| 摘要 |
Provided is a steel sheet which has a chemical composition containing, in terms of mass%, 0.05-0.35% C, 0.05-2.0% Si, 0.8-3.0% Mn, and 0.01-2.0% Al and having contents of P, S, and N reduced to 0.1% or less, 0.05% or less, and 0.01% or less, respectively, with the remainder comprising iron and incidental impurities, and which contains a ferrite phase, a bainite phase, and a tempered martensite phase in a total amount of 50% or more in terms of areal proportion and contains a retained austenite phase in an amount of 3% or more in terms of areal proportion, and in which at least 50% by number of the crystal grains of the retained austenite phase satisfy relationship 1, wherein Cgc is the concentration of carbon in an area located at the center of gravity and Cgb is the concentration of carbon in an area located at the grain boundary. |
