COLD-ROLLED STEEL SHEET AND MANUFACTURING METHOD THEREFOR

摘要

A cold-rolled steel sheet has a structure: which has a prescribed component composition; in which the total area ratio of tempered martensite and bainite with respect to the structure as a whole is 95% to 100%; in which there are not more than 0.8/mm2 of prescribed inclusion groups that extend and/or are distributed in a series of points in the rolling direction and are configured from at least one inclusion particle with a long axis of at least 0.3 µm; in which there are not more than 3500/mm2 of carbides of a prescribed size that have Fe as the main component; in which there are at least 0.7 × 107/mm2 of carbides of 10-50 nm diameter that distribute in the interior of the tempered martensite and/or bainite; and in which the mean particle size of prior γ grains is not more than 18 µm.