Abstract: The injection punch is a ductile iron component cast in sand mold, which is prone to defcts such as shrinkage, porosity, and porosity inside. After machining, the surface will exhibit a loose structure. In the early stage of trial production of the product, the average service life of our branch company’s product was only half as hift（12hours per shift）. After improving the moliding and melting process, the internal structure of the product is dense, and the rate of pualified products after machining is over 98%. At the same time, the induction hardening process on the outer surface of the product was improved, resulting in the transformation of the matrix metallographic structure into flake-like martensite, and the surface hardness was further improved, with a single piece service life of more than one shift.