To produce cold rolled stainless steel sheets efficiently in high speed rolling, surface brightness must be improved. The surface brightness of the sheets is strongly affected by oil-pits which occur on the surface of the sheets in cold rolling. As the number of oil-pits decreases, the surface brightness of the sheets is improved.
In this study, the morphology of oil-pits in actual cold rolling is observed by a microscope and SEM (Scanning Electron Microscopy). The effect of the surface roughness of the mother sheet on the occurrence of oil-pits in cold rolled sheet is examined with a laboratory-scale rolling mill.
The results obtained are as follows :
(1) Oil-pits occur at the bottom of micro-pits on the surface of the mother sheet, at the bottom of scratches which are marks due to the surface roughness of rolls and in the flat surface around the micro-pits and the scratches.
(2) It can be explained that oil pits in the flat surfaces around micro-pits are formed by the squeezing of rolling oil from the micro-pits.
(3) It can be explained that oil-pits at the bottom of the micro-pits and the scratches are caused by enclosure of rolling oil in the micro-pits and the scratches.
