As the name suggests is done with hot materials i.e. the materials are heated to a temperature where they do not recrystallize while going through the die. Most of these are done on hydraulic presses.
In this process, a significant amount of pressure is also involved hence a proper and adequate amount of lubricant is also used.The choice of lubricant used depends upon the operational temperature of the materials used. For low temperature, graphite is used and for higher temperature glass is used.
It is done either at room temperature or near room temperature.The biggest advantage of this process is that there is absolutely no oxidation. Lead, Tin, Aluminium, zirconium, titanium, and steel are some of the metals that are extruded using cold extrusion process.
It finds its application in production of fire extinguisher cases, collapsible tubes, and shock absorber cylinders.
This type is done above room temperature and just below the recrystallization temperature of the material used, this process preserves the inherent qualities of the material that is used for extrusion. The end product retains its properties like malleability and ductility almost perfectly.