High ductility hot-rolled steel sheet and method of manufacturing the same excellent low cycle fatigue strength

摘要

PROBLEM TO BE SOLVED: To provide a high ductility hot rolled steel sheet having excellent low cycle fatigue strength and to provide a production method by which the steel sheet can inexpensively and stably be produced.;SOLUTION: This steel sheet is composed of steel having a composition containing 0.01 to 0.3% C, 0.01 to 2% Si, 0.05 to 3% Mn, ≤0.1% P and ≤0.01% S, containing Al and N by ≤0.2% Al and 0.001 to 0.1% N also so as to satisfy 0.52Al/N≤10, further containing one or more kinds selected from Cr, Mo and V by ≤2.5% Cr, ≤1% Mo and ≤0.1% V also so as to satisfy (Cr+3.5Mo+39 V)≥0.1, and the balance Fe with inevitable impurities, whose microstructure is composed of a composite one containing retained austenite of 5 to 25% by volume fraction, and the balance mainly ferrite and bainite, and the area ratio of a cell structure in the dislocated structure dislocated by ferrite obserbed after a fatigue test is ≤50%.;COPYRIGHT: (C)2002,JPO