Nodular cast iron is a kind of high strength cast iron material developed in 1950s. Its comprehensive properties are close to that of steel. Based on its excellent properties, it has been successfully used to cast some parts with complex stress and high requirements for strength, toughness and wear resistance. Nodular cast iron has developed rapidly to be a widely used cast iron material next to gray cast iron. The so-called "replacing steel with iron" mainly refers to ductile iron. Spheroidal graphite is obtained by spheroidizing and inoculation, which can effectively improve the mechanical properties of cast iron, especially the plasticity and toughness, so as to obtain higher strength than carbon steel.