Patent Application
20200001353
Exemplary embodiments of the present disclosure relate generally to hollow castings and, in one embodiment, to method of producing multi-passage hollow castings.
Many castings have hollow passages that are difficult to cast. In some cases, the difficulty can arise from passages being so small or narrow that an investment casting slurry cannot be effectively applied in multiple layers with intermittent drying to allow for sufficient strength to be developed to withstand fluid flow dynamics and hydrostatic pressures of poured molten metal. On the other hand, in aluminum casting, a very fluid mold material like gypsum can be poured into intricate passages to have sufficient strength to form a “solid mold” structure. Rather than sequentially dip this material with intermittent drying, this material is poured all at once with chemical activation to dry the material to form the “solid mold” around a master wax pattern that forms the component. Once the wax is removed, aluminum is poured into the mold to allow the aluminum to solidify. Once solidified, the solid mold material is mechanically removed.
It has been observed, however, that no such processes exist for iron, nickel, cobalt base or other high temperature castings. In these or other cases, separate ceramic cores must be made (if possible), inserted into the component wax (or other material) pattern during injection and then sent through conventional investment casting sequential dip layer processes. This significantly increases manufacture lead time and cost.
According to an aspect of the disclosure, a method of fabricating a casting is provided. The method includes creating a mixture of ceramic powder and a binder, pouring the mixture around sacrificial patterns, executing a first thermal treatment to set the mixture into a solid mold without damaging the sacrificial patterns, executing a second thermal treatment to remove the sacrificial patterns without removing any of the binder from the solid mold, executing at least one of a third thermal treatment and a chemical treatment to remove a quantity of the binder to transform the solid mold into a solid breakaway mold and pouring molten metallic material into the solid breakaway mold.
In accordance with additional or alternative embodiments, the ceramic powder includes a refractory material and the binder includes a self-setting binder.
In accordance with additional or alternative embodiments, the method further includes assembling a casting pour-cup with gating to the sacrificial patterns.
In accordance with additional or alternative embodiments, the pouring includes pouring the mixture around an entirety of exposed portions of the sacrificial patterns.
In accordance with additional or alternative embodiments, the pouring includes at least one of agitation, vibration, ultrasonic pressure and suction or vacuum.
In accordance with additional or alternative embodiments, the method further includes pouring the mixture around the sacrificial patterns within a rigid container.
In accordance with additional or alternative embodiments, at least one of the third thermal treatment and the chemical treatment remove about 10% or less of the binder from the solid mold.
In accordance with additional or alternative embodiments, at least one of the third thermal treatment and the chemical treatment remove about 30% or more of the binder from the solid mold.
In accordance with additional or alternative embodiments, a temperature of the metallic material is less than a slumping temperature of the solid breakaway mold.
In accordance with additional or alternative embodiments, the method further includes allowing the molten material to cool into a metallic component within the solid breakaway mold and breaking the solid breakaway mold away from the metallic component following cooling.
According to another aspect of the disclosure, a method of fabricating a casting is provided and includes creating a mixture of ceramic powder and a binder, assembling sacrificial patterns to a casting pour-cup with gating in a rigid container, pouring the mixture into the rigid container in a single pour around an entirety of exposed portions of the sacrificial patterns, executing a first thermal treatment to set the mixture into a solid mold without thermally damaging the sacrificial patterns, executing a second thermal treatment to remove the sacrificial patterns without thermally or chemically removing any of the binder from the solid mold, executing at least one of a third thermal treatment and a chemical treatment to remove a quantity of the binder to transform the solid mold into a solid breakaway mold and pouring molten metallic material into the solid breakaway mold.
In accordance with additional or alternative embodiments, the ceramic powder includes a refractory material and the binder comprises a self-setting binder.
In accordance with additional or alternative embodiments, the pouring includes at least one of agitation, vibration, ultrasonic pressure and suction or vacuum.
In accordance with additional or alternative embodiments, at least one of the third thermal treatment and the chemical treatment remove about 10% or less of the binder from the solid mold.
In accordance with additional or alternative embodiments, at least one of the third thermal treatment and the chemical treatment remove about 30% or more of the binder from the solid mold.
In accordance with additional or alternative embodiments, a temperature of the metallic material is less than a slumping temperature of the solid breakaway mold.
In accordance with additional or alternative embodiments, the method further includes allowing the molten material material to cool into a metallic component within the solid breakaway mold and breaking the solid breakaway mold away from the metallic component following cooling.
According to yet another aspect of the disclosure, a method of fabricating a casting is provided and includes creating a mixture of refractory powder and a self-setting binder, assembling sacrificial patterns to a casting pour-cup with gating in a rigid container, pouring the mixture into the rigid container in a single pour around an entirety of exposed portions of the sacrificial patterns, executing at least one of a three-part thermal treatment and a two-part thermal treatment with a chemical treatment to set the mixture into a solid mold without thermally damaging the sacrificial patterns, to remove the sacrificial patterns without thermally or chemically removing any of the binder from the solid mold and to remove a quantity of the binder to transform the solid mold into a solid breakaway mold, pouring molten metallic material, which is coolable into a metallic component, into the solid breakaway mold and breaking the solid mold away from the metallic component.
In accordance with additional or alternative embodiments, the pouring includes at least one of agitation, vibration, ultrasonic pressure and suction or vacuum.
In accordance with additional or alternative embodiments, at least one of the third thermal treatment and the chemical treatment remove about 10% or less or 30% or more of the binder from the solid mold.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.
As will be described below, ceramic powder that is similar in composition to ceramic cores (e.g., silica, zircon, alumina, alumino-silicate, etc.) can be mixed with self-setting binders, such as urethanes and epoxies, to make very fluid ceramic mixtures. These ceramic mixtures can be poured around wax or rapid prototyping (RP) patterns to create a solid mold structure. This solid mold structure can fill and permeate small passages in order to make high temperature castings with complex internal passages relatively quickly and at relatively lower cost than if other methods were used. Vacuum and agitation could be used to assist the penetration and fill processing. The solid mold structure would be self-setting to harden when the binder hardens. The solid ceramic mold could be created in or placed in a metal flask. The wax pattern would be removed and the binder holding the ceramic particles together could then be removed chemically and/or thermally to create porosity. The amount of hardener can be increased for more porosity for crushability and permeability or decreased for improved strength. Once the solid mold is sufficiently hardened, molten metal would be poured in the mold to create a high temperature casting.
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In accordance with embodiments, openings from the gating 22 to the interior of the sacrificial patterns 20 may be about 0.5 inches wide and the viscosity of the mixture 10 should be consistent with an ability of the mixture 10 to flow through openings of this size. Of course, the openings can be decreased in size with a corresponding increase in viscosity of the mixture 10. Conversely, the openings can be increased in size as well.
The sacrificial patterns 20 of
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Benefits of the features described herein are the provision of castings that would conventionally require cores but which can be produced without cores at a more rapid rate and much lower cost that otherwise possible. The processes would not need expensive core tooling and can be used to create complex or simple molds. In particular, it should be understood that whereas normal casting processes can require multiple days of processing, the process of
The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.
While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.
