A study of surface topography, friction and lubricants in metalforming

In this paper are presented the results of investigations concerning the re lation between friction behaviour and surface topography using various lubr icants and initial workpiece surface conditions in ring upsetting and rod e xtrusion processes. The tests were carried out using either a, liquid lubri cant or under clean dry conditions. Two types of workpiece surfaces, random and directional, were prepared by either shotblasting, or EDM or turning t o different levels of surface finish. Not only has the friction effect of l ubricant and initial surface been studied, but also the surface topography of the finished products has been examined in detail, to obtain a better un derstanding of the mechanism of lubrication and surface interaction. It was found that, for random surfaces, smoother ones could retain more lubricant and decrease friction resistance. The experimentation also demonstrated th at turned surfaces were effective in reducing friction, but the final surfa ce finish of the workpiece was not as good as that from random surfaces. (C ) 2000 Elsevier Science Ltd. All rights reserved.