Silicon carbide crystallization

When silicon carbide manufacturers smelt different grades of ferrosilicon, or when the properties of the charge used change, the selected secondary voltage should also be different, so as to ensure that the power and current distribution in the submerged arc furnace meet the smelting requirements. For example, when smelting 45 ferrosilicon, because there are more iron filings in the charge, the conductivity of the charge is stronger than that of 75 ferrosilicon. Therefore, when smelting 45 ferrosilicon in an submerged arc furnace with the same capacity, the secondary voltage lower than that of smelting 75 ferrosilicon should be used. Therefore, when selecting the secondary voltage, not only the difference of smelting temperature, but also the difference of charge conductivity are considered. Transparency varies with its purity. Silicon carbide crystal structure is divided into hexagonal or rhombohedral α- SiC and cube β- SiC (cubic silicon carbide). α- SiC has many different variants due to the different stacking sequences of carbon and silicon atoms in its crystal structure, and more than 70 kinds have been found. β- SiC changes to when the temperature is above 2100 ℃ α- SiC。 The industrial production method of silicon carbide is to refine high-quality quartz sand and petroleum coke in a resistance furnace.

The refined silicon carbide block is made into products with various particle sizes through crushing, acid-base washing, magnetic separation, screening or water separation. Silicon carbide has two common bases, black silicon carbide and green silicon carbide α- SiC。 Black silicon carbide contains about 95% SiC, and its toughness is higher than that of green silicon carbide. It is mostly used to process materials with low tensile strength, such as glass, ceramics, stone, refractory, cast iron and non-ferrous metals. Green silicon carbide contains more than 97% SiC and has good self sharpening property. It is mostly used for processing cemented carbide, titanium alloy and optical glass. It is also used for honing cylinder sleeves and fine grinding high-speed steel tools.