Gray cast irons are so named because of the many flakes of graphite they contain, which convey a dull gray color to the material. Phosphorous is used to lower the freezing point and slow the solidification process of gray cast irons in order that they may be formed into intricate designs. Graphite formation, however, is increased during extended periods of solidification and the correspondingly high graphite content of gray cast irons reduces the metal’s strength and flexibility.