The influence of lubricant viscosity in cold work forward extrusion using micro-pits tool

Abstract

The present research concerns on the study of the effects of micro–pits arrays formed on taper die using cold forward plane strain extrusion experiments. Each pit was of reverse pyramids configuration having 330 microns diagonal length. The pits were 860 microns apart each others. Two additive free paraffinic mineral oils with low viscosity (P2) and high viscosity (P3) were used in this experimental work. The experimental results were compared with the results obtained from the plane strain extrusion experimental works with taper die without micro–pits (NA). The experimental results focused on the extrusion load, billet surface roughness and billet grid pattern on inclination slope. From the results, the existence of the micro–pits array on the taper die surface affected the extrusion load. At the same time, the micro–pits array affected the extruded billet surface roughness after the experiments. From this experiment, we could conclude that the micro–pits formed on the taper die (PA) would control the frictional constraint on the taper die compared to those without the micro–pits (NA). However, high viscosity lubricant (P3) was found to cause more effects compared to low viscosity lubricant (P2).