Tribological characterization and development of coefficient friction in high surface area expansion ratio

A new, simulative test of friction and lubrication in cold forging is developed by the authors. The test is based on a backward can extrusion process in which the workpiece rotates relatively to the conical punch. An analytical model is presented determining the friction stress from the measured torque during testing combined with an analysis of the sliding velocity distribution along the punch nose. The latter is determined by FE analysis of the test. Results show friction stress for unalloyed low C-steel provided with different types of lubricants, i.e. phosphate coating plus soap, phosphate coating plus MoS2 and single bathe lubrication with PULS and aluminum provided with 6 different lubricants. The new test is so severe, that it is possible to break down the best lubrication systems for cold forging of steel and aluminum.