Copper
 Copper has a superior electrical conductivity to all
metals other than silver and it has a very high thermal conductivity
too. It can be worked very easily making it the material of choice for
many applications. Its ability to form a protective oxide film with an
attractive green patina has also made it the material of choice for many
constructional applications, particularly roofing. Example of copper
roofs can be seen throughout Britain today.
In its naturally ‘pure’ state there is always some
degree of impurity. The high conductivity pure copper used for the
production of bus-bars etc. is, as a rule, 99.9% minimum pure, the
impurities being silver and oxygen. These impurities do have their
drawbacks. The oxygen content causes an adverse reaction at high
temperature, and this makes operations such as welding more difficult,
and so phosphorus is often added to de-oxidise the copper, making it
more suitable for applications where brazing or welding is involved.
The softness of ‘commercially pure’ copper makes it a
difficult metal to machine. Of course, in it’s more highly alloyed state
(particularly with the addition of zinc and lead to form free cutting
brass, against which almost all other metals are indexed for their
machinability) this is not a problem, but to retain the higher
conductivity of copper or its aesthetic appearance, the addition of
sulphur gives a greatly increased cutting ability, to as high as 80% on
the machinability index.
Alloy specifications
During the late 1990s a new series of BS EN standards was brought in for
all copper and copper based alloys (i.e. bronze). The new series of
standards brought with it a new system for describing products.
The system described products in two ways, one using
symbols the other using numbers. The symbol system follows the ISO
compositional system and a brass made up of a 63/37 ratio of copper and
zinc is shown as CuZn37.
The numbering system is six-character alpha numeric
system with two characters (the first of which will be ‘C’ for copper)
followed by three numbers and a letter. Using this system C101 has
become CW004.with the W denoting that this is a wrought product.
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