HIGH STRENGTH STEEL THIN SHEET EXCELLENT IN FATIGUE CHARACTERISTIC, HARDENABILITY IN COATING/BAKING AND COLD-AGING RESISTANCE, AND METHOD FOR PRODUCING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a high strength thin steel sheet which is used for car parts to be press-worked and is excellent in fatigue characteristic, hardenability in coating/baking and cold-aging resistance, and to provide a method for producing the high strength thin steel sheet.;SOLUTION: The high strength thin steel sheet excellent in the fatigue characteristic, the hardenability in the coating/baking and the cold-aging resistance, has the steel composition composed by mass% of 0.01-0.20% C, ≤2.0%Si, ≤0.05% Al, 0.1-3.0% Mn, ≤0.1% P, 0.0005-0.01% S, 0.005-0.05% Nb, 0.002-0.015% N, 0.3-1.5% Cr and the balance Fe with inevitable impurities, and satisfies the following formula (1), 0.046×√([N]×10000)+20[Cr]0.058×√([N]×10000)+0.70...(1) to N concentration: [N] and Cr concentration: [Cr], and has ferrite as the main phase and ≤25μm ferrite grain diameter.;COPYRIGHT: (C)2007,JPO&INPIT