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What Is Closed Die Forging?

what is closed die forging

In this process, precut dies known as “tooling” are brought together to completely or partially surround a heated raw material like steel or aluminum. Situated in the bottom die, the material starts off at a size and shape that roughly approximates the final forged product. 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.

What Happens During Closed Die Forging?

Also referred to as impression-die forging, closed die forging is when two or more dies come together to form raw stock into a final product. The process 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.

Carbon, alloy steels, stainless steel, aluminum, copper alloys, and some titanium alloys can be forged using closed die forging. More specialized processes and/or equipment may be required for certain materials, such as refractory alloys, nickel-based super-alloys, and magnesium.

Some shapes, like rectangular solids and simple spherical shapes, are easier to form than others. At Trenton Forging, our capabilities allow us to create any number of shapes, including parts with long, thin sections or more intricate details like ribs and, flanges, and pockets.

What Is Closed Die Forging ‘Upsetting,’ and Why Does It Matter?

Upsetting is a specialized closed 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.

What Is the Difference Between Hot Forging, Cold Forging, and 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.

Engineered for Quality, Integrity, Strength, and Longevity

Now that you know what is closed die forging, you can understand why we take it seriously. That’s why we heat and form billets in a way that maximizes the strength and lifetime of our manufactured products. With custom-machined dies and a cost-effective closed die forging process that reduces post-processing, we strive to produce products that not only last longer but are engineered for maximum strength and quality.

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