MCHE 3920 Week 6 Forging of Metals

metal, impact

Forging: Centuries old process of transforming ________ to a desired shape through __________

compressive, plastically

_ in forging: ____________ loads _________ deform material

high forces

Forging is Used for products that need to withstand _____________​

knives, hand tools, mining equipment, auto and aerospace

examples of products that are forged

casting, form freedom, mechanical properties

Compared to _________, forging offers less ___________ but better ___________​

strength, ductility, hardness

forging offers superior _____, ______, ______

versatile, large, grams, tons, very high, one-offs

Forging is a __________ process​ with

_________ practical weight range (_____ to _____)​

Potential for ____________ production volumes​

Can also be made by hand as _____________

improved, deforms, continuous, fibrous, fewer

Forging of metals: The ___________material properties are largely due to the fact that the grain __________ along with the part creating a ___________ and ____________ grain structure with _________ weak spots

billet, work piece, blank, slug, flat dies, decrease, constant, upsetting

Metal forging: In simplest operation a ________, (aka, _________, _________or ________) is compressed between __________ to produce a ____________ in height​

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Volume stays __________, so diameter increases ​

Method is called ___________​

upsetting force, billet heights, exponential, large forces  

Plotting _____________ vs. ____________shows an ____________ relationship- large shape changes require ________

increases, force, stress, cold, strain hardening, friction

Three reasons for upsetting relationship​

1. Cross sectional area ____________​

• More ______ required to produce same amount of __________​

2. In_______ forging, _____________ takes place​

3. __________ between the billet and the die makes the billet more resistant to deformation​

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upsetting, sigmat=Ket^n

For a given alloy, the s/s relationship in _______ can be fit to a simple model: _________

true, true stress, area, strain hardening, material constant

Simple upsetting model: s/s are _____; _________ is force divided by instantaneous ______, n is ____________ exponent, K is a _________

more difficult, main axis, elastically

In upsetting, it is ____________ to achieve tight tolerances in the ___________ because the dies will also deform ___________ under the compressive load

very large, series of impacts, series of dies, load

Forces involved are __________ , so shaping is often done with a ______________ to gradually change the shape and sometimes with a ______________ to better distribute the ___________ across the changing shape

Cold, 40%, hundreds of

• ______ forging is generally defined as forging below _________ of melting temperature (in Kelvin)​

• Can still be at ___________ degrees Celsius

Warm, 40%, 80%

______ forging is between ________ and _________ of melting temp

Hot, 80%

______ forging occurs above ________ of melting temp

solidification range, Tsolidus

in cold, warm, hot forging: Recall that most metals have a ________________ , so the melting temp here refers to the lower end of the range (______)

lower, strain rate, Zener-Hollomon

For HOT forging: ​

• At elevated temperature, yield strength is much ________, so requires lower forces to deform metal​

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• However, yield stress becomes a function of ____________, i.e., the how fast the metal is being deformed​

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• Strain-rate and temperature are linked via the “_____________________”

ėe(Q/(RT)), ė, Q, R, yield stress

Zener-Hollomon Parameter is given by: Z=______, where _____ = strain rate, _____ = Activation energy, _____ = Universal gas constant

For a given material, the same Z value indicates the same ___________

tolerances, warpage, distortion, oxidation, cracks, surface faults, strain hardening, weaker, softening

Hot forging drawbacks: ​

1. Reduced control over _____________​

• _________ and ___________ can occur during cooling​

2. _____________ can be severe at higher temperatures leading to __________ and ____________​

3. At elevated temps, there is no _______________, so parts made by hard forging are ___________ than cold-forged parts​

4. High temperatures can lead to recrystallization and grain growth, effectively ____________the material

dies, material, dead metal zone, impeded, radially, barreling

Effects of friction in forging: Friction between the __________and the _________ inhibits the material from the ends from deforming outward​

• Creates a _____________in which material does not deform​

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• Away from ends, material is not _________ by friction and deforms __________​

• Called “___________”

open die forging, manipulated, two, blacksmith’s hammer, smith forging, slow, low, no

In __________: A metal block or rod is ____________ between ________ dies that move up and down in a fixed rhythm​

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• Essentially a mechanized version of a _________________ , so it is sometimes called “______________”​

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• Relatively ___________ process, so __________ production volumes, but __________ product specific investment

completely, 10%, 20%, flash, critical, corners, flash

In _________: ​

• Uses profiled dies with goal being to fill the die __________​

• Often performed in steps​

• Usually uses ________ to __________ extra material that is squeezed between the dies​

• Known as “___________” ​

• Makes billet size less __________​

• Material would rather flow into the ________ of the die than into the ___________ region

press forging, low, force, displacement, strain rate, flash, cool, reheated

In _______: Uses two dies brought together at ________ speed by hydraulics​

• Allows control over ________ and _________ (and thus __________)​

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• Also generates __________​

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• Because it is slower, the billet may _______during forging and need to be __________ during the process

Net-shape forging, impression die forming, eliminate, finishing, expensive, titanium

__________: ​

• Essentially ____________________, but with very tight tolerances and control​

• Goal is to _________ waste and need for __________​

• Beneficial for ___________ materials (e.g., __________) or when the functional and/or quality requirements demand a tightly controlled process

Cold heading, fasteners, bolts, screws, at room temperature, impacting dies, grooved plates, strain hardening exponent (n)

_________: ​

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• Used exclusively for ___________ (e.g., ________ and __________)​

• Usually done _____________________​

• Head is formed by passing a thick metal wire through a series of ________________​

• Threads are made by rolling the parts between ______________​

• Only feasible with metals that have a low _______________________

Coining, flash, convex, wouldn’t deform, positive imprints, negative pattern

__________: Used with thin disk-like billlets​

• Closed die process (i.e., no __________ is produced)​

• Dies are made to be slightly ________so contact and deformation starts in the center​

• Otherwise center _________​

• Coins have _________ imprints (i.e., ____________ on the die which is much more durable)