Investment Castings
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<p>LATEST TRENDS IN INVESTMENT CASTING TECHNOLOGY</p>
<p>Dr.Ing.Milan Horek,PhD</p>
<p>Brno University of Technology, CZ</p>
<p>PAPER STRUCTUREA/ 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</p>
<p>E/ Accuracy of investment casting technology F/ Capabilities of modern lost wax technology (examples of castings)</p>
<p>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</p>
<p>LOST FOAM</p>
<p>LOST WAX</p>
<p>IIIrd. GENERATION physical binding</p>
<p>B/ BASIC INVESTMENT CASTING PROCESSWax pattern makingDie</p>
<p>Wax pattern assemblyWax pattern</p>
<p>Dipping into ceramic slurry</p>
<p>Wax pattern Gating system</p>
<p>Ceramic coating</p>
<p>Finished shellCeramic shell</p>
<p>De-waxing</p>
<p>Metal pouring</p>
<p>Removal of shell</p>
<p>Casting cut-off</p>
<p>C/ BRIEF HISTORY OF LOST-WAX PROCESS</p>
<p>p.n.l 0 n.lThajsko Mezopotmie Izrael Indie/S.V. Asie Anatlie na Egej / ecko Etrusko Keltsk S. Evropa man Jin/Stedn Amerika Zpadn Afrika Zpadn Evropa Renesann Itlie</p>
<p>5000</p>
<p>4000</p>
<p>3000</p>
<p>2000</p>
<p>1000</p>
<p>0</p>
<p>1000</p>
<p>2000</p>
<p>EXAMPLES OF HISTORICAL CASTINGS</p>
<p>gold comb casting (300g, Dniepr area, 4th cent.A.D.)</p>
<p>bronze head (Benin 12th.cent.A.D.) bronze statue of Perseus with Meduza head (Cellini, 1540)</p>
<p>D/ DESCRIPTION OF INDIVIDUAL PHASES OF INVESTMENT CASTING PROCESS1. WAX PATTERN MANUFACTURE a/ Die manufacture b/ Wax pattern injection c/ Pattern assembly 2. CERAMIC SHELL MANUFACTURE a/ Step-by-step shell building and drying b/ Shell de-waxing c/ Ceramic shell firing 3. METAL POURING a/ On air b/ Under vacuum 4. FINISHING OPERATIONS a/ Gating system removal b/ Surface finish cleaning, blasting, etc.</p>
<p>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 Low melting point alloy Plaster METAL SPRAYING Master die</p>
<p>Low melting point alloy Sn,Bi,Pb,Cd Tmel=70C soft Tmel= 138C hard Master die</p>
<p>GALVANIZATION Low melting point alloy Metal master pattern</p>
<p>Ni,Cu,Fe by galvanization</p>
<p>-By machining from solid metal blocks( the most often used method )</p>
<p>1. WAX PATTERN MANUFACTURE b/ Wax pattern makingWAXES USED Present waxes complex materials containing following components:- natural waxes - syntetic waxes - natural resins - syntetic resins - organic fillers - water TYPES of WAXES - Straight (non-filled)</p>
<p>- Filled (30% of filler) - Emulsified(by water, air)</p>
<p>Combination of different raw materials properties to achieve optimal wax characteristics:-melting and congealing point -hardness -viscosity -expansion/contraction -solidification rate - ash content ( 0,05%) - flexibility - surface quality - stability to oxidation - possibility to recycle</p>
<p>BASIC PRINCIPLE OF INJECTION MACHINE FOR WAX PATTERN MAKING</p>
<p>Valve</p>
<p>Wax storage</p>
<p>Sp (piston surface) Transport wax hose</p>
<p>Piston pump</p>
<p>vcInjection nozzle Piston Injection cylinder with wax Master die</p>
<p>EQUIPMENT FOR WAX PATTERN MAKING injection machine +wax melter + conditioner</p>
<p>INJECTION CYCLESpeed controlled phase1000</p>
<p>Pressure controlled phase</p>
<p>2U (pre-set packing pressure)</p>
<p>3</p>
<p>E die cavity filling time K packing time N holding time Z cycle time (till the die opening)</p>
<p>Pressu re [bar]</p>
<p>NOTE: Points 1, 2, 3, 4 a 5 correspondent to the points in following picture</p>
<p>1a</p>
<p>Die opening</p>
<p>11</p>
<p>4 E K Z N</p>
<p>5</p>
<p>Time</p>
<p>INJECTION CYCLE</p>
<p>1 bar</p>
<p>Specif ic volum [cm3/ g]</p>
<p>1200</p>
<p>1a600 1000</p>
<p>4 3</p>
<p>21500</p>
<p>1 2 pressure increase in die cavity decrease of spec.volume 2 3 packing pressure slight decrease of spec.volume 3 4 pressure decrease during wax solidification constant spec. volume 4 5 wax cooling in die decrease of spec.volume (contraction)</p>
<p>5NOTE:</p>
<p>vSP = 1/ specific volume [cm3/g] = 1/vSP density [g/cm3]</p>
<p>TE</p>
<p>(wax temperature during pattern stripping from die)</p>
<p>TM</p>
<p>(wax temperature during injection)</p>
<p>Temperature [C]</p>
<p>EXAMPLES OF INJECTION MACHINES</p>
<p>WAX PREPARATION FOR INJECTION</p>
<p>EXAMPLES OF WAX PATTERNS</p>
<p>1. MANUFACTURE OF WAX PATTERNS c/ Wax pattern assemblyWax pattern assembliesa) Horizontal placed patterns on a special gating rings</p>
<p>Assembly Design Influenced by:-Technique of pattern assembly (glueing/welding) -Shelling technique -De-waxing technologyb) Patterns straight on gating sprue</p>
<p>-Pouring system -Casting cutting-off technique -Standartization of gating systems</p>
<p>2. MANUFACTURE OF CERAMIC SHELL a/ Shell building and dryingI/ 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)</p>
<p>SLURRY MIXING TANKS</p>
<p>SANDERSRainfall Fluidized bed</p>
<p>ROBOTIZIED SHELLING LINES</p>
<p>FULLY ROBOTIZED SHELLING LINE</p>
<p>2. MANUFACTURE OF CERAMIC SHELL b/ Shell de-waxing</p>
<p>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.</p>
<p>TECHNIQUES USED FOR DE_WAXING I/ By overheated steam in boilerclaves II/ By firing flash fire systemCERAMIC SHELL Thermal expansion WAX PATTERN</p>
<p>III/ By microvave heating</p>
<p>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</p>
<p>Typical working parameters:-Steam temperature 160-170C -Working pressure 6-8 atm -Reaching work.pressure in 4-5 s -Controlled speed of pressure drop</p>
<p>DE-WAXING IN BOILERCLAVE</p>
<p>WAX RECYCLING AFTER ITS DE-WAXING WAX RECYCLINGREMOVAL OF IMPURITIES + NEW WAX ADDITION</p>
<p>AUTOCLAVE</p>
<p>BOILER TANK 16 hours IMPURITIES</p>
<p>STORAGE TANK GEAR PUMP</p>
<p>MASTER DIE</p>
<p>2. MANUFACTURE OF CERAMIC SHELL c/ Shell firingGOAL: transfer of amorphous type of SiO2 binder layer into a crystallic one + removal of volatiles matters (waxes remains)1000900 - 1080 C</p>
<p>90060 80 min</p>
<p>800 700</p>
<p> 5 C/min</p>
<p>Teplota [ C]</p>
<p>600 500 400 5 C/min</p>
<p>575 C</p>
<p>30 min</p>
<p>300 200 100 0 0 60 120 180 240 300 360100 C 30 min</p>
<p>as [min]</p>
<p>DIFFERENT TYPES OF CERAMIC MOULDS MADE BY LOST WAX PROCESSa) SOLID CERAMIC MOULD COMPACT METHOD</p>
<p>CERAMIC SLURRY a) SOLID CERAMIC MOULD COMBINED METHOD</p>
<p>SLURRY SAND (CEMENT)</p>
<p>2-3 SHELLS</p>
<p>c) BACKFILLED SHELL</p>
<p>d) SELF SUPPORTING SHELL</p>
<p>2-3 SHELLS</p>
<p>5-8 SHELLS</p>
<p>POSSIBILITIES OF USING CERAMIC CORES</p>
<p>Ceramic core manufacturing:-Preparation of ceramic mass -Forming into a needed shape -Heat treatment</p>
<p>3. METAL POURING GRAVITYa/ Classical pouring b/ Roll-overpouringGRAVITY POURING</p>
<p>UNDER VACUUMa/ Melting and gravity pouring under vacuum</p>
<p>b/ Counter-gravity pouring (CLA , CLV)POURING UNDER VACUUM</p>
<p>VACUUM</p>
<p>VACUUM</p>
<p>VACUUM</p>
<p>POSSIBILITIES OF MOLTEN METAL FILTRATIONFILTRATION POSSIBILITIES 1.STRAINER CORES 3.EXTRUDED FILTERS</p>
<p>FILTER 2.FOAM FILTERS 4.GLASS FIBRES FILTERS</p>
<p>4. -</p>
<p>FINISHING OPERATIONS casting cut-off from gating system(by vibration , cutting )</p>
<p>casting surface cleaning(by blasting , grinding )</p>
<p>casting heat treatment</p>
<p>5. -</p>
<p>CASTING QUALITY INSPECTION chemical composition, structure(spectrometr, metalography )</p>
<p>internal casting quality(X-ray, ultrasonic )</p>
<p>casting surface finish(capillar methods )</p>
<p>mechanical properties(tensile strength, hardness, ductility, etc. )</p>
<p>dimensional accuracy</p>
<p>E/ DIMENSIONAL ACCURACY OF INVESTMENT CASTINGS</p>
<p>INVESTMENT CASTING PROCESS</p>
<p>(Lost wax process)CASTING TECHNOLOGY A FINAL MACHINING SHOULD BE ELIMINATED NET SHAPE CASTING AS CAST CONDITIONS DIMENSIONAL AND TOLERANCE REQUIREMENTS</p>
<p>is</p>
<p>where</p>
<p>i.e. our goal is to achieve</p>
<p>to be ready for usage in</p>
<p>complying with all</p>
<p>The average tolerance exhibited by various casting processes (by J.Campbell)</p>
<p>THE FINAL CASTINGS DIMENSIONS</p>
<p>dependent on</p>
<p>Dimensional changes during individual stages of investment casting technology INVESTMENT CASTING PROCESS FINAL CASTING DIMENSIONS</p>
<p>PATTERN DIE DIMENSIONS</p>
<p>PATTERN DIE DIMENSIONmust comply with</p>
<p>All subsequent dimensional changes during the processi.e.</p>
<p>PATTERN MAKING SHELLING DE - WAXING SHELL DRYING and FIRING METAL POURING, SOLIDIFICATION and COOLING</p>
<p>DIMENSIONAL CHANGES DURING INVESTMENT CASTING PROCESS</p>
<p>tolerances dimensionc es toler an io n + Dimens</p>
<p>1 2 3 4</p>
<p>Tool cavity Wax pattern Dried shell Fired shell Final casting</p>
<p>S ta g p o e of ces t ss he</p>
<p>1 2 3</p>
<p>4</p>
<p>5</p>
<p>5</p>
<p>DIMENSIONAL ACCURACY OF INVESTMENT CASTINGS</p>
<p>F/ CAPABILITIES OF INVESTMENT CASTING TECHNOLOGY</p>
<p>EXAMPLES OF CASTINGS MADE BY LOST WAX TECHNOLOGYAircraft engine blade equiaxed structure, directional solidification, single crystal - superalloys Ni base, vacuum cast</p>
<p>Superalloys Ni base, vacuum cast -castings for power industry</p>
<p>Part of aircraft engine GE (Boeing 747,767) Ti alloy</p>
<p>EXAMPLES OF CASTINGS MADE BY LOST WAX TECHNOLOGYCasing of tank control system Al alloy</p>
<p>Investment castings for shotgunCr hardenable stainless steel</p>
<p>Part of helicopter V-22 Ti alloy Boeing 777 APU duct- Ti alloy</p>
<p>EXAMPLES OF CASTINGS MADE BY LOST WAX TECHNOLOGY</p>
<p>Typical aluminium investment casting features</p>
<p>EXAMPLES OF CASTINGS MADE BY LOST WAX TECHNOLOGY</p>
<p>Investment vacuum castings for surgical implants ( knee and hip joints) - Ti6Al4V alloys , CoCrMo alloys</p>
<p>EXAMPLES OF ALUMINIUM INVESTMENT CASTINGS</p>
<p>SUBSTITUTION OF ORIGINAL TECHNOLOGY USED BY LOST WAX PROCESS</p>
<p>MACHINING+ WELDING +BENDING Weight 0,5 kg Material Fe alloy</p>
<p>INVESTMENT CASTING Weight 0,2 kg Material AlSi10 Mg</p>
<p>Dimensions 155x55x55 mm Benefit weight+ labour reduction, better part properties</p>
<p>1. part PLAST-2.part Al machined by milling+ screwed together Weight 0,11 kg Material: plast+ Al alloy</p>
<p>Investment castingWeight 0,14 kg Material AlSi10 Mg</p>
<p>dimensions 100x40x30 mm Benefit labour less demanding, increased lifetime and component utility values</p>
<p>MACHINING -GLUEING Weight O,52 kg Material Al alloy</p>
<p>INVESTMENT CASTING Weight 0,32 kg Material: AlCu4 Ti</p>
<p>Dimensions 70x95x110 mm Benefits: labour less demanding, increased component utility values</p>
<p>MACHINING,WELDING Weight 0,15 kg Material Fe alloy</p>
<p>INVESTMENT CASTING Weight 0,03 kg Material AlSi10 Mg</p>
<p>Dimensions 40x40x40 mm Benefits: by 30% less labour demanding, increased part utility value</p>
<p>MACHINING,BENDING, WELDING Weight 0,05 kg Material Al alloy</p>
<p>INVESTMENT CASTING Weight 0,02 kg Material AlSi10 Mg</p>
<p>Dimensions: 55x40x40 mm Benefits: by 35% less labour , increased part utility value</p>
<p>PRESSURE DIE CASTING Weight 0,10 kg Material : Zn alloy</p>
<p>INVESTMENT CASTING Weight 0,04 kg Material: AlSi10 Mg</p>
<p>Dimensions:60x60x25 mm Savings: see next picture</p>
<p>SAND CASTING Weight 0,25 kg Material AlSi10 Mg</p>
<p>INVESTMENT CASTING Weight 0,20 kg Material AlSi10 Mg</p>
<p>Dimensions: 204x100x15 mm Savings: less labour cost and increase of component quality</p>
<p>SAND CASTING Weight - 4,8 kg Material - grey iron</p>
<p>INVESTMENT CASTING Weight 0,8 kg Material - AlSi7 Mg</p>
<p>Dimensions 240x130x40mm Benefit: Labour costs savings</p>
<p>MACHINING Weight of piece for mach. 3,36 kg Material Fe alloy</p>
<p>INVESTMENT CASTING Weight 0,12 kg Material - AlSi10 Mg</p>
<p>Dimensions 220x18 mm Benefit: labour costs savings</p>
<p>SAND CASTING Weight 2,4 kg Material RR 350 ( AlCu5Ni)</p>
<p>INVESTMENT CASTING Weight 1,8 kg Material RR 350 (AlCu5Ni)</p>
<p>Dimensions: 150x150x110 mm Benefits: weight reduction, increase of engine power by app. 15 %</p>
<p>INVESTMENT CASTING AGAINST PRESSURE DIE CASTING ECONOMICAL COMPARISON OF CORNER CASTING</p>
<p>Inv.Cast. (CzCrowns) Die price 1.000 pcs 10.000 pcs 15.000 pcs 30.000 45.000 450.000 675.000</p>
<p>Press.Die (CzCrowns) 460.000 16.000 160.000 240.000</p>
<p>IC(total)</p>
<p>PD(total)</p>
<p>75.000 480.000 705.000</p>
<p>476.000 620.000 700.000</p>
<p>BREAK-EVEN POINT IS app. 15.000 pcs In other words only over this amount of castings is PD technology more economical</p>
<p>AIRCRAFTS WITH MIKRON ENGINES (www.parmatechnik.cz)</p>
<p>SAND CASTING Weight 8,7 kg (45 kg) Material. Fe alloy</p>
<p>INVESTMENT CASTING Weight 2,7 kg Material:AlSi7 Mg T6</p>
<p>Dimensions: 260x260x100 mm Savings: on material and labour</p>
<p>SAND CASTING Weight 0,9 kg Material Fe alloy</p>
<p>INVESTMENT CASTING Weight 0,4 kg Material AlSi7 Mg T6</p>
<p>Dimensions 150x80x60 mm Benefit: weight reduction and less labour during machining</p>
<p>Customer: Tadiran Communications Title: Body 9004 Dimensions: 234 x 318 x 201 mm Material: A 356 Weight: 3,5 Kg</p>
<p>Customer: BMT Title: Support Dimensions: 190 x 301 x 240 mm Material: A 356 Weight: 1,33 Kg</p>
<p>Customer: Borcad Title: Rack Dimensions: 304 x 337 x 57 mm Material: A356 Weight: 0,82 Kg</p>
<p>Customer: Uniplet Title: Cover Dimensions: 209 x 360 x 118 mm Material: A356 Weight: 1,25 Kg</p>
<p>Customer: Wyman-Gordon Dimensions: 518 x 147 x 32 mm</p>
<p>Title: Ramback side Material: A 357</p>
<p>Weight: 1,38 Kg</p>
<p>THANK YOU FOR YOUR ATTENTION HAVE A NICE DAY !</p>
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