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There are basically three methods (or processes) to make a forged part. Impression Die Forging Cold Forging Open Die Forging Seamless Rolled Ring Forging Impression Die Forging Impression die forging pounds or presses metal between two dies (called tooling) that contain a precut profile of the desired part. Parts from a few ounces to 60,000 lbs. can be made using this process. Some of the smaller parts are actually forged cold. PROCESS OPERATIONS Graphical depiction of process steps. Still Graphic Animated Sequence Video Process Capabilities Commonly referred to as closed-die forging, impression-die forging of steel, aluminum, titanium and other alloys can produce an almost limitless variety of 3-D shapes that range in weight from mere ounces up to more than 25 tons. Impression-die forgings are routinely produced on hydraulic presses, mechanical presses and hammers, with capacities up to 50,000 tons, 20,000 tons and 50,000 lbs. respectively. As the name implies, two or more dies containing impressions of the part shape are brought together as forging stock undergoes plastic deformation. Because metal flow is restricted by the die contours, this process can yield more complex shapes and closer tolerances than open-die forging processes. Additional flexibility in forming both symmetrical and non- symmetrical shapes comes from various preforming operations (sometimes bending) prior to forging in finisher dies. Part geometry's range from some of the easiest to forge simple spherical shapes, block-like rectangular solids, and disc-like configurations to the most intricate components with thin and long sections that incorporate thin webs and relatively high vertical projections like ribs and bosses. Although many parts are generally symmetrical, others incorporate all sorts of design elements (flanges, protrusions, holes, cavities, pockets, etc.) that combine to make the forging very non-symmetrical. In addition, parts can be bent or curved in one or several planes, whether they are basically longitudinal, equidimensional or flat. Most engineering metals and alloys can be forged via conventional impression-die processes, among them: carbon and alloy steels, tool steels, and stainless, aluminum and copper alloys, and certain titanium alloys. Strain-rate and temperature-sensitive materials (magnesium, highly alloyed nickel-based superalloys, refractory alloys and some titanium alloys) may require more sophisticated forging processes and/or special equipment for forging in impression dies. Back To Top Cold Forging 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. Process Operations Graphical depiction of process steps. Process Capabilities Cold forging encompasses many processes bending, cold drawing, cold heading, coining, extrusion, punching, thread rolling and more to yield a diverse range of part shapes. These include various shaft-like components, cup-shaped geometry's, hollow parts with stems and shafts, all kinds of upset (headed) and bent configurations, as well as combinations. Most recently, parts with radial flow like round configurations with center flanges, rectangular parts, and non-axisymmetric parts with 3- and 6-fold symmetry have been produced by warm extrusion. With cold forging of steel rod, wire, or bar, shaft-like parts with 3-plane bends and headed design features are not uncommon. Typical parts are most cost-effective in the range of 10 lbs. or less; symmetrical parts up to 7 lbs. readily lend themselves to automated processing. Material options range form lower-alloy and carbon steels to 300 and 400 series stainless, selected aluminum alloys, brass and bronze. There are times when warm forging practices are selected over cold forging especially for higher carbon grades of steel or where in-process anneals can be eliminated. Often chosen for integral design features such as built-in flanges and bosses, cold forgings are frequently used in automotive steering and suspension parts, antilock-braking systems, hardware, defense components, and other applications where high strength, close tolerances and volume production make them an economical choice. In the process, a chemically lubricated bar slug is forced into a closed die under extreme pressure. The unheated metal thus flows into the desired shape. As shown, forward extrusion involves steel flow in the direction of the ram force. It is used when the diameter of the bar is to be decreased and the length increased. Backward extrusion, where the metal flows opposite to the ram force, generates hollow parts. In upsetting, the metal flows at right angles to the ram force, increasing diameter and reducing length. Back To Top Open Die Forging Open die forging is performed between flat dies with no precut profiles is the dies. Movement of the work piece is the key to this method. Larger parts over 200,000 lbs. and 80 feet in length can be hammered or pressed into shape this way. PROCESS OPERATIONS Graphical depiction of process steps. Still Graphic Animated Sequence Video Process Capabilities Open-die forging can produce forgings from a few pounds up to more than 150 tons. Called open-die because the metal is not confined laterally by impression dies during forging, this process progressively works the starting stock into the desired shape, most commonly between flat-faced dies. In practice, open-die forging comprises many process variations, permitting an extremely broad range of shapes and sizes to be produced. In fact, when design criteria dictate optimum structural integrity for a huge metal component, the sheer size capability of open-die forging makes it the clear process choice over non-forging alternatives. At the high end of the size range, open-die forgings are limited only by the size of the starting stock, namely, the largest ingot that can be cast. Practically all forgeable ferrous and non-ferrous alloys can be open-die forged, including some exotic materials like age-hardening superalloys and corrosion-resistant refractory alloys. Open-die shape capability is indeed wide in latitude. In addition to round, square, rectangular, hexagonal bars and other basic shapes, open-die processes can produce: Step shafts solid shafts (spindles or rotors) whose diameter increases or decreases (steps down) at multiple locations along the longitudinal axis. Hollows cylindrical in shape, usually with length much greater than the diameter of the part. Length, wall thickness, ID and OD can be varied as needed. Ring-like parts can resemble washers or approach hollow cylinders in shape, depending on the height/wall thickness ratio. Contour-formed metal shells like pressure vessels, which may incorporate extruded nozzles and other design features. Not unlike successive forging operations in a sequence of dies, multiple open-die forging operations can be combined to produce the required shape. At the same time, these forging methods can be tailored to attain the proper amount of total deformation and optimum grain-flow structure, thereby maximizing property enhancement and ultimate performance for a particular application. Forging an integral gear blank and hub, for example, may entail multiple drawing or solid forging operations, then upsetting. Similarly, blanks for rings may be prepared by upsetting an ingot, then piercing the center, prior to forging the ring. Back To Top Seamless Rolled Ring Forging Seamless rolled ring forging is typically performed by punching a hole in a thick, round piece of metal (creating a donut shape), and then rolling and squeezing (or in some cases, pounding) the donut into a thin ring. Ring diameters can be anywhere from a few inches to 30 feet. PROCESS OPERATIONS Graphical depiction of process steps. Still Graphic Animated Sequence Video Process Capabilities Rings forged by the seamless ring rolling process can weigh < 1 lb up to 350,000 lbs., while O.D.`s range from just a few inches up to 30-ft. in diameter. Performance-wise, there is no equal for forged, circular-cross-section rings used in energy generation, mining, aerospace, off-highway equipment and other critical applications. Seamless ring configurations can be flat (like a washer), or feature higher vertical walls (approximating a hollow cylindrical section). Heights of rolled rings range from less than an inch up to more than 9 ft. Depending on the equipment utilized, wall-thickness/height ratios of rings typically range from 1:16 up to 16:1, although greater proportions have been achieved with special processing. In fact, seamless tubes up to 48-in. diameter and over 20-ft long are extruded on 20 to 30,000-ton forging presses. Even though basic shapes with rectangular cross-sections are the norm, rings featuring complex, functional cross- sections can be forged to meet virtually any design requirements. Aptly named, these contoured rolled rings can be produced in thousands of different shapes with contours on the inside and/or outside diameters. A key advantage to contoured rings is a significant reduction in machining operations. Not surprisingly, custom-contoured rings can result in cost-saving part consolidations. Compared to flat-faced seamless rolled rings, maximum dimensions (face heights and O.D.`s) of contoured rolled rings are somewhat lower, but are still very impressive in size. High tangential strength and ductility make forged rings well-suited for torque- and pressure-resistant components, such as gears, engine bearings for aircraft, wheel bearings, couplings, rotor spacers, sealed discs and cases, flanges, pressure vessels and valve bodies. Materials include not only carbon and alloy steels, but also non-ferrous alloys of aluminum, copper and titanium, as well as nickel-base alloys.https://www.forging.org/types-of-forging-processes#2

Forging, a metal shaping technique using compressive, localized forces, has been a staple metal fabrication technique since the time of the ancient Mesopotamians. Since its origins in the fertile crescent, 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. Some of the common materials used for forging are carbon steel, alloy steel, microalloy steel, stainless steel, aluminum, and titanium. A traditional hammer and anvil are used for forging. Image credit: Shutterstock.com/Drpixel What is the purpose of forging? The purpose of forging is to create metal parts. Compared to other manufacturing methods, metal forging produces some of the sturdiest manufactured parts available. As metal is heated and pressed, minor cracks are sealed, and any empty spaces in the metal close. The hot forging process also breaks up impurities in the metal and redistributes such material across the metalwork. This vastly reduces inclusions in the forged part. Inclusions are compound materials implanted inside steel throughout manufacturing that cause stress points in the final forged parts. While impurities should be managed during the initial casting process, forging further refines the metal. Another way that forging strengthens metal is by alternating its grain structure, which is the metal material's grain flow as it deforms. Through forging, a favorable grain structure can be created, making the forged metal sturdier. The forging process is highly multipurpose and can be used on small parts just a few inches in size to large components that weigh up to 700,000 lbs. It is used to produce critical aircraft parts and transportation equipment. Forging is also used to fortify hand tools such as chisels, rivets, screws, and bolts. What are the different types of forging? 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. Hot Forging 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. Need a hot forging company? Thomas' Supplier Discovery has a vetted list of Hot Forging Companies in the U.S. and Canada. Cold Forging 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. Need a cold forging company? Thomas' Supplier Discovery has a vetted list of Cold Forging Companies in the U.S. and Canada. For more detailed info on either of these processes please read our Full Guide to Hot Forging and Cold Forging. Hot forging being used to create automotive parts. Image credit: Shutterstock.com/Aumm graphixphoto What are the different forging processes? Beyond basic hot and cold forging, many specific processes exist. This broad range of processes can be grouped into three primary umbrella groups: Draw forming decreases the width of the product and increases length. Upset forging increases the width of the products and decreases length. Compression forming provides forging flow in multiple or customized directions. These three categories entail many different specific types of metal forging methods. Drop Forging Process Drop forging gets its name from the process of dropping a hammer onto the metal to mold it into the shape of the die. The die is the surface that comes into contact with the metal. There are two types of drop forging: open-die and closed-die forging. Dies are typically flat in shape with some having distinctively shaped surfaces for specialized operations. Open Die Forging Process When flat dies that have no precut profiles engage in forging, the forge process is called open die forging (or smith forging). 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. Open die forging creates pieces with better fatigue resistance and strength and reduces the chance of error or holes. It can also be used for a finer grain size than other processes. Closed Die Forging Process Closed die forging, sometimes called impression die forging, employs the use of molds. These molds are attached to an anvil while a hammer forces molten metal to flow into the cavities of the die. Multiple strikes and/or die cavities are often used when forging complex geometries. 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. Press Forging Process 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 Roll forging is the process of increasing rods or wires in length. The manufacturer places heated metal bars between two cylindrical rolls with grooves, which rotate and apply progressive pressure to shape the metal. The precisely shaped geometry of these grooves forges the metal part to the desired shape. The benefits of this forging method include the elimination of flashing and a favorable grain structure. While roll forging uses rolls to produce parts and components, it is still considered a metal forging process and not a rolling process. Roll forging is frequently used to make parts for the automotive industry. It is also used to forge things like knives and hand tools. Upset Forging Process Upset forging is a forging process that increases the diameter of the metal through compression. Crank presses, a particular high-speed machine, are used in upset forging processes. Crank presses are characteristically set on a horizontal plane to improve efficiency and the quick metal exchange from one station to the next. Vertical crank presses or hydraulic presses are also used. The advantages of this process are that it enables a high production rate of up to 4500 parts per hour and full automation is possible. It also produces little to no waste. Isothermal Forging Process Isothermal forging is a forging process where the materials and the die are heated to the same temperature. The name comes from [iso" which means "equal." This forging method is commonly used for forging aluminium, which has a lower forging temperature than other metals such as steel. Forging temperatures for aluminum are around 430 °C, while steels and super alloys can be 930 to 1,260 °C. The benefits are the near net shapes lead to lower machining requirements and, therefore, lower scrap rates, and the metal part is highly reproducible. Another advantage is that smaller machines can be used to make the forging due to the lower heat loss. A few disadvantages are the higher die material costs to handle temperatures and pressures and the required uniform heating systems. It also has a low production rate. What kind of equipment is used for forging? The most popular type of forging equipment is the hammer and anvil. The idea behind the hammer and anvil is still used today in drop hammer forging equipment. The hammer is raised and then dropped or propelled into the workpiece, which rests on the anvil. The main variations between drop hammers are how the hammer is powered, the most common being air and steam hammers. Drop hammers typically operate in a vertical position. This is because the excess energy that isn't released as heat or sound, meaning energy that isn't used to shape the workpiece, needs to be conveyed to the foundation. A large machine base is also required to absorb the impacts. To overcome some shortcomings of the drop hammer, the counterblow machine or impactor is used. Both the hammer and anvil move in a counterblow machine, with the workpiece held between them. Here, excess energy becomes recoil, allowing the machine to work horizontally and have a smaller base. This creates less noise, heat, and vibration. It also creates a distinctly different flow pattern. These machines are used for open die or closed die forging. A press is used for press forging. The two main types are mechanical and hydraulic presses. Mechanical presses function using cams, cranks, and toggles to make preset and reproducible hammer strikes. Because of the characteristics of this type of system, different forces are available at different stroke positions. As a result, these presses are faster than their hydraulic counterparts by 50 strokes per minute. Their capacities range from three to 160 MN. Hydraulic presses use fluid pressure and a piston to produce force. The advantages of a hydraulic over a mechanical are its flexibility and superior capacity. The disadvantages are that it is a slower, larger, and costlier machine to operate. The roll forging, automatic hot forging, and upsetting processes all use specialized machinery. Summary This guide provides a basic understanding of what forging is and the different forging processes. To find out more about other methods of metal fabrication, read our guide here. For more information on related services consult our other product guides or visit the Thomas Supplier Discovery Platform to locate potential sources or view details on specific products.