| 摘要 |
A steel for cold forging which has not undergone annealing and which comprises 0.1-1.0 wt.% carbon, 0.1-2.0 wt.% silicon, 0.01-1.50 wt.% manganese, up to 0.100 wt.% phosphorus, up to 0.500 wt.% sulfur, up to 0. 005 wt.% dissolved nitrogen, and iron and unavoidable impurities as the remainder, has a structure having a pearlite content of 120x[carbon amount (%)] % or lower, has an outermost-layer hardness of 450x[carbon amount (%)]+90 or higher in terms of HV, and shows excellent softening properties in annealing; a process for producing the steel; and a steel for cold forging which has undergone annealing and which comprises the same ingredients as the above and has a structure in which more than 20 % of the carbon is present as graphite and the graphite has an average grain diameter of 10x[carbon amount (%)] 1/3 mum or smaller and a maximum grain diameter of 20 mum or smaller.
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