Tungsten-Rhenium Thermocouples in Air Thermal Emf Stability Test

In order to be consistent with the actual application , the present study, major domestic and foreign manufacturers to provide wire tungsten rhenium thermocouple wire as an object of study, the positive and negative growth 45cm thermocouple match between the poles of high purity Al2O3 insulated pipe insulation, work side exposed to the air . Experiment, the tungsten rhenium thermocouple placed in the working end of the furnace body temperature zone, the reference terminal is at room temperature , which fluctuated within ± 5 ℃ . With high-precision digital voltmeter thermopower of the thermocouple and the bulk resistance for real-time detection , in order to examine the stability of the thermocouple at different temperature variation and high purity platinum wire as reference electrode tungsten- rhenium thermocouples negative comparison the relative stability of the pole , while using electron probe microanalysis techniques and metallographic studies thermocouple thermoelectric potential reason for the change .

Tungsten- rhenium thermocouple thermoelectric EMF and body resistance R in the oxidation process variation with time t showed significant mutagenicity . Very stable prior to the mutation occurs ; thermoelectric potential and volume resistivity at the same temperature mutated . Its direction varies with temperature : 800 ℃ and 900 ℃ , the thermoelectric power is drift occurs ; 1000 ℃ negative drift occurs .

Thermopower mutation manifested again and negative drift occurred . But bipolar mutations occur thermopower time is different , the first thermoelectric potential positive changes , and the negative electrode . As can be seen , under the same conditions , its stability and domestic wire variation of the same , nor found over domestic wire has obvious advantages , this shows that our wire stability has reached the international advanced level of similar products .


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