Akademik

Bessemer was the son of a mechanical engineer who had fled from the French Revolution. After leaving the village school in Charlton, where he was born, he worked as a type-caster, until the family moved to London in 1830. At the age of 17 he set up his own business to produce metal alloys and bronze powder. In 1843 he had an idea that made his fortune. On purchasing some ‘gold’ paint (made of brass) for his sister he was horrified at its high price. He designed an automatic plant to manufacture the paint and made sufficient money to pursue a career as a professional inventor.

During the Crimean War (1853–56) Bessemer invented a new type of gun with a rifled barrel. To manufacture the gun he needed a strong metal that could be run into a mold in a fluid state. At that time cast iron (pig iron) contained carbon and silicon impurities, which made it brittle. Wrought iron, which was relatively pure, was made by a laborious process of refining pig iron. The temperature of the furnace, while sufficient to melt the pig iron, was not sufficient to keep the purer iron molten. The refined metal was extracted in lumps after which it was ‘wrought’. Bessemer proposed burning away the impurities by blowing air through the molten metal. The Bessemer converter that he invented is a cylindrical vessel mounted in such a way that it can be tilted to receive a charge of molten metal from the blast furnace. It is then brought upright for the ‘blow’ to take place. Air is blown in through a series of nozzles at the base and the carbon impurities are oxidized and carried away by the stream of air.

Bessemer announced his discovery in 1856. At first his idea was accepted enthusiastically and within weeks he obtained £27,000 in license fees. However, though the process had worked for him, elsewhere it failed dismally because of excess oxygen trapped in the metal, and because of the presence of phosphorus in the ores. (By chance Bessemer's ore had been phosphorus-free.) His invention was dropped and Bessemer found himself the subject of much ridicule and criticism. Bessemer established his own steelworks in Sheffield (1859) using imported phosphorus-free iron ore.

Robert Mushet (about 1856) solved the problem of the excess oxygen by the addition of an alloy of iron, manganese, and carbon to the melt. Bessemer's process then worked provided nonphosphoric ores were used, but it took much time and determination to convince ironworkers after the initial failure. The invention eventually reduced the price of steel to a fifth of its former cost, made it possible to produce it in large quantities, and made possible its use in a variety of new products. The problem of dealing with the phosphorus impurities was solved in 1878 by Sydney Gilchrist Thomas and Percy Carlyle Gilchrist. Bessemer retired a rich man in 1873.