PURPOSE: To manufacture a cold rolled steel sheet free from surface flaws with an improved yield, by applying a skin pass rolling work simultaneously to both sides of a cold rolled steel sheet with a bright roll for one side and a dull roll for another side, wherein the surface roughnesses of the bright roll and the dull roll are respectively prescribed.
CONSTITUTION: A skin pass rolling work is applied to a cold rolled steel sheet, both sides at the same time, that is, one side by a bright roll (the upper roll, for example) and another side by a dull roll (the lower roll, for example). The bright surface of the bright roll is finished to <1.0μm Hmax surface roughness and the surface of the dull roll is finished to ≥3μm Hmax surface roughness; by using these rolls a bright steel sheet free from the surface flaws is manufactured. The present method is extremely easily practicable, and prevents the generation of surface flaws which is considered as a fatal deficiency of manufacture of a bright steel sheet. The dull pattern transferred to the rear side of the sheet displays an effect of improving a press formability.
TANABE SHINZOU