Hydrodynamic lubrication in cold rolling

Abstract

Particular attention has been paid to the effects of roll flattening and to the inlet zone of pressure build-up in the determination of lubricant film thickness in cold rolling. It is shown that under present-day practical conditions, the thicknesses of the lubricant films relative to surface roughnesses are insufficient to maintain full fluid film lubrication.Although the mathematical model predicts a "speed effect" for rolling (plots of rolling load against speed looking like a Sommerfeld diagram for a journal bearing), the speeds involved are much faster than present commercial rates. Thus speed effects in the literature must have been caused by a change over from boundary to mixed lubrication and lubricant puddle entrapment in surface microcrevices. The non-dimensional form of the solutions shows that laboratory experiments rarely approach full-scale mill conditions, thus reflecting the notoriously difficult problem of evaluating commercial metal-working lubricants.