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Aluminum Extrusion Process and Technical Control Points (Part 1)

May. 04, 2020

Three temperature

In order to obtain higher mechanical properties, higher extrusion temperature should be selected. However, for the 6063 Alloy, when the Extrusion temperature is generally higher than 540℃, the mechanical properties of the aluminum extrusion profile alloy shell will no longer increase. When the Extrusion temperature is lower than 480℃, the tensile strength is in danger of unqualified.

If the extrusion temperature is too high, the product will appear bubbles, cracks, and serious scratches on the surface caused by aluminum sticking to the mold, and even defects such as burrs will appear. Therefore, in order to obtain high surface quality products, a lower extrusion temperature is often used.

In order to improve the production efficiency of aluminum extrusion, good equipment is also the key, especially aluminum extruder, aluminum rod heating furnace, mold heating furnace these three large parts, and the most important thing is to have a good extrusion plant and extrusion workers.

Aluminum Extrusion Profile Alloy Shell

Aluminum Extrusion Profile Alloy Shell

Thermal analysis

The bar and bar are heated prior to extrusion to a Solvus temperature so that the magnesium and the bar can melt and flow evenly through the material. When the bar is put into the extruder, the temperature does not change much.

When the extrusion machine starts, the immense extrusion rod pushing force to soften the Aluminum materials by die extrusion, produces a lot of friction, the friction force is converted into temperature, the extrusion of extruded aluminum temperature more than fuse, so magnesium melt to flow around, unstable.

The temperature must not be higher than the Solidus temperature, otherwise, the aluminum will melt and the profiles will not be formed. The temperature of the aluminum bar should be between 400-540°C (take 6xxx series aluminum alloy as an example), preferably 470-500°C.

Too high will cause tearing, too low will reduce the extrusion speed (because aluminum material must be softened). Most of the extrusion friction will be converted into heat, resulting in a rise in temperature, which is proportional to the extrusion speed and extrusion pressure.

This is often said that the three temperature: aluminum bar temperature, mold temperature, extrusion barrel temperature, another is the extrusion speed must be controlled.

The outlet temperature should be between 550-575°C, or at least above 500-530°C, otherwise, the magnesium in the aluminum alloy will not melt and affect the metal properties. But must not be higher than the solid phase line, too high outlet temperature will lead to tearing phenomenon, and affect the surface quality of the profile.

The optimal extrusion temperature the aluminum bar temperature shall be adjusted in combination with the extrusion speed so that the extrusion temperature difference is not lower than Solvus temperature, nor higher than Solidus temperature, i.e., 620°C. Different alloys have different melting line temperatures. For example, the melting line temperature of 6063 alloy is 498°C, while the melting line temperature of 6005 alloy is 510°C.

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