Page 14 - Curriculum Visions Dynamic Book
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Cold-working
The alternative to hotworking is cold-working. It is done when the metal is too cold for new crystals to grow. Cold-working makes a metal harder and stronger, although it also becomes more brittle and so more liable to crack.
Casting
If the metal is to be made into a large, heavy object, such as the engine block of a car,
then it is usually cast. In this process molten metal is poured into a mould and the metal allowed to set. The mould is then broken open and the casting
removed and trimmed to an exact shape. Casting was well known in the Bronze
Age, and most finds from ancient sites are of castings. Castings are still used when a complicated object is needed, for example, door handles and locks.
(Above) All bells are cast. This is the Liberty Bell.
(Below) Fire hydrants are one of the most common objects in the street. They are made by casting.
(Left) The Statue of Liberty is a mixture of casting and cold-working of copper plate.
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