To provide steel with uniformly diffused graphite which is excellent in cutting property, cold-forging property, and toughness after hardening and tempering by providing the steel having the composition consisting of C, B, N, Mg, etc., of the prescribed wt.% and the balance Fe, specifying the range of the grain size and number of inclusion, and specifying the mean grain size of graphite.
The steel with uniformly diffused graphite has the composition consisting of, by weight, 0.1-1.0% C, 0.01-2.0% Si, 0.1-1% Mn, ≤0.2% P, 0.001-0.1% S, 0.0001-0.01% B, 0.0002-0.02% N, 0.0001-0.01% Mg, and the balance Fe with inevitable impurities. The inclusion contains oxide or sulfide containing Mg whose grain size is 0.005-10.0 μm, or both is contained by the number of 103-106/mm2, and graphite whose mean grain size is η5.0 μm is contained after graphitization and annealing. In addition, one or more kinds of group of Cr, Ni, Co and Cu of the prescribed quantity is contained. The graphite steel excellent in the cutting surface roughness and high frequency hardening property can be provided.
TARUI TOSHIZO
HASHIMURA MASAYUKI
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