WO1980001146A1 - Method of making and using a ceramic shell mold - Google Patents
Method of making and using a ceramic shell mold Download PDFInfo
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- WO1980001146A1 WO1980001146A1 PCT/US1978/000187 US7800187W WO8001146A1 WO 1980001146 A1 WO1980001146 A1 WO 1980001146A1 US 7800187 W US7800187 W US 7800187W WO 8001146 A1 WO8001146 A1 WO 8001146A1
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- mold
- graphite
- barrier coating
- hardened
- applying
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
- B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
- B22C1/165—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents in the manufacture of multilayered shell moulds
Definitions
- This invention relates to the preparation of a ceramic shell mold useful for investment casting purposes, and particularly to a method of making a shell mold that will effectively reduce the amount of surface decarburization of a ferrous article formed in the shell mold.
- Investment casting also referred to as the "lost wax" process, typically involves alternate applications of a ceramic coating composition and a stucco composition to an expendable pattern in order to provide a multi-layered shell mold.
- the pattern is usually made of wax, plastic, or similar material which is melted out to leave a correspondingly shaped internal cavity into which molten metal is poured.
- Unfortunately there have been many attempts to control the surface finish and the amount of decarburization of steel investment castings.
- the problem of a metal-mold-atmosphere reaction at the time of pouring and initial stages of solidification of the molten metal has continued to cause an undesirable carbon-free zone adjacent the surface of the article as well as surface blemishes.
- the present invention is directed to overcoming one or more of the problems as set forth above.
- a ceramic shell mold is made by alternately applying coating compositions and stucco compositions to an expendable pattern forming a resultant multi-layered mold substantially free of graphite, and applying a barrier coating to the exterior surface of the multi-layered mold, with the barrier coating including a mixture of a ceramic powder, a binder, and a preselected amount of graphite.
- the amount of graphite in the barrier coating is limited to a range of about 4 to 20 Wt.% of the solid portion.
- the shell mold is preferably made by heating the multi-layered mold and forming a resultant hardened mold before the barrier coating is applied.
- the abovedescribed multi-layered mold and barrier coating are heated and a ferrous molten metal poured into the cavity, whereupon after cooling and removal of the article from the mold the article will be noted to have minimal surface carbon depletion and a relatively smooth surface.
- the sole figure is a diagrammatic and enlarged, fragmentary cross sectional view through a multi-layered shell mold having a barrier coating thereon in accordance with the present invention.
- a preferred method of making a ceramic shell mold 6 comprises the steps of alternately applying a ceramic coating composition 8 and a stucco composition 10 to an expendable or thermally meltable pattern a preselected number of times, firing such multi-layered mold to remove the pattern and provide a hardened mold 12 having an internal casting cavity 14, and applying a barrier coating 16 including a ceramic power, a binder and a preselected amount of graphite as is generally illustrated in the drawing.
- the presence of any significant amount of graphite is preferably avoided in the multi-layered mold, particularly adjacent the casting cavity 14, and is preferably controlled to a range of about 13 to 17 Wt.% graphite of the total amount of the solid portion of the barrier coating 16.
- the aforementioned ceramic coating composition 8 basically includes a ceramic powder and a binder.
- the ceramic powder is selected from the group consisting essentially of fused silica, vitreous silica, crystalline silica, alumina silicate, alumina, magnesium silicate, zircon, zirconium silicate, and clay treated to remove impurities, and can be mixtures thereof.
- the binder is selected from the group consisting essentially of colloidal silica sol, ethyl silicate, aluminum phosphate, and aqueous alkali metal silicate.
- the stucco composition 10 basically includes conventional granular refractory materials such as zircon.
- the multi-layered mold made by alternately applying the ceramic coating composition 8 and the stucco composition 10 a preselected number of times to the pattern is desirably substantially free of graphite.
- this term it is meant that less than 0.5 Wt.% graphite is present in the multi-layered mold before the barrier coating 16 is applied.
- a preferred method of making the ceramic shell mold 6 includes the following steps:
- Step (a) Forming an expendable or meltable pattern of wax, plastic or similar material of a construction having the desired shape
- Step (b) Applying a prime or first ceramic coating composition 8 including fused silica flour, finely divided zircon, a limited amount of nitrile polymer latex for low temperature strength, for example 2 Wt.%, and colloidal silica sol including water in the form of a slurry to the pattern by dipping the pattern into an agitated thixotropic slurry thereof, removing the coated pattern therefrom and allowing a preselected amount of draining and initial stages of setting thereof;
- a prime or first ceramic coating composition 8 including fused silica flour, finely divided zircon, a limited amount of nitrile polymer latex for low temperature strength, for example 2 Wt.%, and colloidal silica sol including water in the form of a slurry to the pattern by dipping the pattern into an agitated thixotropic slurry thereof, removing the coated pattern therefrom and allowing a preselected amount of draining and initial stages of setting thereof;
- Step (c) Applying a coarser or stucco coating composition 10 including granular refractory material such as zircon to the still wet first coating composition 8 by sprinkling same thereon from a conventional rainfall sander, or alternately by immersing it in a conventional fluidized bed, and with the AFS grain size of the stucco coating composition being generally limited to a range of from about 35 mesh to 20 mesh (about 0.5mm to 0.8mm);
- Step (d) Drying the coated and stuccoed pattern for a preselected time period, for example 30 minutes to 6 hours, to a waterproof or gelled shape and providing a first layer 18; Step (e) Alternately repeating Steps (b),
- Step (f) Heating the multi-layered "green” mold in an autoclave at a preselected first temperature of about 180 to 200° C (350 to 400° F) for about 5 to 25 minutes, melting out and removing the pattern, and providing some strength to the mold;
- Step (g) Firing the multi-layered mold in a furnace at a preselected second temperature of about 800 to 1400° C (1500 to 2500° F), and preferably about 1000° C (1800° F) for about one hour to provide a hardened mold 12 having an exterior surface 20, and an interior surface 22 facing the casting cavity 14 as shown in the drawing;
- Step (h) Applying a barrier coating layer 24 to the exterior surface 20 of the hardened mold 12 while it is at a preselected third temperature of about 200° C (400° F), the barrier coating layer including a mixture of zircon, fused silica, finely divided graphite, and colloidal silica sol, the AFS grain size of the graphite particles being preferably limited in size to passing through a 200 mesh sieve (less than about 0.075mm or 0.003"), and being most desirably limited to a range of about 600 mesh to 325 mesh (about .01mm to .05mm), and limiting the amount of graphite to a range of about 4 to 20
- Step (i) Drying the barrier coating layer for a preselected period of. time; Step (j) Repeating Steps (h) and (i) a plurality of times, for example three times, to provide a plurality of the graphite containing barrier coating layers 24 to define the multi-layered barrier coating 16 as shown in the drawing; and Step (k) Heating the hardened mold 12 and the barrier coating 16 in a furnace of the like to a preselected third temperature of about 900 to 1400° C (1650 to 2550° F), and preferably about 1050° C (1920° F) to make the ceramic shell mold 6. Subsequently, a ferrous molten metal such as steel is poured into the casting cavity 14 of the ceramic shell mold 6.
- the mold is maintained at a temperature of about 1000° C (1830° F), or slightly below, since the molten metal poured therein is about 1350 to 1700° C (2460 to 3100° F) and this minimizes the temperature differential therebetween.
- drying Step (d) can be achieved under ambient air conditions for a. period of about one-half to one hour, or alternatively the drying can be achieved in an oven or furnace at a temperature slightly above ambient temperature to reduce the holding time.
- the temperature cannot be elevated too much because the pattern either can melt or can expand to the point of unduly stressing the relatively weak walls of the partially complete mold.
- Step (g) can be achieved without the. need for a reducing atmosphere because the multi-layered mold is substantially free of graphite at that stage.
- Step (h) zircon can be replaced by an equivalent amount of alumina silicate.
- the barrier coating is preferably about 78 Wt% of dry materials including the aforementioned zircon or alumina silicate, fused silica, and graphite, and the remaining 22 Wt.% is substantially liquid binder including the colloidal silica sol.
- the preferred proportions of the dry materials in the barrier coating 16 are about 75 parts zircon, 25 parts fused silica, and 11 to 25 parts graphite by weight.
- Steps (h), (i), and (j) were achieved by repetitively dipping the hardened mold 12 while hot into an agitated thixotropic solution of the aforementioned ceramic and graphite materials for about four or five seconds and removing the mold to permit substantial gelling of the ceramic materials during periods of about 30 seconds therebetween in ambient air. The fact that the mold is hot accelerates the gelling and tends to bridge the ceramic materials over any minor imperfections. Such dipping was automatically accomplished by a known mechanical dipping apparatus provided with a suitable timing and counting control system, not shown.
- the test data indicates that the prior art ceramic shell mold with substantially no graphite therein exhibited an undesirably high level of decarburization, and the articles prepared in accordance with one aspect of the present invention exhibited a decreasing degree of decarburization as the proportion of graphite in the barrier coating 16 increased up to about 17 Wt.%.
- decarburization measurements which typically reflect the amount of surface material that must be removed so that any subsequent heat treatment effect of the carbon will be uniform throughout the steel article, the surface smoothness of the test articles was noted.
- the relatively frequent valleys of about 1.5mm (0.060”) maximum depth in the prior art articles were proportionately reduced to minimal blemishes of less than about 0.4mm (0.015") with the addition of' graphite toward 15 Wt.% in the barrier coating 16.
- the effect on decarburization was minimal, whereas at the other end of the range at about 20 Wt.% graphite, the graphite was difficult to keep in suspension, tended to agglomerate and thereby weaken the layers, and did not appear to result in any significant change in the results from that of about 15 Wt.% graphite proportion.
- the broad range of graphite in the barrier coating 16 is about 4 to 20 Wt.%, the preferred range is about 13 to 17 Wt.%, and the most desirable amount is about 15 Wt.%.
- the problems of decarburization and surface blemishes of investment cast articles is more severe when the amount of carbon in the ferrous molten metal is reduced toward 0.1 Wt.% carbon.
- the method of the present invention is particularly useful for minimizing decarburization of steel articles with less than 1.5 Wt.% carbon.
- the preferred method of making the shell mold 6 includes the step of heating the multi-layered mold prior to applying the barrier coating 16 thereto, I contemplate that the multilayered mold substantially free of graphite and the barrier coating can be sequentially built-up and then the resultant structure heated to remove the. wax pattern and to form hardened shell mold 6. In either method, graphite is reactive to oxygen, and the reaction is accelerated as the temperature increases.
Abstract
A method of making a shell mold (6) includes alternately applying a ceramic coating composition (8) and a stucco composition (10) to an expendable pattern, the presence of graphite being substantially avoided therein, and applying a barrier coating (16) thereto including a ceramic powder, a binder, and a preselected amount of graphite. A preferred range of graphite of about 13 to 17 Wt.% in the barrier coating (16) minimizes decarburization of a ferrous article formed in the cavity of the shell mold (6).
Description
Description
Method of Making and Using A Ceramic Shell Mold
Technical Field This invention relates to the preparation of a ceramic shell mold useful for investment casting purposes, and particularly to a method of making a shell mold that will effectively reduce the amount of surface decarburization of a ferrous article formed in the shell mold.
Background Art
Investment casting, also referred to as the "lost wax" process, typically involves alternate applications of a ceramic coating composition and a stucco composition to an expendable pattern in order to provide a multi-layered shell mold. The pattern is usually made of wax, plastic, or similar material which is melted out to leave a correspondingly shaped internal cavity into which molten metal is poured. Unfortunately, there have been many attempts to control the surface finish and the amount of decarburization of steel investment castings. The problem of a metal-mold-atmosphere reaction at the time of pouring and initial stages of solidification of the molten metal has continued to cause an undesirable carbon-free zone adjacent the surface of the article as well as surface blemishes. The methods of minimizing this phenomenon have included casting in a vacuum, use of inert gas shrouding, the addition of reducing agents into the mold cavity prior to pouring, preheating the mold in a carbonaceous atmosphere prior to casting, etc. All of these production steps are costly, time-consuming or raise issues of safety to foundry personnel such as by producing noxious vapors.
U.S. Patent No. 3,184,813 issued to P. J. O'Shea on May 25, 1965 and U.S. Patent No. 3,296,666 issued to N. G. Lirones on January 10, 1967 are representative of the large number of ceramic dip coat compositions used in building up multi-layered shell molds. Frequently, the compositions of the shell mold layers are tailored for the specific metal.
In the past, for example, graphite has been added to the usual coating composition of a ceramic powder and a binder in order to improve surface finish and to minimize the amount of decarburization of steel articles. But while the use of a relatively uniform amount of graphite throughout the full cross section of the shell mold wall has resulted in some improvement in the quality of the castings, surface irregularities and localized carburization have been observed because of the undesirable contact of the molten metal directly with the graphite particles. Moreover, the strength of the individually applied layers is reduced by graphite addition and the shell mold is more costly than desired.
The present invention is directed to overcoming one or more of the problems as set forth above.
Disclosure of Invention
In accordance with one aspect of the present invention, a ceramic shell mold is made by alternately applying coating compositions and stucco compositions to an expendable pattern forming a resultant multi-layered mold substantially free of graphite, and applying a barrier coating to the exterior surface of the multi-layered mold, with the barrier coating including a mixture of a ceramic powder, a binder, and a preselected amount of graphite. Preferably, the amount of graphite in the barrier coating is limited to a range of about 4 to 20 Wt.% of the solid portion.
In another aspect of the invention, the shell mold is preferably made by heating the multi-layered mold and forming a resultant hardened mold before the barrier coating is applied. In another aspect of the invention, the abovedescribed multi-layered mold and barrier coating are heated and a ferrous molten metal poured into the cavity, whereupon after cooling and removal of the article from the mold the article will be noted to have minimal surface carbon depletion and a relatively smooth surface.
Brief Description of Drawing
The sole figure is a diagrammatic and enlarged, fragmentary cross sectional view through a multi-layered shell mold having a barrier coating thereon in accordance with the present invention.
Best Mode for Carrying out the Invention
A preferred method of making a ceramic shell mold 6 comprises the steps of alternately applying a ceramic coating composition 8 and a stucco composition 10 to an expendable or thermally meltable pattern a preselected number of times, firing such multi-layered mold to remove the pattern and provide a hardened mold 12 having an internal casting cavity 14, and applying a barrier coating 16 including a ceramic power, a binder and a preselected amount of graphite as is generally illustrated in the drawing. The presence of any significant amount of graphite is preferably avoided in the multi-layered mold, particularly adjacent the casting cavity 14, and is preferably controlled to a range of about 13 to 17 Wt.% graphite of the total amount of the solid portion of the barrier coating 16.
The aforementioned ceramic coating composition 8 basically includes a ceramic powder and a binder. Typically, the ceramic powder is selected from the group
consisting essentially of fused silica, vitreous silica, crystalline silica, alumina silicate, alumina, magnesium silicate, zircon, zirconium silicate, and clay treated to remove impurities, and can be mixtures thereof. The binder is selected from the group consisting essentially of colloidal silica sol, ethyl silicate, aluminum phosphate, and aqueous alkali metal silicate.
The stucco composition 10 basically includes conventional granular refractory materials such as zircon.
The multi-layered mold, made by alternately applying the ceramic coating composition 8 and the stucco composition 10 a preselected number of times to the pattern is desirably substantially free of graphite. By this term it is meant that less than 0.5 Wt.% graphite is present in the multi-layered mold before the barrier coating 16 is applied.
More particularly, a preferred method of making the ceramic shell mold 6 includes the following steps:
Step (a) Forming an expendable or meltable pattern of wax, plastic or similar material of a construction having the desired shape;
Step (b) Applying a prime or first ceramic coating composition 8 including fused silica flour, finely divided zircon, a limited amount of nitrile polymer latex for low temperature strength, for example 2 Wt.%, and colloidal silica sol including water in the form of a slurry to the pattern by dipping the pattern into an agitated thixotropic slurry thereof, removing the coated pattern therefrom and allowing a preselected amount of draining and initial stages of setting thereof;
Step (c) Applying a coarser or stucco coating composition 10 including granular refractory material such as zircon to the still wet first coating composition 8 by sprinkling same thereon from a conventional
rainfall sander, or alternately by immersing it in a conventional fluidized bed, and with the AFS grain size of the stucco coating composition being generally limited to a range of from about 35 mesh to 20 mesh (about 0.5mm to 0.8mm);
Step (d) Drying the coated and stuccoed pattern for a preselected time period, for example 30 minutes to 6 hours, to a waterproof or gelled shape and providing a first layer 18; Step (e) Alternately repeating Steps (b),
(c), and (d) a preselected number of times while preferably increasing the- relative coarseness of the solid particles therein, for example for nine cycles, and providing a multi-layered "green" mold having a plurality of the layers 18, each layer being about 1mm (.040") thick and intimately associated with each other as is representatively indicated in the drawing;
Step (f) Heating the multi-layered "green" mold in an autoclave at a preselected first temperature of about 180 to 200° C (350 to 400° F) for about 5 to 25 minutes, melting out and removing the pattern, and providing some strength to the mold;
Step (g) Firing the multi-layered mold in a furnace at a preselected second temperature of about 800 to 1400° C (1500 to 2500° F), and preferably about 1000° C (1800° F) for about one hour to provide a hardened mold 12 having an exterior surface 20, and an interior surface 22 facing the casting cavity 14 as shown in the drawing; Step (h) Applying a barrier coating layer 24 to the exterior surface 20 of the hardened mold 12 while it is at a preselected third temperature of about 200° C (400° F), the barrier coating layer including a mixture of zircon, fused silica, finely divided graphite, and colloidal silica sol, the AFS grain size of the
graphite particles being preferably limited in size to passing through a 200 mesh sieve (less than about 0.075mm or 0.003"), and being most desirably limited to a range of about 600 mesh to 325 mesh (about .01mm to .05mm), and limiting the amount of graphite to a range of about 4 to 20 Wt.% of the solid or dry portion of the mixture;
Step (i) Drying the barrier coating layer for a preselected period of. time; Step (j) Repeating Steps (h) and (i) a plurality of times, for example three times, to provide a plurality of the graphite containing barrier coating layers 24 to define the multi-layered barrier coating 16 as shown in the drawing; and Step (k) Heating the hardened mold 12 and the barrier coating 16 in a furnace of the like to a preselected third temperature of about 900 to 1400° C (1650 to 2550° F), and preferably about 1050° C (1920° F) to make the ceramic shell mold 6. Subsequently, a ferrous molten metal such as steel is poured into the casting cavity 14 of the ceramic shell mold 6. Most desirably, the mold is maintained at a temperature of about 1000° C (1830° F), or slightly below, since the molten metal poured therein is about 1350 to 1700° C (2460 to 3100° F) and this minimizes the temperature differential therebetween.
Various modifications of Steps (a) through (k) set forth above can be visualized without departing from the spirit of the present invention. For example, drying Step (d) can be achieved under ambient air conditions for a. period of about one-half to one hour, or alternatively the drying can be achieved in an oven or furnace at a temperature slightly above ambient temperature to reduce the holding time. Of course, the temperature cannot be elevated too much because the
pattern either can melt or can expand to the point of unduly stressing the relatively weak walls of the partially complete mold.
One of the advantages of this method of investment casting is that it is easier to melt out and remove the pattern from the multi-layered mold because it has a thinner section during intermediate Step (f) than the equivalent strength prior art shell mold has at the time of pattern removal. I have also noted a consistently higher quality of the hardened molds 12 when compared with the thicker prior art molds. Furthermore, Step (g) can be achieved without the. need for a reducing atmosphere because the multi-layered mold is substantially free of graphite at that stage. Moreover, in Step (h) zircon can be replaced by an equivalent amount of alumina silicate. The barrier coating is preferably about 78 Wt% of dry materials including the aforementioned zircon or alumina silicate, fused silica, and graphite, and the remaining 22 Wt.% is substantially liquid binder including the colloidal silica sol. Specifically, the preferred proportions of the dry materials in the barrier coating 16 are about 75 parts zircon, 25 parts fused silica, and 11 to 25 parts graphite by weight. In actuality. Steps (h), (i), and (j) were achieved by repetitively dipping the hardened mold 12 while hot into an agitated thixotropic solution of the aforementioned ceramic and graphite materials for about four or five seconds and removing the mold to permit substantial gelling of the ceramic materials during periods of about 30 seconds therebetween in ambient air. The fact that the mold is hot accelerates the gelling and tends to bridge the ceramic materials over any minor imperfections. Such dipping was automatically accomplished by a known mechanical dipping apparatus
provided with a suitable timing and counting control system, not shown.
Industrial Applicability
In order to determine the optimum range of graphite in the barrier coating 16, various weight percentages of graphite were added to the zircon and fused silica portions thereof. Steel articles were made by pouring steel of about 0.3 Wt.% carbon into the heated ceramic shell molds 10 as mentioned above, and the carbon free depth (CFD) and maximum affected depth (MAD) from the surface of the article measured after sectioning of the article. The carbon free depth (CFD) is a measure of the thickness of the surface zone that has experienced substantially total decarburization. The maximum affected depth (MAD) is a measure of the thickness of a thicker surface' zone that has experienced at least partial decarburization or a substantive deviation from the carbon level of the central body portion of the article. The test results were as follows:
Prior Art 4.8 Wt.% 9.1 Wt.% 13.1 & 16.7 Wt.%
CFD 0.3mm 0.13mm 0.10mm 0.05mm (0.012") (0.005") (0.004") (0.002")
MAD 0.9mm 0.64mm 0.51mm 0.3mm
(0.035") (0.025") (0.020") (0.012")
Thus, the test data indicates that the prior art ceramic shell mold with substantially no graphite therein exhibited an undesirably high level of decarburization, and the articles prepared in accordance with one aspect of the present invention exhibited a decreasing degree of decarburization as the proportion of graphite in the barrier coating 16 increased up to about 17 Wt.%.
In addition to such decarburization measurements, which typically reflect the amount of surface material that must be removed so that any subsequent heat treatment effect of the carbon will be uniform throughout the steel article, the surface smoothness of the test articles was noted. For example, the relatively frequent valleys of about 1.5mm (0.060") maximum depth in the prior art articles were proportionately reduced to minimal blemishes of less than about 0.4mm (0.015") with the addition of' graphite toward 15 Wt.% in the barrier coating 16. I found out also that at about 3.4 Wt% graphite the effect on decarburization was minimal, whereas at the other end of the range at about 20 Wt.% graphite, the graphite was difficult to keep in suspension, tended to agglomerate and thereby weaken the layers, and did not appear to result in any significant change in the results from that of about 15 Wt.% graphite proportion.
In view of such beneficial results, the broad range of graphite in the barrier coating 16 is about 4 to 20 Wt.%, the preferred range is about 13 to 17 Wt.%, and the most desirable amount is about 15 Wt.%.
It is of note to appreciate that the problems of decarburization and surface blemishes of investment cast articles is more severe when the amount of carbon in the ferrous molten metal is reduced toward 0.1 Wt.% carbon. Thus, the method of the present invention is particularly useful for minimizing decarburization of steel articles with less than 1.5 Wt.% carbon. Moreover, although the preferred method of making the shell mold 6 includes the step of heating the multi-layered mold prior to applying the barrier coating 16 thereto, I contemplate that the multilayered mold substantially free of graphite and the barrier coating can be sequentially built-up and then
the resultant structure heated to remove the. wax pattern and to form hardened shell mold 6. In either method, graphite is reactive to oxygen, and the reaction is accelerated as the temperature increases. In a crystalline material such as the shell mold, graphite will travel in the porous interstices thpreof during heating. I theorize that during pouring of molten metal into the shell mold a portion of the graphite in the barrier coating 16 diffuses inwardly toward the casting cavity 14 while at the same time a portion of the carbon in the molten metal tends to diffuse into the shell mold where oxygen is available. Under any theory, however, carbon depletion is greatly minimized by the method of present invention. Other objects, aspects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.
Claims
1. A method of making a ceramic shell mold (6) comprising: step (a) alternately applying a coating composition (8) including a ceramic powder and a binder, and then a stucco composition (10) including granular refractory material to an expendable pattern a preselected number of times, drying the coating between applications, and forming a resultant multi-layered mold, said multilayered mold being substantially free of graphite; Step (b) applying a barrier coating (16) to the exterior surface of the multi-layered mold, said barrier coating (16) including a mixture of a ceramic power, a binder, and a preselected amount of graphite within a range of about 4 to 20 Wt.% of the solid portion of the barrier coating (16).
2. The method of claim 1 wherein said preselected amount of graphite is in a range of about
13 to 17 Wt.% of the solid portion of the barrier coating (16).
3. The method of claim 1 wherein said preselected amount of graphite is about 15 Wt.% of the solid portion.
4. The method of claim 1 wherein said preselected amount of graphite includes graphite particles of a size less than about 0.075mm.
5. The method of claim 1 wherein said preselected amount of graphite includes graphite particles limited to an AFS grain size range of about 0.01mm to
0.05mm.
6. The method of claim 1 including heating the multi-layered mold, removing the pattern, and forming a resultant hardened mold (12) having an internal cavity (14) between Steps (a) and (b).
7. The method of claim 6 wherein the barrier coating (16) is applied by repetitively dipping the hardened mold (12) into and removing the hardened mold (12) from an agitated thixotropic solution of the barrier coating (16).
8. The method of claim 6 including maintaining the hardened mold (12) at a preselected temperature above ambient during application of the barrier coating (16).
9. The method of claim 6 including applying the barrier coating (.16) to the hardened mold (12) while the hardened mold has a temperature of about 200°C.
10. The method of claim 6 wherein the barrier coating mixture is a thixotropic solution of zircon, fused silica, graphite and colloidal silica sol.
11. The method of claim 6 wherein the barrier coating mixture is a thixotropic solution of alumina silicate, fused silica, graphite and colloidal silica.
12. A method of investment casting of a ferrous article in a shell mold (6) comprising:
Step (a) applying a coating composition (8) including a ceramic powder and binder to an expendable pattern, said ceramic powder being selected from the group consisting essentially of fused silica, vitreous
silica, crystalline silica, alumina silicate, alumina silicate, alumina, magnesium silicate, zircon, zirconium silicate, and clay, and binder being selected from the group consisting essentially of colloidal silica sol, ethyl silicate, aluminum phosphate, arid aqueous alkali metal silicate;
Step (b) applying a stucco composition (10) including a granular refractory material:
Step (c) alternately repeating Steps (a) and (b) a preselected number of times and forming a multilayered mold;
Step (d) heating the multi-layered mold and forming a hardened mold (12) having an internal cavity (14); Step (e) applying a barrier coating (16) to the exterior surface (20) of the hardened mold (12) at a location spaced from the internal cavity (14), said barrier coating (16) having a solid portion and being a mixture of a ceramic powder, a binder, and a preselected amount of finely divided graphite, said preselected amount of graphite being within a range of about 4 to 20 Wt.% of the solid portion of the barrier coating (16); Step (f) heating the hardened mold (12) and barrier coating (16) and forming a hot shell mold (6); and
Step (g) pouring a ferrous molten metal into the internal cavity (14) of the hot shell mold (6).
13. The method of claim 12 wherein the coating and stucco compositions (8,10) are substantially free of graphite.
14. The method of claim 12 wherein the multi-layered mold includes less 0.5 Wt.% graphite.
15. The method of claim 12 wherein said preselected amount of graphite is in a range of about 13 to 17 Wt.%.
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE7979900983T DE2862282D1 (en) | 1978-12-04 | 1978-12-04 | Method of making and using a ceramic shell mold |
JP50131178A JPS55500934A (en) | 1978-12-04 | 1978-12-04 | |
PCT/US1978/000187 WO1980001146A1 (en) | 1978-12-04 | 1978-12-04 | Method of making and using a ceramic shell mold |
EP19790900983 EP0020373B1 (en) | 1978-12-04 | 1978-12-04 | Method of making and using a ceramic shell mold |
CA000336269A CA1119771A (en) | 1978-12-04 | 1979-09-25 | Method of making and using a ceramic shell mold |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
WOUS78/00187 | 1978-12-04 | ||
PCT/US1978/000187 WO1980001146A1 (en) | 1978-12-04 | 1978-12-04 | Method of making and using a ceramic shell mold |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1980001146A1 true WO1980001146A1 (en) | 1980-06-12 |
Family
ID=22141288
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1978/000187 WO1980001146A1 (en) | 1978-12-04 | 1978-12-04 | Method of making and using a ceramic shell mold |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0020373B1 (en) |
JP (1) | JPS55500934A (en) |
CA (1) | CA1119771A (en) |
DE (1) | DE2862282D1 (en) |
WO (1) | WO1980001146A1 (en) |
Cited By (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2213762A (en) * | 1987-12-22 | 1989-08-23 | Steel Castings Res | Manufacture of ceramic shell moulds |
WO2013192264A1 (en) * | 2012-06-20 | 2013-12-27 | Lexmark International, Inc. | Z-directed printed circuit board components having a removable end portion and methods therefor |
US8658245B2 (en) | 2011-08-31 | 2014-02-25 | Lexmark International, Inc. | Spin coat process for manufacturing a Z-directed component for a printed circuit board |
US8735734B2 (en) | 2009-07-23 | 2014-05-27 | Lexmark International, Inc. | Z-directed delay line components for printed circuit boards |
US8752280B2 (en) | 2011-09-30 | 2014-06-17 | Lexmark International, Inc. | Extrusion process for manufacturing a Z-directed component for a printed circuit board |
US8790520B2 (en) | 2011-08-31 | 2014-07-29 | Lexmark International, Inc. | Die press process for manufacturing a Z-directed component for a printed circuit board |
US8822840B2 (en) | 2012-03-29 | 2014-09-02 | Lexmark International, Inc. | Z-directed printed circuit board components having conductive channels for controlling transmission line impedance |
US8822838B2 (en) | 2012-03-29 | 2014-09-02 | Lexmark International, Inc. | Z-directed printed circuit board components having conductive channels for reducing radiated emissions |
US8830692B2 (en) | 2012-03-29 | 2014-09-09 | Lexmark International, Inc. | Ball grid array systems for surface mounting an integrated circuit using a Z-directed printed circuit board component |
US8912452B2 (en) | 2012-03-29 | 2014-12-16 | Lexmark International, Inc. | Z-directed printed circuit board components having different dielectric regions |
US8943684B2 (en) | 2011-08-31 | 2015-02-03 | Lexmark International, Inc. | Continuous extrusion process for manufacturing a Z-directed component for a printed circuit board |
CN104472025A (en) * | 2012-06-20 | 2015-03-25 | 利盟国际有限公司 | Process for manufacturing a Z-directed component for a printed circuit board using a sacrificial constraining material |
US9078374B2 (en) | 2011-08-31 | 2015-07-07 | Lexmark International, Inc. | Screening process for manufacturing a Z-directed component for a printed circuit board |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE4412798C1 (en) * | 1994-04-14 | 1995-04-06 | Thyssen Industrie | Process for producing and using a ceramic shell as casting mould with reducing properties |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3126597A (en) * | 1961-04-07 | 1964-03-31 | Decarburization in casting of steel | |
US3153826A (en) * | 1962-01-10 | 1964-10-27 | Prec Metalsmiths Inc | Precision casting molds and techniques |
US3656983A (en) * | 1970-10-14 | 1972-04-18 | Us Army | Shell mold composition |
Family Cites Families (4)
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---|---|---|---|---|
SU178952A (en) * | ||||
GB672535A (en) * | 1950-02-06 | 1952-05-21 | Bristol Aeroplane Co Ltd | Improvements in or relating to refractory moulds |
GB1132361A (en) * | 1966-01-17 | 1968-10-30 | Monsanto Chemicals | Casting metals |
GB1160090A (en) * | 1967-07-18 | 1969-07-30 | Adam Dunlop | Moulds and Cores for Casting |
-
1978
- 1978-12-04 WO PCT/US1978/000187 patent/WO1980001146A1/en unknown
- 1978-12-04 JP JP50131178A patent/JPS55500934A/ja active Pending
- 1978-12-04 DE DE7979900983T patent/DE2862282D1/en not_active Expired
- 1978-12-04 EP EP19790900983 patent/EP0020373B1/en not_active Expired
-
1979
- 1979-09-25 CA CA000336269A patent/CA1119771A/en not_active Expired
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3126597A (en) * | 1961-04-07 | 1964-03-31 | Decarburization in casting of steel | |
US3153826A (en) * | 1962-01-10 | 1964-10-27 | Prec Metalsmiths Inc | Precision casting molds and techniques |
US3656983A (en) * | 1970-10-14 | 1972-04-18 | Us Army | Shell mold composition |
Non-Patent Citations (1)
Title |
---|
See also references of EP0020373A4 * |
Cited By (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2213762A (en) * | 1987-12-22 | 1989-08-23 | Steel Castings Res | Manufacture of ceramic shell moulds |
US8735734B2 (en) | 2009-07-23 | 2014-05-27 | Lexmark International, Inc. | Z-directed delay line components for printed circuit boards |
US8943684B2 (en) | 2011-08-31 | 2015-02-03 | Lexmark International, Inc. | Continuous extrusion process for manufacturing a Z-directed component for a printed circuit board |
US9078374B2 (en) | 2011-08-31 | 2015-07-07 | Lexmark International, Inc. | Screening process for manufacturing a Z-directed component for a printed circuit board |
US8658245B2 (en) | 2011-08-31 | 2014-02-25 | Lexmark International, Inc. | Spin coat process for manufacturing a Z-directed component for a printed circuit board |
US8790520B2 (en) | 2011-08-31 | 2014-07-29 | Lexmark International, Inc. | Die press process for manufacturing a Z-directed component for a printed circuit board |
US9009954B2 (en) | 2011-08-31 | 2015-04-21 | Lexmark International, Inc. | Process for manufacturing a Z-directed component for a printed circuit board using a sacrificial constraining material |
US8752280B2 (en) | 2011-09-30 | 2014-06-17 | Lexmark International, Inc. | Extrusion process for manufacturing a Z-directed component for a printed circuit board |
US8822840B2 (en) | 2012-03-29 | 2014-09-02 | Lexmark International, Inc. | Z-directed printed circuit board components having conductive channels for controlling transmission line impedance |
US8912452B2 (en) | 2012-03-29 | 2014-12-16 | Lexmark International, Inc. | Z-directed printed circuit board components having different dielectric regions |
US8830692B2 (en) | 2012-03-29 | 2014-09-09 | Lexmark International, Inc. | Ball grid array systems for surface mounting an integrated circuit using a Z-directed printed circuit board component |
US8822838B2 (en) | 2012-03-29 | 2014-09-02 | Lexmark International, Inc. | Z-directed printed circuit board components having conductive channels for reducing radiated emissions |
CN104472025A (en) * | 2012-06-20 | 2015-03-25 | 利盟国际有限公司 | Process for manufacturing a Z-directed component for a printed circuit board using a sacrificial constraining material |
WO2013192264A1 (en) * | 2012-06-20 | 2013-12-27 | Lexmark International, Inc. | Z-directed printed circuit board components having a removable end portion and methods therefor |
Also Published As
Publication number | Publication date |
---|---|
EP0020373A1 (en) | 1981-01-07 |
EP0020373B1 (en) | 1983-06-08 |
CA1119771A (en) | 1982-03-16 |
EP0020373A4 (en) | 1980-09-29 |
JPS55500934A (en) | 1980-11-13 |
DE2862282D1 (en) | 1983-07-14 |
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