Steel Sheet And Method For Manufacturing Same

Abstract: This steel sheet has a specified chemical composition, in which a microstructure located at a position corresponding to the depth of 1/4 of the thickness of the steel sheet from the surface contains, in terms of volume fractions, 0% to 50% of ferrite, 6% to 30% of retained austenite, 5% to 60% of bainite, 5% to 50% of tempered martensite, 0% to 10% of fresh martensite and 0% to 5% of perlite, the ratio of the grains of the retained austenite each of which has an aspect ratio of 2.0 or more in all of grains of the retained austenite is 50% or more and the number density of inclusions and precipitates each having a grain diameter of 1 µm or more is 30 grains/mm2 or less at the aforementioned position corresponding to the depth of 1/4 of the thickness of the steel sheet from the surface, the average distance between Mn-rich regions in the direction orthogonal to the rolling direction is 300 µm or less at a position corresponding to the depth of 1/20 of the thickness of the steel sheet from the surface, and the standard deviation of Mn concentrations in the retained austenite is 0.40% or less.

Patent Information

Applicants

Inventors

Specification

Documents

Application Documents