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 (</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>