A study of die failure mechanisms in aluminum extrusion

A very important factor contributing to the performance and economics (efficiency and quality) of any hot metal-forming process is the service life of tooling. Product rework and rejects can be traced back to various defects spread over the die life-cycle: die design, die manufacture, heat treatment and die service. Initiation and propagation of die damage can be caused by a number of mechanisms. Analysis of tool and die failure thus plays an important role in the prediction and prevention of die failure, and subsequently in improving process economics. This depends to a large extent on the knowledge of the manufacturing and service history of the failed tool and die. Such information is generally not very easily available, and especially not for a large number of die failures and a large spectrum of die profiles. Very few articles are available in literature that present failure analysis based on a substantial sample size of real die breakdowns. The three most commonly reported modes of die failure are fatigue-based fracture, wear, and plastic deformation/deflection. Shape complexity of the die profile plays an important role in hot extrusion of aluminum alloys. The paper presents results of an ongoing study about the relationship between die profile and modes of die failure. A total of 616 die failures involving 17 different die profiles were studied, in collaboration with a local industrial setup. All dies were made of H-13 steel, while the billet material was Al-6063 in all the cases. The analysis presented here reflects three different perspectives: (a) overall and class-wise break-up of failure modes, (b) failure analysis for dies of different complexities, and (c) shape-wise breakdown of each failure mode.