Material World: The Six Raw Materials That Shape Modern Civilization

by Ed Conway

The vast majority of that is turned into steel, which, despite its name, is simply one of many varieties of iron. The clue here is the carbon content. At one end of the spectrum is cast iron or pig iron (so named because when it was first made it would set in a series of channels and moulds resembling a litter of piglets being nursed by their mother). This is a brittle metal with about 3–4 per cent carbon. At the other end is wrought iron, soft enough to be beaten with a hammer and very pure, with infinitesimally small quantities of carbon. In the middle is steel, which typically has less than 2 per cent carbon (and usually, in the case of most mild steels, such as those which once came from the mills at Azovstal, a fair bit less; well below 1 per cent).