The pounding action of forging deforms and shapes the metal, which results in unbroken grain flow. This causes the metal to retain its strength. Ancillary effects of this unique grain flow include the elimination of defects, inclusions, and porosity in the product. Another advantage of forging is the relatively low costs associated with moderate and long production runs. Once the forging tools have been created, products can be manufactured at relatively high speeds with minimal downtime.There are two main types of forging: hot and cold.
Types of Forging Processes
Hot forging requires the metal to be heated above its recrystallization temperature. This can mean heating metals up to 2,300 degrees Fahrenheit. The main benefit of hot forging is the decrease in energy required to form the metal properly. This is because excessive heat decreases yield strength and improves ductility. Hot forged products also benefit from the elimination of chemical inconsistencies.
Cold forging typically refers to forging a metal at room temperature, though any temperature below recrystallization is possible. Many metals, such as steel high in carbon, are simply too strong for cold forging. Despite this hindrance, cold forging does edge out its warmer equivalent when it comes to standards of dimensional control, product uniformity, surface finish, and contamination. Cold forging encompasses numerous forging techniques, including bending, extruding, cold drawing, coining, and cold heading. However, this increased versatility comes at a cost, because cold forging requires more powerful equipment and may call for the use of intermediate anneals..