HIGH-STRENGTH COLD-ROLLED STEEL PLATE, HIGH-STRENGTH PLATED STEEL PLATE, METHOD FOR MANUFACTURING HIGH-STRENGTH COLD-ROLLED STEEL PLATE, METHOD FOR MANUFACTURING HIGH-STRENGTH PLATED STEEL PLATE, AND AUTOMOBILE PART

摘要

Provided are: a high-strength cold-rolled steel plate which has a tensile strength (TS) of 980 MPa or more, while having excellent ductility, stretch-flangeability, and bendability; and a method for manufacturing the high-strength cold-rolled steel plate.　The high-strength cold-rolled steel plate has a component composition containing C, Si, Mn, P, S, N, Al, Ti, Nb and B with the remainder comprising Fe and inevitable impurities, satisfies [mol%N]/[mol%Ti]<1, and has a steel structure comprising, by area fraction: 30-60% of a ferrite; 35-65% of a total of tempered martensite and bainite; 15% or less of quenched martensite; 1-10% of retained austenite; 5-40% of a low Mn ferrite having an Mn concentration of at least 0.8×[%Mn], in which (the area fraction of the ferrite)-(the area fraction of the low Mn ferrite) is at least 10%; and less than 3% of remaining structure, wherein the low Mn ferrite has an average crystal grain diameter of 10 μm or less.