| 摘要 |
PROBLEM TO BE SOLVED: To provide a cold tool steel by refining, the steel having no problem that toughness and fatigue strength are low, and in which the stock cost of a die is not high and die heat treatment cost is not made high like a cold tool steel by powder metallurgy.SOLUTION: The cold tool steel for cold working produced by a dissolution method and having a hardness of 63 HRC or higher and high toughness is formed by subjecting a steel having a composition comprising, by mass, 0.6 to below 0.9% C, 0.6 to 1.0% Si, ≤0.6% Mn, 5.0 to 10.0% Cr, Mo+W/2:above 2.0 to 5.0%, 0.05 to 0.35% or below of V and <250 ppm N, also satisfying 3.0 to 5.5% K provided that K=-0.74C+0.24Cr+0.73(Mo+W/2)+2.12V(1), and the balance Fe with inevitable impurities to hardening treatment at a hardening temperature of 1,020 to below 1,050°C and also repeating a tempering step at a tempering temperature of 500 to 600°C for at least two times. |
