latest trends investment casting technology
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latest trends - investment casting technologyTRANSCRIPT
LATEST TRENDS IN INVESTMENT CASTING TECHNOLOGY
Dr.Ing.Milan Horáček,PhD Brno University of Technology, CZ
PAPER STRUCTURE
A/ Survey of foundry technologies available for casting manufacture
B/ Basic principles of lost wax process – investment casting
C/ Brief history of the investment casting technology
D/ Description of individual investment casting process phases - wax pattern manufacture- ceramic shell manufacture- de-waxing- shell heat treatment- metal pouring- finishing operations
E/ Accuracy of investment casting technology
F/ Capabilities of modern lost wax technology (examples of castings)
A/ SURVEY OF CASTING TECHNOLOGIES USING SAND MOULDING
Ist . GENERATION - clay binders
IInd. GENERATION – chemical binding
a/ Self-hardening processes (plaster,cement,sodium silicate,resin)
b/ External hardening processes (sodium silicate, resin)
c/ Ceramic moulds (mould firing before pouring)
1. Permanent pattern 2. „Lost“ pattern
LOST WAXLOST FOAM
IIIrd. GENERATION – physical binding
B/ BASIC INVESTMENT CASTING PROCESSWax pattern making Wax pattern assembly Dipping into ceramic
slurry
Ceramic coating Finished shell De-waxing
Metal pouring Removal of shell Casting cut-off
Die
Wax pattern
Gating system
Ceramic shell
Wax pattern
C/ BRIEF HISTORY OF LOST-WAX PROCESS
Thajsko Mezopotámie Izrael Indie/S.V. Asie Anatólie Čína Egej / Řecko Etrusko Keltská S. Evropa Římané Jižní/Střední Amerika Západní Afrika Západní Evropa Renesanční Itálie
5000 4000 3000 2000 1000 0 1000 2000p.n.l – 0 – n.l
EXAMPLES OF HISTORICAL CASTINGS
gold comb casting(300g, Dniepr area, 4th cent.A.D.)
bronze head (Benin – 12th.cent.A.D.)
bronze statue of Perseus with Meduza head(Cellini, 1540)
D/ DESCRIPTION OF INDIVIDUAL PHASES OF INVESTMENT CASTING PROCESS
1. WAX PATTERN MANUFACTURE
a/ Die manufactureb/ Wax pattern injectionc/ Pattern assembly
2. CERAMIC SHELL MANUFACTURE
a/ Step-by-step shell building and dryingb/ Shell de-waxingc/ Ceramic shell firing
3. METAL POURING
a/ On airb/ Under vacuum
4. FINISHING OPERATIONS
a/ Gating system removalb/ Surface finish cleaning, blasting, etc.
1. WAX PATTERN MANUFACTURE
a/ Master die making
-Using master pattern(using low-melt point alloys, by metal spraying, by galvanization)
Master pattern
Sand mould
Plaster
Low melting point alloySn,Bi,Pb,CdTmel=70°CsoftTmel= 138°Chard
Master die
METAL SPRAYINGMaster die
Low melting point alloy
GALVANIZATIONLow melting point alloyMetal master pattern
Ni,Cu,Feby galvanization
-By machining from solid metal blocks( the most often used method )
1. WAX PATTERN MANUFACTUREb/ Wax pattern making
WAXES USED
Present waxes – complex materials containingfollowing components:
- natural waxes TYPES of WAXES- syntetic waxes- natural resins - Straight (non-filled)- syntetic resins - Filled (30% of filler)- organic fillers - Emulsified- water (by water, air)
Combination of different raw materials properties to achieve optimal wax characteristics:-melting and congealing point - ash content (‹ 0,05%)-hardness - flexibility-viscosity - surface quality-expansion/contraction - stability to oxidation-solidification rate - possibility to recycle
BASIC PRINCIPLE OF INJECTION MACHINE FOR WAX PATTERN MAKING
vc
Piston
Piston pump
Master die
Injection nozzle
Transport wax hose
Injection cylinder with wax
Valve
Sp (piston surface)
Wax storage
EQUIPMENT FOR WAX PATTERN MAKING –injection machine +wax melter + conditioner
INJECTION CYCLE
τNτK
τZ
τE
1
1a
32
4 5
U (pre-setpackingpressure)
Pressurecontrolledphase
Die opening
Speed controlled phase
Pressure
[bar]
τE …die cavity filling timeτK …packing timeτN …holding timeτZ …cycle time
(till the die opening)
1
1000
Time
NOTE:Points 1, 2, 3, 4 a 5 correspondent to the points in following picture
INJECTION CYCLE
TM (wax temperature during injection)TE (wax temperature during pattern stripping from die)
1 bar
600
1500
200
1000
Specific
volum[cm3/
g]
1 – 2 …pressure increase in die cavity → decrease of spec.volume2 – 3 …packing pressure →slight decrease of spec.volume3 – 4 …pressure decrease during wax solidification → constantspec. volume4 – 5 …wax cooling in die →decrease of spec.volume(contraction)
Temperature [ºC]
NOTE:vSP = 1/ρ …specific volume [cm3/g]ρ = 1/vSP …density [g/cm3]
1
1a
23
4
5
EXAMPLES OF INJECTION MACHINES
WAX PREPARATION FOR INJECTION
EXAMPLES OF WAX PATTERNS
1. MANUFACTURE OF WAX PATTERNSc/ Wax pattern assembly
b) Patterns straight on gating sprue
Wax pattern assembliesa) Horizontal placed patterns on a special
gating rings
Assembly Design Influenced by:
-Technique of pattern assembly (glueing/welding)
-Shelling technique
-De-waxing technology
-Pouring system
-Casting cutting-off technique
-Standartization of gating systems
2. MANUFACTURE OF CERAMIC SHELLa/ Shell building and drying
I/ DEGREASING OF WAX PATTERNS(removal of remaining separator from the wax pattern surface)
II/ DIPPING INTO CERAMIC SLURRY(ceramic slurry consists of filler and binder)
Filler – heat resistant ceramic flour (fused silica,molochite,zircon,..)Binder – colloidal silica sols based on alcohol (alcosols) or water (hydrosols)
III/ SHELL DRAINING
IV/ STUCCO APPLIED WITH CERAMIC GRIT( fluid or rainfall systems)
Stucco materials – silica, molochite, alumina, zircon, atd. Grain size according to the coat number :
- first 1-2 „prime coats“ fine particles –0,175-0,25 mm (CASTING SURFACE FINISH)- next 3- x „back-up coats“ coarser – 0,25-0,5 mm (MOULD GAS PERMEABILITY)
V/ SHELL DRYING(in aircondition room 2-4hours – temp. 20 °C ±1 °C , relative humidity 30-60% -according to the type of binder used, sufficient air flow)
VI/ REPEATING ( II – V)(till the needed number of coats – 8-12)
SLURRY MIXING TANKS
SANDERSRainfall Fluidized bed
ROBOTIZIED SHELLING LINES
FULLY ROBOTIZED SHELLING LINE
2. MANUFACTURE OF CERAMIC SHELL
b/ Shell de-waxing
KEY PROBLEM : different wax and shell expansion !Wax expansion bigger,therefore danger of shell cracking during de-wax process.
NECCESITY of „dilatation gap“ building on wax pattern surface –through THERMAL SHOCK – see picture bellow.
CERAMIC SHELL
WAX PATTERN
Thermal expansion
TECHNIQUES USED FOR DE_WAXING
I/ By overheated steam – in boilerclaves
II/ By firing – „flash fire“ system
III/ By microvave heating
2. MANUFACTURE OF CERAMIC SHELL
b/ Shell de-waxing
Majority foundries use boilerclave systemMAIN REASONS:-Ideal steam properties for heat transfer-Easy to collect de-waxed wax-High efficiency
Typical working parameters:-Steam temperature – 160-170°C-Working pressure – 6-8 atm-Reaching work.pressure in 4-5 s-Controlled speed of pressure drop
DE-WAXING IN BOILERCLAVE
WAX RECYCLING AFTER ITS DE-WAXING
WAX RECYCLING
AUTOCLAVE
BOILER TANK
REMOVAL OF IMPURITIES + NEW WAX ADDITION
GEAR PUMP
MASTERDIE
16 hours
IMPURITIES
STORAGE TANK
2. MANUFACTURE OF CERAMIC SHELL
c/ Shell firing
GOAL: transfer of amorphous type of SiO2 binder layer into a crystallic one +removal of volatiles matters (waxes remains)
0
100
200
300
400
500
600
700
800
900
1000
0 60 120 180 240 300 360
Čas [min]
Tepl
ota
[ ºC]
575 ºC
60 – 80 min
900 - 1080 ºC
100 ºC
30 min
30 min
≈ 5 ºC/min
≈ 5 ºC/min
DIFFERENT TYPES OF CERAMIC MOULDS MADE BY LOST WAX PROCESSa) SOLID CERAMIC MOULD – COMPACT METHOD
a) SOLID CERAMIC MOULD – COMBINED METHOD
CERAMIC SLURRY
SLURRY SAND(CEMENT)
2-3 SHELLS
d) SELF SUPPORTING SHELLc) BACKFILLED SHELL
2-3 SHELLS 5-8 SHELLS
POSSIBILITIES OF USING CERAMIC CORES
Ceramic core manufacturing:
-Preparation of ceramic mass
-Forming into a needed shape
-Heat treatment
3. METAL POURING
UNDER VACUUMGRAVITY
a/ Classical pouringb/ „Roll-over“pouring
a/ Melting and gravity pouring under vacuumb/ Counter-gravity pouring (CLA , CLV)
GRAVITY POURING POURING UNDER VACUUM
VACUUM VACUUM
VACUUM
POSSIBILITIES OF MOLTEN METAL FILTRATION
FILTRATION POSSIBILITIES
1.STRAINER CORES
2.FOAM FILTERS 4.GLASS FIBRES FILTERS
3.EXTRUDED FILTERS
FILTER
4. FINISHING OPERATIONS
- casting cut-off from gating system(by vibration , cutting )
- casting surface cleaning(by blasting , grinding )
- casting heat treatment
5. CASTING QUALITY INSPECTION
- chemical composition, structure(spectrometr, metalography )
- internal casting quality(X-ray, ultrasonic )
- casting surface finish(capillar methods )
- mechanical properties(tensile strength, hardness, ductility, etc. )
- dimensional accuracy
E/ DIMENSIONAL ACCURACY OF INVESTMENT CASTINGS
INVESTMENT CASTING PROCESS(Lost wax process) is
whereCASTING TECHNOLOGY
i.e. our goal is to achieveA FINAL MACHINING SHOULDBE ELIMINATED
to be ready for usage inNET – SHAPE CASTING
complying with allAS CAST CONDITIONS
DIMENSIONAL AND TOLERANCEREQUIREMENTS
The average tolerance exhibited by various casting processes (by J.Campbell)
THE FINAL CASTING’SDIMENSIONS
Dimensional changes during individual stages of investment casting technology
dependent on
PATTERNDIE
DIMENSIONS
INVESTMENTCASTINGPROCESS
FINAL CASTING
DIMENSIONS
PATTERN DIE DIMENSIONmust comply with
All subsequent dimensional changes during the processi.e.
PATTERN MAKING
SHELLING
DE - WAXING
SHELL DRYING and FIRING
METAL POURING, SOLIDIFICATION and COOLING
DIMENSIONAL CHANGES DURING INVESTMENT CASTING PROCESS
dimensiontolerances
Dim
ensi
onD
imen
sion
+
+ tol
eran
ces
tole
rance
s
StageStage ofof thethepocessspocesss
1 2 34 5
1 Tool cavity
2 Wax pattern
3 Dried shell
4 Fired shell
5 Final casting
DIMENSIONAL ACCURACY OF INVESTMENT CASTINGS
F/ CAPABILITIES OF INVESTMENT CASTING TECHNOLOGY
EXAMPLES OF CASTINGS MADE BY LOST WAX TECHNOLOGYAircraft engine blade – equiaxed structure, directional solidification,
single crystal - superalloys Ni base, vacuum cast
Superalloys Ni base, vacuum cast-castings for power industry
Part of aircraft engine GE (Boeing 747,767) – Ti alloy
EXAMPLES OF CASTINGS MADE BY LOST WAX TECHNOLOGY
Casing of tank control system – Al alloy
Part of helicopter V-22 – Ti alloyInvestment castings for shotgun-Cr hardenable stainless steel
Boeing 777 APU duct- Ti alloy
EXAMPLES OF CASTINGS MADE BY LOST WAX TECHNOLOGY
Typical aluminium investment casting features
EXAMPLES OF CASTINGS MADE BY LOST WAX TECHNOLOGY
Investment vacuum castings for surgical implants ( knee and hip joints)- Ti6Al4V alloys , CoCrMo alloys
EXAMPLES OF ALUMINIUM INVESTMENT CASTINGS
SUBSTITUTION OF ORIGINAL TECHNOLOGY USEDBY LOST WAX PROCESS
MACHINING+ WELDING+BENDING
INVESTMENT CASTING
Weight 0,5 kg Weight 0,2 kg
Material – Fe alloy Material – AlSi10 Mg
Dimensions 155x55x55 mm
Benefit – weight+ labour reduction, better part properties
1. part PLAST-2.part Al machined by milling+ screwed
together
Investment casting
Weight 0,11 kg Weight 0,14 kg
Material: plast+ Al alloy Material AlSi10 Mg
dimensions 100x40x30 mm
Benefit – labour less demanding, increased lifetime and component utility values
MACHINING -GLUEING INVESTMENT CASTING
Weight O,52 kg Weight 0,32 kg
Material – Al alloy Material: AlCu4 Ti
Dimensions 70x95x110 mm
Benefits: labour less demanding, increased component utility values
MACHINING,WELDING INVESTMENT CASTING
Weight 0,15 kg Weight 0,03 kg
Material – Fe alloy Material – AlSi10 Mg
Dimensions 40x40x40 mm
Benefits: by 30% less labour demanding, increased part utility value
MACHINING,BENDING, WELDING
INVESTMENT CASTING
Weight 0,05 kg Weight 0,02 kg
Material – Al alloy Material – AlSi10 Mg
Dimensions: 55x40x40 mm
Benefits: by 35% less labour , increased part utility value
PRESSURE DIE CASTING INVESTMENT CASTING
Weight 0,10 kg Weight 0,04 kg
Material : Zn alloy Material: AlSi10 Mg
Dimensions:60x60x25 mm
Savings: see next picture
SAND CASTING INVESTMENT CASTING
Weight 0,25 kg Weight 0,20 kg
Material – AlSi10 Mg Material – AlSi10 Mg
Dimensions: 204x100x15 mm
Savings: less labour cost and increase of component quality
SAND CASTING INVESTMENT CASTING
Weight - 4,8 kg Weight – 0,8 kg
Material - grey iron Material - AlSi7 Mg
Dimensions 240x130x40mm
Benefit: Labour costs savings
MACHINING INVESTMENT CASTING
Weight of piece for mach. 3,36 kg Weight 0,12 kg
Material – Fe alloy Material - AlSi10 Mg
Dimensions Ø 220x18 mm
Benefit: labour costs savings
SAND CASTING INVESTMENT CASTING
Weight 2,4 kg Weight 1,8 kg
Material RR 350 ( AlCu5Ni) Material RR 350 (AlCu5Ni)
Dimensions: 150x150x110 mm
Benefits: weight reduction, increase of engine power by app. 15 %
INVESTMENT CASTING AGAINSTPRESSURE DIE CASTING
• ECONOMICAL COMPARISON OF „CORNER“ CASTING
Inv.Cast. (CzCrowns)
Press.Die (CzCrowns)
IC(total) PD(total)
Die price 30.000 460.000
1.000 pcs 45.000 16.000 75.000 476.000
10.000 pcs 450.000 160.000 480.000 620.000
15.000 pcs 675.000 240.000 705.000 700.000
BREAK-EVEN POINT IS app. 15.000 pcs
In other words only over this amount of castings is PD technology more economical
AIRCRAFTS WITH „MIKRON“ ENGINES (www.parmatechnik.cz)
SAND CASTING INVESTMENT CASTING
Weight 8,7 kg (45 kg) Weight 2,7 kg
Material. Fe alloy Material:AlSi7 Mg T6
Dimensions: 260x260x100 mm
Savings: on material and labour
SAND CASTING INVESTMENT CASTING
Weight 0,9 kg Weight 0,4 kg
Material – Fe alloy Material AlSi7 Mg T6
Dimensions 150x80x60 mm
Benefit: weight reduction and less labour during machining
Customer:
TadiranCommunications
Title:
Body 9004
Dimensions:
234 x 318 x 201 mm
Material:
A 356
Weight:
3,5 Kg
Customer:
BMT
Title:
Support
Dimensions:
190 x 301 x 240 mm
Material:
A 356
Weight:
1,33 Kg
Customer:
Borcad
Title:
Rack
Dimensions:
304 x 337 x 57 mm
Material:
A356
Weight:
0,82 Kg
Customer:
Uniplet
Title:
Cover
Dimensions:
209 x 360 x 118 mm
Material:
A356
Weight:
1,25 Kg
Title:
Ramback side
Material:A 357
Customer:
Wyman-Gordon
Dimensions:
518 x 147 x 32 mm
Weight:
1,38 Kg
THANK YOU FOR YOUR ATTENTION
HAVE A NICE DAY !