BAB IPENDAHULUAN1.1. STEEL MAKINGPig iron is not a useful material for practical use because of its high impurities & gas content. By remelting & minor adjustment; it can be rendered useful as cast iron for founding. The major disadvantage of cast iron is that it is not a malleable & ductile alloy. The malleable & ductile form of iron can only be produced by removing of the impurities present in pig iron dan converting it into steel. Steel making process is reverse of iron making in the sense that here selective oxidation of impurities take place. The oxides are eliminated either as gas or as liquid slag. Classification of steel making processes:1. Bessemer process2. Open hearth process3. Electric furnace process4. LD process5. Kaldo process6. Rotor processBessemer process, open hearth process and electric furnace processes are often called conventional methods of steel making. LD process, Kaldo process, Rotor process and their modifications are called oxygen steel making processes. They are also called basic oxygen furnace processes because of their basic nature. Steel making is a refining or an oxidation process with the exception of reducing conditions being specifically required to eliminate sulphur, phosphor, and other impurity. Being an oxidation process steelmaking needs a source of oxidizing agent. The obvious choice being the oxygen in the form of atmospheric air and / or iron oxide in the form of iron ore and mill scale (oxide produced during hot working of steels). The conventional methods of steelmaking use either or both of these reagents.

The chemistry of steelmaking refining process can be simply described as[Fe} + [O] = (FeO)[C] + [O] = {CO}[Si] + 2[O] = (SiO2)[Mn] + [O] = (MnO)2[P] + 5[O] = (P2O5)[S] + (CaO) = (CaS) + [O]

Except the sulphur reaction, all the rest are oxidizing processes and are favored under the oxidizing conditions of steel making. In the case of oxidation of carbon the product, being a gas, will pass off into the atmosphere but the rest of the oxide products shall remain in contact with the iron melt in the form of a slag phase. As far as the physical requirement of the oxide product is concerned it should be readily separable from the iron melt. This is achieved by keeping the slag and the metal both as thin liquids so that the metal being heavier settles down and the slag floats on top in the form of two immiscible liquids which can be separated readily.