Carburizers are divided into common carburizers and graphitized carburizers.
Common carburizers are divided into calcined petroleum coke and calcined coal. Calcined petroleum coke is made from delayed coke of oil refinery calcined at 1400 ℃, and calcined coal carburizer is made from high-quality anthracite calcined at 1200 ℃.
Graphitized carburizer is made from calcined petroleum coke by graphitization at high temperature.
Performance characteristics of carburizing agent
The carburizing agent is a non-metallic material with a melting point of about 1200 ℃ ~1300 ℃. The high-quality carburizing agent has stable performance, fast absorption speed and high absorption rate.
Action principle of carburizing agent
Carburizing agent mainly plays the role of increasing carbon in steelmaking and casting.
When the cupola is used to melt cast iron, the molten iron passes through the hot bottom coke in the form of droplets, and the effect of carburization is good. When smelting synthetic cast iron (scrap + carburizing agent) in induction furnace, carburizing agent is essential. Replacing pig iron with carburizing agent can reduce the "harmful heredity" in pig iron and improve the metallurgical quality of molten iron.
According to different smelting processes, carburizing agents can increase the mechanical strength of steel and castings. The carburizing agent can promote the nucleation ability of graphite in molten iron, increase the amount of nodular graphite in nodular cast iron, improve the microstructure of gray cast iron, and improve the strength of gray cast iron, so that the carbon element appears as A-type graphite in the casting to obtain fine and uniform graphite, and promote the spheroidization and inoculation process.
There are many kinds of raw materials and different production processes for carburizers. It is not said in the market that graphite powder is used for pressing and forming. This production method needs to add too much binder for forming, and the carbon content generally can not meet the requirements of high-quality carburizing agent. The pressed graphite powder is a solid block without multi pore structure, so its absorption rate and absorption rate are not as good as those of calcined and calcined carburizers. High quality carburizing agent generally refers to the carburizing agent after graphitization. Under high temperature conditions, the arrangement of carbon atoms takes on the microscopic form of graphite, so it is called graphitization. Graphitization can reduce the content of carbon in the carburizing agent, increase the carbon content of the carburizing agent and reduce the sulfur content.
When the carburizing agent is used in casting, it can greatly increase the amount of scrap steel, reduce the amount of pig iron or not use pig iron. Most of the carburizers are suitable for electric furnace smelting, and a small number of carburizers with particularly fast absorption speed are used for cupola. For the feeding method of electric furnace smelting, the carburizing agent shall be added together with scrap and other furnace materials, and a small amount can be added on the surface of molten iron. However, it is necessary to avoid feeding into molten iron in large quantities, so as to prevent too much oxidation and the situation that the carburization effect is not obvious and the carbon content of castings is not enough. The addition amount of carburizing agent shall be determined according to the proportion of other raw materials and the carbon content. For different types of cast iron, different types of carburizing agents shall be selected according to needs. Features of carburizing agent: pure carbon containing graphitized material is selected to reduce excessive impurities in pig iron. Proper selection of carburizing agent can reduce the production cost of castings.
