Thin steel plate and a method of manufacturing the same automotive excellent notched fatigue strength

摘要

PROBLEM TO BE SOLVED: To provide a thin steel sheet for an automobile excellent in notch fatigue strength, and to provide a production method therefor.;SOLUTION: The thin steel sheet for automobile having excellent notch fatigue strength consists 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, ≤0.01% S and 0.005 to 1% Al, and the balance Fe with inevitable impurities. The average value of the X-ray random intensity ratios in the orientation groups of {100}011 to {223}110 in the sheet surface thereof at an arbitrary depth till 0.5 mm from the outermost surface in the sheet thickness direction is ≥2, and also, the average value of the X-ray random intensity ratios in the three orientations of {554}225, {111}112 and {111}110 is ≤4. The steel sheet has a sheet thickness of 0.5 to 12 mm. In the method for producing the same steel sheet, the steel having the above composition is rolled in the temperature region of the Ar₃ transformation temperature +100°C or lower at a total rolling reduction rate of ≥25%.;COPYRIGHT: (C)2003,JPO