HIGH-HARDNESS PRE-HARDENED COLD-ROLLED TOOL STEEL FOR SURFACE PVD, METHOD FOR PRODUCING SAME, AND SURFACE PVD METHOD FOR SAME

摘要

Provided are: a high-hardness pre-hardened cold-rolled tool steel for surface PVD, wherein problems of softening and deformation due to thermal processing during when subjected to surface PVD are improved; a method for producing the high-hardness pre-hardened cold-rolled tool steel for surface PVD; and a surface PVD method for the pre-hardened cold-rolled tool steel. The pre-hardened cold-rolled tool steel is composed of 0.7-1.2% by mass of C, 1.0-2.6% by mass of Si, 0.4-1.0% by mass of Mn, 0.02-0.1% by mass of S, 3.0-6.0% by mass of Cr, 0.4-1.0% by mass of Mo or W by itself or Mo and W in combination (Mo + 1/2W), 0.2-1.0% by mass of V and 0.1-0.3% by mass of Nb, with the balance made up of Fe and unavoidable impurities. The pre-hardened cold-rolled tool steel has a temper hardness of 60 HRC or more and a residual austenite amount in the structure of 8% by volume or less. The pre-hardened cold-rolled tool steel may contain 1.0% by mass or less of Ni. Preferable refining conditions are quenching at 1000°C or higher and tempering at 520°C or higher. It is preferable that the change in the residual austenite amount before and after the surface PVD is set to 5% by volume or less.