Transcript Non-Ferrous Metals and their alloys. Non

Non-Ferrous Metals and their alloys.
Non-ferrous metals are those which do not contain iron. In general they have excellent
resistance to corrosion. Copper, reputed to be the first metal used by mankind, includes some
very useful and interesting properties, it is malleable and ductile. It is for this reason is was of
such interest to our ancestors. Another non-ferrous metal, aluminium, has only featured in
engineering terms in the last 75 years.
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Copper
Copper as an engineering metal came to prominence during the industrial revolution, up to
then it was considered only for its decorative value and utensils value and on roofing.
Properties of copper include
• Malleability - the ability to be beaten or rolled into shape.
• Ductility - The ability to be drawn into shape as in the manufacture of copper wire.
• Copper is a good conductor of heat and electricity.
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• Copper production in modern times
Copper production has a strong link with an Irishman called Marcus Daly, from Co. Cavan.
As a consequence of his mining in Montana USA he was the first to exploit the metal
when he sent a shipment to Wales for smelting just at the time when it was becoming a
prominent metal in the electrical industry. He was really trying to find a better use for the
mineral which was a by-product of the silver mines in the region.
Copper ore Copper matte
Reverberatory furnace
Blister Copper
Converter Furnace
pure copper
Electrolysis
Flowchart of copper ore to pure copper
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Copper production
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The production of copper.
There are three distinct stages to the production of copper;
1 Copper ‘Matte’ - The first stage of the production of copper is with matte. It is a mixture of
30% to 40% copper. Ore is first concentrated at the mining site by crushing and then
leaching or floatation.
The ore is then roasted or smelted in an oil fired furnace at a temperature below the melting
point of copper, [1083oC]
The resultant matte contains high levels of sulphur and iron from the chalcopyrite (Cu Fe S2)
2 Converting - Iron and sulphur are removed by blowing air through the molten matte in a
converter vessel, similar to the Bessemer converter. The matte is placed in the converter
and held at the temperature for about 8 hours.Blowing continues until only copper
sulphide remains. This is what is referred to as ‘Blister Copper’. It is up to 99% pure. This is
then refined by further heating to remove the oxygen. It is then cast into ingots known as
‘Anodes’.
3. Refining by Electrolysis: - For copper to be used in the electrical industry it has to have
99.99% purity. This can only be achieved by electrolytic refinement.
Pto.
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Refined blister copper anodes are attached to the positive DC supply, while a thin cathode
plate is connected to the negative supply. An electrolyte, a mixture of copper sulphate and
sulphuric acid at 50O C is poored into the tanks.
Acurrent density of around 200 amps is passed between the anode and the cathode,
depositing pure copper onto the thin cathodes
Application of copper
Over half of all copper produced is used in the electrical industry. Copper wire for
transmission accounts for a large amount of this use.
Central heating and plumbing are the major applications of copper. Cylinders, copper piping
etc are the most widely used.
Recycling of copper is an industry in itself and accounts for 40% of all copper used.
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Aluminium
Aluminium is one of the most versatile of metals. It is only of engineering significance since
the late twenties, when it became possible to produce it in commercial quantities. Next to
steel it is the most used metal in the world. Yet the production of aluminium is only 6% that of
steel.
Aluminium has a wide range of uses, from cooking foil to aircraft. Its properties make it
suitable for many applications. It is light does not corrode, is a good conductor of electricity
and heat and is cheaper than copper.
Aluminium can be cast, extruded, rolled, forged, drawn,etc., to give us the numerous shapes
of the aluminium objects that we see everyday.
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Mining
Aluminium is the most abundant metal on the earth’s crust. About 8% of the earth’s crust is
made up of aluminium.
So why is it not the most abundant metal in use? There is great difficulty and cost attached to
refining aluminium. It does not exist as a pure metal in nature, but is combined with other
elements. The Ore of aluminium is called ‘Bauxite’,[hydrated aluminium oxide].
Bauxite is mined in many countries, France, Australia, Guinea, Brazil, Russia and china being
the more common.
Mining Methods;Open-cast mining is carried out using very large scale plant. After the overburden of topsoil is
removed the ore is excavated out and loaded into giant dumper trucks. The ore is crushed and
washed close to the mining site to save on transport costs.
Production of Aluminium from Barxite;It requires a huge amount of energy to extract aluminium from its ore. The energy is supplied
in the form of electricity. Because of the large amount of electricity involved the production
of aluminium is generally in countries with large amounts of cheap electricity, such as Canada,
Norway and Brasil.
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A Two-stage process.
Purification;Before aluminium can be made the ore has to be purified. After being mixed with caustic soda
solution the bauxite is sent to heated pressure vessels where the alumina hydrated aluminium
oxide dissolves in the caustic soda. The impurities are removed as red mud. As the alumina
cools alumina hydrate forms crystals. It is then roasted or calcined. In the Bayer process. This
process is what is carried out in Aughinis in the Shannon Estuary outside Limerick.
Reduction of Alumina to Aluminium;Electrolysis is used to convert alumina to aluminium. Alumina has a melting point of 2000oC.
To reduce the temperature at which conversion takes place cryolite is added and hence
reduces the amount of energy required to convert the alumina to aluminium.
It takes about 2 tonnes of alumina , 15000 units of electricity to make one tonne of
aluminium.
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Recycling of Aluminium
Recycling accounts for about 25% of the total world production of aluminium.
As the amount of bauxite is limited, it makes good sense to recycle the metal. The cost of
recycling a tonne of aluminium is 5.3% the cost of its initial production.
Aluminium and its uses;
Aluminium is often used in transmission cables for high tension systems in place of copper
because of cost factors. It is also better in national grid transmission because of the reduction
of weight.
Aluminium is often alloyed with other metals such as copper, magnesium, nickel and zinc to
produce metals with special properties.
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Lead
Lead is one of those metals which have been used for many ages. The Romans used lead to
duct water to their baths. Batteries are the main users of lead nowadays as it has found to be
dangerous in many other applications. Petrol used lead to aid the lubrication of the fuel
system.
Lead is a toxic material and is being replaced by other materials in places like drainpipes,
guttering etc.
Lead-tin alloys of solder are essential to the electrical industry and are known as softsolders(approx 60%tin-40% lead). Other uses of lead include the sheathing of underground
telecommunication cables, bearing matals, radiation protection shields (X-ray and Nuclear).
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Tin
Tin is mainly used in the production of tinplate( sheet steel coated in tin for corrosion
protection.
Tin was mined mainly ion Britain in Cornwall which attracted the Romans to Britain.
Tinplate is produced by dipping sheet steel into baths of molten tin. The canned or tinned
food industry is based on the tinplate can. The tin makes up just 1% of the tincan.
Zinc
Zinc is a white silvery metal which is a poor conductor of both electricity and heat. It is mostly
used as a source of protecting steel I the form of galvanised steel. It is usually applied by hotdipping the steel in vats of molten zinc, But is also applied by electroplating.
Zinc is used in dry-cell batteries such as those for torches and radios etc. It is alloyed with
other metals to make die castings.
One of its main uses is its alloy with copper to make brass.
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