Öntöttvasak

Öntöttvasak, known in English as cast irons, are a family of iron-carbon alloys with a carbon content greater than 2%. These alloys typically contain between 2% and 4% carbon, along with significant amounts of silicon (often 1-3%), and smaller amounts of manganese, phosphorus, and sulfur. The presence of carbon and silicon significantly lowers the melting point of iron compared to pure iron or steel, making it highly suitable for casting.

The properties of cast iron are largely determined by the form in which the carbon exists within the microstructure. The primary types include gray cast iron, ductile iron (or nodular cast iron), white cast iron, and malleable cast iron. Gray cast iron, the most common type, features graphite in the form of flakes, which give it excellent machinability, vibration damping, and wear resistance, but make it brittle. Ductile iron has graphite in spherical nodules, providing higher tensile strength and ductility, making it suitable for applications requiring toughness. White cast iron has carbon in the form of iron carbide (cementite), which is extremely hard and brittle, making it ideal for wear-resistant components. Malleable cast iron is produced by heat-treating white cast iron to convert the cementite into graphite nodules, resulting in improved ductility.

Cast irons are widely used in various industries due to their cost-effectiveness, good castability, and specific mechanical properties. Common applications include engine blocks, crankshafts, brake discs, pipes, cookware, and machine tool bases. The selection of a particular type of cast iron depends heavily on the intended service conditions and required performance characteristics.