A study on center thinning in the rotary forging of a circular plate

The rotary forging process has the potential for producing high-precision parts because of smaller forging forces and incrementally controlled deformation, especially in the cold forging of intricate parts to net shape. However, whilst thin circular plate can be made by rotary forging, center thinning and fracture will occur under given conditions, this problem having seriously influenced the quality of the products and the more widespread of this technique. This paper intends to explain the phenomenon of center thinning and gives a criterion of it. In order to confirm the validity of the proposed criterion, experiments have been carried out using a rotary forging press that has been designed and constructed in the authors' laboratory.