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Grey cast iron also known as flake graphite cast iron, is a type of casting iron in which most of the carbon is present as flake graphite .The propertises of grey cast iron depends on the distribution, sizs and amount of graphite flakes, and the matrix structure. These factorys are in turn, influenced mainly by the manufacturing conditions, chemical composition, solidification time and rate of cooling in he mould. Grey cast iron exhibit low to moderate strength, low modulus of elasticity, low notch sensitiviy, high thermal conductivity, moderate resistance of thermal stock , and outstanding castability
Cast iron is made by remelting pig iron, often along with substantial quantities of scrap iron and scrap steel, and taking various steps to remove undesirable contaminants such as phosphorus and sulfur. Depending on the application, carbon and silicon content are reduced to the desired levels, which may be anywhere from 2% to 3.5% and 1% to 3% respectively. Other elements are then added to the melt before the final form is produced by casting.
Iron is most commonly melted in a small blast furnace known as a cupola (see blast furnace for more details). After melting is complete, the molten iron is removed or ladled from the forehearth of the blast furnace. This process was devised by the Chinese, whose innovative ideas revolutionized the field of metallurgy. Previously, iron was melted in an air furnace, which is a type of reverberatory furnace.