Cold forging is one variation of the forging metal-shaping process that involves forming or shaping metal parts through a process of applying powerful, localized compressive forces. Cold forging is carried out with the metal generally kept at or slightly above room temperature with the temperature always maintained at or below three-tenths of the recrystallization temperature of the metal being shaped. The compressive forces involved in cold forging may be applied by hand with a hammer or by powered sources, such as drop forge machines. In most cases, the metal is forced into a die in the shape of the finished product or around open templates or jigs. Cold forging offers several distinct benefits over hot forging processes, which include better surface finish, improved dimensional stability, and lower production costs.
Forging is one of the oldest metal shaping processes known to man. The process of forging metal involves beating or hammering a workpiece over or into a die, template, or jig, forcing the metal to flow into the desired shape. Forging is generally divided into three process types based on the temperatures to which the metal is heated prior to forging. These are hot, warm, and cold forging, with hot and warm processes employing workpiece temperatures ranging from several hundred degrees to over 2,000° Fahrenheit. Cold forging, on the other hand, sees the working steel heated to no more than three-tenths of its recrystallization temperature.
In many cases, cold forging is carried out with the steel workpiece at room temperature. This is particularly suitable to the manufacture of small, high-volume pieces such as fasteners, including nails, screws, and rivets. The process is thus attractive as a low-cost forging method as expensive heating equipment is eliminated from the work cycle. Cold-forged steel parts may be bent into shape, forced into impression dies by manual or powered drop hammers, or drawn into shape through a profiled die.
Another benefit of the cold forging process is the high-quality finish produced on the end products. Cold forged parts require very little post-forging treatment as is the case with hot processes. Softer metals such as aluminum may, however, undergo secondary heating to temper or harden the material. Cold forging is most commonly used to produce smaller items, although the process may be applied to parts weighing several tonnes. Other benefits of the process include excellent dimensional stability with high die loads during forging and good stress loading characteristics in the finished product.