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Hot extrusion is a hot working process, which means it is done above the material's recrystallization temperature to keep the material from work hardening and to make it easier to push the material through the die. Most hot extrusions are done on horizontal hydraulic presses that range from 230 to 11,000 metric tons (250 to 12,130 short tons ...
During an extrusion process it is essential to consider the surface finish of exposed product surfaces. As a general rule, the narrower an exposed surface, the more uniform its finish becomes. Webs, flanges and abrupt changes in metal thickness may show up as marks on the opposite surface of an extrusion, particularly on thin sections. The ...
In steel extrusions, the depth of an indentation should be no greater than its width at its narrowest point. This is necessary to provide sufficient strength in the tongue portion of the extruding die. In copper alloys, magnesium, and aluminum, the depth of an indentation may be greater since extrusion pressures are lower.
Friction extrusion is a thermo-mechanical process that can be used to form fully consolidated wire, rods, tubes, or other non-circular metal shapes directly from a variety of precursor charges including metal powder, flake, machining waste (chips or swarf) or solid billet.
This process is the same as a regular extrusion process up until the die. There are three main types of dies used in this process: annular (or crosshead), spider, and spiral. Annular dies are the simplest, and rely on the polymer melt channeling around the entire cross section of the die before exiting the die; this can result in uneven flow.
Also referred to as dissimilar-metal corrosion, this process can occur as exfoliation or as intergranular corrosion. Aluminium alloys can be improperly heat treated, causing internal element separation which corrodes the metal from the inside out. [citation needed] Aluminium alloy compositions are registered with The Aluminum Association.
Extrusion welding is an attractive process for applications that take advantage of its ability to weld thick sections quickly. For some applications, especially where there are large geometry parts where more traditional plastic welding methods (such as hot plate welding) is not possible, extrusion welding is the only feasible and cost effect option.
The Hall–Héroult process is the major industrial process for smelting aluminium. It involves dissolving aluminium oxide (alumina) (obtained most often from bauxite , aluminium 's chief ore, through the Bayer process ) in molten cryolite and electrolyzing the molten salt bath, typically in a purpose-built cell.