HK1048274A - Shell mold binder composition and method - Google Patents
Shell mold binder composition and method Download PDFInfo
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- HK1048274A HK1048274A HK03100564.3A HK03100564A HK1048274A HK 1048274 A HK1048274 A HK 1048274A HK 03100564 A HK03100564 A HK 03100564A HK 1048274 A HK1048274 A HK 1048274A
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Description
Technical Field
The present invention relates to a water-based primer (back-up) binder composition comprising colloidal silica and a polymer and its use for forming a rapid-processing slurry for making shell molds. The primer binder composition of the present invention includes fibers and is used to rapidly prepare ceramic shell molds for investment casting processes. Existing adhesive compositions do not include fibers. The present invention provides a composition that significantly reduces the time required to produce a ceramic shell mold. The compositions of the present invention, when used to produce ceramic shell molds for investment casting processes, not only provide low processing times by reducing the number of shell dips, but also provide better handling and dewaxing by high green strength.
Producing shell molds for investment casting typically involves dipping a wax pattern plate (or pattern) into a slurry containing a binder and a refractory powder. Wax was coated with the slurry, and the excess slurry was drained. The coarser refractory powder was dusted onto a wet wax pattern (wax pattern) and the composition was dried. Additional slurry coatings and refractory powders are applied in the same manner until the mold has a thickness and strength for further processing. The base coat is defined as the first or second coat applied to the wax pattern or pattern. The purpose of the undercoating is to provide a highly refractory surface to the metal to be cast and reproduce the details of the mould. The base binder is based on colloidal silica and usually contains other additives such as wetting agents, defoamers and polymers. The refractory powder is typically 200-400 mesh, usually zircon, but may also contain some fused silica. Zircon is selected for its excellent refractory properties. The stucco material used for the base coat is typically finer (50-150 mesh) to help capture the details of the mold. The stucco material for the undercoat is typically zircon, but may also be fused silica. The wax pattern is typically coated with a primer after the basecoat. The sealer is only a slurry coating and does not coat stucco. The sealer is typically applied in an industrial process to "seal" loose stucco to the wax pattern. The primary purpose of the primer is to provide sufficient strength to the shell to withstand the forces and pressures applied thereto during the process of producing the cast article. The seal coat is applied after the final primer coat. The principal stress is due to the pressure exerted on the shell by the wax during the wax removal process. The number of primer coats required for each shell depends on the size of the entire mold, as well as the amount of alloy injected into the shell.
It is common practice in the investment casting art to characterize the raw (unfired) properties of the shell mold (properties prior to firing) by 3-point bending, wherein a single point load is gradually applied to a raw shell test piece supported at two stationary points until failure. The main objective of the bending test is to obtain a measurement of the initial strength of the shell material: modulus of rupture (MOR)
The modulus of rupture (MOR) as used herein is defined by the following equation:
MOR＝(3xLfxS)/(2xWxT2) Wherein L isfFor maximum load at break, S is the interval between two rest points, W and T are the width and thickness of the test barAnd (c) as set forth in Investment Casting Institute Ceramic test procedure 770-79 (1979). MOR is an inherent property of a material and therefore this property is independent of the size of the test bar. It is known that shell thickness is a major factor in determining actual shell performance when an external load is applied to the shell, and the adjusted rupture load (AFL) taking into account thickness is a more accurate measurement of shell strength. AFL information and formulas have been published in a number of industrial papers.
The adjusted rupture load (AFL) as used herein is defined by the following equation:
AFL＝[fx(MOR)xT2]wherein f is as determined by Carl Schwartz of Rancom&Randolph is a constant factor for the bending type determination proposed in "Faster and Safer Shell Production" (1988).
"Polymer" as used in investment casting shell molds generally refers to macromolecules formed by the chemical bonding of 5 or more identical binding units called monomers. The type of polymer used in the present invention is referred to as an elastomer. Elastomers are polymers with elastic properties.
Refractory material, as used herein, refers to inorganic particulate materials that can be used to prepare investment cast shell molds. The refractory material is particularly resistant to changes during heating. The main refractory materials used in industry are as follows: zircon: ZrSiO4(zirconium silicate), alumina: al (Al)2O3(alumina), silica: SiO 22(silica) and aluminosilicate: xAl2O3·ySiO2A mixture of alumina and silica, which has been fired at high temperatures (2500F) to form a stable phase known as mullite, and which minimizes shrinkage as a result of firing, has been generally formed. These refractory materials are in two forms: one in the form of a powder and the other in the form of a grit, commonly referred to as stucco. The size of both the powder and the stucco can vary depending on the respective application.
Refractory powder (or refractory powder) as used herein refers to a refractory powder particulate material having a particle size of: at least 60% of the particles are smaller (finer) than 100 mesh. The refractory powder (or refractory powder) is preferably a refractory particulate material having a particle size of: at least 90% of the particles are smaller (finer) than 100 mesh.
Refractory sand (or refractory mortar), as used herein, refers to a refractory particulate material having a particle size of: at least 60% of the particles are larger (coarser) than 100 mesh. The refractory sand (or refractory mortar) is preferably a refractory particulate material having a particle size of: at least 90% of the particles are larger (coarser) than 100 mesh.
As used herein, "latex polymer" refers to an elastomeric polymer in water. For example, elastomeric polymers of the styrene butadiene (S/B type) type and elastomeric polymers of the acrylic type have the following properties:
latex # PH% solids specific viscosity type of specific gravity
(centipoise) (g/ml)
1008-953% undetected 1.01S/B
1016-750% undetected 1.01S/B
1208.550% 2001.03 acrylic
1217.050% 401.01 acrylic acid series
1409.547% 1001.05 olefinic acids
"colloidal silica" in investment casting shell molds generally refers to an aqueous dispersion of fine silica particles, usually with a small amount of a strong base (e.g., ammonia or sodium hydroxide) used as a stabilizer to produce a stable suspension. The pH obtained is generally from 8.0 to 11.0.
By "dewaxing" is meant that the wax is removed from the unfired mold coating to form an unfired mold, which is then fired and used for investment casting.
"primer" refers to a primer coating of a slurry and plaster material adapted to record minute surface details and formed from a slurry formed from a prinote binder material manufactured by ranom & Randolph, as is well known in the art, which is applied to a wax pattern, typically by dip coating in its slurry.
As used herein, "inorganic fibers" refers to fibers having an aspect ratio of at least 10, more preferably at least 30, comprising, more preferably consisting essentially of, inorganic materials.
It is an object of the present invention to provide a method of forming a shell mold comprising providing an investment casting shell mold composition, wherein the binder and powder mold coating without polymer and fiber is formed in the same manner as the binder and powder mold coating except that no polymer and fiber are present, the binder and powder mold coating without polymer and polymer has an original MOR without polymer and fiber and an original AFL without polymer and fiber, the binder and powder mold coating has an original MOR with polymer and fiber and an original AFL with polymer and fiber, the original MOR with polymer and fiber is at least 50% higher than the original MOR without polymer and fiber, the original AFL with polymer and fiber is at least 150% higher than the AFL without polymer and fiber at the same coating level, the original AFL with polymer and fiber at least 40% reduction in the number of coats is equal to the original AFL without polymer and fiber.
It is an object of the present invention to provide a method of forming a shell mold comprising providing an investment casting shell mold composition, wherein the polymeric but non-fibrous binder and powder mold coating are formed in the same manner as the binder and powder mold coating except that no fiber is present, the polymeric but non-fibrous binder and powder mold coating has a polymeric but non-fibrous original MOR and a polymeric but non-fibrous original AFL, the polymeric but non-fibrous original MOR and the polymeric but non-fibrous original AFL, the polymeric but non-fibrous original MOR being at least 25% higher than the polymeric but non-fibrous original MOR, the polymeric but non-fibrous original AFL being at least 100% higher than the polymeric but non-fibrous original AFL at the same coating level, the original AFL with polymer and fiber at a reduction of the number of coatings of at least 25% is equal to the original AFL with polymer but no fiber.
It is an object of the present invention to provide a method of forming a shell mold comprising providing an investment casting shell mold composition comprising from 0.1 to 70 weight percent of inorganic fibers providing a disposable pattern, applying the composition to the mold to form a binder coated mold, applying a refractory powder to the binder coated mold to form a binder and powder mold coating, the improvement comprising the binder composition.
It is an object of the present invention to provide a method of forming a shell mold, the method comprising: providing an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 weight percent of a sol containing inorganic particles and 1 to 20 weight percent of an organic polymer; in the improvement of applying a refractory powder to a binder to form a slurry, providing a primer coated primary investment, applying the slurry composition to the mold to form a slurry coated mold, and discharging and applying a dried coarse refractory layer (stucco), the binder composition comprising from 0.1 to 70 weight percent inorganic fiber.
It is an object of the present invention to provide an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 wt% of a sol containing inorganic particles, 1 to 20 wt% of an organic polymer, and 0.1 to 70 wt% of inorganic fibers; wherein the inorganic particles have an average particle size of less than 600 mesh and the inorganic fibers have an average aspect ratio of greater than 30.
It is an object of the present invention to provide a method of forming a shell mold, the method comprising the steps of: providing an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 weight percent of a sol comprising inorganic particles, 1 to 20 weight percent of an organic polymer, and 0.1 to 70 weight percent of inorganic fibers; wherein the inorganic particles have an average particle size of less than 600 mesh and the inorganic fibers have an average aspect ratio of greater than 30, applying a refractory powder to a binder to form a slurry, providing a bottom coated primary investment, applying the slurry composition to the mold to form a slurry coated mold, and discharging and applying a dried coarse refractory layer (stucco).
Summary of the invention
The present invention provides a composition that significantly reduces the time required to produce a ceramic shell mold. The compositions of the present invention, when used to produce ceramic shell molds for investment casting processes, not only provide low processing times by reducing the number of shell immersions, but also provide better handling and dewaxing by high green strength.
The present invention provides a method of forming a shell mold comprising providing an investment casting shell mold composition comprising from 0.1 to 70 weight percent of fibers providing a primary investment, applying the composition to the mold to form a binder coated mold, applying a refractory powder to the binder coated mold to form a binder and powder mold coating, the improvement comprising including the binder composition.
The present invention provides an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 wt% of a sol comprising inorganic particles, 1 to 20 wt% of an organic polymer, and 0.1 to 70 wt% of inorganic fibers; wherein the inorganic particles have an average particle size of less than 600 mesh and the inorganic fibers have an average aspect ratio of greater than 30.
The present invention provides an improved method of forming a shell mold, the method comprising: providing an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 weight percent of a sol containing inorganic particles and 1 to 20 weight percent of an organic polymer; in the improvement wherein the binder composition comprises 0.1 to 70 wt% inorganic fiber, the refractory powder is mixed with a binder to form a slurry, a primer coated primary investment is provided, the slurry composition is applied to a mold to form a slurry coated mold, and a dried coarse refractory layer (stucco) is discharged and applied.
The invention provides a method of forming a shell mold, the method comprising the steps of: providing an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 weight percent of a sol comprising inorganic particles, 1 to 20 weight percent of an organic polymer, and 0.1 to 70 weight percent of inorganic fibers; wherein the inorganic particles have an average particle size of less than 600 mesh and the inorganic fibers have an average aspect ratio of greater than 30, applying a refractory powder to a binder to form a slurry, providing a bottom coated primary investment, applying the slurry composition to the mold to form a slurry coated mold, and discharging and applying a dried coarse refractory layer (stucco).
The present invention provides a method of forming a shell mold comprising providing an investment casting shell mold composition wherein a polymer and fiber free binder and powder mold coat and a polymer containing fiber free binder and powder mold coat are formed in the same manner as the binder and powder mold coat except that the polymer and fiber free binder and powder mold coat has a polymer and fiber free raw AFL, the polymer and fiber containing binder and powder mold coat has a polymer and fiber containing raw AFL, the polymer and fiber containing raw AFL is at least 150 higher than the polymer and fiber free raw AFL and at least 100 higher than the polymer and fiber containing raw AFL at the same coat level. Detailed description of the invention
In general, the adhesive of the present invention can be used to prepare a shell mold according to the following method. The binder preferably comprises a mixture of a sol, inorganic fibers and a latex polymer. A slurry is prepared by adding a refractory powder to a binder, and the slurry mixture is mixed to wet the powder. A primary investment of material, such as a wax pattern, is dipped into the slurry, excess slurry is drained, and the mold is stuccoed with additional refractory material while it remains wet. The mold and slurry are dried to establish a bond in the binder.
The dipping, draining and painting steps can be repeated as necessary to form a shell mold having a predetermined desired thickness. After the mold is made, the disposable pattern is removed by heating and discharging the liquid mold material, and the shell mold is fired. After firing, the molten metal is poured into a shell mold and allowed to cool. After cooling, the shell mold is removed from the metal, thereby providing the desired cast metal component.
Latex polymers are included in the adhesive to improve the green strength properties of the shell made from the adhesive. Furthermore, during the mold making process, the latex polymer reduces the processing time between impregnations as compared to impregnations of the binder without the latex polymer. The inorganic fibers are included to increase the thickness of each adhesive coating containing latex so that a sufficiently strong shell of similar thickness can be formed with fewer coatings than other adhesives currently available.
The colloidal silica sols preferably used in the present invention have an average particle size of 3 to 100 nanometers (nm), more preferably 5 to 20nm, and a silica content of 8 to 50 wt%, preferably 12 to 35 wt%. There are many latexes such as vinyl acetate, polyvinylidene chloride, acrylic, styrene butadiene, and the like. Styrene butadiene latex has attracted considerable attention in investment casting because many of these latexes have good compatibility when mixed with colloidal silica and can be added to improve the green strength of the shell. Preferred latex polymers include blends of acrylic polymers having the following properties: pH6-11 (most preferably 7-10); viscosity 50-1000 centipoise (most preferably 50-500); solids content 40-65% (most preferably 45-55%); the average particle size is 0.05 to 1.0 micron (most preferably 0.1 to 0.5 micron). Preferred inorganic fibers for use in the present invention have an average aspect ratio of greater than 30. An example of a refractory powder commonly used in the investment casting industry is zircon (ZrSiO)4) Fused Silica (SiO)2) Aluminum oxide (Al)2O3) Zirconium oxide (ZrO)2) And aluminosilicate (Al)2O3With SiO2Typically to 2500F) high temperature. Any other compatible powder system may also be used. The size of the powder used is generally classified as-120 mesh (u.s.a. standard sieve) to-400 mesh. Commonly used dimensions are well known in the art, but other dimensions are not excluded from the scope of the invention. The slurry is prepared byThe stock preferably has a viscosity (measured by a #4 Zahn cup) of 5 to 20 seconds.
The latex polymer is added to the colloidal silica binder in any ratio such that the ratio of colloidal silica to latex polymer is greater than 1: 1, preferably greater than 3: 1. The concentration of colloidal silica is expected to be 8 to 80 wt% of the weight of the composition. The latex polymer is present in an amount of 2 to 20 weight percent based on the weight of the binder. Other components (surfactants, biocides, etc.) known in the art may also be added to the binder without altering the spirit and scope of the present invention. The refractory powder is mixed with a binder to form a slurry. The slurry composition is applied to the primary investment of the base coat to form a slurry coated mold. The dried raw refractory (stucco) is applied to the slurry coated mold. The stucco coated mold is formed by repeating drying, dipping, draining, painting and drying.
In a preferred embodiment, the present invention provides a method of forming a shell mold, the method comprising: providing an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 weight percent of a sol containing inorganic particles and 1 to 20 weight percent of an organic polymer; applying a refractory powder to a binder to form a slurry, providing a primer coated primary investment, applying the slurry composition to the mold to form a slurry coated mold, and discharging and applying a dry coarse refractory layer (stucco). The improvement resides in the binder composition comprising from 0.1 to 70 wt% of inorganic fibers. The binder and powder mold coat without polymer and fiber is formed in the same manner as the binder and powder mold coat, except that no polymer and fiber are present. The binder without polymer and fiber and the coating of the powder mold have a raw AFL without polymer and fiber. The coating containing polymer and fiber has an original AFL containing polymer and fiber. The original AFL with polymer and fiber is preferably at least 75% greater than the original AFL without polymer and fiber, more preferably at least 100% greater than the original AFL without polymer and fiber, at the same coating number. The original AFL containing polymer and fiber is most preferably at least 150% greater than the original AFL without polymer and fiber. Another mold coat containing polymer but no fiber binder and powder was formed in the same manner as the binder and powder mold coat except that no fiber was present. The polymer-containing but fiber-free binder and powder mold coating had a raw AFL containing polymer but no fiber. The original AFL containing polymer and fiber is preferably at least 50% greater than the original AFL containing polymer but no fiber at the same number of coats. More preferably, the original AFL containing polymer and fiber is at least 75% greater than the original AFL containing polymer but no fiber. The original AFL containing polymer and fiber is most preferably at least 100% greater than the original AFL containing polymer but no fiber.
In a preferred embodiment, the present invention provides an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 weight percent of a sol containing inorganic particles, 1 to 20 weight percent of an organic polymer, and 0.1 to 70 weight percent of inorganic fibers; wherein the inorganic particles have an average particle size of less than 600 mesh and the inorganic fibers have an average aspect ratio of greater than 30.
In a preferred embodiment, the present invention provides a method of forming a shell mold, the method comprising: investment casting shell mold compositions are provided comprising a binder composition comprising a mixture of 20 to 98 weight percent of a sol containing inorganic particles, 1 to 20 weight percent of an organic polymer, and 0.1 to 70 weight percent of inorganic fibers. The inorganic particles have an average particle size of less than 600 mesh and the inorganic fibers have an average aspect ratio of greater than 30. The refractory powder is mixed with a binder to form a slurry. The bottom coated primary investment is coated with the slurry composition to form a slurry coated mold. Slurry coated molds are formed by repeatedly dipping the primary investment pattern of the basecoating cloth into the slurry composition, draining and drying. The stucco coated mold is formed by stuccoing (coating a dry coarse refractory layer) and drying the slurry coated mold.
In accordance with a preferred embodiment of the present invention, there is provided an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 wt% of a sol containing inorganic particles, 1 to 20 wt% of an organic polymer, and 0.1 to 70 wt% of inorganic fibers. The inorganic particles have an average particle size of less than 600 mesh and the inorganic fibers have an average aspect ratio of greater than 30. The binder composition preferably comprises 1 to 90 wt% of the refractory powder. The refractory powder preferably has a mesh size of 120 to 400 mesh, and is selected from the group consisting of aluminosilicates, fused silica, quartz silica, alumina, zircon and zirconia. The sol preferably comprises silica having an average particle diameter of 3 to 100 nm. The ratio of colloidal silica to latex polymer is preferably greater than 1: 1. The colloidal silica to latex ratio is preferably from 10: 1 to 1: 1. The latex polymer preferably comprises a blend of acrylic polymers having the following properties: the pH is 6-11; viscosity 50-1000 centipoise; the solid content is 40-65%; the average particle size is 0.05-1.0 micron. The latex polymer preferably comprises a blend of acrylic polymers having the following properties: the pH value is 7-10; viscosity 50-500 centipoise; solid content is 50-60%; the average particle size is 0.1-0.5 micron. The polymer latex is preferably an acrylic latex or a styrene butadiene latex. The silica sol preferably has an equilibrium particle size below 30 nm. The adhesive composition preferably comprises 1 to 98 wt% water.
According to a preferred embodiment of the present invention, there is provided a method of forming a shell mold, the method comprising the steps of: investment casting shell mold compositions are provided comprising a binder composition comprising a mixture of 20 to 98 weight percent of a sol containing inorganic particles, 1 to 20 weight percent of an organic polymer, and 0.1 to 70 weight percent of inorganic fibers. The inorganic particles have an average particle size of less than 600 mesh and the inorganic fibers have an average aspect ratio of greater than 30. The refractory powder is then mixed with a binder to form a slurry and applied to the mold to form a slurry coating on the mold. The refractory mortar is then applied over the slurry coating to form a slurry and plaster mold coating. The refractory powder preferably has a particle size of 120 to 400 mesh.
In accordance with a preferred embodiment of the present invention, there is provided a method of forming a shell mold comprising providing an investment casting shell mold composition comprising a liquid binder composition; mixing a refractory powder with a binder to form a slurry composition, providing a primer coated primary investment, applying the slurry composition to a mold to form a partial slurry coating on said mold, draining at least a portion of said liquid from said partial slurry coating, thereby forming a drained partial slurry coating. Then applying a slurry composition over the discharged portion of the slurry coating to form a wetted slurry coating, discharging at least a portion of the liquid from the wetted slurry coating to form a discharged slurry coating, and applying a refractory stucco material over the discharged slurry coating, thereby forming a refractory stucco and a slurry coating, the improvement wherein the liquid binder composition comprises from 0.1 to 70 weight percent inorganic fiber. Preferably, the liquid binder composition further comprises 20 to 98 wt% of a sol containing inorganic particles and 1 to 20 wt% of an organic polymer, and the refractory powder comprises inorganic particles having an average particle size of less than 600 mesh. The inorganic fibers preferably have an average aspect ratio of greater than 30. Preferably, after drying, the composition is repeatedly applied to the mold to form a slurry coated mold, and a refractory mortar is applied to the slurry coated mold.
In accordance with a preferred embodiment of the present invention, there is provided a method of forming a shell mold comprising providing an investment casting shell mold composition comprising 0.1 to 70 weight percent inorganic fibers, providing a investment mold, applying said composition to said mold to form a binder coated mold, applying a refractory powder to said binder coated mold to form a binder and powder mold coating, the improvement comprising said binder composition. The investment casting shell mold composition preferably further comprises 1 to 20 wt% of an organic polymer.
According to a preferred embodiment of the present invention, there is provided a shell mold formed by a method comprising the steps of: providing an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 wt% of a sol containing inorganic particles, 1 to 20 wt% of an organic polymer, and 0.1 to 70 wt% of inorganic fibers, applying a refractory powder to the binder to form a slurry, providing a primer coated primary investment, applying the slurry composition to the mold to form a slurry coated mold, and discharging and applying a dried refractory mortar layer.
According to a preferred embodiment, the present invention provides a method of forming a shell mold, the method comprising: providing an investment casting shell mold composition comprising a primer binder composition comprising a mixture of 20 to 98 wt% of a sol containing inorganic particles and 1 to 20 wt% of an organic polymer; in providing a primary investment, applying said composition to said mold to form a binder coated mold having a binder coating, applying a refractory powder to said binder coated mold to form a binder and a powder mold coating, the improvement comprising adding from 0.1 to 70 weight percent inorganic fibers to said primer binder composition to form a fiber-containing primer binder composition. The primer binder composition preferably has an original modulus of rupture (MOR), the fiber-containing primer binder composition having an original modulus of rupture (MOR) that is at least 25% greater than the original modulus of rupture (MOR) of the primer binder composition. The primer binder composition preferably has an as-adjusted break load (AFL) that is at least 75% greater than the as-adjusted break load (AFL) of the primer binder composition. The primer binder composition preferably has an as-adjusted break load (AFL) that is at least 75% greater than the as-adjusted break load (AFL) of the primer binder composition. A fiber-free binder coating is preferably formed as the binder coating except that it is free of the fibers and is at least 25% thinner than the binder coating formed from the prime binder composition containing the fibers. The primer binder composition preferably has an original modulus of rupture (MOR), said fiber-containing primer binder composition having an original modulus of rupture (MOR) that is at least 35% greater than the original modulus of rupture (MOR) of said primer binder composition. The primer binder composition preferably has an as-adjusted break load (AFL) that is at least 100% greater than the as-adjusted break load (AFL) of the primer binder composition. The primer binder composition preferably has an original modulus of rupture (MOR), the fiber-containing primer binder composition having an original modulus of rupture (MOR) that is at least 50% greater than the original modulus of rupture (MOR) of the primer binder composition. The primer binder composition preferably has an as-adjusted break load (AFL) that is at least 150% greater than the as-adjusted break load (AFL) of the primer binder composition. A fiber-free binder coating is preferably formed as the binder coating except that it is free of the fibers and is at least 33% thinner than the binder coating formed from the primed binder composition containing the fibers. The fiber-free binder coating is preferably formed as the binder coating except that it is free of the fibers, it has a fiber-free original modulus of rupture, and the binder and powder mold coating have a fiber-containing original modulus of rupture that is at least 50% greater than the fiber-free original modulus of rupture. The fiber-free binder coating is preferably formed as the binder coating except that it is free of the fibers, it has a fiber-free raw adjusted breaking load, and the binder and powder mold coating have a fiber-containing raw adjusted breaking load that is at least 150% greater than the fiber-free raw modulus of rupture. The fiber-free binder coating is preferably formed as the binder coating except that it is free of the fibers, it has a fiber-free original modulus of rupture, and the binder and powder mold coating have a fiber-containing original modulus of rupture that is at least 25% greater than the fiber-free original modulus of rupture. The fiber-free binder coating is preferably formed as the binder coating except that it is free of the fibers, it has a fiber-free green adjusted breaking load, and the binder and powder mold coating have a fiber-containing green adjusted breaking load that is at least 100% greater than the fiber-free green modulus of rupture.
According to a preferred embodiment, the present invention provides a shell mold formed by a process comprising the steps of: providing an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 weight percent of a sol containing inorganic particles, 1 to 20 weight percent of an organic polymer, and 0.1 to 70 weight percent of inorganic fibers, applying said composition to a mold to form a binder-coated mold, applying a refractory powder to the binder-coated mold to form a binder and powder mold coating, and firing said binder and powder mold coating to form a shell mold.
According to a preferred embodiment, the present invention provides a green shell-mold formed by a method comprising the steps of: providing an investment casting shell mold composition comprising a binder composition comprising a mixture of 20-98 wt% of a sol containing inorganic particles, 1-20 wt% of an organic polymer, and 0.1 to 70 wt% of inorganic fibers, mixing a refractory powder with the binder to form a slurry composition, providing a primer coated primary investment, applying the slurry composition to a mold to form a wet slurry coating on the mold, draining at least a portion of the water from the wet slurry coating to form a drained slurry coating, applying a coarse refractory stucco to the drained slurry coating and removing the mold from the drained slurry coating, thereby forming an original shell mold.
The following examples describe preferred embodiments of the claimed invention. These examples should be considered as illustrating the invention without limiting its scope. Example 1: priming adhesive composition
60.29g of colloidal Silica (SiO)2: 10 nm average particle size); 18.96g of deionized water; 15.57g of acrylic Polymer emulsion: 55 wt% acrylic polymer; 45 wt% water; (Duramax TM B1000); 1.46g of inorganic fiber (Al)2O3And SiO2): it has a median length of 650 microns, a median diameter of 8.5 microns and a mean length to diameter (major diameter) ratio and composition of 80: 46 wt% SiO2、15wt％Al2O316 wt% CaO, 12 wt% MgO, 6 wt% FeO and 5 wt% impurities. Mixing the binder composition with a refractory powderThe combination forms a slurry of binder and powder. The refractory powder has a particle size of 120 mesh to 325 mesh. The refractory powder is molten SiO2Or Al2O3·SiO2。
Example 2
The wax pattern is dipped into a primer slurry for first pass coating of the refractory material, thereby forming a coated wax pattern. The coated wax pattern was immersed in the slurry of binder and powder formed according to the procedure of example 1 for about 5 seconds. The wax pattern is then lifted from the slurry and allowed to drain for 30-60 seconds. The wax pattern with the drained slurry layer was then coated with grit by dipping it into a fluidized bed of sand for about 5 seconds or by using a grit blaster that sprinkles stucco over the mold. The sand is made of fused SiO2Or Al2O3·SiO2And (4) forming. The mesh size of the sieve is 30 to 100 mesh. This step was repeated three times to form a coating having a width of about 5mm thick. The coated wax pattern is then melted by heating, the wax removed, and fired at a temperature of 1600 to 2000 ° F for about 1 to 3 hours. The final mold is used by pouring a liquid metal onto the mold, allowing the metal to cool, and then removing the mold from the cooled metal. The molded metals include iron, aluminum, nickel, and alloys thereof.
Example 3
60.85g of colloidal Silica (SiO)2: 10 nm average particle size); 19.64g deionized water; 15.71g acrylic Polymer emulsion: 55 wt% acrylic polymer; 45 wt% water; (Duramax TM B1000); 1.47g of an alkoxylated primary alcohol; LF-60MOD (wetting agent, manufactured by Defiest Enterprises Inc.); 0.49g of silicone emulsion DCH-10 (antifoaming agent, manufactured by Dow Corning); 0.02g of broad-spectrum bactericide; GROTAN (biocide, manufactured by US Professional Labs), 0.02g of a hydroxy compound; ammonia masking agent (perfume, manufactured by Alpine Aromatics International Inc.), 1.8g of inorganic fiber (Al)2O3And SiO2): it has a median length of 650 microns, a median diameter of 8.5 microns and a mean length to diameter (major diameter) ratio and composition of 80: 46 wt% SiO2、13.5wt％Al2O317.7 wt% CaO, 9.7 wt% MgO, 7 wt% FeO and 6.1 wt% others. The binder composition is mixed with a refractory powder. The refractory powder has a particle size of 120 mesh to 325 mesh. The refractory powder is molten SiO2。
Three primer binder slurries were prepared according to table I below. The Nyacol 830(NYA) system is described by Rancom&Randolph, a fiber-and polymer-free system marketed by Ranson&Customcote manufactured by RandolphTMThe binder (CUS) is a non-fibrous polymer-containing system and the CBS is said binder comprising fibres and polymer. Table I: formulation and viscosity of three slurries
| System ID | NYA | CUS | CSB |
| Adhesive agent | Nyacol830* | CustomcoteTMAdhesive agent | Primer adhesive composition of example 4 |
| Refractory material, addition amount (loading) | Ranco-Sil-140F, 63% addition | Ranco-Sil-140F, 63% addition | Ranco-Sil-140F, 62% addition |
| Viscosity of the oil | 13-15 seconds, # Zahn Cup | 10-12 seconds. # Zahn Cup | 23-25 seconds, # Zahn Cup |
Diluted with water to have binder solids 25.0 wt%.
All slurries were used to prepare test bar samples for green strength determination. All systems used 30 x 50 fused silica stucco sand. The green bending strength is given in table II. For reference, all data were measured in three primer coats and one closed dip coat (Seal dip) against the NYA system (i.e., this point equals 1). Table II: relative raw bend performance of three systems with various coatings
| Performance → architecture ↓ | Thickness of | Original MOR | Original AFL | |
| 3 coating + sealing layer | NYA | 1.00 | 1.00 | 1.00 |
| CUS | 0.94 | 1.63 | 1.46 | |
| CSB | 1.44 | 2.83 | 5.92 | |
| 4 layers + sealing layers | NYA | 1.19 | 1.55 | 2.20 |
| CUS | 1.20 | 2.03 | 2.97 | |
| CSB | 1.78 | 2.98 | 9.50 | |
| 5 coating + sealing layer | NYA | 1.44 | 1.70 | 3.56 |
| CUS | 1.35 | 2.46 | 4.53 | |
| CSB | 2.10 | 3.29 | 14.72 | |
As can be seen from table II, the original MOR and AFL (2.83 and 5.92, respectively) of the CSB system in the three-layer coating were greater than NYA and the CUS system in the 4 and 6-layer primer coating were the same. This demonstrates that a 3-layer primer coat of CSB slurry can replace the 4 and 5-layer coats of NYA and CUS slurry.
Investment casting shell mold compositions useful in the present invention are organic and inorganic fibers. Inorganic fibers are most preferred. Fibers useful in the investment casting shell mold composition most preferably have an average aspect ratio of greater than 30.
The particles useful in the investment casting shell mold composition of the present invention are organic and inorganic particles. Inorganic particles are most preferred. The particles useful in the investment casting shell mold composition of the present invention preferably have an average maximum diameter of less than 1 micron. The particles useful in the investment casting shell mold composition of the present invention most preferably have an average maximum diameter of less than 0.5 microns.
While the invention has been described with reference to various preferred embodiments, those skilled in the art will recognize that various changes and modifications can be made without departing from the spirit and scope of the invention, as defined in the appended claims.
Claims (37)
1. An investment casting shell mold composition comprising a binder composition comprising a mixture of 20-98 wt% of a sol containing inorganic particles, 1-20 wt% of an organic polymer, and 0.1 to 70 wt% of inorganic fibers; wherein the inorganic particles have an average particle size of less than 600 mesh and the inorganic fibers have an average aspect ratio of greater than 30.
2. The composition of claim 1, further comprising 1 to 90 wt% of a refractory powder.
3. The composition of claim 2, wherein the refractory powder has a mesh size of 120 to 140 mesh and is selected from the group consisting of aluminosilicates, fused silica, quartz silica, alumina, zircon and zirconia.
4. The composition according to claim 1, wherein the colloidal silica comprises silica having an average particle size of from 3 to 100 nanometers.
5. The composition of claim 1, wherein the ratio of colloidal silica to latex polymer is greater than 1: 1.
6. A composition according to claim 1 wherein the ratio of colloid to latex is from 10: 1 to 1: 1.
7. The composition according to claim 1, wherein the latex polymer comprises a blend of acrylic polymers having the following properties: the pH is 6-11; viscosity 50-1000 centipoise; the solid content is 40-65%; the average particle size is 0.05-1.0 micron.
8. The composition according to claim 1, wherein the latex polymer comprises a blend of acrylic polymers having the following properties: the pH value is 7-10; viscosity 50-500 centipoise; solid content is 50-60%; the average particle size is 0.1-0.5 micron.
9. The composition of claim 1, wherein the polymer latex is an acrylic latex or a styrene butadiene latex.
10. The composition according to claim 1, wherein the silica sol has an average particle size of less than 30 nanometers.
11. The composition according to claim 1, wherein the latex polymer is an elastomeric latex polymer.
12. The composition according to claim 1, further comprising 1 to 98 wt% of water.
13. A method of forming a shell mold comprising the steps of:
providing an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 weight percent of a sol comprising inorganic particles, 1 to 20 weight percent of an organic polymer, and 0.1 to 70 weight percent of inorganic fibers;
the inorganic particles having an average particle size of less than 600 mesh, the inorganic fibers having an average aspect ratio of greater than 30,
providing a primary melting mold,
mixing a refractory powder with the binder composition to form a slurry composition,
applying the slurry composition to the mold to form a slurry coating on the slurry coated mold,
a refractory mortar is applied over the slurry coating to form a slurry and plaster mold coating.
14. The method of claim 13, wherein the refractory powder has a particle size of 120 to 400 mesh.
15. A method of forming a shell mold comprising providing an investment casting shell mold composition comprising a liquid binder composition; mixing a refractory powder with a binder to form a slurry composition, providing a primer coated primary investment, applying the slurry composition to a mold to form a partial slurry coating on said mold, draining at least a portion of said liquid from said partial slurry coating, thereby forming a drained partial slurry coating,
in the improvement wherein a slurry composition is applied to the discharged portion of the slurry coating to form a wetted slurry coating, at least a portion of the liquid is discharged from the wetted slurry coating to form a discharged slurry coating, and a refractory stucco material is applied to the discharged slurry coating, thereby forming a refractory stucco and a slurry coating, the liquid binder composition including from 0.1 to 70 weight percent inorganic fiber.
16. The method of claim 15, wherein the liquid binder composition further comprises 20 to 98 wt% of a sol containing inorganic particles and 1 to 20 wt% of an organic polymer, and the refractory powder comprises inorganic particles having an average particle size of less than 600 mesh.
17. The method of claim 15, wherein the inorganic fibers have an average aspect ratio greater than 30.
18. The method of claim 15, wherein the applying the composition to the mold to form a slurry coated mold is repeated after drying and the refractory stucco is applied to the slurry coated mold.
19. In a method of forming a shell mold comprising providing an investment casting shell mold composition comprising 0.1 to 70 weight percent inorganic fibers, providing a investment mold, applying said composition to the mold to form a binder coated mold, applying a refractory powder to said binder coated mold to form a binder and powder mold coating, the improvement comprising the binder composition.
20. The method of claim 19 wherein said investment casting shell mold composition further comprises from 1 to 20 weight percent of an organic polymer.
21. A shell mold formed by a method comprising: providing an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 wt% of a sol containing inorganic particles, 1 to 20 wt% of an organic polymer, and 0.1 to 70 wt% of inorganic fibers, applying a refractory powder to the binder to form a slurry, providing a primer coated primary investment, applying the slurry composition to the mold to form a slurry coated mold, and discharging and applying a dried refractory mortar layer.
22. A method of forming a shell mold, comprising: providing an investment casting shell mold composition comprising a primer binder composition comprising a mixture of 20 to 98 wt% of a sol containing inorganic particles and 1 to 20 wt% of an organic polymer; in providing a primary investment, applying said composition to said mold to form a binder coated mold having a binder coating, applying a refractory powder to said binder coated mold to form a binder and a powder mold coating, the improvement comprising adding from 0.1 to 70 weight percent inorganic fibers to said primer binder composition to form a fiber-containing primer binder composition.
23. The method of claim 22 wherein said primer binder composition has an original modulus of rupture (MOR) and said fiber-containing primer binder composition has an original modulus of rupture (MOR) that is at least 25% greater than the original modulus of rupture (MOR) of said primer binder composition.
24. The method according to claim 22, wherein the primer binder composition has an as-adjusted break load (AFL) and the fiber-containing primer binder composition has an as-adjusted break load (AFL) that is at least 75% greater than the as-adjusted break load (AFL) of the primer binder composition.
25. The method according to claim 22, wherein the primer binder composition has an as-adjusted break load (AFL) and the fiber-containing primer binder composition has an as-adjusted break load (AFL) that is at least 75% greater than the as-adjusted break load (AFL) of the primer binder composition.
26. The method of claim 22 wherein a fiber-free binder coating is formed as said binder coating except that said fibers are absent and at least 25% thinner than said binder coating formed from said primed binder composition comprising said fibers.
27. The method of claim 22 wherein said primer binder composition has an original modulus of rupture (MOR) and said fiber-containing primer binder composition has an original modulus of rupture (MOR) that is at least 35% greater than the original modulus of rupture (MOR) of said primer binder composition.
28. The method of claim 22 wherein the primer binder composition has an as-adjusted break load (AFL) and the fiber-containing primer binder composition has an as-adjusted break load (AFL) that is at least 100% greater than the as-adjusted break load (AFL) of the primer binder composition.
29. The method of claim 22 wherein said primer binder composition has an original modulus of rupture (MOR) and said fiber-containing primer binder composition has an original modulus of rupture (MOR) that is at least 50% greater than the original modulus of rupture (MOR) of said primer binder composition.
30. The method according to claim 22, wherein the primer binder composition has an as-adjusted break load (AFL) and the fiber-containing primer binder composition has an as-adjusted break load (AFL) that is at least 150% greater than the as-adjusted break load (AFL) of the primer binder composition.
31. The method of claim 22 wherein a fiber-free binder coating is formed as said binder coating except that said fibers are absent and said fiber-free binder coating is at least 33% thinner than said binder coating formed from a primer binder composition comprising said fibers.
32. The method of claim 22 wherein a fiber-free binder coating is formed as said binder coating except that it is free of said fibers, it has a fiber-free original modulus of rupture, and said binder and powder mold coating have a fiber-containing original modulus of rupture that is at least 50% greater than said fiber-free original modulus of rupture.
33. The method of claim 22 wherein a fiber-free binder coating is formed as the binder coating except that it is free of the fibers, it has a fiber-free raw adjusted breaking load, and the binder and powder mold coating have a fiber-containing raw adjusted breaking load that is at least 150% greater than the fiber-free raw modulus of rupture.
34. The method of claim 22 wherein a fiber-free binder coating is formed as the binder coating except that it is free of the fibers, it has a fiber-free original modulus of rupture, and the binder and powder mold coating have a fiber-containing original modulus of rupture that is at least 25% greater than the fiber-free original modulus of rupture.
35. The method of claim 22 wherein a fiber-free binder coating is formed as said binder coating except that it is free of said fibers, it has a fiber-free green adjusted breaking load, and said binder and powder mold coating have a fiber-containing green adjusted breaking load that is at least 100% greater than the fiber-free green modulus of rupture.
36. A shell mold formed by a method comprising: providing an investment casting shell mold composition comprising a binder composition comprising a mixture of 20 to 98 weight percent of a sol containing inorganic particles, 1 to 20 weight percent of an organic polymer, and 0.1 to 70 weight percent of inorganic fibers, applying the composition to a mold to form a binder coated mold, applying a refractory powder to the binder coated mold to form a binder and powder mold coat, and firing the binder and powder mold coat to form a shell mold.
37. A raw shell mold formed by a method comprising the steps of: providing an investment casting shell mold composition comprising a binder composition comprising a mixture of 20-98 wt% of a sol containing inorganic particles, 1-20 wt% of an organic polymer, and 0.1 to 70 wt% of inorganic fibers, mixing a refractory powder with the binder to form a slurry composition, providing a primer coated primary investment, applying the slurry composition to a mold to form a wet slurry coating on the mold, draining at least a portion of the water from the wet slurry coating to form a drained slurry coating, applying a coarse refractory stucco to the drained slurry coating and removing the mold from the drained slurry coating, thereby forming an original shell mold.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US60/150,626 | 1999-08-25 | ||
| US60/151,832 | 1999-09-01 | ||
| US09/527,047 | 2000-03-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| HK1048274A true HK1048274A (en) | 2003-03-28 |
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