Alloy is unique a combination of qualities of couple of rare metals. A basis of an alloy is tungsten which possesses the greatest refractoriness, and also hardness among the known metals. Its temperature of melting reaches 3410 °C, and temperature of boiling is commensurable with a temperature on a surface of the sun and makes 6690 °C. Thus, tungsten alloys surpass other materials in the hardness and refractoriness. In turn rhenium a little than concedes to tungsten. Its thermal stability in combination with high resistance to corrosion put it in number of leaders among other metals. Rhenium melting temperature = 3170 °C, and boils it at 5870 °C. At an alloying of tungsten of 5% of rhenium, the indicator of plasticity and t ° tungsten recrystallizations raises. BP5 alloy is used, as a rule, as a positive electrode in the thermocouple.
For achievement in the thermocouple of the maximum values of thermo-electromotive force an alloy of BP is connected as a negative electrode, at the same time the content of rhenium should not exceed 35%. It allows an alloy not to lose uniformity at a temperature above 1100 °C, otherwise with loss of uniformity decreases termo-EDS. In domestic metallurgy, as a rule, use alloys with the content of rhenium not higher than 20% that allows to take temperature to 2500 °C. A BP alloys possesses resistance to influence of helium, argon, hydrogen and dry nitrogen. Stability of an alloy increases by 2-3 times at t ° to 2000 °C at an alloying kremneshchelochny additives.
One of shortcomings of alloys of BP is bad reproducibility termo-EDS. There is a need to divide alloys into the following categories of thermoelectrode couples: A-1 provides use of material at temperatures of the reaching 2200 °C; A-2 and A-3 use up to 1800 °C at t°sredy. Use of a wire from various parties, in a type of the fact that each party possesses the indicator of thermo-electromotive force is forbidden. At contact of nitrogen with an alloy in vacuum it is necessary to monitor removal of organic substances, dust and it is obligatory to maintain purity.