Friction in cold rolling of a low carbon steel with lubricants

Abstract

Six commercial lubricants are tested during cold rolling of low carbon steel strips. The objectives are to test the ability of the oils to lower the loads on the mill; to determine the dependence of the coefficient of friction on the model used in inverse calculations and to establish the lubrication regimes during the rolling process. The roll separating forces, roll torques and the forward slip are monitored. The reduction and the speed of rolling are taken to be the independent variables. While the viscosities of the oils vary over a fairly large range, their effects on the roll forces, torques and the forward slip are not very pronounced. The oil, which caused the largest reduction of the loads on the mill is a synthetic one with no additives. The coefficients of friction are determined by two mathematical models. While both models show that the coefficients decrease with increasing speeds and reductions, their magnitudes are strongly dependent on the models. It is recommended that when the inverse technique is used to establish the friction coefficients, all three measured parameters: the force, torque and the forward slip be matched by the predicted ones. In all instances boundary or mixed lubrication regimes are in existence. The hydrodynamic region is approached but not reached.