Malleable Iron

Malleable iron is cast iron that has been transformed from a hard, brittle material into a tough, ductile one by a controlled annealing process: the iron is first cast as white iron, in which nearly all its carbon is locked up as hard iron carbide, and is then reheated and held at high temperature for an extended period so that the carbide breaks down and its carbon reorganizes into small, roughly spherical nodules of graphite scattered through a softer iron matrix, leaving a metal that can be bent, machined and shocked without shattering. Archaeologists have identified malleable iron artifacts made in China as early as the fourth century BC, showing the annealing technique was understood there many centuries before it appeared in the West. In Europe, the French scientist Rene Antoine Ferchault de Reaumur carried out extensive research on malleable iron starting in 1720, discovering that iron castings could be softened by packing them in iron ore and holding them at high temperature for an extended period, and the process reached American industry in 1826 when Seth Boyden opened a foundry in Newark, New Jersey to manufacture malleable iron harness hardware and small castings.