Converting Extruded Aluminum to Forged Aluminum
Anchor Harvey is renowned for producing high-quality forged aluminum products, but not all customers will be familiar with the advantages that forged aluminum products have over other forms of aluminum metal forming, such as extrusion. One of the more common forms of metal forming is the extrusion process. Customers looking for the perfect part for their product may be wondering, what are the advantages and disadvantages between extrusion and forging?
The following will provide you with a comparative understanding of the extrusion and forging processes and what the differences therein mean for the final product and their specific use cases.
What is Extrusion?
Extrusion, including extruded aluminum, is a process that creates a product of a fixed cross-sectional profile along its entire length. The process begins with a die of a fixed shape and a bar of stock (most often round-stock) that is forced through the die to conform to the shape of the die. This requires that the stock is larger than the shape of the die, and thus the stock is narrowed and shaped simultaneously by the thick steel die and the powerful press.
A sister process of extrusion is called “drawing,” which simply pulls the stock through the die instead of pushing it through the die. This process often limits the number of sequential extrusion steps that can be performed quickly and is often only used for simpler extruded shapes like wire and round tubing.
Extrusion can be performed on hot or cold material, though with complex shapes and extreme shape changes, hot extrusion is necessary. Extrusion can be performed on many different types of materials and is very useful for producing tubing and small or medium-sized identical parts that can be cut from a longer piece of extruded stock. The finish on extruded stock is quite good, and brittle materials can be easily extruded due to the support from the die and simple forces present in the extrusion process.
What is Forging?
Forging is the process of using heat and pressure to form metals into a specific shape, and forging transforms a metal stock through these processes without ever melting the metal stock. In this way, forging is generally similar to the process of extrusion, but forging will typically only works with a single part at a time.
Forging, like extrusion, can include the use of many ton presses but can also fall under the category of hammer forging and roll forging:
- Hammer Forging: Hammer forging uses a powerful steam, electrical, or air pressure powered hammer to strike upset a workpiece with quick and repeated strikes. This can quickly reshape a heavy or thick piece of metal with a smaller hammer and lower overall pressures than would be required of a press. Hammer forging, however, is only used in open die forging.
- Press Forging: Presses apply a continuous force to the top and bottom of a material to form it into a shape. Often, a press requires higher power input and larger pressures than a hammer but can reshape materials into a large variety of shapes with more shaping capabilities than a hammer. Press forging can be used with open dies (where the die does not completely enclose the workpiece) or with closed dies (where the die completely encloses the workpiece). A 3-dimensional shaped part will almost always be created using a closed-die press.
- Roll Forging: Roll forging is the process of heating a material and passing it through heavy steel rollers to reduce the size and elongate the material. Roll forging does not have to produce round parts; roll forging can produce both square and rectangular billets, and patterns can be added to a roller to impart that pattern onto a workpiece.
What is the Difference Between Forging and Extrusion?
Because of aluminum’s properties, extrusion and forging can each place a piece of aluminum stock under very extreme stresses that would not be possible with other metals such as steel. The ductility and elasticity of aluminum make it an ideal material for both extrusion and forging. Aluminum can also assume more complex and extreme shapes without suffering a probable failure when compared to steel.
So, what are the advantages of forged aluminum versus extruded aluminum? There are two main ones:
- Complex Shaping: Extrusion requires a round stock and a specific set of criteria for the die. Creating central holes or other closed cavities in the center of stock requires complex tooling, and other complex shapes are impossible to extrude. In contrast, forging can easily produce those shapes with minimal complex engineering. Closed-die forging especially can produce nearly any shape, which may be difficult to produce through extrusion. In addition, forging works in 3-dimensions, whereas extrusion only works in 2-dimensions, meaning that angles that are impossible in extrusion are easy to produce through forging.
- Versatility: Due to the differences in shaping capabilities, extrusion is just not useful for many common forms and shapes. Extrusion is useful for long or tubular shapes that require a consistent 2-dimensional cross-shape that can be cut into many parts but is unsuitable for anything requiring a 3-dimensional shape or angles. Converting extruded aluminum to these kinds of shapes requires complex post-extrusion processes, which all but nullifies the speed gains from the extrusion process.
Extrusion is a necessary process for metal forming and serves its purpose for specific jobs. However, many of the most common applications within the aerospace industry require strong and complex parts that just cannot be achieved through the extrusion process.
So, when it comes to extrusion vs forging, when customers need components that combine the strongest materials, the most effective manufacturing methods, the fastest turnaround times, and custom-tailored solutions for individual needs, look no further than the premier forged aluminum products made at Anchor Harvey. Request a quote today.