Invented By - Ancient China
Year - 5th Century BC
Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%. Its usefulness derives from its low melt temperature. The alloy constituents affect its colour when fractured: white cast iron has carbide impurities which allow cracks to pass straight through; grey cast iron has graphite flakes which deflect a passing crack and initiate countless new cracks as the material breaks; ductile cast iron which stops the crack from further progressing due to their spherical graphite "nodules".
Cast iron tends to be brittle, except for malleable cast irons. With its relatively low melting point, good fluidity, castability, excellent machinability, resistance to deformation and wear resistance, cast irons have become an engineering material with a wide range of applications and are used in pipes, machines and automotive industry parts, such as cylinder heads (declining usage), cylinder blocks and gearbox cases (declining usage). It is resistant to destruction and weakening by oxidation (rust).
The earliest cast iron artefacts date to the 5th century BCE, and were discovered by archaeologists in what is now Jiangsu in China. Cast iron was used in ancient China for warfare, agriculture, and architecture. During the 15th century, cast iron became utilized for artillery in Burgundy, France, and in England during the Reformation. The first cast iron bridge was built during the 1770s by Abraham Darby III, and is known as The Iron Bridge. Cast iron is also used in the construction of buildings.
Cast iron is made by re-melting pig iron, often along with substantial quantities of iron, steel, limestone, carbon (coke) and taking various steps to remove undesirable contaminants. Phosphorus and sulfur may be burnt out of the molten iron, but this also burns out the carbon, which must be replaced. Depending on the application, carbon and silicon content are adjusted to the desired levels, which may be anywhere from 2–3.5% and 1–3%, respectively. Other elements are then added to the melt before the final form is produced by casting
