Bessemer Converter

A Bessemer converter is the large pear-shaped vessel used in the Bessemer process, the first inexpensive industrial method for mass producing steel from molten pig iron, in which a blast of air is forced up through the molten metal inside the vessel to burn off excess carbon and other impurities in ten to twenty minutes, compared with a full day by earlier methods. The English engineer Henry Bessemer developed the process after a conversation with Napoleon III in 1854 about improving steel for artillery during the Crimean War, began work on it in January 1855, and patented it in 1856, though the American William Kelly claimed an independent and earlier discovery around 1851 that most historians consider less developed. The Bessemer converter made steel affordable at a scale that transformed railroad and bridge building, though it was later displaced by the open hearth furnace and, still later, the electric arc furnace.