What is high temperature metal cleaning and annealing of thermocouple _ instrument

Often dealing with a platinum rhodium thermocouple friends all know that platinum rhodium thermocouple is also known as high temperature thermocouple, precious metals for high temperature metal thermocouple is a frequently used technology that is high temperature metal cleaning and annealing of thermocouple. Clean by washing to remove hot electrode surface dirt, organic matter and oxide and improve thermoelectric properties to prolong service life. ( 1) Pickling is to use acid oxidation ability to remove organic matter on the surface of the thermocouple, general metal impurity and their oxides. The thermocouple wire ( Platinum rhodium 10 - Platinum and platinum rhodium 30 - Platinum rhodium thermocouple wire 6) In garden circle about 80 mm in diameter, into the beaker with distillation water flushing, first remove dust and then pour into 30 - 50% ( According to the volume ratio) Chemical pure hydrochloric acid or nitric acid for 1 h 15 min or boiled, add the distilling the water washing several times. ( 2) Borax wash with borax ( na2b4o7·10h2o) Remove attached to the electrode surface, and the reducibility of refractory metal impurity in acid and its oxide, expand the hot electrode, the two heat of reference electrode were hanging from the wash rack, two hot electrode Angle of about 30 ℃, adjust current, make the hot electrode blocks of borax heated to 1100 ℃ ~ 1150 ℃ to touch the hot electrode is reference, borax melt into drops, suitable electrode, several cleaning of metallic luster, cool to room temperature, and then set into a 80 mm diameter circle of garden in distilling the water to boil. Annealing eliminated by annealing heat electrode internal stress, improve the microstructure and improve the stability. ( 3) By annealing in the air, hang the thermocouple thermal electrode annealing on the shelf, slowly adjust current, make the hot electrode at a certain temperature to maintain a certain period of time, and then slowly reduced to zero, the input current electricity annealing makes longitudinal heated evenly, attached to the surface of low melting point metal and impurities can be volatile, but the radial heat affected by the surrounding air, inconsistent, cooling speed to produce thermal stress. ( 4) In the furnace annealing, standard platinum rhodium - 10 Platinum thermocouple and standard platinum rhodium - 30 Platinum rhodium thermocouple 6 after electrify annealing, even in a furnace, annealing, hot after the electrode wear insulating tube into the special of the uniform temperature field of annealing furnace, in the 1100-20 ℃ temperature keep a period of time, and then with the furnace cooling, it makes the radial heat evenly, eliminate internal stress caused wear tube, increase the stability of pyroelectricity.