Application Methods of Silicon Carbide in Metallurgy

Silicon carbide is widely used in the metallurgical industry due to its stable chemical properties and high melting point.

There are different types of silicon carbide, and the best content for casting is about 90%. One is high-purity material, which has high hardness and high melting point. Low-purity material may have too many impurities. When using materials in an electric furnace, it is best to have finer particles, 0.5-3 mm, so that they are easy to melt and absorb. When used in a cupola furnace, the particles should be larger to avoid being flushed out by strong airflow. At high temperatures, silicon carbide decomposes into carbon and silicon ions. Their chemical property is to react with oxygen first, so they can reduce the oxidation of molten iron. Then they enter the molten iron respectively and first become the crystallization core of graphite. Both carbon and silicon have a strong nurturing effect, so they are very helpful for the smelting of electric furnaces and low-carbon molten silicon iron.

Silicon carbide is more widely used abroad, and this substance is added to both electric furnaces and cupola furnaces. Because its melting point is very high, around 2700 degrees, it is impossible to have such a high temperature in our ordinary casting furnaces. That is, at our casting and melting temperatures, the molten state gradually decomposes and diffuses when silicon carbide is dissolved. Comparatively It is slow, so it should be added earlier than other alloys in the furnace. It is usually added when the charge is smelted to one-third to half of the furnace, allowing it to have sufficient temperature and time conditions to decompose.

In the past two years, silicon carbide has been widely used in casting production. Especially in smelting, it is very beneficial to increase the graphite core, increase the number of graphite nodules in ductile iron, and improve the graphite morphology of gray iron. The effect is that after adding silicon carbide particle size sand, the graphite shape becomes thicker and shorter, the distance is larger, the number of eutectic clusters is increased, the relative strength and relative hardness of cast iron are improved, the degree of supercooling of molten iron after incubation is reduced, and silicon carbide is used instead of ferrosilicon It is beneficial to improve the quality of induction furnace cast iron.