A heated aluminum extrusion ingot is placed in an extrusion press and forced through a shaped opening - much the way toothpaste is forced out through the opening when you squeeze the tube. The aluminum takes on the shape of the steel die and an extrusion is formed. But the very special thing about the extrusion process is that die inserts can form a wide array of voids and openings inside the extrusion. A seamless tube, for example, is a single cavity hollow extrusion.
In this manner, one push of the ram, which supplies a force as high as 14,000 tons, can change an ingot of aluminum into an almost limitless variety of one-piece shapes with external and internal ribs, channel curves, flats, slots, grooves and oddly shaped openings.
The resulting part has excellent grain structure, uniform alloying element distribution and all the desirable characteristics inherent in wrought metal.
The ingots of aluminum are heated to between 800 and 1000°F. prior to extrusion and the dies are also heated.
The strength of extruded shapes in some alloys may be modified by a variety of heat treating processes to meet customer specifications.
Aluminum extrusions, like all forms of aluminum, can be bent, formed, machined, welded, brazed, soldered, adhesively joined, painted, etched and anodized.