Silicon Carbide Abrasive

Specification

Due to its low natural content, silicon carbide is mainly man-made. A common method is to mix quartz sand with coke, utilize the silica and petroleum coke, add salt and wood chips, place it in an electric furnace, heat it to a high temperature of about 2000°C, and obtain silicon carbide powder after various chemical processes. 

Silicon carbide abrasive (SiC) has become an important abrasive due to its great hardness, but its application range exceeds general abrasives. For example, its high temperature resistance and thermal conductivity make it one of the first choice kiln furniture materials for tunnel kilns or shuttle kilns. Its electrical conductivity makes it an important electric heating element.

To prepare SiC products, you must first prepare SiC smelting blocks [or: SiC granules. Because they contain C and are super hard, SiC granules were once called: emery. But be careful: it has a different composition than natural emery (garnet). In industrial production, SiC smelting blocks usually use quartz, petroleum coke, etc. as raw materials, auxiliary recycled materials and waste materials, and are prepared through grinding and other processes into furnace materials with reasonable proportions and appropriate particle sizes (in order to adjust the permeability of the furnace materials, an appropriate amount needs to be added (from sawdust, when preparing green silicon carbide, an appropriate amount of salt is also added) and is prepared at high temperature. The thermal equipment for preparing SiC smelting blocks at high temperature is a special silicon carbide electric furnace.

Its structure consists of a furnace bottom, an end wall with electrodes on the inside, a removable side wall, and a furnace core body (full name: the energized heating element in the center of the electric furnace, generally Graphite powder or petroleum coke is installed in the center of the charge according to a certain shape and size, usually circular or rectangular. Its two ends are connected to electrodes) and other components. The firing method used in this electric furnace is commonly known as: buried powder firing. Heating starts as soon as it is powered on. The temperature of the furnace core is about 2500°C or even higher (2600~2700°C). SiC begins to be synthesized when the charge reaches 1450°C (but SiC is mainly formed at ≥1800°C), and CO is released.

However, SiC will decompose at ≥2600°C, but the decomposed Si will react with C in the charge to form SiC. Each group of electric furnaces is equipped with a set of transformers, but only a single electric furnace is powered during production in order to adjust the voltage according to the electrical load characteristics to basically maintain constant power. The high-power electric furnace needs to be heated for about 24 hours. After a power outage, the reaction to generate SiC is basically completed. After a period of cooling, the side walls can be removed, and then the charge is gradually taken out.

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