Hot Forging Metal Shaping Process

Hot forging can be defined as “a metal shaping process in which a malleable metal part, known as a billet or workpiece, is worked to a predetermined shape by one or more processes such as hammering, upsetting, pressing and so forth where the workpiece is heated up to about 75% of its melting temperature”.

The process begins with a cast ingot, which is heated to its plastic deformation temperature, then forged between dies to the desired shape and size. During this forging process, the cast, coarse-grain structure is broken up and replaced by finer grains, achieved through the size reduction of the ingot. Usually, the product is additionally heat treated after it is hot forged. Figure 1 shows schematically the hot forging process of cast ingot.

Hot forging results in metal that is stronger than cast or machined metal parts. Thus, hot forging technology has a special place in producing parts of superior mechanical properties with minimum waste of material.

Furthermore, as the temperature of the workpiece prior to forging approaches the melting temperature, the flow stress and energy required to form the material are decreased. Therefore, the strain rate or production rate can be increased.

Therefore, many hard metals with properties of cold-working hardening or that can be strengthened by heat treatment are forged hot, such as iron and its alloys. Alloys that are amenable to precipitation hardening, such as most of titanium alloys, can also be hot forged and then hardened.