Friction in cold rolling of a low carbon steel with lubricants

Six commercial lubricants are tested during cold rolling of low carbon stee l strips. The objectives are to test the ability of the oils to lower the l oads on the mill; to determine the dependence of the coefficient of frictio n on the model used in inverse calculations and to establish the lubricatio n regimes during the rolling process. The roll separating forces, roll torq ues and the forward slip are monitored. The reduction and the speed of roll ing 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, tor ques and the forward slip are not very pronounced. The oil, which caused th e largest reduction of the loads on the mill is a synthetic one with no add itives. The coefficients of friction are determined by two mathematical models. Whi le both models show that the coefficients decrease with increasing speeds a nd reductions, their magnitudes are strongly dependent on the models. It is recommended that when the inverse technique is used to establish the frict ion 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 app roached but not reached. (C) 2000 Elsevier Science S.A. All rights reserved .