Aluminum Alloy Extrusions
Aluminium Extrusion is the process by which long straight and shaped parts can be produced. The cross-sections that can be produced vary from solid round, rectangular, to L shapes, T shapes. Tubes and many other different types. Extrusion is done by squeezing metal in a closed cavity through a tool, known as a die using either a mechanical or hydraulic press.
Extrusion produces shear as well as compressive forces in the stock. No tensile is produced, this makes high deformation of the Aluminum extrusion possible without tearing the metal. The cavity in which the raw material is contained is lined with a wear resistant material. This can withstand the high radial loads that are created when the material is pushed thru the die. Extrusions, often minimize the need for secondary machining, but are not of the same dimensional accuracy or surface finish as CNC machined parts.
Cold Aluminum Extrusion: Cold extrusion is the process done at room temperature or slightly higher temperatures. This process can be used with Aluminum and zinc alloy and subject to designing a extrusion die that can withstand the stresses created by extrusion. Parts that are cold extruded are collapsible tubes, Aluminum cans, cylinders, gear blanks. The main advantages of cold extrusion are:
- Material does not oxidize
- Extrusions maintain excellent mechanical properties as long as the temperatures during the extrusion are below the re-crystallization threshold
- Attractive surface finish when proper lubricants are applied during the process
Hot Aluminum Extrusion: Hot extrusion is done at high temperatures, approximately 50 to 75 % of the melting point of the alloy. The pressures can range from 35-700 MPa (5076 - 101,526 psi). Due to the high temperatures and pressures and its detrimental effect on the dieset life as well as other components, good lubrication is essential. Graphite applied at lower temperatures, at higher temperatures glass powder is used.
Parts produced by extrusions are hollow parts, commonly used in automotive and consumer appliances, window frame members, railings, aircraft structural parts.
[ Author: admin] [ Date: 2016/4/25 ] [ Hits: ]