| 摘要 |
<p>This invention provides a steel sheet which is soft and has excellent formability and quench hardenability, and a method for manufacturing the same. Provided is a steel sheet, containing: a composition, containing, by mass %, C: 0.3 to 0.7%, Si: 0.1% or lower, Mn: 0.20% or lower, P: 0.01% or lower, S: 0.01% or lower, Al: 0.05% or lower, N: 0.0050% or lower, balance Fe, and inevitable impurities; and a microstructure containing ferrite, graphite, and cementite, in which the total volume ratio of ferrite, graphite, and cementite based on the whole microstructure is 95% or more, the volume ratio of graphite (ratio of graphite) based on the total of graphite and cementite is 5% or more, and the mean grain diameter of graphite and cementite is 5 µm or lower or a steel sheet in which the total volume ratio of graphite and cementite present in ferrite grains based on the total of graphite and cementite is 15% or lower.</p> |
