Improvement of forging die life by failure mechanism analysis**

Abstract This study analyses the causes of rapid failure at the early stages of hot forging tools. Tool life generally refers to the number of forgings that meet the required geometry, properties and quality produced by a tool. Die failure in hot forging processes are caused by failure modes such as plastic deformation, wear and thermomechanical fatigue. This study focuses on plastic deformation failure. The practical experience was carried out in the upset forge fastener head, having a workpiece material of Ck45 alloy steel and tool made of 56 NiCrMoV7 tool material, which was forged at 950–1150°C, under an 800-ton, horizontal mechanical press. The finite element (FE) software MSC Simufact Forming 16.0 was used to simulate the process. The results showed plastic deformation occurring in the upper and lower dies because the temperature increase progressively reduced the hardness, creating softening effects during the forging process. The optimal forging temperature to form the fastener head was determined to be lower at 1000°C, saving time and cost. The FE method can be efficiently used to enhance the formation and to predict diet life.