Effect of deformation and heat treatment on fabrication of large sized ring by mandrel forging of hollow ingot

Abstract

Mandrel forging is a relatively simple process but needs multiple forging steps. A pierced blank is used as a preform for the conventional ring forging process and manufactured from solid ingot by several open die forging steps, such as cogging, upsetting and piercing. Since conventional ring forging process is a very complicated manufacturing process, it is not so efficient and cost‐effective process. In this study, ring forging process is developed using a hollow ingot as a preform. When a hollow ingot is used, open die forging steps to manufacture a pierced blank are not necessary. Hollow ingot has been directly forged into the ring by mandrel forging. Design variables for the new process are mainly related to characteristics of final forged ring product such as ingot size, forging amount and rotation speed. However, these variables are significantly affected by one parameter, that is, deformation amount by which the deformation energy, microstructure and mechanical properties of forged ring are determined. Therefore, mechanical properties with respect to the deformation amount are investigated by hot forging test of a staircase model. Process parameters of cast ingot and mandrel forging are studied on the condition that deformation amount of forged shell at each position can be reached to some values.