Why is chemical analysis not sufficient for cast iron alloys?
Cast iron alloys are very complex and several of the mechanisms behind crystallization and growth of austenite and graphite are only partially understood. While alloying elements may alter the physical properties of cast iron, the final properties and especially the behavior of the alloy when poured in a mold can not be fully predicted and controlled by chemical analysis alone. The practical foundryman experiences this daily in the form of unexpected casting defects, low yields and variations in physical properties. The amount and precipitation patterns of austenite and graphite influence the behavior of gray, ductile and compacted graphite iron during mold filling and solidification. The main variables involved are: • Alloy composition • Charge materials (size, rust, amount combined carbon etc) • Charging sequence • Type of melting furnace • Temperature and time sequences during melting and holding • Interactions with refractory linings • Possibilities for oxygen pick up • Mg-alloy co
