Fluid-Soluble Pattern Material for Investment Casting Process, and Methods for Using Same

Abstract

The present invention is directed to a water-soluble pattern material for an investment casting process, and methods of using same. In one illustrative embodiment, the method involves providing a master die with an interior cavity defining exterior surfaces of the water-soluble pattern, mixing granular sugar and a non-water-soluble binder material to form a pattern material, introducing the pattern material into the interior cavity of the master die, allowing the pattern material to cure within the master die to thereby define the water-soluble pattern comprised of the pattern material, and removing the water-soluble pattern from the master die. In another illustrative embodiment, the present invention is directed to a water-soluble pattern for use in investment casting processes wherein the pattern is comprised of a granular sugar and a non-water-soluble binder material.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally related to the field of investment casting processes, and, more particularly, to a fluid-soluble pattern material for an investment casting process, and methods of using same.

2. Description of the Related Art

One well known technique for casting metal parts is the investment or “lost-wax” process. Generally, in the investment casting process, a wax pattern of the ultimate article or product is created. This is typically accomplished by introducing hot or liquid wax into a master die that has a cavity formed therein that corresponds to the ultimate product. Thereafter, the wax pattern is removed from the master die and a molding media material, typically ceramic particles or refractory material mixes such as terracottas, fused silicas, zircons and the like or slurries thereof is invested around the wax pattern by successive dipping or coating steps wherein the investment material is allowed to dry between the successive coating steps. This process is continued until such time as the investment is of sufficient thickness such that it can be used in casting the ultimate part.

After the investment is created around the wax pattern, the structure is heated to a temperature such that the wax pattern melts and flows out of the investment, leaving a cavity within the investment that corresponds to the final desired product. Thereafter, a molten metal is poured or injected into the cavity and allowed to cool. The investment is then removed from the metal product. The product may thereafter be trimmed to remove excess metal material and subjected to additional machining operations, if necessary.

Although the investment casting process is well known, there are several drawbacks associated with the process. For example, the wax pattern employed in the process may change its shape and/or lose its dimensional tolerances over time due to a variety of factors, such as the relaxation of internal stresses set up within the wax pattern. Such instability makes the formation of parts requiring a high degree of dimensional accuracy problematic. This is particularly true for relatively large products where dimensional accuracy is important. Moreover, the investment casting process involves heating the wax material prior to pouring it into the master die and the process also includes a subsequent cool-down period to allow the wax to reach a solid state. The investment casting process also involves performing a heating process to melt and remove the wax pattern from the interior of the investment after the investment is formed around the wax pattern. Among other things, this generally requires that, after the wax pattern is removed, the investment must be handled with tongs or by other means or wait until the investment is cooled down to a temperature such that it can be handled by human hands. Lastly, the wax material used with investment casting processes is typically not re-useable. Disposal of this non-biodegradable wax material can also create problems.

The present invention is directed to an apparatus and methods for solving, or at least reducing the effects of, some or all of the aforementioned problems.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

The present invention is generally directed to a water-soluble or fluid-soluble pattern material for an investment casting process, and methods of using same. In one illustrative embodiment, the method comprises providing a master die with an interior cavity defining exterior surfaces of a fluid-soluble pattern, mixing a fluid-soluble material and a non-water-soluble binder material to form a pattern material, introducing the pattern material into the interior cavity of the master die, allowing the pattern material to cure within the master die to thereby define the fluid-soluble pattern comprised of the pattern material, and removing the fluid-soluble pattern from the master die.

In another illustrative embodiment, the method comprises providing a master die with an interior cavity defining exterior surfaces of a water-soluble pattern, mixing a water-soluble material and a non-water-soluble binder material to form a pattern material, introducing the pattern material into the interior cavity of the master die, allowing the pattern material to cure within the master die to thereby define the water-soluble pattern comprised of the pattern material, and removing the water-soluble pattern from the master die.

In yet another illustrative embodiment, the method comprises providing a master die with an interior cavity defining exterior surfaces of a water-soluble pattern, mixing granular sugar and a non-water-soluble binder material to form a pattern material, introducing the pattern material into the interior cavity of the master die, allowing the pattern material to cure within the master die to thereby define the fluid-soluble pattern comprised of the pattern material, and removing the fluid-soluble pattern from the master die.

In one illustrative embodiment, the device comprises a water-soluble pattern for use in investment casting comprising a mixture of a water-soluble material and a non-water-soluble binder. In another illustrative embodiment, the device comprises a water-soluble pattern for use in investment casting comprising a mixture of grannular sugar and a non-water-soluble binder. In yet another illustrative embodiment, the device comprises a fluid-soluble pattern for use in investment casting comprising a mixture of a fluid-soluble material and a non-water-soluble binder.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:

FIG. 1 is a side view of an illustrative master die that may be employed with the present invention.

FIG. 2 is a cross-sectional side view of the illustrative master die of FIG. 1 wherein a pattern material in accordance with one illustrative embodiment of the present invention is positioned therein.

FIG. 3 depicts the process described herein after a handle has been inserted into the bulk pattern material positioned in the master die.

FIG. 4 is a depiction of the pattern after it has been removed from the master die.

FIG. 5 is an enlarged, partial sectional view of the pattern shown in FIG. 4 depicting a varnish and wax coating on the pattern.

FIG. 6 is a depiction of the pattern after an investment comprised of a ceramic-based material, or other molding media is formed thereon.

FIG. 7 depicts a side view and a cross-sectional side view of the investment after the pattern described herein has been removed.

FIG. 8 is an enlarged view of the open end of the investment.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

The present invention will now be described with reference to the attached figures. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.

In general, the present invention is directed to an investment casting process, and methods of using same. After a complete reading of the present application, those skilled in the art will recognize that the present invention may be employed to form a variety of different parts or products. By way of example only, the present invention will be disclosed in the context of forming a rolling cutter for a rolling cutter drill bit that may be employed in drilling oil and gas wells. However, it should be understood that the present invention may be employed to manufacture any type of part or device. Thus, the illustrative rolling cutter product depicted herein should not be considered a limitation of the present invention.

FIG. 1 depicts a side view of an illustrative master die 10 that may be employed in connection with the present invention. The master die 10 has an opening 12 and a pattern cavity 14. The pattern cavity 14 has an interior geometry that corresponds to the exterior surface of the fluid-soluble or water-soluble pattern (not shown in FIG. 1) to be formed therein. The master die 10 may be made from a variety of different materials, e.g., aluminum. The master die 10 typically comprises a plurality of segments that are secured together using known techniques and methods. Of course, the number of segments and their shape can vary depending on the size, shape and configuration of the ultimate product.

The present invention employs novel water-soluble or fluid-soluble pattern material 16 in the investment casting process. For ease of reference, the pattern material described herein will be referred to as “water-soluble,” although it may be soluble with respect to additional fluids or liquids as well. Ultimately, the water-soluble pattern material 16 will be introduced into the cavity 14 in the master die 10. See FIG. 2. The water-soluble pattern material 16 may be comprised of a variety of materials. In general, the water-soluble pattern material 16 may comprise any water-soluble material, e.g., a granular sugar, water-soluble salts, detergents and/or soap materials, etc.

In one illustrative embodiment, the water-soluble pattern material 16 comprises granular sugar and a binder material. The granular sugar employed with the present invention is the sugar with the largest grain size that is consistent with the surface finish requirements of the ultimate part. In one illustrative embodiment, the binder material may be a two-part epoxy-type material. The present invention may be employed with any type of binder material that can perform the functions described herein. In one particularly illustrative embodiment, the binder material comprises a mixture of two resins (PEP SET I-1670 (120 grams) and PEP SET 11-2670 (100 grams)) and a hardener (PEP SET Catalyst 3501 (8 drops)). The resin and hardener material described above is commercially available from Ashland Chemical Co.

In one illustrative example, this binder material may be mixed with approximately 5 kg of grannular sugar to produce one illustrative embodiment of the water-soluble pattern material 16 described herein. The sugar and binder are mixed together to form the pattern material 16. In one illustrative example, the binder is present in the sugar at a ratio of approximately 4-5% (by weight) (220 g/5000 g=(0.044%)). The relative quantities of the binder and water-soluble material, e.g., sugar, salt, etc., may vary depending upon the particular application. In general, there are various factors that may impact the desired ratio of binder to water-soluble material in the pattern material mixture. If it is determined that the pattern to be made will need greater strength properties, due to its size, shape or the subsequent handling involved, then the ratio of binder to water-soluble material, e.g., sugar, may be increased. However, increasing the relative amounts of binder material will tend to make the pattern material 16 less soluble in water and thus require more time to ultimately remove the pattern from the investment as described more fully below. Increased concentrations of binder material may also tend to reduce the time at which the pattern material 16 begins to set, thereby reducing the time during which the pattern material 16 may be inserted into the cavity 14.

The binder and water-soluble material, e.g., sugar, salt, etc., may be mixed together by any means that is capable of thoroughly mixing the two components together. For example, a blade type mixing apparatus or blender may be employed to mix the binder and water-soluble material together. In general, due to the presence of the hardener in the binder material, the pattern will tend to harden or set over time. The initial setting time for the novel pattern material 16 described herein may vary depending upon the particular ratio of binder and the water-soluble material, e.g., sugar, salt, etc. For example, the pattern material 16 described herein may begin to initially set approximately 10-15 minutes after it has been mixed together. Thus, it may be advantageous to mix relatively small quantities of the pattern material 16 to allow sufficient time for the pattern material 16 to be inserted into the master die 10 prior to it beginning to set. For example, in casting the illustrative roller cutter depicted herein, two batches of the pattern material 16 are used to fill the master die 10.

After the binder and water-soluble material, e.g., sugar, salt, etc., are combined, the pattern material 16 is then introduced into the cavity 14 within the master die 10 through the opening 12. See FIG. 2. In one embodiment, this is accomplished by hand-packing the pattern material 16 into the master die 10. Of course, other means could be employed to introduce the pattern material 16 into the cavity 14 in the master die 10, e.g., vibratory packing means. Note that this packing process may be done at room temperature without requiring heating of the pattern material 16. This is in contrast to the practice in traditional lost-wax casting processes wherein the wax material is heated to a flowing state prior to introducing the heated wax material into the master die 10.

As indicated in FIG. 3, after the pattern material 16 is introduced into the cavity 14 in the master die 10, a handle 18 is inserted into the pattern material 16 through the opening 12 in the master die 10. The handle 18 will be used to handle the pattern after it is removed from the master die 10. Once the pattern material 16 is placed in the master die 10, it will be allowed to cure for a sufficient time such that the pattern may be removed from the master die 10 and can withstand subsequent handling. The duration of the cure process can vary depending upon the particular application, e.g., size and configuration of the pattern. In the illustrative example where the roller cutter is the desired end product, the pattern material 16 may be allowed to cure for 1-2 hours.

After the pattern material 16 is cured, the master die 10 is disassembled and the pattern 20, as depicted in FIG. 4, is removed. In one illustrative embodiment, the pattern 20 is then coated with a varnish material 21, as indicated in FIG. 5. The varnish coating may be applied by spraying, immersion or painting with a brush. The varnish is added to prevent dissolution of the pattern material during the dipping process. The thickness of this varnish coating is very thin, e.g., from <0.001″ to 0.005 or more inches, and it may not be required in all applications. The range of allowable thicknesses may vary considerably depending upon the tolerances of the final part. In one particular embodiment, the varnish is Piroxilina brand name offered by Comex, more specifically Piroxilina—50% solids.

In another illustrative embodiment, a thin coat of wax 23 may be applied on the varnish-coated pattern 20. The purpose of this wax coating is to help the molding media adhere to the pattern during dipping. The wax may be applied by spraying, immersion or painting with a brush. The resulting wax coating may have a thickness of approximately from <0.001″ to 0.010 or more inches, but may vary considerably depending upon the tolerances of the final part. In one illustrative embodiment, the wax coating comprises a solution of 30% paraffin and 70% Argueso filling wax. However, it should be understood that the varnish coating and wax coating processes described in this paragraph may not be required in all applications. That is, in some cases, one or both of these steps may be omitted.

As indicated in FIG. 6, the next step involves formation of an investment 22 around the pattern 20. The investment 22 is formed using traditional investment casting techniques. That is, in one illustrative embodiment, the pattern 20 may be repeatedly dipped into a molding media, which is typically a slurry of ceramic particles or of refractory material mixes such as terracottas, fused silicas, zircons and the like. The dipped pattern 20 is generally allowed to dry between each successive dipping. The end result is an investment 22 having a layered structure (see FIG. 8) that is positioned around the pattern 20 (not shown in FIG. 8). A plurality of layers 24 are depicted in FIG. 8. Of course, the investment 22 could be formed by other techniques, e.g., spray coating, injection molding.

After the investment 22 is formed, the fluid-soluble or water-soluble pattern 20 may be removed by contacting the pattern 20 with a fluid that is used to at least partially dissolve the pattern material 16 that constitutes the pattern 20. In one particular embodiment, the fluid may be warm or hot water, although other fluids may also be employed. In some cases, a simple garden hose may be employed to rinse out the water-soluble pattern 20 from inside the investment 22. If desired, a pressurized water source may be employed. Note that the step of removing the pattern 20 from the investment 22 is performed at room temperature. As used herein, the term “water-soluble” is only used to mean that the pattern 20 may be removed from the investment 22 through use of water to at least partially dissolve the pattern 20. The term “fluid-soluble” is used only to mean that the pattern 20 may be removed from the investment 22 through use of any fluid or liquid, including water, to at least partially dissolve the pattern 20. If desired, an insect repellant material may be added to the fluid-soluble or water-soluble material, e.g., sugar, during the process of mixing the pattern material 16 to limit the attraction of insects to the material washed out of the investment 22.

FIG. 7 is a cross-sectional view depicting the investment 22 after the pattern 20 has been removed from the investment 22. As shown therein, the investment 22 defines an interior cavity 14A and an opening 26. The interior cavity 14A of the investment 22 corresponds to the configuration of the final desired product.

After the pattern 20 is removed from the investment 22, traditional investment casting processes are employed to complete formation of the ultimate product. That is, the investment 22 is initially positioned in an autoclave and steamed for approximately two minutes. This steaming process allows the varnish and wax to abandon or exit the investment 22. Thereafter, the investment 22 is fired in an oven at approximately 1800° F. for approximately one hour. Then, molten metal is introduced into the cavity 14A in the investment 22 through the opening 26, the molten metal is allowed to cool, and the investment 22 is removed from the exterior of the metal part. Thereafter, excess metal may be trimmed from the part and the part may be subjected to additional machining operations.

The investment 22 may be insulated prior to the metal pouring step to allow selective cooling during the metal pouring process. Moreover, the investment 22 may be wrapped in a layer of refractory clay, or other refractory molding material, to provide strength to the investment 22 when a molten metal is introduced therein.

The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.

Claims

1-36. (canceled)

37. A device, comprising:

a water-soluble pattern for use in investment casting comprising a mixture of a water-soluble material and a non-water-soluble binder, the binder comprising a mixture of two resins and a hardener, wherein the pattern is encapsulated by an investment formed of ceramic particles.

38. The device of claim 37, wherein said water-soluble material is sugar.

39. The device of claim 37, wherein said water-soluble material is salt.

40. The device of claim 37, wherein said non-water-soluble binder is present in said water-soluble material at a weight ratio of approximately 4-5%.

41. (canceled)

42. The device of claim 37, wherein said water-soluble pattern is configured in the shape of a rolling cutter for a drill bit.

43. The device of claim 37, wherein said mixture is adapted to be at least partially dissolved by contact with water.

44. A device, comprising:

a water-soluble pattern for use in investment casting comprising a mixture of grannular sugar and a non-water-soluble binder, the binder comprising a mixture of two resins and a hardener, wherein the pattern is encapsulated by an investment formed of ceramic particles.

45. The device of claim 44, wherein said non-water-soluble binder is present in said gannular sugar at a weight ratio of approximately 4-5%.

46. (canceled)

47. The device of claim 44, wherein said water-soluble pattern is configured in the shape of a rolling cutter for a drill bit.

48. The device of claim 44, wherein said mixture is adapted to be at least partially dissolved by contact with water.

49. A device, comprising:

a fluid-soluble pattern for use in investment casting comprising a mixture of a fluid-soluble material and a non-water-soluble binder, the binder comprising a mixture of two resins and a hardener, wherein the pattern is encapsulated by an investment formed of ceramic particles.

50. The device of claim 49, wherein said fluid-soluble material is sugar.

51. The device of claim 49, wherein said fluid-soluble material is salt.

52. The device of claim 49, wherein said non-water-soluble binder is present in said fluid-soluble material at a weight ratio of approximately 4-5%.

53. (canceled)

54. The device of claim 49, wherein said fluid-soluble pattern is configured in the shape of a rolling cutter for a drill bit.

55. The device of claim 49, wherein said mixture is adapted to be at least partially dissolved by contact with fluid.