Roasting refers to the process of forming the graphite electrode green body in a protective medium in a roasting heating furnace under high-temperature heat treatment at a certain heating rate under the condition of air isolation to carbonize the coal pitch in the process of deterioration. China graphite electrode manufacturer shares with you.
The coal-bitumen binder contained in the graphite electrode green body undergoes pyrolysis and polycondensation reaction during firing to form coking coke (asphalt coke). It forms cohesive coke grids between carbonaceous aggregate particles, firmly holding all aggregates of different sizes Combined, the graphite electrode has certain strength and physical and chemical properties. The graphite electrode made by firing has higher mechanical strength, lower resistivity, better thermal stability, and chemical stability.
The purpose of electrode firing is to:
1. Exclude volatiles. In the process of roasting heat treatment, the coal asphalt contained in the blank will undergo thermal decomposition and condensation reaction, and the unstable light components will be eliminated in the form of volatiles. The emission of volatiles is about 10%, so the rate of roasting products is generally below 90%.
2. Coking of the adhesive. After calcination and heat treatment, the coal pitch binder is pyrolyzed and polycondensed to generate densely structured coke (asphalt coke). The carbonaceous aggregate particles are firmly combined into one body, and the graphite electrode is given performance.
3. Fix the shape of the product. Although the green compact after molding has a certain shape, since the binder remains intact, the green compact is easily softened and deformed after being heated. Through the coking of the binder during the firing process, the coke binds the aggregate particles together, the shape of the product is fixed, and the volume of the product also obtains a certain stability.
4. Improve the electrical conductivity of the product. Along with the scorch of coal pitch binder and a large amount of volatiles during the firing process, the electrical resistivity of the carbon product is greatly reduced, and the resistivity of the green compact is about 10,000 μΩ · m. The resistivity of the carbon product after firing is reduced to 30 ~ 60μΩ · m thus effectively improving the electrical conductivity of carbon products.
5. Improve the physical and chemical properties of products. In the roasting process, the binder coking, product volume shrinkage, mechanical strength, true density, oxidation resistance, thermal conductivity, electrical conductivity, and corrosion resistance have been greatly improved, so that the baked products have good physical and chemical properties and performance.
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