Measurements of friction during hot rolling of aluminum strips

In order to establish the dependence of the coefficient of friction on rolling speed and the reduction, commercially pure aluminum strips were rolled at 500°C, using a 2% oil/water emulsion as the lubricant. The roll separating forces, roll torques, the forward slip, the roll pressure and the interfacial shear stress were measured as a function of the reduction and the rolling speed. The coefficient of friction was determined from the shear stress and the roll pressure distributions and its magnitude was validated independently. The coefficient of friction was found to increase with reduction and, in general, decrease with rolling speed. The adhesion theory of friction has been used to explain the observations.