Copper and its Alloys

Bronzes

Tin Bronze and Phosphor Bronze

These alloys of copper and tin were the first metallic alloys to be developed by mankind, about four thousand years ago, and were used for coins, weapons, tools, jewellery and ornaments.  They revolutionised the way man lived leading to archaeologists naming the period the Bronze Age.

 In modern times wrought bronzes have been developed with 4-8% tin which are harder, stronger, and stiffer than wrought brasses and, in strip and wire form, are produced with a combination of high yield strength and good corrosion resistance.  The addition of small amounts (0.01-0.45%) of phosphorus increases the hardness, fatigue resistance and wear resistance, leading to their use in applications such as springs, bellows, flexible tubing, fasteners, masonry fixings, shafts, valve spindles, gears and bearings.

Alloying elements with copper, in this case tin and phosphorus, can result in lower electrical conductivity compared to pure copper.  The most widely used phosphor bronze for electrical purposes contains 0.2% phosphorus and 5% tin and has an electrical conductivity of 15% IACS (Copper is 100% IACS).  However, the combination of high yield strength, which gives a good contact force, and good corrosion resistance make this bronze ideal for a wide range of small electrical connectors, switches, current carrying springs and rotor bars.  These properties are retained at high operating temperatures.

Wrought leaded phosphor bronzes (3-4% lead) combine the above properties with outstanding machinability and significant self-lubrication, self-seating and alignment in bearing applications and excellent resistance to seizure.  Applications include thrust washers, bearing bushes, cams, clutch plates, intricate machined fasteners and other turned parts, clock and instrument parts, gears, pinions, pump and valve spindles and engraved components.

Phosphor bronzes with higher tin contents are available in all the common cast forms.  They have up to 13% tin and 2.5% lead (for machinability) and nickel (for strength and hardness) and are widely used for bearings and gears.

Bell Metal

A phosphor bronze with 20 to 24% tin has been used for centuries for the sand casting of bells of all types such as church bells, hand bells and ships' bells.  The bells are carefully machined and polished to give the exact notes required.  In the atmosphere, the bells will slowly patinate, which protects the surface from further corrosion, leading to a very long service life.

Aluminium Bronze  

These are alloys of copper with 5-12% aluminium, some having additions of iron, nickel, manganese and silicon, available in cast and wrought form. They are stronger than brasses or tin bronzes with better corrosion resistance due to a hard, adherent, protective alumina film (Al203).  They have an attractive golden colour, with very little tarnishing with time.  The major use for aluminium bronzes is in seawater applications, such as:

  • Fasteners
  • Pumps and valve components
  • Pipe fittings
  • Heat exchangers
  • Bearings
  • Propellers.
For marine applications they meet exacting Def Stan (Defence Standard) specifications (previously Naval Engineering Standard - NES), and are widely used for MOD applications.

 
The durability and golden colour makes aluminium bronze an attractive proposition for architects, for example as cast upright balustrades for the Sackler Crossing in Kew Gardens, London. The alloy used for this project was CuAl8Fe3; the balustrades were polished to the required finish and waxed in situ.

Silicon Bronze

This is an alloy of copper with 3% silicon and 1% manganese.  It has a good combination of strength, ductility, corrosion resistance and weldability.  It is used in architectural applications such as:

  • Door fittings
  • Railings
  • Church doors
  • Window frames
  • Hinges
  • Wall ties
  • Fastener material for marine applications.
The alloy is a firm favourite with sculptors and metalsmiths because of its workability, longevity and attractive golden bronze colour.

Silicon bronze is also widely used for marine hardware and fasteners such as bolts, clamps, screws, nuts, rivets and U bolts.

Manganese Bronze and Architectural Bronze

By composition these alloys are brasses but have picked up the ‘bronze’ name because of their colours. Manganese bronze CuZn40Mn1Pb1 (CW720R) is a brass used for architectural applications where the manganese leads to the formation of an attractive chocolate brown colour.

The term 'architectural bronze' is sometimes applied to a leaded aluminium brass CuZn41Pb1Al (CW620N) which, due to the aluminium, develops an attractive golden lustre.  Like all brasses, this alloy combines longevity with an aesthetic appeal which improves with time and gives a feeling of luxury and prestige to any building both inside and out.  It is available as profiles and rectangular bar and is used for window frames, cladding, doors and curtain walls.  It is usually finished by waxing to maintain the appearance.

Related ResourcesHere are related resources.  To browse and search all resources, visit the Resource Library.
    Pub 206 - Copper Alloys in Marine Environments
    £ 0.00
    Design and manufacture, Marine
    alloys, beryllium, brass, bronze, copper-nickel, corrosion, marine, property, resistance, seawater
    This publication focuses on the properties and corrosion resistance of a wide range of copper alloys used for seawater service - ranging from commercial grades of copper through copper-nickels, bronze,  brass and copper beryllium.  It allows the reader to understand potential types of corrosion mechanisms for the different alloy types and how to avoid them. 2012. 32pp.
    Pub 126 - Resistance to Wear of Aluminium Bronzes
    Design and manufacture, Marine
    alloys, bronze, property, resistance
    A chapter from Harry Meigh's book 'Cast and Wrought Aluminium Bronzes Properties, Processes and Structure' describing resistance to wear of aluminium bronze alloys. It also gives details of factors affecting wear and information on alloy selection. Pub 126.
    Pub 120 - Copper and Copper Alloys: Compositions, Applications and Properties
    £ 0.00
    Design and manufacture
    alloys, beryllium, brass, bronze, copper-nickel, coppers, Industry, manufacturing, nickel silver, property, standards
    Tables of BS EN series of standards with ranges of compositions and properties for coppers and copper alloys and equivalent old British Standard materials. Revision of TN10. 2004. 26pp.
    Pub 115 - Aluminium Bronze with Cast Stainless Steels and Ni-resist in Offshore Seawater Environments
    Design and manufacture, Marine
    alloys, applications, bronze, corrosion, offshore, property, seawater
    This report has collated data comparing the physical, mechanical and fabrication properties of cast nickel aluminium bronze (NAB), in particular NES 747 Part 2, with cast standard and super austenitic and duplex stainless steels and Ni-Resist for use in offshore sea water applications. 1996. 22pp.
    Pub 106 - Corrosion Resistance of Copper and Copper Alloys
    Marine
    alloys, brass, bronze, copper-nickel, coppers, corrosion, nickel silver, resistance
    This large table gives information on the suitability of copper and copper alloys with many different chemicals. Data is given for copper, brass, copper-nickel, aluminium bronze and gunmetals at three temperatures and shows if specific materials can be used with chemicals giving an indication of corrosion resistance. 5pp.
    Pub 086 - Aluminium Bronze, Essential for Industry
    Design and manufacture, Marine
    alloys, bronze, corrosion, Industry, property, resistance, welding electrodes
    Illustrated 8-page leaflet highlighting the main attributes of the important aluminium bronzes including selection criteria, properties, corrosion resistance, welding and machining. 1989. 16pp.
    Pub 085 - Welding Aluminium Bronze
    Design and manufacture, Marine
    alloys, bronze, welding electrodes
    Describes the essential features of good welding practice in relation to the aluminium bronze alloys. 1980. 12pp.
    Pub 083 - Aluminium Bronze Alloys for Industry
    Design and manufacture, Marine
    alloys, applications, bronze, Industry, property
    Describes the properties, applications and fabrication of aluminium bronze alloys. 1986. 24pp.
    Pub 082 - Aluminium Bronze Alloys Technical Data
    Design and manufacture, Marine
    alloys, bronze, property, technical
    Physical and mechanical properties at low, ambient and elevated temperatures are provided for wrought and cast aluminium bronze alloys. 1981. 93pp.
    Pub 081 - Designing Aluminium Bronze Castings
    Design and manufacture, Marine
    alloys, bronze, design, designer
    Reprint of an article published in ‘Engineering’ August 1982 (Tech file 116). The advantages of aluminium bronze casting alloys are discussed with advice on how various design criteria affect casting quality. 1983. 22pp.
    Pub 080 - Aluminium Bronze Corrosion Resistance Guide
    Design and manufacture, Marine
    alloys, applications, bronze, corrosion, resistance
    Survey of published and other information relating to aluminium bronzes in a number of environments. Recommendations are made for materials suitable for many applications. 1981. 30pp.
    Pub 040 - CW451k PB102 Data Sheet
    Design and manufacture
    alloys, bronze, property
    Contains physical and mechanical properties of wrought 5% tin phosphor bronze, PB102. 1969. 12pp.
    Cast and Wrought Aluminium Bronzes
    Design and manufacture, Marine
    alloys, bronze, corrosion, design, manufacturing, property, resistance
    This book, commissioned by CDA, updates information contained in the standard reference work by P J Macken and A A Smith, published in 1966. It contains valuable new material on the metallurgy of aluminium bronzes, the composition and manufacturing conditions required to ensure reliable corrosion resistance - also, alloying elements, physical properties, casting processes, properties of castings, manufacture and design of castings. 1999. 434pp.

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Bells at Whitechapel Foundry
Bronze handrail
1500mm butterfly valve in aluminium bronze (Courtesy Severn Leeds Valve)
Bronze propeller
Aluminium bronze balustrades on Sackler Crossing, Kew Gardens, UK (Courtesy Copper Alloys Ltd)
Silicon bronze rigging toggle for mast support
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