The heating characteristics of silicon carbide
Study on the electrical characteristic of silicon carbide is the relationship between the resistance of clear silicon carbide with temperature changes, the regulation of fever. Silicon carbide is different from the structure of silicon carbide semiconductor materials, metal, its resistance value is affected by the temperature change is relatively large. Under normal temperature, the resistance value is higher, the temperature is increased but below 600 degrees Celsius, the resistance coefficient is negative; about 600 degrees Celsius, the resistance value is minimum; the temperature increases, the resistance coefficient becomes positive, and the resistance value increases. Therefore, to maintain a certain condition in the input voltage, cold resistance, input power, self protection function, ensure the cold state of silicon carbide heating speed is not too fast; at high temperature, the resistance increases with the temperature, power and input resistance is inversely proportional to the change of silicon carbide with self the effect of temperature stability.
2. heating characteristics
The silicon carbide surface load equal to the heating power divided by the surface area of the heating. The surface load is large, the oxidation rate becomes faster, shorten the service life, therefore, in the electric heating to be strictly controlled within the allowable load range, avoid overload. According to the surface load of the furnace construction, atmosphere and temperature is the key element of the right choice to reach the highest life elements, generally use silicon carbide limit surface load 1/2-1/3.
The heating characteristics of silicon carbide is in constant temperature condition, the resistance value change over time, the research purpose is to determine the heating characteristics of silicon carbide life related to those factors, to determine how to prolong its service life. Silicon carbide heating characteristics at certain temperature, the heating time is longer, the oxidation conditions, the higher the temperature of silicon oxide generated faster increase in resistance increases, silicon carbide power becomes small; when the resistance value is increased to 3-4 times the original value, its power is very low, the silicon carbide on the failure. Aluminum refining equipment, electric furnace temperature at 730 degrees Celsius, siliconit temperature at about 1000 DEG C, the silicon carbide life of about half a year. The new silicon carbide work, surface temperature difference at 60 DEG C, the temperature difference along with the aging and change, may reach a maximum of 200 degrees. Globar before use, should be measured resistance value, with resistance of silicon carbide, should try to make the resistance value of each phase matching, the resistance of silicon carbide furnace in the same value in difference should not be greater than 2% for the best. A plurality of silicon carbide is used to parallel. If the series easily lead to support a rapid increase in resistance of silicon carbide, shorten the life of. The silicon carbide rod used for a period of time, the mountain on the resistance increased, the need to improve the voltage, in order to achieve the original power, which compensates for the increase in resistance loss, so the input voltage to a certain range; for the continuous operation of the furnace, voltage adjustment range is 0.7-2.5V (V is the voltage of silicon carbide components early) with the transformer with. The service life of the silicon carbide element can be prolonged by adjusting the voltage. If the control system adopts the automatic voltage regulator, this problem can be solved effectively.