| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel for a machine structure which can be subjected to working such as cold working without performing heat treatment such as softening and annealing in hot rolling. SOLUTION: The steel has a composition satisfying, by mass, 0.25 to 0.5% C, <=0.5% (not inclusive of 0%) Si, 0.2 to 2% Mn, <=0.03% (inclusive of 0%) P, <=0.03% (inclusive of 0%) S, 0.01 to 0.06% Al, <=0.01% (inclusive of 0%) N. The steel further contains at least one element selected from the group consisting of 0.002 to 0.01% Nb, 0.002 to 0.01% Ti, 0.002 to 0.01% V and 0.002 to 0.01% Zr, and those elements satisfy the following inequality (1): (Nb/92.9+Ti/47.9+V/50.9+Zr/91.2)/(N/14)>1.0 (1).
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