Extrusion is the process of shaping a material, such as aluminum, by forcing it through a shaped opening in a die. It is used in the production of aluminum profiles, which allows for the creation of almost unlimited variations and shapes of profiles.
What is the composition of the extrusion process and how does it occur?
Stages of the aluminum extrusion process
First, it is necessary to develop the project documentation, which will include all the necessary parameters: dimensions, cross-section, shape, alloy strength, and so on.
The most important factor to keep in mind during the extrusion process is temperature. Temperature is the most critical factor, as it imparts the desired characteristics of aluminum, such as hardness and strength. The workpieces should be heated to approximately 420-500°C.
After the workpiece reaches the desired temperature, it is transferred to the loader, where a thin film of carbon material or lubricant is added to the workpiece and the traverse. The carbon concentrate acts as a separating agent (lubricant), preventing the two parts from sticking together.
The blank is translated into a groove, and from there it moves inside the press, where it is crushed against the die under pressure, becoming shorter and wider until it makes full contact with the walls of the container. As aluminum is pushed through the die, liquid nitrogen flows around certain sections of the die to cool it. This increases the lifespan of the matrix and creates an inert atmosphere that prevents the formation of oxides on the extruded shape. In some cases, gaseous nitrogen is used instead of liquid nitrogen. Gaseous nitrogen does not cool the matrix, but it creates an inert atmosphere.
As a result of the pressure applied to the workpiece, the metal begins to be forced through the die opening.
When the extrusion comes out of the press, a special tool installed on the press plate measures its temperature. The main goal of temperature knowledge is to maintain the maximum speed of the press. The target initial temperature for extrusion depends on the alloy. For example, the target output temperature for alloys 6063, 6463, 6063A, and 6101 is 498°C (minimum). The target exit temperature for alloys 6005A and 6061 is 510°C (minimum).
Extrusions are pushed out of the die onto the exit table, and a take-off directs the metal down the exit table during the extrusion process. During extraction, the extrusion is cooled by a series of fans along the entire length of the discharge and cooling table. (Note: Alloy 6061 is heat-treated with water as well as air.)
The metal is transferred (via a conveyor belt or movable beams) from the workbench to a special cooling table.
After the aluminum cools down and moves along the cooling table, it is transferred to stretchers. Stretching aligns the extrusions and performs work hardening (restructuring of molecules that gives aluminum increased hardness and strength).
The next step is carving out. After the extrusions have been stretched, they are transferred to a dust table and cut to the desired length.
After the details are cut out, they are loaded into a transport device and moved to the ovens for ageing. Heat treatment or artificial ageing strengthens the metal by accelerating ageing in a controlled temperature environment for a specified period.
If explained in simple terms, the extrusion process is similar to squeezing toothpaste out of a tube. Toothpaste is a heated cylindrical aluminum block, which is also called a blank, while the toothpaste tube is a die (form). The workpiece (preheated in an induction furnace to 450-500 degrees Celsius) is pushed through a tool/die, during which the profile takes on the desired shape. When the profile leaves the tool, it is cooled with water or air, after which the profiles are stretched while they are still soft. This eliminates any buildup of stress in the aluminum, while simultaneously achieving the desired and correct dimensions of the profile. After that, the profiles are cut, and then they achieve their final strength through thermal and/or cold hardening.
As in any production, certain rules and nuances of the process should be considered when preparing for profile extrusion. Therefore, it is important to obtain professional and qualified advice from the very beginning. Drawing on 20 years of industry expertise, the specialists at Alupro are ready to offer you our knowledge and experience, so that ultimately you can achieve the best solution for yourself.
