FRICTION AND LUBRICATION IN HOT METAL DEFORMATION.

A study was conducted to investigate the frictional behavior of metals in hot metal deformation. The purpose of the study was to gain a better understanding of friction at high pressures and temperatures characteristic of metal-working processes. A test technique was developed in which a thin foil was compressed between a hardened anvil and a flat plate. Friction was determined by applying a tangential force to one of the specimens. A technique was also developed to evaluate lubricants based upon the surface deformation they would withstand. These techniques were used to measure the coefficient of friction and surface damage of various pure metals and alloys in both the lubricated and the unlubricated condition, at temperatures to 1800 F and pressures to 200,000 psi. It was found that this test uniquely yielded the friction coefficient of a given metal combination at a particular pressure and interface temperature. The variables found to be most significant in the pressure range 8000 to 200,000 psi are the roughness, temperature, surface oxide, and tool materials. Over this pressure range, friction is primarily determined by the strength of the metal. Adhesion effects modify the friction but primarily determine the extent of metal transfer.