Cast iron was discovered in China during the Warring States period (475-221 BC). In Europe, it became essential in the economy during the 19th century. The gestures applied today by the workers at GHM are hardly different from those of the 19th century, and the buildings of bricks are still testament to this period. In metallurgy, cast iron describes an iron alloy containing 2.1 to 6.67% of carbon. The steelmakers at GHM, in the Haute-Marne department, also often work with cast aluminum and bronze alloys.