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In the forging process, metal is shaped by pressing, pounding, or squeezing under very high pressure to form parts called forgings. Almost any metal can be forged, including carbon, alloy and stainless steel, aluminum, titanium, brass, copper, and others. The metal is preheated prior to the forging services process, but not melted, as in the casting process. There are several different types of forging processes, including cold forging or heading, impression die (closed die) forging, open die forging, and seamless rolled ring forging. The types of forging services selected are determined by the shape, size and material of the metal to be forged and the end product. In cold forging, the metal being processed is not directly heated. Instead, it is molded under extreme pressure. This process makes products that are precisely sized to final shape. It is often used to create small components like fasteners. While the forces required to mold the metals are extreme, the overall energy needed to forge items using this process is rather small, as no heating is required. Items prepared through this process are generally strong, as heating has not weakened the strength and consistency of the metal.
Impression die forging is the most commonly used of the forging services. In impression die forging, a metal workpiece is placed between two dies. As the dies are brought closer together, the workpiece undergoes plastic deformation until its enlarged sides touch the die sidewalls. During the process, flash is formed, as some of the molten metal from the workpiece flows outside the die impression. As the flash cools, it imparts deformation resistance to the workpiece, strengthening the final product. This builds pressure inside the bulk of the workpiece, aiding material flow into unfilled impressions.
In open die forging, the dies do not completely cover the workpiece. Instead, there are open spaces that allow various aspects of the workpiece to move from direct hot die contact, and to cooler open areas. During open die forging services the metal workpieces are heated to above their recrystallization temperatures, and the working process begins. Throughout the process, the workpiece is moved so that all aspects of the workpiece may be forged. As the workpiece is moved and repositioned, aspects that are in the open area cool to below the metals recrystallization point, which must then be reheated as forging continues.
Ring rolling involves heating a metal perform to forging temperature. The preform is then placed into an internal rolling machine. As pressure is applied by the walls of the rolling machine, the preform begins to take on a cylindrical, or ring, shape. As the inner and outer dimensions are expanded within these forging services, the cross-sectional area is reduced.
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