Copper and its Alloys

Today, over half of the copper produced is used in electrical and electronic applications and this leads to a convenient classification of the types of copper into:

  • Electrical (high conductivity)
  • Non-electrical (engineering).

High Conductivity Coppers (Electrical)

Wrought high conductivity copper has excellent ductility and, as a result, is available in forms such as wire, tube, extrusions, bar and sheet.

The main grade of copper used for electrical applications such as building wire, motor windings, cables and busbars is electrolytic tough pitch copper CW004A (was C101) which is at least 99.90% pure and has an electrical conductivity of at least 101% IACS minimum.  Tough pitch copper contains a small % of oxygen (0.02 to 0.04%) so if the high conductivity copper is to be welded or brazed or used in a reducing atmosphere, then the more expensive oxygen free high conductivity copper CW008A (was C103) may be used.

Wrought high conductivity coppers (CW004A and CW008A) can only be strengthened and hardened by cold working such as occurs on cold drawing or bending (typically tensile strength 250N/mm2 with 12% elongation). They cannot be strengthened by heat treatment so, if a stronger grade of high conductivity copper is required, then small amounts (less than 1%) of alloying elements such as silver, cadmium, magnesium or tin are used.  These additions give solid solution hardening and contribute to work hardening when the alloys are cold drawn into wires or tubes or rolled into sheet. However, there is a small loss of conductivity. These alloys, with 90 to 100% IACS values are typically used for overhead conducting and catenary wires on railway and tram systems to transmit electric current to the electric motors of trains and trams. 

High conductivity copper may also be produced as die and sand castings (CC040A), typically for electrical switchgear and electrode holders.

The electrical conductivity of castings may be slightly lower than in wrought copper, however a minimum value of 93% IACS is guaranteed but values up to 100% are reached.

For detailed information on properties and applications:
Publication 122 - High Conductivity Coppers for Electrical Engineering.

Higher Strength Alloys

Small additions of silver, cadmium, magnesium or tin are used to give a small increase in the strength of copper conductors but, for significant increases in strength, the heat treatable copper chromium (0.5-1.2% Cr) and copper chrome zirconium (0.1% Zr) alloys have been developed in cast and wrought form. These alloys combine high strength (tensile strength 450N/mm2 with 10% elongation, up to 400oC) with high electrical conductivity (75 to 78% IACS) and high thermal conductivity. The properties of these alloys are developed by a heat treatment process which involves heating to 950-1000oC (solution treatment), followed by water quenching then reheating to 425-500oC (precipitation hardening). In addition to this heat treatment wrought alloys are strengthened by cold working. Applications for these alloys include resistance welding electrodes, switchgear, heat sinks, current carrying arms and steel casting moulds where copper would be ideal from the electrical and thermal conductivity standpoint but is simply not strong enough.

For detailed information on properties and applications:
Publication 122 - High Conductivity Coppers for Electrical Engineering
BS EN 50149:2012 Railway applications. Fixed installations. Electric traction. Copper and copper alloy grooved contact wires.

Free Machining Copper

An addition of approximately 0.5% tellurium or sulphur raises the machinability rating from 20% to 90%, based on a scale where free machining brass is rated at 100%. The particles of copper telluride or copper sulphide act as chip breakers leading to excellent machinability without substantially affecting the electrical conductivity which is rated at 93% IACS. Free machining copper is used where a large amount of repetitive machining at high rates is required. One example is in the production of gas, laser and plasma cutting nozzles which involves the drilling of small holes in rods followed by cold forming to the finished shape. Other applications include screws, fasteners, contacts, connectors, clamps and bolts used in the electrical and semi-conductor industries.

Further information:
Publication 122 - High Conductivity Coppers for Electrical Engineering
Publication 44 - Machining Brass, Copper and its Alloys

Engineering Copper (Non-Electrical)

The usual grade of copper used for engineering applications is CW024A (was C106). Many of the applications of copper depend upon properties other than its high electrical conductivity.

The properties which make copper the standard material for engineering, including architecture and plumbing, are:

  • Thermal conductivity - the thermal conductivity of copper, 394W/mK, is about twice that of aluminium and thirty times that of stainless steel. This means that copper is used for components where rapid heat transfer is essential. Examples include saucepan bottoms, heat exchangers, car and vehicle radiators and heat sinks in computers, disk drives and TV sets.
  • Corrosion resistance - copper is non-reactive and does not rust or become brittle in sunlight.
  • Ease of joining - by brazing or soldering. The latest technology called CuproBraze® is used to fabricate strong and reliable brazed copper/brass heat exchangers for cooling in vehicles which include cars, trucks, locomotives, tractors and JCBs.
  • High ductility - tubes are easily bent even when hard
  • Toughness - does not become brittle at sub zero temperatures
  • Heat resistance - withstands fire well, melting point is 1083oC
  • Antimicrobial - copper is a naturally hygienic metal which slows down the growth of harmful germs such as E.Coli, MRSA and legionella. Copper's ease of shaping, corrosion resistance and antimicrobial properties make it ideal for brewing vessels.
  • Range of colours and malleability - widely used by designers and architects for exterior and interior applications.
  • Recyclability - copper is 100% recyclable without loss of properties. The price of scrap copper is high.
High Conductivity Copper for Electrical Engineering

Copper-based Electrical Conductivity Alloys

This section introduces coppers and copper alloys for conductivity applications and provides details of properties and uses.

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Related Resources

Here are related resources.  To browse and search all resources, visit the Resource Library.

    Pub TN44 - Machining Brass, Copper and Copper Alloys
    £ 0.00
    Design and manufacture
    alloys, brass, coppers, design, Industry, machining, manufacturing
    Detailed advice on machining as a production technique. Guidance on materials selection where good machinability is important. Basic information and guidance for those who know what material is to be machined. Advice on the selection of cutting fluids. 1992. 65pp.
    Pub TN27 - High Conductivity Coppers: Technical Data
    Electrical systems
    alloys, conductivity , coppers, electrical, property, standards, technical
    These data sheets, originally published in a series from 1968 - 1972, cover all the main coppers and copper alloys. They contain an invaluable summary of data relating to the physical and mechanical properties of the materials at low, ambient and elevated temperatures which is not available elsewhere.
    Pub 223 - Copper for Contacts
    Electrical systems
    alloys, applications, contacts, coppers, electrical
    This publication looks at the properties required for contact materials, and to identify those applications in which copper or copper alloys have special advantages. 1980, revised 2015. 36pp.
    Pub 121 - Copper - The Vital Metal
    £ 0.00
    coppers, alloys, applications, history, schools
    An illustrated introduction to the history, metallurgy, production, and applications of copper and copper alloys. (Revision of Book 1). 1998. 42pp.
    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 106 - Corrosion Resistance of Copper and Copper Alloys
    gunmetal, 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 094 - Equilibrium Diagrams
    Design and manufacture
    coppers, alloys, property
    Industrially important copper alloy systems are discussed in terms of the relationship between their microstructure and properties and the relevant equilibrium diagram. 1993. 36pp.
    Pub 022 - Copper for Busbars - Guidance on Design and Installation
    £ 0.00
    Energy and renewables, Electrical systems
    busbars, coppers, design, electrical, installation
    This 2014 update of a classic, 1936 publication provides the information needed to design efficient, economic and reliable busbar systems.
    Microstructures of Copper and Copper Alloys
    Design and manufacture
    coppers, alloys
    Photo micrographs of commercially important and/or metallurgically interesting copper and copper alloys and processings (on the CDA Inc site).
    DKI i.18 Recommended Machining Parameters for Copper and Copper Alloys
    Industrial, Design and manufacture
    alloys, brass, coppers, machining
    This update by DKI aims to address the concerns of practitioners, helping them to find the most effective and economical solutions to their metal cutting problems. It also assists designers and development engineers when comparing the machinability of different materials, making it easier to estimate the fabrication costs of a particular part. Tables have been brought up to date to reflect the most recent materials standards. 2010. 64pp.
    Copper Key
    Design and manufacture
    alloys, coppers, standards
    Online software giving chemical composition of copper alloys worldwide, their material designation and national standard. Automatically gives equivalent materials from international, European and other national standards and enables chemical compositions to be compared (on the German Copper Centre site).
    CDA Inc Technical Reference Library
    Design and manufacture
    alloys, coppers, technical
    The US Copper Development Association provides access to its Technical Reference Library free of charge in an effort to increase knowledge of the role of copper in the environment.
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