The Use Matters Of Silicon Carbide For Casting

Silicon carbide is added when cast iron is smelted. For gray cast iron, due to the pre-inoculation effect of non-equilibrium graphite, the temperature at which a large number of eutectic clusters are formed and grown can be increased (reduce the relative supercooling degree), which is beneficial to the formation of A-type graphite; The increase in the number of crystal nuclei makes the flake graphite finer, improves the degree of graphitization and reduces the tendency of white mouth, thereby improving the mechanical properties.

In terms of gray iron, ductile iron and malleable iron, SiC is used to reduce the content of FeO and MnO in the slag through the reaction of SiC+FeO=Si+Fe+CO, thereby purifying the molten iron.

Due to the high melting point of silicon carbide, the timing of adding silicon carbide is the key. If it is added too late, the silicon carbide will not be fully melted and diffused, and the unmelted silicon carbide will exist in the molten iron in the form of particles. After pouring, slag holes will be formed; if the addition time is too long, the nucleation formed by silicon carbide will gradually disappear after the molten iron is smelted for a long time, and it can only play a simple role of increasing silicon. Therefore, it is suggested that the best time to add silicon carbide is when 1/3 of the charge is melted in the intermediate frequency furnace, and the charge has been dissolved. With the stirring of the molten iron, the diffusion effect of silicon carbide will be better.

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