Take extruded aluminum tube for example. This comes in two forms: structural and seamless. Structural extruded tube is made by the porthole process, and for that reason is sometimes referred to as “porthole.” Seamless is made by the seamless extrusion process.
In the aluminum industry, the porthole extrusion process is the standard method for the production of extruded tubes and profiles. The process is limited to a number of aluminum alloys. However, most of the commercially available medium strength aluminum alloys such as EN AW-6060 or EN AW-6082 can be extruded by porthole extrusion.
Porthole extruded tubes often represent a compromise in terms of production cost relative to the final requirements. For small dimensions there is often the possibility to use a multi-strand tool enabling the extrusion of several extrusions at the same time. In addition, processing differences in porthole extrusion compared to seamless extrusion present additional cost benefit advantages. With specially designed extrusion tools, tubes with larger outer diameters or tubes at a greater ratio of outside diameter to wall thickness may be manufactured solely by extrusion.
As with seamless extruded tubes, smaller outside diameters or thinner wall thickness can be produced by subsequent cold drawing to achieve the final dimensions and tolerances. The following tables are a guide to the dimensions we offer: