This is a detailed guide about open die forging and closed die forging, including technical drawings and the direct comparison of these two different techniques.
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As we saw in the earlier article “The History of Steel Forging” the forging industry in the past was completely upside down. The techniques were different, the processes were inefficient, and the applications were bizarre! Although the techniques lead the way to advancements in future, a lot of changes were needed to bring efficiency in the process.
However, in the modern society, forging engineering is involved in numerous industries like construction, machinery, agricultural, automotive, oilfield equipment, and more. More the consumption, more the advancement and increase in number of techniques!
Steel billets can be processed and fabricated through various forging processes. Among the widely applied metal forging techniques is the closed die forging and open die forging. Although these two types of forging methods belong to the forging basics, it is not so difficult to point out the differences between the two.
Let us have a deeper insight into the differences between open and closed die forging!
Open and Closed Die Forging Processes in Comparison
Original Source: Suranaree University of Technology
Open die forging process is also known as free forging. The piece of metal is deformed between multiple dies that do not enclose the metal entirely. The dies hammer and stamp the metal through a series of movements to alter its dimensions until the desired shape is achieved.
Closed die forging process is also referred to as impression forging. It utilizes pressure to compress the metal piece to fill an enclosed die impression. A medium frequency induction heating furnace is used to heat the metal to get the desired shapes.
The technique of both open die forging and closed die forging is different. In general, for closed die forging, the molding dies are first made. The metal bars are then placed on the dies and forged to any shapes that are desired.The closed die forging technique utilizes very less or no machining throughout the process. Also, net shape end products can be achieved.
For open die forging, enormous compressive forces are imposed by the continuous strike of a forging hammer to deform the metal billets. Go through the image illustration of the open die forging process here.
Interested in a short visual documentary on the open and closed die forging processes? Check out the forging process video:
The Forging Process of open die and closed die forgings
Source: Youtube
The forged components obtained by open die forging and closed die forging, if compared, are not identical in their application scope. Usually, the metals become stronger and tougher after the forging process due to the modification in its internal grain structure.
A rough precision machining is further required after the open die forging process as imprecise dimensions are achieved by hammering. The open die metal forge parts are more suitable for large parts in a number of tons. Generally, the products in this category of forging include forged long shafts, forged rollers, and forged cylinders. They are mostly utilized in the railway and the aircraft industry.
However, for small parts, closed die forging is preferred as high precision is obtained in the process. It is highly used to produce forged fittings, forged flange, forged automotive parts, etc. Oilfield, automotive, and mining are some of the industries that rely on closed die forge parts.
Advantages & Disadvantages
List of References:
[1] – http://www.canforge.com/open-die-forging/
If you want to learn more, please visit our website open die forging service.
[2] – http://www.ferralloy.com/open-die-forging-explained/
[3] – http://www.dropforging.net/closed-die-forging.html
[4] – http://www.ferralloy.com/closed-die-forging-process-applications/
[5] – http://www.scotforge.com/Why-Forging/Forging-101/Open-Die-Forging
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Please notice that you might be interested in the other technical articles we’ve published:
• What is Steel Forging?
• The History of Steel Forging
• Hot Rolled Steel, Cold Rolled Steel & Cold Drawn Steel – What’s the difference?
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The two types of die forging, open and closed, offer different advantages for forging metal. First, you need to understand the difference in the two processes and what the benefits are to the variations. This will help you to decide which process is best for what you are looking to achieve.
Open die forging, also known as free forging, deforms and then shapes a piece of metal between multiple dies without enclosing the metal entirely. The dies hammer and stamp the metal using a series of movements until it reaches its desired form.
Closed die forging or impression die forging, utilises pressure to compress a piece of metal to fit into an enclosed die impression.
Open die forging is typically used for products made in small quantities with simplistic shapes, for instance disks, rings, sleeves, cylinders and shafts. Customised shapes can also be made, but the more complex a shape, the harder it is for open die forging to achieve without further machining.
A structure’s strength will increase during the deformation process of open die thanks to the repeated working of the metal billet, whilst also improving the fatigue resistance, giving the metal longer endurance and a better microstructure (grain). There is a reduced chance of voids, which are defects in metals during the solidification process.
Open die forging offers more advantages than just being a superior product, including no tooling cost and its far more cost-effective on a small scale for your business too.
Although the cost for close die forging is higher due to the precision machinery required, the upper and lower dies used can forge any shape needed. Allowing for extra specificity in the forging process and the opportunity for more complex designs.
If you are forming metal shapes on a larger production scale, closed die is economically viable because of the specialised machinery needed. If you are only making a small amount of close die items, it would not be financially advisable.
Metal dimensions of tighter tolerances and net shapes can be achieved, with the internal grain structure tighter than open die structures. There is an increased chance of better surface finish, even if voids are more likely.
For more information, please visit Open die forging solution.