| 摘要 |
PURPOSE: To produce a steel sheet for hard can small in plane anisotropy of (r) value while holding the target hardness and proof stress by hot-rolling a low carbon steel slab and applying two times of cold-rolling at a specific draft interposing recrystal continuous annealing after pickling. CONSTITUTION: The continuous casting steel slab containing, by wt., <0.15% C, <0.04% Si, <0.6% Mn, <0.03% P, <0.03% S, <0.15% Al, <0.01% N is hot-rolled at Ar3 transformation point-900 deg.C finish temp. to obtain the sheet material, and oxide scale on the surface is removed by the pickling. Thereafter, a first time of the cold-rolling is executed at the draft R1 shown with the equation I (wherein, (e) is the constant decided with C and Mn contents in the blank steel slab, (f) is the constant decided with C content in the blank steel slab, R2 is the draft of a second cold-rolling andΔr is the target value of the anisotropy in the surface of Lankford value), and then, the recrystal continuous annealing is executed at the recrystallized temp.-the A1 transformation point. Successively, the second time of the cold-rolling is executed at the draft R2 shown with the equation II (wherein (a) is the constant decided with C content in the refining degree of the product steel sheet and the blank steel slab and S is the target value in the hardness level of the product steel sheet).
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