COLD ROLLED HIGH STRENGTH THIN-GAUGE STEEL SHEET EXCELLENT IN ELONGATION AND HOLE EXPANDIBILITY

摘要

PROBLEM TO BE SOLVED: To provide a high strength thin steel sheet having excellent elongation and hole expansibility which has a tensile strength of ≥500 MPa, and to provide a method for producing a high strength thin steel sheet having excellent elongation and hole expansibility capable of producing the same on an industrial scale.;SOLUTION: The high strength thin steel sheet having excellent elongation and hole expansibility has a composition comprising, by mass, 0.03 to 0.25% C, 0.4 to 2.0% Si, 0.8 to 3.1% Mn, ≤0.02% P, ≤0.02% S, ≤2.0% Al and ≤0.01% N, and the balance Fe with inevitable impurities, and has a microstructure composed of ferrite in 10 to 85% by area ratio, retained austenite in 1 to 10% by volume ratio, tempered martensite in 10 to 60% by area ratio, and the balance bainite.;COPYRIGHT: (C)2006,JPO&NCIPI