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Performance and Application of Silicon Carbide Electric Heating Material
May 21, 2018

The using temperature of silicon carbide heating elements is generally about 1500°C. The normal continuous service life is generally more than 2000 hours with the features of high surface load density, rapid temperature rise, and high thermal efficiency. Comparing to resistance alloys (nickel-chromium alloys, iron-chromium alloys), the use of silicon carbide electric heating elements in high temperature and power load, oxidation resistance is better and there is no problem of high temperature softening; compared with high melting point rare metals, the raw materials source of silicon carbide electric heating element is more extensive and the price is cheaper; compared with other non-metallic electric heating materials, the silicon carbide electric heating element can work under a variety of atmospheres and there are no restrictions when used. In addition there are several advantages:

1. Low coefficient of thermal expansion, approximately 4.5x106/°C at 1000°C

2. High thermal conductivity, 10-14w/m°C

3. The use of high temperature, long life

4. Preparation of materials, raw materials are widely available

Therefore, the silicon carbide electric heating element has superior conditions for use temperature and economic value compared with other high-temperature electric heating elements. Therefore, the  application is very wide and occupies a major market share in high-temperature furnaces. At present, it has been widely used in various electric kilns with furnace temperatures of 800-1600°C (eg metallurgy, chemical industry, metal heat treatment, sintering of powder metallurgy, heating of glass kilns in the glass industry), and in the electronics industry, the chemical industry and experimental equipment are also widely used.

The electrothermal characteristics of the silicon carbide heating element is different from that of the general metal heating element. The element is taken when the room temperature reach to 900°C and as the temperature rises, the resistance increases to a greater extent, showing a positive temperature coefficient of resistance. In the meantime the silicon carbide heating elements will gradually oxidize to SiO2 in an oxidizing atmosphere, and as the resistance gradually increases, the SiC heating elements will age.

At the initial stage of use of the heating element, a dense oxide film was not formed on the surface, the oxidation reaction was rapid, and the increase in resistance was particularly significant. As the reaction progressed, a dense oxide film was formed on the surface of the silicon carbide heating element and then entered the resistance stable area. After that, as the time increases, the conductive layer gradually decreases, and the insulating layer gradually increases. When the resistance value reaches about 3 times of the initial resistance value in the general case, the heating element has serious uneven heat generation, and then the silicon carbide heating element of the magnet must be replaced in time.

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