Plate-out behaviors of O/W emulsions for cold rolling in a short time interval

Abstract

O/W emulsions are widely used in tandem cold rolling mills as coolants, in order to reduce friction forces and prevent heat scratches. The lubricating properties may be determined by various factors, and the amount of plated out oil on strip surface is one of the important ones, as well as dynamic concentration mechanics of emulsions at inlet of roll bite, on which much interest has been paid since 1970s. However, plate-out oil film formation has been recognized as a quite important factor in production mill operation, and the understandings of more details are necessary for higher speed and more efficient cold rolling mills. Therefore, the paper is concerned with the plate-out properties, especially the oil film formation in a quite short time. Because the plate-out oil formation is caused through phase transformation of O/W emulsion to oil film, the process may be time dependent, even if the time is quite limited in production high-speed rolling mills. In this paper, firstly a new method to evaluate the amount of plate-out oil is proposed, which makes it possible that the evaluation in quite a short time less than 0.1 s. Then, the time dependency of the oil film formation is clarified, and the amount of plated-out oil increases with time from emulsion supply to strip surface. Also, the influence of oil concentration, oil droplet size of O/W emulsions and other factors are examined by the method, which are compared with the results by conventional test methods.