Copper Alloys Brass – Austral Wright Metals
Application Data Sheet – Copper Alloys
Brasses are copper zinc alloys with a wide range of engineering uses. The addition of zinc to copper raises the strength and gives a range of properties, and the brasses are a very versatile range of materials. They are used for their strength, corrosion resistance, appearance and colour, and ease of working and joining. The single phase alpha brasses, containing up to about 37% zinc, are very ductile and easy to cold work, weld and braze. The dual phase alpha-beta brasses are usually hot worked.
There are many brasses, with properties tailored for specific applications by the level of addition of zinc. Minor amounts of other alloying elements may also be added.
Brasses are often used for their appearance
C22000, 90/10 Gilding metal, combines a rich golden colour with the best combination of strength, ductility and corrosion resistance of the plain copper-zinc alloys. It weathers to a rich bronze colour. It has excellent deep drawing capability, and resistance to pitting corrosion in severe weather and water environments. It is used in architectural fascias, jewellery, ornamental trim, door handles, escutcheons, marine hardware.
C26000, 70/30 Brass and C26130, Arsenical brass, have excellent ductility and strength, and are the most widely used brasses. Arsenical brass contains a small addition of arsenic, which greatly improves corrosion resistance in waters, but is otherwise effectively identical. These alloys have the distinctive bright yellow colour normally associated with brass. They have the optimum combination of strength and ductility in the copper-zinc alloys, coupled with good corrosion resistance. C26000 is used for architecture, drawn and spun containers and shapes, electrical terminals and connectors, door handles, plumbers hardware. C26130 is used for tube and fittings in contact with water, including potable water.
C26800, Yellow brass, is the single phase alpha brass with the lowest content of copper. It is used where its deep drawing properties and lower cost give an advantage. When welded particles of beta phase may form, reducing ductility and corrosion resistance.
C35600 and C37000, Engraving brass, are 60/40 alpha-beta brasses with different levels of lead added to give free machining properties. They are widely used for engraved plates and plaques, builders hardware, gears. They should not be used for acid etched work, for which the single phase alpha brasses should be used.
C38000, Section brass, is a readily extrudable leaded alpha/beta brass with a small aluminium addition, which gives a bright golden colour. The lead gives free cutting properties. C38000 is available as extruded rods, channels, flats and angles, which are typically used in builders hardware.
C38500, Free cutting brass, is a significantly improved form of 60/40 brass, with excellent free cutting properties. It is used in the mass production of brass components where maximum output and longest tool life are required, and where no further cold forming after machining is required.
Australian Product Specifications
Phase Diagram & Mechanical Properties
Brasses are resistant to corrosion in many media. Please consult Austral Wright Metals for detailed advice on your application.
Brasses are particularly susceptible to corrosion by solutions containing ammonia or amines. Alloys with more than about 15% of zinc may suffer dezincification, which leaves a weak, porous corrosion deposit of copper. Resistance to dezincification is greatly reduced by the addition of a small amount of arsenic to the alloy.
Stress corrosion cracking, particularly by ammonia and amines, is also a problem with the brasses. Alloys containing more than about 15% zinc are most susceptible. Use of the annealed temper, and annealing or stress relieving after forming, reduces susceptibility to stress corrosion cracking.