What Are the Differences Between Extruded and Cast Aluminum?

September 20, 2020

What are the differences between extruded and cast aluminum?

  1. Manufacturing Process
  2. Strength
  3. Size of end-products
  4. Rate of production
  5. Secondary techniques
  6. Cost

There are many types of aluminum products that have proven to be useful for different industries. Particularly, there are two processes that are popular among aluminum product manufacturers — cast aluminum and extruded aluminum. You may even find yourself asking the question of “what is the difference between aluminum and cast aluminum?

You should note that extruded aluminum is more often than not, denoted simply as aluminum. Both types of aluminum production processes, however, enjoy a great share in the market. Continue reading to learn more.

Manufacturing Process

Manufacturing process of aluminum
 

On the surface, aluminum extrusion and die-casting (or simply casting) are largely different when it comes to the manufacturing process. You might find that the most common products of the extrusion process may range from pipes, to window frames, door sections, or other kinds of profiles. The die-casting process, on the other hand, results in materials that are typically used in automotive manufacturing — like compressor cylinders or inverter cases.

Simply put, aluminum extrusion involves the passage of a solid aluminum billet into a profile that has specific cross-sections. This makes use of a powerful ram, or high-pressure hydraulic press that forces the billet into profile. The result is the extruded product that likewise takes the form and shape of the cross-section.

The aluminum casting process is much different. Instead of a billet, molten aluminum is utilized to give shape to the resulting product. A steel mold with specific cavities is used to form the cast aluminum product. There needs to be a constant and precise application of speed and pressure so that the aluminum material is evenly distributed throughout the molding.

Strength

Aluminum is a versatile material. Aluminum alloys are durable, lightweight, flexible, and are machined without relative difficulty. However, the expression of these properties may also depend on the manufacturing process — i.e: casting or extruding.

Aluminum extruded products are typically considered to be higher in strength compared to die-cast aluminum. This means that the extrusion products can be used in a variety of structural applications due to the added layer of durability. This means they’re better suited for construction materials like aluminum plates, or perforated sheets.

Cast aluminum products are not ideal for structural applications, but rather for other kinds of equipment that may range from appliances, electric connectors, computer parts, or decorative fixtures.

Size of End-Products

Different sizes of aluminum
 

Unlike cast aluminum, extruded products are limited by the size of the aluminum billet. This means that there are far more opportunities to produce products that are considerably higher and larger in dimension through the casting process. Another factor that limits the method of production has to do with the size of the cross-section, or hydraulic press’ capacity.

With this in mind, it’s more ideal to produce larger-sized aluminum products through casting. The steel mold can be modified and machined in order to accommodate a higher volume of molten aluminum.

Rate of Production

As for the rate of production, the more practical technique is extrusion. As said before, this requires a high-powered passage of a solid billet into a cross-section. It’s fairly simple to manipulate the cross-section, such as changing its length, girth, or width, using different metal fabrication techniques.

The casting process is much slower because it still requires molten aluminum and a precisely-shaped mold. Once the molten material has already solidified, there may still be a need to refine the surface using abrasives.

Secondary Techniques

Secondary process of an aluminum profile
 

Because the rate of production differs between extrusion and casting, it also follows that the latter process requires further polishing and surface refinements. Though the molding process has been assessed to offer maximum precision, small, loose parts may inevitably end up on the surface.

With this in mind, other secondary processes may still need to take place when it comes to aluminum castings. One of these is known as fettling, which is essentially the removal of excess material from the surface of the casted product. As you may already understand, the molding process does not lead to seamless molds. Fettling serves as one of the last stages before the product is finally distributed for industrial use. Due to the hazardous nature of fettling, it’s usually conducted through automated techniques and robotics.

Extrusion products meanwhile require only very minimal requirements, since the precision of the cross-sectional die already contributes to the uniformity of the aluminum extrusion.

Cost

Aluminum casting usually has a higher initial cost compared to extrusion — yet this eventually proves to be the more economical choice, especially in high-volume production.

Going back to the example above, casted aluminum is widely utilized in automotives. Many processes in automotive manufacturing have already been automated, due to the invention of the assembly line. Aluminum castings provide this industry with a faster scheme of component production as well as assembly. Though, one may also find the cost for aluminum extrusion to be comparable. Several factors, such as the minimal level of secondary processing and the simplified method that is found across all extrusion processes all make for an affordable method of aluminum production.

Key Takeaway

What is the difference between aluminum and cast aluminum, you ask? Well these dissimilarities can be found in the production process, cost of operation, secondary techniques, volume of manufacturing, and even the strength of the product. Industries have it in their discretion on whether or not to make use of aluminum castings or extrusions, since each has their own advantages.

When it comes to structural applications, for example, extrusion takes the cake. For parts of scale, casting may be preferred. Nevertheless, it’s still important not to rule out the combination of both casting and extrusion to make the aluminum manufacturing process more efficient.

 


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