COLD-ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING SAME, AND HOT-STAMP FORMED BODY

摘要

A cold-rolled steel sheet according to the present invention contains specific chemical components, wherein the metallic structure of the steel sheet comprises ferrite at an area ratio ranging from 30 to 90%, martensite at an area ratio of 0% or more and less than 20%, perlite at an area ratio ranging from 0 to 10%, retained austenite at a volume ratio ranging from 5 to 20% and a remainder structure made up by bainite both before and after hot stamping, and wherein the hardness of the retained austenite as measured on a nanoindenter fulfills the relationship represented by the formulae H2/H1 < 1.1 and sHM < 20 and the relationship represented by the formula TS × El = 20000 MPa·% is fulfilled both before and after hot stamping.