The story of metal casting begins some five and a half thousand years ago in Mesopotamia, the cradle of civilisation. The process, which involves pouring molten metal into a mould, was used by the Mesopotamians to create all manner of things including tools and weaponry, typically out of the copper — tin alloy, bronze. Civilisation had finally dragged itself out of the Stone Age and metal casting was to play a significant role.
Within a thousand years the Bronze Age had spread to most corners of the globe. There is evidence that the Egyptians had invented bellows that allowed them to heat metal to temperatures previously unattainable. These primitive devices were capable of pumping hot air into furnaces, revolutionising the way metal was worked and cast.
The Bronze Age saw the process of metal casting evolve dramatically too. Early methods simply involved pouring molten metal into open stone moulds, meaning one side of the cast object would always be flat. By 2000 BC, the lost-wax shaping technique, whereby a wax mould that is later removed is used to create cavities, had been developed to counter this issue. Rather remarkable, intricate statues and bronze figurines exist from this period.
Metal casting is an age old profession.
Human’s first attempt to cast iron dates back to around 1,700BC. As it is oxidised in its natural form on Earth, it took early civilised man a little longer to discover its potential. There is evidence from this period, however, that the Hittite empire was using a primitive batch method furnace to deoxidise iron sand. Casting of iron in Europe however did not take off until much later, with forging in blacksmiths the go-to method of iron working until well into the 14th century.
Pig iron (which has a lower melting temperature than iron) casting was used in China from the 7th century by melting high carbon iron. Like the Egyptians, the Chinese utilised heating technology including bellows to achieve the still relatively high temperatures (around 1,150°C) required to cast pig iron. The problem with pig iron was its brittleness; perhaps another factor iron casting didn’t take off in Europe until the 14th century.
Brittle pig iron was largely the only type cast until the industrial revolution in the 18th century. There is evidence in the middle ages of Church doors cast of the material, although the finished products were often of low quality and required numerous rework and reinforcement. Another example of iron casting from the period is the very first cast iron pipe at Dillenburg Castle in Germany in the middle of the 15th century.
By the 18th century foundries were beginning to spring up across Europe and the USA and the casting of iron began to truly take off. An Englishmen, Abraham Darby, was the first man to use coke in his iron furnace whilst a French Scientist, René Antoine Ferchault de Réaumur, invented European Whiteheart, the first malleable iron.
The period between the start of the Industrial Revolution and turn of the 20th century was one of exciting and fast paced technological advances in the casting industry. Notable invents include the first casting steel using the crucible process, the opening of the first commercial steel plants and the development of metallography soon meant high quality iron and steel casts were being mass produced across the globe. The American forging companies led the way although the Europeans and Japanese were never far behind.
The pace did not slow down as the 19th century gave way to the 20th. Electricity became an integral part of the casting process, truly stainless steel was developed and the automobile industry took off in the USA, Europe and Japan. Two World Wars further changed the shape of the metal industry, with Japan emerging at the front runners as they struggled to re-build post 1945.
Metal casting has changed over time.
As the 20th century progressed the quality of worked metal began to take precedence. The Americans had to learn from the Japanese way of working (think Kanban, Six Sigma and JIT) and US powerhouses such as Ford and GM sent managers over to the East to take lessons in quality and lean manufacture.
In the past three decades, quality has become the standard and an emphasis on clean manufacturing has taken centre stage. Green industrial initiatives have been passed across the globe meaning governments and industries have been forced to rethink how they cast metal. The rethink has achieved remarkable results; electromagnetic casting was developed in 1997, dramatically reducing the cost and carbon footprint of the casting process.
And the future? The industry is currently striving to minimise the footprint of the process by innovating new, clean and cheap ways of working metal. Watch this space, there is sure to be lots to come.