Metal Extrusion Process and their application

The Metal extrusion process is an effective method for produce tube, hollow shape, shaft and more in fixed cross section. The metal billet is Placed on chamber (cylinder) often pushed (or) force applied through ram and draws the metal from die. Die are machined with require cross section. That creates long objects of fixed cross section. Some difficult cross section may be manufactured by this method. extrusion applications such as providing bar, tube, shaft and etc.

Advantage of extrusion:

  • Extruded object having very dense grain structure and good mechanical properties.
  • Thin cross sectional part can be manufactured.
  • Good surface finish product.
  • Complicated cross sectional part easily extruded.
  • Good dimensional accuracy
  • Mass production of seamless tube can be machined
  • Fast rate of production.

examples of extrusion Products

Cylindrical Shaft, hollow shaft, Rod and tube are manufactured by using that.

Type of extrusion:

The billet is forced with high pressure through die, that give require shape of object.

  1. Based on temperature
  • Hot extrusion
  • Cold extrusion

2. Based on method of operation

  • Direct (or) forward extrusion
  • Indirect (or) backward extrusion
  • Tube extrusion
  • Impact extrusion.

Hot extrusion:

It is a hot working metal process and used in modern industrial. The metal billet is heated until the extrusion temperature range (below table) and then placed on the chamber the pressure applied to the billet by using moving ram. The ram forces applied to the plastic material through a die and generate require shape. The ram pressure is approximately 68×107 N/m2.

Billet metal temperature for various metals

 S.NO Materials Temperature (⁰c)
1 Steel 1200 to 1300
2 Refractory alloy 975 to 2200
3 Copper alloy 650 to 1300
4 Magnesium 350 to 425
5 lead 200 to 250

Billet is heated through furnace. That billet are lubricated and then loaded on container. When the lubrication process normally, glasses are used or some time vegetable oils support with graphite used and the mechanical support of container presented in this process. It carried by hot metal billet and ram force. In order to possess resistance to wear and chamber fitted with inner made up of tungsten steel.

Following material extrusion and alloyed:

  • Aluminum
  • Copper
  • Steels
  • Magnesium
  • Stainless steel

Direct Extrusion (or) forward extrusion:

The billet is placed on the chamber and is pressed by press. The front end of chamber closed by die. That dies having required shape of section. The ram is pushed the metal inside of chamber.

First, the metal billet is filled the chamber and flowed through die orifice. The metal is squeezed from the die gets the die orifice shape. The metal flow in same direction of ram movement.  When the metal is compressed. The metal contact with chamber cools and forms of oxide. And also the oxide include with metal. When the hot billet is contact with the surface chamber. During the process the high amount of friction provided between chambers and abrades the chamber surface. This is minimized of lubrication.

Direct Extrusion or forward extrusion diagram
Direct Extrusion or forward extrusion diagram

The defects of porous, voids and other are eliminated in the billet. The finished product having some of route has fewer defects presented because of compressed and moved through die orifice. The finished parts consist of elongated grain in direction of force application.

Some Important material extrusion:

Titanium alloy, copper alloy, magnesium alloy, carbon and alloy steel.

Direct (or) forward extrusion applications:

Tubular parts with multiple diameter holes (cylinder), conical, stepped or tapered diameter solid shaft and other non-round shape.

Indirect Extrusion (or) backward extrusion:

The indirect extrusion operation principle same as direct extrusion process. The hollow shape ram is used in this extrude method. The hollow ram is squeezed the metal. Ram contain the die with orifice of require shape of part. Now the ram act as die and end of cylinder is closed consist of as shown in figure.

Indirect Extrusion OR backward extrusion process
Indirect Extrusion OR backward extrusion process

The metal billet is filled in the cylinder and squeezed by the moving the hollow ram. Now the metal flowed through the die hole of hollow cylinder and gets the required shape.

Following material can be extrusion:

Titanium alloys, copper alloy, aluminum alloy, magnesium alloy, carbon and alloys

indirect or backward extrusion applications:

Cupped parts with hole as cylinder, hollow parts, conical or other shapes.

For direct extrusion, the metal billet move over the cylinder wall gets squeezing. For this movement of billet generate the friction. Due to this friction require more squeeze pressure for the direct extrusion compared to indirection extrusion.

The metal billet moment is very less in indirection. So that gives more tooling life. The metal oxidized from chamber is not easy included into formed metal like direct extrusion.

Comparison between direct and indirect extrusion:

            Direct extrusion

Indirect extrusion

  • More fore required in extrusion process
  • Less fore required
  • Not complicated equipment used
  • Complicated equipment used, because of hollow ram
  • More friction
  • Less friction
  • Tools life is less
  • More tool life
  • Finished part contain oxides of metal
  • Not contain oxides of metal

Tube extrusion:

The tube extrusion process, mandrel is attached to front of ram part. When the ram flowed the metal into the die hole. This operation produces by hollow tubes. That hollow tube having joint less called as seam less tubes. That seem less tube use as boiler tubes. It is most common method of hot extrusion of tube. Also it is forward extrusion method by using a mandrel to form bore of tube. First the mandrel is pushed through center of billet and dies flowed by applying pressure (advanced plunger used). The metal billet is forced to flow through opening between die and mandrel. It is a quite rapidly operation. Most of metals and alloy are hot extrusion. Sometime production of seam less tube by using cold extrusion.

tube extrusion process diagram

The feedstock are forced through die for different method are auger, which is single or twin screw, powered by electric motor, by used a ram driven by hydraulic pressure (for titanium alloy, steel alloy), oil pressure (for aluminum).

Material used in tube extrusion:

The most extrude applications of materials used. they are Polymers, ceramics and food stuffs and etc.

hydrostatic extrusion or hydraulic extruder:

The hydraulic fluid is surrounding the billet, which is pressurized by ram and to provide extrusion force. The fluids are placed between chamber and billet. So there eliminate contact between them and avoiding the friction between the chamber wall and metal billet. So no friction to allow very long extrusion of billet. The ram does not directly act on billet, rather it acts on hydraulic fluid. The turn forces provide hot metals through die. Fluid such as mineral oil with 10% of molybdenum disulphide used.

hydrostatic extrusion or hydraulic extruder diagram
hydrostatic extrusion or hydraulic extruder diagram

hydrostatic extrusion applications:

Most important of extrusion applications followed by.

Extrusion of aluminum parts such as cars, diffuser, grilles and ducting for the architectural. It can be provide extrusion of both commercial and industrial vehicle manufacture. The hydro extrusion provide electronic and engineering product such as light weight, high stress resistant bike frames.

Cold extrusion:

The cold extrusion is also called as impact extrusion the metal billet used for this operation with room temperature or some time heated below the re-crystallization temperature. The metal work for this process in high degree of ductility.

The metal (or) slug is cut from bar stock. The material is placed on the die and ram force applied into the die causing the metal to flow plastically around the punch by means of making a cup shaped part. When the punch is provided with in clearance. Which outer diameter of cup is same as die diameter of cup diameter also equal to punch diameter. The thickness of metal controlled by providing clearance between punch and die.

cold extrusion process Diagram
cold extrusion process Diagram

Cold extrusion material :

  • Nickel
  • Aluminium
  • Steel
  • Copper
  • Magnesium

Cold extrusion applications:

For using impact extrusion method providing collapsible tube for



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