What is Forging?
What is Forging?
Forging is a metallurgical process by which metal is shaped and manufactured using heat and compressive forces. The excessive force by which the metal is hammered means the granular structure of the metal remains intact. Rather than reaching its melting point and potentially reducing its elemental lattice of metallic bonds and positive ions, it is manipulated by condensing those bonds without breaking them. By compacting the structure in this way, the forging process allows the metal to retain its strength, eliminate defects and porosity in the product.
History of Forging
Forging has been a crucial technique of metal manufacturing since the age of the Mesopotamians in the fertile crescent between Tigres and Euphrates. They would use iron and bronze in the forging process to produce tools, weapons, and jewellery; however, the first recorded metal forged was gold. The metal was heated in fire, and a rock was used as a forging hammer.
Through the development of wrought iron forging came the forge-smiths in the 19th century, and by the time of the industrial revolution, the forging industry had developed more efficient methods of processes, machinery, and materials, allowing it to be more efficient and durable. Now, with forging presses and hammering tools powered mostly by electricity, compressed air and hydraulics, the forging industry remains one of the most innovative and significant developments in humanity.
Types of Forging
There are two main types of forging – hot and cold.
Hot forging requires the metal to be heated above its recrystallisation temperature. As forging is the process of manipulating metal rather than melting it, this process requires applying a specific heat to maintain the metallic bonds. One of the benefits of hot forging is the reduction in energy required to shape the metal, as excessive heat decreases strength and improves malleability. Another benefit is the elimination of chemical inconsistencies.
Cold forging refers to a process of forging at room temperature. This process is limited in its materials due to the fact that many metals simply can’t be ductile unless it is heated above the recrystallisation temperature. However, with metals that can undergo this process, cold forging benefits include an increase in dimensional control, surface finish, uniformity and consistency. Cold forging consists of many techniques such as bending, extruding, cold heading, but overall requires more power and higher operational demands.
Many specific forging processes exist beyond the categorisation of the hot and cold method. This can be divided into three main groups:
Draw forging: Draw forging is the process of pulling and manipulating a metal by stretching the initial shape until the desired width and length is produced.
Upset forging: Upset forging is the process of deforming metal under great pressure
Compression forging: Compression forging is the process of constant pressure applied to a material.
These three processes can then be subdivided into many different specific types of forging:
Open die forging:
Open die forging consists of flat dies that have no precut profiles. The open design allows the metal to flow freely around the section in which the die touches. It is useful for products that are short-run and for ingots that will require multiple shaping methods.
Closed die forging is also known as impression die forging and employs the use of moulds that attach to anvils while a hammer forces molten metal to flow into the cavities of the die, leaving a predetermined shape to take form. Complex geometries often require multiple strikes or die moulds. Specifications for tools can be costly for short-run projects and products; however, they can prove to be beneficial for manufacturers and those requiring ongoing production. It also allows malleable control over the metals better than most other methods, allowing a shape to be formed with incredible precision.
Press forging requires compression in order to manipulate shape and size. The metal sits on a die while a second die is lowered, causing the metal to compress. The contact with the die is substantially longer than other processes of forming, but this process is beneficial as it can simultaneously deform an entire product rather than a section. Another benefit is the capacity to monitor and control the compression rate.
Roll forging is used for increasing rods or wires in length. As the name suggests, the metal is placed between two cylindrical rolls and rotated with a specific application of pressure to shape the metal and roll it to the desired length. The main benefit of roll forging is increasing the overall grain structure and eliminate the process of flashing.
At Greg Sewell Forging, we have over 40 years’ experience working with forged metals, and our team of engineers and manufacturers are constantly working to improve and manufacture the highest quality forged products such as forged eyebolts, eyenuts, and other forged fittings. Greg Sewell has the greatest production capacity of any steel forge plant in the southern hemisphere.