Appearance and Characteristics
Harmful effects:
Tungsten is considered to be of low toxicity.
Characteristics:
Tungsten is a very hard, dense, silvery-white, lustrous metal that tarnishes in air, forming a protective oxide coating. In powder form tungsten is gray. The metal has the highest melting point of all metals, and at temperatures over 1650 oC also has the highest tensile strength. Pure tungsten is ductile, and tungsten wires, even of a very small diameter, have a very high tensile strength. Tungsten is highly resistant to corrosion. It forms tungstic acid (H2WO4), or wolframic acid from the hydrated oxide (WO3) and its salts are called tungstates, or wolframates. When present in compounds, tungsten exists mostly in the oxidation state VI. Tungsten is one of the five major refractory metals (metals with very high resistance to heat and wear).
Uses of Tungsten
Tungsten and its alloys are widely used for filaments in older style (not energy saving) electric bulbs and electronic tubes. Tungsten is also used as the filament in halogen tungsten lamps. These lamps use halogens like bromine and iodine to prevent the tungsten filament from degrading and are therefore more energy efficient than standard incandescent light bulbs. High speed steel (which can cut material at higher speeds than carbon steel), contains up to 18% tungsten. Tungsten is used in heavy metal alloys because of its hardness and in high-temperature applications such as welding. Tungsten carbide (WC or W2C) is extremely hard and is used to make drills. It is also used for jewelry because of its hardness and wear resistance.