STEEL SHEET, MEMBER, AND METHODS FOR MANUFACTURING THE SAME
Abstract:
A steel sheet has a chemical composition containing, by mass %, C: 0.20% or more and 0.40% or less, Si: more than 1.0% and 3.0% or less, Mn: 1.5% or more and 3.5% or less, P: 0.002% or more and 0.010% or less, S: 0.0002% or more and 0.0020% or less, sol. Al: 0.40% or less (not including 0%), and N: 0.0100% or less, with the balance being Fe and incidental impurities; and a steel microstructure containing, in area fraction, tempered martensite: 45% or more and 83% or less, bainite: 15% or more and 53% or less, and retained austenite: 2% or more. Carbides in the tempered martensite have an average particle size of 0.40 μm or less, an average amount of C in the retained austenite is 0.5% by mass or more, and a tensile strength is 1,470 MPa or more.
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