The extrusion process pushes metal through a pre-formed die to shape it into a carefully designed cross-sectional profile. This process can achieve intricate cross-sections while simultaneously creating a quality surface finish. Many find this process especially useful for weak or brittle metals, since extruding relies entirely on compression and shearing.
The extrusion process is available in two different types. Continuous extrusions, in theory, can go on forever, creating one endless piece of material. Semi-continuous extrusions, conversely, are created in sections and create multiple extruded pieces.
How Is Metal Extruded?
Extruding metals may also increase the strength of the material and can be done with either hot or cold material.
Heated billets of metal are hydraulically compressed into cylinders that contain dies. The dies allow the pressurized billet to escape via orifices of the desired shape. The metal emerges from these openings as a continuous bar with the same cross-sectional shape as the die opening. With the use of two sets of dies, stepped extrusions are created.
Lubricant reduces friction, protecting the die surfaces. Graphite is often used on non-ferrous alloys, and glass is the lubricant of choice for hot steel extrusion. The extrusion process can produce a wide array of configurations, including complex non-uniform and non-symmetrical shapes that would be difficult or impossible to roll. Metal extrusions can easily replace cumbersome or uneven seams created through other methods such as joining, welding, or riveting.
The extrusion of cold metal has gone by a variety of names, including:
- Impact extrusion
- Cold forging
- Cold extrusion forging
- Cold pressing
- Extrusion pressing
However, cold extrusion is likely the most common term in the steel sector. Impact extrusion is also a widely accepted term for the cold extrusion of non-ferrous metals.
The process usually involves a high-speed punch, which strikes a metal blank within a die cavity. The force of the punch drives the blank through space between the punch and die. The speed and distance of the punch can be controlled via various mechanical settings on the machine itself. The thickness of the final extruded part is will be determined by the distance setting.
Cold extrusion offers high strength, because of severe strain-hardening, good finish, stringent accuracy, and lower production costs due to less operational setup and requirements.
Which Metals Are Used for Custom Extrusions?
Almost any metals can be extruded, though doing so can be cost-prohibitive for high strength alloys. Below is a list of the most common metals used independently, or as alloys, as well as examples of their common end uses.
Manufacturers can extrude aluminum—the most frequently extruded material—using either the hot or cold methods. Extruded aluminum can be fabricated, painted, and anodized, and it produces complex cross-sections with aesthetically pleasing surface finishes. Because of its high corrosion resistance and excellent thermal conductivity, extruded-aluminum products play large roles in the construction, automotive, aerospace, industrial, and domestic product manufacturing sectors. Because of its light weight and affordability, aluminum is the metal of choice for extrusion projects that seek to optimize strength without sacrificing the end product’s weight.
Brass extrusions create end products that resist corrosion, benefiting applications that require optimal performance for long periods in various weather or atmospheric conditions. Brass-extruded products are known for their durability and aesthetic appeal, providing a golden glaze on handrails, doors, columns, furniture, gates, and other ornamental materials. Brass products also form major parts of automotive components, pipe connectors, and industrial machinery.
Like aluminum, titanium provides a similar level of strength compared to heavier metals like steel, but its density is lighter, allowing manufacturers to reduce the amount their end products weigh. Aerospace manufacturers especially value titanium for its heat-resistant properties, keeping its shape at temperatures exceeding 800°C. Extruded titanium also undergoes a number of finishing processes such as heat treatment to refine grain structure and chemical treatment to enhance machinability.
Nickel extrusion creates high-strength products that are silver-gray in appearance. Despite nickel’s toughness, extruded-nickel products retain a degree of malleability that allow them to perform well in a variety of applications. Because nickel can withstand direct impacts without weighing too much, it’s ideal for door and window fasteners, locks, mining equipment, musical instruments, animal harnesses, electronic components, and industrial machinery. Nickel also can be alloyed with metals including silver, copper, and zinc, creating a variety of color customization options and allowing it to be used for a range of architectural purposes.
Metal extrusion also works well with copper, zirconium, and beryllium. Electronics manufacturers in particular rely on extruded copper to create wire, and it also forms essential parts of electrodes for welding, pipes, bars, and tubes. Zirconium benefits a wide range of forming and mechanical applications, and beryllium appears in many military and commercial guidance systems as well as the structural components of satellites and spacecraft, alloying well with copper.
Lynch Metals Offers Custom Aluminum Extrusions
Strong, durable, and light, extruded aluminum offers design flexibility as a corrosion-resistance choice for a wide variety of needs. Aluminum’s physical characteristics of malleability and ductility allow it to be easily extruded. At one third the density and stiffness of steel, extruded aluminum provides for both strength and stability at an efficient production cost. Coming with a low recyclability cost, aluminum has a very high rate of scrap recovery, making it a highly economical and environmentally sustainable material.
At Lynch Metals, we specialize in working with our customers to develop cost-effective engineered material solutions, such as extruded aluminum. Feel free to contact us with your questions regarding aluminum extrusion sourcing and distribution to see how Lynch Metals can positively impact your bottom line.
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