Patent ID: 8177924

Claim:
A high-strength steel sheet comprising: a metallic structure consisting of a ferrite phase and a hard second phase dispersed in the ferrite phase; the hard second phase in the metallic structure having an area ratio of 30 to 70%; and the ferrite composed of grains L having a grain size of greater than 1.2 μm and grains s having a grain size of less than 1.2 μm, the grains s having an area ratio of 15 to 90% in the ferrite phase, wherein ds is an average grain size of the grains s of the ferrite of which grain sizes are not more than 1.2 μm, dL is an average grain size of the grains L of the ferrite of which grain sizes are more than 1.2 μm, and ds and dL satisfy the following equation (1): dL/ds≧ 3 (1).