Steel industry process
Iron is most widely found in the crust of the earth, in the form of various minerals (oxides, hydrated ores, carbonates, sulphides, silicates and so on). Since prehistoric times, humans have learned to prepare and process these minerals by various washing, crushing and screening operations, by separating the gangue, calcining, sintering and pelletizing, in order to render the ores smelt able and to obtain iron and steel.
Iron occurs mainly as oxide ores, though it is also found in smaller quantities as its sulfide and carbonate. These other ores are usually first roasted to convert them into the oxide.
The carbon initially burns in air to give carbon dioxide and the heat, which is necessary for the process. The carbon dioxide then undergoes an endothermic reaction with more carbon to yield carbon monoxide:
C + O2 → CO2
C + CO2 → 2CO
The oxide ores are then principally reduced by the carbon monoxide produced in this reaction, the reactions involving very small enthalpy changes:
Fe2O3 + 3CO → 2Fe + 3CO2
Fe3O4 + 4CO → 3Fe + 4CO2
Steel is a term given to alloys containing a high proportion of iron with some carbon. The major disadvantage of steel is that it will oxidize under moist conditions to form rust. Typical steel would have a density of about 7.7 g cm-3 and a melting point of about 1650 degree.