Problems and precautions in the use of SiC
(1) For continuous operation kilns and material channels, the voltage adjustment range is 0.7 ~ 2.0V (V refers to the voltage used at the initial stage of silicon carbide rod elements). The service life of silicon carbide components can be prolonged by pressurization adjustment. After using the silicon carbide rod electric heating element for a certain time, due to the increase of resistance value, the voltage needs to be increased to compensate for the loss of increased resistance. Therefore, the transformer needs to have a large voltage regulation range.
(2) In order to prolong the service life of silicon carbide rod elements and ensure safe use, multiple branches in series should be avoided. The wiring method of silicon carbide rod elements can adopt parallel, series, angular, star and other forms of wiring; However, parallel connection is superior to series connection. Parallel connection can adjust the factor of load imbalance, while multiple series connections aggravate the factor of imbalance and improve the working voltage.
(3) In order to ensure that each silicon carbide rod can be in a normal and ideal working state, the resistance value of the whole batch of silicon carbide rods shall be measured and classified before installation. Those with similar resistance values shall be installed in the same adjustment area to make their working resistance similar.
(4) If the current is too small, either the resistance is too large or the pin is not pressed properly. If there is no current, the silicon carbide rod electric heating element may be broken. Further inspection and replacement should be carried out. In order to check whether each silicon carbide rod electric heating element works well, the current can be measured one by one with a clamp ammeter during the power on test. In the same area, the current is required to be similar under the same voltage, and the deviation shall not exceed 10%. If the individual current is too large, it means that the resistance value is too small.
(5) In the use of glass industry, the incomplete silicon carbide rod fragments must be taken out, but generally, the silicon carbide rod will only break, not break. Silicon carbide rod fragments falling into the liquid glass will cause bubbles, which is due to the strong reduction of silicon carbide, which will react with the gas and glass components dissolved in the liquid glass.
(6) Due to the low volatile content in the general material channel, it has little impact on it. The kiln gas contains a lot of oxides such as sulfur, sodium and boron, which will react strongly with the silicon carbide rod and make the whole rod body fat and damaged within a few days. When using silicon carbide rod as heater, the material channel must be completely separated from the flame space of the working pool.
(7) During installation, special attention shall be paid not to allow unilateral stress. If necessary, heat-resistant steel pipe shall be used to cover the silicon carbide rod, gently push it in, then pull out the steel pipe sleeve, install the sheath and fix it. The silicon carbide rod electric heating element is brittle and easy to break, especially at the position with thread. It should be installed with special care and handled with care.
(8) The surface load density is inversely proportional to the furnace temperature. The higher the furnace temperature, the smaller the allowable surface load density; Overload use will cause overheating and decomposition of silicon carbide rod, resulting in falling off and burning loss of the surface of heating part. In order to ensure the service life of the element, the electric heating element shall not be used under overload conditions, and its value is generally controlled at 3 ~ 8W / cm2. The surface load density is reduced by adjusting the power load applied to the silicon carbide rod element. If smaller load and lower surface load density are adopted, the kiln can maintain a long service life despite the high temperature, which can be realized by changing the installation number of silicon carbide rod elements or changing the specification of elements to adjust the size of heating surface.
(9) In order to prevent the interaction between the silicon carbide rod electric heating element and the refractory of the superstructure, the pins of each element are insulated with ceramic fiber sleeve. The ceramic fiber sleeve not only plays the role of electrical insulation, but also plays the role of fixing the silicon carbide rod.
(10) The service life of silicon carbide heating elements is generally 3 ~ 4 months, most of which reach about 12 months. The silicon carbide rod is used in the kiln, and the operating temperature can reach 1450 ℃;. Under reducing atmosphere, the maximum operating temperature is 1500 ℃;.
(11) The silicon carbide rod used in the material channel is to prolong the service life of the silicon carbide rod heating element. The upper structure of the material channel can be improved, the material channel and the working pool can be separated by retaining bricks, and the material channel atmosphere can be strictly controlled.
(12) The aging speed of silicon carbide components is directly proportional to the service temperature. The higher the service temperature, the faster the aging and the shorter the service life. Reduce the influence of service temperature.
Contact Person: Mr. Yuwei, Chen