High tensile strength hot rolled steel sheet having excellent formability and method for manufacturing the same

A method for manufacturing a high tensile strength hot rolled steel sheet having excellent formability, comprising preparing a steel material, subjecting the steel material to hot rolling including rough rolling and finish rolling, cooling after completion of the finish rolling, and coiling to obtain a hot rolled steel sheet, the method further comprising:

• preparing the steel material to have a composition including by mass %,
• C:
• 0.07% to 0.13% (inclusive of 0.07% and 0. 13%),
• Si:
• 0.3% or less,
• Mn:
• 0.5% to 2.0% (inclusive of 0.5% and 2.0%),
• P:
• 0.025% or less,
• S:
• 0.005% or less,
• N:
• 0.0060% or less,
• Al:
• 0.06% or less,
• Ti:
• 0.08% to 0.14% (inclusive of 0.08% and 0. 14%),
• V:
• 0.15% to 0.30% (inclusive of 0.15% and 0. 30%),
• solute V:
• 0.04% to 0.1% (inclusive of 0.04% and 0.1%),
• solute Ti:
• 0.05% or less, and
• remainder consisting of Fe and incidental impurities;
• setting finish rolling completing temperature in the finish rolling to be equal to or higher than 880° C.;
• setting the average cooling rate in the cooling process to be at least 20° C./s;
• and
• setting coiling temperature in the coiling to be 580° C. or higher,
• wherein contents of C, Ti, V, S and N satisfy formula (1) and formula (2):
• Ti≧0.08+(N/14×48+S/32×48) (1)
• 0.8≦(Ti/48+V/51)/(C/12)≦1.2 (2)
• wherein C, Ti, V, S, and N represent contents (mass %) of corresponding elements, respectively.