6732653-Forging

7/30/2019 6732653-Forging

1/38

Forging History and Key Developments in the Metals Forging IndustryTopics CoveredOrigins of the Forging Process

Forging Through the 19th Century

Steel Making Developments That Aided the Forging Industry

Invention of the Forging Press

Modern Computer Controlled Forging MachinesOrigins of the Forging Process

The art of forging dates to at least 4000BC and probably earlier. Metals such as bronze

and wrought iron were forged by early man to produce hand toots and weapons of war.

Forging of wrought iron and crucible steel continued until near the end of the 19th

century for similar purposes and it is unfortunate that weapons of war are still produced

by the forging process using more contemporary metals.

Forging Through the 19th Century

The forgesmiths of the 19th century were particularly skilled at hand and open die

forging of wrought iron. As wrought iron was only produced in heats of 50 kilograms,

the smiths became skillful in hammer welding and many large shaft forgings weighing

10 tonnes and more were gradually built up by a process of forging and hammer

welding. The invention of the Bessemer steel making process in 1856 was a major

breakthrough for the ferrous forging industry. The forgers now had a plentiful supply of

low cost steel for production of volume quantities of forgings. It has been accepted that

the first cavity steel forgings using a closed die process commenced in the United States

in 1862 for production of components for the Colt revolver.

Steel Making Developments That Aided the Forging Industry

The further development of the Bessemer process with the invention of the basic steel

making technique meant that cheaper supplies of iron ore containing high phosphorus

and sulphur levels could be smelted to produce good quality steel.

The simultaneous development of the open hearth steel making process toward the end

of the 19th century meant that the forging industry now had a reliable, low cost, high

volume raw material.

Invention of the Forging Press

With the introduction of motor vehicles and in particular Henry Fords T Model a

considerable demand for forgings developed in the early years of the 20th century. Up

until 1930, when National Machinery Company of the USA introduced the first forging

press (Maxipress), all forgings were produced on hammers. The advantage of the

forging press was exemplified by higher production rates and a lesser degree of skill in

producing forgings as compared to hammer forging.

The introduction of the forging press did not obsolete the forging hammer but rather

challenged the manufacturers to improve their product and of course, there are many
http://www.azom.com/details.asp?ArticleID=2195#_Origins_of_the#_Origins_of_thehttp://www.azom.com/details.asp?ArticleID=2195#_Forging_Through_the#_Forging_Through_thehttp://www.azom.com/details.asp?ArticleID=2195#_Steel_Making_Developments#_Steel_Making_Developmentshttp://www.azom.com/details.asp?ArticleID=2195#_Invention_of_the#_Invention_of_thehttp://www.azom.com/details.asp?ArticleID=2195#_Modern_Computer_Controlled#_Modern_Computer_Controlledhttp://www.azom.com/details.asp?ArticleID=2195#_Origins_of_the#_Origins_of_thehttp://www.azom.com/details.asp?ArticleID=2195#_Forging_Through_the#_Forging_Through_thehttp://www.azom.com/details.asp?ArticleID=2195#_Steel_Making_Developments#_Steel_Making_Developmentshttp://www.azom.com/details.asp?ArticleID=2195#_Invention_of_the#_Invention_of_thehttp://www.azom.com/details.asp?ArticleID=2195#_Modern_Computer_Controlled#_Modern_Computer_Controlled

7/30/2019 6732653-Forging

2/38

forgings which are best made on hammers.

Modern Computer Controlled Forging Machines

Today we have computer controlled hammers and presses capable of making a widerange of components in a variety of materials for many applications including

aerospace, automobile, mining and agriculture, to mention a few.

What are the types of forging processes?

There are basically three methods (or processes) to make a forged part.

1. Impression Die Forging2. Cold Forging

3. Open Die Forging

4. Seamless Rolled Ring Forging

Impression Die Forging

Impression die forgingpounds or presses metal between two dies (called tooling) that contain aprecut profile of the desired part. Parts from a few ounces to 60,000 lbs. can be made using thisprocess. Some of the smaller parts are actually forged cold.

PROCESS OPERATIONSGraphical depiction of process steps

Impression Die Forging Process Operations

In the simplest example of impression die forging, two dies are brought together and theworkpiece undergoes plastic deformation until its enlarged sides touch the side walls of the die.Then, a small amount of material begins to flow outside the die impression forming flash that isgradually thinned. The flash cools rapidly and presents increased resistance to deformation andhelps build up pressure increased resistance to deformation and helps build up pressure insidethe bulk of the workpiece that aids material flow into unfilled impressions.

Upsetting
http://www.forging.org/facts/faq9.htm#1#1http://www.forging.org/facts/faq9.htm#2#2http://www.forging.org/facts/faq9.htm#3#3http://www.forging.org/facts/faq9.htm#4#4http://www.forging.org/facts/faq9.htm#1#1http://www.forging.org/facts/faq9.htm#2#2http://www.forging.org/facts/faq9.htm#3#3http://www.forging.org/facts/faq9.htm#4#4

7/30/2019 6732653-Forging

3/38

Fundamentally, impression die forgings produced on horizontal forging machines (upsetters) aresimilar to those produced by hammers or presses. Each is the result of forcing metal intocavities in dies which separate at parting lines.

Trastornando

Fundamentalmente, las forjas por impresin producidas sobre mquinas de forja

(prensas) horizontales son similares a aquellos producidos por martillos o prensas. Cada

uno es el resultado de forzar el metal en cavidades en muere que se separan en lneas

que se separan.

The impression in the ram-operated "heading tool" is the equivalent of a hammer or press topdie. The "grip dies" contain the impressions corresponding to the hammer or press bottom die.Grip dies consist of a stationary die and a moving die which, when closed, act to grip the stockand hold it in position for forging. After each workstroke of the machine, these dies permit thetransfer of stock from one cavity to another in the multiple-impression dies.

La impresin en el manejado por carnero " el instrumento de ttulo " es el equivalente deun martillo o la cima de prensa muere. " El apretn muere " contienen las impresiones

correspondiente al martillo o la prensa inferior muere. El apretn muere consisten en un

inmvil mueren y un movimiento muere que, cuando cerrado, el acto para agarrar la

accin(reserva) y lo sostiene en la posicin para la forja(falsificacin). Despus de cada

workstroke de la mquina, estos mueren el permiso la transferencia de accin(reserva)

de una cavidad al otro en la impresin mltiple muere.

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 frommere ounces up to more than 25 tons. Impression-die forgings are routinely produced onhydraulic presses, mechanical presses and hammers, with capacities up to 50,000 tons, 20,000tons and 50,000 lbs. respectively.

As the name implies, two or more dies containing impressions of the part shape are broughttogether as forging stock undergoes plastic deformation. Because metal flow is restricted by thedie contours, this process can yield more complex shapes and closer tolerances than open-dieforging processes. Additional flexibility in forming both symmetrical and non- symmetricalshapes comes from various preforming operations (sometimes bending) prior to forging infinisher dies.

Part geometry's range from some of the easiest to forge simple spherical shapes, block-likerectangular solids, and disc-like configurations to the most intricate components with thin andlong sections that incorporate thin webs and relatively high vertical projections like ribs and

7/30/2019 6732653-Forging

4/38

bosses. Although many parts are generally symmetrical, others incorporate all sorts of designelements (flanges, protrusions, holes, cavities, pockets, etc.) that combine to make the forgingvery non-symmetrical. In addition, parts can be bent or curved in one or several planes, whetherthey 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, highlyalloyed nickel-based superalloys, refractory alloys and some titanium alloys) may require moresophisticated forging processes and/or special equipment for forging in impression dies.

Cold Forging

Most forging is done as hot work, at temperatures up to 2300 degrees F, however, a variation ofimpression 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 partshapes. The temperature of metals being cold forged may range from room temperature toseveral hundred degrees.

.

Cold ForgingProcess Operations

1. Forward extrusionreduces slug diameterand increases its lengthto produce parts suchas stepped shafts andcylinders.

7/30/2019 6732653-Forging

5/38

2. In backwardextrusion, the steel

flows back and aroundthe descending punchto form cup-shapedpieces.

3. Upsetting, orheading, a commontechnique for makingfasteners, gathers steelin the head and other

sections along thelength of the part.

El trastornar, o el dirigir, una tcnica comn para hacer los

sujetadores, frunces de acero en la cabeza y otras secciones a lo

largo de la longitud de la pieza


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. Theseinclude 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, rectangularparts, and non-axisymmetric parts with 3- and 6-fold symmetry have been produced by warmextrusion. With cold forging of steel rod, wire, or bar, shaft-like parts with 3-plane bends andheaded design features are not uncommon.

Mas recientemente, las partes con flujo radial como configuraciones redondas con rebordes de centro,partes rectangulares, y partes de non-axisymmetric con 3-y la simetra de 6 pliegues han sido producidaspor extrusion en caliente. Con la forja(falsificacin) de fro de barra de acero, el cable, o la barra, partesparecidas a un eje con curvas de 3 planos y rasgos de diseo encabezados no son raras.

Typical parts are most cost-effective in the range of 10 lbs. or less; symmetrical parts up to 7lbs. 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 forhigher 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 arefrequently used in automotive steering and suspension parts, antilock-braking systems,hardware, defense components, and other applications where high strength, close tolerancesand volume production make them an economical choice.

In the process, a chemically lubricated bar slug is forced into a closed die under extremepressure. 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 tobe decreased and the length increased. Backward extrusion, where the metal flows opposite to

7/30/2019 6732653-Forging

6/38

the ram force, generates hollow parts. In upsetting, the metal flows at right angles to the ramforce, increasing diameter and reducing length.

Open Die Forging

Open die forgingis 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 lengthcan be hammered or pressed into shape this way.

PROCESS OPERATIONSGraphical depiction of process steps.

7/30/2019 6732653-Forging

7/38

SHAFTS

1. Starting stock,

held by

manipulator.

2. Open-die

forging.

3. Progressive forging. 4. Lathe turning to

near net-shape.

DISCS

1. Starting stock. 2. Preliminaryupsetting.

3. Progressiveupsetting/forging to discdimensions.

4. Pierced forsaddle/mandrelring hollow"sleeve type"

preform.

SADDLE/MANDREL RINGS

1. Preformmounted onsaddle/mandrel.

2. Metaldisplacement-reduce preformwall thickness toincreasediameter.

3. Progressivereduction of wallthickness to producering dimensions.

4. Matching tonear net shape.

HOLLOW "SLEEVE TYPE" FORGING

1. Punched or trepanned disc ontapered draw bar.

2. Progressive reduction of outsidediameter (inside diameter remainsconstant) increases overall length ofsleeve.


Open-die forging can produce forgings from a few pounds up to more than 150 tons. Calledopen-die because the metal is not confined laterally by impression dies during forging, thisprocess progressively works the starting stock into the desired shape, most commonly between

7/30/2019 6732653-Forging

8/38

flat-faced dies. In practice, open-die forging comprises many process variations, permitting anextremely broad range of shapes and sizes to be produced. In fact, when design criteria dictateoptimum structural integrity for a huge metal component, the sheer size capability of open-dieforging makes it the clear process choice over non-forging alternatives. At the high end of thesize range, open-die forgings are limited only by the size of the starting stock, namely, thelargest ingot that can be cast.

Practically all forgeable ferrous and non-ferrous alloys can be open-die forged, including someexotic 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 forgingoperations can be combined to produce the required shape. At the same time, these forgingmethods can be tailored to attain the proper amount of total deformation and optimum grain-flowstructure, thereby maximizing property enhancement and ultimate performance for a particularapplication. Forging an integral gear blank and hub, for example, may entail multiple drawing orsolid forging operations, then upsetting. Similarly, blanks for rings may be prepared by upsettingan ingot, then piercing the center, prior to forging the ring.

Seamless Rolled Ring Forging

Seamless rolled ring forgingis typically performed by punching a hole in a thick, round piece ofmetal (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 OPERATIONSGraphical depiction of process steps.

Seamless Rolled Ring Forging Process Operations

1. The ring rolling process typicallybegins with upsetting of the startingstock on flat dies at its plasticdeformation temperature - in the caseof grade 1020 steel, approximately2200 degrees Fahrenheit.

2. Piercing involves forcing a punchinto the hot upset stock causingmetal to be displaced radially, asshown by the illustration.

7/30/2019 6732653-Forging

9/38

3. A subsequent operation, shearing,serves to remove the small punchout...

4. ...producing a completed holethrough the stock, which is now readyfor the ring rolling operation itself. Atthis point the stock is called apreform.

5. The doughnut-shaped preform isslipped over the ID roll shown herefrom an "above" view.

6. A side view of the ring mill andpreform workpiece, which squeezes itagainst the OD roll which impartsrotary action...

7. ...resulting in a thinning of the section and correspondence increase in thediameter of the ring. Once off the ring mill, the ring is then ready forsecondary operations such as close tolerance sizing, parting, heat treatmentand test/inspection


Rings forged by the seamless ring rolling process can weigh < 1 lb up to 350,000 lbs., whileO.D.s range from just a few inches up to 30-ft. in diameter. Performance-wise, there is no equalfor 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 inchup to more than 9 ft. Depending on the equipment utilized, wall-thickness/height ratios of ringstypically range from 1:16 up to 16:1, although greater proportions have been achieved withspecial processing. In fact, seamless tubes up to 48-in. diameter and over 20-ft long areextruded on 20 to 30,000-ton forging presses.

Even though basic shapes with rectangular cross-sections are the norm, rings featuringcomplex, functional crosssections can be forged to meet virtually any design requirements.

7/30/2019 6732653-Forging

10/38

Aptly named, these contoured rolled rings can be produced in thousands of different shapeswith contours on the inside and/or outside diameters. A key advantage to contoured rings is asignificant reduction in machining operations. Not surprisingly, custom-contoured rings canresult 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. Materialsinclude not only carbon and alloy steels, but also non-ferrous alloys of aluminum, copper andtitanium, as well as nickel-base alloys.

WHEREcan you find forgings?

Automotive and TruckIn automotive and truck applications, forged components are commonly foundat points of shock and stress. Cars and trucks may contain more than 250

forgings, most of which are produced from carbon or alloy steel.Forged engineand powertrain components include connecting rods, crankshafts, transmissionshafts and gears, differential gears, drive shafts, clutch hubs, and universal joint yokes andcrosses. Forged camshafts, pinions, gears, and rocker arms offer ease of selective hardeningas well as strength. Wheel spindles, kingpins, axle beams and shafts, torsion bars, ball studs,idler arms, pitman arms, steering arms, and linkages for passenger cars, buses, and truckstypify applications requiring extra strength and toughness.

AerospaceHigh strength-to-weight ratio and structural reliability improve performance, range,and payload capabilities of aircraft. That's why ferrous and nonferrous forgings areused in helicopters, piston-engine planes, commercial jets, and supersonic militaryaircraft. Many aircraft are "designed around" forgings, and contain more than 450

structural forgings as well as hundreds of forged engine parts. Forged parts includebulkheads, wing roots and spars, hinges, engine mounts, brackets, beams, shafts,bellcranks, landing-gear cylinders and struts, wheels, brake carriers and discs, andarresting hooks. In jet turbine engines, iron-based, nickel-base, and cobalt-base

superalloys are forged into buckets, blades, couplings, discs, manifolds, rings, chambers,wheels, and shafts--all requiring uniformly high-yield tensile and creep rupture strengths, plusgood ductility at temperatures ranging between 1,000 and 2,000F. Forgings of stainless steels,maraging steels, titanium, and aluminum find similar applications at lower temperatures. Forgedmissile components of titanium, columbium, super alloys, and refractory materials provideunduplicated mechanical and physical properties under severe service conditions. Aluminumstructural beams for boosters, titanium motor cases, and nuclear-engine reactor shields andinflatable satellite launch canisters of magnesium are used in the space shuttle program.

Off-Highway and AgriculturalStrength, toughness, machinability, and economy account for theuse of ferrous forgings in off-highway and heavy constructionequipment, and in mining machinery. In addition to engine andtransmission parts, forgings are used for gears, sprockets, levers,

shafts, spindles, ball joints, wheel hubs, rollers, yokes, axle beams,bearing holders, and links. Farm implements, in addition to engine and transmissioncomponents, utilize key forgings ranging from gears, shafts, levers, and spindles to tie-rod ends,spike harrow teeth, and cultivator shanks.

7/30/2019 6732653-Forging

11/38

OrdnanceForged components are found in virtually every implement of defense, from rifletriggers to nuclear submarine drive shafts. Heavy tanks contain more than 550separate forgings; armored personnel carriers employ more than 250. Themajority of 155-mm, 75-mm, and 3-in. shells as well as mortar projectiles

contain at least two forged components.

Valves and FittingsFor valves and fittings, the mechanical properties of forgings and their freedomfrom porosity are especially suited to high-pressure applications. Corrosion andheat-resistant materials are used for flanges, valve bodies and stems, tees, elbows,reducers, saddles, and other fittings. Oilfield applications include rock cutter bits,drilling hardware, and high-pressure valves and fittings.

Industrial, Hardware and ToolsStationary and shipboard internal combustion engines include forged crankshafts, connectingrods, rod caps, camshafts, rocker arms, valves, gears, shafts, levers, and linkages. Outboardmotors, motorcycles, and power saws offer examples of the intensive use of forgings insmaller engines. Industrial equipment industries use forgings in materials handling systems,

conveyors, chain-hoist assemblies, and lift trucks.

"Forged" is the mark of quality in hand tools and hardware. Pliers, hammers, sledges,wrenches, and garden implements, as well as wire-rope clips and sockets, hooks, turnbuckles,and eye bolts are common examples. Strength, resistance to impact and fatigue, and excellentappearance are reasons why forgings have been the standard of quality since the earliest oftimes. The same is true of surgical instruments. Special hardware for electrical transmission anddistribution lines is subject to high stresses and corrosion. For strength and dependability,forgings are used for parts such as pedestal caps, suspension clamps, sockets, and brackets.

WHY are forgings so prevalent?

The degree of structural reliability achieved in a forging is unexcelled by any other metalworkingprocess. There are no internal gas pockets or voids that could cause unexpected failure understress or impact. Often, the forging process assists in improving chemical segregation of theforging stock by moving centerline material to various locations throughout the forging.

El esfuerzo Direccional es Clave

Directional Strength is KeyDirectional strength is a direct result of the forging process. In the forging process, controlleddeformation (usually at elevated temperatures) results in greater metallurgical soundness andimproved mechanical properties of the material. In mostcases, forging stock has been pre-worked to removeporosity resulting from the solidification process. Thisproduces directional alignment (or "grain flow") forimportant directional properties in strength, ductility, andresistance to impact and fatigue.These properties aredeliberately oriented in directions requiring maximumstrength. Working the material achieves recrystallizationand grain refinement that yields the maximum strengthpotential of the material with the minimum propertyvariation, piece-to-peace.

7/30/2019 6732653-Forging

12/38

Properly developed grain flow in forgings closely follows the outline of the component. Incontrast, bar stock and plate have unidirectional grain flow; any changes in contour will cut flowlines, exposing grain ends, and render the material more liable to fatigue and more sensitive tostress corrosion.

Designers and materials engineers are recognizing the increasing importance of resistance to

impact and fatigue as a portion of total component reliability. With the use of proper materialsand heat treatments, if required, improved impact strength of forged components is achievable.

The resulting higher strength-to-weight ratio can be used to reduce section thickness in partdesigns without jeopardizing performance characteristics of safety. Weight reduction, even inparts produced from less expensive materials, can amount to a considerable cost savings overthe life of a product run.

The consistency of material from one forging to the next, and between separate quantities offorgings is extremely high. Forged parts are made through a controlled sequence of productionsteps rather than random flow of material into the desired shape.

Uniformity of composition and structure piece-to-piece, lot-to-lot, assure reproducible responseto heat treatment, minimum variation in machinability, and consistent property levels of finishedparts.

Dimensional characteristics are remarkably stable. Successive forgings are produced from thesame die impression, and because die impressions exert control over all contours of the forgedpart, the possibility of transfer distortion is eliminated.

For cryogenic applications, forgings have the necessary toughness, high strength-to-weightratios, and freedom from ductile-brittle transition problems.

Forgings are produced economically in an extremely broad range of sizes. With the increaseduse of special punching, piercing, shearing, trimming, and coining operations, there have beensubstantial increases in the range of economical forging shapes and the feasibility of improvedprecision. However, parts with small holes, internal passages, re-entrant pockets, and severedraft limitations usually require more elaborate forging tooling and more complex processing,and are therefore usually more economical in larger sizes.

Sizing Up the Competition

Forging versus Forging Advantages When Using A Similar Alloy

Casting StrongerPreworking refines defectsMore reliable, lower cost overcomponent lifeBetter response to heat treatment

Adaptable to demandWelding/Fabricating Material savings, production economies

StrongerCost-effective design/inspectionMore consistent and better metallurgical propertiesSimplified production

Machining Broader size range of desired material gradesGrain flow provides higher strengthMore economical use of materialYields lower scrapRequires fewer secondary operations

Powder metal Stronger

Higher integrityRequires fewer secondary operationsGreater design flexibility

7/30/2019 6732653-Forging

13/38

Less costly materialsComposites/Plastics Less costly materials

Greater productivityEstablished documentationBroader service-temperature rangeMore reliable service performance

Forgings are superior to metal parts produced by other methods in their compatibility with othermanufacturing processes.

The characteristically uniform refinement of crystalline structure in forged components

assures superior response to all forms of heat treatment, maximum possibledevelopment of desired properties, and unequaled uniformity.

Because forged components of weldable materials have a near absence of structural

defects, material at welding surfaces offers the best possible opportunity for strong,efficient welds by any welding technique.

Again, the near absence of internal discontinuities or surface inclusions in forgings

provides a dependable machining base for metal-cutting processes such as turning,milling, drilling, boring, broaching, and shear spinning; and shaping processes such aselectrochemical machining, chemical milling, electrical-discharge machining, andplasma jet techniques.

Forged parts are readily fabricated by assembling processes such as welding, bolting,

or riveting. More importantly, single-piece forgings can often be designed to eliminatethe need for assemblies.

In many applications, forgings are ready for use without surface conditioning or

machining. Forged surfaces are suited to plating, polishing, painting, or treatment withdecorative or protective coatings.

Forging Spans the Metallurgical Spectrum

Metal Characteristic Application

Aluminum Readily forgedCombines low density with good strength-

to-weight ratio

Primarily for structural and engineapplications in the aircraft andtransportation industries wheretemperatures do not exceed 400F.

Magnesium Offer the lowest density of any commercialmetal

Usually employed at servicetemperatures lower than 500F butcertain alloys provide short-timeservice to 700F.

Copper,Brass,Bronze

Well-suited to forgingElectrical and thermal conductivity

Important for applications requiringcorrosion resistance.

Low-CarbonandLow-AlloySteels

Low material costEasily processedGood mechanical propertiesVaried response to heat treatment gives

designers a choice of properties in thefinished forging

Comprise the greatest volume offorgings produced for serviceapplications up to 900F.

Microalloy/

HSLASteels

Low material cost

Cost benefit derived from simplifiedthermomechanical treatmentEquivalent mechanical properties to many

Various automotive and truck

applications including crankshafts,connecting rods, yokes, pistons,suspension and steering components,

7/30/2019 6732653-Forging

14/38

carbon and low-alloy steels spindles, hubs, and trunio

Special-AlloySteels

Permit forgings with more than 300,000 psiyield strength at room temperature

Used in transportation, mining,industrial and agricultural equipment,as well as high-stress applications inmissiles and aircraft.

StainlessSteel

Corrosion-resistant Used in pressure vessels, steamturbines, and many other applicationsin the chemical, food processing,petroleum, and hospital servicesindustries. Used for high-stress serviceat temperatures up to 1,250F and low-stress service to 1,800F and higher.Nickel-Base

Nickel-BaseSuperalloy

Creep-rupture strengthOxidation resistance

Service in the 1,200-1,800F range.Structural shapes, turbine components,and fittings and valves.

Titanium High strength

Low densityExcellent corrosion resistanceAlloys offer yield strengths in the 120,000 to

180,000 psi range at room temperatures

Used primarily in the temperature

services to 1,000F. Configurationsnearly identical to steel parts areforgeable and 40% lighter in weight.Aircraft-engine components andstructurals, ship components, andvalves and fittings in transportation andchemical industries.

RefractoryMetal

Include columbium, molybdenum, tantalum,and tungsten and their alloys

Enhanced resistance to creep in high-thermal environments

High-temperature applicationsinvolving advanced chemical,electrical, and nuclear propulsionsystems and flight vehicles.

Beryllium Light, hard, and brittleIncreasingly used as an alloying materialHigh melting pointSpecial forging techniques have been

developed to process beryllium in sintered,ingot, or powdered form

Used primarily in nuclear, structural,and heat-sink applications.

Zirconium Corrosion-resistant Produced in relatively limited quantitiesand used almost exclusively in nuclearapplications.

HOWAre Forgings Produced?

Forging--metal shaping by plastic deformation--spans a myriad of equipment and techniques.Knowing the various forging operations and the characteristic metal flow each produces is keyto understanding forging design.

Hammer and Press Forging

Generally, forged components are shaped either by a hammer orpress. Forging on the hammer is carried out in a succession of dieimpressions using repeated blows. The quality of the forging, andthe economy and productivity of the hammer process dependupon the tooling and the skill of the operator. The advent ofprogrammable hammers has resulted on less operator

dependency and improved process consistency. In a press, theFig. 1. Compressionbetween narrow dies.

7/30/2019 6732653-Forging

15/38

stock is usually hit only once in each die impression, and the design of each impressionbecomes more important while operator skill i

The Processes

Open Die ForgingOpen die forging with hammers and presses is amodern-day extension of the pre-industrial metalsmithworking with a hammer at his anvil.

In open die forging, the workpiece is not completelyconfined as it is being shaped by the dies. The open dieprocess is commonly associated with large parts suchas shafts, sleeves and disks, but part weights can rangefrom 5 to 500,000 lb.

Most open die forgings are produced on flat dies. Roundswaging dies and V dies also are used in pairs or with a flat die. Operations performed on opendie presses include:

1. Drawing out or reducing the cross-section of an ingot or billet to lengthen it.

2. Upsetting or reducing the length of an ingot orbillet to a larger diameter.

3. Upsetting, drawing out, and piercing--processessometimes combined with forging over amandrel for forging rough-contoured rings.

As the forging workpiece is hammered or pressed, it is

repeatedly manipulated between the dies until it reachesfinal forged dimensions. Because the process is inexactand requires considerable skill of the forging master,substantial workpiece stock allowances are retained toaccommodate forging irregularities. The forged part isrough machined and then finish machined to finaldimensions. The increasing use of press and hammercontrols is making open die forging, and all forging processes for that matter, more automated.

In open die forging, metals are worked above their recrystallization temperatures. Because theprocess requires repeated changes in workpiece positioning, the workpiece cools during opendie forging below its hot-working or recrystallization temperature. It then must be reheated

before forging can continue. For example, a steel shaft 2 ft in diameter and 24 ft long mayrequire four to six heats before final forged dimensions are reached.

In open die forging of steel, a rule of thumb says that 50 lb of falling weight is required for eachsquare inch of stock cross-section.

Compression between flat dies, orupsetting, is an open die forging process whereby anoblong workpiece is placed on end on a lower die and its height reduced by the downwardmovement of the top die. Friction between end faces of the workpiece and dies prevents thefree lateral spread of the metal, resulting in a typical barrel shape. Contact with the cool diesurface chills the end faces of the metal, increasing its resistance to deformation and enhancingbarreling.

Upsetting between parallel flat dies is limited to deformation symmetrical around a vertical axis.If preferential elongation is desired, compression between narrow dies (Fig. 1) is ideal.

Fig. 2. Roll forging.

Fig. 3. Roll forging using specialityshaped rolls.
http://www.forging.org/facts/wwhy6.htm#fig1#fig1http://www.forging.org/facts/wwhy6.htm#fig1#fig1

7/30/2019 6732653-Forging

16/38

Frictional forces in the axial direction of the bar are smaller than in the perpendicular direction,and material flow is mostly axial.

A narrower die elongates better, but a too-narrow die will cut metal instead of elongate. Thedirection of material flow can also be influenced by using dies with specially shaped surfaces.

Compression between narrow dies is discontinuous since many strokes must be executed whilethe workpiece is moved in an axial direction. This task can be made continuous by roll forging(Fig. 2). Note the resemblance betweenFig. 1and Fig. 2. The width of the die is nowrepresented by the length of the arc of contact. The elongation achieved depends on the lengthof this contact arc.

Larger rolls cause greater lateral spread and less elongation because of the greater frictionaldifference in the arc of contact, whereas smaller rolls elongate more. Lateral spread can bereduced and elongation promoted by using specially shaped rolls (Fig. 3).

The properties of roll-forged components are very satisfactory. In most cases, there is no flashand the fiber structure is very favorable and continuous in all sections. The rolls perform a

certain amount of descaling, making the surface of theproduct smooth and free of scale pockets.

Impression Die Forging

In the most basic example of impression die forging,which accounts for the majority of forging production,two dies are brought together and the workpieceundergoes plastic deformation until its enlarged sidestouch the die side walls(Fig. 4). Then, some material begins to flow outside thedie impression, forming flash. The flash cools rapidlyand presents increased resistance to deformation,

effectively becoming a part of the tool. This buildspressure inside the bulk of the workpiece, aidingmaterial flow into unfilled impressions.

Impression die forgings may be produced on ahorizontal forging machine (upsetter) in a process referred to as upsetting. In upsetting, stockis held between a fixed and moving die while a horizontal ram provides the pressure to forge thestock (Fig. 5). After each ramstroke, the multiple-impression dies can open to permit transfer ofstock from one cavity to another.A form of impression die forging, closed die forgingdoes not depend on flash formation to achieve completefilling of the die. Material is deformed in a cavity that

allows little or no escape of excess material, thusplacing greater demands on die design.

For impression die forging, forging dies become moreimportant, and operator skill level is less critical in pressforging operations. The press forging sequence isusually block and finish, sometimes with a preform,pierce, or trim operation. The piece is usually hit onlyonce in each die cavity.

The Precision Forging AdvantagePrecision forging normally means close-to-final form or close-

Fig. 4. Impression die forging

Fig. 5. Upsetting.
http://www.forging.org/facts/wwhy6.htm#fig2#fig2http://www.forging.org/facts/wwhy6.htm#fig1#fig1http://www.forging.org/facts/wwhy6.htm#fig1#fig1http://www.forging.org/facts/wwhy6.htm#fig1#fig1http://www.forging.org/facts/wwhy6.htm#fig2#fig2http://www.forging.org/facts/wwhy6.htm#fig3#fig3http://www.forging.org/facts/wwhy6.htm#fig4#fig4http://www.forging.org/facts/wwhy6.htm#fig5#fig5http://www.forging.org/facts/wwhy6.htm#fig2#fig2http://www.forging.org/facts/wwhy6.htm#fig1#fig1http://www.forging.org/facts/wwhy6.htm#fig2#fig2http://www.forging.org/facts/wwhy6.htm#fig3#fig3http://www.forging.org/facts/wwhy6.htm#fig4#fig4http://www.forging.org/facts/wwhy6.htm#fig5#fig5

7/30/2019 6732653-Forging

17/38

tolerance forging. It is not a special technology, but a refinement ofexisting techniques to a point where the forged part can be usedwith little or no subsequent machining. Improvements cover notonly the forging method itself but also preheating, descaling,lubrication, and temperature control practices.The decision to apply precision forging techniques depends on the

relative economics of additional operations and tooling vs.elimination of machining. Because of higher tooling anddevelopment costs, precision forging is usually limited to extremelyhigh-quality applications.

Ring RollingRing rolling has evolved from an art into astrictly controlled engineering process.Seamless rolled rings are produced on avariety of equipment. All give the same

product--a seamless section withcircumferential grain orientation. Theserings generally have tangential strengthand ductility, and often are less expensiveto manufacture than similar closed dieforgings. In sum, the ring rolling processoffers homogeneous circumferential grainflow, ease of manufacture, and versatility inmaterial, size, mass, and geometry.

In the ring rolling process, a preform isheated to forging temperature and placedover the idler (internal) roll of the rollingmachine. Pressure is applied to the wall by the main (external) roll as the ring rotates. Thecross-sectional area is reduced as the inner and outer diameters are expanded. Equipment canbe fully automated from billet heatingthrough post-forge handling. Advanced ring rollingequipment can roll contours in both the inner and outer diameter of the ring, allowing forexcellent weight reductions, material savings, and reduced machining cost.There is an infinite variety of sizes into which rings can be rolled, ranging from rollerbearingsleeves to rings of 25 ft in diameter with face heights of more than 80 in. Various profiles may berolled by suitably shaping the drive and idling rolls.

ExtrusionIn extrusion (Fig. 6), the workpiece is placed in acontainer and compressed until pressure insidethe metal reaches flowstress levels. Theworkpiece completely fills the container andadditional pressure causes it to travel through anorifice and form the extruded product.Extrusion can be forward (direct) or backward(reverse), depending on the direction of motionbetween ram and extruded product. Extrudedproduct can be solid or hollow. Tube extrusion istypical of forward extrusion of hollow shapes,and backward extrusion is used for massproduction of containers.Piercing is closely related to reverse extrusion but distinguished by greater movement of thepunch relative to movement of the workpiece material.

Stages in the Ring Rolling Process

.

2 3

4 5

6 7

Fig. 6. a-Foward extrusion; b-backwardextrusion; c-tube extrusion; d-containerextrusion.
http://www.forging.org/facts/wwhy6.htm#fig6#fig6http://www.forging.org/facts/wwhy6.htm#fig6#fig6

7/30/2019 6732653-Forging

18/38

Secondary ProcessesBesides the primary forging processes, secondary operations often areemployed. Drawing through a die is a convenient way to eliminate forgeddraft (Fig. 7a). The mode of deformation is tangential compression. Thediameter of the drawing ring can be slightly smaller than the outer diameterof the preforged shell to control or reduce wall thickness and increase the

height of the shell in a drawing orironing operation (Fig. 7b).

Bending can be performed on the finished forging or at any stage duringits production.

Because forging stock may assume complex shapes, it is rare that only asingle die impression is needed. Preforming the forging stock--by bendingor rolling it, or by working it in a preliminary die--may be more desirable.Gains in productivity, die life, and forging quality often outweigh the fact thatpreforming adds an operation and attendant costs. Forging in one final dieimpression may be practical for extremely small part runs.

Since bending of larger parts requires a machine of long stroke, special mechanical or hydraulic

presses are often necessary. Simple shapes can be bent in one operation, but more complexcontours take successive steps. If complex shapes are to be formed in a single operation, thetool must contain moving elements.

Special TechniquesAfter deformation, forged parts may undergo further metalworking. Flash is removed, punchedholes may be needed, and improved surface finish or closer dimensional accuracy may bedesired.

Trimming--Flash is trimmed before the forging is ready for shipping. Occasionally, especiallywith crack-sensitive alloys, this may be done by grinding, milling, sawing, or flame cutting.

Coining--Coining and ironing are essentially sizing operations with pressure applied to criticalsurfaces to improve tolerances, smoothen surfaces, or eliminate draft.Coining is usually done on surfaces parallel to the parting line, while ironing is typified by theforcing of a cup-shaped component through a ring to size on outer diameter. Little metal flow isinvolved in either operation and flash is not formed.

Swaging--This operation is related to the open die forging process whereby the stock is drawnout between flat, narrow dies. But instead of the stock, the hammer is rotated to producemultiple blows, sometimes as high as 2,000 per minute. It is a useful method of primary working,although in industrial production its role is normally that of finishing. Swaging can be stopped atany point in the length of stock and is often used for pointing tube and bar ends and forproducing stepped columns and shafts of declining diameter.

Hot Extrusion--Extrusion is most suitable for forming parts ofdrastically changing cross section and is, therefore, a directcompetitor to continuous upsetting and the horizontal forgingmachine. InFig. 8, a bar section of carefully controlled volume isheated, descaled, and placed into the die. Under pressure of theclosely fitting punch (Fig. 8a), the material first fills the cavity, thenpart of it is extruded into a long stem. At the end of the stroke (Fig.8b), a valve body is obtained that needs only grinding of theseating surfaces.

There are a number of variants of the extrusion process, many of them patented. The slug maybe hollow (machined), pierced in a separate operation or in the extrusion process itself. In all

instances, the quality of heating, the efficiency of scale removal or prevention, and theeffectiveness of lubrications are matters of greatest importance. The variety of shapes produced

Fig. 7.a-drawing;b-ironing

Fig. 8. Hot extrusion of avalve body.
http://www.forging.org/facts/wwhy6.htm#fig7#fig7http://www.forging.org/facts/wwhy6.htm#fig7#fig7http://www.forging.org/facts/wwhy6.htm#fig8#fig8http://www.forging.org/facts/wwhy6.htm#fig8#fig8http://www.forging.org/facts/wwhy6.htm#fig8#fig8http://www.forging.org/facts/wwhy6.htm#fig8#fig8http://www.forging.org/facts/wwhy6.htm#fig8#fig8http://www.forging.org/facts/wwhy6.htm#fig8#fig8http://www.forging.org/facts/wwhy6.htm#fig8#fig8http://www.forging.org/facts/wwhy6.htm#fig7#fig7http://www.forging.org/facts/wwhy6.htm#fig7#fig7http://www.forging.org/facts/wwhy6.htm#fig8#fig8http://www.forging.org/facts/wwhy6.htm#fig8#fig8http://www.forging.org/facts/wwhy6.htm#fig8#fig8http://www.forging.org/facts/wwhy6.htm#fig8#fig8

7/30/2019 6732653-Forging

19/38

are numerous. Dimensional accuracy, surface quality, and productivity are high, and a greaterdegree of deformation can be achieved in a single operation than in any other forging method.

Cold, Warm, and Hot Forging--What's the Difference?ColdCold forging involves either impression die forging or true closed die forging with lubricant and

circular dies at or near room temperature. Carbon and standard alloy steels are most commonlycold-forged. Parts are generally symmetrical and rarely exceed 25 lb. The primary advantage isthe material savings achieved through precision shapes that require little finishing. Completelycontained impressions and extrusion-type metal flow yield draftless, close-tolerance components.Production rates are very high with exceptional die life. While cold forging usually improvesmechanical properties, the improvement is not useful in many common applications andeconomic advantages remain the primary interest. Tool design and manufacture are critical.

WarmWarm forging has a number of cost-saving advantages which underscore its increasing use as amanufacturing method. The temperature range for the warm forging of steel runs from aboveroom temperature to below the recrystallization temperature, or from about 800 to 1,800F.However, the narrower range of from 1,000 to 1,330F is emerging as the range of perhaps thegreatest commercial potential for warm forging. Compared with cold forging, warm forging has thepotential advantages of: Reduced tooling loads, reduced press loads, increased steel ductility,elimination of need to anneal prior to forging, and favorable as-forged properties that caneliminateheat treatment.

HotHot forging is the plastic deformation of metal at a temperature and strain rate such thatrecrystallization occurs simultaneously with deformation, thus avoiding strain hardening. For thisto occur, high workpiece temperature (matching the metal's recrystallization temperature) must beattained throughout the process. A form of hot forging is isothermal forging, where materials anddies are heated to the same temperature. In nearly all cases, isothermal forging is conducted onsuperalloys in a vacuum or highly controlled atmosphere to preventoxidation.

Introduction

Forging is the process by which metal is heated and is shaped by plasticdeformation by suitably applying compressive force. Usually the compressiveforce is in the form of hammer blows using a power hammer or a press.

Forging refines the grain structure and improves physical properties of themetal. With proper design, the grain flow can be oriented in the direction of

principal stresses encountered in actual use. Grain flow is the direction of thepattern that the crystals take during plastic deformation. Physical properties(such as strength, ductility and toughness) are much better in a forging thanin the base metal, which has, crystals randomly oriented.

7/30/2019 6732653-Forging

20/38

Forgings are consistentfrom piece to piece, without any of the porosity,voids, inclusions and other defects. Thus, finishing operations such as

machining do not expose voids, because there aren't any. Also coatingoperations such as plating or painting are straightforward due to a goodsurface, which needs very little preparation.

Forgings yield parts that have high strength to weight ratio-thus are oftenused in the design of aircraft frame members.

A Forged metal can result in the following

Increase length, decrease cross-section, called drawing outthe metal.

Decrease length, increase cross-section, called upsetting the metal.

Change length, change cross-section, by squeezing in closed impressiondies. This results in favorable grain flow for strong parts

Top of Page

Common Forging Processes

The metal can be forged hot (above recrystallization temperatures) or cold.
http://www.efunda.com/processes/metal_processing/Forging.cfm#PageTop#PageTophttp://www.efunda.com/processes/metal_processing/Forging.cfm#PageTop#PageTop

7/30/2019 6732653-Forging

21/38

Open Die Forgings / Hand Forgings: Open die forgings or hand forgingsare made with repeated blows in an open die, where the operatormanipulates the workpiece in the die. The finished product is a roughapproximation of the die. This is what a traditional blacksmith does, and is

an old manufacturing process.

Impression Die Forgings / Precision Forgings: Impression die forgingsand precision forgings are further refinements of the blocker forgings. Thefinished part more closely resembles the die impression.

Design Consideration:

7/30/2019 6732653-Forging

22/38

Parting surface should be along a single plane if possible, else follow thecontour of the part. The parting surface should be through the center ofthe part, not near the upper or lower edges. If the parting line cannotbe on a single plane, then it is good practice to use symmetry of thedesign to minimize the side thrust forces. Any point on the parting

surface should be less than 75 from the principal parting plane.

As in most forming processes, use of undercuts should be avoided, asthese will make the removal of the part difficult, if not impossible.

Recommended draft angles are described in the following table.

Material Draft Angle ()

Aluminum 0 - 2

Copper Alloys (Brass) 0 - 3

Steel 5 - 7

Stainless Steel 5 - 8

Generous fillets and radius should be provided to aid in material flowduring the forging process. Sharp corners are stress-risers in theforgings, as well as make the dies weak in service. Recommendedminimum radiuses are described in the following table.

Height ofProtrusion

mm(in)

Min. CornerRadius

mm(in)

Min. FilletRadius

mm(in)

12.5(0.5)

1.5(0.06)

5(0.2)

25(1.0)

3(0.12)

6.25(0.25)

50(2.0)

5(0.2)

10(0.4)

100(4.0)

6.25(0.25)

10(0.4)

400

(16)

22

(0.875)

50

(2.0)

Ribs should be not be high or narrow, this makes it difficult for thematerial to flow.

Tolerances:

7/30/2019 6732653-Forging

23/38

Dimension tolerances are usually positive and are approximately 0.3 %of the dimension, rounded off to the next higher 0.5 mm (0.020 in).

Die wear tolerances are lateral tolerances (parallel to the parting plane)

and are roughly +0.2 % for Copper alloys to +0.5 % for Aluminum andSteel.

Die closure tolerances are in the direction of opening and closing, andrange from 1 mm (0.040 inch) for small forgings, die projection area 6500 cm2 (100 in2).

Die match tolerances are to allow for shift in the upper die with respectto the lower die. This is weight based and is shown in the the followingtable.

Material

Finished Forging WeightTrimmed kg (lb)

< 10(< 22)

< 50(< 110)

> 500(> 1100)

Die Match Tolerancemm (in)

Aluminum,Copper Alloys,Steel

0.75(0.030)

1.75(0.070)

5(0.200)

Stainless Steel,Titanium 1.25(0.050) 2.5(0.100) 6.5(0.260)

Flash tolerance is the amount of acceptable flash after the trimmingoperation. This is weight based and is shown in the following table.

Material

Finished Forging WeightTrimmed kg (lb)

< 10(< 22)

< 50(< 110)

> 500(> 1100)

Flash Tolerance

mm (in)

Aluminum,Copper Alloys,Steel

0.8(0.032)

3.25(0.125)

10(0.4)

Stainless Steel,Titanium

1.6(0.064)

5(0.2)

12.5(0.5)

A proper lubricantis necessary for making good forgings. The lubricant isuseful in preventing sticking of the workpiece to the die, and also acts as athermal insulator to help reduce die wear.

Press Forgings: Press forging use a slow squeezing action of a press, to

7/30/2019 6732653-Forging

24/38

transfer a great amount of compressive force to the workpiece. Unlike anopen-die forging where multiple blows transfer the compressive energy tothe outside of the product, press forging transfers the force uniformly to thebulk of the material. This results in uniform material properties and is

necessary for large weight forgings. Parts made with this process can bequite large as much as 125 kg (260 lb) and 3m (10 feet) long.

Upset Forgings: Upset forging increases cross-section by compressing thelength, this is used in making heads on bolts and fasteners, valves and othersimilar parts.

Roll Forgings: In roll forging, a bar stock, round or flat is placed betweendie rollers which reduces the cross-section and increases the length to formparts such as axles, leaf springs etc. This is essentially a form ofdrawforging.

Swaging: Swaging - a tube or rod is forced inside a die and the diameter isreduced as the cylindrical object is fed. The die hammers the diameter andcauses the metal to flow inward causing the outer diameter of the tube orthe rod to take the shape of the die.

Net Shape / Near-Net Shape Forging: In net shape or near-net shapeforging, forging results in wastage of material in the form of material flashand subsequent machining operations. This wastage can be as high as 70 %for gear blanks, and even 90+ % in the case of aircraft structural parts. Net-shape and near-net-shape processes minimize the waste by making precisiondies, producing parts with very little draft angle (less than 1). These types

of processes often eliminate or reduce machining. The processes are quiteexpensive in terms of tooling and the capital expenditure required. Thus,these processes can be only justified for current processes that are verywasteful where the material savings will pay for the significant increase intooling costs.Facts About ForgingWhen buyers must select a process and supplier for the production of an important metal part,they face an enormous array of possible alternatives. A great many metalworking processes arenow available, each offering a unique set of capabilities, costs and advantages. The forgingprocess is ideally suited to many part applications, however some buyers may be unaware of theexclusive benefits available only from this ancient form of metal forming. In fact, forging is oftenthe optimum process, in terms of both part quality and cost-efficiency-especially for applicationsthat require maximum part strength, special sizes or critical performance specifications.

There are several forging processes available, including impression or closed die, cold forging, andextrusion. However,here we will discuss in detail the methods, application and comparative

7/30/2019 6732653-Forging

25/38

benefits of the open die and seamless rolled ring forging processes. We invite you to consider thisinformation when selecting the optimum process for the production of your metal parts.

A Historical PerspectivePerhaps the oldest mechanical method of metalworking known to man, forging traces its originsfrom ancient Egypt through the blacksmith shops of the pre-industrial period, and directly to thehigh-technology forging plants of today.

To meet the changing needs of industry, forging has evolved to incorporate the tremendousadvances in equipment, computers and electronic controls that have occurred in recent years.These sophisticated tools complement the creative human skills which, even today, are essential tothe success of every forging made. Modern forging plants are capable of producing superior qualitymetal parts in a virtually limitless array of sizes, shapes, materials and finishes.

Forging DefinedAt its most basic level, forging is the process of forming and shaping metals through the use ofhammering, 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 plasticdeformation temperature, then upset or"kneaded" between dies to the desired shapeand size.

During this hot forging process, the cast, coarsegrain structure is broken up and replaced byfiner grains. Low-density areas, microshrinkageand gas porosity inherent in the cast metal areconsolidated through the reduction of the ingot,achieving sound centers and structural integrity.Mechanical properties are therefore improvedthrough the elimination of the cast structure,enhanced density, and improved homogeneity.Forging also provides means for aligning thegrain flow to best obtain desired directional strengths. Secondary processing, such as heattreating, can also be used to further refine the part.

No other metalworking process can equal forging in its ability to develop the optimum combinationof properties.

Open Die Forging

Open die forging involves the shaping of heated metal parts between a top die attached to a ramand a bottom die attached to a hammer anvil or press bed. Metal parts are worked above theirrecrystallization temperatures-ranging from 1900F to 2400F for steel-and gradually shaped intothe desired configuration through the skillful hammering or pressing of the work piece.

While impression or closed die forging confines the metal in dies, open die forging is distinguishedby the fact that the metal is never completely confined or restrained in the dies. Most open dieforgings are produced on flat dies. However, round swaging dies, V-dies, mandrels, pins and loosetools are also used depending on the desired part configuration and its size.

Although the open die forging process is often associated with larger, simpler-shaped parts such asbars, blanks, rings, hollows or spindles, in fact it can be considered the ultimate option in "custom-designed" metal components. High-strength, long-life parts optimized in terms of both mechanicalproperties and structural integrity are today produced in sizes that range from a few pounds tohundreds of tons in weight. In addition, advanced forge shops now offer shapes that were neverbefore thought capable of being produced by the open die forging process.

The Open Die Forging ProcessSteps to produce a typical spindle-shaped part:

1. Rough forging a heated billet betweenflat dies to the maximum diameterdimension.

How the open die forging processaffects the crystal structure.

7/30/2019 6732653-Forging

26/38

2. A "fuller" tool marks the starting "step"locations on the fully rounded workpiece.

3. Forging or "drawing" down the first stepto size.

4. The second step is drawn down to size.Note how the part elongates with eachprocess step as the material is beingdisplaced.

5. "Planishing" the rough forging for asmoother surface finish and to keepstock allowance to a minimum.

Rolled Ring Forging

The production of seamless forged rings is often performed by a process called ring rolling onrolling mills. These mills vary in size to produce rings with outside diameters of just a few inchesto over 300" and in weights from a single pound up to over 300,000 pounds.

The process starts with a circular preform of metal that has been previously upset and pierced(using the open die forging process) to form a hollow "donut". This donut is heated above therecrystallization temperature and placed over the idler or mandrel roll. This idler roll then moves

under pressure toward a drive roll that continuously rotates to reduce the wall thickness, therebyincreasing the diameters (I.D. and O.D.) of the resulting ring.

Seamless rings can be produced in configurations ranging from flat, washer-like parts to tall,cylindrical shapes, with heights ranging from less than an inch to more than 9 feet. Wall thicknessto height ratios of rings typically range from 1:16 up to 16:1, although greater proportions can beachieved with special processing. The simplest, and most commonly used shape is a rectangularcross-section ring, but shaped tooling can be used to produce seamless rolled rings in complex,custom shapes with contours on the inside and/or outside diameters.

The Seamless Rolled Ring Forging ProcessProducing a ring "preform" by the open die forging process:

7/30/2019 6732653-Forging

27/38

1. Starting stock cut to size by weight isfirst rounded, then upset to achievestructural integrity and directional grain

flow.

2. Work piece is punched, then pierced toachieve starting "donut" shape neededfor ring rolling process.

3. Completed preform ready for placementon ring mill for rolling.

Rolled ring forging process:

4.

Ring rolling process begins with the idler roll

applying pressure to the preform against thedrive roll.

5. Ring diameters are increased as thecontinuous pressure reduces the wallthickness. The axial rolls control the height ofthe ring as it is being rolled.

6. The process continues until the desired sizeis achieved.

Part Integrity

1.Directional StrengthBy mechanically deforming the heated metal under tightly controlled conditions, forging producespredictable and uniform grain size and flow characteristics. Forging stock is also typically pre-worked to refine the dendritic structure of the ingot and remove defects or porosity. These

7/30/2019 6732653-Forging

28/38

qualities translate into superior metallurgical and mechanical qualities, and deliver increaseddirectional strength in the final part.

2.Structural StrengthForging also provides a degree of structural integrity

that is unmatched by other metalworking processes.Forging eliminates internal voids and gas pockets thatcan weaken metal parts. By dispersing segregation ofalloys or nonmetallics, forging provides superiorchemical uniformity. Predictable structural integrityreduces part inspection requirements, simplifies heattreating and machining, and ensures optimum partperformance under field-load conditions.

3.Impact StrengthParts can also be forged to meet virtually any stress, load or impact requirement. Properorientation of grain flow assures maximum impact strength and fatigue resistance. The high-strength properties of the forging process can be used to reduce sectional thickness and overallweight without compromising final part integrity.

Grain Flow Comparison

Forged Bar:Directional alignment through the forging process has been deliberatelyoriented in a direction requiring maximum strength. This also yields ductilityand resistance to impact and fatigue.Machined Bar:Unidirectional grain flow has been cut when changing contour, exposing grainends. This renders the material more liable to fatigue and more sensitive tostress corrosion cracking.Cast Bar:No grain flow or directional strength is achieved through the casting process.

Part Flexibility

1.Variety of SizesLimited only to the largest ingot that can be cast, open die forged part weights can run froma single pound to over 400,000 pounds. In addition to commonly purchased open die parts,forgings are often specified for their soundness in place of rolled bars or castings, or forthose parts that are too large to produce by any other metalworking method.

2.Variety of ShapesShape design is just as versatile, ranging from simple bar, shaft and ring configurations to

specialized shapes. These include multiple O.D./I.D. hollows, single and double hubs that approachclosed die configurations, and unique, custom shapes produced by combining forging withsecondary processes such as torch cutting, sawing and machining. Shape designs are often limitedonly by the creative skills and imagination of the forging supplier.

3.Metallurgical SpectrumForgings can be produced from literally all ferrous and non-ferrous metals. The forging processitself can be adjusted-through the selection of alloys, temperatures, working methods and post-forming techniques-to yield virtually any desired metallurgical property.

4.Quantity and Prototype OptionsVirtually all open die and rolled ring forgings are custom made one at a time, providing the optionto purchase one, a dozen or hundreds of parts as needed. An added benefit is the ability to offeropen die prototypes in single piece or low volume quantities. No better way exists to test initialclosed die forging designs, because open die forging imparts similar grain flow orientation,deformation, and other beneficial characteristics. In addition, the high costs and long lead times

associated with closed die tooling and set-ups are eliminated.

Cross section of continuous grain flowof custom forged contoured ring.

7/30/2019 6732653-Forging

29/38

What is Forging?

Forging is manufacturing process where metal is pressed, pounded orsqueezed under great pressure into high strength parts known as forgings. The

process is normally (but not always) performed hot by preheating the metal to adesired temperature before it is worked. It is important to note that the forgingprocess is entirely different from the casting (or foundry) process, as metal usedto make forged parts is never melted and poured (as in the casting process).

Why use Forgings and where are they used?

The forging process can create parts that are stronger than those manufacturedby any other metalworking process. This is why forgings are almost alwaysused where reliability and human safety are critical. But you'll rarely seeforgings, as they are normally component parts contained inside assembled

items such a airplanes, automobiles, tractors, ships, oil drilling equipment,engines, missiles and all kinds of capital equipment - to name a few.

How FORGINGS compare to Castings

Forgings are stronger. Casting cannot obtain the strengthening effects of hotand cold working. Forging surpasses casting in predictable strength properties -producing superior strength that is assured, part to part.

Forging refines defects from cast ingots or continuous cast bar. A casting hasneither grain flow nor directional strength and the process cannot preventformation of certain metallurgical defects. Pre-working forge stock produces agrain flow oriented in directions requiring maximum strength. Dendriticstructures, alloy segregation's and like imperfections are refined in forging.

Forgings are more reliable, less costly. Casting defects occur in a variety offorms. Because hot working refines grain pattern and imparts high strength,ductility and resistance properties, forged products are more reliable. And theyare manufactured without the added costs for tighter process controls andinspection that are required for casting.

Forgings offer better response to heat treatment. Castings require closecontrol of melting and cooling processes because alloy segregation may occur.This results in non-uniform heat treatment response that can affect straightnessof finished parts. Forgings respond more predictably to heat treatment and offerbetter dimensional stability.

Forgings' flexible, cost-effective production adapts to demand. Some castings,such as special performance castings, require expensive materials and processcontrols, and longer lead times. Open-die and ring rolling are examples offorging processes that adapt to various production run lengths and enableshortened lead times.

7/30/2019 6732653-Forging

30/38

The History of Forgings

Durante la edad del oscurantismo(Alta Edad Media) la produccin de armas prosper. Lacultura europea y la industria fueron seriamente retrasadas debido a guerras constantes. An laIndustria siderrgica permaneci intacta debido a la necesidad de armas.Uno de los acontecimientos ms significativos vino de la combinacin del descubrimiento

romano de energa hidrulica y la forja de metales. La energa hidrulica fue usada paramanejar el fuelle y martillos mecnicos. Este descubrimiento significativo entr en el empleoentre los siglos X y XII D. de C.

Forja(Falsificacin) como una forma de arte comenzada con el deseo de producir objetosdecorativos de metales preciosos. Hoy, la forja(falsificacin) es una industria principal mundialque considerablemente ha contribuido al desarrollo de hombre

The 19th century invention of the steam engine brought us to the doorstep ofmodern forging as we know it. Of course, to follow was the harnessing of electricalpower and the development of explosive forming, which truly brought forging out ofthe dark ages.

Forging as an art form started with the desire to produce decorative objects fromprecious metals. Today, forging is a major world-wide industry that has significantlycontributed to the development of man.

7/30/2019 6732653-Forging

31/38

5.2.4.2 Cold Forging Processes

There is a variety of cold forging processes currently in -use, either alone or in combination.Following is an overview of those used most often.

Forward Extrusion In the most common forward extrusion process, a billet is pushed through acontainer or die by means of a punch. The material flows in the same direction as the punch to

provide various types of exit sections. The process is also used on hollow slugs to reduce wallthickness, and to manufacture cans with either cylindrical cavities or cavities with varying crosssections. It is used to produce solid shapes such as rounds, thread blanks, squares, rectangles,triangles, polygons and splines. Hollow shapes, including rounds, polygons and splines are alsoforward extruded. Figure 5-18 shows three types of forward extrusion.

Backward Extrusion In this process, the material flows in the opposite direction to the upperpunch. The workpiece is formed either in the cavity formed between the punch and die, or in thecavity of the punch. Backward extrusion is used to produce circular inside and outsidediameters, squares with rounded corners, multiple outside diameters and multiple insidediameters. Figure 5-19 shows three types of backward extrusion.

Side Extrusion In this process, the material flows lateral to the direction of the punch, generallyin one direction. Two types of lateral extrusion are shown in Figure 5-20.

Upsetting In this process, material flows lateral to the direction of the punch in all directions,increasing the cross section of the stock. The term "heading" is often used interchangeably withupsetting. Sometimes a distinction is drawn, and "heading" (or "flanging") is used to describeupsetting at the end of the workpiece, and "gathering" to describe upsetting at locations otherthan the end. Headed shapes include T- and L-heads, ball heads, square heads and socketheads. Three types of upsetting operations are shown in Figure 5-21.

Ironing In this process, the wall thickness of hollow cans or tubes is reduced, as shown inFigure 5-22. The force is applied to the bottom of the preform by a relatively long punch. Theprocess differs from forward extrusion in that the workpiece is in tension, whereas forward

extrusion places the workpiece in compression.

7/30/2019 6732653-Forging

32/38

Nosing Nosing is used to reduce the end of a backward extrusion, or its radius. The process isshown in Figure 5-23.

Radial Forging In this process, tools moving radially forge the workpiece to the desired shape,as shown in Figure 5-24. Radial forging can also be used to make solid parts, such as axles.Hollow parts, such as gun barrels, can be axially forged using a mandrel.

Bending Bending operations are often used to generate non-symmetrical shapes. The processis used to produce rod and bar shapes with and without heads, including J-, S, U-, W-, and Z-bends.

Combined Processes Many of the above processes can be combined to advantage in a singleoperation. For example, forward and backward extrusion are combined to produce shaft gearswith either solid or cup heads, splined shafts and threaded shafts. Seven common processcombinations are shown in Figure 5-25.

Process Sequence In almost all cases, cold forgings are made in several forming strokes. Thenumber of strokes is determined by the formability of the alloy, die loading, press loading, press

characteristics, and the opportunity to combine processes. If the formability limit is reached, theworkpiece must be annealed in an intermediate stage before proceeding with the nextoperation. The application of surface coatings between processes may be necessary for somematerials. The design of process sequence is therefore based on many years of experience bythe process design engineer.

Process sequences for two cold forgings are shown in Figures 5-26 and 5-27. The processsequence for the bevel gear in the figure shows the progress in cold forming technology inrecent years to produce very intricate shapes

7/30/2019 6732653-Forging

33/38

El taller de forjado est dotado de dos prensas mecnicas para el forjado en matrices -una de 4000 y otra de2500 toneladas-, donde se elaboran bridas de dimensiones limitadas adems de engranajes y ejes para laindustria productora de maquinaria agrcola.

Este departamento cuenta tambin con un grupo de martillos -el mayor de 16.000 Kgm.- que son utilizadospara realizar forja libre con la ayuda de manipuladores de 3000, 1500 y 750 Kg.

A modo de ejemplos de fabricacin podemos mencionar:

Cabezas de pozo

Cuerpos de vlvulas

Bielas

Repuestos ferroviarios

Ruedas de puente gra

Discos

Placas tubulares

7/30/2019 6732653-Forging

34/38

Welcome to TW Stamping

7/30/2019 6732653-Forging

35/38

Forging

Components can be forged into an infinite variety of shapes which would be difficultto produce by conventional machining or fabrication techniques. The result is aproduct with a superior surface finish, lack of porosity and enhanced strength sinceit does not suffer from internal stresses and it's grain structure has been improved.The result is a cost effective product fit for most applications.

Tooling is relatively cheap and setting times short, this allows for economicproduction down to as little as a couple of hundred piece parts per order.

As well as forging in brass we also work in aluminium, copper, aluminium bronze,etc.

Machining

After forging, many customers find it economical for the subsequent machiningoperations to be carried out by the supplier of the brass stampings. The photograph

gives a few examples of the vast range of items which we machine after they havebeen forged. This is in fact due to the very efficient re-cycling of machining waste.This also includes work in aluminium, copper, etc.

By virtue of the fact that we are sub contractors, our products have to comply withmany British and foreign standards, a few of which are,

BS5433 Underground stop valves for water services

BS3288 Electrical fittings

BS 746 Gas Meter Unions And Adapters

BS2767 Valves and unions for hot water radiators

7/30/2019 6732653-Forging

36/38

BS1010 Draw off taps and stop valves

BS5154 Globe, check and gate valves

Electrical Components

Our range of products include:

Parts for lighting fittings

Immersion and kettle element heads and other domestic

appliance components.

Distribution line fittings including pole mounted fuse

holders, line taps, etc.

Cable Sockets

Components for generators, transformers and switchgear

Parts for telephone, radio, radar and scientific equipment

Components for industrial use such as railway traction

engines, welding sets and traffic control equipment

Gas Fittings

Our range includes parts for the gas supply industry such

as unions, connectors, meter couplers, etc.

We manufacture a multitude of parts for the domestic gas

appliance industry such as elbows, tees, gas cocks and

manifolds.

In addition we supply decorative and other fittings for use

on domestic gas fires and cookers.

Hydraulic / Pneumatic Applications

We manufacture many parts for hydraulic/ pneumatic applications, these beingused in a variety of situations from mining equipment through industrial applicationsfor use on aircraft. In particular we manufacture items which are subject to highpressure with CO2 and other bottled gases. In this case these items are fully testedwell above the required specification.

Security

It is commonplace for lock and bolt parts to be made from brass components sincethese do not suffer from failure through corrosion attack in the event of adverseweather conditions. Such fittings are ideally made using the hot forging process.

7/30/2019 6732653-Forging

37/38

Many other applications are now to be found in the home security market which usehot brass forging in production.

Decorative Hardware

It has always been traditional to use hot brass forgings in the manufacture of doorhandles, window stays and other types of architectural fittings. In recent years therehas been a vast increase in the use of highly decorative components for otheritems of door furniture such as letter boxes, finger plates, door pulls, etc.

Sport and Leisure

A popular use for aluminium components is found in the world of mountaineering inwhich it is commonplace to use such items as 'karabineer' hooks or parts for iceaxes.

Similarly hot brass forging are incorporated into the design of many popular typesof golf club putters.

Transport: Road, Rail, Ship, Aircraft

There are many applications for hot brass forgings in the transport industry. Theserange from parts for road vehicles such as elbows or tees in the fuel line, flangesfor petrol tanks, radiator filler caps, etc. to discrete items such as battery terminals,light weight wheel nuts and hinges and fittings for heavy goods vehicles, suppliedto component manufacturers.

Hot brass, aluminium, aluminium bronze forgings are used extensively in themarine industry. Typically such items would include shackles and turnbuckles onyachts, parts for pumps, guard-wire terminals, etc.

On aircraft there is a greater tendency to use items forged in aluminium.

Assembly Work

As well as forging and machining we have a considerable capacity for work whichrequires sub-assembly before use. It is usual for the resulting assembly to consistpredominantly of hot brass forged and machined components. However, we are

obviously willing to discuss any other type of assembly work. The problems ofresourcing the parts, and as necessary holding them against scheduled call-offdevolve onto TW Stamping Limited.

7/30/2019 6732653-Forging

38/38

Date post:	04-Apr-2018
Category:	Documents
Upload:	bhushan-verma
View:	215 times
Download:	0 times

6732653-Forging

Documents