WO2006044713A2

WO2006044713A2 - Insert cladding technique for precision casting processes

Info

Publication number: WO2006044713A2
Application number: PCT/US2005/037107
Authority: WO
Inventors: James A. Buckley
Original assignee: Chipless Metals Llc
Priority date: 2004-10-20
Filing date: 2005-10-18
Publication date: 2006-04-27
Also published as: WO2006044713A3

Abstract

A process is disclosed of placing a thin walled inserts in or around a core, casting a part about the core, and removing the core from the cast part while leaving the insert in the part to form one or more surface features of the cast part. In the case of melt away cores used in metal melt-away semi-solid forming processes, metal inserts are placed within a die during the formation of the core. The core with inserts is then placed into a second die. Shot is added to the die and, after the shot cools and solidifies to form a casting, the core is removed from the casting mechanically or otherwise while the inserts remain bonded to the casting. The process increases the precision and durability of appendages and intricate internal features of the casting as compared to previous melt-away processes.

Description

INSERT CLADDING TECHNIQUE FOR PRECISION CASTING PROCESSES

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to precision casting processes and, more particularly, relates to a process utilizing clad removable cores to produce internal surface features such as seal grooves in a cast part while leaving the thin cladding in the finished part.

2. Discussion of the Related Art

Substantial developments have recently occurred in melt-away core casting processes in which a metal part is cast about a core formed from a metal having a lower melting point than the melting point of the metal casting and in which the core is subsequently melted away. Improvements to these processes are disclosed, for example, in U.S. Patent Nos. 6,564,856; and 6,427,755, which are assigned to Chiplesss Metals LLC and which are incorporated by reference herein. The above referenced Chipless Metals patents disclose a technique for precision zinc coring of aluminum castings formed from semi-solid metals. This metal melt-away core technique allows complex internal shapes to be formed in castings, allowing for more robust designs and lower costs than those achieved with the traditional cast and machine processes. Despite the success of casting using semi-solid thixotropic metal alloys, some limits of the metal melt-away core techniques have been found. Specifically, it has been recognized that certain parts of a core may tend to be susceptible to overheating as a result of their unique geometric shapes and orientation within the metal casting. For example, projections in the core such as rings or small appendages that become surrounded by the metal cast are particularly susceptible to the detrimental effects of overheating. As the metal shot of the casting is injected over the core, these appendages are often surrounded by thick regions of the relatively high energy cast metal. The heat transfer between the cast metal and the core may, under some circumstances, lead to alterations of the thin appendages and other intricate features. The subsequent alterations can have a detrimental effect on the precision of the end product. The need, therefore, remains for an improved, versatile melt-away core casting process that can form precision castings economically and with high repeatability. There is a further need for such a process that can form intricate internal core shapes without melting. There is still further a need for a more generic removable core casting process that adds additional versatility and reliability to the casting process. There is also a need for a fine surface finish and the absence of any parting lines.

OBJECTS AND SUMMARY OF THE INVENTION

It is therefore a principal object of the invention to provide a process for producing precision castings that have complex internal and/or external geometries and that require little or no machining of their interior surfaces after core removal.

A second object of the invention is to provide a process that meets the first principal object and that is highly repeatable.

A third object of the invention is to provide a process that meets the first principal object and that does not place unnecessary restraints on production. A fourth object of the invention is to provide a process that meets the first principal object and that can be practiced economically.

A fifth object of the invention is to provide a process that meets the first principal object and that can be used to produce parts with highly complex surface geometries.

A sixth object is to provide a process for producing precision castings that generates a superior surface finish, dimensional accuracy, and negates the appearance of parting line marks without the need for machining.

In accordance with the present invention, at least some of these objects are achieved by cladding removable cores with inserts that remain in the cast part after the core is removed from the cast part, either mechanically or by melting, dissolving or otherwise. These inserts can be used to protect those parts of the metal core that by geometry or orientation within the casting, would be otherwise susceptible to overheating in, for example, aluminum or magnesium casting processes. The process includes placing a core having at least one insert within a die while retaining a die cavity between the core and an inner surface of the die, filling the die cavity with a shot of a metal, allowing the shot to cool and solidify, and removing the core from the part such that the inserts remain imbedded in the cast part after core removal. The above noted problems associated with overheating are successfully overcome through the inclusion of the thin sheet metal inserts in the core production process. In addition, the inserts can be utilized to form areas of the part that must be of the finest surface finish and dimensional accuracy. The inserts negate parting line marks in the cast parts without the need for machining. These inserts can also be used advantageously to locally promote wear resistance, corrosion resistance, and high pressure hydraulic sealing by the selection of insert material properties and advantageous surface treatment such as coatings.

In another preferred embodiment, thin inserts are placed into a zinc core mold and the zinc shot is cast within the thin inserts. The inserts thus form a protective external shell around the core in areas that could be thermally damaged by the aluminum casting process if left unprotected. These precision clad zinc cores are then placed into the aluminum or magnesium part casting molds. The molds are closed. The hot aluminum or magnesium semi-solid casting material is then formed over these clad cores. The casting cools and solidifies. Although the heat from the aluminum solidification and cooling is largely absorbed by the core, the cladding protects the thermally sensitive areas of the zinc core from melting during the casting process thus preserving the quality of the final casting. During solidification, the aluminum casting shrinks down on the clad core with tremendous force, becoming integral to the core and the clad inserts. After solidification, the composite aluminum part with its clad zinc core is then ejected from the casting tooling and submerged into a hot bath that melts and washes out all of the zinc that had defined the core leaving the aluminum with the shape of the original core impressed on its interior surfaces. The precision clad inserts are now captured by the cast aluminum part and become an integral part of this newly formed casting. These clad inserts are retained tightly due to the shrinkage forces of the cooled aluminum casting. The inserts are now imbedded within the cast part and provide a surface that is smooth, hard, and precise without parting lines that otherwise would be a natural impression in the aluminum from an unclad cast core.

The inventive clad cast surfaces in the aluminum casting are ideal for such features as hydraulic seal grooves, high wear surfaces, precision bores and other commonly machined parts. Although described in reference to a particular preferred embodiment, the clad inserts can be precision formed with many materials such as aluminum, stainless steel, titanium, brass, bronze, copper, copper alloys, carbon, steel, and other known metals. The inventive inserts can further be coated, plated, or heat treated to give surface properties that are very advantageous to the final part versus a raw aluminum cast or machined surface. These coatings are very economical since the coating of these small, thin parts is much less expensive than applying it to the entire cast part. The inventive method eliminates the need for machining of the castings in these clad areas, typically resulting in a major cost savings even while producing a highly superior part for durability. When used with the advantages of the metal melt core technology it is often the case that all secondary machining can be eliminated. These inserts can provide localized durability that often results in much greater life in the final part usage. This insert technique works very well when used with the metal melt-away core techniques disclosed in U.S. Patent Nos. 6,564,856 and 6,427,755, but is not limited to either metal cores or to semi-solid casting processes.

It is understood that the present technique can also be incorporated into the use of sand cores for permanent mold and sand casting as well as salt cores in use with high pressure die casting, and lost foam or evaporative pattern casting. The technique can also be used with conventional steel slide cores employed in die castings and permanent mold casting. In each case, the insert is utilized to give precision geometry, good surface finish, and eliminate harmful parting lines that would otherwise be caused by the cores. Metal melt cores are more durable, precise, and give better surface finishes than these other coring techniques but the sand, salt, and conventional steel slide cores have a higher temperature capability. In use with sand and salt cores, it is possible to use this technique to cast aluminum, magnesium and higher temperature materials such as copper alloys, iron, and steel. It is possible to do this with liquid metal casting techniques as well as for semi-solid techniques.

Other objects, features, and advantages of the present invention will become apparent to those skilled in the art from the following detailed description and the accompanying drawings. It should be understood, however, the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred exemplary embodiments of the invention are illustrated in the accompanying drawings in which like reference numerals represent like parts throughout, and in which:

FIG. 1 is a perspective view of a die for forming a core utilized in the melt-away casting process of a single piston disc brake caliper housing in accordance with a preferred embodiment of the present invention;

FIGs. 2a-2d are perspective views of metal cladding inserts that may be inserted into the die of FIG. 1 in accordance with a preferred embodiment of the present invention;

FIG. 3 is a perspective view illustrating the metal inserts placed within the core die prior to casting the core;

FIG. 4 is a perspective view of the cast core within its die with the cladding cast integrally;

FIG. 5 is a perspective view of the cast core and integral claddings after being removed from the die FIG. 6 is a perspective view of the cast core of FIG. 5 inserted into a caliper casting die;

FIG. 7 is a perspective view illustrating the caliper housing being cast within die of FIG. 6;

FIG. 8 is a sectional view of the clad core within the caliper housing casting of FIG. 7;

FIG. 9 A is a perspective view of the composite core and caliper housing casting following the casting of the caliper housing;

FIG. 9B is an alternative perspective view of the composite structure of FIG. 9A;

FIG. 1OA is a perspective view of the caliper housing with the inserts imbedded following core melt-away;

FIG. 1OB is an alternative perspective view of the caliper housing of FIG. 1OA; and

FIG. 1OC is another alternative perspective view of the caliper housing of FIG. 1OA.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A casting process in accordance with a preferred embodiment of the present invention is generally characterized by the casting of thin walled inserts, generally designated by the numerals 20 and 22, into a removable core 16. An exemplary process includes the use of a semi-solid thixotropic metal alloy material with the inserts 20, 22 between dies at a temperature above the melting point of the material of the core and below the melting point of the insert. In describing the preferred embodiment, examples will be given of the insert process in conjunction with a core melt process. It should be understood, however, that the technique is not limited to the core melt method and is applicable to other coring methods such as those using sand, salt, and steel slide cores, as well as "lost foam" or "evaporative pattern casting" cores. The technique may also be utilized in conjunction with various forms of liquid metal casting. In addition, it should be understood that although the preferred embodiment is discussed in relation to a brake caliper, the process is useful in the manufacture of a wide variety of products or parts, and the illustrated examples should not be read as limiting in any way.

FIG. 1 illustrates a core die 14 capable of casting a clad core 16 (FIGs. 6-9B) that maybe utilized in the casting of a cast metal part 15 (FIGs. 1-10). In the illustrated preferred embodiment, the cast part 15 is a single piston disc brake caliper housing. The core 16 is obtained by placing steel inserts 20, 22 into the core die 14 and injecting a shot of zinc alloy into the core die 14 to form a clad core 16. After the clad core 16 is cooled and removed from the core die 14, the part 15 is cast over the core as seen in FIGs. 6-8. The part 15 with the core 16 is then heated to a temperature such that the core 16 is melted away from the part 15 and the part 15 remains with the clad portions or inserts 20, 22 securely attached as seen in FIGs. 10A- 1OC.

Core die 14 is preferably a metal die known in the die casting industry. The die 14 of the illustrated embodiment is preferably formed from steel. However, it should be understood that the die materials will vary from application-to-application, depending upon the properties of the metal being cast. As illustrated in FIG. 1, core die 14 comprises an imprint of the internal features of the finished product 15. In the illustrated embodiment, core die 14 includes a caliper seal groove defining region 17, and two pin seal defining regions 19.

As illustrated in FIGs. 2a-2d, in accordance with the present inventive process, prefabricated inserts 20, 22 can be added to the core die 14 prior to core casting to form clad regions of the core 16 that will be incorporated into the finished part. As noted previously, the inserts 20, 22 can be utilized to deter the detrimental effects of the heat transferred to the core 16 during the metal part casting process as well as to add superior properties to strategic locations of the finished part 15. In the illustrated embodiment shown in FIG. 2a- 2d, the inserts 20, 22 include a stainless steel ring 20 that defines a seal grove 26 and two steel mounting bushings 22 that each defines a pin seal for a cast aluminum brake housing 15. As illustrated by FIG. 2b, the ring 20 also defines an internal boot groove 28, and a cylinder bore 24 of the caliper housing.

Preferred inserts 20, 22 may vary in thickness from about 0.005 to 0.125 inches, however, thicker inserts are possible if they are machined. A particularly preferred thickness is about 0.030 inches. It should be understood that although the illustrated preferred inserts 20, 22 are described in relation to their ability to define internal portions of the part 15, the inserts may also define external surfaces of the cast part 15 as well. In accordance with the preferred process, the inserts 20, 22 will be imbedded in the final cast part 15 and will have no parting lines. The inserts 20, 22 will be smooth and precise in shape. Preferably, the inserts 20, 22 are made from a material that will contribute to quality and durability of the final cast part 15. Properties such as strength, hardness, wear resistance, precision, and other surface qualities inherent in the insert materials and treatment should be considered.

Inserts 20, 22 may be formed from sheet metal or another material using a variety of known methods. Typical methods include conventional cold stamping, drawn stamping or cutting to form the cylindrical tubing blanks followed by rolling of the groove features in a die and arbor set up. Hydro-forming or magnetic field forming, although more expensive, may be utilized to form the final shape into the inserts 20, 22. These processes can form sheet or tubing stock from a wide variety of materials and in a range of thicknesses very quickly and inexpensively. Preferred insert materials include, for example, aluminum, brass, bronze, copper, copper alloys, steel, stainless steel, tin, and plated steel. The formed inserts can be held to tolerances as closely as .001" in diameter or across measurable points in non rounded parts after being cast into the core and the part.

In the illustrated embodiment, the caliper bore 24, seal groove 26 and boot groove 28 shapes are formed into a thin stainless steel sheet metal ring 20 of 0.030 inch thickness using one of the methods disclosed above. The inside features of the inserts 20, 22 should define the exact shape of the features to be used in the final part 15. Because of the intricate features of the clad ring 20 and the undercutting required to form both the boot groove 28 and the seal groove 26 in the entire ring 20, hydro-forming or magna-forming is required to form the entire illustrated ring insert 20. As a less expensive alternative to forming the entire ring 20, only the portion of the ring below line 27 may be clad. Since the precision of the seal groove 26 is of greatest importance to the performance of the finished part 15, only the seal groove region 26 and bore 24 need to be clad. Thus by only cladding these regions, the undercutting required to form the entire ring 20 is eliminated, as is the necessity of hydro- forming or magna- forming the ring 20. The clad portion of the ring 20 below line 27 may be formed by cold stamping or other less expensive methods. The remaining less critical regions, such as the boot groove 28, can be formed by the core 16. Thus, depending on the criticality of the particular features of the finished product, as well as the orientation of these features within the cast part, the known methods of forming the clad part can be varied. The inserts 20, 22 could be heat treated or coated in wide variety of known ways to augment the properties of the final product or to aid in part processing. The desired surface or heat treatment may be applied to the raw sheet stock and remain present after forming, such as is the case with tin plated steel stock. For example, rings 20 made of aluminum can be hard coat anodized or anodized for corrosion and wear resistance after forming without affecting the precision shape.

Following the manufacture of the inserts 20, 22, the inserts 20, 22 are placed within the core die 14. FIG. 3 illustrates the stainless steel bushing 22 and ring 20 inserts within the die 14 that will be used to make the zinc core 16 utilized in casting the finished product 15. As noted earlier, in the preferred embodiment, zinc core casting is described, however, other materials and methods could be used such as sand core tooling or salt core tooling. The inserts 20, 22 offer a close fit to the zinc core tooling (typically to within .001" or .002") once the tooling is closed.

As illustrated in FIGS. 1 and 3, the core die 14 has identical cavities corresponding to the inserts 20, 22 to augment casting. Although only one half of the die 14 is illustrated, it is understood that core dies will typically comprise two halves configured to close upon themselves and define the external features of the core 16. In the formation of the core 16, the core die 14 closes, trapping the inserts 20, 22 in the cavity with nearly no clearance to the die steel. The close fit assures the surface of the inserts 20, 22 will remain exposed after the casting of the core 16 within it is complete and will be held to a nearly perfect roundness.

In the preferred embodiment, zinc is cast into the core die 14 and within the inserts 20, 22 with a preferred pressure of 5000psi. This pressure is seen on the inner surface of the stainless steel cladding inserts 20, 22 and causes the inserts 20, 22 to expand into the zinc core die 14 very tightly, thereby preventing zinc from covering the outside surface of the inserts 20, 22 after the core 16 is cast. The zinc cools in the die 14 and solidifies, shrinking slightly as it cools and allowing the inserts 20, 22 to relax. The resulting core 16 is solid and has the bushing 22 and ring 20 inserts integrally cast and exposed on the outer core surface only.

It is understood that the core 16 may require a coating to protect the zinc or cast aluminum in the casting and the melt out steps. The need for a core coating is dictated by the part design and the process parameters. The inserts 20, 22 typically have no need for a protective coating. With the stainless steel inserts 20, 22 used in the illustrated preferred embodiment, no coating is necessary.

After any coating, the zinc core 16 with its cast-in stainless steel inserts 20, 22 may receive threaded fittings to assure that there will be no need for machining after casting. This is an optional process and is described here only for exemplary reasons. Once the clad core 16 is formed, the core 16 is removed from the core die 14. FIG. 5 illustrates the cast core 16 with the integral inserts 20, 22.

Turning now to FIG. 6, the clad core 16 with the inserts 20, 22 is placed into the semi-solid aluminum part casting die 40 and the die 40 is shut. As noted above, although only one half of the die 40 is illustrated, typically a die with two halves will be utilized. As illustrated in FIG. 7, the semi-solid aluminum shot is made into the die cavity and over the core 16. Once the aluminum part casting die 40 is filled, the pressure in the cavities is raised to about 10,000 to 15,000 psi to assure all the fine detail in the cores and cavities are filled fully. Because shrinkage occurs as the shot cools, this pressure is held to allow make up metal to compensate for part shrinkage in the massive sections. As the aluminum cools, the energy from the aluminum is largely absorbed by the highly thermally conductive and massive core 16. The core 16 has ample mass to insure that this energy is not adequate to cause core melting in the aggregate. In addition, with the inventive stainless steel inserts 20, 22, the finest details of the core that would naturally be the most susceptible to thermal damage in the casting and heat transfer process are protected by the cladding material that cannot be damaged by the available energy or temperature of the shot metal. After the shot is completed, the aluminum caliper housing 15 cools and solidifies. While cooling, the housing 15 imparts very large compressive forces on the core 16 and its clad inserts 20, 22, causing excellent mating of the inserts 20, 22 with great retention forces and integral sealing of the inserts 20, 22. This sealing prevents any hydraulic leakage potential around for example, the ring insert 20. FIG. 8 illustrates the clad core in the caliper casting tool.

The composite hydraulic caliper disc brake housing 15 (core 16, inserts 20, and cast aluminum part 14) illustrated in FIGS. 9 A and 9B is removed from the part casting die 40, trimmed, and placed in a holding fixture and submerged in a liquid bath at roughly 850° F for zinc core removal as described, e.g., in the above-mentioned Chipless Metals LLC patents. This bath heats the part 15 and the core 16 to allow the melt out of the core 16 while not affecting the aluminum cast part 15 or the inserts 20, 22 since only the zinc core 16 can melt at this relatively low temperature. This bath melts and washes the zinc and its remnants out of and off of the final part 15.

As illustrated in Figs. lOA-C, the stainless steel inserts 20, 22 remain imbedded tightly in the cast aluminum part 15 after core removal. The part 15 is then cooled, is blast cleaned, if desired, the fitting inserts removed, and the part is washed. In some cases the part may be subject to an additional heat treatment step. Oftentimes this heat treatment can be avoided since the properties of the inserts 20, 22 are superior to the casting and are at the critical part interfaces for wear and durability. The part is cleaned and is now ready to use. Since no machining is required, there are no burrs to remove or machining fluids to clean off the part. No impregnation is required since no porosity is uncovered by machining. All of these saved steps reduce process costs and reduce scrap and salvage costs.

The clad inserts 20, 22 formed in this process are naturally as smooth as when they were formed, present no lines in the cast part as would occur if the core 16 formed the corresponding areas or if those areas were machined into the cast part, and are tightly held by their geometry and natural shrink forces imparted by the casting resulting in leak free tightness. For these reasons, the part 15 can have better finishes in the seal surfaces than typically obtained in a machined part. The surfaces also exhibit better wear life than machined or cast surfaces and superiority in holding pressure since they are tightly held. Since no machining takes place there is not the possibility to open up any porosity that may be hidden beneath the surface of the cast aluminum. In the illustrated embodiment, the cleaned aluminum disc brake caliper housing with its stainless steel clad bore and grooves is ready for assembly with no expensive machining required and no scrap generated by the cutting of surfaces that can expose internal porosity. Less aluminum is consumed since the part is cast at 100% net shape. This can contribute to a 15% to 30% reduction in material cost. This process significantly improves consistency and quality of brake calipers while substantially reducing cost over cast and machined calipers. Similar benefits can be found with other parts such as, for example, steering gear housings, transmission parts, water pump housings, air conditioning scrolls, motorcycle fork sliders, suspension parts, and engine parts.

As noted above, this clad insert can be used externally as well as internally on the core to define a variety of complex surfaces. Also as noted above, the invention is not limited to a melt away core casting process but, instead, is usable with virtually any process in which a part is cast about a core. For instance, the described precision casting process can be performed using an evaporative pattern casting process, often known as a "lost foam" casting process. The evaporative cladding pattern precision casting process can be further enhanced by the use of a reinforcing ring or other reinforcing structure. The reinforcing structure helps to maintain the nonstructural foam utilized in a desired configuration during the cladding process. The reinforcing structure may be formed in a plurality of parts.

Preferably, the plurality of parts lock together to define a structure such as a ring. Once the reinforcing structure has been assembled, the cladding is then tightly pressed over the reinforcing structure. The structure is then inserted in one of two halves of the foam before the other half is glued onto the foam over the insert. The foam insert is then coated with a ceramic coating. After the coating has been completely dried, the resulting pattern is attached to a downsprue to form a cluster which is placed on few inches of unbonded sand in a vented container, usually referred to as a flask. More unbonded sand is then added to the flask until the pattern is entirely imbedded in sand. The flask is vibrated during the filling cycle to compact the sand fill the voids around the insert with sufficient density and stiffness resist molten metal and gas pressures during pouring. When the vibration is stopped the sand grains lock together forming a very dense mold. A molten metal, typically aluminum, is then poured into the downsprue and vaporizes the foam. The molten metal displaces the foam with precise dimensional accuracy. Gases produced due to the vaporization of the foam pass through the coating layer, through the compacted sand, and through vents located on the flask walls. Once the metal shot has been has cooled, the locked reinforcing structure is removed to allow the reinforcing structure to be reused. Many changes or modifications may be made within the scope of the invention without departing from the spirit thereof. The scope of some of these changes are discussed above. The scope of other changes will become apparent from the appended claims.

Claims

I claim:

1. A precision casting process comprising:

(A) placing a core having at least one metal insert in a die while retaining a die cavity between said core and an inner surface of said die;

(B) filling said die cavity with a shot of a liquid or semi-solid metal;

(C) allowing said shot to cool and solidify, thereby forming a cast part; and

(D) removing said core from said cast part such that said insert remains attached to said cast part.

2. The process as defined in claim 1 , further comprising the steps of placing a metal insert in a core die and casting said core within said insert.

3. The process as defined in claim 1, wherein said core is formed from a metal having a lower melting point than that of said cast part.

4. The process as defined in claim 3, wherein said cast part is formed from aluminum or an aluminum alloy and the core is formed from zinc or a zinc alloy.

5. The process as defined in claim 1, wherein said insert is comprised of a metal selected from the group consisting of aluminum, stainless steel, titanium, brass, bronze, copper, copper alloys and carbon steel.

6. The process as defined in claim 1 , wherein said insert is coated, plated and/or heat treated to enhance its surface properties

7. The process as defined in claim 1, wherein said core is a salt core.

8. The process as defined in claim 1, wherein said core is a sand core.

9. The process as defined in claim 1, wherein said core is a steel slide core.

10. The process as defined in claim 1, wherein said insert is placed internally into two or more glued foam patterns.

11. The process of claim 10, further comprising placing a removeable reinforcing structure on an inner surface of said insert to accurately maintain its precision shape during the casting process.

12. The process as defined in claim 1, wherein said cast part is a brake caliper housing. 13. The process as defined in claim 1, wherein said insert has a thickness of between .005 and .125 inches.

14. The process as defined in claim 13, wherein said insert has a thickness of about .030 inches.

15. The process as defined in claim 1, wherein said insert defines an internal portion of said cast part.

16. The process as defined in claim 1, wherein said insert defines an external surface of said cast part.

18. The process as defined in claim 1 , wherein said insert is formed from of a tin plated steel stock.

19. The process as defined in claim 1, wherein said insert is formed from a hard coat anodized aluminum for corrosion and wear resistance.

20. The process as defined in claim 3, wherein zinc is cast into said core die and within said insert at a pressure of about 5000psi.

21. The process as defined in claim 2, further comprising the step of placing threaded fittings on said insert after casting said core within said insert.

22. The process as defined in claim 1, wherein, during the casting process, the pressure in said die cavity is raised to between 10,000 and 15,000 psi.

23. The process as defined in claim 4, wherein the removing step comprises placing said cast part in a liquid bath.

24. The process as defined in claim 23, wherein the liquid bath has a temperature of about 850° F.

25. A process of forming a casting core for a precision casting process comprising placing a metal insert in a core die and casting a core within said insert, wherein said insert has different properties than said core.

26. The process as defined in claim 25, wherein said core is formed from a metal having a lower melting point than that of said insert.

27. The process as defined in claim 25, wherein said core is formed from zinc or a zinc alloy.

28. The process as defined in claim 25, wherein said insert is comprised of a metal selected from the group consisting: of aluminum, stainless steel, titanium, brass, bronze, copper, copper alloys and carbon steel. 29. The process as defined in claim 25, wherein said insert is coated, plated and/or heat treated to enhance its surface properties

30. The process as defined in claim 25, wherein said core is a salt core.

31. The process as defined in claim 25, wherein said core is a sand core.

32. The process as defined in claim 25, wherein said core is a steel slide core.

33. The process as defined in claim 25, wherein said insert is placed within a lost foam pattern.

34. The process as defined in claim 25, further comprising placing a removeable reinforcing structure on an inner surface of said insert.

35. The process as defined in claim 25, wherein said insert has a thickness of between .005 and .125 inches.

36. The process as defined in claim 25, wherein said insert defines an internal portion of said cast part.

37. The process as defined in claim 25, wherein said insert defines an external surface of said cast part.

38. The process as defined in claim 25, wherein said insert is formed from a tin plated steel stock.

39. The process as defined in claim 25, wherein said insert is formed from a hard coat anodized aluminum for corrosion and wear resistance.

40. The process as defined in claim 25, wherein zinc is cast into said core die and within said inserts at a pressure of about 5000psi.

41. A core for a precision casting process comprising an insert of a different material than said core.

42. The core of claim 41 , wherein said core is formed from a metal having a lower melting point than that of said insert.

43. The core of claim 41, wherein said core is formed from zinc or a zinc alloy.

44. The core of claim 41 , wherein said insert is comprised of a metal selected from the group consisting of: aluminum, stainless steel, titanium, brass, bronze, copper, copper alloys and carbon steel.

45. The core of claim 41, wherein said insert has a thickness of between .005 and .125 inches.

46. The core of claim 45, wherein said core has a thickness of about .030 inches. 47. The core of claim 41 , wherein said insert defines an internal portion of said cast part.

48. A cast metal part formed by the process of claim 1.

49. A cast metal part comprising: a casting formed from a first material; and at least one insert imbedded in said casting and being formed of a second material, said insert being imbedded in said casting by casting said first material around said insert and core containing said insert, then removing said core from said cast metal part.