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Experimental Study of Longitudinal Weld-Seam Properties

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Experimental Study of Longitudinal Weld-Seam Properties in Tubular AA6060 and AA6082 Extrusions

Andrew J. den Bakker, Nedal Aluminium B.V., Utrecht, The Netherlands
Wim H. Sillekens, TNO Science & Industry, Eindhoven, The Netherlands
Robert J. Werkhoven, TNO Science & Industry, Eindhoven, The Netherlands

Track: EXTRUSION/DIE, PRACTICAL - Hollow Profiles and Heat Exchanger Profiles

ABSTRACT --- Longitudinal weld seams in hollow aluminum extrusions
produced by means of porthole dies are formed when metal streams flowing
around the mandrel in the die are re-joined through a process of solid-state
bonding. As longitudinal weld seams occur along the entire length of the
extrusion these cannot be eliminated from the extrusion. Therefore, for structural
extruded products, the mechanical integrity of weld seams is of paramount
importance. In this research, a literature study has shown that the combination of
process conditions and metal-flow characteristics control weld-seam quality as
this determines the major particulars of the solid-state bonding process; i.e., the
interfacial pressure, temperature, strain, and contact time in the plane of rejoining
metal streams. Tubular sections were produced in lab-scale extrusion
tests with AA6060 and AA6082 alloys, using porthole dies with a mandrel
supported by three bridges, yet with different internal geometries. The extrusions
were tested with the aim of relating the investigated parameters to the
microstructural features and the mechanical integrity of the weld seams, with the
latter focused on the ductility characteristics. Results show that pronounced
differences in weld-seam quality exist between the alloys, but also in dependence
on the location along the length and between the particular die designs.

© Extrusion Technology for Aluminum Profiles Foundation (ET Foundation). All rights reserved. No part of The Proceedings may be reproduced in any form without the express written permission of the ET Foundation.