MXPA00007888A - Investment casting mold and method of manufacture - Google Patents

Abstract

A process for rapidly forming a ceramic shell mold on an expendable pattern (1) is disclosed. The process entails use of refractory slurries which include a large particle size colloidal silica sol binder. The colloidal silica sol binder has an average particle size of about 40 nanometers, i.e., about 3-4 times larger than colloidal silica sol binders heretofore employed in manufacture of ceramic shell molds. The use of the large particle sols yields unfired ceramic shell molds (20) which have about 40%to about 70%greater unfired strengths compared to ceramic shells made with prior art small particle size silica sols. Prime coats and refractory back-up coats which use the large particle size sol dry about 30%to about 40%faster than prime coats and back-up coats which employ the smaller particle size silica sols of the prior art.

Description

CAST IRON MOLD AND MANUFACTURING METHOD Field of the Invention The present invention relates to improved methods and compositions for coating casting technology.

Background of the Invention The smelting of coatings through the process of wax loss can be transferred to ancient Egypt and China. However, the process as practiced today, is a relatively new technology that dates back to the thirties and represents a business and science of rapid growth. Casting technology simplifies the production of complex metal shapes by melting the molten metal into expandable ceramic liner casings formed around disposable wax patterns which duplicate the desired shape of the metal. (Precision Investment Casting), for example, PIC is the term in the art that refers to this technology. The conventional PIC process employs the following six main steps: (1) Preparation of the pattern. A positive disposable pattern of the desired metal casting is made from thermoplastic material such as wax that will be melted, vaporized, or baked completely so as not to leave contaminating residues in the mold of the ceramic liner, from which it has been extracted. the wax. The positive pattern is prepared by injecting the thermoplastic material into a segmented die or "negative tool" and designed to produce patterns of the shape, dimension, and surface finish required for the melting of the metal. Simple or multiple patterns can be assembled by melting them into a "pour hole system" of disposable wax that feeds the molten metal to fill the liner mold; (2) Construction of the liner mold by: (a) Immersing the pattern assembly in a refractory paste containing fine particulate grains, in an aqueous solution of a stabilized alkaline colloidal silica linker, to define a coating of refractory material in the pattern; (b) Bringing the refractory lining in contact with a refractory coarse dry particulate grain "repellant" to define a repellant coating, and (c) Air drying to define a dry coating "insoluble fresh lining". These steps of the process can be repeated in order to build a mold of the lining (without baking) dried by air of the desired thickness, by successive layers. (3) "Extraction of the wax" The disposable wax pattern is removed from the mold of the air-dried "unbaked" liner, by applying steam autoclave, immersing the mold of the unbaked liner inside an instant extraction oven of wax heated to a temperature of 1000 ° F - 1900 ° F, or by any other method, which heats rapidly and melts the wax so that excessive pressure buildup does not break the mold liner. (4) "Baking" The liner mold from which the wax has been extracted is heated to a temperature of approximately 1600 ° F-2000 ° F to remove the volatile residues and form stable ceramic bonds in the liner mold. (5) "Casting" The mold of the heated casing is recovered from the furnace and placed to receive the melted metal. The metal can be melted by means of gas, indirect arc or induction heating. The melted metal can be melted in an air chamber or a vacuum chamber. The molten metal can be cast statically or centrifugally, and from a pouring spoon or directly from a casting crucible. The melted metal is cooled to produce a solidified metal melt in the mold. (6) "Recovery of the casting" The lining molds containing solidified metal castings are separated, and the metal castings are separated from the ceramic material of the lining. The foundries can be separated by means of a casting system, sawing it or cutting it with abrasive discs. The foundries can be cleaned by rubbing, overturning or grit blasting. The linkers used in refractory pastes affect the • 5 lining construction process and finally, the quality of the lining mold. The linkers must be chemically stable to ensure a long service of a refractory paste, used for repetitive dipping coatings. The linkers must also form insoluble bonds with the grains of refractory during drying with air, in order to allow the • new immersion of the pattern, as well as to allow the removal of the pattern during baking. The stabilized ceramic bonds produced in the liner by baking the mold, must also have an adequate baked resistance and a high melting point to withstand the melting of melted metal. The standard refractory paste linkers which have been used in the manufacture of ceramic liner molds, include hydrolysed ethyl silicates, and silicas colloidal sodium stabilized with small particle size having an average particle size of about 8 to 14 nanometers. The latter include alkaline aqueous dispersions of colloidal silica stabilized with sodium hydroxide, which are non-flammable and low in toxicity. The former is stabilized with added sulfuric or hydrochloric acid during hydrolysis to form the colloidal silica in situ. The former, however, employs flammable and toxic alcohol solutions to maintain solubility. However, the linkers based on ethyl silicate allow the • 5 faster drying and use lower levels of sodium oxide flow promoter. In the conventional process for the manufacture of ceramic lining molds, the required interval for drying between the layers can vary between thirty minutes for the main layers refractory, and eight hours or more, for the support layers • Depending on the complexity of the mold and the thickness of the lining wall. Generally, the finished liner molds are air dried for an additional twenty-four hours or more, to ensure adequate unbaked strength for the removal of the pattern. This dependence on air drying for the quality of the lining mold justifies a major pressure of production time, contributes to high production costs and has serious disadvantages. Due to these disadvantages, numerous efforts to shorten or eliminate the time interval required for drying between the layers, using chemical methods to quickly adjust the refractory filler linker. These chemical methods have extended the range of choice of candidate refractory binder linkers, beyond silicate of hydrolyzed ethyl and colloidal silica stabilized by sodium, to include ionic alkali metal silicates, and colloidal silica modified with stable alumina acid. These chemical methods of the prior art include: 1) The use of gaseous gelling agents to convert into • 5 gel a paste linker system. US Patent No. 2, 829, 060 teaches the use of carbon dioxide to gel an ammonia-modified sodium silicate paste linker system. W. Jones in a technical paper presented to the Investment 10 Casting Institute in October of 1979, described the use of dioxide • carbon or acid alumina solutions, to convert the linker pastes to alkali silicate. However, the pastes of the alkali silicate linker can cause undesirable flow at high temperatures. 15 US Patent No. 3,455,368 describes the use of ammonia gas to gel a linker system gßk hydrolyzed ethyl silicate or acidified colloidal silica. However, ammonia gas is toxic. U.S. Patent No. 3,369,775 describes the use of volatile organic gases to gel a hydrolysed ethyl paste linker system. Organic gases, however, present a ventilation problem that contributes to poor acceptance in smelting. 2) The use of two systems of linkers of paste to convert in gel to each other, when they are applied in the form of alternative layers. U.S. Patent No. 2,806,270 describes the use of: • 5 • Sodium silicate paste acidified by nitric acid, to gel an alkali sodium silicate paste; • A system of potassium silicate paste acidified by phosphoric acid to convert into gel any of: (a) A paste of alkaline potassium silicate, 10 (b) A paste of ethyl silicate modified by piperidine • alkaline and, (c) A system of ethyl silicate paste modified with alkaline monoethanolamine. 3) An acid ethyl silicate paste to gel any of: (a) A paste of alkaline potassium silicate, • (b) A paste of ethyl silicate modified by alkaline piperidine and, 20 (c) A system Ethyl silicate linker modified by alkaline monoethanolamine. U.S. Patent Nos. 3,751, 276 and 3,878,034 describe the use of a colloidal silica paste linker system modified by stable acid alumina, to convert into gel, either a stable ionic alkali silicate linker paste system or an alkali stable colloidal silica linker paste system. However, the use of these two interactive paste linking systems requires a change in the conventional coating manufacturing process. • 5 3) The use of a chemically treated repellent grain to gel a paste linker system. Dootz, Craig and Payton in the Journal Prosthetic Dentistry, volume 17, No. 5, p. 464-471 of May 1967 describes the use of stucco treated with monoammonium phosphate and magnesium oxide 10 to gel a solution of the paste system of the • sodium silicate paste linker. However, this method suffers the disadvantage that it degrades its effectiveness over time and can contaminate the refractory linker paste. 4) Use of a solution of a gelling agent to gel a paste-in-paste system. US Patent No. 3, 748, 157 describes the use of a solution of a basic aluminum salt conversion agent • for gel conversion. 1) A colloidal silica solder paste of stabilized sodium negative solution, and 2) An ionic alkali silicate paste system. Although these art methods have varying degrees in the usefulness in the preparation of ceramic lining molds for the Use in the PIC, however, requires multiple catalyst steps, or substantial time intervals between the successive coatings of the refractory paste materials. Therefore, there is a need for materials and methods, which quickly form the ceramic liner molds. • 5 Summary of the Invention The present invention relates to a process for rapidly forming a ceramic liner mold into a disposable support member, and to ceramic liner molds. obtained by it. The process of the present invention employs a colloidal silica solution with a large particle size having an average particle size of about 40 nanometers, a range of particle width from about 6 nm to about 190 nm, and one standard deviation of approximately 20 nm. The large particle size solution, which is employed, can preferably be achieved under the trademark • Megasol ™ marketed by Westbond Corp. Wilmington, DE. Megasol ™ has an average particle size of about 40 nanometers, a particle size range of about 6 nm to 190 nm, a standard deviation of the particle size about 20 nm and a sodium content of about 0.22% against sodium contents of about 0.4 to 0.6 % of the solutions of colloidal silica from the previous art.

The process of the present invention offers a number of advantages for the manufacture of ceramic liner molds over the prior art processes described above. For example, the use of the aqueous solution of colloidal silica Megasol ™ makes it possible to manufacture molds of ceramic liners without baking, which have unbaked resistances above about 40% up to 70%, compared with ceramic linings without baking, made with the prior art silica solutions which have much smaller particle size ranges. Another advantage of the present invention is that the refractory paste compositions employing Megasol ™ can accommodate a wide range of thermal expansions of the liner mold. A further advantage is that refractory pulp compositions employing Megasol ™ have a colloidal silica solids content of about 40% to 50% in the refractory slurry. These solids contents are much higher than the colloidal silica contents of approximately 22% to 27% achieved in the refractory pastes, which use small particle size silica solution linkers. The highest colloidal silica solids content in the refractory pastes used by Megasol ™ advantageously makes it possible to quickly dry both the refractory main layers and the refractory support layers.

The use of Megasol ™ in at least one of the pastes of the refractory main layer, and the refractory support layer pastes, preferably in both pastes, produces an increased stability of the pastes, as well as lining molds. • 5 ceramic with higher resistance. The present invention advantageously eliminates the common practice of the industry of using a polymer in refractory pastes, or using improved linkers with polymers in refractory pastes. The elimination of polymers, solves advantageously art problems prior to the manufacture of ceramic mold liners, the • which have low bake breaking modules, due to the porosity generated when the polymer is burned during baking. The elimination of the polymers also solves the problems of the previous art of the destabilization of the pastes refractory with the passage of time, as well as the problems of the quality control of refractory pastes. The main layers and the support layers, which use the Megasol ™ also dry in a faster time in approximately 30% to 40%, than the main layers and The support employs the small particle size colloidal silica solutions of the prior art. This makes possible, shorter drying times which reduce the cost of manufacturing the molds.

Brief Description of the Drawings Figure 1 illustrates a disposable positive standard 1 of a desired metal casting. Figure 2 is an isometric view of a liner 10 without baking before the removal of the pattern 1. • 5 Figure 3 is a cutaway view of a ceramic liner without dry baking, from which the wax has been extracted.

Detailed Description of Invention Refractory Grains 10 A wide variety of refractory grains can be used • with Megasol ™, both in the refractory main coating pastes and in the refractory support layer pastes. Examples of these refractory grains include, but are not limited to, mullite, calcined porcelain clay, and others. silicates of alumina, vitreous and crystalline silica, alumina, zircon and chromite. Preferably, the refractory grains are free of ionic contaminants in amounts that may contribute to the • Instability of refractory grains, and thermally induced phase changes, which may occur during the metal casting. As is known in the art, refractory grains which are free of contaminants in amounts that may contribute to the instability of the refractory grains, can be produced by purification with or without calcination. 25 Preparation of Refractory Pasta. The refractory main layer pastes and the refractory support layer pastes use large particle size silica solders, such as Megasol ™, with • 5 a refractory grain in sufficient quantities to have a desired viscosity to be used in the mold immersion process. Preferably, Megasol ™ having a specific surface area of about 68m2 / gm of an average particle size of about 40 nanometers is used, a particle range of about 6 nm to about 190 nm, a standard deviation of the particle size of about 20 nm, and a sodium content of about 0.22%. The average particle size of the Megasol ™ is calculated, dividing the number 2727 between the area of specific surface. The amounts of Megasol ™ and refractory grain in the refractory paste compositions can be varied over a wide range. • The linker of the Megasol ™ silica solution has a much larger particle size range, and an area of surface area lower than the colloidal silica solution linkers of the prior art. The Megasol ™ silica solution linker can be used at a pH of about 8.0 to about 10.0, preferably at a pH of about 9.0 to about 9.5, the linker of silica solution Megasol ™ can be used in titrable NA20 contents of from about 0.02% to about 0.35%, preferably from about 0.1% to about 0.25%. More preferably, the silica solution linker Megasol ™ is used in a content of NA20 titrable from about 0.20% to about 0.22%. The Megasol ™ silica solution linkers for use in the present invention can have varying solids contents. For example, Megasol ™ can be used in a solids content from about 30% up • about 50%, preferably from about 40% to about 75%, and more preferably, the Megasol ™ is used at solids contents of about 45% in at least one of the pulps of the refractory main layer, and more preferably, in both pastes of the refractory support layers. The main coating refractory pastes and the • refractory support pastes, are prepared by placing the Megasol ™ silica solution linker in a tank of mixed clean sprayed with water, and adding the refractory material while mixing. In the mixing tank, various mixing apparatuses known in the art can be used. These apparatuses include, for example, blade type mixers, hammer mills, high speed dispersion mixers, and fixed turntable blade mixers. The refractory material is added while the mixture is carried out until the desired viscosity is reached. For the • 5 refractory pastes of the main layer, this viscosity is approximately 18 to 30 seconds No.4 Zahn, preferably 20 to 30 seconds, and more preferably 24 to 30 seconds. The appropriate viscosity for the refractory support coating pastes, in which the Megasol ™ is used, and the refractory grains of fused silica, are approximately 10 a • 18 seconds, Zahn viscosity No. 4, preferably approximately 10 to 16 seconds, Zahn No. 4, more preferably, approximately 12 to 15 seconds Zahn No.4. After the additional mixture to remove the air trapped, and to achieve equilibrium, a final viscosity adjustment is made by adding additional Megasol ™ colloidal silica solution linker or refractory material. It also can • Add a non-ionic surfactant or anionic surfactant to the refractory pastes. 20 Construction of the Lining Mold The construction of the lining mold begins with the application to a clean disposable pattern of one of three coatings of a refractory main coat paste that includes refractory grains and Megasol ™, preferably to a wax pattern. The wax pattern is preferably formed from any wax-grade coating melt based on paraffin or full or non-full microcrystalline wax. The wax pattern is submerged inside the layer dough • 5 main refractory, to cover the surface of the pattern with a continuous layer of a refractory paste of the main layer, is drained completely to remove the excess paste, then it is reframed with refractory stucco of the main layer. The resulting main layer may have a thickness of approximately 0.02"to 0.2", preferably 0.04"to 0.2", more • preferably 0.04"to 0.1". Different paste compositions can be used in the refractory pastes of the main layer, and the pastes of the support layers. Refractory pastes specific to the main layer and refractory pastes specific of the support layer, are determined by the desired characteristics of the lining mold ceramic to produce a metal casting having the dimensions • desired and the surface finish provided by the disposable pattern. 20 The refractory paste of the main layer employs finer refractory grain sizes, generally from about -200 and finer, descending to approximately maya -325. The refractory pastes of the main layer can be used and include Megasol ™, together with a mixture of melted silica from maya -200 and fluorine and fine powder from zircon from maya -325. The fine zircon powder provides a high resistance to the melted metal. The fine particle size of the zircon powder also makes it possible to produce foundries which have detailed and smooth surface finishes. Each main layer is repelled, with a coarse refractory grain generally of maya zircon sand from about -20 to about -200, preferably maya from -70 to -140. In the refractory pastes of the main layer in which Megasol ™, silica and melted zircon are used, the melted silica, should preferably have a particle size of maya from • about -120 to about -200, and zircon should have more preferably, a maya particle size -325. The sizes of the melted silica of approximately maya - 100, approximately -120, approximately maya -140, approximately maya -170, approximately maya -270 to approximately 325. The zircon particle sizes may be, for example, approximately maya -200, • approximately maya -325 and approximately maya -400. Preferably the zircon is approximately maya -200.

Non-ionic surfactants can also be added optionally to the refractory paste of the main layer. A particularly useful nonionic surfactant, which can be employed PS9400 marketed by Buntrock Industries, Williamsburg, VA. This surfactant can be added to the refractory layer paste in an amount of up to 0.02%, based on the weight of the Megasol ™ linker. This surfactant improves the ability of the refractory paste in the main layer to wet the wax pattern and also aids in drainage. The refractory paste of the support layers is applied to the main layers • 5 riveted, to produce support layers. The refractory support pastes use refractory grain sizes thicker than those used in the refractory pastes of the main layer. In refractory support pastes where melted silica has been used with Megasol ™, the melted silica can have a particle size from about maya • -80 to approximately maya -270, preferably from maya -100 to approximately maya-200. More preferably, the melted silica is approximately maya -100 to approximately maya -120. Each layer of support, is resurfaced with a thicker refractory grain to build the thickness in the mold for increased strength. The refractory grains that can be used as stucco in the • support layers, can vary from approximately maya -10 to approximately maya 50, preferably from about maya -20 to about 50 maya. More preferably, these refractory grains have a size of about -30 to about 50 maya. The support layers are applied over the main stripped layers until the lining reaches the thickness and desired resistance. The number of support layers applied depends on the size and weight of the metal casting to be formed in the ceramic mold. A ceramic mold thickness of approximately 0.20"to 0.5" is sufficient for most foundries. Generally, two main layers and four to five support layers produce an unbaked mold with a thickness of 0.25"that has a sufficient strength to resist wax extraction and baking In an alternative mode a peeling material can be applied transitional refractory, preferably zircon or aluminum silicate, which has an intermediate grain size between the fine-grained resurfacing of the main layer, and the coarse-grained repellent of the support layer, to the pattern of the expanded expandable core layer , before the application of the coating of the refractory paste of the support layer, the layering of the transition layer can be used to add resistance to the mold without baking, and to minimize the possibility of misalignment between the final coating of the paste of the main layer, and the first coating of the paste of the refractory support layer.The unbaked mold is dried to a temper from about 60 ° F to about 90 ° F, preferably from about 70 ° F to about 75 ° F. The drying can be done under accelerated conditions of low humidity and high temperature with rapid movement of air.

The drying time between the main layers and the successive support layers depends on the complexity of the shape of the expandable pattern. Expansible patterns that have deep cavities where the air flow is minimal, take a while • 5 longer to dry between the layers. Simple patterns, which have flat sides, dry faster. The main layers and the support layers formed from refractory pastes employing Megasol ™ dry in about 30% to 40% faster than the industry-standard refractory pastes 10 which use • colloidal silica solution binders of smaller particle size, and which contain higher amounts of water.

Extraction of Wax. Unbaked ceramic liner molds can be subjected to wax extraction by immersion in water • boiling, subjected to steam autoclave and rapid extraction as it is known in the art. The steam autoclave can be made by: 1. The use of a vapor pressure as high as possible, preferably about 60 psi or greater, and more preferably about 80 to 90 psi. 2. Carry out the closing and pressurization of the autoclave, as quickly as possible, preferably in less than approximately 15 to 20 seconds. 3. Expose the mold without baking steam-dried air • 5 for a period of approximately 15 to 20 minutes. 4. Slow depressurization of the autoclave for a time of approximately 30 to 60 seconds. The extraction of instant wax can be done by immersing the mold of the liner without baking drying by air inside an oven heated to a temperature from about • 1000 ° F to approximately 1900 ° F. At these temperatures the wax that is glued next to the wall of the ceramic mold melts quickly due to the expansion of the wax, does not break the ceramic mold. The ceramic mold can be removed then to a cooler temperature zone of about 200 ° F to 600 ° F to finish the removal of the wax. The melted wax can be drained through an opening in the bottom • inside the fusion chamber, inside the water bath or a container for recovery. 20 Baking Baking involves heating the mold of the ceramic liner, from which the wax has been extracted, produced at a temperature above about 1600 ° F to approximately 2000 ° F to remove the volatile residues and to produce the mold of the high strength ceramic liner, by forming stable ceramic bonds through sintering. The molds of the ceramic lining, from which the wax has been extracted, are kept in the oven to achieve the • 5 thermal equilibrium, after which, they are removed from the furnace, and the melting with the desired melted metal. The present invention is described further with reference to the following non-limiting examples.

Example 1: A wax bar pattern one of 8"by 7/8" by 3/8"as illustrated in Figure 1, is immersed within a refractory paste of the composition shown in Table 1 For reasons of convenience, the same refractory paste is used for both layers, the main one and the support one.

Table 1 • MATERIAL AMOUNT Megasol ™ 1000gr 20 Tecosil 120F2 1500gr Zircon 3253 400gr Surfactant PS 94004 2ml 1 . Colloidal silica linker from Megasol ™ with a 50% solids content marketed by Wesbond Corp. 2. Melted silica from C-E minerals, particle size from 44 to 177μm 3. Calcined Florida zircon, maya particle size -325 marketed by Continental Minerals. • 5 4. Non-ionic surfactant marketed by Buntrock Industries, Williamsburg, VA, PS 9400 is a polyoxyethylated decyl alcohol, having a specific gravity of about 1.0.

The wax pattern 1, is submerged inside the paste ^ refractory for 5 seconds, then it will be removed and allowed to drain for 10 seconds to form a first main layer. To the first main layer, a sand zircon-maya -70 to maya 140 marketed by DuPont Corp. The main coat bar pattern sandwiched with zircon sand is dried for one hour, and then re-immersed in the refractory paste F for 5 seconds to form a second main layer and it is again reframed with zirconium sand from maya -70 to 140. The wax pattern 1, which has two main layers peeled off, is subsequently submerged within the refractory mixture for 5 seconds and drained for 10 seconds to produce a first support layer. The first layer of The refractory support is then stripped with fused silica Tecosil de maya -30 to Mayan 50 marketed by C-E Minerals. The peeled backing layer is then dried for one hour. This procedure is repeated to produce a total of 5 layers of support stripped with melted silica Tecosil de maya -30 a • 5 Mayan 50. After the application of each main layer and each support refractory layer, the vertical sides 5 of the pattern are discarded to remove the layers and the repellent. The resulting unbaked ceramic mold 10 formed in pattern one having two main layers of coating, and peeled with zircon sand and 5 layers of support where the peel is from • Melted silica Tecosil de maya -30 a maya -50 marketed by C-E Minerals Co. As illustrated in Figure. 2, it is immersed in the refractory paste again to produce a sealed coating. The ceramic mold with coating sealing is dried at a temperature of 75 ° F overnight. The ceramic mold without dry baking is immersed in boiling water to remove the pattern 1. The ceramic mold without • Dry baking to which the resulting wax has been extracted 20, is illustrated in the Figure. 3, is cut in half so longitudinal and dried overnight. The strength of a section of the unbaked ceramic mold measuring 1"wide by 6" long by 0.3"thick is evaluated by loading a 2" section of the section to the bending failure.

This modulus of rupture ("MOR") of the unbaked ceramic mold is calculated using the formula: R = (3WI) / (2bd2) Where: R = a modulus of rupture lbs / in2 W = a load in pounds in which sample 1 = distance (section) in inches between the center lines of the lower support ends, b = sample width in inches d = depth of the sample in inches The rupture modulus is shown in table two. A section of the unbaked ceramic mold measuring 1"by 6" by 0.3"in thickness is baked at a temperature of 1800 ° F for one hour.The baked section is then evaluated to determine its strength by loading a length of 2"from the section to the flexure failure, as described above. The breaking module ("MOR") of the baked ceramic mold is calculated using the formula above. The results are illustrated in table 2.

Example 2 The procedure of Example 1 is followed except that the Megasol ™ is diluted with water to produce a 45% colloidal silica solids content. The MOR is measured as in Example 1.

Example 3 • 5 The procedure of Example 1 was followed except that the Megasol ™ is diluted with water to produce a colloidal silica solids content of 40%. The MOR was measured following the procedure of Exemplol.

Example 4 • The procedure of Example 1 was followed except that the Megasol ™ is diluted with water to produce a solids colloidal silica content of 35%. The MOR was measured following the procedure of Example 1. Example 5 The procedure of Example 1 was followed except that • replaced the M47-22S Mulgrain having a particle size of maya -20 to maya +50 by the fused silica Tecosil de maya -30 to 20 maya +50. The Mulgrain M47-22S is marketed by C-E Minerals Co. The MOR is measured following the procedure of Example 1 .

Example 6 The procedure of Example 5 was followed except that the Megasol ™ is diluted with water to produce a solids content of colloidal silica of 45%: the MOR is measured following the procedure of Example 1. • Example 7 The procedure of Example 5 was followed except that the Megasol ™ is diluted with water to produce a colloidal silica solids content of 40%. The MOR is measured following the procedure of example 1. • Comparative examples from 8 to 12 Example 8 The procedure of example 1 was followed except that the NYACOL 830 colloidal silica solution having an average particle size of 8 nanometers, and the solids content of the colloidal silica 30% is replaced by the colloidal silica solution Megasol ™ having a solids content of 50%. The NYACOL 830 is marketed by EKA Chemicals Co. The MOR is measured following the procedure of example 1.

Example 9 The procedure of Example 8 was followed except that the NYACOL 830 is diluted with water to produce a solids content of colloidal silica of 24%. The MOR is measured following the procedure of Example 1.

Example 10 • 5 The procedure of example 8 is followed except that the Mulgrain M47-22S of maya size -20 to +50 is replaced by melted silica Tecosil de maya-30 to maya +50. The MOR is measured following the procedure of Example 1.

Example 1 1 • The procedure of Example 10 is followed except that the NYACOL 830 is diluted with water to produce a solids content of colloidal silica of 27%. The MOR is measured following the procedure of Example 1. Example 12 The procedure of Example 10 is followed except that the NYACOL 830 is diluted with water to produce a solids content of colloidal silica of 24%. The MOR is measured following the procedure of Example 1. In order to illustrate the reduced drying times that can be achieved with the use of Megasol ™, the total drying times were compared for the 5 support layers applied in examples 1 and 8. The drying times are measured using a thermocouple attached to the samples. A Pocket Logger model XR340 from Pace Scientific records the time against the temperature, each layer is considered dry, when its temperature is two degrees from the ambient temperature. The ambient temperature is 70 ° F + 5 ° F, and the relative humidity is about 30% + 5%. The results are illustrated in Table 2. As illustrated in Table 2, the support layers formed from the refractory support mixtures which utilize the Megasol ™ at 50% solids contents, are dried at about 67% of the time required to dry the 5 layers of support formed from refractory mixtures of the support layer, which use the NYACOL 830.

Table 2 • • fifteen • twenty 1 Baking rupture module is obtained after baking the mold at a temperature of 1800 ° F. * The total drying time of the 5 support layers is 141 minutes.

** The total drying time for the 5 layers of support is 236 minutes Comparative examples from 13 to 18 These examples illustrate the increased strengths of the ceramic mold linings, due to the use of refractory pastes which Megasol ™ uses on ceramic molds made from refractory pastes, which use silica solutions that have average particle sizes from 14 nanometers to 20 nanometers. The results are shown in table 3.

Example 13 The procedure of Example 1 is followed, except that the Ludox® Hs 40 colloidal silica solution having average particle size of 14 nanometers, and a solids content of colloidal silica of 35% is replaced by the Megasol ™ having a solids content of 50%. The Ludox® HS 40 is marketed by E.l. DuPont de Nemours, Inc., the unbaked and baked MOR are measured following the procedure of Example 1.

Example 14 The procedure of Example 13 is followed except that the Ludox® HS 40 colloidal silica solution has a colloidal silica content of 40%. The unbaked and baked MORs are measured following the procedure of Example 1.

Example 15 The procedure of Example 1 is followed, except that the Ludox®TM colloidal silica solution having an average particle size of 20 nanometers, a solids content of 75% colloidal silica is replaced by the Megasol ™ having a solids content of 50%. The Ludox® Hr40 E. l. DuPont de Nemours, Inc. The unbaked and baked MORs are measured following the procedure of Example 1.

Example 16 • The procedure of Example 14 is followed, except that the Ludox® TM colloidal silica solution has a colloidal silica solids content of 40%. The unbaked and baked MORs are measured following the procedure of Example 1.

Example 17 The procedure of Example 1 is followed, except that the • Colloidal silica solution Megasol ™ has a solids content of 35%. The unbaked and baked MORs are measured following the procedure of example 1.

Example 18 The exemplum procedure is followed, except that the colloidal silica solution Megasol ™ has a solids content of 40%. The unbaked and baked MOR is measured following the procedure of Example 1.

• In a further embodiment the present invention, as illustrated by the non-limiting examples which are 19 and 20, the potassium silicate is mixed with Megasol ™. The mixture of potassium silicate and Megasol ™ is present in, at least one of the layer main and the support layer. Preferably, the mixture of potassium silicate and Megasol ™ is present in the composition of both the main layer and the • in the composition of the support layer. In each of the main layer and support takes the potassium silicate can be present in an amount of up to 50% by weight of Megasol ™. Preferably, potassium silicate is present in about 6 to 8% by weight of Megasol ™, more preferably in about 6%.

Example 19 The procedure of Example 1 is followed, except that the refractory paste used, both for the main layer and for the support layer, has the composition illustrated in Table 4. • 5 Megasol ™ used in Table 4 has a solids content of 40%. Table 4 MATERIAL AMOUNT Megasol ™ 1 700gr 10 Silica of maya 4002 1375gr • Surfactant PS 9400 3 2ml Silicate of potassium4 16.8gr 1 The linker of the colloidal silica solution Megasol ™ 15 having a solids content of 40%, is marketed by Webond Corp. 2 Melted silica • 3 Surfactant marketed by Buntrock Industries, Williamsburg, VA 20 4 Kasil potassium silicate sold by PQ Corporation, weight ratio of SiO2 / K20 is 2.5, 8.3% K2O, 20.8% Si02 and 29.1% solids. The unbaked and baked MORs are measured following the procedure in Example 1. The unbaked MORs is 913 psi.

The baked MOR is 1424 psi.

Example 20 The procedure of example 19 is followed, except that the layers • main and support have the composition shown in Table 5. TABLE 5 MATERIAL AMOUNT Megasol ™ 1 700gr 10 Mayan silica 1402 1375gr • Surfactant PS 94003 2ml Potassium silicate44 22.4gr 1 The linker of colloidal silica solution Megasol ™ that has 40% solid content, marketed by Wesbond Corp. 2 Melted silica 3 Surfactant marketed by Buntrock Industries, Williamsburg, VA. 4 Kasil potassium silicate sold by PQ Corporation, weight ratio of SiO2 / K2O is 2.5, 8.3% K2O, 20.8% SiO2 and 29.1% solids.

The unbaked and baked MOR is measured following the procedure of Example 1. MOR without baking is 912 psi. The baked MOR is 1362 psi.

Still in a further embodiment of the present invention as illustrated in non-limiting examples from 21 to 24, a colloidal silica solution of commercial particle size is mixed with Megasol ™. The mixture of the silica solution • 5 colloidal and Megasol ™ is present in, at least one of the main layer and the support layers. Preferably, the mixture of colloidal silica solution and Megasol ™ is present in the composition of both main layers and the composition of the support layer. In each of the main layers and the support layer, the commercial small colloidal silica solution may be present in the mixture in amounts of about 18% to about 85% by weight of the Megasol ™. A particularly useful commercial colloidal silica solution of the size of small particle which can be mixed with Megasol ™, as described above is the NYACOL 830 having an average particle size of 8. • nanometers, and silica solids of 24%, marketed by EKA Chemicals Co. Other silica solutions of small particle size can be mixed with the Megasol ™, according to this embodiment, they can have an average particle size of about 12. nanometers, 14 nanometers, 20 nanometers and 22 nanometers.

Example 21 The procedure of Example 1 is followed except that the refractory paste used for both coatings of both support layers has the composition illustrated in Table 6. The Megasol ™ is employed in Table 6 and has a content of • 50% solids. Table 6 MATERIAL AMOUNT Megasol ™ 1 100gr Tecosil 120F 1 190gr 10 Zircon 325 3 330gr • Surfactant PS 9400 4 2ml NYACOL 830 5 562gr The linker of colloidal silica solution Megasol ™ that has a 50% solid content, marketed by Wesbond Corp. 2. Melted silica 3. Calcined Florida zircon, maya particle size -325 marketed by Continental Minerals. 20 4. Surfactant marketed by Buntrock Industries, Williamsburg, VA. NYACOL 830 @ 24% silica solids marketed by EKA Chemicals Co.

The unbaked and baked MOR is measured following the procedure of Example 1. MOR without baking is 740 psi. The baked MOR is 1618 psi.

• Example 22 The procedure of Example 21 is followed, except that the Megasol ™ is present in an amount of 172g, and the NYACOL 830 is present in an amount of 490gr. The unbaked and baked MOR is measured according to the procedure of Example 1. MOR without baking is 870 psi. The MOR is 1493 psi.

Example 23 The procedure of Example 21 is followed, except that Megasol ™ is present in an amount of 542 g and Nyacol 830 is present in an amount of 120 g. The MOR without baking and baking is measured following the • procedure of Example 1. The unbaked MOR is 858 psi. The baked MOR is 1668 20 psi. In yet another embodiment of the present invention, as illustrated in Examples 24 through 26, a colloidal linker employing potassium silicate, a commercial colloidal silica solution of small particle size, and Megasol ™ is used. in, at least one of the main and support layers.

Preferably, the colloidal linker is present in both the main layer and the support layer. On each of the main layer and the support layer, the potassium silicate, the small particle size colloidal silica solution and the Megasol ™, • 5 may be present in the colloidal linker in varying amounts. The Megasol ™ in the colloidal linker may be present in the present embodiment in an amount from about 10% to about 87% by weight of the colloidal linker; Potassium silicate can be present in an amount of about 3% to about 8% by weight of colloidal linker; and the colloidal solution of small particle size, can be present in the colloidal linker in an amount of about 5% up to 87% by weight of the linker colloidal. In this embodiment, the potassium silicate is preferably Kasil potassium silicate, marketed by PQ Corporation. The potassium silicate Kasil has a proportion of • weight of Si02 / K20 of 2.5, 8.3% K20, 20.8% Si02 and 29.1% solids. In this modality, also the colloidal solution of size of preferred small particle, is the NYACOL 830 having an average particle size of 8 nanometers, and silica solids of 24%, marketed by EKA Chemicals Co.

Example 24 The procedure of Example 1 is followed, except that the refractory paste used for both the main layer and the support layer has the composition shown in Table 7. f 5 Table 7 CANTI DAD MATERIAL Colloidal linker1 1000gr Tecosil 120F2 1500gr Zircon3253 400gr 10 Surfactant PS 94004 2ml f 1 Megasol ™ blend having 50% solids content marketed by Wesbond Corp., Kasil potassium silicate and NYACOL 830 where the Megasol ™ is present in an amount of 87% by weight of the colloidal linker, the Kasil is present in an amount of about 8% by weight of the colloidal linker, and NYACOL 830 is present in an amount of about 5% by weight of the colloidal f-linker. 2- Fused colloidal silica marketed by C-E Minerals, size particle size from 44 to 177μm 3 Calcined Florida Zircon, maya particle size of -325 marketed by Continental Minerals. 4 Surfactant marketed by Buntrock Industries, Williamsburg, VA 25 Example 25 The procedure of Example 24 is followed, except that the colloid linker in Megasol ™ is present in an amount of 10% by weight of the colloidal linker, the Kasil is present in • an amount of about 3% by weight of the colloidal linker and the NYACOL 830 is present in an amount of about 87% by weight of the colloidal linker.

Example 26 10 The procedure of Example 24 is followed, except that the • colloidal linker Megasol ™ is present in an amount of 57% by weight of the colloidal linker, Kasil is present in an amount of about 5% by weight of the colloidal linker and the NYACOL 830 is present in an amount of about 38% by weight of the colloidal linker. •

Claims (20)

1. R E I V I N D I C A C I O N E S Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: • 5 1. A method of manufacturing a ceramic liner mold, which comprises: applying a layer of a main layer paste comprising refractory material and a colloidal silica solution 10 on an expandable pattern of thermoplastic material, for • producing a main coating preform, drying said main coating preform, applying at least one layer of a support coating refractory paste comprising material 15 refractory and a colloidal silica solution on said main coating preform to produce a support refractory lining preform, the drying of said support refractory lining preform, the removal of said thermoplastic pattern from said refractory lining preform to produce a lining mold without baking, and heating said lining mold without baking at a temperature sufficient to produce a lining mold of 25 ceramic. Wherein at least one of said main coating paste, or said support refractory coating paste, wherein said solution is an aqueous solution of colloidal silica having an average particle size of approximately 40 nanometers. • The method as described in claim 1 further characterized in that it additionally comprises a peel material of at least one of said main coating preform or refractory lining preform of 10 support before drying said coating preform • main or refractory support lining preform. 3. The method as described in Claim 2 further characterized in that said colloidal silica solution 15 has a range of particle size from about 6 nm to about 190 nm. 4. The method as described in Claim 3 further characterized in that said colloidal silica solution, 20 has a standard deviation of particles of approximately 20nm. 5. The method as described in Claim 3, further characterized in that said solution has a sodium content of about 0.02% and up to about 0.35%. 6. The method as described in Claim 2, • 5 further characterized in that said silica solution has a solids content of from about 30% to about 50%. 7. The method as described in Claim 6, 10 further characterized in that said silica solution has a • Solids content of approximately 40%. 8. The method as described in Claim 2, further characterized in that said main layer paste 15 comprises a refractory grain selected from the group consisting of silica and melted zircon, said refractory grain having a particle size of about maya -200 to about maya-350. 9. The method as described in Claim 8, further characterized in that said support refractory layer slurry comprising melted silica having a particle size of approximately about -80 to about maya of -270. 25 . 10. The product of the process as described in Claim 2. eleven . A method of manufacturing a ceramic lining mold • which comprises: the application of a coating of a main layer paste comprising refractory material and colloid linker comprising solution of silica and potassium silicate on an expandable pattern of thermoplastic material to produce a 10 main coating preform. The drying of said main coating preform, the application of at least one layer of the paste of the refractory support layer comprising refractory material, colloidal silica solution on said coating preform 15 to produce a support refractory lining preform, the drying of said refractory lining preform of • support, the removal of said thermoplastic pattern from said preform 20 of refractory support liner to produce a lining mold without baking and heating said liner mold to a temperature sufficient to produce a ceramic liner mold, wherein at least one of said main lining paste or said refractory support paste, said colloidal silica solution employing said colloidal silica linker is an aqueous solution of colloidal silica having an average particle size of about 40 nanometers. • 12. The method as described in Claim 1 1, further characterized in that it additionally comprises applying the polishing material to at least one of said main coating preform or coating preform. 10 refractory support before drying said preform of • main lining or refractory support lining preform. 13. The method as described in Claim 12 further characterized in that the potassium silicate is present in an amount of up to about 50% by weight of the colloidal silica solution having an average particle size of about 40 nanometers. . 14. The method as described in the Claim 15 further characterized in that the potassium silicate is present in an amount of about 6 to 8% by weight of the colloidal silica solution having an average particle size of about 40 nanometers. 25 15. The method as described in Claim 14, further characterized in that the potassium silicate is present in an amount of about 6% by weight of the colloidal silica linker having an average particle size of • 5 approximately 40 nanometers. 16. The product of the process as described in Claim 12. 10 17. A method for manufacturing liner molds • ceramic which comprises: the application of a coating of a main layer paste comprising refractory material and a colloidal linker on an expandable pattern of thermoplastic material to produce a main coating preform; the drying of said main coating preform, the application of at least one layer of a paste of a refractory support coating comprising refractory material and a colloidal silica solution on said main coating preform 20, to produce a coating preform support refractory, the drying of said support refractory lining preform, the removal of said thermoplastic pattern from said support refractory lining preform to produce an unbaked lining mold, and the heating of said lining mold without baking to a lining mold. • 5 sufficient temperature to produce a ceramic mold liner, wherein at least one of said main coating paste or refractory support paste and said colloidal linker is a mixture of colloidal silica aqueous solution having a particle size. average of approximately 40 nanometers, • an aqueous solution of colloidal silica having an average particle size of approximately 8 nanometers and potassium silicate. 18. The method as described in Claim 17, further characterized in that it additionally comprises the application of a plaster material to at least one of said main cladding preform or refractory backing preform, prior to the drying of said cladding material. preform of 20 main lining or support refractory lining preform. 19. The method as described in Claim 18, further characterized in that said colloidal linker said The colloidal silica solution having an average particle size of about 40 nanometers is present in an amount of from about 10% to about 87% by weight of the colloidal linker, the potassium silicate is present in an amount of • about 3% to about 8% by weight of colloidal linker, and the colloidal solution of small particle size having an average particle size of about 8 nanometers is present in the colloidal linker in an amount of about 5%. % up to about 10% by weight of the colloidal linker. • 20. The product of the process as described in Claim 18 R E S U M E N A method is described for rapidly forming a ceramic shell mold in a disposable pattern (1). The process includes the use of refractory pastes, which include a • 5 large particle size colloidal silica linker. The colloidal silica solution linker has an average particle size of about 40 nanometers, for example, about 3 to 4 times greater than the colloidal silica solution linkers used so far 10 in the application of ceramic outer shell. The use of • Large particle solutions, produces unbaked ceramic outer shell molds (20) which have unbaked resistances greater than about 40% to about 70%, compared to the outer shells of 15 ceramics made with small particle size silica solutions from the prior art. The main and refractory support layers that use the particle solutions of # large size, they dry approximately 30 to 40% faster than the main and support layers that employ solutions of 20 silica particles of smaller size than the previous art.