Enhanced Modelling of Friction and Lubrication in Cold Strip Rolling
Sprache des Titels:
Proceedings of the 9th International and 6th European Rolling Conference 2013
In this work, a numerical simulation model for the mixed lubrication regime in cold strip rolling is presented. By calculating the pressure and shear stress distributions along the interface between the strip and the work roll simultaneously and consistently, the highly empirical coefficient of friction applied in conventional cold rolling models is replaced by the ratio of shear stress and pressure. Both the inlet zone, where film formation takes place, as well as the zone of strip bulk plastic deformation, are considered. In the latter zone, the interaction between lubricant flow, strip and work roll surfaces inside the roll bite and the developing fractional area of contact are the governing effects for determining the relative ratios of boundary shear stress and lubricant shear stress. In the inlet zone, particular emphasis was put on modelling the lubricant and its composition, which influence the thickness of the entrained lubricant film. Film formation for both neat oils and emulsions is considered based on widely accepted theories of plate-out layer formation on the strip and work roll surfaces. A robust and stable solution concept was developed to solve the underlying equations describing fluid motion and plasto-hydrodynamic coupling. The model has been validated by comparing rolling force predictions to mill data measurements from four stands of a tandem cold rolling mill at voestalpine. Selected validation calculations are presented in the paper.