This typically involves only metals. On the basis of temperatures extrusion can be cold or hot. The type of process is dependent on the ductility of the material involved. Cold Extrusion is suitable for Ductile materials whereas brittle materials require a hot extrusion process for change shape without the risk of breaking it.

• Cold Extrusion
  The process of Cold extrusion is generally done at room temperature or at temperatures that is slightly elevated. This process is applicable for most materials, provided the materials are able to withstand the stresses as a result of extrusion. Typically metals that are extruded by cold Extrusion method includes aluminum alloys, lead, tin, copper, titanium, steel etc. A typical Cold Extrusion process in three steps are described here: Profiles that can be cold extruded includes gear blanks, collapsible tubes, aluminum cans, cylinders etc. Following advantages are attributed to cold extrusion:
  • Absence of oxidation
  • Fairly good mechanical properties
  • Good surface finish
  • Absence of the requirement of billet heating
  • Excellent control of dimensional tolerances
  
  
  
• Hot Extrusion
  Hot extrusion process takes place at high temperatures. The temperature is generally kept at 50- 75% of the melting point of metal. The pressures In hot extrusion ranges from 35-700 MPa or 5076 - 101,525 psi. On thing is important in hot extrusion and that is good lubrication. This is because of high temperatures and pressures involved. A typical hot extrusion process is shown below: