SUBJECT:� BASIC TECHNOLOGY
WEEK SIX AND SEVEN
TOPIC:� IDENTIFICATION OF METALS
DEFINITION OF METAL
METAL is a type of solid mineral substance that is usually hard and shiny. It conducts heat and electricity can travel through it.
Metals have characteristics which are different from those of the non-metals such as wood, plastics ceramics, rubber etc�
PROPERTIES OF METAL
Metals can be identified by the following physical properties:
CLASSES OF METAL
The metals used in engineering can be classified into categories�
FERROUS METALS AND THEIR ALLOYS
This group of metals contains iron. The metals are, therefore, magnetic. Examples include wrought iron, cast iron and various grades of steel.�
NON-FERROUS METALS AND THEIR ALLOYS
This group of metals have no iron . These metals are therefore not magnetic.� Examples are aluminum, copper, brass etc.
Most metals do not occur in a pure state. They are usually combined with other metals and earthly impurities to form what is called mineral ore. The ore is then mined and processed to extract the metal of interest. The extraction process differs from metal to metal.
Casting is the process of melting and pouring molten metal into� the� mould to take the shape of the mould when it cools down or solidifies.
Smelting is the process of extracting metals from iron-ore dug from the ground .
Annealing is the process by which metals can be softened.
USES OF METAL
65%copper and� 35%zinc�
80% copper and � � 20 % zinc
Polishes well and no corrosion�
78% copper and � 22% zinc
Louder in sound than other metals
Cast iron in the manufacturing� of machine parts , pipes, radiators, stoves, engine blocks
Carbon steels are used� in the manufacturing of the automobile bodies gears, hacksaws ,hammers ,drill, knives
Alloy steels are used in the manufacturing of cables, steels, rail, wires , springs , shoves, ball-bearing, chisels� etc.�
The wrought iron is used in the manufacturing of nails ,horse shoes, pipe ,wires, roofing sheets
Aluminium is used� for manufacturing aircraft, cooking pots for its lightness.
Copper is used for making� telephone wires, water heater, pipes ,electric cables.
Zinc� is used for the coating of iron and steel as a protection against rusting .It is used for wire-fence ,water tank reservoir� ,bucket.��
Brass is for making musical instrument screws clocks.�
Silver is for ornament work ,mirror .
Nickel is used� for plating iron and materials to give a shining slivering appearance . It is also used for making cooking pots and sauce pan.
Lead is used for making lead pipes , storage batteries , chemicals and cover electric cables.
Tin is used for making engine bearing, ball-bearing� medals, coins , statues and collapsible tubes.
Read on Identification of Ceramics, Plastics and Rubber from Introductory Technology (JSS1) by Evans.� Pages 32-35
(a)� aluminium (b) copper (c)� steel (d) brass
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