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Abstract

This invention is aimed at providing a cold working die steel successfully reduced in the hardness, and increased in readiness in the cold workability (forging, pressing and so forth) and machinability (milling, drilling, endmilling processing, grinding and lathe turning). A cold working die steel aimed at solving the above-described subject consists essentially of, in % by mass, 0.6%.ltoreq.C.ltoreq.1.60%, 0.10%.ltoreq.Si.ltoreq.1.20%, 0.10%.ltoreq.Mn.ltoreq.0.60%, 5.5%.ltoreq.Cr.ltoreq.13.0%, 0.80%.ltoreq.Mo+0.5W.ltoreq.2.10%, 0.10%.ltoreq.V.ltoreq.0.40%, 0.0002%.ltoreq.O.ltoreq.0.0080%, 0.001%.ltoreq.A1.ltoreq.0.10%, and the balance of Fe and inevitable impurities; has transformation point Ar3 in the range from 750.degree. C. to 850.degree. C., with both ends inclusive; has a mean circle-equivalent diameter of a carbide, which belongs to a circle-equivalent diameter range from 0.1 .mu.m to 3 .mu.m observed in a section of a structure obtained after spherodizing a sample that was heated at a temperature of (Ar3+50.degree. C.) or above and 1,050.degree. C. or below, of 0.25 .mu.m to 0.8 .mu.m, with both ends inclusive; has a Brinell hardness attained after the spherodizing of HB179 to HB235, with both ends inclusive; has a steel cleanliness of (dB+dC)60.times.400 in the group C inclusion and the group B inclusion specified by JIS G0555 of 0.05% or less; and has a K value defined as Cr(%)-6.8.times.C(%) of 0.1 to 3.5, both ends inclusive.

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First Claim