Nodular cast iron with high strength and high tenacity, crank shaft and manufacturing method thereof

The invention provides a nodular cast iron with high strength and high tenacity. The nodular cast iron material used for a crank shaft is subjected to component intensifying; the invention further provides a manufacturing method of the nodular cast iron crank shaft with high strength and high tenacity; the nodular cast iron crank shaft is subjected to technique intensifying, so that the nodularization level of the crank shaft is 1-2 level; the size of graphene is 5-8 level; the crank shaft is subjected to isothermal quenching to obtain an upper bainite structure of 2-3 level; the component intensifying and the technique intensifying are favorably combined, so that the tensile strength of the crank shaft is larger than or equal to 900MPa; the ductility is larger than or equal to 10%; the impact tenacity is larger than or equal to 190 J/cm ; the hardness is 260-320 HBW; the comprehensive mechanical performance is better than that of forged steel 40Cr and 42CrMo; iron replacing steel isrealized in a true sense;