Forged steels are steels obtained through the forging process, an industrial transformation process consisting in plastic deformation of metals, usually bringing them to a high temperature (higher than recrystallization), to obtain semi-finished or finished pieces (forgings), starting from ingots, blocks, etc. which are subjected to repeated blows or compression either in special machines (hammers, presses) or manually, by anvil and mallet, which permanently change the piece shape, without leading it to breakage and bringing it to a more plastic condition (effect given by temperature).
The main characteristics of forged steels
This method generates a number of properties in steel that distinguish it from other metal treatments, i.e., casting, where liquid metal is poured into a mold and then allowed to solidify.
In particular, forged steel gain the following characteristic:
– Strong and Durable:
Generally, steel forgings have a higher fatigue strength. This is because hot plastic deformation improves the material’s mechanical properties, such as unit tensile and yield strength, resilience and wear resistance; in addition, internal defects such as cavities and blowholes, commonly found in the early-stage blanks, are easily eliminated and variations in homogeneity are alleviated or eliminated; segregations and non-metallic inclusions are aligned along the material’s flow directions, generating the typical forging fibers.
Forged steels are anisotropic, meaning that when metal is processes and deformation occurs, the strength of the steel is greater in the direction of the resulting grain flow. This leads to the creation of forged steels that are stronger along their longitudinal axis, and weaker in other directions. They differ from casting steels, which are isotropic and therefore have almost identical properties in all directions.
– Size limitation:
During the forging process, it’s harder to shape the metal it being still in a solid state, unlike casting where the metal has been reduced to its liquid form, as part of the process. The larger the section of metal being worked on, the more difficult the forging will be, therefore there is a limit to the size and thickness of steel that can be successfully forged.
The forging technique is therefore suitable for irregularly shaped parts, such as crankshafts, connecting rods, hooks, gears, rings, anchors, etc., and for regular parts made out of special steels, such as bars intended for the manufacture of special tools, or steels for magnetic, electrical, etc. uses.