Editing Forging (section)

===Automatic hot forging===
The automatic hot forging process involves feeding mill-length steel bars (typically {{convert|7|m|0|abbr=on}} long) into one end of the machine at room temperature and hot forged products emerge from the other end. This all occurs rapidly; small parts can be made at a rate of 180 parts per minute (ppm) and larger can be made at a rate of 90 ppm. The parts can be solid or hollow, round or symmetrical, up to {{convert|6|kg|lb|abbr=on}}, and up to {{convert|18|cm|in|abbr=on}} in diameter. The main advantages to this process are its high output rate and ability to accept low-cost materials. Little labor is required to operate the machinery.

There is no flash produced so material savings are between 20 and 30% over conventional forging. The final product is a consistent {{convert|1050|°C|°F|abbr=on}} so air cooling will result in a part that is still easily machinable (the advantage being the lack of [[annealing (metallurgy)|annealing]] required after forging). Tolerances are usually ±{{convert|0.3|mm|in|abbr=on}}, surfaces are clean, and draft angles are 0.5 to 1°. Tool life is nearly double that of conventional forging because contact times are on the order of 0.06-second. The downside is that this process is only feasible on smaller symmetric parts and cost; the initial investment can be over $10 million, so large quantities are required to justify this process.<ref>Degarmo, pp. 396–397</ref>

The process starts by heating the bar to {{convert|1200|to|1300|C|F}} in less than 60 seconds using high-power induction coils. It is then descaled with rollers, sheared into blanks, and transferred through several successive forming stages, during which it is upset, preformed, final forged, and pierced (if necessary). This process can also be coupled with high-speed cold-forming operations. Generally, the cold forming operation will do the finishing stage so that the advantages of cold-working can be obtained, while maintaining the high speed of automatic hot forging.<ref>Degarmo, p. 396</ref>

Examples of parts made by this process are: wheel hub unit bearings, transmission gears, tapered roller bearing races, stainless steel coupling flanges, and neck rings for liquid propane (LP) gas cylinders.<ref>[http://www.samtech.co.jp/e/precision_hot/index.html Precision Hot Forging] {{Webarchive|url=https://web.archive.org/web/20081020051411/http://www.samtech.co.jp/e/precision_hot/index.html |date=2008-10-20 }}. Samtech. Retrieved 22 November 2007</ref> Manual transmission gears are an example of automatic hot forging used in conjunction with cold working.<ref>[http://www.samtech.co.jp/e/precision_composite/index.html Precision Composite Forging] {{Webarchive|url=https://web.archive.org/web/20080417020414/http://www.samtech.co.jp/e/precision_composite/index.html |date=2008-04-17 }}. Samtech. Retrieved 22 November 2007</ref>