|
|
Ductile Iron Casting was the original "cast iron", and is an iron alloy characterized by its relatively high carbon content (usually 2% to 4%). When molten cast iron solidifies some of the carbon precipitates as graphite, forming tiny, irregular flakes within the crystal structure of the metal. While the graphite enhances the desirable properties of cast iron (improved casting & machining properties and better thermal conductivity), the flakes disrupt the crystal structure and provide a nucleation point for cracks, leading to cast iron¡¯s characteristic brittleness. In ductile iron the graphite is in the form of spherical nodules rather than flakes, thus inhibiting the creation of cracks and providing the enhanced ductility that gives the alloy its name. The formation of nodules is achieved by addition of "nodulizers" (for example, magnesium or cerium) into the melt. Yttrium has also been studied as a possible nodulizer.