Preliminary examination of the fracture surfaces of a cold working die

Failure analysis investigates the causes of a product's destruction. Its final objective is to suggest measures that can be taken in order to prevent or minimize the chance of failure in the most economical way. This paper studies the failure of a rotary cold working die. The tool was manufactured from AISI D2 tool steel and it was intended for cutting paper at room temperature. The tool failed during the setup process on the machine it was designed for, thus failing to commence the manufacturing process. The process was initiated by a crack that began at the point of a diameter change of the tool body in the attachment part, where the tool was fastened to the rest of the machine. This paper presents the first results of the die failure study. Historical data were collected: operating conditions, lifetime, restitution of sound operation, collection of recorded history, measurement of operating temperatures and hardness control. This was followed by optical inspection, selection and preparation of samples and macroscopic analysis of fracture surfaces. The paper presents conclusions on the fracture mechanism and form and suggests the first probable causes leading to die failure. The results could be useful for industry as regards the avoidance of such failures in the production process.