Iron Ore

Lore & Background

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 when compared to the ease of casting and handling. The Chinese were already making pig iron during 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 County of Mark to the 13th century, which is now part of Westphalia, Germany. It is unclear whether these northern European developments were derived from the Chinese ones or independent inventions. 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 step from bloomery to blast furnace is a big technical leap: not only a bigger furnace and more powerful blowers are needed but also higher quality refractory material and a crucible for the molten iron. The temperatures are considerably higher: more than 1,538 °C (2,800 °F), which is the melting temperature of iron.

In Their Own Story

Before her lay a vein of dark, metallic rock glowing faintly with the residual heat of the surrounding magma. She raised her pickaxe, the metal striking stone with a sharp *clang* that echoed in the silence. This was it—the first true haul of Iron Ore for the fledgling colony. As she chipped away at the crust, releasing a heavy chunk onto her inventory belt, she felt the familiar weight of progress. Tomorrow, this rough rock would become smooth ingots, and those ingots would become walls that kept the freezing void out.

Reader's Guide

Traditionally, pig iron was worked into wrought iron in finery forges, later puddling furnaces, and more recently, it is worked into steel. In these processes, pig iron is melted and a strong current of air is directed over it while it is stirred or agitated. This causes the dissolved impurities (such as silicon) to be thoroughly oxidized. An intermediate product of puddling is known as refined pig iron, finers metal, or refined iron. Pig iron can also be used to produce gray iron. This is achieved by remelting pig iron, often along with substantial quantities of steel and scrap iron, removing undesirable contaminants, adding alloys, and adjusting the carbon content. Ductile iron can also be produced using certain high purity grades of pig iron; depending on the grade of ductile iron being produced, the pig irons chosen may be low in the elements silicon, manganese, sulfur and phosphorus. High purity pig iron is used to dilute any elements in a ductile iron charge which may be harmful to the ductile iron process (except carbon).

Did You Know?

• Pig iron has a high carbon content, typically 3.8–4.7%, along with silica and other dross, which makes it brittle.
• The name 'pig iron' comes from the traditional mold shape: a branching structure with individual ingots at right angles to a central channel, resembling a litter of piglets nursed by a sow.
• The Chinese were already making pig iron during the later Zhou dynasty, which ended in 256 BC.
• Furnaces such as Lapphyttan in Sweden may date back to the 12th century.
• The melting temperature of iron is more than 1,538 °C (2,800 °F).