MEASUREMENTS OF FRICTION DURING THE WARM ROLLING OF ALUMINUM

The parameters and variables that affect the normal pressure and the friction stress at the roll/strip contact surface during flat rolling include those determined by the material, the rolling mill and the process. Of the process parameters, the least researched one appears to be the temperature and that is the concern of the present study. Specifically, it is the dependence of the coefficient of friction in the roll bite on the temperature there that is addressed. The dependence of the roll-separating forces, roll torques, forward slip, interfacial normal and shear stresses and hence the coefficient of friction, on the reduction are measured and reported for nominal temperatures of 22, 100 and 300-degrees-C, the actual surface temperatures of the strips during the pass being calculated using an elastic-plastic finite element model of the process. The measured values of the interfacial stresses are substantiated independently and are found to be reasonable. The results may enable engineers in the aluminum industry to model the flat-rolling process with some confidence, using the experimentally developed values of the coefficient of friction in the roll gap.