The temperature control of the chamber atmosphere furnace is to change the heating power of the furnace according to the deviation between the actual temperature and the set temperature, so that the furnace temperature is within the set temperature range to meet the heating process requirements. The size of the heating power determines the temperature of the furnace and the speed of heating, and the stability of the heating power determines the stability of the temperature of the resistance furnace.

There are many ways to change the heating power, common are positional type, thyristor regulator and electric furnace transformer control mode, etc., which heating method is determined by the structure, use and temperature of the furnace.

No matter which control method is adopted, the control process of the chamber atmosphere furnace is basically the same, always including temperature measurement, temperature controller, heating drive components, electric heating elements and auxiliary circuits.

(1) Temperature measurement of chamber atmosphere furnace. Temperature measurement of resistance furnace usually uses thermocouple temperature sensor and photoelectric pyrometer, generally using thermocouple for contact side measurement, when the temperature is high, it must be selected radiometric photoelectric thermometer for non-contact measurement.

(2) Temperature controller. The temperature controller is also commonly known as the temperature control instrument, and its function is to display the temperature signal sent by the temperature sensor or transmitter on the one hand; On the other hand, the measured temperature value is compared with the set value, and the temperature control signal is output. In the temperature control of resistance furnace, if the control accuracy requirements are not high, an analog bit-controlled temperature controller can be used, otherwise a digital intelligent temperature control instrument is used, and the latter is currently widely used.

(3) Chamber type atmosphere furnace heating drive parts. The heating drive component plays the role of power amplification, converts the change of temperature control signal into the change of heating power, heats the electric heating element, and achieves the purpose of changing the temperature of the furnace. Heating drive components are one of the main factors affecting the temperature control method, commonly used contactors, solid state relays, thyristor regulators and transformers.

(4) Electric heating element. Electric heating elements are components that convert electrical energy into heat energy, mainly including non-metal, metal alloy and pure metal.

(5) Chamber type atmosphere furnace auxiliary circuit. Auxiliary circuit refers to a circuit other than the heating main circuit, including the action of auxiliary devices, the indication of working status, and safety interlock protection.

How to maintain the chamber atmosphere furnace:

1. In order to measure accurately, the DC potentiometer is used every year to calibrate the temperature meter of the XMT type temperature controller to avoid causing large errors.

2. Regularly check whether the hot wire of each part of the box atmosphere furnace is loose, whether the contacts of the AC contactor are good, and the fault should be repaired in time.

3. The instrument should be placed in a dry and ventilated, non-corrosive gas place, the working environment temperature is 10-50 °C, and the relative temperature is not more than 85%.

4. Silicon carbon rod type furnace, after the silicon carbon rod is found to be damaged, the new silicon carbon rod with the same specification and similar resistance value should be replaced. When replacing, first remove the protective cover at both ends and the silicon carbon rod chuck, and then take out the damaged silicon carbon rod, because the silicon carbon rod is easy to break, be careful when installing, the outer part of the exposed furnace shell at both ends should be equal, and the chuck must be tightened so that it has good contact with the silicon carbon rod. If the chuck is severely oxidized, it should be replaced with a new one. The gaps in the mounting holes at both ends of the silicon carbon rod should be plugged with asbestos rope.

5. The furnace temperature of the chamber atmosphere furnace shall not exceed the high working temperature. Silicon carbon rods are allowed to work continuously for 4 hours at high temperatures. After the chamber furnace has been used for a long time, if the clockwise direction of the heating power adjustment button is adjusted to the large position, the heating current still cannot go up. If it is far from the rated value and does not reach the required heating power, the silicon carbon rod is aging. At this time, the silicon carbon rods connected in series can be changed to parallel and can still be used. When changing the connection, it is not necessary to disassemble the silicon carbon rod, just change the connection, and after changing the connection, pay attention to slowly adjusting the heating power adjustment button when using, and the heating current value shall not exceed the rated value.