| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing steel for a plastic molding die excellent in toughness, mirror finishing properties and crimping properties and moreover excellent in a machinability. SOLUTION: In this method for producing steel for a plastic molding die, steel containing, by weight, 0.01 to 0.20% C, <=1.0% Si, 0.5 to 2.5% Mn, 1.5 to 3.5% Ni, 0.3 to 2.5% Cu, 0.3 to 1.5% Al, <=15 ppm O, <=150 ppm N, and the balance Fe is hot-worked, is cooled to <=1173 K at a cooling rate of 0.5 to 10 K/s to a lower bainitic region, is held at >=1.8 Ks and is thereafter subjected to again treatment at 723 to 873 K. Moreover, the steel may contain 0.01 to 0.30% S, <=0.3% Pb, <=0.3% Bi, <=0.3% Se, <=0.3% Te, <=0.005% Zr, <=0.01% B, <=0.02% Ca, 0.05 to 0.04% Cr, 0.1 to 1.0% Mo, <=0.5% W, 0.6% V, 0.6% Ti and <=0.6% Nb as well.
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