Grey cast iron (also called grey cast iron) is a group of cast iron including several kinds of grade according to different designation of diverse standards. Gray cast iron is a kind of iron-carbon alloy and it gets its name "grey" from the fact that their cutting sections looks grey. The metallographic structure of gray cast iron is mainly composed of flake graphite, metal matrix and grain boundary eutectic. During the grey iron, the Carbon is in the flake graphite. As one of the widely used casting metals, cast gray iron has many advangates in costs, castability and machinablity.