Closed Die Forging: The Definitive Guide
What Is Closed Die Forging? Also referred to as impression die forging, closed die forging is when two or more dies are brought together to completely or partially surround a heated raw material like steel or aluminum. When the top die is pressed against it, the profile of the final part takes shape from the pressure of the two dies that are pressed against it forming it in the process into a final product or “forging”.
Closed die forging can produce an astounding number of three-dimensional shapes, ranging from just a few ounces to more than 25 tons. Commonly used presses include mechanical presses, hammer, and hydraulic presses with capacities spanning from 20,000 to 50,000 tons.
Open Die Forging vs Closed Die Forging
The main difference between closed and open-die forging is that the latter does not enclose the workpiece. The workpiece is moved within the open die to shape it. Conversely, a closed die has the entire part profile cut into it. The workpiece is completely enclosed by the upper and lower dies.
Closed die forging is capable of creating highly complex products. The dies can be cut to form almost any shape. Plus, more than two dies can be used when needed. However, it is not suitable for very large shapes due to the excessively large dies that would be necessary. Using the closed process creates a better surface finish and increased overall strength and tightness of the grain structure resulting in a forging with improved longevity and strength.
For mass-produced components, a closed die forging is a recommended option that doesn’t require additional industrial equipment to achieve the ideal finish.
Another thing to keep in mind when considering closed vs open die forging is that a closed die forge requires more time and investment to create the die tooling. The closed design requires these closed-impression dies to be constructed with precision to prevent voids and to improve the tolerance of your machining.
When comparing open die forging vs closed a major factor to consider is that an open die requires additional equipment to achieve a final product. An open die is best used to create simple objects, such as rings, cylinders and discs, but the additional equipment requirements make it less than optimal for precision custom forgings. Both options can provide great results when performed by an expert forging company.
Closed Die Forging Process
Also referred to as impression forging, this type of forging requires state-of-the-art forging equipment for precision results. At our American forging company, we use an air-lift, gravity-drop hammer to provide the force necessary to create a detailed component out of a steel billet. When it comes to drop forged steel here is the basic process when forging manufacturing:
- Raw material procurement
- Tool creation and testing
- Cleaning and heat treating
- Coining and piercing
- Final inspection and shipping
This process ensures you receive accurate components that aren’t affected by voids or surface finish issues. If you need coating, machining, pull testing or additional testing and processing, we incorporate these elements into the timeline and work to start shipping your components in a prompt and efficient manner to meet your deadlines.
Commonly Used Metals
Carbon, alloy steels, stainless steel, aluminum, copper alloys, and some titanium alloys can be forged using this process. More specialized processes and/or equipment may be required for certain materials, such as refractory alloys, nickel-based super-alloys, and magnesium.
Hot Forging vs Cold Forging vs Warm Forging
Hot forging and cold forging can deliver similar results, but the processes have basic differences. Simply put, hot forging involves shaping a piece of metal (known as a billet or workpiece) into a predefined shape through hammering, upsetting, or other pressing processes where the workpiece is heated to roughly 75% of the temperate at which it melts.
Transmission gears, neck rings for LP gas cylinders, and tapered roller bearing braces are examples of products commonly manufactured through hot forging.
Cold forging, on the other hand, simply involves putting stock between two dies and squeezing the dies together. Screws, bits, camshafts, and axles are all examples of common, everyday items formed through cold forging.
Finally, when the workpiece is heated to a temperature that’s above its hardening temperature yet below the temperature where scale would form, we have what’s called “warm forging.”
Warm forging avoids the expense of cold forging while achieving a level of precision hot forging can’t reliably match. Examples of components formed with warm forging include gears, shafts, and automotive front-wheel-drive tulips.
What Is ‘Upsetting,’ and Why Does It Matter?
Upsetting is a specialized closed style die forging process where metal is plastically deformed under immense pressure into varying sizes of high-strength components. For longer components where only one end needs to be forged, it can be an ideal choice.
Operating on a horizontal plane, a mechanical press used for upsetting takes advantage of split “grip” dies (dies with grooves in them) that allow material to extrude beyond the boundaries of the press. Sometimes, a third die is attached to the header and aids the forming process as well.
The process produces shapes of exceptional strength because the shape of the finished product is oriented the same way as the grain flow of the material. Going with the grain reduces the chances of cracks and defects in the finished product.
With custom-machined dies and a cost-effective forging process that reduces post-processing, Our forging company strives to produce products that not only last longer but are engineered for maximum strength and quality. Contact us today for more details.