Forming process study and defect analysis of precision forging for the gear shafts of oil pumps

A special die of precision forging was designed for gear shafts. Metal forming and flow in the forging process were studied by finite element method and forging trials. The cause of tooth filling defects in the precision forging was analyzed:filling of the tooth corner is one of the key influence factor of a sharp rise of forming load. The forging die cannot bear the high load of fully corner filling due to its special structure. Based on the analysis of corner filling,chamfered relief and annulus relief were proposed for the precision forging. Finite element method was used for simulating the two relief processes and the conventional precision forging of gear shafts. It is shown that the two relief processes can both reduce the resistance of metal flow into the tooth corner,ensure well filling of the tooth corner and low forming load. Moreover,chamfered relief is better than annulus relief in the precision forging. Forging trials proved the validity of finite element simulation.