Bessemer Process:

This is an industrial procedure for the manufacture of steel through molten pig iron. The principle included is that of oxidation of the impurities in the iron through the oxygen of air that is blown from the molten iron; the heat of oxidation increases the temperature of the mass and keeps it molten throughout operation. The procedure is carried on in a big container called the Bessemer converter as illustrated in Figure 6 that is made of steel and contain a lining of silica and clay or of dolomite. The ability is from 8 to 30 tons of molten iron; the normal charge is 15 or 18 tons. The converter is of egg-shaped. At its narrow upper ending it contains an opening through that the iron to be treated is introduced and the finished manufactured is poured out. The wide end, or bottom, contain a number of perforations (tuyeres) through which the air is forced upward into the converter throughout operation. The container is set on pivots (trunnions) so that it might be tilted at an angle to attain the charge, turned upright throughout the blow, and inclined for pouring the molten steel after the operation is accomplished. As the air passes upward from the molten pig iron, impurities such like manganese, silicon and carbon unite along the oxygen in the air to form oxides; the carbon monoxide burns off along a blue flame and the other impurities form slag.

Dolomite is utilized as the converter lining while the phosphorus content is high; the procedure is then known as basic Bessemer. The silica and clay lining is utilized in the acid Bessemer, in which phosphorus is not eliminated. To provide the elements essential to give the steel the desired properties, usually another substance (an iron-carbon-manganese alloy) is added up to the molten metal after the oxidation is accomplished. Then the converter is emptied into ladles from which the steel is poured into molds; the slag is left behind. The entire process is accomplished in 15 to 20 min.

Figure: The Bessemer Process