Aluminum Extrusion Process
The aluminum extrusions process shapes aluminum by heating it and forcing it with a hydraulic ram through a shaped opening in a die. Extruded material emerges as a long piece with the same profile as the die opening. Once extruded, the hot aluminum profile must be quenched, cooled, straightened and cut.
The extrusion process can be compared to squeezing toothpaste from a tube. The continuous stream of toothpaste takes the shape of the round tip, just as an aluminum extrusion takes the shape of the die. By changing the tip or die, different extrusion profiles can be formed. If you were to flatten the opening of the toothpaste tube, a flat ribbon of toothpaste would emerge. With the aid of a powerful hydraulic press which can exert from 100 tons to 15,000 tons of pressure, aluminum can be extruded into just about any imaginable shape.
There are two methods of extrusion – direct and indirect – and the process generally follows these steps:
A die is cast from the cross-section of the shape you want to create.
Aluminum billets are heated in a furnace to approximately 750 to 925ºF, the point where aluminum becomes a soft solid.
Once at the desired temperature, smut or lubricant is applied to the billet and ram to keep the parts from sticking together, and the billet is transferred to a steel extrusion press container.
The ram applies pressure to the billet, pushing it through the container and through the die. The soft but solid metal is squeezed through the opening in the die and exits the press.
Another billet is loaded and welded to the previous one, and the process continues. Complex shapes may emerge from the extrusion press as slowly as one foot per minute. Simpler shapes can emerge as quickly as 200 feet per minute.
When the formed profile reaches the desired length, it is sheared off and transferred to a cooling table, where it is quickly cooled with air, water sprays, water baths or mists.
After the aluminum extrusion has cooled, it is moved to a stretcher where it is straightened and work-hardened to improve its hardness and strength and release internal stresses.
At this stage, extrusions are cut with a saw to the desired lengths.
Once cut, the extruded parts can be cooled at room temperature or moved into aging ovens, where heat treatment speeds up the aging process in a controlled temperature environment.
After adequate aging, extrusions profiles can be finished (painted or anodized), fabricated (cut, machined, bent, welded, assembled), or prepared for delivery as is to the customer. This aluminum extrusions process actually enhances the properties of the metal and results in a final product that is stronger and more resilient than before. It also creates a thin layer of aluminum oxide on the surface of the metal, which gives it a weather-resistant and an attractive natural finish that does not require any further treatment, unless a different finish is desired. The natural characteristics of aluminum allow it to be extruded into intricate, complex shapes, providing engineers and designers with limitless design possibilities.
Sapa Extrusions is the world’s leading producer of extruded aluminum profiles. We can satisfy the most challenging requirements from standard profiles to complex multi-part aluminum extrusions in standard and proprietary aluminum alloys with dimensional accuracy and superior surface quality. Our nationwide network of production and supply facilities enables us to produce all shapes, sizes, alloys and tempers. Sapa offers complete solutions for extruded aluminum products required by the automotive, mass transit, bridge decking, and solar/renewable energy industries, as well as green applications for the building & construction market.