Brass forging is a process in which a forging press places extreme pressure on a single piece of brass or brass alloy that has been heated to about 1,500 degrees F (815 degrees C). The softened metal is then forced, beaten, and shaped to produce a part made from a single piece of brass and free of imperfections. Different methods of brass forging can create just about any type of three-dimesional shape or form, weighing anywhere from a few ounces to several tons. The various types of brass forging include impression or closed die forging, open die forging, cold forging, and seamless rolled ring forging.
The brass forging process actually makes the metal around 15% stronger than mold cast parts as the process does not change the structure of the metal. Extruded brass stock is made into a shape already close to the final part that it will be forged into when the brass is heated. Forging brass parts reduces metal scrap and is faster than machining the parts. The forging process also produces a pore-free surface which makes for a more attractive brass part.
Closed die forging, also known as impression-die forging, utilizes two or more dies made in the shape of the part desired. The brass is heated until it becomes malleable, or reaches a plastic state, and is then compressed by the die machine. Some die machines are capable of creating a compression force of 5,500 pounds (2,500 kg) or more to create forged parts. This forging process creates brass parts that have enhanced density, aligned grain flow, and high strength. In this process, brass parts may also be curved or bent on one or more planes. While more expensive than brass casting methods, closed die brass forging produces extremely strong and durable products.
In open die forging the heated, malleable brass is not confined in a die or mold. Instead, it is accomplished with the use of two flat die surfaces with no type of impression. This type of brass forging is typically used to create and shape very large single pieces of brass up to 80,000 lbs (36,363 kg) or more. This open die process is typically used for lower quantity production runs and custom brass forging on larger parts.
While most forging is done at extremely high temperatures, cold brass forging only requires that the brass be heated to a few hundred degrees. Cold forging is typically used to create things like coins, automotive steering parts, anti-lock braking systems, and other smaller parts that weigh less than 10 lbs (4.5 kg). This process produces parts that require high strength and close tolerances.
Rolled ring forging uses round, open ring-shaped parts that were shaped using the open die forging process. This type of forging is accomplished through the forced pressure of two axial rolls, a driver roll and an idler roll. The ring of brass is rotated by the idler roll while applying pressure to the inside of the ring. The driver roll applies pressure to the outside edge of the ring. As the process progresses, the ring becomes flatter until the desired ring diameter is achieved.