COPPER
COPPER
Unlike other common metals,
the various types of copper are better known by name then by code number.
Electrolytic tough-pitch copper is susceptible to embrittlement when heated in
reducing atmosphere, but it has high electrical conductivity. Deoxidized copper
has lover electrical conductivity but improved cold working characteristics,
and it is not subject to embrittlement. It has better welding and brazing
characteristics than do other grades of copper. Oxygen free copper has same
electrical conductivity as tough pitch copper and is not prone to embrittlement
when heated in a reducing atmosphere.
Modified copper
include tellurium copper, which contains 0.5% tellurium for free cutting
characteristics (selenium and lead are also used for this purpose), and
tellurium-nickel copper, an age hardenable alloy that provides high strength.
BACKGROUND:
Copper smelting
appears to have been developed independently in several parts of the world. In
addition to its development in Anatolia by 5000 B C, it was developed in china
before 2800 BC, in the Andes around 2000 BC, in Central America around 600 AD,
and in West Africa around 900 AD. Copper is found extensively in the Indus
valley civilization by 3rd millennium BC. In Europe Otzi the iceman,
a well-preserved male dated to 3200 BC, was found with an axe tipped with
copper that was 99.7% pure. High levels of arsenic in his hair suggest he was
involved in copper smelting.
Properties of Copper:
Copper has a high
electrical and thermal conductivity, second only to silver among pure metals at
room temperature. Copper is a reddish-colored metal. It has its characteristic
color because of its band structure. In its liquefied state, a pure copper
surface without ambient light appears somewhat greenish, a characteristic
shared with gold. When liquid copper is in bright ambient light, Its retains
some of its pinkish luster.
Copper occupies the
same family of the periodic table as silver as gold, since they each have one
s-orbital electron on top of a filled electron shell. This similarity in
electron structure makes them similar in many characteristics. All have very
high thermal and electrical conductivity, and all are malleable metals.
Copper has been the
most common alloying element almost since the beginning of the Aluminium
industry, and a variety of alloys in which copper is the major addition were
developed. In the cast alloys the basic structure consists of cored dendrites
of aluminium solid solution, with a variety of constituents at the grain
boundaries or interdendritic spaces, forming a brittle, more or less continuous
network of eutectics. Wrought products consist of a matrix of aluminium solid
solution with the other soluble and insoluble constituents dispersed within it.
Physical properties of copper:
Density (near room temp) (g cm-3) 8.96
Melting point (0C) 1084
Boiling point (0C) 2562
Heat capacity (j mol-1 k-1) 24440
Crystal structure F.C.C
Thermal conductivity (W m-1 k-1) 401
Brinell hardness (Mpa)
874
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