| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength hot-dip galvannealed steel sheet having high yield strength, high elongation and high stretch-flangeability.SOLUTION: There is provided the high strength hot-dip galvannealed steel sheet that has a component composition containing, by mass%, C:0.05 to 0.30%, Si:0.1 to 3.0%, Mn:1.0 to 3.0%, P:0.1% or less, S:0.01% or less, N:0.01% or less, Al:0.001 to 0.10% and the balance Fe with inevitable impurities, and that has structure in which an average area ratio of a mixed structure MA composed of martensite and austenite to the whole structure Vis 2 to 5%; an area where an MA area ratio is locally 60% or less of the average area ratio Vis 10% or less by area ratio to the whole structure; the average area ratio of ferrite to the whole structure is 2% or less; the balance is bainite and martensite; and dislocation density is 2.0×10to 8.0×10m. |
