PURPOSE: To obtain a cold rolled steel sheet which has a good press formability and has excellent sharpness after painting by working rugged patterns consisting of may parallel lines intersected with each other on a roll surface by a laser beam and transferring the patterns to the steel sheet by means of such roll.
CONSTITUTION: The rugged patterns consisting of the many parallel lines intersected with each other are worked on the roll surface by a combination of the rotation of the roll and the lateral movement of a laser beam machine. Said patterns are transferred by means of the roll onto the steel sheet. The stagnation of a lubricating oil is thereby uniformized over the entire surface and, therefore, the press formability is good. Since the patterns are regular and uniform, the painting is uniformly executed and the sharpness after the painting is improved.
SEKIYA HIROSHI
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