What is Forging?
Forging is the process of heating, deforming and finishing a piece of metal. Forgings are made by forcing materials into customized shapes either by the force of a falling ram upon an anvil or by a die press enclosing a piece of metal and squeeze-forming the part.Due to the realigning of the grains of metal when heated and deformed, forgings can withstand extreme pressure and maintain structural integrity under stress.
Forging has experienced significant changes, resulting in a more efficient, faster and more durable process. This is because today, forging is most commonly performed with the use of forging presses or hammering tools that are powered by electricity, hydraulics or compressed air.Once produced, forgings have a broad range of uses across a variety of industries ranging from heavy trucks, medical supplies, automotive parts, to aerospace. The industries we serve can be found here.
Forging and Their Advantages
Forgings are stronger. Forging surpasses casting in predictable strength properties and produces superior simultaneously more ductile and resistant pieces with uniform quality assured across the production run.Forgings are consistently more reliable and often less costly over time compared to castings. Hot working refines grain patterns and imparts high strength, ductility, and resistance to each forged piece they are also more durable. Forgings also offer better response to heat treatment.Forgings respond more predictably to heat treatment and offer better dimensional stability.Production of forgings allows for flexible, cost-effective adaption to market demand.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. 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. Most forging is done as hot work, at temperatures up to 2300 degrees F, however, a variation of impression die forging is cold forging. Cold forging encompasses many processes — bending, cold drawing, cold heading, coining, extrusions and more, to yield a diverse range of part shapes. The temperature of metals being cold forged may range from room temperature to several hundred degrees.
Metal Forging Process
At its most basic level, forging is the process of forming and shaping metals through the use of hammering, pressing or rolling. The process begins with starting stock, usually a cast ingot (or a “cogged” billet which has already been forged from a cast ingot), which is heated to its plastic deformation temperature, then upset or “kneaded” between dies to the desired shape and size.
Open Die Forging Process
When flat dies that have no precut profiles engage in forging, the process is called open die forging (or smith forging). Open die forging involves the shaping of heated metal parts between a top die attached to a ram and a bottom die attached to a hammer, anvil or bolster. The open design allows the metal to flow everywhere except where it touches the die. To achieve maximum results, correct movement of the workpiece, which should be over 200,000 lbs. in weight and 80 feet long, is essential. It is useful for short-run art smithing or for shaping ingots prior to secondary shaping measures.
Closed Die Forging Process
Closed die forging is also known as impression-die forging. The metal is placed in a die and attached to an anvil. The hammer is dropped onto the metal, causing it to flow and fill the die cavities. The hammer is timed to come into contact with the metal in quick succession on a scale of milliseconds. Excess metal is pushed out from the die cavities, resulting in flash. The flash cools faster than the rest of the material, making it stronger than the metal in the die. After forging, the flash is removed.High initial tooling costs make closed die forging expensive for short-run operations, but the forging process becomes cost-effective as parts produced increases. Closed die forging also provides exceptional strength over alternative methods. Common applications of closed die forging include the production of automobile components and hardware tools.
In press forging, the main forming factor is compression. The metal sits on a stationary die while a compression die applies continuous pressure, achieving the desired shape. The metal’s contact time with the dies is considerably longer than other types of forging, but the forging process benefits from being able to simultaneously deform the entire product, as opposed to a localized section. Another benefit of press forging is the ability of the manufacturer to monitor and control the specific compression rate. Applications of press forging are numerous, as there are relatively no limits to the size of product that can be created. Press forging can be hot or cold forged.
Roll Forging Process
Press forging uses a slow, continuous pressure or force, instead of the impact used in drop-hammer forging. The slower ram travel means that the deformation reaches deeper, so that the entire volume of the metal is uniformly affected. Contrastingly, in drop-hammer forging, the deformation is often only at the surface level while the metal’s interior stays somewhat undeformed. By controlling the compression rate in press forging, the internal strain can also be controlled.