Factors affecting heating power of vacuum furnace

The heating power of the vacuum furnace will be affected by various factors, such as the recalibration of the heating power of the vacuum furnace with the increase of the service time of the furnace, the decrease of the thermal resistance of the heat insulation screen, the increase of the power due to the volatilization of the electric heating elements and the increase of the resistance. The maintenance of the heat shield plays the role of heat insulation and heat preservation in the vacuum furnace, sometimes it also serves as the structural foundation of the fixed heater.

Generally, there are four types of heat shield: all metal heat shield, sandwich heat shield, graphite felt heat shield and mixed felt heat shield. The key points of different heat shields should be mastered during maintenance. If the standard can not be reached in the low temperature experiment, it depends on the same temperature reduction speed. If the temperature drops slowly, it is necessary to check whether there is no drying treatment in the working room. Before the experiment, the studio needs to dry and place too many test articles, so that the air inside cannot be recycled; if not, it needs to check the equipment in the refrigeration system, which needs professional personnel to check.

The automatic control system of vacuum furnace needs to detect the vacuum degree, temperature parameter, process operation parameter and state of degassing chamber, heating chamber and cooling chamber, and ensure the control output required by process temperature control of each chamber. There are mainly the following:

1) Detection parameters: temperature values of three temperature detection points in degassing chamber, heating chamber and cooling chamber, pressure value in vacuum furnace, vacuum degree in furnace and other parameters;

2) Detection status: over temperature alarm, over pressure alarm and water shortage alarm of degassing chamber, heating chamber and cooling chamber;

3) Heating setting: adjust the heating power supply to change the temperature in the furnace by controlling the operation of the temperature control meter. The temperature of each room is sampled by thermocouple, and the temperature of furnace body tested is compared with the temperature value required by the process, and the deviation is calculated. The temperature control meter controls the heating current of heating power panel according to a certain rule, so as to control the temperature.

4) Control output: control the conveying mechanism to transport the charging car between the degassing chamber, heating chamber and cooling chamber, and control the action of diffusion pump, roots pump, mechanical pump, main valve, coarse pumping valve, front valve and other valves to achieve the required vacuum environment.

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