Brass
Brass is the term used for
alloys of
copper and
zinc in a
solid solution. Typically it is more than 50% copper and from 5 to 20% zinc
[Brasses and other Copper-Zinc Alloys, Copper Development Association, London, England. Publication No.6, ], in comparison to
bronze which 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.
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(L-R) Decorative brass paperweight, along with zinc and copper samples |
Brass has a yellow colour, somewhat similar to
gold. It is relatively resistant to
tarnishing, and is often used as decoration.
Brass has been known to man since prehistoric times, long before zinc itself was discovered. It was produced by melting copper together with
calamine, a zinc ore. During this process, the zinc is extracted from the calamine and instantly mixes with the copper. Pure zinc, on the other hand, is too reactive to have been produced by ancient metalworking techniques.
The malleability and acoustic properties of brass have made it the metal of choice for
brass musical instruments such as the
trumpet,
tuba,
trombone,
saxophone,
harmonica, and
euphonium. In organ pipes designed as "reed" pipes, brass strips are used as the "reed". It has higher malleability than copper or zinc.
By varying the proportions of copper and zinc, the properties of the brass can be changed, allowing hard and soft brasses. The relatively low melting point (900-940 degrees C depending on composition) of brass and its flow characteristics make it a relatively easy material to cast.
Today almost 90% of all brass alloys are recycled. 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.
Aluminium makes brass stronger and more corrosion resistant. Aluminium also causes a highly beneficial hard layer (
Al2O3) 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, aluminium, 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.
Brass was used to make fan blades, fan cages and motor bearings in many antique fans that date before the 1930s.
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Admiralty brass contains 30% zinc and 1%
tin which inhibits dezincification in most environments.
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Alpha brasses (
Prince's metal), with less than 35% zinc, are malleable, can be worked cold, and are used in pressing, forging, or similar. They contain only one phase, with
face-centered cubic crystal structure.
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Alpha-beta brass (
Muntz metal), also called
duplex brass, is 35-45 % zinc and is suited for hot working. It contains both α and β' phase; the β'-phase is
body-centered cubic and is harder and stronger than α. Alpha-beta brasses are usually worked hot.
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Aluminium brass contains aluminium, which improves its corrosion resistance.
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Arsenical brass contains an addition of
arsenic and frequently aluminium and is used for
boiler fireboxes.
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Beta brasses, with 45-50 % zinc content, can only be worked hot, and are harder, stronger, and suitable for casting.
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Cartridge brass is a 30% zinc brass with good cold working properties.
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Common brass, or
rivet brass, is a 37% zinc brass, cheap and standard for cold working.
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High brass, contains 65% copper and 35% zinc, has a high tensile strength and is used for
springs,
screws,
rivets.
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Leaded brass is an alpha-beta brass with an addition of
lead. It has excellent machinability.
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Low brass is a copper-zinc alloy containing 20% zinc with a light golden color, excellent ductility and is used for flexible metal hoses and metal
bellows.
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Naval brass, similar to admiralty brass, is a 40% zinc brass and 1% tin.
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Red brass is an American term for CuZnSn alloy known as
gunmetal.
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White brass contains more than 50 % zinc and is too brittle for general use.
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Yellow brass is an American term for 33% zinc brass.Brass can be used for Cryogenic containers
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Calamine brass — brass alloy and manufacturing process from discovery until the late 18th century
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Corinthian brass — an alloy of gold, silver and copper, known to antiquity
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Pinchbeck — a brass that closely resembles gold in appearance.
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Bronze — an alloy of
copper with
tin and optionally
zinc,
silicon,
nickel and other metals
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Cupronickel — an alloy of copper with nickel
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Brass instrument — a musical instrument usually made of brass
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Brass rubbing — reproduction of
brasses, commemorative plates laid down in British and European churches from the 13th Century onwards'''
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National Pollutant Inventory - Copper and compounds fact sheet
