Prediction of Surface Crack in Hot Forging by Numerical Simulation

This paper focuses on a technique for predicting surface cracks in hot free forging. These surface cracks occur at the side on which strains concentrate when a round bar is compressed by hot free forging. A final product has hardly any surface cracks because they are removed by gas scarfing. These conventional manufacturing processes have an industrial problem of low productivity with a waste of time. The suppression of the surface cracks is required. The mechanism and criteria for the surface cracks are not clear. In this paper, the mechanism of surface cracking was estimated, compared with the actual forging process. The mechanical property was evaluated by a high temperature tensile test. Various numerical simulations which changed the damage parameter (C value) were carried out. The critical value (C1) is calculated by shape comparison between the tensile test and the numerical simulation. It is possible to predict the surface cracking in the hot forging process by using this parameter.