What is Metal Forging?
Metal forging is the process of creating shaped metals with tools. Smiths have been forging metals for thousands of years, creating everything from weaponry to tableware. Forged parts are used in almost everything these days, and machinery typically uses forged parts because they have a high strength level.
Forged components can range in size from a few ounces to hundreds of tons. The process takes the metal and either hammer it into the shape needed or presses it with a die.
How Many Forging Processes are There?
Forging processes fall into a few different classifications. There is cold, warm, and hot forging. These are further broken down into:
- Cold Forging
- Impression Die Forging
- Open Die Forging
- Seamless Rolled Ring Forging
Cold forging takes low-carbon and lower alloy metals and forges them into shapes using dies. Cold is largely the most common method used today. With this approach, smaller parts can be produced in a wide variety of forms. The process does limit the weight of the parts to a far lower range than traditional warm and hot forging.
The impression die method uses two dies to press metal between. The process creates 3-d shapes that can be anywhere from a few ounces to over 60,000 pounds. The impression die method is usually done on hydraulic presses that can handle anything up to 50,000 tons. Mechanical presses and hammers are also common, though with lower weight tolerances.
The open die method uses flat dies to hammer or press large parts into shape. The dies have no precut profiles, and the piece being shaped is moved throughout the process. That movement allows the shaping of items up to 80 feet in length. Open die can handle pieces over 150 tons.
Seamless rolled ring forging punches a hole in the thick, round metal and then rolling, pounding, or squeezing the round metal into a predetermined thickness. These rings can vary from a couple of inches to over 30 feet.
What are the Differences between These Processes?
Most metal forging is done at relatively high temperatures, up to 2300 degrees. With cold, the temperature of the metal can range from room temperature to several hundred degrees. Two dies are typically used to press the metal between. This die process, also called tooling, takes a precut design of the part required and pressed the metal between the two dies.
The most commonly used cold forge items are generally lighter in weight, often in the five to ten-pound range. While there are several specific techniques used in cold forge metals, the most abundant are created using impression die.
Metals used range from lower alloy and carbon steels to 300 and 400 series stainless, brass and bronze, and some aluminum alloys.
Impression Die Forging
Cold forging typically uses this process to create parts. Warm and hot methods are more commonly done with impression die.
Carbon and alloy steels, stainless steel, tool steels, copper, aluminum, and some titanium alloys can be forged using conventional impression die methods.
Open Die Forging
Open die methods can forge large parts into a wide range of shapes. Round, rectangular, square, hexagonal, step down shafts like rotors and spindles, hollow bodies, and many more are possible with this process.
Multiple open die processes can be combined to create the perfected part. With the ability to integrate processes, it offers a wide range of flexibility in the creation process.
Almost all forgeable alloys can be used on the open die forge. It has the capability to handle some superalloys and corrosion-resistant alloys.
Seamless Rolled Ring Forging
Creating seamless rolled rings adds a high level of strength to the metal, in turn making them ideal for components like gears, bearings, rotor spacers, couplings, flanges, pressure valve bodies, and more.
Seamless rolled ring methods can work with carbon and alloy steels, non-ferrous alloys like aluminum, copper, titanium, and nickel alloys.