It is the latest development in steel making processes and is now adopted at Rourkela steel plant where three converters of 40 tonnes capacity are working.
Note : The Bessemer process may be acidic or basic depending upon the lining of the furnace. In the acidic bessemer process, the furnace is lined with silica ricks. The slag produced in this process contains a large amount of silica. Since phosphorus in a pig iron cannot be removed by this process, therefore acidic bessemer process is unsuitable for producing steel from pig iron containing large quantities of phosphorus.
In basic Bessemer process, also known as the Thomas process, the furnace is lined with a mixture of tar and burned dolomite. This process is applicable for making steel from pig iron which contains more than 1.5% phosphorus.
Note: The steel contains small amounts of impurities like silicon, sulfur, manganese, and phosphorus. The effect of these impurities are as follows:
Silicon in the finished steel usually ranges from 0.05 to 0.30%. It is added in low carbon steels to prevent them from becoming porous. It removes the gases and oxides, prevents blow holes and thereby makes the steel tougher and harder.
Sulfur occurs in steel either as iron sulfide or manganese sulfide. Iron sulfide because of its low melting point produces red shortness whereas manganese sulfide does not affect so much.
Manganese serves as a valuable deoxidizing and purifying agent, in steel. When used in ordinary low carbon steels, manganese makes the metal ductile and of good bending qualities. In high-speed steels, it is used to toughen the metal and to increase its critical temperature.
Phosphorus makes the steel brittle, It also produces cold shortness in steel. In low carbon steels, it raises the yield point and improves the resistance to atmospheric corrosion. The sum of carbon and phosphorus usually does not exceed 0.25%.