EP1785205B1 - Verfahren und Einrichtung zur Verbindung von keramische und metallkerne im Feingiessverfahren - Google Patents

Verfahren und Einrichtung zur Verbindung von keramische und metallkerne im Feingiessverfahren Download PDF

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Publication number
EP1785205B1
EP1785205B1 EP06254846A EP06254846A EP1785205B1 EP 1785205 B1 EP1785205 B1 EP 1785205B1 EP 06254846 A EP06254846 A EP 06254846A EP 06254846 A EP06254846 A EP 06254846A EP 1785205 B1 EP1785205 B1 EP 1785205B1
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EP
European Patent Office
Prior art keywords
casting core
core
ceramic
slurry
metallic
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EP06254846A
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English (en)
French (fr)
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EP1785205A1 (de
Inventor
Carl R. Verner
Michael K. Turkington
Mark F. Bartholomew
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Raytheon Technologies Corp
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United Technologies Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/10—Cores; Manufacture or installation of cores
    • B22C9/103—Multipart cores
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
    • B22C1/18—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents
    • B22C1/183—Sols, colloids or hydroxide gels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/02—Sand moulds or like moulds for shaped castings
    • B22C9/04—Use of lost patterns
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/12—Treating moulds or cores, e.g. drying, hardening

Definitions

  • the invention relates to investment casting. More particularly, the invention relates to investment casting core assemblies.
  • Investment casting is commonly used in the aerospace industry. Various examples involve the casting of gas turbine engine parts. Exemplary parts include various blades, vanes, seals, and combustor panels. Many such parts are cast with cooling passageways. The passageways may be formed by sacrificial casting cores.
  • Exemplary cores include ceramic cores, refractory metal cores (RMCs), and combinations thereof.
  • the ceramic cores may form feed passageways whereas the RMCs form cooling passageways extending from the feed passageways through walls of the associated part.
  • the cores may be assembled to each other and secured with a ceramic adhesive.
  • An exemplary ceramic adhesive is alumina-based.
  • the adhesive may comprise alumina powder and a binder such as colloidal silica.
  • the casting shell and core(s) are destructively removed.
  • Exemplary shell removal is principally mechanical.
  • Exemplary core removal is principally chemical.
  • the cores may be removed by chemical leaching.
  • Exemplary leaching involves use of an alkaline solution in an autoclave. Exemplary leaching techniques are disclosed in US Patents 4,141,781 , 6,241,000 , and 6,739,380 .
  • one aspect of the invention involves a method for attaching a metallic casting core to a ceramic casting core.
  • An insertion portion of the metallic casting core is inserted into a receiving portion of the ceramic casting core.
  • a slurry is introduced between the metallic casting core and the ceramic casting core.
  • the metallic casting core and ceramic casting core are vibrated during the introducing.
  • the metallic casting core may comprise a refractory metal-based substrate (e.g., optionally coated).
  • the method may be used to form a turbine blade core assembly or a turbine vane core assembly.
  • the slurry may be heated to harden.
  • the inserting may be performed with the ceramic casting core in a green state.
  • the slurry may comprise zircon and aqueous colloidal silica.
  • the apparatus has a fixture comprising means for holding a ceramic casting core.
  • the fixture also has means for holding a metallic casting core with an insertion portion received in a receiving portion of the ceramic casting core.
  • the apparatus has means for vibrating the fixture.
  • the means for holding may include means for adjusting relative position of the ceramic casting core and metallic casting core.
  • the binders of ceramic adhesives may have adverse reactions with additional items such as refractory metal cores.
  • a specialized slurry has been developed to secure cores based upon shelling slurries.
  • the exemplary slurry consists essentially of a combination of: zircon and aqueous colloidal silica in a 79:21 weight ratio; a surfactant; and sufficient additional water to achieve the desired viscosity.
  • Exemplary ranges for the zircon to colloidal silica ratio are 70:30 through 80:20.
  • An exemplary surfactant is essentially a linear alcohol-based surfactant available from Solvay Chemicals, Inc. of Houston, Texas under the trademark ANTAROX BL 225.
  • An exemplary surfactant amount is 0.05-0.15%, by volume, more narrowly under 0.1% such as 0.7-0.9%.
  • An optional additive is polydimethyl siloxanes (available from Hydrolabs, Inc. of Wayne, New Jersey under the trademark BURST RSD-10) in a small amount (e.g., 0.005-0.015%, by volume) to aid in bubble rupture.
  • the exemplary slurry has a density in the range of 2.87-2.96g/cm 3 .
  • the exemplary slurry has a pH in the range of 9.0-10.5.
  • the exemplary slurry has a viscosity of 25 (+/-2) centiPoise (cP).
  • cP centiPoise
  • other viscosities may be appropriate for particular situations, especially thinner slurries (e.g., 18-27 cP, more particularly 18-25cP).
  • FIG. 1 shows an exemplary method 20 for forming an investment casting mold.
  • One or more metallic core elements are formed 22 (e.g., of refractory metals such as molybdenum and niobium by stamping or otherwise cutting from sheet metal) and coated 24.
  • Suitable coating materials include silica, alumina, zirconia, chromia, mullite and hafnia.
  • the coefficient of thermal expansion (CTE) of the refractory metal and the coating are similar.
  • Coatings may be applied by any appropriate line-of sight or non-line-of sight technique (e.g., chemical or physical vapor deposition (CVD, PVD) methods, plasma spray methods, electrophoresis, and sol gel methods). Individual layers may typically be 0.1 to 1 mil (0.0025-0.025 mm) thick. Layers of Pt, other noble metals, Cr, Si, W, and/or Al, or other non-metallic materials may be applied to the metallic core elements for oxidation protection in combination with a ceramic coating for protection from molten metal erosion and dissolution.
  • CVD chemical or physical vapor deposition
  • PVD physical vapor deposition
  • One or more ceramic cores may also be formed 26 (e.g., of or containing silica in a molding and firing process).
  • One or more of the coated metallic core elements (hereafter refractory metal cores (RMCs)) are assembled 28 to one or more of the ceramic cores.
  • RMCs refractory metal cores
  • the assembly may include use of a ceramic slurry discussed below.
  • the core assembly is then overmolded 30 with an easily sacrificed material such as a natural or synthetic wax (e.g., via placing the assembly in a mold and molding the wax around it). There may be multiple such assemblies involved in a given mold.
  • the overmolded core assembly (or group of assemblies) forms a casting pattern with an exterior shape largely corresponding to the exterior shape of the part to be cast.
  • the pattern may then be assembled 32 to a shelling fixture (e.g., via wax welding between end plates of the fixture).
  • the pattern may then be shelled 34 (e.g., via one or more stages of slurry dipping, slurry spraying, or the like).
  • the drying provides the shell with at least sufficient strength or other physical integrity properties to permit subsequent processing.
  • the shell containing the invested core assembly may be disassembled 38 fully or partially from the shelling fixture and then transferred 40 to a dewaxer (e.g., a steam autoclave).
  • a dewaxer e.g., a steam autoclave
  • a steam dewax process 42 removes a major portion of the wax leaving the core assembly secured within the shell.
  • the shell and core assembly will largely form the ultimate mold.
  • the dewax process typically leaves a wax or byproduct hydrocarbon residue on the shell interior and core assembly.
  • the shell is transferred 44 to a furnace (e.g., containing air or other oxidizing atmosphere) in which it is heated 46 to strengthen the shell and remove any remaining wax residue (e.g., by vaporization) and/or converting hydrocarbon residue to carbon.
  • Oxygen in the atmosphere reacts with the carbon to form carbon dioxide. Removal of the carbon is advantageous to reduce or eliminate the formation of detrimental carbides in the metal casting. Removing carbon offers the additional advantage of reducing the potential for clogging the vacuum pumps used in subsequent stages of operation.
  • the mold may be removed from the atmospheric furnace, allowed to cool, and inspected 48.
  • the mold may be seeded 50 by placing a metallic seed in the mold to establish the ultimate crystal structure of a directionally solidified (DS) casting or a single-crystal (SX) casting. Nevertheless the present teachings may be applied to other DS and SX casting techniques (e.g., wherein the shell geometry defines a grain selector) or to casting of other microstructures.
  • the mold may be transferred 52 to a casting furnace (e.g., placed atop a chill plate in the furnace).
  • the casting furnace may be pumped down to vacuum 54 or charged with a non-oxidizing atmosphere (e.g., inert gas) to prevent oxidation of the casting alloy.
  • the casting furnace is heated 56 to preheat the mold. This preheating serves two purposes: to further harden and strengthen the shell; and to preheat the shell for the introduction of molten alloy to prevent thermal shock and premature solidification of the alloy.
  • the molten alloy is poured 58 into the mold and the mold is allowed to cool to solidify 60 the alloy (e.g., after withdrawal from the furnace hot zone).
  • the vacuum may be broken 62 and the chilled mold removed 64 from the casting furnace.
  • the shell may be removed in a deshelling process 66 (e.g., mechanical breaking of the shell).
  • the core assembly is removed in a decoring process 68 to leave a cast article (e.g., a metallic precursor of the ultimate part).
  • a cast article e.g., a metallic precursor of the ultimate part.
  • the cast article may be machined 70, chemically and/or thermally treated 72 and coated 74 to form the ultimate part. Some or all of any machining or chemical or thermal treatment may be performed before the decoring.
  • FIG. 2 shows details of an apparatus 200 for assembling the cores.
  • the apparatus includes a shake table 202 for vibrating the assemblies. Each assembly is held by a fixture 204 atop the shake table.
  • Exemplary assemblies ( FIG. 3 ) are of molded ceramic feedcores 210 and refractory sheet trailing edge slot RMCs 212.
  • FIG. 3 shows further details of the exemplary fixtures 204.
  • the fixtures include a base 220 for mounting to the shake table.
  • the fixture includes features for holding an associated feedcore 210. These features may include a plurality of tooling balls 222 precisely fixed on the base to engage the feedcore 210.
  • a clamp 224 may be mounted on the base to engage the feedcore after the feedcore is placed against the tooling balls.
  • a pivotal retaining bar 230 may be positioned to engage a root portion of the feedcore to retain the feedcore in position.
  • the fixture includes features for holding an associated RMC 212 relative to the associated feedcore.
  • a leading end portion of the RMC is inserted within a slot in a trailing leg of the feedcore.
  • the RMC-holding features may include a clamp 240 grasping a trailing end portion of the RMC.
  • the clamp may be mounted to a gantry structure 242.
  • the exemplary gantry structure is slidably mounted for movement along a direction 500.
  • the gantry (and thus the RMC) position may be controlled by a micrometer mechanism 250.
  • the exemplary micrometer mechanism biases the gantry against the root end of the feedcore to provide fine adjustment of the position of the RMC along the feedcore.
  • a bead of the slurry may be applied 302 to their joint. Vibration 304 with the shake table may cause the slurry to infiltrate the joint. After infiltration, the slurry may be allowed to dry 306.
  • the slurry application may be performed with the feedcore in a green state. Therafter, the core assembly may be removed 308 and fired 310 to cure the feedcore. The firing may also further harden the slurry to more strongly attach the cores. The firing may be separate from or coincident with the shell firing previously described.
  • the slurry has a viscosity effective to facilitate its shake-assisted infiltration into the joint.
  • the drying shrinkage should not be so great as to risk mechanical failure.
  • the coefficient of thermal expansion should be effective to maintain engagement during the heatings associated with firing and casting. The exemplary properties and composition discussed above are believed particularly effective.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Materials Engineering (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)

Claims (11)

  1. Verfahren zum Befestigen eines metallischen Gusskerns (212) an einem keramischen Gusskern (210), aufweisend:
    Einfügen eines Einfiigeberaichs des metallischen Gusskems (212) in einen Aufnahmebereich des keramischen Gusskems (210);
    Einbringen einer Gießmasse zwischen den metallischen Gusskern (212) und den keramischen Gusskem (210); und gekennzeichnet durch
    Rütteln des metallischen Gusskems (212) und des keramischen Gusskerns (210) während des Einbringens.
  2. Verfahren nach Anspruch 1, bei dem:
    der metallische Gusskern (212) ein Substrat auf der Basis eines schwerschmelzenden Metalls aufweist.
  3. Verfahren nach Anspruch 1 oder 2, das zur Herstellung einer Turbinenlaufschaufel-Kernanordnung oder einer Turbinenleitschaufel-Kemanordnung verwendet wird.
  4. Verfahren nach einem vorangehenden Anspruch, bei dem:
    das Einfügen mit dem keramischen Gusskern (210), der sich in einem Grünzustand befindet, durchgeführt wird.
  5. Verfahren nach einem vorangehenden Anspruch, bei dem die Gießmasse Zirkon und wässriges kolloidales Siliziumdioxid aufweist.
  6. Verfahren nach Anspruch 4, bei dem:
    die Gießmasse einen Gehalt an wässrigem kolloidalen Siliziumdioxid von 20 bis 30 Gew% eines Zirkongehalts hat.
  7. Verfahren nach einem vorangehenden Anspruch, bei dem:
    die Gießmasse ein grenzflächenaktives Mittel aufweist.
  8. Verfahren nach einem vorangehenden Anspruch, bei dem die Gießmasse hat:
    eine Dichte von 2,87 bis 2,96 g/cm3;
    einen pH von 9 bis 10,5; und
    eine Viskosität von 25 +/- 2 cP.
  9. Verfahren nach einem der Ansprüche 1 bis 7, bei dem die Gießmasse hat:
    eine Dichte von 2,87 bis 2,96 g/cm3;
    einen pH von 9 bis 10,5; und
    eine Viskosität von 18 bis 27 cP.
  10. Vorrichtung (200) aufweisend:
    eine Festhaltevorrichtung (204) aufweisend Mittel (222) zum Halten eines keramischen Gusskerns (210) und Mittel (240) zum Halten eines metallischen Gu;skerns (212), wobei ein Einfügebereich in einem Aufnahmebereich des keramischen Gusskerns (210) aufgenommen ist; und
    Mittel (202) zum Rütteln der Festhaltevorrichtung (204).
  11. Vorrichtung nach Anspruch 10, bei der die Mittel zum Halten des metallischen Gusskerns aufweisen:
    Mittel (250) zum Anpassen einer relativen Position des keramischen Gusskerns (210) und des metallischen Gusskerns (212).
EP06254846A 2005-09-28 2006-09-21 Verfahren und Einrichtung zur Verbindung von keramische und metallkerne im Feingiessverfahren Active EP1785205B1 (de)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US11/237,322 US20070068649A1 (en) 2005-09-28 2005-09-28 Methods and materials for attaching ceramic and refractory metal casting cores

Publications (2)

Publication Number Publication Date
EP1785205A1 EP1785205A1 (de) 2007-05-16
EP1785205B1 true EP1785205B1 (de) 2011-08-03

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US (1) US20070068649A1 (de)
EP (1) EP1785205B1 (de)
JP (1) JP2007090434A (de)
KR (1) KR20070035941A (de)
CN (1) CN1939617A (de)
IL (1) IL176624A0 (de)

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ITMI20071148A1 (it) 2007-06-05 2008-12-06 Getters Spa Batterie ricaricabili al litio comprendenti mezzi in forma di foglio polimerico multistrato per l'assorbimento di sostanze nocive
US9403208B2 (en) 2010-12-30 2016-08-02 United Technologies Corporation Method and casting core for forming a landing for welding a baffle inserted in an airfoil
US8302668B1 (en) 2011-06-08 2012-11-06 United Technologies Corporation Hybrid core assembly for a casting process
US8291963B1 (en) 2011-08-03 2012-10-23 United Technologies Corporation Hybrid core assembly
WO2015060989A1 (en) * 2013-10-24 2015-04-30 United Technologies Corporation Lost core molding cores for forming cooling passages
PL3086893T3 (pl) 2013-12-23 2020-01-31 United Technologies Corporation Rama konstrukcyjna z traconym rdzeniem
US10639705B2 (en) * 2016-12-23 2020-05-05 Fisher Controls International Llc Combined technology investment casting process

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US4141781A (en) * 1977-10-06 1979-02-27 General Electric Company Method for rapid removal of cores made of βAl2 O3 from directionally solidified eutectic and superalloy and superalloy materials
US4352390A (en) * 1978-12-04 1982-10-05 Sherwood Refractories, Inc. Precision silica cones for sand casting of steel and iron alloys
US4273182A (en) * 1979-12-07 1981-06-16 Ford Motor Company Core assembly and the method of making and using such assembly
US4981167A (en) * 1989-11-30 1991-01-01 Steve Anderson Method of forming products by low turbulence, uniform cross section investment casting
US5296308A (en) * 1992-08-10 1994-03-22 Howmet Corporation Investment casting using core with integral wall thickness control means
US6241000B1 (en) * 1995-06-07 2001-06-05 Howmet Research Corporation Method for removing cores from castings
US6637500B2 (en) * 2001-10-24 2003-10-28 United Technologies Corporation Cores for use in precision investment casting
US6739380B2 (en) * 2002-04-11 2004-05-25 Rolls-Royce Corporation Method and apparatus for removing ceramic material from cast components
US20050087319A1 (en) * 2003-10-16 2005-04-28 Beals James T. Refractory metal core wall thickness control
US6929054B2 (en) * 2003-12-19 2005-08-16 United Technologies Corporation Investment casting cores
US6951239B1 (en) * 2004-04-15 2005-10-04 United Technologies Corporation Methods for manufacturing investment casting shells
US7144220B2 (en) * 2004-07-30 2006-12-05 United Technologies Corporation Investment casting
US7108045B2 (en) * 2004-09-09 2006-09-19 United Technologies Corporation Composite core for use in precision investment casting
US7134475B2 (en) * 2004-10-29 2006-11-14 United Technologies Corporation Investment casting cores and methods

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Publication number Publication date
KR20070035941A (ko) 2007-04-02
JP2007090434A (ja) 2007-04-12
EP1785205A1 (de) 2007-05-16
US20070068649A1 (en) 2007-03-29
IL176624A0 (en) 2006-10-31
CN1939617A (zh) 2007-04-04

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