Ĭast iron is sometimes melted in a special type of blast furnace known as a cupola, but in modern applications, it is more often melted in electric induction furnaces or electric arc furnaces. If desired, other elements are then added to the melt before the final form is produced by casting. 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. Phosphorus and sulfur may be burnt out of the molten iron, but this also burns out the carbon, which must be replaced. Cast iron can be made directly from the molten pig iron or by re-melting pig iron, often along with substantial quantities of iron, steel, limestone, carbon (coke) and taking various steps to remove undesirable contaminants. Cast iron was also used in the construction of buildings.Ĭast iron is made from pig iron, which is the product of melting iron ore in a blast furnace. The first cast-iron bridge was built during the 1770s by Abraham Darby III, and is known as the Iron Bridge in Shropshire, England. The amounts of cast iron used for cannons required large-scale production. During the 15th century AD, cast iron became utilized for cannon in Burgundy, France, and in England during the Reformation. Cast iron was used in ancient China for warfare, agriculture, and architecture. The earliest cast-iron artefacts date to the 5th century BC, and were discovered by archaeologists in what is now Jiangsu, China. It is resistant to damage by oxidation but is notoriously difficult to weld. 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, cylinder blocks and gearbox cases. Iron alloys with lower carbon content are known as steel.Ĭast iron tends to be brittle, except for malleable cast irons.
#Colorcast cast iron crack#
The alloy constituents affect its color 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, and ductile cast iron has spherical graphite "nodules" which stop the crack from further progressing.Ĭarbon (C), ranging from 1.8 to 4 wt%, and silicon (Si), 1–3 wt%, are the main alloying elements of cast iron. Its usefulness derives from its relatively low melting temperature. Cast iron is a class of iron– carbon alloys with a carbon content more than 2%.
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