Patent ID: 11472159

Abstract:
A high strength steel sheet comprising a center part of sheet thickness and a surface soft part formed at one side or two sides of the center part of sheet thickness, having metal structures of the center part of sheet thickness comprising, by area ratio, tempered martensite: 85% or more, one or more of ferrite, bainite, pearlite, and retained austenite: total of less than 15%, and as-quenched martensite: less than 5%, and additionally having metal structures of the surface soft part comprising, by area ratio, ferrite: 65% or more, pearlite: 5% or more and less than 20%, one or more of tempered martensite, bainite, and retained austenite: total of less than 10%, and as-quenched martensite: less than 5%, wherein a Vickers hardness (Hc) of the center part of sheet thickness and a Vickers hardness (Hs) of the surface soft part satisfy 0.50≤Hs/Hc≤0.75.