| 摘要 |
A steel sheet is provided, including: as chemical components, by mass%, 0.05% to 0.35% of C; 0.05% to 2.0% of Si; 0.8% to 3.0% of Mn; 0.01% to 2.0% of Al; equal to or less than 0. 2% of P; equal to or less than 0.05% of S; equal to or less than 0.01% ofN; and the balance including iron and inevitable impurities, wherein an area ratio of equal to or higher than 50% of a total of a ferrite phase, a bainite phase, and a tempered martensite phase is contained, an area ratio of equal to or higher than 3% of a retained austenite phase is contained, and crystal grains of the retained austenite phase having a number ratio of equal to or higher than 50% satisfy Expression 1, assuming that a carbon concentration at a position of center of gravity is Cgc and a carbon concentration at a grain boundary is Cgb. |
