Forging of Metals Flashcards
Forging is used for products that need to withstand __________________
High forces
Compared to _________, forging offers less ___________ but better ___________ such as superior _________,
__________ and __________
casting, form freedom, material properties, strength, ductility, hardness
Forging has a _________ practical weight range and the potential for ____________ production volumes but can also be made by hand as _____________
large, very high, one offs
In forging, the ___________material properties are largely due to the fact that the grain __________ along with the part creating a ___________ and ____________ grain structure with _________ weak spots
improved, deforms, continuous, fibrous, fewer
In forging operation, a ________, (aka, _________, _________or ________) is compressed between __________ to produce a ____________ in height
Billet, workpiece, blank, slug, flat dies, decrease
______________ is when the volume stays constant but the diameter increases
Upsetting
Plotting _____________ vs. ____________shows an ____________ relationship where large shape changes
require ____________
upsetting force, billet height, exponential, large forces
Three reasons for Exponential relationship between Upsetting force and Billet height:
1. Cross sectional area ____________ so more ______ is 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
increases, force, stress, cold, strain hardening, Friction
In upsetting, it is ____________ to achieve tight tolerances in the ___________ because the dies will also deform ___________ under the compressive load
difficult, main axis, elastically
Forces involved with upsetting 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
very large, series of impacts, series of dies, load
Cold forging is generally defined as forging below _________ of melting temperature (in Kelvin)
40%
Warm forging is between ________ and _________ of melting temp
40%-80%
Hot forging occurs above ________ of melting temp
80%
Recall that most metals have a ________________ , so the melting temp here refers to the lower end of the range (______)
solidification range, Tsolidus
Hot forging is at an elevated temperature, yield strength is much ________, so requires lower forces to deform metal however, yield stress becomes a function of ____________, i.e., the how fast the metal is being deformed
lower, strain rate
______________________ links the strain-rate and temperature for hot forged materials
Zener-Hollomon
Drawback of Hot forging include:
1. Reduced control over _____________ because _________ 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 tolerances
Tolerances, distortion, warpage, oxidation, cracks, surface defaults, strain hardening, weaker, softening
Friction between the __________and the _________ inhibits the material from the ends from deforming outward which creates a _____________in which material does not deform
dies, material, dead metal zones
Away from ends, material is not _________ by friction and deforms __________ which is called “___________”
impeded, radially, barreling
What are the 6 methods of forging?
Open die forging, Impression forging, Press forging, Net-Shape Forging, Cold Heading, Coining
What forging Method is described below?
o A metal block or rod is manipulated between two dies that move up and down in a fixed rhythm
o Essentially a mechanized version of blacksmith hammer , so it is sometimes called “smith forging”
o Relatively slow process, slow production volumes, but no product specific investment
Open Die Forging
What forging Method is described below?
o Uses profiled dies with goal being to fill the die completely
o Often performed in steps
o Usually uses10% to 20% extra material that is squeezed between the dies
o Known as “Flash”
o Makes billet size less critical
o Material would rather flow into the corners of the die than into the flsh region
Impression forging
What forging Method is described below?
o Uses two dies brought together at low speed by hydraulics
o Allows control over force and displacement (and thus strain rate)
o Also generates flash
o Because it is slower, the billet may cool during forging and need to be reheated during the process
Press Forging
What forging Method is described below?
o Essentially Impression Die forming, but with very tight tolerances and control
o Goal is to eliminate waste and need for finishing
o Beneficial for expensive materials (e.g., titanium) or when the functional and/or quality requirements that demand a tightly controlled process
Net-Shape Forging
What forging Method is described below?
o Used exclusively for fasteners (e.g., nuts and bolts)
o Usually done at room temperature
o Head is formed by passing a thick metal wire through a series of impacting dies
o Threads are made by rolling the parts between grooved plates
o Only feasible with metals that have a low strain hardening exponent, n
Cold Heading
What forging Method is described below?
Used with thin disk-like billlets
o Closed die process (i.e., no __________ is produced)
o Dies are made to be slightly ________so contact and deformation starts in the center
o Otherwise center _________
o Coins have _________ imprints (i.e., ____________ on the die which is much more durable)
flash
convex
wouldn’t deform
positive imprints
negative pattern
