| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-strength hot-dip galvanized steel sheet of≥980 MPa which has a high yield ratio and excellent elongation. SOLUTION: The high yield ratio and high-strength hot-dip galvanized steel sheet having excellent workability and having tensile strength of≥980 MPa comprises C, Si, Mn or the like and has a metallic structure composed of a composite structure containing ferrite and martensite, and in which, in the ferrite structure, provided that the length per unit area of grain boundaries with a crystal orientation difference of≥10°is defined as L<SB>a</SB>and the length per unit area of grain boundaries with a crystal orientation difference of <10°is defined as L<SB>b</SB>, 0.2≤(L<SB>b</SB>/L<SB>a</SB>)≤1.5 is satisfied, provided that the equivalent circle diameter of ferrite grains surrounded by the grain boundaries with a crystal orientation difference of≥10°is defined as D, the average value of D is≤25μm, and further, the area ratio of the crystal grains satisfying D≤30μm among the ferrite grains surrounded by the grain boundaries with a crystal orientation difference of≥10°is≥50%. COPYRIGHT: (C)2010,JPO&INPIT |
