In recent years, more and more factories use the induction electric furnace for cast iron, but usually only the metal material can not keep the carbon content in iron, so that's why it need the recarburizer. For the induction electric furnace, special the intermediate frequency furnace, adding the carbon material is important link for smelting.
1. Shoul choose the carbon additive(calcined petroleum coke) with low nitrogen
The usual nitrogen content in cast iron liquid is below 100 ppm. If the nitrogen content exceeds this concentration (150-200 ppm or higher), it is easy to cause cracks, shrinkage or loose defects in the casting, and thick-walled castings are more likely to occur. This is caused by an increase in the amount of recarburizer added when the proportion of scrap steel increases. Coke-based recarburants, especially bitumen coke, contain large amounts of nitrogen. The graphite graphite has a nitrogen mass fraction of 0.1% or less or a very small amount, and the pitch pyrolysis mass fraction is about 0.6%. If 2% of the recarburizer with a mass fraction of 0.6% nitrogen is added, this increases the nitrogen content by 120 ppm. A large amount of nitrogen is not only liable to cause casting defects, but also nitrogen can promote pearlite compaction, ferrite hardening, and strongly increase strength.
2. Ways to adding the recarburizer
The stirring of molten iron can promote carbon addition. Therefore, the medium frequency induction electric furnace with weak stirring force is much more difficult to increase carbon than the power frequency induction electric furnace with strong stirring power. Therefore, the medium frequency induction electric furnace has the carbonization speed and the melting rate of the metal charge The possibility.
Even in a power-frequency induction furnace with high stirring power, the carbon-increasing operation cannot be ignored. This is because, from the schematic diagram of the induction furnace melting, there is a stirring iron flow separated vertically in the induction furnace, and there is a dead angle near the furnace wall at the boundary. The graphite cluster which stays on the furnace wall and adheres cannot be melted into the molten iron without excessive temperature rise and long-term iron liquid heat preservation. Excessive heating of the molten iron and long-term heat preservation will increase the degree of supercooling of the molten iron and increase the tendency of the cast iron to become white. In addition, for medium frequency induction furnaces that generate a strong induced current near the furnace wall, if molten iron is drilled between the graphite clusters attached to the furnace wall, the drilled metal is melted during the next furnace smelting, resulting in erosion. And damage the furnace wall. Therefore, in the case where the proportion of scrap steel is high and the amount of recarburizing agent is added, it is necessary to pay more attention to the addition of the recarburizing agent.
The addition time of the recarburizer cannot be ignored. If the addition time of the recarburizing agent is too early, it is easy to adhere to the vicinity of the bottom of the furnace, and the recarburizing agent adhering to the furnace wall is not easily melted into the molten iron. On the contrary, if the joining time is too late, the timing of carbon increase will be lost, causing the smelting and heating time to be slow. This not only delays the time of chemical composition analysis and adjustment, but also may cause harm due to excessive temperature rise. Therefore, the recarburizing agent is preferably added little by little during the process of adding the metal charge.
The recarburizer contains: fixed carbon, moisture, ash, volatile matter, sulfur, nitrogen, and so on. Different types of recarburizers with certain different content.
Calcined petroleum coke recarburizer is widely used in many industries. Calcined petroleum coke recarburizer can be used in steel making, iron making, ordinary casting and other industries; calcined petroleum coke recarburizer can also be used to make brake discs on casting, Crankshaft, brake pads, etc.
Graphitized petroleum coke also widely used in industry for metallurgy, casting, precision casting as a recarburizer, for the production of high temperature smelting, lubricants for the mechanical industry, making electrodes and pencil lead, widely used Advanced refractory materials and coatings for the metallurgical industry, stabilizers for military industrial pyrotechnic materials, pencil cores for light industry, carbon brushes for the electrical industry, electrodes for the battery industry, catalysts for fertilizer industries, etc.
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Contact: Owen Zhang
Mobile： +86 182 1805 1155
Wechat: 182 1805 1155
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The high-quality recarburizer generally refers to the process of graphitization after high-temperature treatment. Under the high temperature condition of 3000 °C, the carbon molecular form changes from an irregular arrangement to a hexagonal uniform arrangement. This graphite structure is most easily decomposed in molten iron and steel.
Mainly used to increase the carbon content for metallurgical steelmaking and ductile iron casting.
1) The low-sulfur graphitization recarburizer has a high decomposition rate and a high absorption rate, and can reach more than 90%.
2) High carbon, low sulfur, low nitrogen, and extremely harmful components.
3) Adding graphite nucleus to molten steel and molten iron, more uniform and finer distribution in molten steel and molten iron, so that the performance is more excellent and stable.
The graphitized recarburizer is suitable for melting in an induction furnace, but it is not the same depending on the process requirements.
(1) Use low-sulfur graphitization recarburizer in medium-frequency electric furnace smelting, which can be added to the lower part of electric furnace at one time or two to three times according to the ratio or carbon equivalent requirement, and the recovery rate can reach more than 90%;
(2) If the amount of carbon is insufficient to adjust the carbon content, firstly clean the slag in the furnace, add the recarburizer, and heat the iron by electromagnetic stirring or electromagnetic stirring.
(3) Use graphitized recarburizer when tapping, put the recarburizer into the bag, or flush with the flow from the tapping trough, stir well after the molten iron, dissolve and absorb carbon as much as possible, carbon The recovery rate is around 90%.
Usually packing in 25kg/bag, 30Kg/bag or with jumboo bag, and also can be packaged according to customer requirements.
Calcined Petroleum Coke 1-10mm
Date: December 05, 2015
Volatile Matter: 0.74%
Fixed Carbon: 98.55%
High calorific power: 32.8 MJ/KG
Low calorific power: 32.78MJ/KG
The so-called recarburizer is to increase the content of carbon in the molten iron after it is added. Therefore, the fixed carbon content of the recarburizer must not be too low. Otherwise, to reach a certain carbon content, it is necessary to add a high carbon content. With more samples of recarburizer, this undoubtedly increases the amount of other unfavorable elements in the recarburizer, so that the ferrofluid can not obtain a better return.
Low levels of sulfur, nitrogen, and hydrogen are key to preventing the production of nitrogen holes in castings. This requires that the nitrogen content of the recharging agent be as low as possible. The other indicators of recarburizers, such as moisture, ash, and volatiles, the higher the amount of fixed breakage, so the high fixed carbon content of these harmful ingredients must not be high. For different smelting methods, furnace types, and sizes of smelting furnaces, it is also important to select an appropriate particle size of the carbon reductant, which can effectively increase the absorption rate and absorption rate of the recarburizer by the molten iron and avoid excessively small particles. Caused by oxidative damage to the breaker. The particle size is preferably: 100 kg furnace less than 10 mm, 500 kg furnace less than 15 mm, 1.5 tons furnace less than 20 mm, 20 tons furnace less than 30 mm. In the smelting of converters, when high-carbon steels are used, recarburizers containing little impurities are used.
The requirement for the recarburizer for top-blowing converter steelmaking is that the fixed carbon should be high, the content of ash, volatile matter and sulfur, phosphorus, nitrogen and other impurities should be low, and it should be dry, clean, and the grain size should be moderate. Its fixed carbon C> 97%, volatile matter <1.0%, S <0.5%, moisture <0.5%, particle size in l-5mm. The particle size is too fine to be easily burned, and it is too thick to float on the surface of the molten steel and is not easily absorbed by molten steel. The particle size of the induction furnace is 0.2-6mm, in which the steel and other ferrous metals have a particle size of 1.4-9.5mm, the high carbon steel requires low nitrogen, the particle size is 0.5-5mm, etc. The concrete need to be based on the specific furnace type smelting workpiece The details of the types and so on are specifically judged and selected.
Name: Owen Zhang
Mobile： 0086-182 1805 1155
Wechat: 182 1805 1155
Whatsapp: 0086-182 1805 1155
Add: Foshan, Guangdong, China