COOLING METHOD FOR HOT STEEL SHEET

PURPOSE:To decrease the variance in the temp. of a steel sheet after cooling and to obtain a product having a good shape by roughening the front and rear surfaces of the steel sheet before cooling to the prescribed projection height and projection pitch which are approximately uniform in the transverse direction of the sheet. CONSTITUTION:The steel sheet is rolled with rolling rolls of which the projection height of the surface roughness is >=20mumRz and the pitch thereof is >=50mumSm to transfer the surface roughness of the rolling rolls to the surfaces of the steel sheet. The pinch rolls of a leveling device disposed between a rolling installation and cooler or the front stage rolls of the cooler may be used in place of the rolling rolls. A non-contact type surface roughness gage is used to measure the surface roughness of the steel sheet. The resultant steel sheet has the decreased variance in the temp. thereof. The improvement in the steel sheet shape is thus made possible.