Patent ID: 11174529

Abstract:
A high-strength steel sheet having a microstructure represented by, in area %, martensite: 5% or more; ferrite: 20% or more; and pearlite: 5% or less. A ratio of the number of bulging type martensite grains to the number of martensite grains on grain boundary triple points of a matrix is 70% or more, wherein: the bulging type martensite grain is on one of the grain boundary triple points of the matrix; and at least one of grain boundaries of the bulging type martensite grain, the grain boundaries connecting two adjacent grain boundary triple points of the bulging type martensite grain and grains of the matrix, has a convex curvature to an outer side with respect to line segments connecting the two adjacent grain boundary triple points. An area ratio VM/A0 is 1.0 or more.