Open die forging is the process of deforming a piece of metal between multiple dies that do not completely enclose the material. The metal is altered as the dies “hammer” or “stamp” the material through a series of movements until the desired shape is achieved. Products formed through open forging often need secondary machining and refining to achieve the tolerances required for the finished specifications. Open die forging is widely used for the products in small quantity that are simple, rather than complex, such as discs, rings, sleeves, cylinders and shafts. Custom shapes can also be produced with open die forging. The strength of the grain structure will be increased during the deformation process due to the repeated working of the steel billet. Another benefit of open die forging is that the fatigue resistance and strength of products will be improved. Besides, voids could be effectively reduced after open die forging.Closed die forging (also known as as impression die forging) is a metal forming process that compress a piece of metal under high pressure to fill an enclosed die impression. For some special shapes, second forging operation is required to reach final shapes and dimensions. The type of material, tightness of tolerances, and need for heat treatment can determine the cost of a closed die forged part.