| 摘要 |
PROBLEM TO BE SOLVED: To provide tool steel excellent in antipodal characteristics of machinability and heat treatability. SOLUTION: This tool steel satisfies the relational formulae of, by mass, (Cr+5.9×C): 9.1 to 12.5, (Cr-4.2×C): <=5, and (Cr-6.3×C)>=2.2. Preferably, the tool steel has a composition, in addition to the above, containing 0.1 to 0.6% Si, 0.1 to 1.2% Mn, one or two kinds of Mo and W by (Mo+1/2W): 0.6 to 1.25% and <0.5% V, furthermore containing <=0.12% Si, <=100 ppm Ca, <=1% Ni and <=0.6% Al, and the balance Fe with inevitable impurities. In addition, in the tool steel, the matrix segregation width of Cr after quenching if <=1%, by mass, or, by tempering at >=500 deg.C, the maximum tempering hardness if >=57 HRC, or the heat treatment dimensional change generated by tempering at >=500 deg.C is <=0.1% expressed in terms of a linear expansion coefficient on a standard before the quenching, and also, the heat treatment dimensional change by tempering at 490 deg.C is <=0, and a die is produced by refining the tool steel to the hardness of >=55 HRC and executing machining.
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