Once recrystallized at high temperatures, tungsten becomes brittle and easily breaks under impact or vibration. In order to prevent the fracture of filament, rhenium is often added into the doped tungsten filament, which is called tungsten rhenium wire, and 1% ~ 5% rhenium is contained in the alloy (mass). In addition, silicon, aluminum and potassium are also added to improve the high-temperature performance of the material. It can reduce the brittle transition temperature of tungsten to room temperature or below.
Tungsten-rhenium wire has a series of excellent properties, such as high melting point, high strength, high hardness, high plasticity, high recrystallization temperature, high resistivity, low vapor pressure, low electron escaping work and low plastic brittle transition temperature. In addition to the above properties of tungsten rhenium alloy, the low rhenium alloy and the high rhenium alloy wire are matched into thermocouple, and have high thermoelectric potential value. Relationship between the thermoelectric potential value and temperature of various w-Rhenium thermocouples.
An alloy of tungsten and rhenium. One type is low rhenium alloy, which contains less than 5% rhenium. The other is the perrhenium alloy, which contains 20% ~ 30% rhenium. Its preparation method is similar to that of tungsten material. Its main application is the filament of special vacuum tube and color CRT, which requires high strength and high plasticity at high temperature components. The pairing of low-rhenium alloy and high-rhenium alloy can be used to measure thermocouples at high temperature of 1500 ~ 3000℃. Using tungsten rhenium thermocouple instead of platinum and rhodium thermocouple to measure temperature can save precious metals such as platinum and rhodium. Rhenium is also a rare metal, less resources, more expensive, if not necessary, should try to use no or less rhenium tungsten alloy.
In addition, the tungsten rhenium wire, 25%Re and 26%Re are two commonly used tungsten rhenium alloys, mainly used as thermocouple materials! The main advantages of tungsten - rhenium thermocouple are: 1. 2. Wide range of temperature measurement, up to 2500℃. But generally used in inert atmosphere or reducing atmosphere, or need to add a protective casing, generally Mo alloy casing！
