Abstract: The invention relates to a investment casting molds and their method of manufacture. The method entails mixing refractory fiber, glass fiber, and refractory filler to form a dry blend; mixing the dry blend with an aqueous colloidal silica sol to form a refractory prime coat slurry, and employing the refractory slurry to produce an investment casting mold.

Abstract: Molds are fabricated having a substrate of high density, high strength ultrafine grained isotropic graphite, and having a mold cavity coated with titanium carbide. The molds may be made by making the substrate (main body) of high density, high strength ultrafine grained isotropic graphite, by, for example, isostatic or vibrational molding, machining the substrate to form the mold cavity, and coating the mold cavity with titanium carbide via either chemical deposition or plasma assisted chemical vapor deposition, magnetron sputtering or sputtering. The molds may be used to make various metallic alloys such as nickel, cobalt and iron based superalloys, stainless steel alloys, titanium alloys and titanium aluminide alloys into engineering components by melting the alloys in a vacuum or under a low partial pressure of inert gas and subsequently casting the melt in the graphite molds under vacuum or low partial pressure of inert gas.

Abstract: Methods for making various metallic alloys such as nickel, cobalt and/or iron based superalloys, stainless steel alloys, titanium alloys and titanium aluminide alloys into engineering components by melting of the alloys in a vacuum or under a low partial pressure of inert gas and subsequent casting of the melt in the graphite molds under vacuum or low partial pressure of inert gas are provided, the molds having been fabricated by machining high density, high strength ultrafine grained isotropic graphite, wherein the graphite has been made by isostatic pressing or vibrational molding.

Abstract: One method of the present invention includes introducing a slurry into a mold unit comprised of a mold contained within a casting receptacle and lowering the temperature of the slurry to freeze the slurry and form a freeze-cast substrate while controlling temperature gradients within the mold unit to minimize distortion in the freeze-cast substrate. Another method includes introducing a slurry into a mold unit comprised of a mold contained within a casting receptacle, placing insulation material around at least a portion of the casting receptacle to minimize distortion in the freeze-cast substrate by controlling temperature gradients within the mold unit, and lowering the temperature of the slurry to freeze the slurry to form a freeze-cast substrate.

Abstract: Methods for making molding casts by a process typically referred to as “investment casting” using a novel composition is described. The composition is a phosphate bonded material that contains mono-ammonium phosphate (MAP), magnesium oxide and silica filler (quartz, cristobalite, or a mixture thereof). It has been discovered that controlling the amount and ratio of these components has a significant impact on gas permeability (porosity), set time, cast smoothness and cast softness. The most outstanding feature of the new investments is the short mold fabrication and processing time that they allow due to their high gas permeability. The investments can be placed in a burn out furnace while still wet and can be heated rapidly to the firing temperature. The casts can be broken by sandblasting the casts with glass beads. Molds made from the casts have smooth surfaces indicating that the casts are free of visible inclusions and other defects.

Abstract: Methods and materials for preparing investment molds useful in pressure infiltration casting of near net-shape metal or metal matrix composite (MMC) components. One embodiment of the invention includes disposing a slurry of an appropriately sized refractory material and a vehicle around a preform or fugitive pattern, removing the bulk of the vehicle, then curing/drying the refractory material to create an investment mold of the invention. Subsequently, pressure infiltration casting with a molten infiltrant using the investment mold permits infiltration of the mold cavity and/or preform without infiltration of the investment mold. As a result, the investment mold readily is removed to provide the near net-shape metal or MMC component. In other embodiments of the invention, a non-fugitive pattern is used, typically with a modified refractory cement of the invention.

Abstract: The present invention relates to improvements in and relating to investment casting. In particular, the invention provides a method of investment casting, comprising the steps of mixing a binder, a refractory material, and a quantity of water-insoluble organic fibres to form a slurry; coating an expendable pattern with a coat of said slurry; and drying said coat or allowing said coat to dry to form a shell. The present invention further provides a refractory slurry for use in the method of the invention, and a kit of ingredients for putting the method of the invention into effect.

Abstract: A method of making a ceramic shell mold comprises repeatedly coating a fugitive pattern of an article to be cast with a ceramic slurry layer and applying on the ceramic slurry layer a refractory stucco to form a plurality of ceramic slurry layers and stucco layers on the pattern wherein at least one of the stucco layers is formed by applying discontinuous stucco fiber bundles held together in the bundles by a fugitive binder, which is removed during subsequent firing of the shell mold at elevated temperature.

Abstract: A method of investment casting is disclosed, which comprises the preparation of a refractory slurry by mixing a binder, a refractory material, and a quantity of water-insoluble organic fibres, and the application of one or more coats of this slurry to an expendable pattern, so as to build up a shell. It has been found that each coat of the slurry thus formed is surprisingly thick, and that a relatively short drying time is required for each coat, hence enabling a shell of desirable thickness to be rapidly built in a small number of “dipping cycles”. The invention also encompasses a kit of ingredients for putting the method of the invention into effect; a shell produced in accordance with this method; and a refractory slurry for use in this method.

Abstract: A method of making a ceramic shell mold comprises repeatedly coating a fugitive pattern of an article to be cast with a ceramic slurry layer and applying on the ceramic slurry layer a refractory stucco to form a plurality of ceramic slurry layers and stucco layers on the pattern wherein at least one of the stucco layers is formed by applying discontinuous stucco fibers followed by applying a granular stucco particles on the discontinuous stucco fibers.

Abstract: A method of making a ceramic shell mold comprises repeatedly coating a fugitive pattern of an article to be cast with a ceramic slurry layer and applying on the ceramic slurry layer a refractory stucco to form a plurality of ceramic slurry layers and stucco layers on the pattern wherein at least one of the stucco layers is formed by applying discontinuous stucco fibers followed by applying a granular stucco particles on the discontinuous stucco fibers.

Abstract: The present invention relates to improvements in and relating to investment casting. In particular, the invention provides a method of investment casting, comprising the steps of mixing a binder, a refractory material, and a quantity of water-insoluble organic fibres to form a slurry; coating an expendable pattern with a coat of said slurry; and drying said coat or allowing said coat to dry to form a shell. The present invention further provides a refractory slurry for use in the method of the invention, and a kit of ingredients for putting the method of the invention into effect.

Abstract: A method for imaging inclusions in metal or metal alloy castings is described. One embodiment of the present method first involves casting a metal or metal alloy article using an investment casting mold where the mold facecoat, and perhaps one or more of the mold backup layers, comprises an imaging agent distributed substantially uniformly throughout in amounts sufficient for imaging inclusions. The facecoat preferably comprises an intimate mixture of a refractory material and the imaging agent. Intimate mixtures can be produced in a number of ways, but a currently preferred method is to cocalcine the refractory material, such as yttria, with the imaging agent, such as gadolinia. The facecoat also can comprise plural mold-forming materials and/or plural imaging agents. The difference between the linear attenuation coefficient of the article and the linear attenuation coefficient of the imaging agent should be sufficient to allow imaging of the inclusion throughout the article.

Abstract: The invention relates to a investment casting molds and their method of manufacture. The method entails mixing refractory fiber, glass fiber, and refractory filler to form a dry blend; mixing the dry blend with an aqueous colloidal silica sol to form a refractory prime coat slurry, and employing the refractory slurry to produce an investment casting mold.

Abstract: Methods for making molding casts by a process typically referred to as “investment casting” using a novel composition is described. The composition is a phosphate bonded material that contains mono-ammonium phosphate (MAP), magnesium oxide and silica filler (quartz, cristobalite, or a mixture thereof). It has been discovered that controlling the amount and ratio of these components has a significant impact on gas permeability (porosity), set time, cast smoothness and cast softness. The most outstanding feature of the new investments is the short mold fabrication and processing time that they allow due to their high gas permeability. The investments can be placed in a burn out furnace while still wet and can be heated rapidly to the firing temperature. The casts can be broken by sandblasting the casts with glass beads. Molds made from the casts have smooth surfaces indicating that the casts are free of visible inclusions and other defects.

Abstract: A ceramic mould slurry is disclosed for forming moulds and metal castings of improved surface quality. The slurry comprises a binder, a gelling agent, a first refractory material having a density of &rgr;1 and a mean particle size of &agr;1, and a second refractory material having a density of &rgr;2 and a mean particle size of &agr;2, wherein &rgr;1>&rgr;2 and &agr;1<&agr;2. The denser refractory material migrates downward through the slurry toward the upward-facing mould surface, thereby allowing formation of a smooth and accurate surface.

Abstract: A method of investment casting is disclosed, which comprises the preparation of a refractory slurry by mixing a binder, a refractory material, and a quantity of water-insoluble organic fibres, and the application of one or more coats of this slurry to an expendable pattern, so as to build up a shell. It has been found that each coat of the slurry thus formed is surprisingly thick, and that a relatively short drying time is required for each coat, hence enabling a shell of desirable thickness to be rapidly built in a small number of “dipping cycles”. The invention also encompasses a kit of ingredients for putting the method of the invention into effect; a shell produced in accordance with this method; and a refractory slurry for use in this method.

Abstract: A ceramic investment shell mold is reinforced with a carbon based fibrous reinforcement having an extremely high tensile strength that increases as the mold temperature is increased especially within the range of casting temperatures employed for casting large directionally solidified industrial gas turbine components. The carbon based fibrous reinforcement is wrapped or otherwise positioned around the repeating ceramic slurry/stucco layers forming the intermediate thickness of the shell mold wall. The reinforced shell mold can be used to cast large directionally solidified industrial gas turbine components with accurate dimensional control.

Abstract: The strength and solids level of an investment casting shell is increased by incorporating at least one microsilica into the shell.

Abstract: The present invention relates to improvements in and relating to investment casting. In particular, the invention provides a method of investment casting, comprising the steps of mixing a binder, a refractory material, and a quantity of water-insoluble organic fibers to form a slurry; coating an expendable pattern with a coat of said slurry; and drying said coat or allowing said coat to dry to form a shell. The present invention further provides a refractory slurry for use in the method of the invention, and a kit of ingredients for putting the method of the invention into effect.

Abstract: A ceramic casting shell mold having a pre-selected shape comprises alternate, repeating layers of a ceramic coating material and a ceramic stucco, defining a total thickness of the shell mold; and a ceramic-based reinforcing sheet disposed in the alternate, repeating layers of coating material and stucco at an intermediate thickness. The ceramic-based reinforcing sheet comprises a one-piece monolithic, integral body, which comprises a pattern of holes that enhance bonding between the ceramic-based reinforcing sheet and adjacent ones of the alternate, repeating layers of ceramic coating material. The ceramic-based reinforcing sheet conforms to the shape of the mold and providing structural reinforcement to the mold.

Abstract: A ceramic investment shell mold is reinforced with a carbon based fibrous reinforcement having an extremely high tensile strength that increases as the mold temperature is increased especially within the range of casting temperatures employed for casting large directionally solidified industrial gas turbine components. The carbon based fibrous reinforcement is wrapped or otherwise positioned around the repeating ceramic slurry/stucco layers forming the intermediate thickness of the shell mold wall. The reinforced shell mold can be used to cast large directionally solidified industrial gas turbine components with accurate dimensional control.

Abstract: The present invention relates to improvements in and relating to investment casting. In particular, the invention provides a method of investment casting, comprising the steps of mixing a binder, a refractory material, and a quantity of water-insoluble organic fibers to form a slurry; coating an expendable pattern with a coat of said slurry; and drying said coat or allowing said coat to dry to form a shell. The present invention further provides a refractory slurry for use in the method of the invention, and a kit of ingredients for putting the method of the invention into effect.

Abstract: Methods for increasing the lifetime of a casting slurry are described. One feature of the invention is processing refractory powders at a first hydration level to produce powders having a second, lower hydration level before the processed materials are used to form casting slurries. Processing according to the disclosed methods results in a substantial increase in the lifetime of a slurry made using such processed materials compared to slurries made using materials not processed as described herein. One embodiment of the method comprises heat processing at least one refractory powder, typically refractory powders which have undergone hydration subsequent to commercial production, for a period of time sufficient to reduce the amount of hydration from a first hydration level to a second hydration level. A slurry is formed using the refractory powder at an hydration level which provides an increased slurry lifetime relative to the same material without processing according to the method of the present invention.

Abstract: A ceramic investment shell mold is reinforced with a carbon based fibrous reinforcement having an extremely high tensile strength that increases as the mold temperature is increased especially within the range of casting temperatures employed for casting large directionally solidified industrial gas turbine components. The carbon based fibrous reinforcement is wrapped or otherwise positioned around the repeating ceramic slurry/stucco layers forming the intermediate thickness of the shell mold wall. The reinforced shell mold can be used to cast large directionally solidified industrial gas turbine components with accurate dimensional control.

Abstract: A ceramic casting shell mold having a pre-selected shape is described. The shell mold comprises repeating layers of a ceramic material which define its wall thickness and shape. At least one of the layers of ceramic material contains refractory whiskers which provide structural reinforcement to the shell mold. The whiskers are usually incorporated into a layer of the ceramic material which is disposed at a position off-center of the wall-thickness of the mold. A method for making a ceramic casting shell mold is also described, as are metal- or metal alloy components cast in these shell molds.

Abstract: A method for fabricating a fired ceramic article, a green product, and a fired ceramic article, all for use as a core in the investment casting of directionally solidified eutectic and superalloy material. A ceramic slurry is prepared of alumina, aluminum and a solution of a polymerizable binder in a liquid. The slurry is extruded under low pressure into a closed cavity to form a gelled green product which is subsequently heated in an oxygen-containing atmosphere, wherein the oxygen reacts with the aluminum in the green product to form alumina which advantageously causes an increase in volume of the green product which counters the shrinkage effects of heating.

Abstract: A disposable plunger for use in a pressing furnace for the fabrication of dental restorations. The plunger is fabricated of a refractory investment material such as gypsum-bonded, phosphate-bonded or ethyl silicate-bonded investment materials. The plunger is fabricated by known casting methods. The mold used for making the plunger can be supplied by a manufacturer of molds or can be easily made by using an alumina or similar plunger as a model. Laborious cleaning and grinding are not required with plungers herein described. Cracking problems that occur with prior art plungers are decreased, if not completely eliminated.

Abstract: Method of making a casting by investment casting of a metal or alloy, especially titanium and its alloys, in a ceramic investment shell mold in a manner to provide enhanced x-ray detectability of any sub-surface ceramic inclusions that may be present below exterior surfaces of the casting. The method involves forming a ceramic mold facecoat and/or back-up layer including erbia or other x-ray or neutron-ray detectable ceramic component. The facecoat/back-up layer is/are formed using a ceramic slurry comprising erbia and other optional ceramic particulates, an inorganic binder, and an inorganic pH control agent. The slurry is applied to a pattern of component to be cast to form the mold. A metal or alloy is cast in the mold, and the solidified casting is removed from the mold. The casting is subjected to radiography to detect any sub-surface ceramic inclusions below the exterior surface thereof not detectable by visual inspection of the casting.

Abstract: A method for fabricating a fired ceramic article, a green product, and a fired ceramic article, all for use as a core in the investment casting of directionally solidified eutectic and superalloy material. A ceramic slurry is prepared of alumina, aluminum and a solution of a polymerizable binder in a liquid. The slurry is extruded under low pressure into a closed cavity to form a gelled green product which is subsequently heated in an oxygen-containing atmosphere, wherein the oxygen reacts with the aluminum in the green product to form alumina which advantageously causes an increase in volume of the green product which counters the shrinkage effects of heating.

Abstract: A golf ball mold is prepared by inserting a dimpled hemispherical male die into a chamber in a frame, admitting hot liquid wax into the chamber, cooling and curing the wax to form a wax shape, covering the wax shape with a mix slurry of ceramic particles and a binder, drying and curing the slurry to form a ceramic shell around the wax shape, removing the wax shape from the ceramic shell, casting a molten metal into the ceramic shell, cooling and solidifying the metal to form a mold half, and removing the ceramic shell from the mold half. The mold is improved in molding precision, durability and cost.

Abstract: A method to suppress displacement of the core during casting when making hollow blades by applying the lost wax method using a core. A wax pattern is made which comprises a core and a layer of wax covering the core. Then at least one pin of the same material as the blade is inserted into the wax layer such that this pin engages the core and part of the pin projects from the outer surface of the wax layer, after which, with the portion of the pin which projects from the outer surface of the wax layer being held in a casting mold, the wax is removed, followed by casting.

Abstract: A method of making a metal shape comprising the steps of supplying molten metal into a ceramic shell mould mounted in a container, spinning the container and the shell mould therein about an axis and permitting the metal to solidify in the shell mould and thereafter removing, for example by breaking, the shell mould to expose the metal shape. The ceramic shell moulds made by providing a pattern of flexible elastically deformable material of a required shape and supported on a mandrel, applying at least one coating of hardenable refractory material to said pattern to form a rigid shell and removing the mandrel from supporting relationship with the pattern and subsequently removing the pattern from the shell by elastically deforming the pattern. The pattern is made by moulding said material in a master mould of a required shape and removing the pattern from the master mould, after the pattern has set, by elastically deforming the pattern.

Abstract: A technique for smoothing and otherwise changing the surfaces of porous bodies, such as ceramic molds, made using layer manufacturing processes, such as three dimensional printing processes. The surface finish of the mold can be smoothed by casting a slip of fine particles onto the surface to form a generally level, and preferably non-conformal, coating on the surfaces. In general, the fine particles of the slip are caused to be filtered out from the liquid, so that the fine particles come to rest at or near the surface of the body formed. They are typically, preferentially drawn toward concave regions of the surface, as compared to convex regions, thereby forming a non-conformal coating. Furthermore, other surface properties can be changed by tailoring the slip to produce those properties. The coating can be applied to external surfaces, and internal surfaces, such as would become the surface against which a molded part would be formed.

Abstract: A metal or metal alloy article is cast using an investment casting mold where the mold facecoat, and perhaps one or more of the mold backup layers, comprises an imaging agent distributed substantially uniformly throughout in amounts sufficient for imaging inclusions. The facecoat preferably comprises an intimate mixture of a refractory material and the imaging agent. Intimate mixtures can be produced in a number of ways, but a currently preferred method is to cocalcine the refractory material, such as yttria, with the imaging agent, such as gadolinia. The facecoat also can comprise plural mold-forming materials and/or plural imaging agents. The difference between the linear attenuation coefficient of the article and the linear attenuation coefficient of the imaging agent should be sufficient to allow imaging of the inclusion throughout the article. The metal or metal alloy article is then analyzed for inclusions by N-ray analysis.

Abstract: Investment casting shells, methods for their manufacture and methods for casting metals and alloys using such shells are disclosed. One feature of the shells is that the facecoat plus interior backup layers are purposefully designed to have substantially similar coefficients of thermal expansion to the seal dip layers. This helps reduce the occurrence of dimensional casting defects caused by differential thermal expansions of the layers comprising the shell. One embodiment of such a shell comprises a facecoat, plural interior backup layers and plural intermediate backup layers wherein at least one of the plural intermediate backup layers comprises a material capable of undergoing a volumetric transformation during cool down, and wherein the seal-dip layers have a coefficient of thermal expansion that varies from the coefficient of thermal expansion of the facecoat and interior backup layers by less than about 10 percent.

Abstract: Method of making a casting by investment casting of a metal or alloy, especially titanium and its alloys, in a ceramic investment shell mold in a manner to provide enhanced x-ray detectability of any sub-surface ceramic inclusions that may be present below exterior surfaces of the casting. The method involves forming a ceramic mold facecoat and/or back-up layer including erbia or other x-ray or neutron-ray detectable ceramic component. The facecoat/back-up layer is/are formed using a ceramic slurry comprising erbia and other optional ceramic particulates, an inorganic binder, and an inorganic pH control agent. The slurry is applied to a pattern of component to be cast to form the mold. A metal or alloy is cast in the mold, and the solidified casting is removed from the mold. The casting is subjected to radiography to detect any sub-surface ceramic inclusions below the exterior surface thereof not detectable by visual inspection of the casting.

Abstract: Ceria is used to assure release between a metal workpiece and associated forming tooling in forming operations conducted at temperatures of 1500.degree. F. (816.degree. C.) and above.

Abstract: Mold coatings that are relatively unreactive with titanium and titanium alloys during casting are prepared from yttria slurries, which may contain other refractory materials, an acid and an inert organic solvent.

Abstract: Methods and compositions for forming shells for investment casting and methods for casting metal articles using the shells are described. One embodiment of the method comprises serially immersing a pattern in at least one, and perhaps several different slurries, each of which slurries comprises refractory material and from about 0 to about 30 volume percent inorganic binder. This forms a facecoat and plural refractory backup layers about the pattern, the facecoat and at least one backup layer defining a shell. The facecoat and/or the shell is then infiltrated with a binder. Infiltrating the shell with a binder is a key feature of the present invention. Infiltration refers to any process whereby a binder can be introduced into the facecoat and/or the subsequent layers built up about the shell.

Abstract: The stem is cast about an irregular plug body, which is then removed, leaving a wall thickness that satisfies the opposing constraints of high strength and relatively low stiffness. The plug narrows the prosthesis wall thickness in upper regions thereof and strengthens the wall about regions of recessed or discontinuous features, or high load coupling, to assure that the stem has adequate strength in regions of high strain, while effectively coupling strain to surrounding bone. The prosthesis is produced in a range of sizes, and plugs or entire molds for casting the hollow body are readily made and modified by a three-dimensional printing mold fabrication technique.

Abstract: A calcia mold facecoat is applied to a mold for casting parts composed of reactive metals such as titanium and titanium aluminide. The facecoat is composed of a calcium carbonate based slurry comprising a dense grain calcium carbonate powder and an aqueous based binder. It is applied to a wax or plastic pattern used in the lost wax process for fabricating a casting shell. The mold is built using multiple dipping of alumina-silicate slurries, and then fired at high temperatures in an oxygen rich environment. The metal part is cast before the fired mold can cool below about 800.degree. C. Organometallic based slurry binders are avoided and significant cost savings are realized owing to the benign nature of the aqueous based suspensions with respect to the environment.

Abstract: Cores that are relatively unreactive with titanium and titanium alloys during casting are prepared from yttria slurries, which may contain other refractory materials, an acid and an inert organic solvent.

Abstract: An investment casting process which includes: attaching a gate to a pattern made of a plastic to form a pattern assembly; forming a mold by applying a plaster slurry on an outer surface of the pattern assembly; dissolving and removing the pattern assembly in the mold by applying an organic solvent; burning the mold from which the pattern has been removed; casting by pouring a molten metal into the burned mold; and breaking the mold to take out a cast product.

Abstract: Time-stable yttria slurries, and a method for forming such yttria slurries and articles therefrom are described. The method involves forming an intimate mixture comprising yttria and at least about 0.1 weight percent of a dopant material. An aqueous slurry is then formed comprising from about 1 weight percent to about 95 weight percent of the intimate mixture. The intimate mixture may be formed by heating the mixture to a temperature sufficient to calcine the mixture. Alternatively, the intimate mixture may be formed by heating the mixture to a temperature sufficient to fuse the mixture. The dopant also may be provided as a surface coating on the yttria particles.

Abstract: Mold coatings that are relatively unreactive with titanium and titanium alloys during casting are prepared from yttria slurries, which may contain other refractory materials, an acid and an inert organic solvent.

Abstract: The present invention pertains to a process for preparing ceramic shells as casting molds, wherein a) a pattern of a part to be cast, which pattern can be melted or dissolved out, is prepared, b) the pattern is dipped into a dip-coating composition of a slurry of a refractory material and a binder in order to form a wet coating on the pattern, c) a coarse refractory powder is sprinkled onto the coating, d) the coating is dried, and e) steps b), c) and d) are repeated until the mold shell has reached the desired thickness. A ceramic protective material is added to the dip-coating composition and/or to the coarse refractory powder. Carbon is introduced into the ceramic protective material during the preparation in the molten state. The carbon is able to chemically bind oxygen at the time of the cooling of the casting essentially at mold temperatures above the firing temperature of the casting mold and is thus able to prevent skin decarburization and surface defects in carbon-containing steels.

Abstract: The disclosure describes an aqueous ceramic slurry having from about 70-weight percent to about 85 weight-percent of a fused yttria-zirconia material. The weight percent of zirconia in the fused yttria-zirconia preferably varies from about 1.0 weight percent to about 10.0 weight percent. Fused slurries may comprise, in addition to fused yttria-zirconia, an inorganic binder (preferably silica), an organic binder (preferably a latex binder), a surfactant (preferably a sodium dioctyl sulfosuccinate), an antifoaming agent (preferably a water-dilutable active silicone defoamer) and titanium dioxide. The slurries of the present invention are used to form ceramic mold facecoatings for casting reactive materials. These slurries are less sensitive to pH fluctuations than are slurries made from 100 percent yttria (yttria slurries). Moreover, slurries as described in the disclosure do not gel prematurely, and exhibit substantially the same formation of oxygen-enriched titanium (alpha case) than do yttria slurries.

Abstract: Emissive compositions are described that can be applied as a coating to the surface of an investment casting mold to increase or decrease the rate of cooling of a casting within the mold. A coating that decreases the rate of cooling of an investment casting within an investment casting mold may comprise a compound having an emissivity less than the emissivity of the mold; a high temperature glass-forming material and a solvent to make a slurry. Similarly, a coating that increases the rate of cooling may comprise a compound having an emissivity greater than the emissivity of the mold; a low temperature glass-forming material and a solvent to make a slurry. Also disclosed in a method of investment casting wherein an emissive composition is applied to the investment casting mold.

Abstract: Dental investment materials for providing inexpensive dental investments which are free from the occurrence of cracks, crevices or breakage and can greatly reduce the metal casting time, dental casting molds using the same and a process for burning them. The dental investment material contains as the major components a calcined gypsum powder, a cristobalite powder and a quartz powder and additionally contains a gas permeability improving additive. In the dental investment prepared using such dental investment material, the thermal expansion can be dispersed and the steam pressure generated can be released effectively during calcination and burning.