The effect of roll roughness on the rolling parameters during cold rolling of an aluminum alloy

The effects of the roughness of the work roll on the roll force, roll torque and the forward slip are investigated. Using a light mineral seal oil with 5% oleyl alcohol as a boundary additive, 6061-T6 aluminum alloy strips were cold rolled at various speeds to various reductions. The roll roughness, obtained by sand blasting, was varied from a low of 0.3–2.4 μm and the roll separating force, roll torque and the forward slip were measured. The coefficient of friction was calculated by Hill’s formula and the friction factor was evaluated by using the upper bound approach. The roll and the rolled surfaces were examined. The process conditions under which starvation of the contact may have occurred were studied. The frictional mechanisms were identified. High roughness appeared to increase the possibility of insufficient lubrication at the interfaces. While both adhesive and ploughing forces were present in all instances, the ploughing forces became dominant at higher rolling speeds. The contribution of ploughing to frictional resistance increased as the roll roughness increased to a certain value and beyond that its behaviour depended on the rolling speed.