The melting point of tungsten is 3410℃, the boiling point is about 5900℃, and the thermal conductivity is 174 w / m at 10 ~ 100℃, at high temperature, the evaporation rate is slow, the coefficient of thermal expansion is small, and the coefficient of expansion is 4.5 * 10-6 / K-1. at 0 ~ 100℃.
The resistance of tungsten is 3 times larger than that of copper, and the resistivity is 10-8 ohm/ m at 20℃.
Tungsten has good hardness, high density (the density of tungsten is 19.25 g / cm 3), and good high temperature strength, the electron emission performance is also good.
The mechanical properties of tungsten are mainly determined by its stress state and heat treatment process. In the cold state, tungsten can not be processed by pressure. Forging, rolling, drawing shall be carried out in the hot state.
At room temperature, tungsten is stable in air, at 400-500 degrees, tungsten begins to obviously oxidize to form blue black dense W03 protective film.
At room temperature, tungsten is not easy to be corroded by acid, alkali and aqua, but it can be dissolved in the the mixture of hydrofluoric acid aqua regia.
The main uses of tungsten:
Tungsten and its alloys are widely used in electronics, electric light source industry. It is used to produce a variety of lighting bulbs, electronic tube filament, it uses the doped tungsten wires with sagging resistance performance. The large size of the tungsten wire is also used as a heating element of vacuum furnace. Tungsten is the main alloying elements of high speed tool steel, alloy structural steel, spring steel, heat resistant steel and stainless steel. The amount of tungsten used in the production of special steel is very large.
