Stability of contact line accompanied by solidification

Abstract

The cooling rate in actual roll casting systems is markedly decreased by contact resistance between the chilled roll and melt (or solidified shell). In this study, focusing on the dynamic behavior of a contact line, the mechanism generating the contact resistance is experimentally investigated using liquid paraffin as a melt and flat plates as chilled surfaces. The experimental results obtained show that the smoothness of the solidified shell is closely related to the stability of the contact line. The range of immersion velocities of the plate, and stable contact lines appear only at middle immersion velocities. The range of immersion velocity in which stable contact lines appear becomes narrower with increasing undercooling degree of the plate. The unstable contact line appearing at high immersion velocities results from the dynamic nonwetting condition at the contact line. The unstable contact line at low immersion velocities is closely related to the formation of a solidified shell in the vicinity of the contact line and to the interface temperature upon contact between the melt and the chilled surface