| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a die for hot working which has both of wear resistance and heat-cracking resistance, and can be used as a die for machined parts having comparatively large size such as a crank shaft. Ž<P>SOLUTION: A base metal of the die for hot working has chemical composition including 0.30 to <0.50% C, 0.10-0.5% Si, 0.30-1.0% Mn, ≤0.02% P, ≤0.005% S, 4.0-8.0% Cr, 0.2 to <1.5% Mo, 0.05-1.0% V, ≤0.03% Al, ≤0.0150% N, ≤0.0030% O and the balance Fe with impurities, wherein <0.7% Ni and <0.7% W as the impurities are contained, and the base metal has a tensile strength of ≥900 MPa. In the die for hot working, a nitrided layer having hardened depth exceeding 200 μm is provided at least on the surface contacted with a material to be worked, and the hardness at a position at ≥30 μm depth of the nitrided layer is ≤900 Vickers hardness. The base metal may further contain one or more kinds of Nb, Ti, B, Ca. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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