PURPOSE: To obtain a deep drawing cold rolling steel plate which is excellent in its surface shape and suitable for an automobile outside plate, by adding Al, etc. to dead low C steel of a specific composition, executing hot rolling, cooling and cold rolling under the specific conditions, and after that, annealing it continuously.
CONSTITUTION: Steel consisting of ≤0.006wt% C, 0.04W0.30% Mn, ≤0.01% N, 2 times of N content W0;15% Al, and the balance Fe and impurities is melt- manufactured. This steel is hot rolled at a finish temperature 830W900°C, is cooled at a mean colling speed 60°C/sec, and is wound up at ≤600°C. Subsequently, it is pickled, is cold-rolled, and is made to pass through a continuous annealing line. Also, with regard to steel contaning ≤0.10% C, 2 times of N content W0.10%, A and more than one kind of Nb and V 3W15 times of C, the same process as above is executed. According to this composition and control for lowering a rolling temperature, it is possible to obtain a cold rolling steel plate which is free from needle-like defect, etc. caused by residual scale, satisfactory in its surface quality and excellent in its deep drawing property.
IRIE TOSHIO
HASHIMOTO OSAMU
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