Precision Aluminum Extrusion

The production process of aluminum extrusions involves forcing heated aluminum alloy material through a die with a specific cross-sectional profile. Aluminum extrusions are widely used in construction, machinery, home appliances and other fields.

Aluminum extrusions are available in different shapes of profiles:

Solid (i.e. bars, beams)

Hollow (i.e. rectangular tubes)

Semi-hollow (i.e. various channels, heat sinks)

The aluminum extrusion process begins with product design. The product design, based on its intended use, determines the production parameters. Issues related to function, machinability, finishing and service environment will influence the choice of alloy. The function of the profile will dictate the design of its shape and thus the design of the forming die.

Extrusion process

During the extrusion process, the billet remains solid, but has been softened in the furnace. The extrusion operation typically heats the billet to a temperature of over 700°F (375°C). The actual extrusion process begins when the punch begins to apply pressure (from 100 to 15,000 tons of pressure) to the billet anywhere in the vessel. The pressure of the press determines how large an extrusion it can produce.

The completed extrusion is cut off at the die and the remaining metal is removed for recycling. Depending on the billet size and die opening, each stroke of the press can produce up to 200 feet of continuous extrusion. The newly formed extrusion is supported by the output conveyor as it leaves the press and begins to cool naturally or by quenching using air or water. This is a critical step to ensure adequate metallurgical properties after aging. The extrusions are then transferred to the cooling table. After the profile has been quenched (cooled), a "stretching machine" can be used to straighten the extrusion and correct any distortion that may have occurred during the extrusion process.

Heat Treatment

After aluminum profiles are cut to specified commercial lengths, they are typically heat treated in an oven to achieve a T5 or T6 condition. Aluminum profiles achieve optimum strength through an aging or heat treatment process. Heat treated alloys are further strengthened or hardened by a controlled heat treatment that affects the metallographic structure of the alloy. The heat treatment process ensures that fine particles are uniformly deposited in the metal, resulting in maximum strength, hardness and flexibility for the particular extruded alloy.

Finishing

After heat treatment, extrusions can be fabricated (cut, machined, bent, welded, etc.) or finished (anodized or painted). Although aluminum alloys are more resistant to corrosion than ordinary steel, depending on the aluminum alloy used, some corrosion may occur after a period of time. To enhance the corrosion resistance of aluminum, anodizing is often used as a surface treatment. Its thick oxide layer helps improve corrosion resistance and also makes it more wear resistant. Powder coatings can also be applied to aluminum extrusions, which provide a thicker protective layer on the surface and offer more options for various colors.