Tungsten and rhenium made of various components of tungsten-rhenium alloy, these alloys overcome the shortcomings of pure tungsten and pure rhenium, with many excellent properties, such as high melting point, high strength, high hardness, high plasticity, high recrystallization temperature, high thermoelectric potential value, low steam pressure, low electron escape work and low plastic-brittle transition temperature, colleagues they also have excellent resistance to "water cycle" reaction performance, The price is also 75-95% lower than pure rhenium. Therefore, tungsten-rhenium alloy has been widely used in electronic technology, thermal control, modern nuclear technology and aerospace technology, temperature measurement, instrumentation, electrical appliances and other cutting-edge science and technology departments. In particular, tungsten-rhenium alloy wire is matched into tungsten-rhenium thermocouple, which has a high thermoelectric potential and sensitivity, and a wide range of temperature measurement, fast reflection speed, good corrosion resistance, and is a good thermal sensing material in the field of temperature measurement.
1, molybdenum rhenium alloy mechanical properties
As a body centered cubic metal, pure molybdenum is brittle at room temperature and has poor processing performance, which restricts the deep processing performance and service efficiency of metal molybdenum to a certain extent. The addition of rhenium to molybdenum can significantly improve the low temperature brittleness of molybdenum, and then improve its processing performance, increase the strength while still maintaining good plasticity, and the addition of rhenium also changes the mechanical deformation behavior of molybdenum in the process of hot and cold processing from single slip to twin and slip combined, inhibits the embrittleness of carbon and oxygen, and improves the welding performance of the material. It can make the forged and rolled products have lower tough-brittle transition temperature and reduce the embrittlement degree of the materials after recrystallization annealing. This addition of rhenium to improve the properties of molybdenum is called the "rhenium effect".
2, molybdenum rhenium alloy thermal physical properties
Figure 2 shows the effect of rhenium content on the thermal conductivity and thermal expansion coefficient of molybdenum rhenium alloy. As can be seen from Figure 2, for molybdenum-rhenium alloys of the same composition, the thermal conductivity gradually decreases and the coefficient of thermal expansion gradually increases with the increase of temperature. With the increase of rhenium content, the thermal conductivity of molybdenum-rhenium alloys with different compositions decreases gradually at the same temperature. In addition, with the increase of rhenium content, the coefficient of thermal expansion at the same temperature increases gradually. Possible reasons for this phenomenon are as follows:
The thermal conductivity of pure rhenium is less than the thermal conductivity of pure molybdenum, and the thermal expansion coefficient of pure rhenium is greater than the thermal expansion coefficient of pure molybdenum, so with the increase of rhenium content, the thermal conductivity at the same temperature gradually decreases, and the thermal expansion coefficient gradually increases.
Effect of rhenium content on thermal conductivity and thermal expansion coefficient of molybdenum-rhenium alloys
Application of tungsten-rhenium alloy wire in electrovacuum technology
The main performance requirements of vacuum tubes, picture tubes and bulb hot wires are:
1: Low temperature ductility, that is, a good wire forming. Processed filaments are wound, folded or twisted into filaments of various shapes and sizes, and must have good insulation between each other. Low plastic-brittle transition temperature, good uniformity and consistency
2: Low temperature annealing ductility is good, that is, two times winding wire formability is good. The filament parts after a wire winding are annealed to fix the shape and size of the parts. Generally, the annealing is carried out within the range of the temperature of a single recrystallization of the wire. Only low temperature annealing of good ductility wire can meet the requirements of secondary winding, that is, making double helix filament, or multiple winding and folding.
3: High temperature ductility, that is, ductility after secondary recrystallization. To core wire, transport. In the process of tube loading, vibration and impact must be received, and the filament with poor inflammation will be destroyed. The made filament should be used at high temperatures, and most of the filament should exist in a spiral shape during use, and the filament is longer and has a certain quality. In the use of the process to keep the pitch does not change, high temperature sag resistance is the key.
Our company produces W-3Re wire, W-5Re wire, W-20Re wire, W-25Re wire can meet the above requirements.
Application of tungsten-rhenium alloy wire in electronic tube materials
The tube is often affected by temperature changes and strong vibration, and the pitch of the spiral wire is easy to change, and even collision causes electrical short circuit. The bare wire is coated with a layer of aluminum oxide powder to improve the strength of the spiral wire, reduce the embrittlement factor, and increase the insulation, so that temperature fluctuations and mechanical vibration will not short-circuit the filament spiral collision.
The tungsten-rhenium alloy wire used in the electron tube filament has a wide range of components. The filament with good anti-sag performance is generally doped W-3Re tungsten-rhenium alloy wire. The filament with good ductility at low temperature is generally used as W-20Re and W-25Re tungsten rhenium alloy wire. The wire winding and life test of the electron tube filament made of tungsten-rhenium alloy wire are carried out. The results are shown in the table below. When annealing at 2000℃ and 2500℃, with the increase of rhenium content, the ratio of wire radius increases, indicating that the plasticity of the alloy with high rhenium content decreases, the wire winding performance is poor, but the filament life is increased.
Satellite tubes require long life, tens of thousands or even hundreds of thousands of hours, high reliability and vibration resistance. When launching an artificial Earth satellite, the electron tube is subjected to 5-8g gravitational acceleration vibration. Doped tungsten powder was prepared by hydrogen reduction using blue tungsten oxide as raw material, adding high content dopant and cobalt. After washing with hydrofluoric acid, it was mixed with ammonium rhenate solution, and then reduced with hydrogen to make pickling doped W-3Re alloy powder. After pressing and sintering, the doped W-3Re alloy wire is made by rotary forging and drawing. This kind of alloy wire can meet the requirements of satellite long-life surface tube filament.
The electronic tube used by the ground receiving station of artificial earth satellite requires high mechanical strength and will not break the electronic tube filament when receiving the resonance of the same frequency; Bending 90° Angle is not brittle split, break and crack; The filament evaporation rate is low to prevent the tube wall from blackness, and the tungsten-rhenium alloy wire with high rhenium content can meet this requirement.
The heating filament of the accelerator tube electron gun of the medical treatment machine and the industrial flaw detection machine uses tungsten-rhenium alloy wire to ensure the requirements of long life noodles and other life requirements.
The folding filament of the high voltage rectifier is made of tungsten-rhenium alloy wire, which is not brittle. Splitting, breaking and cracking, and the consistency of the electrical parameters of the rectifier tube is better.