EFFECTS OF DEFORMATION SPEED AND TYPE OF ALLOY ON FRICTION AND LUBRICATION BY TIP TEST

The tribological conditions in cold forging operations are extremely severe, especially with high ram speed, due to large surface expansion and normal pressure at the tool/workpiece interface. The effects of deformation velocity and type of alloy were determined in the two sets of experiments carried out in the present study. In the first set, two different deformation speeds of 0.1 and I mm/s were used for the aluminum alloys of 6061-O, 1050-O and copper alloys tests. The results were further confirmed with the second sets of experiments using AA2024 and AA6061 and three deformation speeds of 0.1, 1 and 5mm/s to evaluate the performance of each lubricant under increasing ram speed. Four lubricants such as grease, corn oil, VG100 and VG32 were used. While all the lubricants show a reduction in maximum load with increasing deformation speed, grease shows a rise in the maximum load from zero to a maximum at a deformation speed of I mm/s and then descends gradually to a minimum load at a speed of 5mm/s for AA2024-O and AA6061-O. Since the load reduction seen, with grease as lubricant, is probably due to thermal softening, it will not be considered a desirable lubricant under increasing deformation speed because of the adverse effects on the tooling. It is found that in choosing lubricant for cold forging operations the type of workpiece material and deformation speed should be properly considered. Of the liquid lubricants (corn oil, VG100 and VG32) considered, corn oil shows the best lubricant for cold forging operations of copper, aluminum 6061-O, 1050-O and 2024-0 under increasing speed magnitude.