Only die casting molding will generally satisfy the mechanical demands of mold inserts that are required for more than just experimental and low-production runs. Furthermore, only steel has an adequate degree of polish ability. Many of the steel grades successfully employed in mold making are amenable to casting. However, it must be borne in mind that castings always have a coarse structure that is not comparable to the transformation structure of foiled or rolled steels. At the macroscopic level，castings have different primal grain sizes between the edge and core zones. There is limited scope for using subsequent heat treatment to eliminate the primary phases that settle out on the grain surfaces during solidification. For these reasons, when making cast molds, it is best to use steel grades that have little tendency to form coarse crystals or to separate by liquation.
Not only does die casting molding treatment bring about the improvement in structure mentioned above but it also enhances the mechanical properties, and the necessary notch resistance and stress relief are obtained. The strength, which depends on the carbon content, is lower than that of rolled or forged steel, and so too are the toughness and ductility . However, they meet the major demands imposed on them. The service life of cast steel molds depends on the wear resistance and, under thermal load, on the thermal shock resistance. Given comparable steel grades, the thermal shock resistance of cast steels is generally lower than that of worked steels.