Tungsten and Tungsten Alloys

Tungsten is a metal with an extremely high density and thermal capacity. Not only does it have the highest melting point of all metals, it also exhibits the greatest mechanical strength, very high stiffness and the smallest thermal expansion coefficient. Temperatures like those on the surface of the sun are required to bring tungsten to a boil (approx. 5,900°C). With a density of 19.28 g/cm³, tungsten is also among the heaviest metals which is why it is used among other things for specific mass balancing. Tungsten takes eighth place in the electrical conductivity ranking. This means it has about 31% of the electrical conductivity of copper. Tungsten is also a special metal in terms of its chemistry. It is extraordinarily resistant to air exposure at room temperature. Only at high temperatures does it gradually burn, forming tungsten (VI) trioxide (WO3). It is impervious to most acids and bases. Mineral acids, hydrofluoric acid and even nitrohydrochloric acid (aqua regia) only attack the metal slowly. It does however dissolve quickly in a mixture of nitric and hydrofluoric acid.

Physical properties of tungsten:

Chemical properties of tungsten:

Physical and mechanical properties

Density 18.0 – 19.25 g/cm³ (depending on the degree of deformation) Strength at 1.0 – 1.99 mm diameter > 1500 – 2200 MPa at 2.0 – 3.2 mm diameter > 1300 – 2000 MPa Expansion < 6 % Recrystallisation properties Start of recrystallisation: approx. 1150 °C Full recrystallisation: approx. 1350 °C 1 hour Specific electrical resistance 300 K 5,65 µΩcm 500 K 10,65 µΩcm 1000 K 24,93 µΩcm 1500 K 40,36 µΩcm 2000 K 56,67 µΩcm 2500 K 73,91 µΩcm 3000 K 92,04 µΩcm 3500 K 111,10 µΩcm Thermal conductivity at 293° K 174 W/m·K Temperature coefficient 273 – 373 K 4,5 · 10-6 K-1 Surface Can be ground, drawn (black/cleaned), wrought, turned, milled and eroded Heat treatment May be annealed or unannealed