Which grades of cast iron are the most popular in foundry production?

Cast irons are alloys of Fe and C containing > 2.14% carbon. A key feature of cast irons is the presence of a eutectic in their structure. A eutectic is a mixture of two phases; in cast irons, this is austenite and cementite. Due to the combination of excellent casting properties with good strength and wear resistance, cast irons are used to make parts where strict dimensional accuracy is not required. The carbon in cast irons is present in the form of graphite. Graphite inclusions improve machinability by reducing hardness. Moreover, cast irons exhibit the best casting properties among all iron-based alloys. There are four main types of cast iron: gray, ductile (high-strength), malleable, and white. In gray cast irons (GCI), graphite is present as flakes. White cast irons have flake-like graphite inclusions, while ductile cast irons (SGI) have spherical graphite. The type of cast iron can be determined by examining microsections of castings under a microscope.