| 摘要 |
PROBLEM TO BE SOLVED: To provide hot tool steel capable of simultaneously attaining the improvement of the lives of a die and a tool and the reduction of the production cost by improving its resistance to heat cracks and wear and its machinability. SOLUTION: This powder hot tool steel has a composition containing, by mass, >0.35 to <0.45% C, <1.0% Si, 0.2 to 1.5% Mn, 0.05 to 0.30% S, 2.35 to 5.65% Cr and one or two kinds of W and Mo by (1.2W+Mo): 1.5 to 3.5%, 0.5 to 1.5% V, in which the contents of Si and Cr satisfy the relational inequality of Si<; (18.7/Cr) -3.3, and the balance Fe with inevitable impurities. Alternatively, the powder hot tool steel contains <=1.5% Ni or <=5.0% Co as well. Then, the powder hot tool steel has hardness of >50 HRC, and the hot die is composed of the same powder hot tool steel.
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