Extrusion Surface Effects Resulting from Billet Surface Inflow
William Dixon, QED Extrusion Developments Inc., San Diego, USA
Track: EXTRUSION/DIE, PRACTICAL
ABSTRACT --- Surface finish effects such as pick-up, associated die lines, and
roughness have long been related to billet quality and have been extensively
researched, notably regarding the influence of impurity content, and how the
homogenization process affects the favorable Iron- (Fe) phase transformation.
This work extends from the established knowledge base, and addresses the role of
inflow of the billet surface Inverse Segregation Zone (ISZ), and its effect on
surface finish of 6061 alloy extrusions. The effect of the inverse segregation layer
depth in the billet is investigated. The effect of die design and edge distance from
die entry to the container liner is also investigated. Deeper ISZ and shallower
edge distance produced extrusions with inferior surface quality. Measures to
improve surface condition based on the findings of the work are presented. Other
extrusion process related factors are discussed.
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