Cast Iron - History

History

The earliest cast iron artifacts date to the 5th century BC, and was discovered by archaeologists in what is now modern Luhe County, Jiangsu in China. Because cast iron is comparatively brittle, it is not suitable for purposes where a sharp edge or flexibility is required. It is strong under compression, but not under tension. Cast iron was invented in China in the 5th century BC and poured into moulds to make ploughshares and pots as well as weapons and pagodas. Although steel was more desirable, cast iron was cheaper and thus was more commonly used for warfare in ancient China.

In the west, where it did not become available till the 15th century, its earliest uses included cannon and shot. Henry VIII initiated the casting of cannon in England. Soon, English iron workers using blast furnaces developed the technique of producing cast iron cannons, which, while heavier than the prevailing bronze cannons, were much cheaper and enabled England to arm her navy better. The ironmasters of the Weald continued producing cast irons until the 1760s and armament was one of the main uses of irons after the Restoration.

Cast iron pots were made at many English blast furnaces at the time. In 1707, Abraham Darby patented a method of making pots (and kettles) thinner and hence cheaper than his rivals could. This meant that his Coalbrookdale furnaces became dominant as suppliers of pots, an activity in which they were joined in the 1720s and 1730s by a small number of other coke-fired blast furnaces.

The development of the steam engine by Thomas Newcomen provided further market for cast iron, since cast iron was considerably cheaper than the brass of which the engine cylinders were originally made. John Wilkinson was a great exponent of cast iron, who, amongst other things, cast the cylinders for many of James Watt's improved steam engines until the establishment of the Soho Foundry in 1795.