Metal Forging

Process Definition & Working Principle

Metal forging is one of the oldest and most advanced manufacturing processes for plastic deformation, where a starting metal billet is permanently shaped through localized compressive forces applied by hammers, presses, or specialized forging machines. The process is executed entirely in the solid state of the material, fundamentally distinguishing it from casting.

Physical and Metallurgical Principles

The application of external compressive stress ($\sigma$) exceeds the flow stress (${\sigma }_f$) or yield strength of the material, initiating dislocation slip along crystallographic planes and resulting in permanent plastic deformation.

The defining metallurgical advantage of forging is grain flow refinement. During forging, the pre-existing grain boundaries and non-metallic inclusions are elongated and aligned in the direction of plastic flow, creating continuous "grain flow lines" (fibers). This engineered microstructure orientation yields:

Kinematics, Axes, & Machine Configuration

Forging machinery is classified based on energy, force, or stroke limitations into two main categories: energy-restricted machines (forging hammers) and force- or stroke-restricted machines (forging presses).

Forging Hammers

Hammers are energy-restricted machines where deformation is accomplished via rapid impact, converting the kinetic energy of the falling ram into workpiece deformation.