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Aluminium extrusion process

Aluminium extrusion 1

What is aluminium profile?

Aluminium extrusion is widely used in construction, automobile and aircraft manufacturing, industrial machinery and consumer goods.Extrusion is a process used to make aluminium lengths with fixed cross section profiles. By extrusion, very complex cross sections can be produced with excellent strength and surface finish.The aluminium extrusion process works by forcing a piece of metal, called a blank, through a die opening with a smaller cross-sectional area than the blank itself.

Extrusion process

The aluminium extrusion process itself is much like the old Play-Doh Shape Maker. When you squeeze the Play-DOH through the press, the outgoing flow will take the shape of the selected die. Similarly, the extruded aluminium takes the shape of a die opening. Using powerful hydraulic presses capable of applying up to 15,000 tons of pressure, aluminium can be extruded into any shape you can imagine.

There are two main methods of aluminum extrusion:

  • direct
  • indirect

Direct extrusion

Direct extrusion is the most important and widely used method in aluminium extrusion. In direct extrusion, the die head remains stationary and the billet is forced through the die using a moving punch. 

Direct extrusion is commonly used to make solid bars, bars, and hollow tubes. The mold design can be modified to produce a variety of solid and hollow sections.

Indirect extrusion

In direct extrusion, it is the blank that moves. In indirect extrusion, the billet remains stationary and the plunger moves the die to apply pressure in the stationary billet. The advantage of keeping the blank at rest is that friction is kept to a minimum.

Design the cross section shape before the extrusion begins. The shape and characteristics of the extruded metal are carefully calculated to maximize function, facilitate assembly, reduce weight, and minimize finishing costs. The unique characteristics of aluminium make it a cost-effective product with superior functionality and excellent finish.

The stage of aluminium extrusion

  • Cast the mold from the cross section of the desired shape.
  • The billet is heated in a furnace until it reaches 750 to 925ºF. At this point, the aluminium becomes a soft solid.
  • Lubrication, called SMUT, is applied to the billet and plunger. Black powder is essential because it ensures that the billet and plunger do not stick together.
  • The plunger applies pressure to the blank, pushing it through the die. In this process, liquid nitrogen is used to cool the mold. Cooling prevents the formation of undesired oxides and extends the length of the die.
  • The extruded aluminium comes out of the mold in the same shape as the mold opening. The extruded piece is pulled onto a cooling stage and exposed to air, water, or a mixture of both (depending on the final mechanical requirements of the metal).
  • Use a stretcher next. This corrects any distortions that may have occurred and straightens the metal. Hardness and strength are increased during stretching.
  • Possibly 50 m long extrusions are fed into a saw conveyor and cut to the desired profile using a circular saw.
  • For some aluminium alloys, manual aging is used to achieve optimal strength. Artificial aging is accomplished by precipitation heat treatment in an aging furnace. The aging process ensures that fine particles are uniformly precipitated through aluminium to improve strength, hardness and elasticity.
  • Finally, the finished profile is finished or manufactured and ready for shipping to the customer.
Aluminium extrusion 2

The benefits of extruding aluminium

Compared with other metals, extruded aluminium has many advantages. Some metals can match some of the desirable properties of aluminium, but no metal can match all of these advantages at once.

The benefits of aluminium profiles are many, including:

  • Light. Aluminum is about one-third the weight of iron, steel, copper or brass. This makes it easier to handle and cheaper to ship. As a result, aluminum is widely used in automotive design, aerospace and high-rise buildings.
  • Strong. Aluminum is strong enough for all but the most demanding applications. Aluminum is ideal for cold environments because it becomes stronger as the temperature drops.
  • Corrosion resistance. Aluminum does not rust. It is protected by a surface oxide film, which can be strengthened by anodizing.
  • Excellent thermal conductivity. Aluminum conducts heat better than most metals. This makes it ideal for heat exchanger operation. Extrusion can be used to produce the most suitable shape for heat transfer.
  • Economic benefits. The extrusion process is relatively cheap. Prototypes can even be made at reasonable cost.
Aluminium extrusion
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