| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength steel sheet having excellent workability, in which bulging formability and stretch flange formability are effectively improved.SOLUTION: A high strength steel sheet has a composition including, by mass, 0.11 to 0.16% C, 0.7 to 1.5% Si, 1.0 to 2.0% Mn, ≤0.05% P, ≤0.005% S and ≤0.07% Al, and the balance Fe with inevitable impurities, and further has a metallic structure composed of ferrite as the main phase and a second phase including retained austenite of 5 to 15% by volume fraction to the whole of the structure, and the average particle spacing of the second phase is controlled to ≤5.0 μm. |
