| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel sheet for a machine structural component having excellent workability.SOLUTION: The steel sheet for a machine structural component has a chemical composition including, by mass, 0.15 to <0.35% C, ≤0.30% Si, 0.30 to 1.50% Mn, ≤0.02% S, 0.01 to 0.30% Cr, 0.002 to 0.030% Ti, ≤0.070% Al and ≤0.0070% N, and further including P and B in quantities satisfying the following inequalities (1) and (2), and the balance Fe with impurities, has a hardness of ≤95 by HRB, and is as quenched or is subjected to tempering at ≤400°C after quenching: 0.018×Si≤P≤0.2×(31/11)×(B)0.5(1) and 0.0005≤B≤0.0050(2); B* is prescribed by the following formula (3) and formula (4): B=max[B-(11/14)×N, 0](3) and N=max[N-(14/48)×Ti, 0](4). |
