The Differences Between Cold Extrusion and Hot Extrusion

Summary:Aluminum is one of the most commonly extruded metals, found in everything from w...
Aluminum is one of the most commonly extruded metals, found in everything from windows and doors to automobile frames and pasta. This versatile material is a key part of many modern applications, offering strength, durability and corrosion resistance while keeping the overall cost low. Extruded aluminum is also highly recyclable, making it a sustainable choice for many different types of products.

Forming metals into specific shapes requires specialized fabrication processes, and two of the most common are extrusion and cold drawing. While both of these methods offer the same main benefits, they each have their own unique characteristics that may be better suited for different situations.

Cold extrusion is a method of manufacturing that utilizes a die with openings that are shaped to match the desired finished product. The die is pounded or “extruded” with the help of a hydraulic press, and as the pressure continues to be applied, the aluminum expands through these openings into its final shape. The resulting product is then cut to length and heat-treated as needed.

This type of extrusion process is often used for smaller, thinner profiles and can be utilized with a variety of alloys. It is ideal for creating durable, lightweight components and is frequently used in the automotive industry due to its strength-to-weight ratio. The process can also be used to create large and complex pieces such as railings, window frames and door handles.

In hot extrusion, a hydraulic ram is used to push malleable billets of aluminum through a container that has been preheated to the required temperature. These billets are then pressed against a stationary steel die through which they are forced into their final shape as the ram applies continual pressure. The result is a hollow tube that can be used to carry liquids and pressurized gases.

The most important factor in hot and cold extrusion is the dies that are used to shape the aluminum. These must be able to withstand tremendous forces while maintaining their structural integrity at extremely high temperatures. The machining of these dies can be a very lengthy process, but it is well worth the effort to ensure that they are ready to go into production as soon as possible.

It is also critical to consider the hydrodynamic forces that are exerted upon and by the flowing aluminum as it moves through the die. By some estimates, half of all the energy used during extrusion goes to overcoming this friction, so every effort must be made to reduce these forces. This is a major reason why die designers include generous draft angles along the entire width of the die.

Both of these methods can be used to manufacture a wide range of shapes and sizes for any number of applications. The advantages of each have their own perks, but in general, cold extrusion offers a more consistent quality and can be used with more alloys than hot extrusion. It is important to discuss these differences with an experienced supplier to make the right decision for your project.