In addition to a small amount of tungsten wire used as heating material of high temperature furnace, heating element of electron tube and reinforcing bar of composite material, most of the tungsten wire is used for making filament of various incandescent lamp and halogen tungsten lamp and electrode of gas discharge lamp. For tungsten wire or tungsten rod used as cathode of gas discharge lamp, 0.5 ~ 3% thorium must be added, which is called tungsten wire. Because thorium is a radioactive element that contaminates the environment, cerium is used instead of thorium to make tungsten-cerium wire or tungsten-cerium rod. Because of the high evaporation rate of cerium, the tungsten-cerium wire or tungsten-cerium rod can only be used in low-power gas discharge lamps.
Once the tungsten wire is recrystallized at high temperature, it becomes brittle and easily breaks under shock or vibration. In some electric light source products requiring high reliability, 3 ~ 5% rhenium is often added into the doped tungsten wire to prevent the filament from breaking, which is called tungsten-rhenium wire. It can reduce the brittle transition temperature of tungsten to room temperature or below. This is a curious rhenium effect, and no element has yet been found to replace rhenium to produce the same effect in tungsten.
Tungsten has good acid and alkali resistance at room temperature, but it is easy to be oxidized in moist air. In addition, tungsten starts to react with carbon around 1200℃ to form tungsten carbide. Therefore, attention should be paid to the hydrogen burning treatment of the filament, otherwise the filament will become brittle and break if the tungsten reacts with the graphite lubricant on the surface.