Lubricating Properties of Lubricants used in Fluorine-free Claying Method for Cold Forging of Aluminum Alloy

Abstract

A claying method for lubrication has been developed to reduce the environmental load when an aluminum workpiece is lubricated for cold forging. In this study, the claying method and the clayed lubricant are investigated. Claying produces a layered double hydroxide on the aluminum workpiece. It normally takes about 120 minutes to produce the clay film on the aluminum workpiece. A prior alkaline treatment of short duration before lubrication enables the claying reduction in claying time, so that the time to produce the clay film takes 2en10 min in the claying method. The clay lubricant resulted in less friction. Using the clay-lubricated workpiece, the ring compression test showed a Coulomb’s frictional coefficient m of 0.061, which is lower than m = 0.13 when using the conventional lubricant of aluminum-fluoride and zinc. Moreover, using another claylubricated workpiece, punch loads were reduced in 70-shot continuous backward-cup extrusion tests. Extrusion conditions included the cup depth/punch diameter ratio of 5.26, and an 81% reduction in cross-sectional area. All extruded cups showed a smooth inner surface without galling. It was found that the claying method is effective for lubricating aluminum for cold forging.