STEEL FOR PLASTIC MOLDING DIE EXCELLENT IN MACHINABILITY AND SPECULARITY

摘要

PROBLEM TO BE SOLVED: To provide a steel for a plastic molding die excellent in machinability and specularity by preventing a size of a sulfide-based inclusion from excessively increasing.;SOLUTION: There is provided a steel for a plastic molding die excellent in machinability and specularity, containing, by mass%, C:0.12 to 0.30%, Si:0.25 to 0.45%, Mn:0.5 to 2.0%, S:0.012 to 0.060%, Cr:1.0 to 3.0%, Mo:0.10 to 0.40%, Al:0.001 to 0.050%, O:less than 0.10% and the balance Fe with inevitable impurities, and having hardness of a matrix of 26 to 38 HRC, volume fraction of an inclusion of 0.03 to 0.30%, difference between hardness of the inclusion having volume fraction of 75% or more and hardness of matrix of 250 HV or less, and √Area of a size of the inclusion occupied at 95% or more as a number percentage of 50 μm or less.;COPYRIGHT: (C)2014,JPO&INPIT