Basic oxygen converter, also called LD-steelmaking, is a method able to turn pig iron into steel. A water-cooled lance blows oxygen through molten metal, burning excess carbon. The process is called basic because alkaline limestone is added to help remove impurities.
This process is used to make 60% of world steel and can convert 400 tons of pig iron in less than 40 minutes. Its principle has been invented by Henry Bessemer at the middle of 19th century. Work by Swiss engineer Robert Durrer and Austrian companies VOEST and ÖAMG led to its industrialization.