COLD-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME

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COLD-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME

This abstract first appeared for US patent application 18834966 titled 'COLD-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME

Original Abstract Submitted

This cold-rolled steel sheet has a predetermined chemical composition, in which a metallographic structure at a ¼ depth position, which is a ¼ thickness position from a surface, contains, by volume percentage, retained austenite: more than 1.0% and less than 8.0%, tempered martensite: 80.0% or more, ferrite and bainite: 0% or more and 15.0% or less in total, and martensite: 0% or more and 5.0% or less, and in the metallographic structure, a prior γ grain size is 5.0 μm or more and 25.0 μm or less, and a number density of retained γ on a prior γ grain boundary is 100/mmor less.