Forgings

About Forgings and Cold Forging Including: Alloy Forgings, Aluminum Forgings, Brass Forgings, Carbon Steel Forgings, Copper Forgings, Nickel Forgings, Stainless Steel Forgings & Titanium Forgings.

Forgings and aluminum forgings are manufactured through a metal forming process that involves the plastic deformation of metal under pressure and high temperatures through hammering and rolling. For work with high temperatures, high loads and increased stress applications, forging is an ideal method to use. Unlike casting, the metal is preheated prior to the forging process, but not to the point of melting. Common forging processes utilize a press containing one or more dies. Closed-die, or impression-die, forging involves the movement of metal blanks through a set of dies shaped in the required part design. Closed-die forging is the most common method of forging utilized in the industry and is done by two dies coming completely together. When the dies are brought closer together, plastic deformation of the workpiece takes place. It is during this process that flash is formed, which is created when the molten metal from the workpiece flows outside the die impression. Once this flash cools, it creates resistance to deformation in the workpiece, thus strengthening the final product. The final product often requires very little tooling to be done.

Open-die forging, also known as hand forging, involves the use of flat dies with little shape. This method creates parts by the manipulation of the metal through the die into the required shape. The workpiece is manipulated so that all aspects of the piece are able to be forged at some point during the process. This process allows for larger products to be forged, and can offer a wider variety of mechanical products than closed-die or other types of forging. Another forging process is called ring rolling. This process involves heating a metal to the proper temperature, then placing it into a rolling machine. The pressure from the walls of the machine begins to shape the metal into a cylindrical or ring shape. This process, like open-die, allows a variety of shapes and sizes to be formed. Other forging processes include hammer forging and cold forging. Although most forging is done at temperatures up to 2300 degrees F, the cold forging process causes less stress on the metal itself than heat-based forging processes, which tend to compromise the strength and consistency of the metal. Cold forging processes include bending, cold drawing, cold heading, coining and extrusions. The temperature of cold forging may range from room temperature to several hundred degrees.

After the forging process, there are many subsequent metalworking techniques that enhance the function and durability of the forgings. The main one is trimming, removing excess flash for the proper shipping and/or operation of the forged part. Another post-forging procedure is coining, which is essentially a sizing operation in which the application of pressure is used to improve tolerances and smooth critical surfaces. Coining is usually done on surfaces parallel to the parting line, and little metal flow is involved in the operation. Swaging is done exclusively in conjunction with the open-die process. This operation creates a tapering of the workpiece via the use of a rotating hammer, which produces stepped columns and shafts of declining diameter. Many post-forging processes are done by the manufacturers and shops that produce forgings.

Forging produces a great many industrial components, such as blanks, bars, hubs, spindles, shafts, rings and piping parts. Aluminum forgings are one of the most popular types of product made through this process, although various metal materials can be used, including copper, brass, stainless steel and titanium. Forged parts are used in a variety of industries, including mining, construction, aerospace, defense, forestry, oil/gas and automotive/trucking. Forging provides an economical alternative to casting, welding and fabrication. Forgings are strong, offer great design flexibility, require few secondary operations, produce broad part size range and usually have few defects. Due to the lack of internal gas pockets in forged products and materials, there is very little unexpected failure, which allows forging to remain one of the safest, most economical and fastest producing forms of metalworking.

	Forgings and Cold Forging Images Provided by Clifford-Jacobs Forging Company

Forgings and Cold Forging Images Provided by Weldaloy Products Company

Types of Forgings

• Alloy steel forgings contain steel and alloys, such as nickel, to produce desired properties. These steel alloys do not contain carbon.
  
• Aluminum forgings are easy to forge, possess a smooth appearance, good fracture resistance and great electrical conductivity and are economical.
  
• Axisymmetric forging uses a metal flow moving in a direction away from a common axis in a radial direction during deformation.
  
• Brass forgings are common in the hardware industry, producing useful and decorative parts, such as valves, doorknobs and handles.
  
• Carbon steel forgings are cost-effective, easy to manufacture and effective in temperatures up to 900°F (482ºC).
  
• Closed die forging is the shaping of hot metal completely within the walls or cavities of two dies that come together and enclose the workpiece on all sides.
  
• Cold forgings are produced at temperatures ranging from room temperature to a few hundred degrees. Consisting of alloys of steel and aluminum, among others, cold forgings are common in the production of industrial parts that have intricate features, such as suspension components and steering parts in automotive equipment.
  
• Copper forgings, such as automotive forgings and electrical fittings, are used in the semiconductor process equipment, material processing and hydro-dynamic bearings market segments because of their high corrosion resistance and good conductive properties.
  
• Counterblow forging is a process in which a press containing two opposing rams hits a blank at the same time.
  
• Cross forging works forging stock in alternate planes, usually on flat dies, to develop mechanical properties.
  
• Double forgings are designed to be cut apart and used as two separate pieces.
  
• Drop forgings are made in closed or impression dies under a drop or steam hammer.
  
• Hammer forging is a process in which a ram strikes a workpiece on an anvil.
  
• Hot-die forging is a process in which dies are heated close to the forging temperature of the alloy being forged; used for difficult-to-forge alloys.
  
• Impression die forgings are formed to the specific shape and size by machined impressions in specially prepared dies that exert three-dimensional control on the workpiece.
  
• Machine forging (upsetter forging) is the process of forging in a machine (upsetter), in which metal is moved into the die impression by pressure applied in a horizontal direction by the moving die in the ram.
  
• Magnesium forgings have a lower density than other metals. Magnesium forgings can also withstand operational temperatures up to 500°F (280ºC).
  
• Mandrel forging is the process of forging and rolling a hollow blank over a mandrel in order to produce a weldless, seamless ring or tube.
  
• Nickel alloy forgings are resistant to oxidation and can withstand temperatures up to 1800°F (982ºC).
  
• Open die forgings are forgings produced by working between flat or simply contoured dies with unrestricted metal flow using repetitive strokes and continuous manipulation of the workpiece; sometimes called hand forging.
  
• Precision forging is a forging produced to closer tolerances than normally considered standard by the industry.
  
• Rolled ring forging involves the creation of rings in which a doughnut hole is punched into a round metal blank. The ring is then thinned out through rolling and stretching operations.
  
• Stainless steel forgings contain 10-12% chromium and provide great corrosion resistance to a variety of structures, such as pressure vessels, turbines and boilers, in temperatures ranging up to 1800°F (982ºC) or higher.
  
• Titanium forgings produce strong, low-density parts similar to steel, but lighter. Titanium is particularly useful in the construction of parts in the aerospace industry.
  
• Upset forging is a process in which the metal is gathered at the middle or one or both ends, producing plastic deformation of the metal.

Common Terms Related to Forgings

As forged - The condition of a forging as it comes out of the finisher cavity without any added operations.

Backward Extrusion – A process in which the metal flows in the opposing direction of the die and punch.

Bar – A metal piece that is hot rolled from a billet to form a round, hexagonal, square or rectangular shape.

Bend – Lengthwise deformation that occurs during forging or secondary operations, such as trimming.

Billet – A semi-finished, usually hot-rolled, uniform section metal product. Billets are relatively larger than bars for the most part.

Block - The forging operation in which metal is progressively formed to general desired shape and contour by means of an impression die.

Bloom – A semi-finished product of square or round cross section. This term is sometimes used interchangeably with "billet."”

Board Hammer – A type of gravity drop hammer in which wood boards attached to the ram are raised vertically by action of contra-rotating rolls, then released. Forging energy is produced by the mass and velocity from the freely falling ram and the attached upper die.

Cavity – The recess in a die that gives shape to the forging. Cavities are typically created by machining.

Coining – A sizing process in which pressure is applied to forged parts to smooth part surfaces and fix deformations.

Cold Working – Changing properties, such as size, shape and strength of an alloy, through plastic deformation of the metal at low to moderate temperatures below the recrystallization point of the metal.

Die – Part of press that punches shaped holes in, cuts or forms sheet metal.

Discontinuities – External and internal imperfections of a forging. External discontinuities include cracks, folds and laps; internal discontinuities include porous and segregated deformations.

Drifting – The formation of a hole or the enlargement of an existing hole in a forging through punching.

Efficiency – The amount of applied energy that is utilized in the deforming of the workpiece, expressed as a percentage of the total energy expended by the forging equipment.

Extrusion – The process of forcing metal to flow through a die opening in the same direction in which energy is being applied. Extrusion is used in many die-forging applications.

Flash – Excess metal that extends past the parting line of the die set, blocking metal from flowing past the die lines and filling the die impressions.

Flow Stress – The measurement of the deformation resistance of a substance dependent on such factors as temperature.

Ram – The mechanism on a press to which the punch is fastened and that forces the punch through the die.

Trimming – Secondary operation in which a forging is cut down to desired shape and size by removing flash from the forging.

Twist – Forging deformation that occurs along the width of the forging.