High strength cold rolled steel sheet and high strength alloyed hot dip galvanized steel sheet with excellent processability

摘要

PROBLEM TO BE SOLVED: To provide a high strength cold rolled steel sheet excellent in processability and capable of securing tensile strength (TS) of 980 MPa or more, strength-elongation balance (TS×EL) of 25000 MPa % or more and elongation flange property (λ) of 20% or more.SOLUTION: There is provided a high strength cold rolled steel sheet having a component composition containing, by mass%, C:0.10 to 0.50%, Si:1.0 to 3.0%, Mn:1.0 to 3.0%, Al:0.001 to 0.10% and the balance iron with inevitable impurities and a structure consisting of, by area percentage to the total structure, polygonal ferrite of 35% or more, tempered martensite of 5% or more, bainitic ferrite of 5% or more, MA of 5% or more and a total of the polygonal ferrite and the MA of 80% or less with MA having aspect ratio of 3.5 occupying 30 to 70% by number percentage to the total MA.SELECTED DRAWING: None