EP3137244A1 - Investment casting compositions, molds, and related methods - Google Patents
Investment casting compositions, molds, and related methodsInfo
- Publication number
- EP3137244A1 EP3137244A1 EP15724405.4A EP15724405A EP3137244A1 EP 3137244 A1 EP3137244 A1 EP 3137244A1 EP 15724405 A EP15724405 A EP 15724405A EP 3137244 A1 EP3137244 A1 EP 3137244A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- composition
- slurry
- layer
- refractory
- investment casting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
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- 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
- B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
-
- 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
- B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
- B22C1/08—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives for decreasing shrinkage of the mould, e.g. for investment casting
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- 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
- B22C1/165—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 in the manufacture of multilayered shell moulds
-
- 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
- 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
- B22C1/186—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 contaming ammonium or metal silicates, silica sols
-
- 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
- B22C1/20—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 organic agents
- B22C1/22—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 organic agents of resins or rosins
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
- B22C7/02—Lost patterns
-
- 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
Definitions
- compositions along with related articles and methods, useful in investment casting.
- the compositions more particularly, include additives that facilitate the making of an investment casting mold.
- Investment casting sometimes referred to as a "lost wax” process, is a well known method of manufacturing components having intricate and complex shapes. This process is used in diverse large- and small-scale applications, ranging from the manufacture of superalloy gas turbine engine components to tiny customized orthodontic appliances.
- the pattern is then heated, typically using a flash furnace or steam autoclave, to melt the wax and allow it to be extracted from the mold.
- the end result is a mold with a hollow cavity faithfully reproducing the shape of the pattern.
- the mold can be further strengthened by firing.
- a molten metal alloy can then be introduced into the mold cavity to cast the desired part.
- the mold can be mechanically or chemically disintegrated to separate the cast part from the mold.
- the finished shell contains six or more layers, each of which could include two or more sub-layers of slurry or stucco.
- the first layer known as a prime coat
- the prime coat often includes both a refractory slurry and a refractory stucco.
- the next layer known as the intermediate coat, is applied over the prime coat and also includes a refractory slurry and a refractory stucco.
- three or more backup coats are generally applied to build up the thickness of the shell.
- Each backup coat also commonly includes a refractory slurry and a refractory stucco.
- a final seal coat is then applied over the final backup coat to prevent stucco from coming loose from the shell during further processing of the shell.
- Creating the aforementioned layers of the shell involves a substantial amount of time. Substantial amounts of time are involved not only in the dipping process used to apply each of the constituent slurry and/or stucco layers, but also the drying steps that follow the coating of each major layer. The large number of steps in the manufacturing process also heightens the overall risk of inadvertently inducing a defect or causing damage to the shell.
- a thixotropic agent derived from a polymer emulsion such as an acrylic polymer emulsion
- a polymer emulsion such as an acrylic polymer emulsion
- slurry compositions were further observed to resist settling over long periods of time, thereby providing a "shippable" slurry that can be mixed in advance by a manufacturer prior to delivery to the end user.
- slurry compositions could be prepared on a large scale and under precisely controlled conditions to achieve more predictable and consistent slurry compositions. Such consistency is of great value to the end user, because variation in slurry composition is known to cause shell performance issues and increase scrap rate. Both effects can adversely impact the fidelity of the final manufactured product.
- a slurry composition for investment casting is provided.
- the slurry composition comprises: a refractory material; a binder; a solvent; and a thixotropic agent comprising a polymer emulsion.
- a method of making an investment casting mold comprises: coating a sacrificial pattern with a prime layer comprising a first refractory slurry and a first refractory stucco; at least partially hardening the prime layer; coating the prime layer with an intermediate layer comprising a second refractory slurry and a second refractory stucco; at least partially hardening the intermediate layer; coating the intermediate layer with a backup layer comprising a thixotropic agent, the thixotropic agent including a polymer emulsion; and at least partially hardening the backup layer.
- FIG. 1 is a cross-sectional view of a multilayered investment casting mold according to a prior art embodiment.
- FIG. 2 is an enlarged fragmentary cross-sectional view of an inset portion of the investment casting mold of FIG. 1.
- FIGS. 3-5 are cross-sectional views of multilayered investment casting molds according to various exemplary embodiments of the invention.
- FIG. 6 is a plot of experimental data showing slurry viscosity as a function of shear rate.
- FIG. 7 is a plot of experimental data showing slurry shear stress as a function of shear rate.
- refractory refers to a heat-resistant ceramic material
- slurry refers to a fluid mixture of a solid grain with a liquid
- ucco refers to a solid grain having a particle size usually not coarser than a U.S. sieve 30 mesh screen;
- thixotropic refers to a shear-thinning property, where a gel or liquid becomes less viscous when it is shaken, agitated, or otherwise stressed;
- wax refers to a polymeric substance capable of melting at low temperatures to yield a low viscosity liquid;
- the terms "preferred” and “preferably” refer to embodiments described herein that may afford certain benefits under certain circumstances. Other embodiments may also be preferred, under the same or other circumstances. Further, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.
- the present disclosure describes, by way of illustration and example, slurry compositions used to produce investment casting molds.
- the illustrated patterns and associated sprues are exemplary, not drawn to scale, and may differ widely in size and shape depending on the application at hand. It is further understood that the refractory materials, solvents, and binders herein described are exemplary and may be substituted or modified according to the knowledge of one skilled in the art.
- compositions and related methods described herein enable one of skill in the art to make and use investment casting molds with certain advantageous properties, it is appreciated that these compositions and methods could be further combined with additives or enhancements not examined here.
- slurry compositions could further include gaseous or solvent-based gelling agents, chemically treated refractory materials, and slurry binder systems that interact with one another.
- FIG. 1 shows a conventional investment casting mold shown in cross-section and designated by the numeral 100.
- the mold 100 is shown encapsulating a substantial portion of a sacrificial pattern 102, which has a tree-like structure with a centrally located trunk 103 and a plurality of branches 105 extending outwardly from the trunk 103.
- the pattern 102 is exemplary and there are no particular restrictions on its size or shape.
- the pattern 102 is made from wax, polymer resin, or other suitable pattern material capable of being subsequently melted, vaporized, burned or dissolved to leave behind, with minimal residue, a cavity conforming to the exterior contours of the pattern 102.
- the mold 100 includes a series of successive layers built up by dipping the pattern 102 into containers of refractory slurry. After withdrawing the pattern 102 after each dip, excess slurry/stucco is allowed to drain off. Optionally, the pattern 102 is manipulated by hand or mechanically to promote uniform coverage. Refractory granules, or stucco, are then applied to the wet slurry coating.
- the combination of slurry and stucco comprises a single major layer, which then is allowed to dry and at least partially harden before the next coat is applied.
- mold 100 are progressively built up, layer upon layer, until the overall mold 100 has the strength to withstand the physical handling forces induced by metal casting. Beginning from the innermost layer and ending with the outermost layer, mold 100 includes a prime layer 104, an intermediate layer 1 10, a first backup layer 1 16, a second backup layer 122, a third backup layer 128, and a seal layer 134.
- the prime layer 104 is an innermost layer extending across and contacting the pattern 102.
- the prime layer 104 is intended to come into direct contact with molten metal after the finished mold 100 has been de-waxed and fired.
- the prime layer 104 includes two sub-layers— an inner layer of refractory slurry 106 and an outer layer of refractory stucco 108.
- both the refractory slurry 106 and refractory stucco 108 include zircon particles (shown here as round particles) although this need not be the case.
- one or more additional prime layers may be used. This may be the case, for example, where there is no intermediate slurry layer capability.
- the intermediate layer 1 10, and successive backup layers 1 16, 122, 128 also include two sub-layers each, a layer of refractory slurry 1 12, 1 18, 124, 130 and an adjacent layer of refractory stucco 1 14, 120, 126, 132, respectively.
- the refractory slurry for these layers may include a fused silica, alumino-silicate, zircon, aluminum oxide or a mixture thereof.
- the refractory stucco (represented in the figures as jagged-edged particles) may also include a fused silica, alumino-silicate, zircon, aluminum oxide, or mixture thereof.
- the stucco can be applied either by sprinkling it onto a freshly coated slurry by hand or by rainfall sander, or by immersion into of a fluidized bed of stucco.
- the size of the stucco particles generally increases from the inside to the outside of the mold 100.
- a seal layer 134 is located on the outermost periphery of the mold 100.
- the seal layer 134 serves the purpose of preventing stucco from the backup layer 128 from coming loose during subsequent processing of the finished mold 100 and can have a composition identical or similar to that of the intermediate or backup slurries.
- the seal layer 134 contains a fused silica, alumino-silicate, zircon, aluminum oxide, or a mixture thereof.
- the resulting structure as shown in FIGS. 1 and 2 can then be fully dried and heated to melt the pattern 102 and remove the pattern 102 from the finished investment casting mold 100.
- the finished mold 100 can be fired in a curing oven at temperatures of about 980 degrees Celsius.
- An improved investment casting mold 200 according to one exemplary
- the mold 200 shares some characteristics of the mold 100.
- the mold 200 includes a prime layer 204 disposed on a wax pattern 202 and an intermediate layer 210 disposed on the prime layer 204.
- the pattern 202, prime layer 204, and intermediate layer 210 generally share the
- the prime layer 204 includes an inner coating of zircon-containing slurry 206 followed by an outer layer of zircon stucco 208.
- the intermediate layer 210 in the illustrated embodiment, includes an inner coating of refractory slurry 212 and an outer layer of refractory stucco 214.
- the intermediate slurry layer 210 may also contain a zircon refractory.
- the backup layer 240 has a spatial thickness considerably greater than either of the prime or intermediate layers 204, 210.
- the backup layer 240 can fill in open undercuts and cavitiesjjresented by the branches of the pattern 202, thereby simplifying subsequent coating processes.
- the configuration of the mold 200 eliminates the need for multiple backup layers in common investment casting applications.
- the backup layer 240 includes an inner coating of a refractory slurry 242 followed by a layer of refractory stucco 244.
- a seal layer 234 is disposed over the backup layer 240 whereby the two layers 234, 240 directly contact each other.
- the seal layer 234, which serves the same purposes as those of the seal layer 134, can also be omitted if desired.
- each slurry layer is optionally disposed on the pattern or underlying layer using a dipping process.
- a dipping process it is
- the slurry advantageous for the slurry to have a sufficient viscosity to be retained on the pattern or underlying layer over an acceptable working time, yet also having sufficient flowability to fill essentially all of the voids in the dipped assembly to preserve high fidelity in the mold shape.
- Acceptable working times generally range from about 12 seconds to about 60 seconds.
- the required working time for this slurry will depend upon the process and foundry, but generally is the time required for the slurry to stop draining and then be moved from above the slurry pot into the stucco application area. Using prior art methods, this time period is on the order of 2-3 minutes.
- the investment casting mold 200 is fabricated using methods of layer-by-layer construction analogous to those used to fabricate the investment casting mold 100, but with certain deviations as noted below.
- departures from the prior art methods include differences in the composition of the refractory slurry used for the backup layer(s) and, advantageously, reduction in the number of processing steps required to produce the finished investment casting mold 200.
- the refractory slurry 242 has a composition that includes a refractory material, a binder, a solvent, and a thixotropic agent comprising a polymer emulsion.
- the refractory material is a first major component of the refractory slurry 242.
- Refractory powders commonly used in the investment casting industry are zircon (ZrSiC ), silica (SiCte), both fused and quartz, alumina (AI2O3), zirconia (Z1O2), and alumino-silicate (various combinations of AI2O3 and S1O2, commonly fired at high temperatures).
- Preferred refractory materials usable in the slurry 242 and/or stucco 244 include fused silica, alumino-silicate, zircon, aluminum oxide and mixtures thereof.
- the refractory powder can have a wide particle size distribution, including sizes as large as 30 mesh along with sub-micron particle sizes.
- the binder is a second major component of the refractory slurry 242.
- the binder may include a refractory binder, an organic binder, or a combination of both.
- Refractory binders that may be contained in the refractory slurry 242 include a variety of ceramic materials, including silicates, alkali metal silicates, silica sols, aluminum oxychloride, aluminum phosphate, gypsum-silica mixes, cements, and mixtures thereof.
- a particularly preferred refractory binder is colloidal silica.
- Organic binders can be thermally decomposable and include polyvinyl alcohol, polyvinyl butyral, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, and mixtures thereof. Exemplary binders are described, for example, in U.S. Patent Nos. 3,165,799 (Watts), 3,903,950 (Lirones), 5,021,213 ( ato et al.), and 6,020,415 (Guerra). Alternatively, the organic binder could include a mixture of colloidal sol and at least one acrylic latex polymer.
- the solvent is generally the same as the liquid dispersant used for the binder.
- water is the preferred solvent.
- solvents are available, however, including other polar solvents such as mineral acids, alcohols such as methanol, ethanol, isopropanol, and butanol, glycols and glycol ethers, and mixtures thereof.
- Commercial binders are often provided in solution form, so the step of adding of a separate solvent may not be necessary.
- composition of the refractory slurry 242 further includes a thixotropic agent
- the polymer emulsion is an acrylic polymer emulsion. More preferably, the polymer emulsion is an acrylic polymer emulsion in water.
- Polymers suitable for this application may be prepared using any of a number of different synthetic routes.
- Alkali-swellable polymers for example, are synthesized by copolymerizing different monomers, where at least one monomer contains a carboxyl (- COOH) functional group. These polymers may have a structure that is linear, branched or cross linked to form a networked structure.
- Use of these polymers as thickening agents is described, for example, in U.S. Patent No. 4,226,754 (Whitton et al), which discloses a polymer made by reacting an ester of methacrylic acid, methacrylic acid and a vinyl ester of a saturated aliphatic carboxylic acid.
- These thickeners are often referred to as alkali- swellable thickeners because the carboxylic acid groups are sufficient to render the polymer water-soluble when neutralized with a suitable base.
- the slurry composition includes hydrophobic entities covalently bonded to the polymeric backbone.
- polymers can be formed by reacting an ethylenically unsaturated carboxylic acid monomer, a nonionic vinyl monomer, and a vinyl surfactant ester such as an alkylphenoxypoly (ethyleneoxy) ethyl acrylate terminated on one end with an alkyl phenyl group.
- a vinyl surfactant ester such as an alkylphenoxypoly (ethyleneoxy) ethyl acrylate terminated on one end with an alkyl phenyl group.
- Another example derives from a reaction product of an unsaturated carboxylic acid, alkyl (meth)acrylate, and an ester containing an alkyl phenyl group, where the alkyl group has 8 to 20 carbon atoms.
- composition includes an emulsion copolymer based on the reaction product of monomers including methacrylic acid, ethyl acrylate, optionally a defined copolymerizable ethylenica!Iy unsaturated monomer, and a small weight percent of a polyethylenically unsaturated monomer.
- a wide range of surfactants can enhance the thickening effect on the composition when added to an aqueous system containing the copolymer when the emulsion copolymer is neutralized.
- the aforementioned copolymers are further described in European Patent No. 13,836 (Chang et al.) and U.S. Patent No. 4,421,902 (Chang et al.).
- the copolymer On partial or complete neutralization, the copolymer becomes water- soluble or colloidally dispersible, and can be used as a thickening agent.
- These copolymers are also described in U.S. Patent No. 4,668,410 (Engel et al.).
- One particularly advantageous thixotropic agent usable in the refractory slurry 242 is a polymer emulsion based on hydrophobically modified ester of methacrylic acid available from Elementis Specialties in Hightstown, NJ under the tradename RHEOLATE. Methods of making such polymer emulsions are described in detail, for example, in U.S. Patent No. 6,069,217 (Nae et al.).
- the slurry composition displays a working viscosity of about 20 poise when subjected to a shear stress of at least 1 dyne per square centimeter, of at least 5 dynes per square centimeter, of at least 10 dynes per square centimeter, of at least 20 dynes per square centimeter, of at least 50 dynes per square centimeter, at least 100 dynes per square centimeter, at least 200 dynes per square centimeter, or at least 400 dynes per square centimeter, as measured using the method described in the Examples.
- the same composition displays a working viscosity of about 20 poise when subjected to a yield stress in shear of at most 1000 dynes per square centimeter, at most 950 dynes per square centimeter, at most 900 dynes per square centimeter, at most 850 dynes per square centimeter, or at most 800 dynes per square centimeter.
- Investment casting shells generally have large porosity as a result of the stuccoing process, which can adversely affect strength. For the strength to be deemed adequate for a given application, it must be capable of withstanding potentially high internal pressure and thermal stress, especially during the de-waxing process and when pouring metal into the free standing ceramic shell. Cracking can occur when the stress on the mold is greater than the modulus of rupture of the mold material.
- the investment casting mold has non-fired modulus of rupture of at least 150 psi, at leastl75, at least 200 psi, at least 225, or at least 250 psi, after being fully hardened. In some embodiments, the investment casting mold has non-fired modulus of rupture of at most 750 psi, at most 735, at most 725 psi, at most 710, or at most 700 psi, after being fully hardened.
- the composition of the refractory slurry 242 further includes an aluminum phyllosilicate clay.
- the aluminum phyllosilicate clay is present in an amount ranging from a weight ratio of at least 1 : 15, at least 1 : 10, at least 1 :8, at least 1 :7, or at least 1 :6, relative to that of the polymer emulsion.
- the aluminum phyllosilicate clay is present in an amount ranging from a weight ratio of at most 6 : 1 , at most 5 : 1 , or at most 4 : 1 , relative to that of the polymer emulsion.
- This three-layered construction includes a prime layer 304 extending across and contacting a sacrificial pattern 302, an intermediate layer 310 extending across and contacting the prime layer 304, and a single backup layer 340 extending across and contacting the intermediate layer 310.
- each of the layers 304, 310, 340 includes an inner sub-layer of refractory slurry adjoining an outer sub-layer of a refractory stucco.
- Absent from the mold 300 is an outermost seal layer; in FIG. 4, the layered construction ends with the refractory stucco for the backup layer 340. While sharing most of the functional properties of the mold 200, the mold 300 requires even fewer processing steps to fabricate.
- FIG. 5 illustrates an investment casting mold 400 according to yet another embodiment.
- the mold 400 is notably even further simplified in its two-layered construction. Showing merely a prime layer 404 and backup layer 440 disposed on a pattern 402, the mold 400 can advantageously be made using only two dips— one for each of layers 404, 440.
- Other aspects of the mold 400 and its constituent layers are essentially the same as those described with respect to the three- and four-layered embodiments above.
- an investment casting slurry composition displays a yield stress that is sufficient to prevent excessive drainage of the slurry from a pattern after the pattern is withdrawn from a bath of the slurry.
- This characteristic should be tempered, however, by its flowability— essentially, its ability to flow into and around complex pattern geometries, including narrow cavities, when the pattern is dipped into the slurry.
- the slurry compositions provided here operate in a solid-like regime at the low shear rates associated with gravity, but operate in a liquid-like regime at higher shear rates associated with dipping the pattern into a bath of the slurry.
- the provided compositions reduce the number of required dips while preserving the fidelity of the final molded product.
- the yield stress of the slurry composition is at least 0.2 dynes/cm 2 , at least 0.5 dynes/cm 2 , at least 1 dyne/cm 2 , at least 5 dynes/cm 2 , or at least 10 dynes/cm 2 .
- the yield stress of the slurry composition can be at most 200 dynes/cm 2 , at most 250 dynes/cm 2 , at most 500 dynes/cm 2 , at most 750 dynes/cm 2 , or at most 1000 dynes/cm 2 .
- Exemplary slurry compositions at the onset of flow, can display a viscosity at the onset of flow of at least 50 poise, at least 100 poise, at least 200 poise, at least 500 poise, or at least 1000 poise.
- the viscosity of the slurry composition at the onset of flow can be at most 7000 poise, at most 8000 poise, at most 9000 poise, at most 10000 poise, or at most 12000 poise.
- Technical features and advantages of the invention are further exemplified by, but are not necessarily limited to, the following enumerated embodiments A-AI:
- a slurry composition for investment casting including: a refractory material; a binder; a solvent; and a thixotropic agent including a polymer emulsion.
- composition of embodiment A or B, where the polymer emulsion includes an alkali-swellable polymer is provided.
- composition of embodiment C, where the alkali-swellable polymer includes a hydrophobically modified ester of methacrylic acid includes a hydrophobically modified ester of methacrylic acid.
- composition of any one of embodiments A-D, further including an aluminum phyllosilicate clay is provided.
- composition of embodiment E where the aluminum phyllosilicate clay is present in an amount ranging from a weight ratio of 1 : 15 to 6: 1 relative to the polymer emulsion.
- G The composition of embodiment F, where the aluminum phyllosilicate day is present in an amount ranging from a weight ratio of 1 :8 to 4: 1 relative to the polymer emulsion.
- H The composition of embodiment G, where the aluminum phyllosilicate clay is present in an amount ranging from a weight ratio of 1 :6 to 4:1 relative to the polymer emulsion.
- composition of embodiment I where the polymer emulsion is present in an amount ranging from 0.05 weight percent to 1 weight percent based on the overall weight of the composition. .
- composition of any one of embodiments A- where the composition has an overall solids content ranging from 45 weight percent to 80 weight percent, based on the overall weight of the composition.
- M The composition of embodiment L, where the composition has an overall solids content ranging from 45 weight percent to 75 weight percent, based on the overall weight of the composition.
- composition of embodiment M where the composition has an overall solids content ranging from 50 weight percent to 75 weight percent, based on the overall weight of the composition.
- composition of any one of embodiments A-P where the composition displays a working viscosity of about 20 poise when subjected to a yield stress ranging from 25 dynes/cm 2 to 1000 dynes/cm 2 .
- R The composition of embodiment Q, where the composition displays a working viscosity of 20 poise when subjected to a yield stress ranging from 25 dynes/cm 2 to 900 dynes/cm 2 .
- composition of embodiment R where the composition displays a working viscosity of 20 Poise when subjected to a yield stress ranging from 25 dynes/cm 2 to 800 dynes/cm 2 .
- T The composition of any one of embodiments A-S, where the binder includes a styrene-butadiene latex.
- a method of making an investment casting mold including: coating a sacrificial pattern with a prime layer including a first refractory slurry and a first refractory stucco; at least partially hardening the prime layer; coating the prime layer with an intermediate layer including a second refractory slurry and a second refractory stucco; at least partially hardening the intermediate layer; coating the intermediate layer with a backup layer including a thixotropic agent, the thixotropic agent including a polymer emulsion; and at least partially hardening the backup layer.
- AA The method of any one of embodiments W-Z, where the second refractory stucco includes fused silica, alumina, alumino-silicate, or a mixture thereof.
- AB The method of any one of embodiments W-AA, further including: coating the backup layer with a seal layer including a third refractory slurry, where the seal layer directly contacts the backup layer; and at least partially hardening the seal layer.
- AD The method of any one of embodiments W-AC, where the investment casting mold has a non-fired modulus of rupture ranging from 150 psi to 750 psi after fully hardened.
- WDS II fused silica flour was obtained from 3M Midway, Midway, TN, under the trade designation "WDS II”.
- WDS 3 fused silica flour, was obtained from 3M Midway, Midway, TN, under trade designation "WDS 3".
- Min-Sil 120F fused silica flour, was obtained from 3M Midway, Midway, TN, under trade designation "Min-Sil 120F”.
- NALCO 6300 a styrene-butadiene latex polymer , 50 weight% solids, was obtained from Nalco Chemical Company, Naperville, IL, under trade designation
- Minco HP a styrene butadiene latex polymer, 50 weight% solids, was obtained from 3M Midway, Midway, TN, under trade designation "Minco HP”.
- NALCO 2305" antifoam additive containing a blend of silicones and polyglycols in a hydrocarbon solvent, was obtained from Nalco Chemical Company, Naperville, IL, under trade designation “NALCO 2305".
- NALCO 8815 a wetting agent, was obtained from Nalco Chemical Company, Naperville, IL, under trade designation “NALCO 8815”.
- BENTONE EW highly beneficiated, easily dispersible powdered clay thickener, was obtained from Elementis, Specialties, Inc., Hightstown, NJ, under trade designation "BENTONE EW”.
- RHEOLATE 420 an alkali swellable thickener, was obtained from Elementis, Specialties, Inc., Hightstown, NJ, under trade designation "RHEOLATE 420".
- RHEOLATE 288 a highly efficient polyether polyurethane associative thickener, was obtained from Elementis, Specialties, Inc., Hightstown, NJ, under trade designation "RHEOLATE 288".
- RHEOLATE 1 an acrylic thickener with high thickening efficiency, was obtained from Elementis, Specialties, Inc., Hightstown, NJ, under trade designation "RHEOLATE 1".
- RHEOLATE 278 a highly efficient polyether polyurethane associative thickener, was obtained from Elementis, Specialties, Inc., Hightstown, NJ, under trade designation "RHEOLATE 278".
- SOLTHIX A300 an alkali swellable thickener, was obtained from Lubrizol Advanced Materials, Inc., Brecksville, OH, under trade designation "SOLTHIX A300".
- SOLTHIX A 100 an alkali swellable thickener, was obtained from Lubrizol Advanced Materials, Inc., Brecksville, OH, under trade designation "SOLTHIX A 100".
- TIXATROL PLUS an active, seed resistant organic rheological additive, was obtained from Elementis, Specialties, Inc., Hightstown, NJ, under trade designation "THIXATROL PLUS".
- Fused silica 50 x 100 mesh (finer than U.S. Sieve 50 mesh but coarser than U.S. Sieve 100 mesh), was obtained from 3M Midway, Midway, TN.
- de-ionized (DI) water and NALCO 1 130 silica sol were added Into a sufficient volume container, de-ionized (DI) water and NALCO 1 130 silica sol were added. While mixing using a INDCO Model HS120T mixer (2 horsepower, 220 V, single phase motor, set at a speed of 2050 rpm), desired amounts of silica flour, additives such as polymeric binders (e.g., styrene-butadiene latex), antifoam and/or wetting agents were added and mixing was continued until all the lumps were dispersed. Finally, if desired, a Theological additive (i.e., a thixotropic agent) was added and mixing was continued, typically for less than 5 minutes.
- a Theological additive i.e., a thixotropic agent
- a wax pattern having the shape of final investment cast parts was provided.
- investment cast molds were formed by building a series of shells (i.e., layers) sequentially.
- the wax pattern was coated by a "prime layer" which comprises an initial coating of prime slurry layer which was further coated with a prime stucco layer.
- the prime slurry layer was formed by dipping the wax pattern in the prime slurry for about 20 seconds while rotating and moving the wax pattern to maximize the uniformity of the prime slurry layer.
- a prime stucco layer was then deposited on the wet prime slurry layer by exposing the wax pattern with the prime slurry layer thereon to a fluidized bed of 50 x 100 mesh zircon particles.
- the wax pattern with the prime stucco layer was then dried at 21 degrees Celsius for about 2 hours.
- the wax pattern with the dried prime layer was coated with an "intermediate layer" in essentially the same manner as the prime layer except by using an intermediate slurry and stucco layers and dried.
- the intermediate stucco layer was formed using a fluidized bed of 50 x 100 mesh fused silica particles.
- the composition of the intermediate slurry could be the same or different than the primary slurry.
- the resulting pattern was then coated with one or more backup layer(s) in essentially the same manner as the primary/intermediate layer except using backup slurry and stucco layers and dried.
- the backup stucco layer was formed using a fluidized bed of 30 x 50 mesh fused silica particles.
- the composition of the backup slurry could be the same or different than the primary/intermediate slurry.
- the backup slurry layer/stucco layer building is typically repeated several times to build enough thickness with sufficient drying between each layer.
- the pattern with sufficiently thick backup layer(s) was coated with a seal layer by dipping it again into the backup slurry and drying.
- the final investment casting molds were freed of the wax pattern, fired and used for testing and/or preparing final investment cast parts.
- Viscosity and shear stress data for slurries were measured using an AR G2 stress controlled rheometer (TA Instruments, New Castle, DE) outfitted with a 40-mm diameter parallel plate fixture. Measurements were made using a gap of 1 mm and an operating temperature of 23 degrees Celsius.
- the strength test data reported was average of 24 test samples for each Example and Comparative Example investment cast mold compositions. The strength data for Example samples were run along with the corresponding Comparative Example samples. The strength test data e.g., modulus of rupture (MOR), modulus of elasticity (MOE), and load at failure were determined. The strength testing was done in the green and fired states under variety of environmental conditions.
- MOR modulus of rupture
- MOE modulus of elasticity
- samples were prepared by building shells using the slurries prepared according to the Examples and Comparative Examples, on polyvinylchloride (PVC), schedule 40 cold plumbing pipes.
- PVC polyvinylchloride
- the PVC pipes had 0.75 in. (1.09 cm) inner diameter and 1.05 in. (2.77 cm) outer diameter and were 13 in. (33 cm) long.
- the pipes were first coated with wax (S.C. Johnson's Paste Wax). After the shells were built, the resulting samples were cut into 6 in. (15.2 cm) long sections for testing.
- the permeability and burst testing was done using the method described in Snyder, B. and Snow, J. "A New
- CE-1 investment cast mold was prepared using the general method for preparing investment casting molds described above, except that no prime layer was applied and that the CE-l investment cast mold included five backup layers.
- the compositions of the intermediate, backup, and seal slurry layer used for preparing CE-1 investment cast mold was the same and the slurry was prepared as described in the general method for preparing prime slurry, intermediate slurry, and backup slurry described above by mixing 13,705 g of WDS II silica flour, 4,516 g of NALCO 1 130, 934 g DI water, 498 g Minco HP latex binder, and 21 g NALCO 2305 antifoam additive.
- the CE-1 investment cast molds were fired at 2000°F (1093°C) for two hours before use.
- CE-2 investment cast mold was prepared using the general method for preparing investment casting molds described above, except that no prime layer was applied and that the CE-2 investment cast mold included five backup layers.
- the compositions of the intermediate, backup, and seal slurry layer used for preparing CE-2 investment cast mold was the same and the slurry was prepared as described in the general method for preparing prime slurry, intermediate slurry, and backup slurry described above by mixing 13,305 g of WDS 3 silica flour, 6,259 g of NALCO 1 130, 545 g NALCO 6300, 285 g DI water, 10 g NALCO 2305 antifoam additive, and 10 g NALCO 8815 wetting additive.
- the CE-2 investment cast molds were fired at 2000°F (1093°C) for two hours before use.
- EX-3 investment cast mold was prepared using the general method for preparing investment casting molds described above, except that no prime layer was applied and that the EX-3 investment cast mold included only one backup layer.
- the compositions of the intermediate, and seal slurry layer were same as that used for preparing CE-1 investment cast mold as described above.
- the slurry used for EX-3 backup layer had a unique composition that enabled a useful, single backup layer.
- the EX-3 backup slurry was prepared as described in the general method for preparing prime slurry, intermediate slurry, and backup slurry described above by mixing 6,750 g of Min-Sil 120F fused silica flour, 3,362 g of NALCO 1 130, 476 g Dl water, 164 g styrene-butadiene latex binder, and 15 g RHEOLATE 420 rheological additive (thixotrope).
- the EX-3 investment cast molds were fired at 2000°F ( 1093°C) for two hours before use.
- CE- 1 , CE-2 and EX-3 formulations were used to prepare sufficient number of permeability, burst, and strength testing under a variety of test conditions as described below. Sample preparation and testing was carried out using the procedures described above. Test results obtained are described below.
- CE-1 , CE-2 and EX-3 samples prepared for strength testing and permeability testing were used to determine the thickness of the shells built for each formulation.
- the shell thickness data is summarized in Table 1 , below. Table 1
- Table 4 summarizes the hot / wet strength test data after boiling for 15 minutes in water (e.g. "hot/wet” state).
- CE-1, CE-2, and EX-3 were obtained using the method described above.
- Table 5 summarizes the fired (after cooling to room temperature) strength test data for CE-1, CE-2, and EX-3, obtained using the method described above.
- CE-1 , CE-2, and EX-3 prepared using the method described above.
- Comparative CE-4 and Examples EX-5 to EX- 19 were prepared to demonstrate the variation of rheological properties of backup slurries with the amount and type of various rheological additives.
- CE-4 was prepared in the same manner as EX-3 except CE-4 did not contain any rheological additive.
- EX-5 to EX-22 were prepared in the same manner as EX-3 except that the rheological additive RHEOLATE 420 was replaced with various rheological additives as summarized in Table 7, below.
- EX-24 to EX-26 additional mixing steps were used to incorporate additional components.
- BENTONE EW was added to the batch, mixed lightly by hand to wet the clay, then mixed in a high-intensity mixer for 30 seconds.
- RHEOLATE 420 was then added to the batch and mixed at high intensity for 1 minute.
- a prime stucco layer was then deposited on the wet prime slurry layer by exposing the wax pattern with the prime slurry layer thereon to a fluidized bed of 50 x 100 mesh zircon particles.
- the wax pattern with the prime stucco layer was then dried at 21 degrees Celsius for about 2 hours.
- the wax pattern with the dried prime layer was coated with the corresponding Example slurries followed by a stucco layer which was formed using a fluidized bed of 30 x 50 mesh fused silica particles.
- the slurries used for EX-27 to EX-32 backup layers had unique compositions that enabled a useful, single backup layer.
- each mold were applied with a seal layer (also known as a cover coat).
- the composition of the seal layer slurry was the same as CE-1 slurry.
- EX-27 slurry was prepared as described in the general method for preparing prime slurry, intermediate slurry, and backup slurry described above by mixing 13,500 g of Min- Sil 120F fused silica flour, 15 g of BENTONE EW, 6,724 g of NALCO 1 130, 952 g DI water, 328 g styrene-butadiene latex binder, and 60 g RHEOLATE 475 rheological additive (thixotrope).
- EX-28 slurry was the same as EX-27 slurry, except that it was aged for 1 month before use.
- EX-29 slurry was same as EX-27 slurry except that it contained 30 g of
- EX-30 slurry was the same as EX-29 slurry, except that it was aged for 1 month before use.
- EX-31 slurry was same as EX-27 slurry except that it contained 120 g of
- EX-32 slurry was same as EX-31 slurry except that it was aged for 1 month before use.
- CE-24 and CE-25 were same as CE-1 and CE-2, respectively.
- CE-24, CE-25 and EX-27 to EX-32 formulations were used to prepare sufficient number of permeability, burst, and strength test samples for testing under a variety of test conditions as described below. Sample preparation and testing was carried out using the procedures described above. Test results obtained are summarized below.
- CE-24, CE-25 and EX-27 to EX-32 samples prepared for strength testing (24 samples per Example) and permeability testing ( 10 samples per Example) were used to determine the thickness of the shells built for each formulation. The shell thickness data is summarized in Table 10, below.
- Table 1 summarizes the permeability and burst test data for CE-24, CE-25 and EX-27 to EX-32 obtained using the method described above.
- Table 12 summarizes the green strength test data for green CE-24, CE-25 and EX-27 to EX-32, obtained using the method described above.
- Table 13 summarizes the hot / wet strength test data after boiling for 15 minutes in water (e.g. "hot/wet” state).
- CE-24, CE-25 and EX-27 to EX-32 were obtained using the method described above.
- Table 14 summarizes the fired (after cooling to room temperature) strength test data for CE-24, CE-25 and EX-27 to EX-32, obtained using the method described above.
- Table 15 summarizes the fired (and tested while hot) strength test data for CE-24, CE-25 and EX-27 to EX-32, prepared using the method described above.
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Abstract
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US201461987604P | 2014-05-02 | 2014-05-02 | |
PCT/US2015/028193 WO2015168233A1 (en) | 2014-05-02 | 2015-04-29 | Investment casting compositions, molds, and related methods |
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US (1) | US20170043390A1 (en) |
EP (1) | EP3137244A1 (en) |
CN (1) | CN106232261B (en) |
CA (1) | CA2947695A1 (en) |
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MX2019004103A (en) * | 2016-10-10 | 2019-07-15 | 3M Innovative Properties Co | Method of making investment casting mold. |
WO2019016741A1 (en) | 2017-07-20 | 2019-01-24 | 3M Innovative Properties Company | Investment casting compositions, molds, and related methods |
US20230348667A1 (en) | 2020-09-11 | 2023-11-02 | 3M Innovative Properties Company | Investment Casting Compositions and Methods |
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US4196107A (en) * | 1978-06-05 | 1980-04-01 | Ppg Industries, Inc. | Semi-solid water-based coating compositions |
US4226754A (en) * | 1978-06-08 | 1980-10-07 | Nl Industries, Inc. | Synthetic polymer |
CN85105348A (en) * | 1985-06-27 | 1986-12-24 | 青岛化工学院 | New method of the sclerosis of Ludox and the application in precision-investment casting system shell thereof |
CN1014686B (en) * | 1988-09-30 | 1991-11-13 | 太原矿山机器厂 | Productive method of sand core for investment casting |
US9227241B2 (en) * | 2010-12-08 | 2016-01-05 | Nalco Company | Investment casting shells having an organic component |
CN102847870B (en) * | 2012-08-08 | 2014-05-21 | 南京航空航天大学 | Suspending agent for water-based zirconium oxide coating for investment titanium casting and preparation method and application of suspending agent |
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2015
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- 2015-04-29 EP EP15724405.4A patent/EP3137244A1/en not_active Withdrawn
- 2015-04-29 US US15/307,771 patent/US20170043390A1/en not_active Abandoned
Non-Patent Citations (2)
Title |
---|
DANIELS HESSELBARTH ET AL: "Mechanical Properties of Coagulated Wet Particle Networks with Alkali-Swellable Thickeners", JOURNAL OF THE AMERICAN CERAMIC SOCIETY, vol. 84, no. 8, 1 August 2001 (2001-08-01), US, pages 1689 - 1695, XP055742308, ISSN: 0002-7820, DOI: 10.1111/j.1151-2916.2001.tb00900.x * |
See also references of WO2015168233A1 * |
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CA2947695A1 (en) | 2015-11-05 |
US20170043390A1 (en) | 2017-02-16 |
WO2015168233A1 (en) | 2015-11-05 |
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