Extrusion is the process used to create sections of aluminium from a fixed cross-section profile. Through extrusion, very complex cross sections can be created with excellent strength and surface finish.
The aluminium extrusion process works by forcing a block of metal, known as a billet, through the die opening with a smaller cross-sectional area than the billet itself.
The extrusion process
The extrusion process itself is very similar to the old Play-Doh Shape Maker. When you squeeze the Play-Doh compound through the press, the stream that comes out takes the shape of the selected mold. Likewise, extruded aluminium takes the shape of the die opening. By using powerful hydraulic presses capable of exerting up to 15,000 tons of pressure, aluminium can be extruded into any shape you can imagine.
Direct extrusion
Direct extrusion is the most important and widespread method used in aluminium extrusion profiles manufacturers. In direct extrusion, the die head is held stationary and the aluminium billet is forced through the die by a moving piston.
Direct extrusion is commonly used in the manufacture of solid rods, bars, and hollow tubes. The die design can be modified to produce a wide variety of solid and hollow profiles.
Indirect extrusion
In direct extrusion, it is the billet that moves. In indirect extrusion, the aluminium billet is held stationary and the ram moves the die to exert pressure on the stationary billet. The advantage of keeping the billet stationary is to keep friction to a minimum.
Before extrusion begins, the cross-sectional shape is designed. The shape and characteristics of the extruded metal are carefully calculated to maximize functionality, ease assembly, reduce weight and minimize finishing costs. The unique characteristics of aluminium make it a cost-effective product with excellent functionality and a great finish.
The stages in aluminium extrusion
A die is molded from the cross section of the desired shape.
Aluminium billets are heated in an oven until they reach 750-925ºF. At this point, the aluminium becomes a soft solid.
Lubrication, known as smut, is applied to the billet and ram. The smut is essential as it ensures that the billet and ram do not stick together.
The ram applies pressure to the billet, pushing it through the die. During this process, liquid nitrogen is used to cool the matrix. Cooling prevents the formation of undesirable oxides, in addition to prolonging the length of the matrix.
The extruded aluminium emerges from the die, taking the same shape as the die opening from Tamilnadu aluminium company. The extrusion is taken to a cooling table where it is exposed to air, water, or a mixture of both (depending on the final mechanical requirements of the metal).
A stretcher is then applied. This corrects any twisting that may have occurred and straightens the metal. Hardness and strength improve during the stretching process.
The extrusions, which can be 50 meters long, are fed onto a saw conveyor and cut to the required profiles with a circular saw.
For some aluminium alloys, an artificial aging process is applied to achieve optimum strength. Artificial aging is achieved by precipitation heat treatment in an aging oven. The aging process ensures uniform precipitation of fine particles throughout the aluminium to improve strength, hardness and elasticity.
Finally, the finished profiles are taken to finishing or manufacturing, ready to be shipped to the customer from best aluminium company in Chennai.
Benefits of Extruded Aluminium
Extruded aluminium has a number of advantages over other metals. There are metals that can match some of the desirable characteristics of aluminium, but no metal can match all of these benefits at once.
The benefits of aluminium extrusions are many and include:
• Light. Aluminium is about one-third the weight of iron, steel, copper, or brass. This makes it easier to handle and cheaper to ship. For this reason, aluminium is widely used in automotive design, the aerospace industry, and high-rise construction.
• Strong. The strength of aluminium is sufficient for all but the most demanding applications. Aluminium is well suited to cold environments as it gets stronger as temperatures drop.
• Corrosion resistant. Aluminium does not rust. It is protected by a surface film of oxide, and this protection can be enhanced by anodizing.
• Excellent thermal conductivity. Aluminium conducts heat better than most metals. This makes it ideal for heat exchanger operations. Extrusion can be used to produce optimal shapes for thermal conduction.
• Accessible. The extrusion process is relatively inexpensive. Prototypes can even be made at a reasonable cost.
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