| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a hot rolled steel sheet excellent in uniformity in a coil and used as a base material for a cold rolled steel sheet for two-piece can. SOLUTION: A continuously cast slab, having a composition containing, by weight, 0.015-0.05% C, <=0.1% Si, 0.1-1.0% Mn, <=0.02% P, <=0.02% S, 0.02-0.15% sol.Al, and <=0.005% N, is roughed in the temperature region not lower than the Ar3 transformation point at >=70% draft into a bar stock, and the degree of flatness of the bar stock is straightened. Subsequently, on the entry side of a hot finishing mill, the finish rolling entry temperature of the bar stock is regulated by the application of heating to the edge part alone by an edge heater and heating to the whole in a width direction by an induction heating device. Then, the hot finish rolling is performed so that the finish rolling delivery-side temperature becomes 880 to 910 deg.C from the head end of a steel strip to its tail end and also finish sheet thickness becomes <=2.3 mm, and the resultant steel sheet is coiled at 600 to 700 deg.C. By this method, the extra thin hot rolled steel sheet, where average grain size is regulated to 12 to <30μm and also the ratio between the average grain size (Dte) in the width-direction edge part at the longitudinal-direction head end of the steel strip and the average grain size (Dmc) in the width-direction central part in the longitudinal direction central part is regulated to 0.5-2.0, can be obtained.
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