The applications of tungsten wire
Tungsten wire is mainly used in incandescent lamp, halogen tungsten lamp and other electric light source. After the tungsten wire is heated, it can emit the electron. And the higher voltage in two sides of the light tube can form the electric field, then these electrons in the fire tube will be informed to speed up, at this time, it will form an electronic flow with a certain speed and energy. In addition, tungsten wire can also be used for high temperature furnace heating materials, thermal electronic tube and composite reinforcement etc.
Thorium tungsten wire is used for tungsten wire or tungsten rod of gas discharge lamp cathode, in order to reduce the electron work function, we must add 0.5 ~ 3% of thorium. As the thorium is a radioactive element and it can pollute environment. So it is often used for making the thorium tungsten wire or cerium tungsten rod with cerium. But the evaporation rate of the cerium is high, so the cerium tungsten wire or cerium tungsten rod can only be used for gas discharge lamp with small power.
Once the tungsten wire has the recrystallization phenomenon after the high temperature use, it will become very brittle, and it's easy to break in the impact or vibration conditions. In some electric light source products with requirements of high reliability, in order to prevent the filament fracture, the doped tungsten wire often be added 3 %~ 5% of rhenium, it is called tungsten rhenium wire, it can make the tungsten brittle ductile transition temperature dropped to room temperature or below. This is a very strange rhenium effect. Up to now, any element can't replace the rhenium that produces the same effect in tungsten.
Tungsten has a good ability of acid resistant and nalkali resistant at room temperature, but it is easy to be oxidized in the humid air, so the fine tungsten wire can't be stored in the humid environment for too long. In addition, the tungsten will begin to react with carbon, at this time, tungsten carbide will be got. So the filament burn hydrogen treatment should pay attention to this problem, or the filament will become brittle fracture if the tungsten has a reaction with the graphite lubricant on surface of tungsten.
Thorium tungsten wire is used for tungsten wire or tungsten rod of gas discharge lamp cathode, in order to reduce the electron work function, we must add 0.5 ~ 3% of thorium. As the thorium is a radioactive element and it can pollute environment. So it is often used for making the thorium tungsten wire or cerium tungsten rod with cerium. But the evaporation rate of the cerium is high, so the cerium tungsten wire or cerium tungsten rod can only be used for gas discharge lamp with small power.
Once the tungsten wire has the recrystallization phenomenon after the high temperature use, it will become very brittle, and it's easy to break in the impact or vibration conditions. In some electric light source products with requirements of high reliability, in order to prevent the filament fracture, the doped tungsten wire often be added 3 %~ 5% of rhenium, it is called tungsten rhenium wire, it can make the tungsten brittle ductile transition temperature dropped to room temperature or below. This is a very strange rhenium effect. Up to now, any element can't replace the rhenium that produces the same effect in tungsten.
Tungsten has a good ability of acid resistant and nalkali resistant at room temperature, but it is easy to be oxidized in the humid air, so the fine tungsten wire can't be stored in the humid environment for too long. In addition, the tungsten will begin to react with carbon, at this time, tungsten carbide will be got. So the filament burn hydrogen treatment should pay attention to this problem, or the filament will become brittle fracture if the tungsten has a reaction with the graphite lubricant on surface of tungsten.
Next：下一篇：The applications of molybdenum
