This document discusses different types of extrusion processes including hot, cold, and warm extrusion. Hot extrusion is done above the material's recrystallization temperature to reduce work hardening and require less force. It is commonly used for metals like magnesium, aluminum, copper, steel, titanium, and nickel. Cold extrusion is done at or near room temperature and offers advantages like no oxidation, higher strength, and better tolerances. Materials often cold extruded include lead, tin, aluminum, and steel. Warm extrusion is between room temperature and the recrystallization point to balance required forces and properties.

1. COLD AND HOT EXTRUSION

2. HOT EXTRUSION

3.  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). Pressures range from 30 to
700 MPa (4,400 to 101,500 psi), therefore
lubrication is required, which can be oil or graphite
for lower temperature extrusions, or glass powder
for higher temperature extrusions. The biggest
disadvantage of this process is its cost for
machinery and its upkeep.

4. HOT EXTRUSION TEMPERATURE FOR VARIOUS
METALS
Hot extrusion temperature for various metals
Material Temperature [°C (°F)]
 Magnesium 350–450 (650–850)
 Aluminium 350–500 (650–900)
 Copper 600–1100 (1200–2000)
 Steel 1200–1300 (2200–2400)
 Titanium 700–1200 (1300–2100)
 Nickel 1000–1200 (1900–2200)
 Refractory alloys up to 2000 (4000)

 The extrusion process is generally economical when producing between
several kilograms (pounds) and many tons, depending on the material
being extruded. There is a crossover point where roll forming becomes
more economical. For instance, some steels become more economical
to roll if producing more than 20,000 kg (50,000 lb).

5. ADVANTAGES
 For metals and alloys that do not have sufficient
ductility at room temperature
 Reduces forces
 Increases die wear
 Preheated billet will develop an abrasive oxide
film that affects the material flow pattern, unless
it is heated in an inert-atmosphere furnace
 Die materials often steels, sometimes coated
with zirconia to extend life.
 Glass is often used as a lubricant

6. COLD EXTRUSION

7.  Cold extrusion is done at room temperature or
near room temperature. The advantages of this
over hot extrusion are the lack of oxidation, higher
strength due to cold working, closer tolerances,
good surface finish, and fast extrusion speeds if
the material is subject to hot shortness.[1]
 Materials that are commonly cold extruded
include: lead, tin, aluminum, copper, zirconium,
titanium, molybdenum, beryllium, vanadium,
niobium, and steel.
 Examples of products produced by this process
are: collapsible tubes, fire extinguisher cases,
shock absorber cylinders and gear blanks.

8. ADVANTAGES
 No oxidation takes place.
 Good mechanical properties due to severe
cold working as long as the temperatures
created are below the re- crystallization
temperature.
 Good surface finish with the use of proper
lubricants.
 Superior dimension control
 Improved strength properties

9. DISADVANTAGES
 Higher forces required for deformation
 Heavier and more powerful equipment required
 Less ductility available
 Metal surfaces must be clean and scale-free
 Strain hardening occurs (may require
intermediate anneals)
 Imparted directional properties may be
detrimental
 May produce undesirable residual stresses

10. WARM EXTRUSION
 Warm extrusion is done above room
temperature, but below the recrystallization
temperature of the material the temperatures
ranges from 800 to 1800 °F (424 to 975 °C).
It is usually used to achieve the proper
balance of required forces, ductility and final
extrusion properties.