Forging is the process of forming and shaping metals through the use of hammering, rolling or pressing. The process usually begins with starting stock, a cast ingot or a cogged billet which has already been forged from a cast ingot; this will be heated to its plastic deformation temperature, then upset or kneaded between dies to the shape or size required. It has been a staple metal fabrication technique since the time of ancient Mesopotamians.
Since its origins in the Fertile Crescent, forging has experienced significant changes resulting nowadays in a faster and more efficient process. This is mainly because forging is most commonly performed with the use of forging presses or hammering tools that can be powered by electricity, compressed air or hydraulics.
The pounding action of forging deforms and shapes the metal, these result in an unbroken grain flow, this causes the metal to retain its strength. Effects of this unique grain flow include the elimination of defects and inclusions and porosity in the product. Another advantage of forging is it is a relatively low cost especially with moderate and long runs. There are several forging processes available , including impression or closed die, cold forging, drop forging, forging, upset forging and open die forgings.
The two main types of forging are hot and cold: Hot forging requires the metal to be heated above its recrystallization temperature, the metal can be heated up to 2,300 degrees Fahrenheit. Hot forging’s benefit is the decrease in energy required to form the metal properly, excessive heat decreases yield strength and improves ductility. Products that have been hot forged also benefit from the elimination of chemical inconsistencies.
The other main type of forging is cold forging, many metals such as steel high in carbon are simply too strong for cold forging. Cold forging comes at a cost because cold forging requires more powerful equipment. Cold forging typically refers to forging metal at room temperature.