STEEL SHEET AND METHOD FOR MANUFACTURING STEEL SHEET

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STEEL SHEET AND METHOD FOR MANUFACTURING STEEL SHEET

This abstract first appeared for US patent application 18837473 titled 'STEEL SHEET AND METHOD FOR MANUFACTURING STEEL SHEET

Original Abstract Submitted

This steel sheet includes, in mass % C: 0.15% to 0.50%, Si: 0.01% to 1.00%, Mn: 1.00% to 3.00%, P: 0% to 0.0200%, S: 0.0001% to 0.0200%, Al: 0.001% to 0.100%, and N: 0% to 0.0200%, with the remainder being Fe and impurities, in which a metallorgraphic structure has an area fraction of 0% to 10.0% of retained austenite and 0% to 5.0% of pearlite, ferrite, and bainite in total, with the remaining structure being martensite and tempered martensite, a maximum diameter of MnS predicted by extreme value statistics is 30 μm or less, a surface roughness Ra is 5 μm or less, and a surface layer has a Vickers hardness of greater than or equal to a tensile strength TS (MPa) of the steel sheet×0.25.