The extrusion process can be categorized into warm extrusion and cold extrusion. These three types differ in the temperatures to which metals are exposed to and several other aspects. To make things clearer, let me start by defining the term extrusion.
What is extrusion?
Extrusion is a process used in metals to change them into different shapes. The final products are then used in several industries such as automobile and aircraft companies. The process of shaping the metal is done by pushing it into a series of dies until the desired shape is achieved. Machineries and tools that come in various sizes and functionalities are used in order to do things faster and more efficiently.
What is hot extrusion?
Hot extrusion can also be referred to as hot working. It is the process where a piece of metal is deformed or melted by applying heat greater than its recrystallization temperature.
Extrusion may involve several sub-processes and they are drawing, forging, rolling and rotary piercing.
In drawing, tensile forces are used to stretch a metal. You can do any of the following drawing types: sheet, bar, tube or wire drawing.
In forging, localized compressive forces do the job. There are at least seven most common types and they are: drop, roll, press, upset, automatic hot, net-shape, near-net-shape, and induction forging.
In rolling, a pair or series of rolls are used where a metal stock could pass through. Flat, ring, and foil rolling are just three of the common rolling processes used today.
In rotary piercing, seamless tubing that has thick walls is formed. The process has two kinds: the Stiefel process and the Mannesmann process.
What are the advantages of hot extrusion over the other extrusion processes?
Some of the pros of doing hot extrusion are the following:
- The material produced via hot extrusion is more ductile compared to the material produced via other processes.
- It is much easier to perform hot extrusion because it requires less force and energy.
- During the deformation process, the pores found in the metal are reduced in size or are completely closed up.
- Because this process is done at very high temperatures, chemical inhomogeneities are minimized or are totally eradicated.
But, just like other things in this world, hot extrusion also has disadvantages. Here are some:
- There might be unwanted reactions that may result from the exposure of the metal to the atmosphere of the surroundings.
- You may need to purchase costly machineries such as an induction heater or a diesel furnace.