High-strength cold-rolled steel sheet, high-strength hot-dip galvanized steel sheet, and high-strength hot-dip galvannealed steel sheet excellent in formability and shape fixability, and methods for manufacturing them

A cold-rolled steel sheet, comprising, in mass percent, based on the chemical composition:

• C in a content of 0.1% to 0.3%;
• Si in a content of 1.0% to 3.0%;
• Mn in a content of 0.5% to 3.0%;
• P in a content of 0.1% or less;
• S in a content of 0.03% or less;
• Al in a content of 0.01% to 1.0%;
• and
• N in a content of 0.01% or less,
• with a remainder being iron and inevitable impurities,
• the steel sheet having a steel microstructure meeting conditions given as follows:
• a total content of bainitic ferrite (BF) and tempered martensite (TM) of 65% in area percent or more;
• a content of fresh martensite (M) is from 3% to 18%;
• a content of retained austenite is from 5% or more;
• and
• a content of polygonal ferrite (F) is 5% or less,
• the steel microstructure further meeting a condition given as follows:
• an average KAM<1.00° is 0.50° or more,
• wherein the “average KAM<1.00°” denotes is an average of kernel average misorientation (KAM) values (misorientation values, in “degree (°)”) in a region of less than 1.00° as measured at two or more points;
• and
• the steel sheet having a tensile strength of 980 MPa or more.