Casting carburizer actually refers to graphitized columnar carburizer, bar carburizer is mainly used in casting enterprises, the production of ordinary cast iron, gray iron more.
This kind of product and the calcined petroleum JiaoZeng carbon agent also has certain market competition, especially in the casting, the steel industry, from market feedback, the last two years from the beginning of the manufacturer to try to use a cylindrical recarburizer to use two years have been rising, many manufacturers reaction under the premise of the use effect is good, can effectively reduce the production cost, get the favour of many foundries.
Foundry carburizer manufacturers recommend that you should choose a low nitrogen carburizer
The usual nitrogen mass fraction in cast iron is less than 100 PPM.If the nitrogen content exceeds this concentration (150-200 PPM or higher), the casting is prone to cracking, shrinkage or porosity defects, and the thick-walled casting is more likely to occur.This is due to the increase of scrap ratio, to increase the amount of carburizer.Coke carbonizer, especially asphalt coke contains a lot of nitrogen.The nitrogen content of electrode graphite is less than 0.1% or very trace, while the nitrogen content of asphalt coke is about 0.6%.If a 2% carburizer with a mass fraction of 0.6% nitrogen is added, this alone increases the nitrogen with a mass fraction of 120 PPM.A large amount of nitrogen is not only easy to produce casting defects, but also can promote the pearlite compact, ferrite hardening, and strongly improve the strength.
Method of adding casting carburizer
The stirring of iron liquid can promote increasing carbon, so the medium frequency induction furnace with weak stirring force and the power frequency induction furnace with strong stirring force are compared, increasing carbon is relatively more difficult, so the medium frequency induction furnace has increasing carbon can not keep up with the melting speed of metal charge possibility.
Even if the stirring force is strong power frequency induction furnace, increasing carbon operation can not be ignored.This is because, as can be seen from the schematic diagram of induction furnace smelting, there is a separate stirred iron flow in the induction furnace, and there is a dead corner near the furnace wall at its boundary.The graphite masses that stay on the furnace wall cannot be melted into molten iron without excessive heating and long-term molten iron insulation.Excessive heating of molten iron and long-term heat preservation will increase the supercooling degree of molten iron and increase the tendency of cast iron whitening.In addition, for an intermediate frequency induction furnace that generates a strong induction current near the furnace wall, if molten iron is drilled between graphite masses attached to the furnace wall, the metal drilled will be melted during the next furnace smelting, leading to erosion and damage to the furnace wall.Therefore, more attention should be paid to the addition of carburizer when the ratio of scrap steel is high and the amount of carburizer is large.
The addition time of carburizer cannot be ignored.If the addition time of the carburizer is too early, it is easy to make it adhere to the furnace bottom nearby, and attached to the furnace wall of the carburizer is not easy to be melted into the liquid iron.On the contrary, if the addition time is too late, the opportunity to increase carbon will be lost, resulting in slow melting and heating time.Not only does this delay the time for chemical composition analysis and adjustment, but it may also cause harm due to excessive heating.Therefore, add carbon agent or in the process of adding metal charge to add a little bit.