Welding of thermocouple materials

    The commonly used welding methods for thermocouple materials include gas welding, carbon arc and mercury arc welding.

    1. Gas welding

    Gas welding uses a flame combusted by a mixed gas of acetylene and oxygen (or hydrogen and oxygen), which needs to be adjusted to a neutral flame with a slight excess of acetylene before use. When welding, heat the contact at a position 1.2~2.0 mm outside the flame core; during operation, the flame rises and falls from time to time and cannot always stay at one point; once the two metal wires are fused, immediately remove the flame and cool down. A spherical joint.

    2. Carbon arc welding

    Carbon arc welding can use AC or DC arc welding, and DC is better; under DC, the thermocouple wire is used as the positive electrode and the carbon electrode is used as the negative electrode. When the thermocouple wire is just melted, immediately pull the carbon electrode apart to interrupt the arc, and the molten metal will form a spherical joint. Materials that are more susceptible to oxidation can be welded under argon protection.

    3. Mercury arc welding

    Mercury arc welding is suitable for welding thermocouple wires with a wire diameter of 0.3~1.5 mm. AC or DC can be used, and the voltage is 20~60 V. When DC power is used, the thermocouple wire must be connected to the positive pole and the cup containing mercury to the negative pole (not connected Otherwise, the mercury will evaporate violently, which is harmful to the human body. A layer of transformer oil can be applied to the surface of the mercury to prevent oxidation of the solder joints and evaporation of the mercury); during welding, touch the end of the thermocouple wire to the surface of the mercury and raise it slightly to make An arc is generated; the thermocouple wire melts quickly. At this time, the thermocouple wire is lifted to extinguish the arc. After condensation, a spherical joint is formed. The crystal structure of the welding joint is fine and dense, with less pores and impurities, and the welding quality is high.

(Huiputech)