The void close behavior of large ingots during hot forging

Abstract

All the parameters that may affect void closure behavior are judged using finite element method (FEM). The simulation results show that temperature, strain rate, friction coefficient, sample size and void size do not affect the void closure behavior. Height-diameter ratio of the sample and void position will affect the strain around the void and the void will be easier to close when the strain around it are higher. Of all the parameters, void shape is the most important one. Height-diameter ratio of the void is defined to describe the effect of void shape. The simulation results show that the larger height-diameter ratio of the void, the harder it is for the void to close. Based on these results and the sectioning results of a 100 t ingot, a new forging method, wide-anvil radial forging (WRF) is proposed. WRF method can concentrate the strain on the center of the ingot; meet the optimum height-diameter ratio condition of the void closure and heal shrinkage cavities effectively. Experiments on continuous casting billets prove the effectiveness and applicability of this method.