What is Die Forging?
Definition: Die forging is a forging process in which the deformation of a workpiece takes place between the dies by the application of high compressive forces.
There are basically 2 types of die forging process that are used in industries to forge the steel (or other metals).
- Open die forging
- Closed die forging
Let’s see each of these die casting processes one by one.
Open die forging
What is Open Die Forging (or Smith Forging)?
Open die forging (also known as Smith forging) is a forging process in which the deformation of a workpiece takes place between the dies that do not completely enclose the workpiece.
In open die forging, the metal is heated above its recrystallization temperature which improves its plastic deformation with less force.
The dies used in open die forging are generally flat, but some dies can have specific shapes for different applications. For example, a die may have a round shape or concave shape, or convex shape.
Open die forging is basically used to forge larger metal pieces that are not possible to forge with closed die forging.
The simple type of Smith forging process is also called upsetting forging in which the metal piece is placed between the two flat dies and its height is reduced by compressive forces.
As the height of the workpiece is reduced by the compressive forces, its width increases since it has constant volume.
Closed die forging
What is Closed Die Forging?
Closed die forging (also known as Impression Die Forging) is a process in which the deformation of a workpiece takes place between the dies that completely encloses the workpiece.
Closed die forging (or impression die forging) process
In closed die forging process, the pair of matched dies having contoured impressions are used.
The dies used in impression die forging are such that it restricts the flow of metal within the die during its deformation.
The metal fills up in the space within the die cavity as it gets compressed into the molds.
Because of this, the impression of the die is left on the workpiece and in this way, the final forged metal is obtained.
Sometimes the desired shape is not achieved in a single impression. So two or more progressive impressions are used in conjunction to get the desired impression on the workpiece.
You can see the closed die forging process of a crankshaft in the above image.
The desired shape of crankshaft is achieved in several stages.
If the metal is hot worked properly, then it improves its plastic flow as well as it reduces the forces on the dies and other tools.
By impression die forging process, the flash or fins are formed around the forged part.
During the design of a forging process, the volume of starting workpiece is kept slightly more than the volume of the closed die cavity.
As the die closes, the workpiece gets deformed into it and the impression of the die is formed on the workpiece.