Unlike most forging, which is performed hot at temperatures nearing or exceeding 2300 degrees F, cold forging is performed at below the re-crystallization temperature of the metal, at anywhere from room temperature to several hundred degrees F.
Cold forging is ideal for the fabrication of many metals including selected aluminum alloys, 300 and 400 series stainless steel, carbon steel, electrolytic copper, brass and bronze.
The metal amounts must be fairly small, rarely exceeding 25 lbs., and the ingot, or semi-finished solid metal form that has been cast into a circular shape must be fairly symmetrical. Industries that use cold forging processes include automotive, mining, oil and petroleum, aerospace, electronics, hardware, appliance, agricultural, construction and industrial.
In the cold forging process an ingot, also known as a slug or billet, is punched through a cold forging die in order to re-form the ingot by means of high pressure rather than high temperatures. The ingot typically requires lubrication in order to be cold forged.
Cold forging is most commonly done using closed die forging. In the closed die or impression forging process metal is pounded or pressed into a desired shape through the use of a press or hammer.
Two tooling dies are attached to an anvil and contain a negative 3-D image of the product’s end shape. The metal undergoes plasticization until its enlarged sides touch the die sidewalls and then flows to take on the shape of the two dies.
Cold forging can have some disadvantages due to requiring high forging pressures, needing several pre-forming steps, and in some cases necessitating several more annealing steps during the process. However, cold forging of a material results in improved material strength because cold forging does not heat stress a material, or change the structure of the material’s grain flow as radically. Cold forging services are very precise and also offer a better surface finish than hot forging.