Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.
By comparison, bronze is principally an alloy of copper and tin. Bronze does not necessarily contain tin, and a variety of alloys of copper, including alloys with arsenic, phosphorus, aluminium, manganese, and silicon, are commonly termed “bronze”. The term is applied to a variety of brasses and the distinction is largely historical, both terms having a common antecedent in the term latten.
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, doorknobs, ammunition, and valves; for plumbing and electrical applications; and extensively in musical instruments such as horns and bells for its acoustic properties. It is also used in zippers. Because it is softer than most other metals in general use, brass is often used in situations where it is important that sparks not be struck, as in fittings and tools around explosive gases.
To enhance the machinability of brass, lead is often added in concentrations of around 2%. Since lead has a lower melting point than the other constituents of the brass, it tends to migrate towards the grain boundaries in the form of globules as it cools from casting. The pattern the globules form on the surface of the brass increases the available lead surface area which in turn affects the degree of leaching. In addition, cutting operations can smear the lead globules over the surface. These effects can lead to significant lead leaching from brasses of comparatively low lead content.
Silicon is an alternative to lead; however, when silicon is used in a brass alloy, the scrap must never be mixed with leaded brass scrap because of contamination and safety problems.
The so-called dezincification resistant (DZR or DR) brasses 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.
Low-zinc brasses below 20% are resistant to stress-corrosion cracking and are easily formed. Red brass (15% zinc) is highly corrosive-resistant. Yellow brasses contain from 34 to 37% zinc and have good ductility and high strength and can withstand severe cold-working. Cartridge brass contains 30-33% zinc. Muntz Metal (40% zinc) is primarily a hot-working alloy used where cold-forming operations are unnecessary. Some brasses also contain low percentages of other elements, e.g., manganese, aluminium, silicon, lead, and tin (admiralty metal, naval brass).
- Admiralty brass contains 30% zinc, and 1% tin which inhibits dezincification in many environments.
- Aich’s alloy typically contains 60.66% copper, 36.58% zinc, 1.02% tin, and 1.74% iron. Designed for use in marine service owing to its corrosion resistance, hardness and toughness. 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.
- Alpha brasses with less than 35% zinc, are malleable, can be worked cold, and are used in pressing, forging, or similar applications. They contain only one phase, with face-centered cubic crystal structure.
- Prince’s metal or Prince Rupert’s metal is a type of alpha brass containing 75% copper and 25% zinc. Due to its beautiful yellow color, it is used as an imitation of gold. The alloy was named after Prince Rupert of the Rhine.
- 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.
- Aluminium brass contains aluminium, which improves its corrosion resistance. It is used for seawater service and also in Euro coins.
- Arsenical brass contains an addition of arsenic and frequently aluminium and is used for boiler fireboxes.
- Beta brasses, with 45–50% zinc content, can only be worked hot, and are harder, stronger, and suitable for casting.
- Cartridge brass is a 30% zinc brass with good cold working properties. Used for ammunition cases.
- Common brass, or rivet brass, is a 37% zinc brass, cheap and standard for cold working.
- DZR brass is dezincification resistant brass with a small percentage of arsenic.
- Gilding metal is the softest type of brass commonly available. An alloy of 95% copper and 5% zinc, gilding metal is typically used for ammunition bullet “jackets”, e.g. full metal jacket bullets.
- High brass contains 65% copper and 35% zinc, has a high tensile strength and is used for springs, screws, and rivets.
- Leaded brass is an alpha-beta brass with an addition of lead. It has excellent machinability.
- Lead-free brass as defined by California Assembly Bill AB 1953 contains “not more than 0.25 percent lead content”.
- Low brass 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.
- Manganese brass is a brass most notably used in making golden dollar coins in the United States. It contains roughly 70% copper, 29% zinc, and 1.3% manganese.
- Muntz metal is about 60% copper, 40% zinc and a trace of iron, used as a lining on boats.
- Naval brass, similar to admiralty brass, is 40% zinc and 1% tin.
- Nickel brass is composed of 70% copper, 24.5% zinc and 5.5% nickel used to make pound coins in the pound sterling currency.
- Nordic gold, used in 10, 20 and 50 cts euro coins, contains 89% copper, 5% aluminium, 5% zinc, and 1% tin.
- Red brass is both an American term for the copper-zinc-tin alloy known as gunmetal, and an alloy which is considered both a brass and a bronze. It typically contains 85% copper, 5% tin, 5% lead, and 5% zinc. Red brass is also an alternative name for copper alloy C23000, which is composed of 14–16% zinc, 0.05% iron and lead, and the remainder copper. It may also refer to ounce metal, another copper-zinc-tin alloy.
- Rich low brass (Tombac) is 15% zinc. It is often used in jewelry applications.
- Tonval brass (also called CW617N or CZ122 or OT58) is a copper-lead-zinc alloy.
- 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.
- Yellow brass is an American term for 33% zinc brass.
Brass (industrial) use
Condensor tube plates, piping, hose nozzles and couplings, oil gauges, flow indicators, air cocks, drain cocks, marine equipment.
Shipment / Storage / Risk factors
Brass products include sheet, strip, tube, wire, wrought shapes and castings.
When the brass product is thin and of a high surface finish, scratches, gougings, tears, etc., may ruin the product to the extent of the damaged area. Sea water and fresh water produce stains, and sea water may give rise to corrosion. So long as the stains are superficial, the product can be used, but if rough and pitted, the material may be rejected. Manufacturing difficulties such as scabbiness or folds (‘pinches’) can be readily identified, as these cannot be produced by rough handling or by corrosion in transit. Cracks, particularly in tubes or pressings, may generally be attributed to mild corrosive conditions in transit, in conjunction with the omission of a stress relieving treatment after manufacture.
Surface defects apart from corrosion pits, scratches and dents, can easily be attributed to faulty manufacture. Scabbiness is caused by the metal splashing when it is poured into the mould and cooling in droplets on the side. An oxide film is formed around these droplets which prevents them mixing with the rest of the metal in the ingot. Roughness is caused by the ingot sticking to the mould, causing a tearing of the surface on removal. Folds (‘pinches’) are caused in casting with too low a pouring rate, allowing a series of oxide films to be formed. All these defects originated in a faulty ingot and the faults remain because of the inability of oxidized surfaces to weld together.
Superficial staining or slight corrosion may be removed by the use of mild abrasives and, provided the product is not made to accurate dimensions, scratches, etc., may be polished out with an abrasive. Ammonia solutions with, or without, mild abrasives may be used for cleaning by wiping provided the operation is controlled and the surface is washed thoroughly afterwards. There is the possibility that stressed brass may crack when brought into contact with ammonia.
Sheets indented for utensil manufacture have a smooth finish. While scratches, gouging, tears, etc., may ruin the sheets for this purpose to the extent of the damaged area, the undamaged part of the sheets can be used for cutting segments of a suitable size from which utensils may also be made.