Open Die vs. Closed Die Forging: What You Need to Know

Two of the most common forging techniques are open die forging and closed die forging. Both have their own processes, advantages, disadvantages, and applications across various industries. These types of forging are commonly done in the aircraft, aerospace, or oil industries. Learn the differences with Steel Industries and find the right type for you.


What IS Open Die Forging? Closed Die Forging?

Open die forging, sometimes called “free forging”, is the process of taking a piece of metal and shaping it into a desired form. While doing this, the metal is positioned between multiple dies that don’t completely enclose it. This type of forging is typically used in rough machining that will need further work, such as forged long shafts, rollers, or cylinders in the aerospace, defense, nuclear, power, and transportation industries. 


Closed die forging, also called “impression die forging”, is the shaping process that compresses a piece of metal under high pressure to fill an enclosed die. It will be sealed completely around the material to precisely shape the metal. This process is commonly used in the oil, automotive, forestry/agriculture, and mining industries. Closed die will focus more on small critical parts with safety roles/considerations, since the increased precision means it can create intricate and solid components. 


Processes of Open vs. Closed Die Forging

Open die forging is a very simple process, made of only a few steps. 

  1. Desired metal is placed between the dies.
  2. Enormous compressive forces push down to force the metal into the shaped dies (although they are not closed all the way). 
  3. A hammer or other large tools are used to forge the piece further, for whatever the compressive force does not do. 


That’s it! Open die forging is a relatively simple process, made to help companies with short run production schedules. 


Closed die forging is slightly more complicated, with more intricate processes at the start to reach the desired result. 

  1. The dies are precisely machined and molded into the specified desired  shape. This often is done on an individual basis, as closed-die focuses on more unique pieces for each case. 
  2. Metal bars or sheets are placed between the upper and lower dies. 
  3. The piece is forged into the necessary desired shape. 


The increase in complexity here comes with the need to create precise and different dies to mold the forged metals later on in the process. 


Advantages & Disadvantages of Open Die vs Closed Die 

Both of these processes have their advantages and disadvantages, especially for different industries and intended applications. Steel Industries specializes in open die forging, but can offer both. Check out our blog post on the advantages of open die forging for more details on the pros of this type of forging. 


◊ Open Die Forging

Advantages of Open Die: 

  • Better fatigue resistance, improved microstructure
  • Continuous grain flow, finer grain size
  • High strength, longer part life
  • Less material waste
  • Valuable cost savings- cost effective even in short runs


Disadvantages of Open Die: 

  • Not able to form intricate precision parts or close-tolerance applications
  • Extra machining and fine-tuning is often required


◊ Closed Die Forging

Advantages of Closed Die Forging: 

  • Internal grain structure formation increases the tightness and strength of products
  • Economical for large production runs and specialized parts
  • No material limitations
  • Little to no machining/extra processes required 
  • Tighter tolerances and net shapes are possible


Disadvantages of Closed Die: 

  • Not cost effective for short runs
  • High cost to create the dies for production
  • Creates a more dangerous working environment due to the extreme heat and crushing of equipment metals


Open die and closed die forging both offer different advantages, depending on what your goal is for your business. It is important to work with your manufacturer to select the best option to produce the best result for you. 

Steel Industries is proud to offer open die forging services to a variety of industries including (list some). View our open die capabilities now.

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