The white metals are a series of often decorative bright metal alloys used as a base for plated

silverware Silverware may refer to: * Household silver including **Tableware **Cutlery **Candlesticks *The work of a silversmith * Silverware is also a slang term for a collection of trophies A trophy is a tangible, durable reminder of a specific achieveme ...

, ornaments or novelties, as well as any of several lead-based or tin-based alloys used for things like bearings, jewellery, miniature figures, fusible plugs, some medals and metal

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * Ty ...

. The term is also used in the antiques trade for an item suspected of being silver, but not

hallmarked A hallmark is an official mark or series of marks struck on items made of metal, mostly to certify the content of noble metals—such as platinum, gold, silver and in some nations, palladium. In a more general sense, the term ''hallmark'' can al ...

. A white metal alloy may include antimony, tin, lead, cadmium, bismuth, and zinc (some of which are quite toxic). Not all of these metals are found in all white metal alloys. Metals are mixed to achieve a desired goal or need. As an example, a base metal for jewellery needs to be

castable In materials science, a refractory material or refractory is a material that is resistant to Thermal decomposition, decomposition by heat, pressure, or chemical attack, and retains strength and form at high temperatures. Refractories are polycr ...

, polishable, have good flow characteristics, have the ability to cast fine detail without an excessive amount of porosity and cast at between .

Silver

In compliance with British law, the British fine art trade uses the term "white metal" in auction catalogues to describe foreign silver items which do not carry British Assay Office

hallmarks A hallmark is an official mark or series of marks struck on items made of metal, mostly to certify the content of noble metals—such as platinum, gold, silver and in some nations, palladium. In a more general sense, the term ''hallmark'' can al ...

, but which are nonetheless understood to be silver and are priced accordingly.

Tin-lead and tin-copper alloys

Tin-lead and tin- copper alloys such as

Babbitt metal Babbitt metal or bearing metal is any of several alloys used for the bearing surface in a plain bearing. The original Babbitt alloy was invented in 1839 by Isaac Babbitt in Taunton, Massachusetts, United States. He disclosed one of his alloy recip ...

. have a low melting point, which is ideal for use as solder, but these alloys also have ideal characteristics for plain bearings. Most importantly for bearings, the material should be hard and wear-resistant and have a low coefficient of friction. It must also be shock-resistant, tough and sufficiently ductile to allow for slight misalignment prior to running-in. Pure metals are soft, tough and ductile with a high coefficient of friction. Intermetallic compounds are hard and wear-resistant but brittle. By themselves, these do not make ideal bearing materials. Alloys consist of small particles of a hard compound embedded in the tough, ductile background of a solid solution. In service the latter can wear away slightly, leaving the hard compound to carry the load. This wear also provides channels to allow in

lubricant A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, t ...

( oils). All bearing metals contain antimony (Sb), which forms hard cubic crystals.

References

{{DEFAULTSORT:White Metal Alloys Bearings (mechanical)

Silver

Tin-lead and tin-copper alloys

See also

References