Cold Forging
Cold forging, also known as cold heading, is a metal forming process that involves the plastic deformation of metal by squeezing the material through an open die using an unheated billet and causing the finished part to assume the shape of the die. In order to be cold forging the metal must be worked below its recrystallization temperature; which can range from room temperature to several hundred degrees F. However, cold forging temperatures remain well under temperatures nearing 2300 degrees F, which is what most forging is done at. 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 through high pressure rather than high temperatures. The ingot typically requires lubrication in order to be cold forged. Cold forging is most commonly done using impression die forging. In the impression die 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 mirror image profile of the product's end shape are used to form the metal. 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 of a materials results in improved material strength because cold forging does not heat stress a material, or change the structure of the material's grain flow. Cold forging services are very precise and also offer a better surface finish than hot forging. However, cold forging can be disadvantageous due to requiring high forging pressures as well as several pre-forming steps. In addition, several more annealing steps may be required during the process.