| 摘要 |
PROBLEM TO BE SOLVED: To provide a cold rolled steel sheet which is useful as a stock for automobile automatic transmissions (such as a separate plate and a friction plate), and to improve a production process thereof. SOLUTION: The cold rolled steel sheet comprises, by weight, 0.15 to 0.25% C,≤0.25% Si, 0.3 to 0.9% Mn,≤0.03% P,≤0.015% S, 0.01 to 0.08% Al,≤0.008% N, 0.01 to 0.05% Ti and 0.002 to 0.005% B, and the balance substantially Fe, and is produced by subjecting a hot rolled sheet having a ferrite grain size of 5 to 15μm to cold rolling at a draft of≥50%. The cold rolled steel sheet which requires no annealing before the cold rolling by the effect of the control of the C content and the composite addition of Ti and B, and is provided with required quality by the process of hot rolling-pickling-cold rolling (at a draft of≥50%) can be obtained. The effect of the reduction in cost by the obviation of annealing is remarkable. The cold rolling can consist of two steps of prerolling (at a draft of≤25%) before the pickling and finish rolling (at a draft of≥25%) after the pickling, and the effect of the remarkable reduction in cost by the improvement of the descale properties in the hot rolled sheet can also be obtained. COPYRIGHT: (C)2004,JPO
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