In recent years, with the continuous development of casting technology, more and more cast iron manufacturers use induction furnace production of synthetic iron technology to improve product quality, reduce costs and improve business efficiency. In the continuous development of synthetic cast iron technology, scrap added more and more, from the initial 30%, has now increased to 80%. Due to the increase in the amount of scrap added to the cast iron when the furnace is melted, the Carburant content in the molten iron is reduced. Therefore, the Carburant reduction technology must be adopted to ensure the quality of smelting and improve the composition and performance of the cast iron.
1. Classification of Carburant
Cast iron commonly used Carburantizer is a Carburantaceous material, the main component is Carburant. Carburantaceous materials are mainly graphite and amorphous Carburant. Graphite is a hexagonal lamellar crystal. The Carburant atoms in the graphite crystal are arranged in a layered form, and the cohesive bonds are covalently bonded to the same layer atoms. The binding force between the layers is between the layers and the polar bonds Combined, the combination of weak. Therefore, the graphite is easily delaminated, the strength is extremely low. Since the graphite crystal has such a structural feature, it is easy to grow into a sheet-like structure when it is grown in the molten iron. Amorphous Carburant is also hexagonal lamellar crystal, and graphite is different from the hexagonal arrangement is not complete, slightly larger interval between layers.
According to the Carburant structure of Carburant in the Carburant, Carburant agent can be divided into amorphous and crystalline state. According to the Carburant in the presence of Carburant in the form, divided into graphite Carburant and non-graphite Carburant agent. In addition, silicon carbide (SiC) has a hexagonal structure similar to that of graphite, and is also classified as a graphite-Carburantized agent. The graphite Carburant (SiC) has a hexagonal structure similar to that of graphite. A special form. Non-graphite Carburant agent mainly asphalt coke, calcined petroleum coke, coke pressed material, calcined anthracite and so on.
2. Carburant principle
Carburant dioxide exists in the form of Carburant, melting temperature of 3727 ℃, can not melt at the temperature of the molten iron, so the Carburant in the Carburant by dissolving and diffusion in two ways dissolved in molten iron. When the wc = 1.0% of the molten iron, the graphite in the graphite can be dissolved directly in the molten iron. Rather than the direct phenomenon of graphite Carburant does not exist, but with the passage of time, Carburant in the molten iron gradually spread and dissolved. Therefore, for the furnace smelting synthetic cast iron by Carburant, the use of graphite by Carburant increased Carburant speed was significantly higher than non-graphite Carburant agent.
It is shown that the dissolution of Carburant in the molten iron is affected by the liquid boundary layer of the solid particles. The results obtained with coke and coal particles were compared with those obtained by graphite. It was found that the diffusion and dissolution rate of graphite Carburantizer in iron liquid was much faster than that of coke and coal particles. Electron microscopy was used to observe the partially dissolved coke and coal particles. It was found that a thin layer of viscous gray layer was formed on the surface of the sample, which was the main reason for its diffusion solubility in molten iron.
3. Selection of Carburant agent
For the furnace melting, the core of Carburant enhancement technology is the use of high-quality Carburant agent. Reference to the relevant information, that the selected Carburant agent should have the following characteristics:
(1) the use of high temperature graphitization treatment of Carburant agent, only after high temperature treatment, the Carburant atoms can be arranged from the original disordered arrangement of flakes, flake graphite can become the best core of graphite nucleation, to promote graphite The
(2) good Carburant agent sulfur is very low, wS <0.03% is an important indicator.
(3) the porosity of the Carburant agent is also important for the Carburant effect and the Carburant absorption rate. Therefore, the high temperature graphitized petroleum coke is more effective than the electrode graphite.