| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength hot rolled steel sheet excellent in low temperature toughness, uniform elongation and hole expansibility, and having a tensile strength of 780 MP or more, and a production method therefor.SOLUTION: The high strength hot rolled steel sheet excellent in low temperature toughness, uniform elongation and hole expansibility, and having a tensile strength of 780 MP or more is provided which contains, by mass%, C:0.02% to 0.10%, Si:0.01% to 2.0%, Mn:0.5% to 2.5%, P:0.1% to S:0.01%, Al:0.01% to 1.0%, N:0.01% or less, and Ti:0.01% to 0.20%. The high strength hot rolled steel sheet has two-phase structure comprised of structure fraction a ferrite phase of 40% to 90% and the balance a bainite phase by area fraction, an X ray random strength ratio in [211]<011> parallel to a rolling face of the steel sheet and parallel to a rolling direction of 2.5 or less, an average particle diameter of ferrite particles of 5.0 μm or less and a standard deviation of 2.0 μm or less. |
