Applications of tungsten wire

Aside from a small amount used as heating material in high-temperature furnaces, heat exchangers in electron tubes, and reinforcing ribs in composite materials, tungsten filaments are mostly used to manufacture filaments for various incandescent and halogen tungsten lamps, as well as electrodes for gas discharge lamps. For tungsten filaments or rods used as cathodes in gas discharge lamps, 0.5–3% thorium is added to reduce its electron work function, resulting in tungsten-thorium filaments. Since thorium is a radioactive element and pollutes the environment, cerium is sometimes used instead to make tungsten-cerium filaments or rods. However, cerium has a high evaporation rate, so tungsten-cerium filaments or rods can only be used in low-power gas discharge lamps.

Once tungsten filaments recrystallize after high-temperature use, they become very brittle and easily break under impact or vibration. In some high-reliability electric light source products, to prevent filament breakage, 3–5% rhenium is often added to the doped tungsten filament, resulting in tungsten-rhenium filaments. This lowers the ductile-brittle transition temperature of tungsten to room temperature or below. This is a very peculiar rhenium effect, and so far no element has been found that can replace rhenium to produce the same effect in tungsten.