| 摘要 |
PROBLEM TO BE SOLVED: To provide a thin steel sheet in which heat treatment is not required after blanking, and is excellent in the flatness of a component after blanking as cold-rolled. SOLUTION: The thin steel sheet excellent in flatness after blanking comprises 0.15 to 0.4% C,≤0.5% Si,≤1.0% Mn and≤0.05% P, and the balance substantially Fe, and in which the hardness of the sheet face is 170 to 280 by Hv, and the maximum value▵Hv of the difference in hardness in the width direction is≤20. On hot rolling, if required, the crude bar edge parts are heated, thereafter, finish rolling is performed, and further, coiling is performed in a state where the cooling conditions in the edge parts of the steel sheet in the process of runout cooling after the finish rolling are controlled, so that a hot rolled steel sheet with a microstructure in which the maximum value▵Vf of a difference in ferrite fractions in the width direction is≤30% is obtained. Thereafter, pickling and cold rolling are performed. If required, annealing is performed at 600 to 680°C for≥20 hr after the pickling. COPYRIGHT: (C)2005,JPO&NCIPI
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