US3644608A

US3644608A - Method of making a non-metallic cast chill

Info

Publication number: US3644608A
Application number: US880074A
Authority: US
Inventors: John J Valentine
Original assignee: JOHN J VALENTINE
Current assignee: JOHN J VALENTINE
Priority date: 1969-11-26
Filing date: 1969-11-26
Publication date: 1972-02-22
Anticipated expiration: 1989-02-22

Abstract

A METHOD OF AND MEANS FOR PRODUCING THE VARIOUS ELEMENTS OF A METAL FORMING MOLD, SUCH AS A COPE, DRAG, CORE, AND/OR CHILL, BY CASTING EACH ELEMENT FROM AN IMPROVED HIGH TEMPERATURE RESISTANT CASTING COMPOSITION AND THEREAFTER TREATING THE METAL FORMING SURFACES OF EACH CAST ELEMENT WITH A MIXTURE OF PHOSPHORIC ACID AND FURFURYL ALCOHOL RESIN TO HARDEN THE SURFACES AND IMPREGNATE THE LATTER WITH CARBON. A METHOD OF AND MEANS FOR PRODUCING A CAST FOUNDRY CHILL INVOLVING SEALING THE OPEN END OF A CHILL FORM TO A SELECTED SURFACE REGION OF A PATTERN, FILLING THE FORM WITH A CHILL CASTING COMPOSITIN, AND CURING THE COMPOSITION TO PROVIDE A FINISHED CHILL FOR USE IN SUBSEQUENT MOLDING OF A PART IN A MOLD CAVITY CONFORMING TO THE PATTERN.

Description

1972 J. J. VALENTINE METHOD OF MAKING A NON-METALLIC CAST CHILL 3 Sheets-Sheet 1 Filed NOV. 26, 1969 L/QU/DS Fred. 2.

L/QU/DS /A/ l/E'A/ TOR JOHN J. MLEA/T/NE A 7'7'0E/VE Y i I ll V/BRA 70/? Feb. 22, 1972 J. J. VALENTINE METHOD OF MAKING A NON-METALLIC CAST CHILL 3 Sheets-Sheet 2 AC/D ETHYL 5 AC/D (3: /N70 /50PROP)/L WA TE/Q ALCOHOL AC/D AND WATER nvm ETHYL 5 & lSOPROPYL ALCOHOL Z/RCON/UM cuT MAGNESIUM CARBON 5/L/CA7E GLASS OXIDE WATER WATER /A/7O B NOE R L/QU/DS INTO DRY lNGRED/ENTS 55 /0 i M FIN ,{ww i I A:

- L LL H L 'yL Ol/EA/ I U'iiHl; "mm "run-h Z4 V/BRATOR /A/l/EA/7'02 54 JOHN J. VALENTINE fli r! A TraQA/EY United States Patent Olhce 3,644,608 Patented Feb. 22, 1972 US. Cl. 264-71 8 Claims ABSTRACT OF THE DISCLOSURE A method of and means for producing the various elements of a metal forming mold, such as a cope, drag, core, and/or chill, by casting each element from an improved high temperature resistant casting composition and thereafter treating the metal forming surfaces of each cast element with a mixture of phosphoric acid and furfuryl alcohol resin to harden the surfaces and impregnate the latter with carbon. A method of and means for producing a cast foundry chill involving sealing the open end of a chill form to a selected surface region of a pattern, filling the form with a chill casting composition, and curing the composition to provide a finished chill for use in subsequent molding of a part in a mold cavity conforming to the pattern.

This application is a continuation-in-part of my co-pending application, Ser. No. 582,832, filed Sept. 29, 1966, and now abandoned and entitled Cast Chill and Method and Means for Fabricating Same.

BACKGROUND OF THE INVENTION Field of the invention This invention relates generally to the metal casting art. The invention relates more particularly to a method of and means for casting the various elements of a metal forming mold, such as a cope, drag, core, and/or chill.

Prior art According to one of its important aspects, the invention provides a novel method of and means for casting a chill for a metal forming mold. Another important aspect of the invention is concerned with a novel method of and composition for casting the various elements of a high temperature metal forming mold, such as a cope, drag, core and/or chill and treating the metal forming surfaces of each element to harden the surfaces and impregnate the latter with carbon. The latter aspect of the invention is particularly suited to the production of mold elements for use in casting high temperature alloys, such as titanium and beryllium alloys.

SUMMARY OF THE INVENTION The use of chills is a well established practice in the molding or casting art. For this reason, the technology of chills and the existing techniques of making and using chills need not be explained in detail. Suflice it to say that the production of a sound casting requires flow of adequate liquid metal to all portions of the mold cavity to fill the cavity completely as the metal solidifies or freezes. This, in turn, necessitates progressive solidification or freezing of the metal in the cavity in such a Way as to assure adequate liquid metal in all portions of the cavity to compensate for the reduction in volume of the metal occasioned by freezing thereof. Unless such proper progressive freezing occurs, the finished cast part may be and generally is defective. For example, a mass of molten metal inherently tends to solidify or freeze inwardly from all sides toward the center. Accordingly, if the mass of metal is permitted to freeze in this inherent fashion, a condition will eventually obtain wherein an inner core of liquid metal is encased in an outer shell of solidified metal. This outer shell blocks flow to the core of the additional liquid feed metal required to compensate for the reduction in the volume of the core metal which occurs during its subsequent freezing. In this case, the finished cast part is characterized by undesirable internal porosity, large internal shrinkage cavities, and other deformities. Similarly, if a relatively large section of a mold cavity is fed with liquid metal through a relatively narrow section of the cavity, the metal tends to freeze more rapidly in the narrow cavity section than it does in the large cavity section. In this case, if the metal freezes prematurely in the narrow section, flow of additional liquid feed metal to the large cavity section will be blocked. Here again, the finished cast part is characterized by undesirable internal porosity, large internal shrinkage cavities, and other deformities. The same adverse results obtain when irn proper progressive freezing of the liquid metal occurs in the cavities. The problems discussed above are particularly serious when the metal being cast is one, such as aluminum, which has a relatively high coefiicient of thermal expansion owing to the fact that such a metal undergoes a relatively large reduction in volume as it freezes.

In some cases, the proper progressive freezing of liquid metal within a mold cavity necessary to the production of a sound casting may be induced solely by proper design of the casting and utilization of the proper riser ring, gating, and pouring techniques. In other cases, the production of a sound casting requires, in addition, selective chilling of the mold cavity. Generally speaking, such chilling involves the rapid conduction of heat away from selected portions of a mold cavity, thereby to establish within the cavity a temperature gradient, or temperature gradients, which induce proper progressive freezing of the metal within the cavity. Thus, the basic aim of chilling is to induce an initial freezing of the metal at a selected location or selected locations within a mold cavity remote from the riser or risers, such that progressive freezing of the metal occurs toward and terminates at the risers. In this way, sufiicient liquid peat metal is continuously available at the advancing front of the freezing metal to compensate for the reduction in volume of the metal occasioned by freezing.

Selective chilling of a mold cavity may be accomplished in various ways. The present invention is particularly concerned with the chilling technique which involves the placement of thermally conductive plugs, commonly referred to as chills, within the mold. One important aspect of the invention, for example, relates to an improved chill which avoids certain of the inherent disadvantages of the existing chills. Thus, the existing chills are commonly constructed of metal, such as aluminum, iron, copper, or other metal having a sufiiciently high melting point and coefiicient of thermo conductivity. In some cases, carbon blocks are employed as chills. These chills are coated with a suitable parting agent, such as a ceramic composition, to prevent adherence to the chills of the metal being cast. The ceramic or other parting agent is commonly applied to the chills by spraying or brushing. After each part is cast, the conventional metal chills are removed from the mold, cleaned, and recoated with parting agent to condition the chills for reuse. In the event that a chill incurs damage in use, which happens quite frequently, owing to the rough manner in which the chills are commonly handled, the damaged chill must be repaired or refaced. The steps incident to initial fabrication of the existing chills, conditioning of the chills for reuse, and repair of damaged chills are time consuming and involve substantial cost. Moreover, the number of chills which are unavailable for use at any given time, due to reconditioning or repair, may be quite large. As a consequence either a supply of spare chills, sulficient to satisfy production requirements, must be maintained at all times, or the production of finished castings must be temporarily halted until the previously used chills are available for reuse. In the first case, the chill production cost is high. In the second case, production delay costs are high.

As noted earlier, another important aspect of the invention is concerned with the production of high temperature metal forming molds for high temperature alloys, such as titanium and beryllium alloys. Heretofore, the various elements of such molds, such as the drag and cope, have been produced by two different methods. According to one method, each mold element is constructed from a carbon block which is machined to the desired shape. According to the other method, each mold element is cast using a mixture of a furfuryl alcohol resin and powdered carbon or graphite.

It is a general object of the present invention to provide a novel non-metallic cast chill, as well as a novel method of and means for producing the chill by casting the latter in direct contact with a pattern of the part to be molded, and a chill casting composition.

Another object of the invention is to provide a nonmetallic cast chill of the character described which may be conveniently produced in sufficient quantity and at sufficiently low cost to render the chill disposable or reusable, as desired.

Another object of the invention is to provide a nonmetallic cast chill of the character described having an optimum shelf life, whereby a number of chills may be stored for long periods of time without deterioration, thus to provide a constant available supply of the chills and thereby eliminate casting production delay time due to the unavailability of chills.

Another object of the invention is to provide a method of and a non-metallic composition for producing the various elements of a high temperature metal forming mold, such as a cope, drag, core, and/or chill for high temperature metals such as titanium and beryllium alloys by casting each element from the composition and then treating its surfaces to harden the surfaces and impregnate the latter with carbon.

Other objects, features and advantages of the present invention will become apparent to those versed in the art from a consideration of the following description, the appended claims and the accompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates, in semi-diagrammatic fashion, the present method of the means for casting a non-metallic chill according to the invention;

FIG. 2 illustrates an oven in which the cast chill is cured during the final step of the method;

FIG. 3 is a vertical section through the cope of a molding flask illustrating a finished chill according to the invention positioned in the cope and the latter being packed with molding sand in preparation for a casting operation;

FIG. 4 is a vertical section through the completed mold containing the chill;

FIG. 5 is a flow diagram of the present chill casting method; and

'FIG. 6 is a fiow diagram of the present method of producing high temperature mold elements.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference is made first to FIGS. 1 through 4 of the drawings which illustrate an exemplary method of and means for casting a chill 10 according to the invention. It should be understood that the chill shape shown, as

well as the means for casting the chill, are intended to be merely illustrative and not limiting in nature and that the nature may be utilized to cast chills of any desired shape by following the general steps outlined below. Moreover, While the invention will be explained primarily in connection with foundry or sand casting, it will become evident as the description proceeds that the invention may be utilized to produce a chill for any of the known molding or casting techniques, i.e., sand casting including green sand, dry sand, and CO pressures, permanent mold casting, semi-permanent mold casting, plaster casting, and lost wax investment casting.

With the foregoing discussion in mind, the first step in producing a chill 10 according to the invention involves the selection of a pattern 12 having the shape of a finish part to be cast. For convenience, the illustrated pattern is shown to have a simple shape including a relatively large, generally semi-spherical portion 14 and a reduced niche 16 extending from the semi-spherical portion. The fiat side of the casting is secured to a plate 17.

The second step of the present chill forming or casting method involves the selection of a surface region on the pattern 12 corresponding to the location, in a mold cavity conforming to the pattern, at which chilling will be required during subsequent casting of a finished part in the cavity to induce proper progressive freezing of liquid metal in the cavity. It is obvious that this mold cavity chill location, and hence the selected surface region of the pattern, will vary from one pattern to another. The selected surface region of the illustrated pattern 12 corresponding to the mold cavity location at which chilling will be required to induce proper progressive freezing of liquid metal in the mold cavity is designated by the reference numeral 18. In regard to selection of the surface region 18 of the patern 12, attention is directed to FIG. 4, wherein it will be observed that the pattern is intended to be employed in conjunction with a core 20 to produce a mold cavity 22 for casting a finished part having an external shape corresponding to that of the pattern and an internal shape corresponding to that of the core. The mold cavity 22 has an enlargement 24, defined by a recess in the core, for forming a corresponding internal enlargement of a cast part. The mold cavity 22 is formed, in the well known way, by first placing the cope section 26 and then the drag section 28 of a molding a flask 30 on the pattern plate 17, about the pattern 12, and packing the interior of the cope section and drag section with molding sand 31, thus to form the cope and drag of a mold. After removal of the pattern, the cope and drag are assembled with the core 20 therebetween, in the manner illustrated in FIG. 4, to define the completed mold cavity 22. In actual practice, a pair of patterns 12, secured to opposite sides of a match plate, may be utilized in forming the mold cavity. During subsequent casting of a finished part in the mold cavity 22, the latter is fed with liquid metal through a riser 32 which opens to the niche portion of the cavity. The cavity is vented at 34 in the usual way. At this point, it will be evident to those skilled in the art that proper progressive solidification or freezing of liquid metal within the cavity 22 requires chilling of the metal in the vicinity of the cavity enlargement 24. The selected surface region 18 of the pattern 12 corresponds to this portion of the mold cavity. I

The third step of the present chill forming or cast ng method involves the selection of a chill form 36 having an opening 38 conforming approximately to the selected surface region 18 of the pattern 12 and bounded by a seating edge 40 having a contour conforming substantially to the surface contour of the pattern about such surface region. The illustrated chill form 36 has the general shape of a truncated pyramid and comprises four tapered wall members or plates 42 placed edge to edge, as shown, and releaseably secured in assembled relation by any convenient means 44, as nails, straps, rubber bands, or the like. The wall members or plates 42 of the chill form 36 may be constructed of wood, metal, plastic, or any other suitable material. The completed chill form has an opening 46 remote from its opening 38 through which the chill casting composition of the invention, to be described presently, may be introduced into the form.

According to the next step of the present chill casting method, the chill form 36 is placed in chill casting relation to the pattern 12, wherein the seating edge 40 of the form seats against the surface of the pattern about its selected surface region 18. The juncture between the pattern 12 and the chill form 36 is sealed, to prevent leakage of the casting composition therebetween, in any con venient way, as by pressing modeling clay 48 about the chill form in the manner shown.

The final step of the present chill forming or casting method involves introduction of the present chill casting composition into the chill form 36 through its opening 46. This composition is then permitted to set in the form, thus to produce a rigid chill according to the invention, after which the chill is removed from the form and cured in an oven 50. The completed chill 10 has a face 52 conforming to the selected surface region 18 of the pattern 12. In order to prevent adherence of the chill casting composition to the pattern 12 and he chill form 36, the selected surface region 18 of the pattern and the inner surfaces of the chill form may be coated with a suitable parting agent, such as petroleum jelly, silicone oil, or the like.

After curing, the chill 10 is ready for use. In such use, the chill is supported in proper position relative to the pattern 12, wherein the chill face 52 is disposed adjacent or in seating contact with the selected surface region 18 of the pattern, during forming of the mold cavity 22 in the manner explained earlier. In the illustrated practice of the invention, for example, the chill 10 is supported in the cope 26 of the molding flask 30, atop the pattern 12 in the manner illustrated in FIG. 3, during packing of the cope with the molding sand to form the upper half of the mold cavity 22. The chill remains imbedded in the molding sand when the pattern is removed from the cope. Accordingly, in the completed mold of FIG. 4, the chill face 52 is exposed to and forms a wall portion of the mold cavity 22. During subsequent casting of liquid metal in the mold cavity 22, the chill 10 is effetive to conduct heat away from the adjacent portion of the cavity, thus to assure proper progressive solidification or freezing of the metal in the cavity and thereby yield a sound casting.

As noted earlier, one important advantage of the present non-metallic cast chill 10 resides in the fact that it may be produced in sufficient quantity and at sutficiently low cost to render the chill reusable or disposable, as desired. Disposal of the chill, of course, is desirable for the reason that it eliminates the need for cleaning and other conditioning of the chill for reuse, and hence the complications attendant to such reconditioning. Moreover, the necessity of repairing chills which are damaged during removal from the molding sand after casting is eliminated.

The discussion thus far has related only to the use of the present chill in connection with sand casting. As noted earlier, the present chill may be used, as well, in any of the other casting techniques, to wit, permanent mold casting, semi-permanent mold casting, plaster mold casting, and lost wax investment casting. In these other casting techniques, the chill is supported in the mold in much the same manner as a conventional metal chill. In plaster casting, for example, the chill is properly positioned relative to the pattern and liquid plaster is poured about the chill and over the pattern in such a way that the chill is imbedded in the finished plaster mold. In investment casting, permanent mold casting, and semi-permanent mold casting, the chill is mechanically secured or attached to the mold in an area formed by a core print. The chill is thus secured by any suitable means, such as gluing or clamping the chill in position or by retaining the chill in position with the aid of weights. As also noted earlier, the present chill may be employed in any of the known techniques of sand casting, including the green sand, dry sand, and CO processes. In the CO process of sand casting, the chill is positioned relative to the pattern and sand, mixed with sodium silicate, is rammed about the chill and pattern, in much the same way as described earlier. CO is then passed through the sand to cause setting of the sodium silicate, thus to provide a relatively hard mold.

A chill casting composition of the invention is composed of the following ingredients combined in the approximate proportions indicated, which proportions may be varied, as explained below, to alter the properties of the cast chill.

Ingredients:

(1) Ethyl silicate (40% concentration)--26,000 cc. (2) Isopropyl alcoholl8,000 cc. (3) Water4,000 cc. (4) Hydrochloric acid (36% acid concentration)- (5) Ground or powdered carbon2,000 cc. (6) 78 mesh zirconium silicate2,000 cc. (optional) (7) Cut glass fiber long)-1 ounce (optional) (8) Magnesium oxide (light fired)1 /2 ounce.

The combined ingredients of items 1 through 4 in the above list constitute a binder. The ingredients of items 5 through 8 constitute dry ingredients or solids. According to the present invention, the binder (items 1 through 4) is diluted with water in the approximate proportions of 2,000 cc.. binder, 4,000 cc. water, to form a diluted binder mixture, and this mixture is combined with the solids (items 5 through 8) to form the final casting composition of the invention which is introduced into the chill form 36. According to the preferred practice of the invention, as it is illustrated in FIG. 5, the ethyl silicate and isopropyl alcohol of items 1 and 2 are mixed and stored as are the water and hydrochloric acid of items 3 and 4, since these mixtures are stable and have an indefinite storage life. These two separate mixtures are then combined before use to form the binder. These two mixtures, upon combination, undergo hydrolyzing with resultant generation of heat. According to the present invention, the combined mixture, or binder, is permitted to cool to ambient temperature before use. The cooling time of the binder is typically on the order of twelve hours. After cooling, the binder is combined or diluted with water, as indicated above. Just prior to use, the diluted binder-water mixture is combined with the dry ingredients of items 5 through 8 to form the completed casting composition which is then introduced into the chill form 36.

In carrying out the above steps to produce the casting composition of the invention, it is desirable and necessary to mix certain of the ingredients in the proper sequence. When mixing the ethyl silicate and isopropyl alcohol, for example, it is immaterial whether the ethyl silicate is added to the isopropyl alcohol or the isopropyl alcohol is added to the ethyl silicate. However, when mixing the hydrochloric acid and water, it is essential to pour the acid into the water, rather than the water into the acid, to avoid the possibility of explosion. With regard to mixing of the ethyl silicate-isopropyl alcohol mixture and the water-acid mixture to produce the binder, it is desirable or necessary to combine these mixtures by pouring the acid-water mixture into the ethyl silicate-isopropyl alcohol mixture to avoid very rapid initial hydrolization and resulting jellying of the combined mixture or binder. Mixing of the dry ingredients may be accomplished in any order desired. Preferably, however, the solids of larger proportions, i.e., the carbon and zirconium, are mixed together first, after which the solids of minor proportions, i.e., the cut glass and magnesium oxide are added to the carbon-zirconium mixture to insure optimum blending of the solids. The final casting composition of the invention, which is produced by mixing the diluted binder mixture and the solids hardens at a very short period of time, typically on the order of two to three minutes, whereby the binder and solids are not mixed until just before casting of the chill, as explained above.

As noted above, the proportions of the various ingredients of the present chill casting composition may be varied. For example, the hardness of the binder of the casting composition depends upon the percentage of ethyl silicate in the binder. In a typical binder mixture according to the invention, the concentration of ethyl silicate is on the order of 18%. Increasing the concentration of ethyl silicate above 18% increases the hardness of the binder. Reducing the concentration of ethyl silicate below 18% reduces the hardness of the binder. Thus, the hardness of the final chill of the invention may be controlled, to a degree, by adjusting the concentration of ethyl silicate in the chill casting composition. A relatively soft chill, for example, may be desired in certain applications, such as where an internal chill is to be removed from a core within a casting. A relatively hard chill, on the other hand, may be desirable where a chill is subjected to rela tively high pressure, as where a relatively heavy mass of metal is cast about the chill.

The relative hardness or softness of the completed chill may also be controlled, to some extent, by adjusting the concentration of isopropyl alcohol in the chill casting composition. Increasing the proportion of this ingredient relative to the ethyl silicate in the composition, for example, reduces the hardness of the final chill. Similarly, reducing the proportion of isopropyl alcohol relative to the ethyl silicate increases the hardness of the final chill.

The concentration of acid in the casting composition affects the rate of hydrolization which occurs when the binder is mixed with the solid ingredients of the casting composition. Increasing the acid concentration, for example, increases the rate of hydrolization. Similarly, re ducing the acid concentration reduces the rate of hydrolization.

The zirconium element of the present casting composi tion is employed for its weight, and also because of its heavier or coarser granular structure. This relatively coarse granular structure of the zirconium is desirable for the reason that it prevents surface crazing of the final chill which would occur if such a coarse granular structure were omitted from the chill casting composition.

The cut glass fibers of the present casting composition serve as reinforcing elements. Accordingly, the concentration of glass fibers in composition may be varied, depending upon the desired strength of the final chill.

The concentration of magnesium oxide in the casting composition determines the setting rate of the composition. Thus, increasing the concentration of magnesium oxide accelerates or reduces the setting time of the composition. Similarly, reducing the concentration of magnesium oxide retards or increases the setting time of the composition. The setting time of the casting composition may be also regulated, to a degree, by varying the concentration of water in the composition.

The relative proportions of binder and dry ingredients or solids in the casting composition determines the viscosity of the composition in its initial fluent condition. Thus, reducing the proportions of the dry ingredients has the effect of reducing the viscosity of or thinning the fluent casting composition. Similarly, increasing the proportions of dry ingredients has the effect of increasing the viscosity of or thickening the fluent casting composition. A fluent casting composition of relatively low viscosity may be desirable, for example, to permit casting of a chill with relatively fine detail. In other applications, a relatively aviscous chill casting composition may be preferred.

When introducing the fluent casting composition of the invention into the chill form 36, to cast a chill 10 according to the invention, it is important that no air be trapped between the chill composition and the surface of the pattern 12 in order to avoid the formation of a rough face 52 on the chill. Such a rough chill face, of course, would produce a correspondingly rough surface on the cast part in the region of the chill. Such air entrapment may be prevented in various ways. For example, the surface region 18 of the pattern which is contacted by the chill casting composition may be initially coated with such composition, as by brushing, prior to actual casting of the chill. Alternatively, the casting composition Within the chill form may be agitated, as by a vibrator 54, during casting of the chill.

As noted earlier, the final step of the present chill cast ing method involves curing of the set chill composition within the oven 50. According to typical practice of the invention, curing is typically accomplished at 350 F. over a period of approximately twelve hours.

As stated earlier, the chill casting technique and casting composition discussed above constitute one important aspect of the invention. Another important aspect of the invention is concerned with the production of high temperature mold elements to be assembled into a mold for use in casting high temperature metals, particularly titanium and beryllium. FIGURE 6 shows a flow diagram depicting this latter inventive aspect as it is practiced to produce the drag 28a of a metal forming mold. According to this inventive aspect, the same ingredients used to form the chill 10 are mixed in the proportions and in the manner explained earlier in connection with the chill to form a casting composition. In this regard, it should be noted that mixing the ethyl silicate, isopropyl alcohol, water and acid as we discussed in the earlier description and illustrated in the how diagram of FIGURE 5 produces the hydrolyzed ethyl silicate mixture represented by the large box in the upper left hand area of the fiow digrarn of FIGURE 6. The resulting casting composition is then poured into the lower drag section of the molding flask 30, about the lower half of the pattern 12, and allowed to set, after which the pattern is removed to form the drag 28a.

The next step of method involves treating the metal forming surfaces of the drag 28a, i.e., the surfaces of the mold cavity produced by the pattern 12, with an agent which hardens these surfaces and impregnates the latter with carbon. According to the present invention, the agent used for this purpose is a mixture of phosphoric acid and furfuryl alcohol no-bake resin combined in the following proportions:

Parts phosphoric acid 1 Furfuryl alcohol} 10 No-bake resin In the case of the drag 28a under discussion, the above mixture is poured into the drag mold cavity as shown in FIGURE 6 and allowed to remain in the cavity for several minutes. During this time, the mixture permeates the walls of the cavity. The excess mixture is then poured from the mold cavity and the drag is placed in an inert gas oven 50a and heated to a curing temperature on the order of 1500 F. at a rate of temperature increase on the order of F. per hour. The drag is then heated at the final curing temperature of 1500 F. for a period of about four hours. This curing action hardens the resin which impregnates the surface of the drag mold cavity. The furfuryl alcohol in the resin also impregnates the cavity surfaces with carbon. These hard, carbon impregnated walls of the drag 28a adapt the latter for molding high temperature metals, particularly titanium and beryllium alloys.

While the above discussion deals with forming the drag 28a of a high temperature metal forming mold, it is evident the same procedure may be followed to produce the cope of the mold. Moreover, a core and chill for this high temperature mold may be produced in essentially the same manner except that casting composition is formed to the desired shape in a mold cavity rather than about a pattern and the surfaces of the core and chill are treated with the acid-resin mixture by a clipping or coating technique rather than by the pouring technique referred to above.

Those versed in the art will appreciate that the present invention achieves the objects and realizes the advantages hereinbefore mentioned.

Although a specific embodiment of the present invention has been illustrated and described herein, it will be understood that the same is merely exemplary of presently preferred embodiments capable of attaining the objects and advantages hereinbefore mentioned, and that the invention is not limited thereto; variations will be readily apparent to those versed in the art, and the invention is entitled to the broadest interpretation within the terms of the appended claims.

The inventor claims:

1. The method of making a non-metallic cast chill to be used in casting a finished part in a mold cavity, which comprises the steps of:

selecting a pattern having the shape of the finished part,

selecting a surface region on said pattern corresponding to the region of said mold cavity where chilling is required,

selecting a fluent settable non-metallic thermally conductive chill casting composition comprising the following ingredients combined in approximately the proportions indicated:

hydrolyzed ethyl slicate48,l50 cc.

powdered carbon-2,000 cc.

fibers-l ounce magnesium oxide (light fired)-l% ounce,

casting said composition to a desired chill shape with said composition disposed in contact with said surface region of said pattern, and

curing said composition at a temperature of approximately 350 F. for a period of approximately twelve hours to provide a finished chill having a face corresponding in contour to said surface region of said pattern.

2. The method according to claim 1 wherein:

said casting step involves selecting a hollow chill form having an opening conforming approximately to said surface region of said pattern and bounded by an edge conforming approximately to the surface contour of said pattern about said surface region, placing said chill form in contact with said pattern in such a way that said chill form edge seats against said pattern about said surface region, and introducing said casting composition into said chill form.

3. The method according to claim 1 wherein:

said hydrolyzed ethyl silicate comprises the following ingredients combined in approximately the proportions indicated:

ethyl silicate-26,000 cc.

isopropyl alcohol-18,000 cc.

water-4,000 cc.

hydrochloric acid-36% concentration-150 cc.

said ingredients are combined to form said casting composition by initially combining said ethyl silicate and isopropyl alcohol to form a first liquid mixture and combining said water and acid to form a second liquid mixture, thereafter combining said liquid mixtures to form a binder, thereafter combining said binder with water to form a diluted binder, and thereafter combining said diluted binder with said carbon, fibers, and magnesium oxide to form said casting composition.

4. The method according to claim 1 including the additional step of:

coating said selected surface region of said pattern with a thin layer of said casting composition prior to casting of said chill, thereby to prevent entrapment of air between said casting composition and said surface region.

5. The method according to claim 1 including the additional step of:

vibrating said casting composition during setting thereof to prevent entrapment of air between said casting composition and said selected surface region of said pattern.

6. The method of producing an element, such as a cope, drag, core or chill, for a high temperature metal casting mold which comprises the steps of:

preparing a casting composition comprising the follow ing ingredients combined in approximately the proportions indicated:

hydrolyzed ethyl silicate48,l50 cc.

powdered carbon-2,000 cc.

fibers-1 ounce magnesium oxide (light fired)1 /2 ounce,

casting said composition to a desired shape having a surface which contacts and forms the molten metal being cast in the mold,

treating said metal forming surface with a mixture comprising the following ingredients combined in approximately the proportions indicated:

% phosphoric acid-1 part furfuryl alcohol no-bake resin-1O parts,

curing the treated element casting by heating the latter to about 1,500 F. at a rate of about per hour and holding the l,500 F. temperature for about four hours.

7. The method according to claim 6 wherein:

said element casting has a cavity the wall of which provides said metal forming surface, and

said treatment step involves filling said cavity with said treatment mixture and after a few minutes pouring the excess mixture from said cavity.

8. The method according to claim 6 wherein:

said metal forming surface of said element is en external surface, and

said treatment step involves coating said surface with said treatment mixture.

References Cited UNITED STATES PATENTS 1,768,546 7/1930 Curtis 264-71 2,303,303 11/1942 Schleicher 264-333 2,703,913 3/ 1955 Hinde 264-220 2,897,572 8/ 1959 Hansen 264-71 3,060,543 10/ 1962 Shaw 264-71 3,213,497 10/1965 Scott 264-225 3,366,720 1/ 1968 Burger 264-333 3,371,135 2/1968 Goodwin 264-71 DONALD J. ARNOLD, Primary Examiner US. Cl. X.R.