During the smelting process, due to improper ingredients or charging and excessive decarburization, sometimes the carbon content in steel or iron does not meet the expected requirements. At this time, carbon should be added to steel or molten iron. The main substances usually used to increase carbon is anthracite coal powder, carbon-increasing pig iron, electrode powder, petroleum coke powder, pitch coke, charcoal powder, and coke powder. The requirement for the carburant is that the higher the fixed carbon content, the better, and the lower the harmful impurities such as ash, volatile matter, and sulfur, the better, so as not to contaminate the steel.
The smelting of castings uses a high-quality carburizing agent after the high-temperature firing of petroleum coke with few impurities, which is the most important link in the carburizing process. The quality of the recarburizer determines the quality of the molten iron and also determines whether a good graphitization effect can be obtained. In short, the carburizer plays a pivotal role in reducing the shrinkage of molten iron.
When all scrap steel is smelted in an electric furnace, the recarburizer that has undergone graphitization treatment is preferred. Only after high-temperature graphitization treatment, the carbon atoms can change from the original disordered arrangement to the flake arrangement, and the flake graphite can become graphite-shaped. The best core of the nucleus to facilitate graphitization. Therefore, we should choose a recarburizer that has been graphitized at a high temperature. Because during the high-temperature graphitization process, the sulfur content is reduced by the escape of SO2 gas. Therefore, high-quality recarburizers contain very low sulfur content, w(s) is generally less than 0.05%, and better w(s) is even less than 0.03%. At the same time, this is also an indirect indicator to judge whether it has been subjected to high-temperature graphitization treatment and whether the graphitization is good. If the selected recarburizer has not undergone high-temperature graphitization treatment, the nucleation ability of graphite will be greatly reduced, and the graphitization ability will be weakened. Even if the same amount of carbon can be achieved, the result is completely different.
The carburizer is to effectively increases the carbon content in the molten iron after adding it, so the fixed carbon content of the carburizer must not be too low, otherwise, to achieve a certain carbon content, it is necessary to add a higher carbon More samples of recarburizer will undoubtedly increase the amount of other unfavorable elements in the recarburizer, so that the molten iron cannot obtain better returns.
Low sulfur, nitrogen, and hydrogen elements are the key to preventing nitrogen pores in castings, so the lower the nitrogen content of the carburizer, the better. Other indicators of the carburant, such as moisture, ash, and volatile matter, the lower the amount of fixed carbon, the higher the amount of fixed carbon, so the higher the amount of fixed carbon, the content of these harmful components must not be high.
According to different smelting methods, furnace types, and sizes of smelting furnaces, it is also very important to choose the appropriate particle size of the carburizer, which can effectively improve the absorption speed and rate of the carburant by the molten iron, and avoid the loss of recarburizer due to too small particle size. The oxidative burning of the carburant caused.
The particle size is preferable: less than 10mm for a 100kg furnace, less than 15mm for a 500kg furnace, less than 20mm for a 1.5-ton furnace, and less than 30mm for a 20-ton furnace. In converter smelting, when high carbon steel is used, a recarburizer with few impurities is used. The requirements for carburizers for top-blown converter steelmaking are high fixed carbon, low content of ash, volatile matter, sulfur, phosphorus, nitrogen and other impurities, and dry, clean, and moderate particle size. Its fixed carbon C≥96%, volatile matter≤1.0%, S≤0.5%, moisture≤0.5%, and particle size is 1-5mm. If the particle size is too fine, it is easy to be burned, and if it is too coarse, it will float on the surface of molten steel after being added, and it will not be easily absorbed by molten steel. For the induction furnace, the particle size is 0.2-6mm, among which the particle size of steel and other ferrous metals is 1.4-9.5mm, and the high-carbon steel requires low nitrogen, and the particle size is 0.5-5mm. Contact us for specific judgment and selection of the type and other details.