Evaluation of Cold Forging Lubricants for Steel by Ring Compression Test with Rotating Die

Abstract

In cold forging processes, friction between a material and dies strongly influences the material flow, forging load, and damage to the dies. Therefore, several methods of evaluating friction have been proposed. However those methods are not well simulated for the severe conditions occurring in actual forging processes. In this study, a new method of evaluating friction coefficients is proposed. The method applies a developed die set with a rotating die in the ring compression test. The unique feature of the die set is a die rotating at a very slow angular velocity which makes it possible to measure both load and torque. By a combination of measured load and torque, friction coefficients can be monitored throughout the measurement process. Friction coefficients were measured for four types of lubrication: mineral oil, cold forging oil, dry-in-place, and bonderizing lubricants. These results confirm that the proposed method enables us to measure friction coefficients under cold forging conditions.