Failure analysis of the die in the third hot forging stage of a gear blank

The failure by excessive plastic deformation of the high relief ring in the bottom die during the third stage of a gear blank forging was analyzed using a finite element method. An evaluation of the effective stress and temperature evolution at critical points of the high relief ring was completed. It was established that the plastic deformation was caused by excessive stresses applied on the high relief ring, which were associated with an additional upset that was employed in order to compensate for a lack of die filling under normal upsetting conditions. A solution to the problem involves a better cooling of the high relief ring during forging and die geometry changes that would allow the elimination of the additional upset.