Aluminum extrusions are an essential part of our homes, although many people do not even notice them. They are usually part of window or door systems, but the application does not stop there. Aluminum bars have countless applications in building and manufacturing industries, therefore the quality of each product must be impeccable.

Extrusion is a modern process in which aluminum billets are heated and pushed through a shaped die opening. The opening can be modified to create different shapes and sizes to fulfill a user’s specific needs.

Depending on the required aluminum bar type, we use different steel dies.
For solid bars or profiles
flat dies
pre-chamber dies
For hollow bars or profiles
chamber dies

The 6 Steps of Aluminum Extrusion
The extrusion process is carried out in direct or indirect extrusion presses with different power levels (at Impol, those are between 12.5 and 55-MN). The basic process can be broken down into six distinct steps, although they can be modified or expanded upon depending on the customer’s specific requirements.

But even before the extrusion process begins, the cast aluminum rods needs to be cut into smaller pieces. These short pieces are called billets. The pre-cut billets ensure that the length of each extruded bar will be roughly the same and there will be no material wastage.

Step 1: Preheating the aluminum billet and steel die to a specified temperature
The billets are heated in induction or gas furnaces from room temperature to the extrusion The temperature varies depending on the alloy and the final temper.
The heated billets need to be malleable enough to take on the required shape, but still firm enough to retain their shape during transportation.
The push bat starts applying pressure into the heated billet and pushes it towards the die opening.
Step 2: Loading the billet into the steel extrusion press container
To prevent heat loss, the billets are quickly transported from the furnace into the press. They are loaded into the recipient and are ready to be extruded.
The ram starts applying pressure into the heated billet and pushes it towards the die opening.
Step 3: Extrusion
The heated aluminum billet is pushed through the openings in the tool. Those openings can be modified to create different shapes and sizes. The process is similar to a cookie press, where the different shaped discs create different cookie designs.
When the bars exit the press, they are already extruded to their required shape.
Step 4: Controlled cooling
The extrusion process is followed by quick cooling of the extruded bars/tubes/profile
When exiting the press, the fully formed bars/profiles are pushed through a water bath which guarantees uniform quenching of the heated aluminum.
The quenching process is necessary to ensure the required mechanical properties and adequate material microstructure.
To prevent any material deformation, the cooling process must be carried out without delays immediately after the extrusion process.
Step 5: Stretching
Immediately after quenching, the extruded bars are cut into the prescribed interphase length.
The cut bars are then grabbed by a puller, which lays them over the runout table. This allows them to further cool down.
In this phase, the extruded bars are run through a strengthening process, which stretches the bars and ensures their mechanical properties by removing the internal tension within the bars.
Step 6: Cutting and final packaging
The quenched and straightened bars are cut to the length specified by the customer.
At this stage, the aluminum bars have the properties of the T1/T4 temper. To ensure better mechanical properties of the T5/T6/T66 temper, the bars are artificially aged.
The aging process further strengthens the extruded profiles and ensures they fulfill the mechanical properties specified for individual alloys.