4.2 Open-die Forging

Open-die forging is the simplest forging process. Although most open-die forgings generally weigh 15 kg–500 kg (30 lb–1000 lb), forgings as heavy as 300 tons can be made. Sizes may range from very small parts up to shafts about 23 m long (in the case of ship propellers).

The open-die forging process can be depicted by a solid workpiece placed between two flat dies and reduced in height by compressing it. This process is also called upsetting or flat-die forging.[2] The die surfaces in open-die forging may have simple cavities, to produce relatively simple forgings. Because constancy of volume is maintained, any reduction in height increases the diameter of the forged part.