| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel sheet to be die-quenched superior in hot-punchability. 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. Mn-containing sulfides in the steel sheet have minor axes of which the average is 0.10 μm or more. Thereby produced steel sheet can reduce the occurrence of a burr when hot-punched and has such a high strength as a tensile strength of 2,000 MPa or more after having been die-quenched. A molded product with a hole can be inexpensively and easily manufactured from the steel sheet. In addition, the steel sheet has Mn-containing sulfides with minor axes of 0.1 μm or more preferably in an amount of 30 pieces or more by average per 1 mm<SP>2</SP>in a cross section of the steel sheet. The steel sheet also may further include one or more elements selected from among 0.15-1% Cr, 0.0008-0.0030% B, 0.1-0.5% Mo and 0.05-1% W, in addition to the above composition. COPYRIGHT: (C)2010,JPO&INPIT
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