The Bessemer process is the industrial process of manufacturing steel cheaply and in mass quantities by converting and refining pig iron into steel from a blast furnace. The technique was named after the British engineer Henry Bessemer who invented a special converter for producing steel called the Bessemer converter in 1856.
The primary objective of the Bessemer process was to remove the impurities of pig iron via oxidation and blasting compressed air through the molten iron to burn out any impurities. During the Bessemer process, oxidation was used to raise the temperature of the iron to keep it in a molten state.
The process involved using a Bessemar converter—an egg-shaped steel container lined with clay and dolomite. The converter had the capacity to hold from eight to 30 tons of molten iron. The top of the converter featured an opening through which the iron was placed and the finished product removed. The bottom of the converter featured a number of perforated channels through which air was forced up into the the converter. The converter was also pivoted on trunnions so it could be rotated to receive an electrical charge, turned upright during conversion, and then rotated over again for pouring out the molten steel into molds with the slag from the process being left behind. This conversion process, called the blow, could be finished in around 20 minutes.
About 20 years after the Bessemer method was first invented, it was being used worldwide in the manufacturing of steel. It was first patented by William Kelly in the U.S. in 1857. Eventually, 90 percent of American manufacturers produced steel using this method.