Open Die Forging

There are three methods of forging a piece of metal into a desired shape. These are open die forging, closed die forging, and rolled ring forging—with their names offering a general depiction of what each type of custom forging method does. There are advantages to using each method, and many factors are considered in advance to determine which forging type is ideal for different jobs. When a part is forged correctly with the proper equipment and the project is overseen by a highly skilled staff, both open and closed die forging methods and rolled rings will all yield high quality parts. Open die forging is the oldest method of metal working known to man. Also known as hand forging, smith forging, hammer forging, and flat-die forging, open die forging has considerably evolved over the span of hundreds of years as technology and machinery has advanced. This process uses two dies that, unlike in closed die forging, do not completely encase the material. The material is heated to the required temperature, and is placed in between a top die that is attached to a ram, and a bottom die that is attached to either a hammer, anvil or bolster on a press. Once the metal is in place, the dies are used to repeatedly and continuously hit or compress the metal in order to form it into a specific shape. There are many advantages to forging a part in the open die process. The open die method tends to be more cost effective for low volume parts. Additionally, parts forged in this method can result in finer grain sizes and continuous grain flow, resulting in an overall stronger part. Another positive for open die forging is that it is versatile. Any forgeable metal can be forged in the open die method, but generally, steel alloys, copper alloys, brass, Inconel 625, Inconel 718, and titanium alloys are all popular common choices. Reasons why open die forging can be the preferred forging method for certain projects include:

• Parts that are too large to be produced by other manufacturing methods
• Parts that require mechanical properties that cannot be achieved by other metal forming methods
• Orders that have a small quantity requirement that wouldn’t justify tooling costs
• Orders that involve a short delivery requirement, and wouldn’t allow time to make proper tooling

Additionally, this method of forging can be used on parts like rings that have special mechanical requirements, or that may require warm work or cold work, or are too large to be produced on a ring rolling mill. Once a part is forged in this application, it is common to have the product machine finished to achieve a smooth exterior. There are generally two main disadvantages to open die forging. The first is material consumption. While open die forging is ideal for larger parts, this method is limited in close tolerance applications because it is not suited to form more precise details. Another thing to consider with open die forging is that there is typically more machining required for finishing these products.