| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength hot rolled steel sheet excellent in toughness and production method thereof.SOLUTION: The high strength hot rolled steel sheet excellent in toughness and having a yield strength of 700 MPa or more is obtained by having a composition which contains, by mass%, C:0.050% to 0.090%, Si:0.45% or less, Mn:1.20% to less than 1.60%, P:0.03% or less, S:0.005% or less, Al:0.1% or less, N:0.0060% or less, Ti:0.13% to less than 0.20 and the balance Fe with inevitable impurities, the Ti amount of solid solution being 0.04% or more, and having structure which has an area ratio of a bainite phase of 75% or more (including 100%), an area ratio of a ferrite phase of 25% or less (including 0%), an average lath width of the bainite phase of 600 nm or less. |
