The extrusion process is limited to manufacturing objects with only a fixed cross-sectional profile. It is typically used to make straight metallic parts or tubes of varying lengths. Some of the common profiles that are used in extrusion are a solid circle, rectangular, T-shape, L-shape, and tubular profile.
The extrusion process depends on extremely high shear forces and not tensile stress. This allows for the stock material get deformed to great lengths without breaking down. A wear resistant coating is often used in the cavity where the stock material is stored.
Advantages of Extrusion
Extrusion is a process that is common for making components for both industrial and domestic applications. The most significant advantage of this process is its ability to create extremely long and uniform components without sacrificing the strength of the material. The most popular materials that are used for the extrusion process are magnesium, aluminum, and steel as they can be easily thinned down and pushed through.
Some of the major advantages of extrusion are:
- It is extremely cost-effective as the process does not require complex mechanisms.
- Extrusion has high productivity than other long member manufacturing processes due to the speed of its operation.
- It generates a sufficiently high surface finish.
- It is the only process which achieves such low levels of thickness (steel 3 mm (0.120 in), for Aluminum and Magnesium 1mm (0.040 in).
- Extrusion also allows for much smaller cross-section areas as compared to other processes.
- Extrusion offers unparalleled accuracy in maintaining corner and fillet radii.
Types of Extrusion
There are two basic types: cold and hot extrusion.
- Hot Extrusion- Hot extrusion is carried out at very high-temperature ranges (around 50-75% of melting point of the metal). The pressure that is applied ranges in 35-700 MPa. Since such high temperatures and pressure puts enormous stress on the die, special lubricants and coating are used to maintain its life. A popular lubricant that is often used in this process is oil graphite and glass powder.
- Cold Extrusion- Cold extrusion is usually carried out in room-temperature or slightly elevated temperatures. This process is ideal if the materials can withstand the shear stress during the process. The most significant advantage of cold extrusion is the fact that it causes no oxidation. Additionally, if the temperatures are below the recrystallization, then it results in excellent surface finish.
Applications of Cold and Hot Extrusion
Hot extrusion is typically used for materials such as copper, aluminum, and their alloys. Some common products made using hot extrusion are wires, bars and conduit tubes. Cold extrusion can be used with a wide range of metals such as steel, vanadium, titanium, copper, lead, aluminum alloys, molybdenum, and tin. Cold extrusion is used for manufacturing complex parts such as gear blanks, collapsible tubes and structures, aluminum cans and other symmetrical shapes.
Extrusion as a process finds widespread applications in the manufacturing industry, most notably the automobile sector. Vital components of major systems such as engine control, fuel supply, automatic transmission and seat technologies are made using extrusion.