The effect of lubricant viscosity and material properties on friction effects in the roll gap and their influence on rolling conditions and product surface quality was investigated and theoretically analyzed. Hydrodynamic and boundary friction are determined by the hydrodynamically entrapped amount of lubricant and by the surface roughness of both the strip and the roll. Rolling tests with thin aluminium sheets are presented where the main parameters have been systematically varied for i) the hydrodynamic effect, i.e. the rolling speed, base viscosity and yield stress, and ii) for the surface effect, i.e. the surface roughness and its orientation. A theoretical model for the entrained oil film thickness has been developed, which accounts for both effects. The changes in friction conditions are correlated with significant rolling parameters, using dimensionless similarity numbers, and alterations of the surface structures of the rolled test sheets.
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