Cold forging is a variation of the forging metal forming process that shapes metal parts through the process of applying strong localized compressive forces. Cold forging is performed while the metal is usually kept at or slightly above room temperature, and the temperature is always kept at or below the recrystallization temperature of the metal being formed. The compressive forces involved in cold forging can be applied manually with a hammer or by a power source, such as a drop forging machine. In most cases, the metal is pressed into the shape of the final product. Cold forging has several distinct advantages over hot forging processes, including better surface finish, improved dimensional stability, and lower production costs.
Forging is one of the oldest metal forming processes known to mankind. The process of forging metal involves striking or hammering the workpiece over or in a die, plate, or fixture to force the metal to flow into the desired shape. Forging is generally divided into three process types based on the temperature to which the metal is heated prior to forging. These are hot metal forging, warm forging, and cold forging, with the hot forging process using workpiece temperatures ranging from a few hundred degrees Fahrenheit to over 2,000 degrees Fahrenheit. Cold forging, on the other hand, finds the work steel heated to no more than one-tenth of its recrystallization temperature.
In many cases, cold forging is performed on steel workpieces at room temperature. This is particularly suitable for making small batches of parts, such as fasteners, including nails, screws, and rivets. The method is attractive as a low-cost forging method because expensive heating equipment is eliminated from the work cycle. These cold forging components can be bent into shape, pressed into an impression die by a manual or powered drop hammer, or drawn into shape by a profiled die.
Another benefit of the cold forging process is the high-quality finish produced on the final product. As with hot working, cold forged parts require little post-forging treatment. However, softer metals, such as aluminum, can undergo secondary heating to temper or harden the material. Cold forging is most often used to produce smaller parts, although the process may be suitable for parts weighing several tons. Other advantages of the process include good dimensional stability and high die loads during the forging process, as well as good stress loading characteristics in the finished product.
