Copper and Copper Alloys
Copper and copper alloys are one of the major groups of commercial
metals. They offe r
a wide range of properties, including excellent electrical and
thermal conductivity, outstanding corrosion resistance, good
strength and fatigue resistance, and appearance. They can be readily
worked, brazed and welded.
Selection of Copper and Copper Alloys
The primary selection criteria for copper and copper alloys include:
● Electrical conductivity: copper has the highest conductivity of
the engineering metals. Silver or other elements may be added to
increase strength, softening resistance or other properties without
major loss of conductivity.
●Thermal conductivity: this property is similar to electrical
conductivity. Alloys of copper may be used for this property, where
good corrosion resistance compensates for loss of conductivity with
increased alloying.
●Colour and appearance: many of the copper alloys have a distinctive
colour, which may change as the object weathers. For most of alloys
it is easy to prepare and maintain the surface to a high standard,
even in adverse corrosion conditions. Many of the alloys are used in
decorative applications, either in their native form or after metal
plating. The alloys have specific colours, ranging from the salmon
pink of copper through yellow, gold and green to dark bronze in the
weathered condition. Atmospheric exposure can produce a green or
bronze surface, and prepatinated alloys are available in some
product forms.
●Ease of fabrication: most of the alloys can be easily cast, hot or
cold formed, machined, joined etc.These alloys are often the
standard against which other metals are compared.
Different Types of Metal Alloys
1. Copper are essentially commercially pure copper, which ordinarily
is very soft and ductile, containing up to about 0.7% total
impurities. These materials are used for their electrical and
thermal conductivity, corrosion resistance, appearance and colour,
and ease of working. They have the highest conductivity of the
engineering metals and are very ductile and easy to braze, and
generally to weld. Typical applications include electrical wiring
and fittings, busbars, heat exchangers, roofs, wall cladding, tubes
for water, air and process equipment.
2. High copper alloys contain small amounts of various alloying
elements such as beryllium, chromium, zirconium, tin, silver,
sulphur or iron. These elements modify one or more of the basic
properties of copper, such as strength, creep resistance,
machinability or weldability. Most of the uses are similar to those
given above for coppers, but the conditions of application are more
extreme.
3. Brasses are copper zinc alloys containing up to about 45% zinc,
with possibly small additions of lead for machinability, and tin for
strength. Copper zinc alloys are single phase up to about 37% zinc
in the wrought condition. The single phase alloys have excellent
ductility, and are often used in the cold worked condition for
better strength. Alloys with more than about 37% zinc are dual
phase, and have even higher strength, but limited ductility at room
temperature compared to the single phase alloys. The dual phase
brasses are usually cast or hot worked. Typical uses for brasses are
architecture, drawn & spun containers and components, radiator cores
and tanks, electrical terminals, plugs and lamp fittings, locks,
door handles, name plates, plumbers hardware, fasteners, cartridge
cases, cylinder liners for pumps.
4. Bronzes are alloys of copper with tin, plus at least one of
phosphorus, aluminium, silicon, manganese and nickel. These alloys
can achieve high strengths, combined with good corrosion resistance.
They are used for springs and fixtures, metal forming dies,
bearings, bushes, terminals, contacts and connectors, architectural
fittings and features. The use of cast bronze for statuary is well
known.
5. Copper nickel are alloys of copper with nickel, with a small
amount of iron and sometimes other minor alloying additions such as
chromium or tin. The alloys have outstanding corrosion resistance in
waters, and are used extensively in sea water applications such as
heat exchangers, condensers, pumps and piping systems, sheathing for
boat hulls.
6. Nickel silvers contain 55 – 65% copper alloyed with nickel and
zinc, and sometimes an addition of lead to promote machinability.
These alloys get their misleading name from their appearance, which
is similar to pure silver, although they contain no addition of
silver. They are used for jewellery and name plates and as a base
for silver plate (EPNS), as springs, fasteners, coins, keys and
camera parts.
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