Preamble

Converter steelmaking processes are also known as BOF (Basic oxygen Furnace) steelmaking. These processes include top blown steelmaking and combined blown steelmaking processes. These processes are based on hot metal. Hot metal from Blast furnace is refined to steel. Blast furnace hot metal contains 3-4 % C, 0.8 to 1% Si, 0.6 to 0.8 %   and 0.15 - 0.2 % P. In all BOF processes, oxygen is blown from top. In most of the steelmaking practices hot metal is pretreated to remove Si, P and S from hot metal to the extent it is possible. This lecture discusses pretreatment of hot metal and material balance.

Pretreatment of hot metal

In recent years pretreatment of hot metal prior to charging in converter has become common practice. The objective is to reduce S, P and Si of hot metal to produce steel with good surface finish, free from internal cracks. P and Si removal reactions are dealt in lectures 6, 7 and 8. Here S removal is discussed

Removal of Sulphur

Removal of sulphur is called desulphurization.  Sulphur exhibits negative deviation from Henry’s Law in molten iron. Bonds between Fe and S are strong. Activity coefficient of S increases with increase in C, Si and P.