Improvement in Surface Quality of Ironing Product Using Differential Lubrication

Ironing is an effective process for precisely finishing a formed product at the final stage of a series of forming processes. Generally, a high-performance lubricant oil with high viscosity is used to prevent galling under severe forming conditions, but high-viscosity oil is difficult to remove from the workpiece after the forming process. Residual oil can interfere with subsequent processes such as welding, heat treatment, and painting. Therefore, low-viscosity oils with excellent cleanability are desirable under severe ironing conditions. In this study, differential lubrication was applied to ironing to enable the use of low-viscosity lubricant oil. The results showed that severe galling occurred on the inner surface of the workpiece when a low-viscosity oil was used. However, no galling was observed when low- and high-viscosity oils were applied to the inner and outer surfaces of the workpiece, respectively. These results indicate that differential lubrication enables the use of a low-viscosity lubricant oil without galling while maintaining high surface quality.