Lubrication in Cold Strip Rolling in the ‘Mixed’ Regime

Abstract

Lubrication in metal rolling in the mixed lubrication regime has been considered. An inlet analysis has been used to calculate the film thickness and area of contact ratio in the bite, taking into account the effect of roughness on the pressure build-up and the effect of the bulk deformation on the crushing of asperities. The film thickness with rough contact is most strongly dependent on the variables which determine the film thickness with smooth contacts, that is, roiling speed, oil properties and inlet geometry, but the effect of yield stress, strip thickness, roughness geometry and inlet tension are also examined. In a separate calculation hydrodynamic theory has been used to estimate film thickness under the ‘contact’ areas. These two calculations have been combined with recent measurements of oil properties to estimate friction-slip relations when rolling thin aluminium foil. These calculations provide quantitative information on friction conditions to help model the rolling process and to estimate the strip surface quality.