The application of tungsten and rhenium
Tungsten and rhenium are high melting point metals and they are widely used in high temperature fields. But they also have shortcomings, pure tungsten brittle, recrystallization temperature is very low; Pure rhenium has poor processing performance and high price. So that their application scope is greatly limited. Made components with the rhenium tungsten rhenium tungsten alloy, the alloy overcomes the drawback of pure tungsten and rhenium, has many excellent properties, such as high melting point, high strength, high hardness, high plasticity, high resistivity, high thermoelectric potential value of the recrystallization temperature, high, low vapor pressure, low electron work function and low plastic a brittle transition temperature, etc., At the same time, they also have excellent resistance to "water cycle" reaction performance, the price is also 75 ~ 95% lower than pure rhenium.
So tungsten-rhenium alloy in electronic technology, thermal control, modern nuclear technology and space navigation technology, temperature measurement field, instrumentation, electrical appliances and other cutting-edge science and technology departments have been widely used. Especially the tungsten-rhenium alloy wire matched into a thermocouple, has a very high thermoelectric potential and sensitivity, and a wide range of temperature measurement, fast reaction speed, good corrosion resistance, is a good thermal sensing material in the field of temperature measurement. Because tungsten-rhenium thermocouple replaces platinum-rhodium thermocouple it is the general trend.
Application in electric vacuum technology
The main performance requirements for tube, picture tube and bulb hot filament are:
1. Good low temperature ductility (that is, good formability of a winding wire). The processed wire material is wound, folded or twisted into filaments of various shapes and sizes, and there should be good insulation between each other, low plasticity brittle transition temperature, good uniformity and consistency;
2. Good low temperature annealing ductility (that is, good formability of secondary winding wire). After a filament winding, the filament parts are annealed to fix the shape and size of the parts. Annealing is generally carried out in the range of the temperature of the first recrystallization of the wire. Only low temperature annealed wire with good ductility can meet the requirements of double winding (making double helix filament) or multiple winding and folding;
3. Good high temperature ductility (that is, the ductility after secondary recrystallization). To core wire, transportation, pipe installation and other processes should be affected by vibration and impact, poor ductility of the filament will be destroyed. The made filament should be used at high temperature, and the filament should maintain the required shape during use.
4. Good anti-sagging performance at high temperature. Because most of the filament exists in a spiral shape, the filament is longer and has a certain mass. In the process of use to keep the screw pitch does not change, high temperature anti-sagging is the key.
Used as electrical contact material
Electrical switches are commonly used many contact materials, such as car horn contact and ignition contact, voltage regulator contact, telephone contact, all kinds of electrical switch contact. In the work, each pair of contacts friction and spark corrosion and high frequency contact characteristics, therefore, the production of contact materials should meet the following requirements: 1 material contact resistance is small, 2 arc volt-ampire characteristics of small, 3 small etching rate, etc..
The metals that can be used as contact materials are copper, silver, platinum, rhodium, iridium, tungsten, molybdenum, rhenium, tungsten-copper alloy, tungsten-silver alloy, tungsten-steel alloy and high specific gravity alloy. Tungsten, molybdenum, rhenium and their alloys have been widely used in automobile horn contacts and igniter contacts. Tungsten-rhenium alloys for contact materials have been developed in recent years and can be compared with platinum, iridium, rhodium and other precious metal contacts.
Used as thermocouple material
Various components of tungsten-rhenium alloy wire can be paired to form tungsten-rhenium thermocouple. Widely used tungsten-rhenium thermocouple in industrial practice are:
Doped and tungsten-rhenium thermocouple. They have high thermoelectric potential value and high sensitivity, good linear thermoelectric potential -- temperature corresponding relationship, high measurement temperature (up to 2800 ℃), high accuracy (its allowable deviation of ± 0.25%T, ± 0.5%T and ± 1%T, etc.).
Tungsten-rhenium thermocouple is mainly used in vacuum, reducing atmosphere and inert atmosphere temperature measurement and high temperature field. Some special anti-oxidation measures can be taken to measure the temperature of platinum-rhodium thermocouple in oxidizing atmosphere. The price of tungsten-rhenium thermocouple is 12 ~ 18 times lower than that of single platinum-germanium thermocouple. The temperature measurement of tungsten-rhenium thermocouple instead of platinum-rhodium thermocouple has obvious economic benefits and has been paid more and more attention.
Other aspects of the application
(1) high temperature structural materials
Tungsten-rhenium alloys are used in aerospace aircraft as coatings for heat shields, rocket nozzles, cone parts, engines or engine parts. Tungsten-rhenium alloy container and crucible material for uranium extraction when heated to 2000℃ without reaction. Tungsten-rhenium alloy for heating element and heat insulation screen of high temperature furnace, crucible for evaporating high purity metal, spring, screw, nut, support rod and connecting rod in high temperature field, etc., with good plasticity.
(2) wear-resistant materials
Because of its high hardness, high strength, good wear resistance and corrosion resistance, tungsten-rhenium alloy can be used to make printing needles for printers, and its service life can reach 100 million times. In addition, it can also produce pen nib, center of gravity hammer and wear-resisting parts of surveying and mapping instruments.
(3) Electrode materials
Tungsten-rhenium alloy bar containing thorium, zirconia and cerium oxide dispersion particles, used for electrode of argon arc welding machine and non-consumable arc furnace melting electrode, it has high temperature resistance and ablation resistance, long service life.
