Extrusion & Die R&D (RD)

Tommaso Pinter, Almax Mori, Italy

In direct aluminum extrusion, the die is subject to severe operational conditions. The die discard is due to the plastic deformations accumulated after multiple cycles and to sever abrasion of the bearings region due to high extrusion rates. Hardening processes and best practices can reduce wash-out, thus improving the tool's useful life. However, when abrasion of the bearings channel is excessive, it is impossible to produce a profile within tolerance and with an acceptable surface quality; at that point, the adoption of a new die becomes mandatory. In this context, with a view to die reuse instead of discard, repair techniques can represent a valid alternative for reducing tooling costs. This paper describes a case study in which an end-of-life die was repaired using additive manufacturing techniques and reused to produce the same hollow section. The benefits in terms of reduced die cost per ton of extruded aluminum are described.

Roni Rountree, Charles Yurgel and Wojciech Misiolek, Lehigh University; Hannah Mason and Paul Rottmann, University of Kentucky; Randall Bowers and Nicholas Nanninga, Secat, Inc.; Dallas Sousek, Gordon Aluminum Industries, Inc., USA

Seam welds in direct, porthole die extrusion present an unavoidable challenge to extruders in the production of hollow profiles. Seam welds form through solid-state bonding, which can exhibit properties comparable to the bulk material. Pressure, temperature, and time under pressure within the weld chamber of the extrusion die strongly influence the integrity of the seam weld. However, optimizing these variables while maintaining other extrusion quality requirements remains complex. This work introduces a thermomechanical seam-weld simulation method in which two cylindrical blanks are compressed together under extrusion-relevant conditions. Flow stress data from such tests are then implemented into a finite element model to predict state variables in full-scale extrusion. In parallel, micro-tensile tests are then machined from the compressed blanks to evaluate the acceptance/rejection of the process conditions for sound weld formation. Microstructural and mechanical property comparisons with extrusion trials are performed to validate and assess the proposed simulation method.

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