| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength steel sheet having both of yield ratio and ductility without causing cost increase or generating problems in manufacturing.SOLUTION: There is provided a high strength steel sheet having a component composition consisting of, by mass%, C:0.1 to 0.6%, Si:0.2 to 3.0%, Mn:0 to 0.6%, Al:0.5 to 2.0% and the balance iron with inevitable impurities and a structure having by area percentage to the total structure, ferrite:70 to 97%, a white area observed by LePera corrosion Vwt:2% or more, retained austenite calculated by an X ray diffraction method VγR:2% or more, difference between the white area observed by LePera corrosion and the retained austenite calculated by the X ray diffraction method &Dgr;V=Vwt-VrR:2% or less, and the balance:one or two of pearlite and bainite and carbon concentration CγR in the retained austenite of 1.5 to 2.5 mass%. |
