From DT Online
Revision as of 19:33, 26 April 2018 by DT Online
Very few metals in everyday use are in pure form (i.e. just the metallic element itself). In most cases, the metallic element has been mixed with another to improve a particular property or characteristic (e.g. Strength, Durability), to change its melting point or to improve how well it machines.
This process of mixing different metals together, or with other elements, to create a new material with particular properties and characteristics is known as Alloying and the resulting material is an Alloy.
- Small amounts of Carbon produce a range of Steels and thus, Steel can be seen to be an Alloy of Iron and Carbon.
- Tool Steel has a Carbon content of between 0.5% and 1.5%. This amount of Carbon can only be held in solution with Iron at a high temperature which, if cooled or quenched suddenly, is ‘frozen’ in solution to create material too Hard and Brittle for most purposes. The process of Tempering allows some Carbon to diffuse out and controls the balance between Hardness and Toughness to make products ranging from wood chisels to clock springs.
- The addition of Chromium to steel produces Stainless Steel which has many applications where high strength and resistance to corrosion is required. The once commonly seen grade 18/8 Stainless Steel (now known as 403 grade), used for utensils, cutlery and cookware commonly found in kitchens everywhere, indicates that the steel contains 18% Chromium for greater strength and 8% nickel to improve its sheen or polish.
- Brass is an Alloy of Copper and Zinc the proportions of which can be varied to create either a hard brass or a softer brass. Other elements may also be added to enhance particular properties (e.g. the addition of Lead can make it easier to machine and adding Tin helps to stop the Zinc leaching out in marine environments).
- Brass is a decorative metal, it casts and machines well, it is a good bearing metal and resistant to corrosion. It is used to making plumbing fittings, ornaments, door furniture, gears, bearings, instruments and electrical switchgear for example.
- Pinchbeck is a Brass in which the proportions of Copper and Zinc are chosen to result in a colour very close to Gold. Another 'Faux Gold' is Prince’s Metal which is also a Brass mixed to resemble Gold.
- Bronze is an Alloy of Copper with about 12% Tin. It is most commonly used for sculpture, coinage, some musical instruments and traditionally for ships' fittings, although this use is now largely superseded by Stainless Steel.
- Gunmetal is a Bronze used originally to make guns. It casts well and is used to make valves and fittings for steam and hydraulics.
- Latten is a term used in the Middle Ages and up to the early 19th Century as a general description of Copper-based Alloys. It was a type of Brass made into thin sheets and used for decorative metalwork and embellishment. The contract for making the effigy of Richard Beauchamp (1382-1489) the Earl of Warwick, which can be seen on his tomb in St Mary's Church, Warwiick, refers to: an image of a man armed, of fine latten, garnished with certain ornaments, viz., with sword, dagger, garter, helm, crest under his head, at his feet a bear muzzled and a gryphon, perfectly made of the finest latten . . . .
- Solders are Alloys used to join metals together. They are chosen to have a lower melting point than the metals to be joined so that, when heated, they can flow into the joint (and be ‘drawn’ into tight joints by Capillary Action). Solders are often also a Eutectic Alloy which means the proportions of the contributing elements are such that the Alloy solidifies quickly and at the lowest temperature.
- The once used Plumbers Solder had 50% Lead content which made it very useful for ‘wiping lead joints’ because it solidified slowly, giving time for the joint to be shaped, but Lead pipes are no longer used for plumbing because of the danger or Lead poisoning.
- The proportions of the contributing elements are varied to create ‘Easy’, ‘Medium’ and ‘Hard’ Silver Solders - terms which denote grades of solder designed to melt at different temperatures. This enables complex articles to be soldered together in sequence, starting with ‘Hard’ for example, without subsequent heating causing previously made joints to melt.
- Aluminium is the world's most abundant metal but difficult to extract. The ore is found in clay, Bauxite being the most common source (perhaps this is why the Martians first dug clay pits to build their machines in ‘War of the Worlds’ by H.G. Wells?).
- Pure Aluminium is lightweight, resistant to corrosion, Ductile, and Malleable but quite soft and low strength. Aluminium Alloys are designed to improve strength, casting and working properties, or to make the material heat-treatable.
- White Metal is a classification covering a range of light-coloured Alloys. The term is used by antique dealers to describe a variety of tableware and other non-silver ornaments or novelties. It describes also any of several Lead-based or Tin-based alloys used for things like bearings and small Zinc-based Die Cast components for example.