lecture 2(metal) [read-only] [compatibility mode].pdf
TRANSCRIPT
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Lecture 2
Fabrication &Fabrication &
Thermal ProcessThermal Process
of Metalsof Metals
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....
You should be able to state the purpose andYou should be able to state the purpose anddescribe heat treatment rocess in metaldescribe heat treatment rocess in metal
You should be able to name and describeYou should be able to name and describe
You should be able to provide a suitableYou should be able to provide a suitable
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Fabrication of MetalsFabrication of Metals --MethodsMethods
Metal Fabrication MethodsMetal Fabrication Methods
. . .
Sha e of metal Molten metal is Two or more parts
piece changed by
plastic deformation.
poured into a mouldcavity having
desired sha e.
are joined to for asingle piece
certain ductility canbe formed.
Suitable for
hard/brittle metal. Miscellaneous
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. orm pera o s. orm pera o s
Deformation is achieved at Deformation is achieved
o or ng
temperature at which
recrystalisation can occursbelow the recrystalisation
temperatures
Large deformation is possible.
Deformation can be repeated (soft and ductile)
Metals strain hardened
Higher quality surface finish
Oxidation might occurs bad surface finish
Better mec an ca propert es
Variety of mechanical properties can be formedCloser dimension control of the final piece
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FORMING
Forging Rolling Extrusion Drawing
Stamping
force
die tensileA Addie
Ao Adblankorce
die
Aroll ram billet
container
forcedie holder
Ao
Aextrusion
roll
Ao container die
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Direct
Forging
Mechanically working or deforming a singleMechanically working or deforming a single
piece of a hot metalpiece of a hot metal
Hammered or pressed into a desired shapeHammered or pressed into a desired shape
Mould used to place hot metal in beforeMould used to place hot metal in before
being shaped into desired shapebeing shaped into desired shape
Use for producing large parts; steel shaftsUse for producing large parts; steel shaftsIndirect
Forging
,,connecting rods, or tools like wrenchconnecting rods, or tools like wrench
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ampamp
Mechanically working or deforming a sheet of metalMechanically working or deforming a sheet of metal
sizesize
,,
doors, metal plates etcdoors, metal plates etc
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Rollers
Passing a piece of metalPassing a piece of metalbetween two rollsbetween two rollsMetal
Thickness reduced withThickness reduced with
rolling passrolling pass Cold or hot rolling.Cold or hot rolling.
Cold rolling produces sheet,Cold rolling produces sheet,
strips, foils which can bestrips, foils which can berecrystallised after rollingrecrystallised after rolling
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Mould
A bar of metal is forcedA bar of metal is forcedthrough a die orifice bythrough a die orifice by
Metal Ram
a compressive force thata compressive force that
is applied to a ramis applied to a ram
Rods, tubing, wires,Rods, tubing, wires,
i esi es Mould
Anything withAnything withMetal
Ram
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A bar of metal is drawnA bar of metal is drawnthrou h a die orifice b athrou h a die orifice b a
mould
compressive force that iscompressive force that is
a lied to a rama lied to a rammetal
Start with rods to form wiresStart with rods to form wiresorce
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Cite the best method for the production of:Cite the best method for the production of: Copper wire for electrical cableCopper wire for electrical cable
Aluminium serving platesAluminium serving plates
Automotive bodyAutomotive body Nickel sheet for battery electrodesNickel sheet for battery electrodes
Aluminium foilsAluminium foils
Steel wrenchSteel wrench
II--beam for structural buildingbeam for structural building
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Cite the best method for the production of:Cite the best method for the production of: Copper wire for electrical cableCopper wire for electrical cable --drawingdrawing
Aluminium serving platesAluminium serving plates forging/sheet metal (stamping)forging/sheet metal (stamping)
Automotive bodyAutomotive body -- stampingstamping Nickel sheet for battery electrodesNickel sheet for battery electrodes -- rollingrolling
Aluminium foilsAluminium foils -- rollingrolling
Steel wrenchSteel wrench -- forgingforging
II--beam for structural buildingbeam for structural building extrusionextrusion
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..
Molten metal is poured into a mould cavityhaving the desired shape. Upon
so ca on, e me a assumes e s ape
of the mould but experiences some
shrinkage.
Casting is best used:
To produce metal product of complex shape and
size. Other method is not a licable.
For metal alloys having low ductility that
forging is impossible
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Mould made out of sand using a shape
made by a prototype
Mould made out of
metalmolten
mac ne o es reshape)
Mould made out of plaster/sandusing a final desired shapepattern made using waxMolten metal
wax
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Exam le of roductExam le of roductproduced by castingproduced by casting
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a asa as
The mould is
made out sandusing a shape
Molten metal
.
Economical!
Sand cast
2-piece mould
Molten metal is placed at one opening
and once the metal is solidified, mouldLarge parts; Automotive
the moulds.cy n er oc s, re
hydrants, large pipe fittings
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To produce high volume products, low melting pointalloys (e.g. Zn, Al and Mg) and small products
Clamped& cooled
Mould ismade out ofmetal (die).
Molten metal is placesin a two-part mouldunder ressure.
The mould canbe opened toeject the
piece (cast piece)
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xamp es o e casxamp es o e cas
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Investment CastinInvestment CastinThis process is capable of producing precise detail and dimensional accuracy inparts weighing many pounds to just a few ounces. Precision investment castingsare able to reduce costs in many cases due to reduced machining and less
material waste.Molten metalplaster of
furnace
wax
poure n emould
par s san
Pattern ismade out of
Mould is madeusing thepattern by
Once cooled,metal part isremoved from
When mould isheated, thewax/plastic burns off
pouring plasterof paris
the mouldleaving a cavity
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ves me asves me as
nves men as ng s su a e or ow vo ume, comp ex s apes
like jewelry, dental crown, turbine blades, weaponry,
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xerc sexerc se
Cite the best method for the production of:Cite the best method for the production of: Gold earGold ear--rin srin s
Pipe connectionPipe connection
Large engine block for a truckLarge engine block for a truck
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..
Miscellaneous
Powder Processing Welding
Materials with low To oint two arts
ductilityOther working
procedures are difficult
together
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ow er e a ur yow er e a ur y
ressure
Micron sized or nanosized metal powders areplaced in a die
Powders
heat
diePressure applied to compact
the powders
areacontact
densify
Uniaxial press
Heat sometimes applied during
point contactat low T
densificationby diffusion at
During heating, particles started to bedensified assist by high temperature
g erand solidify
Finish product will be removed fromthe die
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What would be the advantageWhat would be the advantage
an sa van a es o pow eran sa van a es o pow ermetallurgy?metallurgy?
AdvantagesAdvantages DisadvantagesDisadvantages
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ee
Similar or dissimilar metals can be joined.Similar or dissimilar metals can be joined.Joinin bond is metallur ical not mechanicalJoinin bond is metallur ical not mechanical
Arch, gas welding, soldering and brazingArch, gas welding, soldering and brazing
Done by melting work pieces and adding a filler material to form a
pool of molten material (the weld puddle) that cools to become a
Arc welding refers to a group of welding processes that use a
.
and the base material tomelt themetals at thewelding point.
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ea ec e o eea ec e o e
Workpieces arejoinedbya filler material which isheated toahigh temperature.
This resulted in fusion joint betweenthe2parts
The region adjacent to the weld will experience microstructure and property
alterations.
Heat-affected-zone (HAZ). Knowledge of HAZ is required to make sure the
joiningstays intact andnot failed
fused base metal
filler metal (melted)base metal (melted)
unaffectedunaffectedheat affected zone
p ece p ece
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ee
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ThermalThermal
Processing ofProcessing ofMetalsMetals
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Thermal Processing of MetalsThermal Processing of Metals
Annealing: Heat to high temperature, Tanneal, then cool slowly.
tress e e : e ucestress caused by:
-plastic deformation-nonuniform cooling
p ero ze stee s :Make very soft steels forgood machining. Heat just
below TE
& hold for
Types of
-p ase rans orm.
Full Anneal (steels):Make soft steels for
15-25 h.
Annealing
Process Anneal:
good forming by heatingto get , then cool in
furnace to get coarse P.
ega e e ec ocold working by(recovery/
recrystallization)
Normalize (steels):Deform steel with largegrains, then normalize
.
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Definition:Definition:
material will be heated at high
tem erature leave at thattemperature for a period of time
follow by cooling
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e o s o nnea ne o s o nnea n
1.1. You need an oven (furnace)You need an oven (furnace)2.2. Place the metal samples which you wish to anneal in the ovenPlace the metal samples which you wish to anneal in the oven
3.3. Heat the furnace to desired temperatureHeat the furnace to desired temperature
4.4. Make sure ou use the ri ht heatin rate to aid thermal shockMake sure ou use the ri ht heatin rate to aid thermal shock
5.5. Set the annealing time (i.e. how long you would want to annealSet the annealing time (i.e. how long you would want to anneal
your samples)your samples) -- soakingsoaking
6.6. Once the annealing is done, cool down the furnaceOnce the annealing is done, cool down the furnace
7.7. Make sure the coolin rate is ri htMake sure the coolin rate is ri ht
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easo s o eaeaso s o ea
1. Process annealing heat treatment to negate (counteract)effects of cold work. During cold work, metal suffers severe
deformation (hence it strain-hardens) and with process
annealing, recovery and recrystalisation occurs
2. Internal residual stress formed in metal because of plastic
deformation (machining, grinding) and non-uniform cooling.
.
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orma zorma z
Heat treatment to refine the grains (decrease grain size)
Produces more uniform grains (size and distribution)
trengt o stee a so increases
Heating to temperature > upper critical temperature (see phase diagram)
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Heat treatment of Carbon SteelHeat treatment of Carbon Steel
(Formation of Martensitic Steel)(Formation of Martensitic Steel)
Quench austenite >726
o
C (in water, air or oil) Upon quenching, martensite formed
Cooling is not uniform.
The outer part of the metal will cooled quicker compared
to the inner art
Hardenability property which determines the depth
and distribution of hardness induced by quenching from
It is a parameter which measure the rate at which
hardness drops off the distance into the interior of a
Quenching
spec men as a resu o m n s e mar ens e con en .
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orma o o ar e s eorma o o ar e s e
Austenite
Quenching
of austenite Martensite
ar ens e orme
on the surface
High
hardness
Low
hardness
Hardenability
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Test used to measure
Hardemability Test
ardness,
HRC
20
40
60
specimenflat ground
1
H 0 1 2 3
600A
P
T(C) 0%100%
24C water
phase field)
400
200A M
M(start)
s,HRC
Martensite
Martensite
FinePearlit
earlite0 M(finish)
Hardne
s
Pearlit
e
0.1 1 10 100 1000
Time (s)Distance from quenched end
Heat TreatmentsHeat Treatments
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Heat TreatmentsHeat Treatments
a)a) AnnealingAnnealingT(C)Austenite (stable)
TE
A
c) Tempered 600
P
ar ens e
400
B
AAdapted from Fig. 10.22, Callister 7e.
200M + A
M + A50%
90%
a)
c)
time (s)
10 103
105
10-1
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rec p a o ar erec p a o ar e
Introducing small uniformly dispersed particlesIntroducing small uniformly dispersed particles(second phase) within original phase matrix.(second phase) within original phase matrix.
The small particles are called precipitates andThe small particles are called precipitates and
can be formed by appropriate heat treatmentcan be formed by appropriate heat treatmentThe strengthening processThe strengthening process increased inincreased in
resistance to dislocation motion by latticeresistance to dislocation motion by lattice
strains which are established in the vicinity ofstrains which are established in the vicinity ofsmall precipitated particlessmall precipitated particles
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Preci itation Hardenin ;Preci itation Hardenin ;
example (READ)example (READ)
DuraluminDuralumin isis anan aluminiumaluminium alloyalloy containingcontaining 44wtwt%% copper,copper, asas wellwellasas smallersmaller amountsamounts ofof otherother elementselements.. TheThe impuritiesimpurities inin thethe
andand sincesince thethe distributiondistributionofof thethecoppercopper atomsatoms cancan bebe variedvaried usingusingheatheat treatments,treatments, aavarietyvariety ofof microstructures,microstructures, andand hencehencepropertiesproperties
TheThecoppercopper formsforms precipitatesprecipitates ofof CuAlCuAl22 withinwithin ananaluminiumaluminiummatrixmatrix..eseese precp aesprecp aes n ern er ee movemenmovemen oo soca onssoca ons anan
substantiallysubstantially strengthensstrengthens thethe alloyalloy.. ThisThis processprocess isis widelywidely usedused totomakemake strongstrong aluminiumaluminium alloysalloys forfor structuralstructural purposes,purposes, andand isisnownnown asas precp a onprecp a on ar enngar enng ..
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o ura umo ura um
Discuss how these
precipitates hindersdislocation movement.
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rec p a o ar erec p a o ar e