Silicon carbide rods are non - metallic electro - thermal elements. They are made from high - purity green hexagonal silicon carbide as the main raw material and are recrystallized at a high temperature of 2200°C. The normal operating temperature can reach 1450°C. Under reasonable use conditions, they can be used continuously for more than 2000 hours.
When used in the air, no protective atmosphere is required. They are suitable for various electric furnaces and kilns.
Due to their high operating temperature and good chemical stability, when silicon carbide rods are equipped with an automated power supply system, an accurate constant temperature can be obtained. They can also automatically adjust the temperature according to the curve as required by the actual production process. They have now been widely applied in fields such as national defense, machinery, metallurgy, light industry and chemical industry, ceramics, semiconductors, analysis and testing, and scientific research, and are used as electric heating elements for various electric furnaces and kilns, including tunnel kilns, roller - hearth kilns, glass kilns, vacuum furnaces, muffle furnaces, smelting furnaces, and various heating equipment. Heating with silicon carbide rods is both convenient and safe and reliable.
These elements are hard and brittle in texture, with a small coefficient of expansion. They can withstand rapid cooling and heating, are not prone to high - temperature deformation, have good chemical stability, and are extremely resistant to acids, showing no reaction with strong acids. However, their alkali - resistance is relatively poor, and they can be corroded and decomposed at high temperatures. Chlorine gas can decompose the elements, and hydrogen and ammonia gases have different degrees of corrosive effects. If used in air and water vapor for a long time, the elements will age slowly, with an increase in the silica content and an increase in resistance value due to chemical reactions.
The resistance value of silicon carbide rods changes with the change of the element temperature because the element is a non - linear resistor. From room temperature to 850 ± 50°C, the resistance decreases, and above 850 ± 50°C, it increases again. That is to say, the temperature coefficient of resistance of the element has both negative and positive value stages. The resistance marked at one end of the rod is measured at 1050 ± 50°C in accordance with the ministry - issued standards, which is convenient for matching during installation.
