Properties and maintenance of silicon carbon rods

(1) Silicon-carbon rod (SiC) electric heating element is a rod-shaped non-metal high-temperature electric heating element made of green high-purity hexagonal silicon carbide as the main raw material, processed into embryos, siliconized at high temperature, and recrystallized at a high temperature of 2200 ° C. The surface temperature of the rod can reach 1450 ° C. When the surface temperature of the rod exceeds 1500 ° C, the aging speed of the rod increases and it is easy to burn. Under reasonable conditions of use, the continuous use of silicon carbon rods for more than 2000 hours, in addition to the inherent quality difference In addition, it is also related to the surface load (the larger the surface load is, the shorter the service life) during the use of the silicon carbon rod, the ambient atmosphere, the heating method (intermittent heating or continuous heating), and the series-parallel method during the use of the component. And other factors.

(2) Silicon carbide rods are hard and brittle, with a small expansion coefficient, good resistance to rapid cooling and heating, not easy to deform, good chemical stability, extremely strong acid resistance, and do not react with strong acids.

(3) The resistance value of the silicon carbon rod changes with the change of the component temperature, because the silicon carbon rod is a non-linear resistor. From room temperature to about 900 degrees, the resistance value changes from large to small, and the resistance value of silicon carbon rods above 900 turns from small to large. That is to say, the resistance value of silicon carbon rods is the smallest at about 900 degrees. That is, the resistance value at this temperature.

 (4) Silicon carbon rods are hard and brittle, so special care should be taken during loading and unloading.

 (5) The silicon carbon rods should be stored in a dry place to prevent the aluminum-plated ends from getting wet and deteriorating.

 (6) Molten KOH, NaOH, Na2CO3 and K2CO3 decompose SiC at the red hot temperature. The contact between silicon carbon rod and alkali, alkaline earth metal, sulfate, boride, etc. will be corroded, and they should be strictly prohibited from contacting silicon carbon rod.

 (7) The wiring of the silicon carbon rod should be in close contact with the white aluminum head at the cold end of the rod to avoid ignition.

(8) Silicon carbon rods react with Cl2 at 600 ° C, and react with water vapor at 1300-1400 ° C. Silicon carbon rods are not oxidized below 1000 ° C, and significantly oxidized at 1350 ° C, at 1350- A SiO2 protective film is formed between 1500 ° C and attached to the surface of the silicon carbon rod, preventing SiC from continuing to oxidize.

 (9) The resistance value of silicon carbon rods increases with the use of silicon carbon rods. The reaction is as follows:

SiC + 2O2 = SiO2 + CO2

SiC + 4H2O = SiO2 + 4H2 + CO2

The more the content of SiO2, the greater the resistance value of silicon carbon rods. Therefore, the new and old silicon molybdenum rods cannot be mixed, otherwise the resistance value will be unbalanced, which is very unfavorable to the temperature field and the service life of silicon carbon rods.

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