HIGH-STRENGTH COLD ROLLED STEEL SHEET HAVING EXCELLENT DEEP- DRAWABILITY AND DUCTILITY AND PRODUCTION METHOD, HIGH-STRENGTH HOT DIP GALVANIZED STEEL SHEET USING THE COLD ROLLED STEEL SHEET AND ITS PRODUCTION METHOD

摘要

PROBLEM TO BE SOLVED: To provide a high-strength cold rolled steel sheet having excellent deep-drawability and ductility by regulating the composition and structure of the steel sheet.;SOLUTION: The high-strength cold rolled steel sheet has a composition comprising, by mass, 0.05 to 0.2% C, 0.1 to 2.0% Si, 0.5 to 3.0% Mn, ≤0.10% P, ≤0.02% S, 0.005 to 1.5% Al and ≤0.02% N, and the balance Fe with inevitable impurity elements, also has a composite structure composed of ferrite in an amount of ≥70 vol.%, retained austenite in an amount of ≥2 vol.% and bainite, and has a Lankford value (r value) of ≥1.1.;COPYRIGHT: (C)2007,JPO&INPIT