A water cooled mould from a continuous casting machine, c 1970.
© Science Museum / Science & Society Picture Library
This machine was used for the casting of iron universal beam blanks. Cast iron is an iron alloy which normally contains between 1.8 and 4.5 % carbon by weight. It is made by melting pig iron, which has the effect of removing impurities, and is then cast in moulds to the desired shape. It can alternatively be poured into moulds directly from a blast furnace. The high carbon content tends to make cast iron somewhat brittle and prone to crack under tension.