Impact extrusion is a subset process of cold forging that is defined as a compressive metal deformation process conducted at room temperature. Deformation is achieved by applying a tremendous amount of force to a billet by use of a mechanical or hydraulic press. Once the compressive yield strength or flow stress is exceeded, the metal actually begins to “flow,” or plastically deform. The formation of dislocations in the crystal lattice is responsible for work hardening, a phenomenon unique to cold forming. This work hardening increases the hardness and tensile strength of the formed material vs. the raw material. Many times the work hardening alone increases the mechanical properties of the material enough that subsequent heat treating is not required.
Impact extrusion is used to form discreet parts with close tolerances, simple-to-complex shapes, net surfaces with excellent surface finish, and good mechanical properties. The most common forms of impact extrusion are forward extrusion, backward extrusion, radial extrusion, closed die impacting, and combinations of these.
Many materials can be impacted with good results. Aluminum and medium-to-low carbon steel are the most common metals used; with copper and magnesium impacted in less frequent applications. Titanium and stainless steel can be impacted under certain conditions, but deformation is more limited than what is achievable with the other alloys. KEYWORDS for this process: extruded shapes, extruders
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