DIFFERENCE BETWEEN OPEN DIE FORGING AND CLOSED DIE FORGING

Forging Processes: Open Die Forging & Closed Die Forging

There are multiple options for metal deformation using the forging concept. The two most common processes are open and closed die forging. While similar in the basic idea of using pressure and temperature to modify material, the two types of forging are made distinct by their use of dies to form the metal.

Open Die Forging

Open die forging is the process of deforming a piece of metal between multiple dies that do not completely enclose the material. The metal is altered as the dies “hammer” or “stamp” the material through a series of movements until the desired shape is achieved. Products formed through open forging often need secondary machining and refining to achieve the tolerances required for the finished specifications. Open die forging is often used for short run forgings of parts that are simple, rather than complex, in design, such as discs, rings, sleeves, cylinders and shafts. Custom shapes can also be produced with open die forging. The repeated working of the material through the deformation process increases the strength of the grain structure. Some additional benefits of open die forging include improved fatigue resistance and strength. Open die forging also reduces voids.

Closed Die Forging

Closed die forging (also referred to as impression die forging) is a metal deformation process that uses pressure to compress a piece of metal to fill an enclosed die impression. In some closed die forging processes, a succession of impression dies are used to modify the shape of the material into the final desired shape and form. The type of material, tightness of tolerances, and need for heat treatment can determine the number of passes the product requires through the dies.

There are two types of equipment that are commonly used for closed die forging: mechanical forging presses and hydraulic forging presses.