Effect of Oil Film Thickness on Lubrication Property in Hot Rolling

In hot rolling, lubrication between the work roll and hot strip plays an important role in reducing rolling force and protecting the work roll surface. However, the tribological behavior in hot rolling has not been clarified sufficiently. In this work, the effects of oil amount on the coefficient of friction in hot rolling were investigated in comparison with the case of cold rolling. The oil amount in hot rolling was measured by the amount of oil remaining on the work roll surface after rolling. The results of rolling tests clarified the following points: The coefficient of friction is reduced adequately with a small amount of oil. If the oil amount is increased, a few small oil-pits will form, but no further decrease in the coefficient of friction will be achieved. It is suggested that boundary lubrication is controlling in hot rolling, which is different from the case of cold rolling.