There are three main categories of cast irons. Gray, Ductile and Malleable Iron. Malleable Iron is rarely specified anymore because ductile iron offers better properties at comparable costs.
Cast iron is a family of metals that are iron-carbon-silicon alloys containing more than 2% carbon (C), usually 1 - 3% silicon (Si) and a few other elements for various purposes. The high C and Si content in cast irons helps formation of lower density free graphite in the iron during solidification and makes production of more complex castings possible. Ductile irons are represented by nodular graphite and gray irons contain flake graphite.
Gray irons are generally considered lower to moderate strength, with tensile ranges from 20,000 psi to 60,000 psi. Gray irons have better damping capacity and machinability. Ductile irons have moderate machinability and higher strength with tensile ranges from 60,000 psi to over 150,000 psi.
Cast irons are widely used in industries like agriculture, automotive, construction, and municipal applications.
Iron castings can be made with various processes, such as green sand process, resin sand process, shell mold, centrifugal process, permanent mold process, etc., depending on the specific features of the products and their intended applications, etc.