Brass is any
alloy of
copper and
zinc; the proportions of zinc and copper can be varied to create a range of brasses, each of which has unique properties
[''Engineering Designer, v 30, n 3, May-June 2004, 6-9]. Note that in comparison
bronze is principally an alloy of copper and
tin.
[''Machinery Handbook'', Industrial Press Inc, New York, Edition 24, page 501]. Despite this distinction, some types of brasses are called bronzes. Brass is a substitutional
alloy. It is used for decoration for its bright gold-like appearance; for applications where low friction is required such as locks, gears, bearings, ammunition, and valves; for plumbing and electrical applications; and extensively in
musical instruments such as horns and bells for its acoustic properties.
Brass has a yellow color, somewhat similar to
gold. It is relatively resistant to
tarnishing, and is often used as decoration and for coins.
Brass has likely been known to humans since prehistoric times, even before zinc itself was discovered. It was produced by melting copper together with
calamine, a zinc ore. In the German village of
Breinigerberg an ancient Roman settlement was discovered where a calamine ore mine existed. During the melting process, the zinc is extracted from the calamine and mixes with the copper. Pure zinc, on the other hand, has too low a boiling point to have been produced by ancient metalworking techniques. The many references to 'brass' appearing throughout the
King James Bible are thought to signify another bronze alloy, or copper, rather than the strict modern definition of 'brass'
[Cruden's Complete Concordance p. 55].
Properties
The malleability and acoustic properties of brass have made it the metal of choice for
brass musical instruments such as the
trombone,
tuba,
trumpet,
euphonium, and the
French horn. Even though the
saxophone is classified as a
woodwind instrument and the
harmonica is a
free reed aerophone, both are also often made from brass. In
organ pipes designed as "reed" pipes, brass strips are used as the "reed".
Brass has higher malleability than copper or zinc. The relatively low melting point (900–940 °C depending on composition) of brass and its flow characteristics make it a relatively easy material to cast. By varying the proportions of copper and zinc, the properties of the brass can be changed, allowing hard and soft brasses.
Today almost 90% of all brass alloys are recycled. Because most brass is nonmagnetic, it can be separated from ferrous scrap by passing the scrap near a powerful magnet. Brass scrap is collected and transported to the foundry where it is melted and recast into billets. Billets are later heated up and extruded into the right form and size.
Aluminum makes brass stronger and more corrosion resistant. Aluminum also causes a highly beneficial hard layer of
aluminium oxide (Al
2O
3) to be formed on the surface that is thin, transparent and self healing. Tin has a similar effect and finds its use especially in sea water applications (naval brasses). Combinations of iron, aluminum, silicon and manganese make brass wear and tear resistant. A well known alloy used in the automotive industry is 'LDM C673', where the right combination of manganese and silicon lead to a strong and resistant brass.
The so called
dezincification resistant (DZR) brasses, like alloy 'LDM G563' (known for its brand name 'Enkotal'), are used where there is a large corrosion risk and where normal brasses do not meet the standards. Applications with high water temperatures, chlorides present or deviating water qualities (soft water) play a role. DZR-brass is excellent in water boiler systems. This brass alloy must be produced with great care, with special attention placed on a balanced composition and proper production temperatures and parameters to avoid long-term failures. Drunen, Netherlands, has the only active production facility which makes these high grade brass alloys.
The copper in brass makes brass germicidal, via the
oligodynamic effect. For example, brass doorknobs disinfect themselves of many bacteria within eight hours
http://members.vol.at/schmiede/MsgverSSt.html. This effect is important in hospitals, but useful in many contexts.
Brass was used to make fan blades, fan cages and motor bearings in many antique fans that date before the 1930s. Brass can be used for fixings for use in
cryogenic systems, however its use is not limited to this.
[http://www.freepatentsonline.com/20020056992.html Example patent referring to fixings]
The density of brass is approximately 8.4 g/cm
3.