Pigiron

Pig iron is an intermediate product of the iron industry. Crude iron as first obtained from a smelting furnace, in the form of oblong blocks. Pig iron has a very high carbon content, typically 3.8–4.7%, along with silica and other constituents of dross, which makes it very brittle, and not useful directly as a material except for limited applications. Pig iron is made by smelting iron ore into a transportable ingot of impure high carbon-content iron in a blast furnace as an ingredient for further processing steps. The traditional shape of the molds used for pig iron ingots was 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 suckled 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 caused only insignificant problems considering the ease of casting and handling them.

Smelting and producing wrought iron was known in ancient Europe and the Middle East, but iron was produced in bloomeries by direct reduction. Pig iron was not produced in Europe before the Middle Ages. The Chinese were also 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 the Mark, Westfalen, 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.

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