Speed Effects in Forging Lubrication

Abstract

The effect of forging speed on the efficiency of selected solid and liquid lubricants was investigated by the axial upsetting of 0.45 percent C steel cylinders and rings at 2000 deg F, at press (30–500 in./min), and at hammer (28–40 ft/sec) speeds. Increasing speed reduced friction both in the unlubricated state and with lubricants capable of forming hydrodynamic (squeeze) films. Carrier fluids used for the application of solid lubricants such as graphite were effective when contact time was kept short enough to prevent their evaporation; residues of a mineral oil carrier appeared to impair the effectiveness of graphite. Squeeze films were most marked with glassy lubricants and caused anomalous material flow by the formation of an immobile lubricant wedge. In general, speed and the condition of the carrier at the moment of deformation were found to be the primary variables that determined the relative performance of forging lubricants.