ABSTRACT
Extrusion is a very versatile process, which transforms cast billets in one ram stroke into long uniform shapes with easily ‰nished surfaces. This is notably so for aluminum alloys where heat-resistant steel dies give good durability even for sections with several cavities and irregular projections. Extrusions are dimensionally accurate over long lengths, and any loss of straightness during cooling can be restored by cold stretching [1-7]. More than half the volume of extrusions is in aluminum and these constitute about 25% of aluminum mill products. The process is very §exible since many shapes can be produced by changing only the die and many Al alloys can be shaped in the same die. For long shapes the process has higher capital costs linked to higher productivity than longitudinal welding of several rolled shapes or plate brake forming; on the other hand, roll forming of sheet has higher capital costs and also productivity. Extrusion affords the production of shapes more complex than can be achieved by any other high-volume process.
