các silicon carbide rod begins to oxidize when used in the air to 800℃. When the temperature reaches 1000-1200℃, a protective silicon dioxide film is formed on the surface of the heating part. At 1200℃, cristobalite is formed. When the temperature rises above 1527℃, the protective film will be damaged and the oxidation rate will increase significantly, causing premature damage to the components.
Although the components oxidize extremely slowly during use, long-term operation will still cause the resistance to increase. This phenomenon is called aging.
The resistance of all silicon carbide heating elements will increase and age as the use time increases. When the resistance of the element increases to 3 times its original resistance, it is considered the end of its life. There are several factors that affect component aging and service life:
- working temperature
- Burned materials and the harmful substances they produce
- Component surface load (W/CM square)
- How to connect electrical appliances
- Furnace atmosphere
- Temperature control method
- Mode of work (continuous or indirect)
- Usage habits
The test method is to measure the voltage and current when the silicon carbide rod is energized and heated to a high temperature of 1050℃, and the resistance is obtained using Ohm’s law.
Under a clean oxidizing atmosphere of 1000°C, it can be used for 1 year normally and 3 months at high temperatures.