Pig iron

Pig iron, also known as crude iron, is an intermediate good used by the iron industry in the production of steel, which is developed by smelting iron ore in a blast furnace. Pig iron has a high carbon content, typically 3.8–4.7%, along with silica and other constituents of dross, which makes it brittle and not useful directly as a material except for limited applications. The traditional shape of the molds used for pig iron ingots is a branching structure formed in sand, with many individual ingots at right angles to a central channel or "runner", resembling a litter of piglets being nursed by a sow. When the metal had cooled and hardened, the smaller ingots (the "pigs") were simply broken from the runner (the "sow"), hence the name "pig iron". As pig iron is intended for remelting, the uneven size of the ingots and the inclusion of small amounts of sand are insignificant issues when compared to the ease of casting and handling. History of ferrous metallurgy Smelting and producing wrought iron was known in ancient Europe and the Middle East, but it was produced in bloomeries by direct reduction. Pig iron was not produced in Europe before the Middle Ages. The Chinese were making pig iron by the later Zhou dynasty (which ended in 256 BC). Furnaces such as Lapphyttan in Sweden may date back to the 12th century; and some in Mark (today part of Westphalia, Germany) to the 13th. It remains to be established whether these northern European developments derive from Chinese ones. Wagner has postulated a possible link via Persian contacts with China along the Silk Road and Viking contacts with Persia, but there is a chronological gap between the Viking period and Lapphyttan. The phase transition of the iron into liquid in the furnace was an avoided phenomenon, as decarburizing the pig iron into steel was an extremely tedious process using medieval technology. Traditionally, pig iron was worked into wrought iron in finery forges, later puddling furnaces, and more recently, into steel.