Like titanium, tungsten has come to embody the idea of advanced properties that helps drive stories for designers. However, unlike titanium, which has the highest strength-to-weight ratio of any metal, tungsten is a superheavy metal. Tungsten suggests technology, hardness and, in certain applications, a sense of being premium quality, such as in these darts. Derived from the Swedish words ‘tung’ and ‘sten’ meaning heavy stone, its applications in design are fairly limited, but due to its significant properties it deserves to be mentioned in this book.
Its main attributes, beyond its heaviness, are an outstanding hardness and temperature resistance; it has the highest temperature resistance of all metals. Hardness is not the same as toughness, which is a term used for metals and describes the ability of a material to absorb impact energy without breaking; hardness is the ability of material to resist indentation, which means it resists scratching, wear and abrasion and is difficult to machine. Tungsten has one of the highest melting points of all metals and at elevated temperatures is also at its highest strength. Tungsten carbide is one of the most well known forms of tungsten and, as with all the carbide family of metals, has the highest melting point of all engineering materials. An interesting application of the material is its use in football boots in the form of a powder to shift weight towards the impact point, to help ensure the most effective control of the ball.
Image: Tungsten darts by TGV Design
•Very high density
•Very hard
•High corrosion resistance
•Low electrical conductivity
•Low toxicity
•Extremely high melting point: 3410ºC (6192ºF)
•Recyclable
Sources
Tungsten is not found freely in nature. The principal ores of tungsten are wolframite (an iron manganese tungstate). World tungsten mining and supply is dominated by China, which produces more than half of the world’s output. Global production in 2011 was 72,000 tonnes with global reserves at 3,100,000 tonnes.
Cost
£70 ($110) per kg.
Sustainability issues
There are no major environmental concerns; however, tungsten powder has been known to have mild affects on animals and some reports suggest that it could be an ‘emerging contaminant’. It can be recycled and 30% of tungsten production is based on recycled content.
Production
Because tungsten has one of the highest ductile-to-brittle transition temperatures, its formability at room temperature is low. Its high heat resistance also makes it hard to cast, instead components are usually sintered from powder. It is available in various semi-finished states such as bars, tubes, wire, plate and sheets, from which it can be machined.
Typical applications
As one of the ‘hard metals’ its primary use is in heavy industry. In the shaping and cutting of other materials, particularly tool steels, it completely transformed the tooling industry. Apart from in darts, where its weight is used to stabilize its trajectory, tungsten is well known as the metal inside incandescent lightbulbs. Along with aluminium, cobalt, copper and zinc, tungsten is used in the nib of the common ballpoint pen. Less common applications include very hard and scratchresistant tungsten and tungsten carbide jewellery, fishing weights, and bullets; vapour-deposited tungsten oxide layers are used in self-darkening windowpanes. It is also used in high-temperature applications such as welding anvils, and used to make the thin wire for the heaters in the back windows of cars.
Derivatives
–Tungsten steel
–Tungsten carbide
–Tungsten chromium
–Tungsten bronze
–Cobalt tungsten
–Copper tungsten
–Silver tungsten
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–Very hard and dense –Corrosion resistant –High temperature resistance –Recyclable |
–Hard to cast or machine |