ALTHOUGH he is best known for developing a way to mass-produce steel, Henry Bessemer was a prolific British inventor. In the 1850s in Sheffield his converters blasted air through molten iron to burn away impurities, making steel the material of the industrial revolution. But Bessemer knew he could do better, and in 1865 he filed a patent to cast strips of steel directly, rather than as large ingots which then had to be expensively reheated and shaped by giant rolling machines.
Bessemer’s idea was to pour molten steel in between two counter-rotating water-cooled rollers which, like a mangle, would squeeze the metal into a sheet. It was an elegant idea that, by dint of having fewer steps, would save time and money. Yet it was tricky to pull off. Efforts to commercialise the process were abandoned.
Until now. Advances in production technology and materials science, particularly for new types of high-tech steel, mean that Bessemer’s “twin-roll” idea is being taken up successfully. An alternative system that casts liquid steel directly onto a single horizontally moving belt is also being tried. Both techniques could cut energy…Continue reading