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|1. (WO2018179387) HOT-ROLLED STEEL SHEET|
|Applicants:||NIPPON STEEL & SUMITOMO METAL CORPORATION
|Title:||HOT-ROLLED STEEL SHEET|
A hot-rolled steel sheet, wherein: the chemical composition, in mass%, is C: 0.07-0.22%, Si: 1.00-3.20%, Mn:0.80-2.20%, Al: 0.010-1.000%, N≤0.0060%, P≤0.050%, S≤0.005%, Ti: 0-0.150%, Nb: 0-0.100%, V: 0-0.300%, Cu: 0-2.00%, Ni: 0-2.00%, Cr: 0-2.00%, Mo: 0-1.00%, B: 0-0.0100%, Mg: 0-0.0100%, Ca: 0-0.0100%, REM: 0-0.1000%, Zr: 0-1.000%, Co: 0-1.000%, Zn: 0-1.000%, W: 0-1.000%, Sn: 0-0.050%, balance: Fe and impurities; the metal structure located at 1/4W or 3/4W from the edge face of the steel sheet and 1/4t or 3/4t from the surface is, in area%, retained austenite: greater than 2% to 10%, martensite≤2%, bainite: 10-70%, pearlite≤2%, balance: ferrite; the mean equivalent circular diameter of the metal phases made of retained austenite/martensite is 1.0-5.0 µm; the mean value for the shortest distance between adjacent metal phases is at least 3 µm; and the standard deviation for nano-hardness is 2.5 GPa or less.