| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength hot dip galvanized steel sheet having excellent ductility and stretch flangeability. SOLUTION: The high strength hot dip galvanized steel sheet has a steel composition comprising 0.04 to 0.13% C, 0.12 to 1.0% Si, 0.5 to 2.5% Mn,≤0.1% P,≤0.07% S,≤1.0% Al and≤0.007% N, and has a steel sheet structure having crystal grains where the area ratio of polygonal ferrite is≥50%, other than the polygonal ferrite, the respective crystal grains are composed of a single phase of martensite, bainite or retained austenite, or a mixed phase thereof, the area ratio of he bainite is 15 to 48%, the total area ratio of the martensite and retained austenite is 2 to 30%, the area ratio of the retained austenite is 0 to 5%, (the area ratio of the martensite and retained austenite)/(the area ratio of the bainite)≤1/2, and further, the area ratio of the crystal grains composed of the martensite and/or retained austenite is 0 to 5%. COPYRIGHT: (C)2009,JPO&INPIT |
