Basic oxygen furnace
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The basic oxygen furnace is the place within a foundry where molten iron from the blast furnace is changed into liquid steel. The vast majority of steel manufactured in the world is produced using the basic oxygen furnace. It is the most common way for steel to be made in the United Kingdom. Modern furnaces will take a charge of iron of up to 350 tons and convert it into steel in less than 40 minutes.
Oxygen is blown into the furnace or BOS vessel through a water cooled oxygen lance, like the LD converter. This oxidises carbon and the other unwanted elements in the hot metal. Carbon is oxidised to carbon monoxide gas, which passes from the converter to a cleaning plant. After cleaning, it can be re-used as a fuel gas. The rest of the elements in the metal are converted to acidic oxides. They combine with the lime and other fluxes that are added during the blow.
This produces a slag that floats on the surface of the metal.
The steel is tapped from the furnace when it is at the correct temperature and composition. The furnace is tilted and the molten metal is run out via the taphole into a ladle. Once the steel has been removed, the furnace is turned upside down and the slag that is left inside runs into another ladle. The solidified slag can be used in the production of cement and as an aggregate in road building.