The original definition of forging is the "mechanical deformation of metal when heated to a plastic state". However, in recent years it has come to include similar operations done in the cold or room temperature state as well. There are two types of forgings: open end forging and close end forging.Cold forging is a cold working process where the material is squeezed into a die and the finished parts assume the shape of the die. This process is also known as cold heading. Bar stock or wire stock is fed into a die and is squeezed into the closed die. The resultant part is a nail, a bolt or a screw with the head. A subsequent cold heading operation forms other features on the head such as knurls or slots for screw drivers etc. The shaping rod stock by forming the head as in rivets, bolts, nails and other fasteners. This process can be highly automated and parts can be made economically. Most forging is done as hot work, at temperatures up to 2300 degrees f; however, a variation of impression die forging is cold forging. Cold forging encompasses many processes -- bending, cold drawing, cold heading, coining, extrusions and more, to yield a diverse range of part shapes. The temperature of metals being cold forged may range from room temperature to several hundred degrees. Cold forging encompasses many processes bending, cold drawing, cold heading, coining, extrusion, punching, thread rolling and more to yield a diverse range of part shapes. These include various shaft-like components, cup-shaped geometry's, hollow parts with stems and shafts, all kinds of upset (headed) and bent configurations, as well as combinations. Most recently, parts with radial flow like round configurations with center flanges, rectangular parts, and non-axisymmetric parts with 3- and 6-fold symmetry have been produced by warm extrusion. With cold forging of steel rod, wire, or bar, shaft-like parts with 3-plane bends and headed design features are not uncommon.
Typical parts are most cost-effective in the range of 10 lbs. Or less; symmetrical parts up to 7 lbs. Readily lend themselves to automated processing. Material options range form lower-alloy and carbon steels to 300 and 400 series stainless, selected aluminum alloys, brass and bronze. There are times when warm forging practices are selected over cold forging especially for higher carbon grades of steel or where in-process anneals can be eliminated. Often chosen for integral design features such as built-in flanges and bosses, cold forgings are frequently used in automotive steering and suspension parts, antilock-braking systems, hardware, defense components, and other applications where high strength, close tolerances and volume production make them an economical choice. In the process, a chemically lubricated bar slug is forced into a closed die under extreme pressure. The unheated metal thus flows into the desired shape. As shown, forward extrusion involves steel flow in the direction of the ram force.
