In order to eliminate the internal stress of thermocouple and make its metallographic more regular, the thermocouple should be annealed before use. There are usually two methods of thermocouple annealing, which can be divided into electrified annealing and furnace annealing. The following is a detailed introduction to how to annealing:
1. Electrified annealing
Power on annealing is to hang the thermoelectric electrode on the bracket according to borax cleaning method, adjust the current slowly, keep the thermal electrode at a certain temperature for a certain time, and then slowly reduce the input current to low. The annealing temperature and time of all kinds of thermocouples are regulated.
The advantages of electrified annealing are simple equipment, convenient operation, uniform heating along the hot electrode, and easy volatilization of surface impurities. The disadvantage is that the radial temperature of the thermoelectric electrode is affected by the surrounding air, and the surface metal is easy to volatilize, which makes the composition change, but it can still meet the requirements of industrial thermocouple.
2. Annealing in furnace
Annealing in furnace is to put the thermoelectric electrode into the uniform temperature field of the special annealing furnace by putting it on the insulating tube, holding for a certain time at the specified temperature, and then cooling with the furnace. Its advantage is that the thermoelectric electrode is evenly heated in radial direction and can eliminate the stress caused by pipe penetration. The disadvantage is uneven heating along the longitudinal direction of the thermal electrode. The two annealing methods have their own advantages and disadvantages. Good results can be obtained if they are used successively.
On 2018-08-08 11:45:46
