Brass Alloys

Topics: Brass, Copper, Bronze Pages: 9 (2731 words) Published: October 16, 2010

Brasses are copper zinc alloys. It is a substitutional alloy. Brass has higher malleability than copper or zinc. In general, they have good strength and corrosion resistance, although their structure and properties are a function of zinc content. The relatively low melting point of brass (900 to 940°C, depending on composition) 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. The density of brass is approximately 8400 to 8730 kilograms per cubic meter (equivalent to 8.4 to 8.73 grams per cubic centimeter). Today almost 90% of all brass alloys are recycled. Because brass is not ferromagnetic, 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 heated and extruded into the desired form and size. The color terms yellow and red are American terms referring to the composition of the brass. Brass goes from dark reddish brown to light silvery yellow depending on the amount of zinc. The more zinc the lighter the color. Red brass is really not brass as it is an alloy of copper, zinc, and tin. It is also called gunmetal

Brass Alloys:

Gilding metal
It is the softest type of brass commonly available. An alloy of 95% copper and 5% zinc, gilding metal is typically used for ammunition components.

Rich low Brass
It contains 15% zinc. It is often used in jewelry applications.

Low Brass
It is a copper-zinc alloy containing 20% zinc with a light golden color and excellent ductility; it is used for flexible metal hoses and metal bellows.

Cartridge Brass
It contains 30% zinc brass with good cold working properties.

Yellow Brass
It is an American term for 33% zinc brass.

Alpha (α) Brass
Contains less than 35% zinc. These brasses have good strength and ductility. They are malleable, can be worked cold, and are used in pressing, forging, or similar applications. They are single phase alloys consisting of solid solution of zinc and alpha copper, with face-centered cubic crystal structure.The strength and ductility of these alloys increases with increasing zinc content.

Alpha-beta (α + β) Brass
Muntz metal, also called duplex brass, contains 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.

Beta Brass
Contains 45–50% zinc content. Can only be worked hot. They are harder, stronger, and suitable for casting.

White Brass
Contains more than 50% zinc and is too brittle for general use. The term may also refer to certain types of nickel silver alloys as well as Cu-Zn-Sn alloys with high proportions (typically 40 %+) of tin and/or zinc, as well as predominantly zinc casting alloys with copper additive.

By adding different elements to brass we can improve its properties:

Admiralty Brass
Contains 30% zinc, and 1% tin which inhibits dezincification in most environments.

Aich's alloy
Typically contains 60.66% copper, 36.58% zinc, 1.02% tin, and 1.74% iron. Because of its corrosion resistance, hardness and toughness, it is used in marine service. A characteristic application is to the protection of ships' bottoms, but more modern methods of cathodic protection have rendered its use less common. Its appearance resembles that of gold.

Aluminum Brass
Contains aluminum. It is used for seawater service and also in coins. Aluminum makes brass stronger and more corrosion resistant. Aluminum also causes a highly beneficial hard layer of aluminum oxide (Al2O3) to be formed on the surface that is thin, transparent and self healing.

Arsenical Brass
Contains an addition of arsenic and frequently aluminum and is used for boiler...
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