In designing the multi-stage cold forging process, an important factor along with formability is the die life cycle. As the die life cycle is closely related to the integrity of the phosphate film coating on the surface of the material, this study presents a method for predicting the die life cycle considering damage to the phosphate film coating. First, the correlation between the phosphate treatment conditions (phosphate treatment solution concentration and temperature) and the film layer weight was discussed. Afterwards, the behavior of the friction coefficient according to the damage of the phosphate film was predicted through repeated frictional tests. The behavior of the coefficient of friction was mainly divided into three areas and correlated with the film weight. By applying these results to the automobile engine bolt forging process, a method for performing precise simulation considering the damage to the phosphate film was presented. In addition, a method for predicting the quantitative limit life of the die based on precise simulation results with high accuracy was presented.
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