The experiments were carried out on the formation of nodular graphite in cast iron by adding some different kinds of mother alloys to molten cast iron and on the increase of graphite particles caused by annealing treatment. The yield of modified element in cast iron is increased as the content of alloying element in mother alloy or the amount of mother alloy added to molten cast iron decreases. By using many components alloy the structure in which the ground mass consisted fully of ferrite, is obtained. The hardness of modified cast iron decreases rapidly by annealing or with the increase of the diameter of specimen
