Heat treatment process of nodular cast iron piston casting

The invention discloses a heat treatment process of a nodular cast iron piston casting, and relates to the technical field of nodular cast iron heat treatment, the heat treatment process of the nodular cast iron piston casting comprises the following steps: step 1, casting pretreatment, step 2, quenching treatment, step 3, tempering treatment, and step 4, cleaning and drying. According to the method, an original matrix is completely austenitized through high-temperature quenching and heat preservation treatment, the original matrix is converted into tempered martensite and retained austenite structures in the process of cooling the nodular cast iron piston casting through the cooling effect of quenching oil, and the casting subjected to quenching treatment has high hardness and certain toughness; the lubricating property of graphite is reserved, the wear resistance is enhanced, the ethylene-propylene-diene copolymer is added as a cooling accelerant, the cooling process of oil quenching can be effectively acce