HIGH-STRENGTH HOT-ROLLED STEEL SHEET HAVING MAXIMUM TENSILE STRENGTH OF 980 MPa OR ABOVE, AND HAVIN

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This high-strength steel sheet contains, in mass%, 0.01% to 0.2% carbon, 0 to 2.5% silicon, 0 to 4.0% manganese, 0 to 2.0% aluminum, 0 to 0.01% nitrogen, 0 to 2.0% copper, 0 to 2.0% nickel, 0 to 1.0% molybdenum, 0 to 0.3% vanadium, 0 to 2.0% chromium, 0 to 0.01% magnesium, 0 to 0.01% calcium, 0 to 0.1% rare-earth metals, 0 to 0.01% boron, not more than 0.10% phosphorus, not more than 0.03% sulfur, not more than 0.01% oxygen, and a total of 0.01 to 0.30% of either or both titanium and niobium, with the remainder comprising iron and unavoidable impurities. The steel sheet has a dislocation density of 5 × 1013 (1/m2) to 1 × 1016 (1/m2), and comprises, in total volume fraction, at least 90% tempered martensite or lower bainite containing at least 1 x 106 iron carbide/mm2.