High strength steel sheet having excellent workability and method for manufacturing same

A high strength steel sheet having excellent workability, comprising:

• by wt %, C:
• 0.36 to 0.75%, Si:
• 4.0% or less, Mn:
• 0.9 to 5.0%, Al:
• 5.0% or less, P:
• 0.15% or less, S:
• 0.03% or less, N:
• 0.03% or less, and the balance Fe and unavoidable impurities;
• and
• as microstructures, by volume fraction, 3 to 20% of ferrite which is a soft structure, and 30 to 70% of tempered martensite, 10 to 45% of bainite, and 10 to 40% of retained austenite which are hard structures,
• wherein the high strength steel sheet satisfies the following [Relational Expression 1] and [Relational Expression 2],
• 0.4≤[H]F/[H]TM+B+γ≤0.9 [Relational Expression 1]
• where [H]F and [H]TM+B+γ are nanohardness values measured using a nanoindenter, [H]F is an average nanohardness value Hv of the ferrite which is the soft structure, [H]TM+B+γ is the average nanohardness value Hv of the tempered martensite, the bainite, and the residual austenite which are the hard structures,
• V(1.2 μm,γ)/V(γ)≥0.1 [Relational Expression 2]
• where V(1.2 μm, γ) is a fraction (vol %) of the retained austenite having an average grain size of 1.2 μm or more, and V(γ) is the fraction (vol %) of the retained austenite of the steel sheet.