| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a steel sheet to be die-quenched superior in hot-punchability. Ž<P>SOLUTION: The steel sheet has a composition which includes, by mass%, 0.35-0.45% C, 0.15-0.5% Si, 1.0-1.8% Mn, 0.03% or less P, 0.020-0.050% S, 0.015-0.07% Al, 0.005% or less N, and Ti in the range of 0.05 to 0.15% so that Ti* which is defined by Ti*=Ti-3.4N-1.5S satisfies C-0.25Ti*≥0.35. Ti-containing sulfides in the steel sheet have diameters of which the average is 0.10 μm or more. In addition, the steel sheet has Ti-containing sulfides with diameters of 0.10 μm or more preferably in an amount of 30 pieces/mm<SP>2</SP>or more by average in a cross section of the steel sheet. The steel sheet also may further include one or more elements selected from among Cr, B, Mo and W, in addition to the above composition. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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