High strength steel sheet having excellent formability and manufacturing method thereof

A manufacturing method of a high strength steel sheet, comprising:

• hot rolling a steel slab comprising, by weight, C:
• 0.001% to 0.004%, Si:
• 0.5% or less (excluding 0%), Mn:
• 1.2% or less (excluding 0%), P:
• 0.005% to 0.12%, S:
• 0.01% or less, N:
• 0.01% or less, acid soluble Al:
• 0.1% or less (excluding 0%), Ti:
• 0.01% to 0.04%, a remainder of Fe, and unavoidable impurities, to obtain a hot-rolled steel sheet;
• coiling the hot-rolled steel sheet at a temperature within a range of 450° C. to 750° C.;
• cold rolling the coiled hot-rolled steel sheet at a reduction ratio of 75% or more to obtain a cold-rolled steel sheet;
• heating the cold-rolled steel sheet to an annealing temperature within a range of 830° C. to 880° C., and continuous annealing the heated cold-rolled steel sheet at the annealing temperature for an annealing time of 30 to 80 seconds;
• cooling the continuous annealed cold-rolled steel sheet to a temperature within a range of 650° C. or lower at a rate of 2 to 10° C./sec;
• and
• temper rolling the cooled cold-rolled steel sheet at a reduction ratio of 0.3% to 1.6%, and
• wherein an average heating rate from a temperature (recrystallization start temperature+20° C.) to the annealing temperature at a time of heating the cold-rolled steel sheet is 5° C./sec or lower.