DIE STEEL AND METHOD FOR PRODUCING SAME

Provided are a mold steel which satisfies the basic characteristics of mold steel and also exhibits both an excellent rust resistance and a high thermal conductivity, and a method for producing the same. A mold steel that is a steel having a composition containing, in terms of mass%: 0.07 to 0.15% of C; more than 0 and less than 0.8% of Si; more than 0 and not more than 1.0% of Mn; less than 0.05% of P; less than 0.02% of S; more than 0 and not more than 0.5% of Ni; more than 0 and less than 0.8% of Mo and W, either alone or as a complex (Mo + 1/2W); more than 0 and less than 0.15% of V; and 0.25 to 1.5% of Cu, with the balance consisting of Fe, Cr and unavoidable impurities, wherein the content of Cr is more than 4.9% and not more than 5.3% and the hardness of the mold steel is 30 to 42 HRC. It is preferred that, in the unavoidable impurities, the contents of Al, N and O are regulated respectively to less than 0.1%, less than 0.06% and less than 0.0055%. The aforesaid hardness can be obtained by quenching the mold steel and then tempering the same at 530 DEG C or higher.