Blast Furnace and Pig Iron
Pig iron is the term applied generally to the metallic product of the blast furnace when it contains over 90 percent iron. Most pig iron is transferred to the steel-making shops and used in the liquid state; in this form it is referred to as hot metal. The term "pig iron" arose from the old-fashioned method of casting iron into beds of molds form in sand, so arranged that they could be fed from a common runner. Since the group of molds resembled a litter of suckling pigs, the individual pieces of iron were referred to as "pigs" and the runner as a "sow".In the blast-furnace process, iron-bearing materials, such as iron ore, sinter, pellets, along with fuel (coke), and flux (limestone) are charged into the top of the furnace (Fig. 6). Heated air (blast) and, in some instances, fuel (gas, oil or powdered coal) are blown in at the bottom. The blast air burns part of the fuel to produce heat for the chemical reactions involved and for melting the iron, while the balance of the fuel and part of the gas from the combustion remove the oxygen combined with the metal.