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Aluminium Extrusion

The products obtained by aluminium extrusion account for more than 50% of aluminium products in the European market. Extruded aluminium is used principally in architecture; windows and doors, structures, curtain walls, lattice, etc. However, it also has applications in a great variety of industries; furniture, heat sinks, airframes, car and train frames.
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The extrusion consists in shaping a cylindrical aluminium ingot, known as “Billet”, by pulling it through an opening specially arranged, called “die”. This opening corresponds with the profile cross section that we want to obtain. The most common method is direct extrusion, where the press push the billet through the die.

Basic Elements.

Aluminium: Aluminium is extracted from Bauxite, mineral from we obtain Alumina with the Bayer process. In a second phase we get Aluminium by electrolysis. To improve the material properties alloys are used, usually series 6000 Aluminium-Magnesium-Silicon, which are heat treated.

Press: They are hydraulic machines that provide between 1.000 and 3.000 tons of pressure, they are composed of a container, a die holder and a ram.

Die: They are made of high temperature resistant steel. The openings are made by electrical discharges (EDM) by computer-controlled machines. For cleaning they undergo a nitriding process, that in addition it gives them surface hardness.

Pressure: The pressure is a factor that depends on multiple variables; the raw material, the profile, the press and the temperature, being the most determining factor the relation between the diameter of the log and the profile surface.

 

Extrusion process

Once the log is heated, a portion is cut and the material is introduced at 500º in the press, this is the temperature needed for aluminium to reach a plastic condition. The die is also preheated so there is no temperature difference with the material.

Once the aluminium starts flowing through the die, the tip is removed and the profile is supported by a carriage on the bench till it reaches a length of approximately 50m. Meanwhile, it is quickly cooled by air or water, at a 50º per minute speed.

Usually the profiles show slight bends and tensions that are corrected by the stretching. Afterwards, the profiles are cut into the specific lengths.

The extrusion process will continue with the thermal treatments, heat-treating and/or artificial aging. These processes consist in the heating and quenching (in special ovens) in a controlled temperature environment for a set amount of time.

 

 

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