Gianfranco Palumbo

Lubrication in the cold rolling process plays a key role in withstanding the loads between the strip and the work rolls, as well as in ensuring high surface quality, tight geometric tolerances, and large thickness reductions. Most of the currently used lubricants have synthetic or semi-synthetic formulations, but the research for greener alternatives, able to guarantee very low environmental impact during both the preparation (use of natural raw components) and the disposal, is increasingly playing a key role. In the present work, the lubricating performance of a natural-based emulsion and a mineral-based one has been assessed in terms of rolling forces, Coefficient of Friction (CoF) at the roll/strip interface, and work rolls’ wear. Data from the two-stands reversing cold mill (RCM) at the Marcegaglia plant (Ravenna, Italy) were used for comparing the investigated lubricants. In particular, data about the forces and the wear evolution during the rolling process were acquired over quite a long period (11 months), thus being related to a large type of steel. In addition, the CoF was evaluated using the CSM High-Temperature pin-on-disk Tribometer (THT) and replicating the operating conditions in which the two lubricants are currently used. Laboratory tests revealed that the green lubricant is characterized by a better lubricating performance (the CoF value of the green lubricant is about 10% lower than the one of the semi-synthetic formulation). Such a result was confirmed by both the rolling forces (an average reduction equal to 5.6% was obtained by using the green lubricant) and by the work rolls’ wear (less frequent maintenance of the rolls), thus determining a large and valuable reduction of the process-related costs.