing) with the lathe to the user's required size, in order to prevent the product in use of rapid oxidation decarburization, the surface of the product should be coated with a layer of anti-oxidation coating to prevent graphite oxidation.
For not burning aluminum carbonaceous refractory, commonly used raw materials are: corundum, mullite and Ⅰ and Ⅱ contour bauxite clinker, flake graphite, SiC, Si, etc.
Compared with sintered aluminum carbonaceous refractory, non-sintered aluminum carbonaceous refractory has the following characteristics: no sintering, oil immersion and dry distillation heat treatment, simple process, but compared with sintered aluminum carbonaceous refractory slide, low strength and high porosity.
(1) corundum. Corundum has good erosion resistance but high expansion coefficient, so the thermal shock resistance of aluminum-carbonaceous refractory is not very ideal, especially for sliding nozzle system.
(2) carbon. Carbon material has great influence on the erosion resistance and thermal shock resistance of slide plate. Generally, when the carbon content is 10%, the corrosion resistance is the best. With the increase of carbon content, the thermal shock resistance was obviously improved. Carbon black is an amorphous nanometer material, which can easily react with Si and is difficult to dissolve in steel. Generally, two or more kinds of carbon raw materials are used, and the total carbon content in the skateboard is from 5% to 15%.
(3) additives. The additive Si reacts with carbon to produce beta-sic, forming a certain degree of ceramic binding, and the remaining Si is favorable against oxidation. In the range of 0~7%, the more Si is added, the better the antioxidant effect is. The thinner Si powder is, the more evenly distributed it is. A small amount of Al powder can significantly improve the products at room temperature pressure and flexural strength (high temperature); When the total Si+Al is 5% and Si/Al=1, the material has the best oxidation resistance and erosion resistance.
(4) oil immersion process. Oil immersion can decrease the porosity of al carbon refractories and increase the amount of carbon residue, so as to improve the strength, thermal shock resistance and corrosion resistance of al carbon refractories.