Abstract
Oil-in-water (O/W) emulsion has been widely used as a coolant and a flame-retardant lubricant in the rolling mill. Understanding of the physical properties of the oil film between the roll and strip is necessary because it affects the rolling productivity and surface quality of the sheets. The oil film generally consists of ‘plate-out oil’ and ‘supplied oil’ directly introduced from an O/W emulsion nozzle as oil droplets. However, the detailed mechanism of the oil film formation is still unclear. In this study, we investigated the thickness of plate-out oil on a roller in rolling process and the thickness of oil film formed between ball and disk using a disk-on-ball apparatus with an optical interferometer with changes to the rolling speed, particle size and concentration of the O/W emulsion. As a results, when a volume of plate-out oil was sufficient, the oil film thickness decreased by supplying O/W emulsion because of the re-emulsifying. When the plate-out volume was insufficient, the oil film thickness became thicker just after a high-concentrated O/W emulsion with a large particle size was supplied. In addition, the oil film thickness became thinner when the sliding speed became higher as a result of a growth of vortex which occurred around the inlet zone.
