Metal Extrusion

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  • Topic: Extrusion, Friction, Aluminium
  • Pages : 35 (5576 words )
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  • Published : February 19, 2013
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Chapter 4

Extrusion
Subjects of interest
• Introduction/objectives • Classification of extrusion processes • Extrusion equipment (Presses, dies and tools) • Hot extrusion • Deformation, lubrication, and defects in extrusion • Analysis of the extrusion process • Cold extrusion and cold-forming • Hydrostatic extrusion • Extrusion of tubing • Production of seamless pipe and tubing Suranaree University of Technology

Tapany Udomphol

Jan-Mar 2007

Objective
• This chapter aims to provide useful information on different extrusions processes, which can be mainly divided into direct and indirect extrusion processes. This also includes basic background on hydrostatic extrusion, extrusions of tubing and production of seamless pipe and tubing. • Principal background and concept of extrusion will be addressed along with the utilisation of mathematical approaches to understand the calculation of extrusion load. • The role of lubricants on the deformation process which results in the improvement in extrusion products will be provided. • Finally, defects and its solutions occurring in the extrusion process will be emphasised.

Suranaree University of Technology

Tapany Udomphol

Jan-Mar 2007

What is extrusion?
Extrusion is the process by which a block/billet of metal is reduced in cross section by forcing it to flow through a die orifice under high pressure. • In general, extrusion is used to produce cylindrical bars or hollow tubes or for the starting stock for drawn rod, cold extrusion or forged products. • Most metals are hot extruded due to large amount of forces required in extrusion. Complex shape can be extruded from the more readily extrudable metals such as aluminium. * The products obtained are also called extrusion. Suranaree University of Technology

Tapany Udomphol

Jan-Mar 2007

• The reaction of the extrusion billet with the container and die results in high compressive stresses which are effective in reducing cracking of materials during primary breakdown from the ingot.

• This helps to increase the utilisation of extrusion in the working of metals that are difficult to form like stainless steels, nickel-based alloys, and other high-temperature materials. • Similar to forging, lower ram force and a fine grained recrystallised structure are possible in hot extrusion. • However, better surface finish and higher strengths (strain hardened metals) are provided by cold extrusion. Suranaree University of Technology

Tapany Udomphol

Jan-Mar 2007

Extrusion products
Typical parts produced by extrusion are trim parts used in automotive and construction applications, window frame members, railings, aircraft structural parts. Example: Aluminium extrusions are used in commercial and domestic buildings for window and door frame systems, prefabricated houses/building structures, roofing and exterior cladding, curtain walling, shop fronts, etc. Furthermore, extrusions are also used in transport for airframes, road and rail vehicles and in marine applications. Aluminium extrusions Brass parts

Aluminium for windows and doors

Suranaree University of Technology

Tapany Udomphol

Jan-Mar 2006

Classification of extrusion processes
There are several ways to classify metal extrusion processes;

By direction

• Direct / Indirect extrusion • Forward / backward extrusion

By operating temperature

• Hot / cold extrusion

By equipment

• Horizontal and vertical extrusion

Suranaree University of Technology

Tapany Udomphol

Jan-Mar 2007

Direct and indirect extrusions
1) Direct extrusion
extrusion container dummy plate ram die billet

• The metal billet is placed in a container and driven through the die by the ram. • The dummy block or pressure plate, is placed at the end of the ram in contact with the billet. • Friction is at the die and container wall requires higher pressure than indirect extrusion. • The hollow ram containing the die is kept stationary and the...
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