Extrusion Process is used for manufacturing long and straight metal parts. The shape of the Cross-sections can be solid round, rectangular, to T shapes, L shapes and Tubes etc. Extrusion is done by squeezing the metal in a die by using a mechanical or hydraulic press.
 
Extrusions are capable of producing compressive and shear forces in the stock material. As tensile is not produced, this makes very high deformity a possibility without actually tearing the metal. A wear resistant material lines the cavity in which the raw, material is constrained. This helps to resist the high radial loads as the material is pushed into the die.
 
Features of Extrusion Process:

Cost Effective: Minimizes the need for secondary machining process.

Surface Finish :  For Steel is 3 µm;(125 µ in ) , for Aluminum and Magnesium-0.8 µm(30 µ in)

Cross-Section  :Wide Variety of Cross-sections can be made

Minimum Thickness : For  Steel 3 mm (0.120 in), for Aluminium and Magnesium 1 mm (0.040 in)

Minimum Cross Section: For Steel 250 mm (0.4 in ) for steel

Corner and Fillet Radii : 0.4 mm (0.015 in ) for Aluminium and Magnesium, for steel the minimum corner radius is 0.8 mm (0.030 in) and 4mm (0.120 in) Fillet radius.
 
Application of Extrusion Process:
 
Trim Parts as used in automobile and construction equipment, Railings, window frame members, structural parts etc.
 
Extrusion can be of two types:

Hot Extrusion:

Generally done at fairly high temperature, approximately at 50 to 75 % of the melting point of the metal. The Pressures range from 35-700 MP a (5076-101,525 psi). To Cool down the high temperatures and pressures and its adverse effect on the die life as well as other components, good lubrication is a must. Oil graphite and glass powder is preferred as lubricants.