Insulation enclosure with a thermal mass

An example insulation enclosure includes a support structure having a top end, a bottom end, and an opening defined at the bottom end for receiving a mold within an interior of the support structure, and a thermal mass arranged at the top end of the support structure to thermally communicate with a top of the mold and resist heat flow from the top of the mold in an axial direction.

BACKGROUND

The present disclosure relates to oilfield tool manufacturing and, more particularly, to insulation enclosures that help control the thermal profile of drill bits during manufacture to prevent manufacturing defects.

Rotary drill bits are often used to drill oil and gas wells, geothermal wells, and water wells. One type of rotary drill bit is a fixed-cutter drill bit having a bit body comprising matrix and reinforcement materials, i.e., a “matrix drill bit” as referred to herein. Matrix drill bits usually include cutting elements or inserts positioned at selected locations on the exterior of the matrix bit body. Fluid flow passageways are formed within the matrix bit body to allow communication of drilling fluids from associated surface drilling equipment through a drill string or drill pipe attached to the matrix bit body. The drilling fluids lubricate the cutting elements on the matrix drill bit.

Matrix drill bits are typically manufactured by placing powder material into a mold and infiltrating the powder material with a binder material, such as a metallic alloy. The various features of the resulting matrix drill bit, such as blades, cutter pockets, and/or fluid-flow passageways, may be provided by shaping the mold cavity and/or by positioning temporary displacement material within interior portions of the mold cavity. A preformed bit blank (or steel shank) may be placed within the mold cavity to provide reinforcement for the matrix bit body and to allow attachment of the resulting matrix drill bit with a drill string. A quantity of matrix reinforcement material (typically in powder form) may then be placed within the mold cavity with a quantity of the binder material.

The mold is then placed within a furnace and the temperature of the mold is increased to a desired temperature to allow the binder (e.g., metallic alloy) to liquefy and infiltrate the matrix reinforcement material. The furnace typically maintains this desired temperature to the point that the infiltration process is deemed complete, such as when a specific location in the bit reaches a certain temperature. Once the designated process time or temperature has been reached, the mold containing the infiltrated matrix bit is removed from the furnace. As the mold is removed from the furnace, the mold begins to rapidly lose heat to its surrounding environment via heat transfer, such as radiation and/or convection in all directions, including both radially from a bit axis and axially parallel with the bit axis. Upon cooling, the infiltrated binder (e.g., metallic alloy) solidifies and incorporates the matrix reinforcement material to form a metal-matrix composite bit body and also binds the bit body to the bit blank to form the resulting matrix drill bit.

Typically, cooling begins at the periphery of the infiltrated matrix and continues inwardly, with the center of the bit body cooling at the slowest rate. Thus, even after the surfaces of the infiltrated matrix of the bit body have cooled, a pool of molten material may remain in the center of the bit body. As the molten material cools, there is a tendency for shrinkage that could result in voids forming within the bit body unless molten material is able to continuously backfill such voids. In some cases, for instance, one or more intermediate regions within the bit body may solidify prior to adjacent regions and thereby stop the flow of molten material to locations where shrinkage porosity is developing. In other cases, shrinkage porosity may result in poor metallurgical bonding at the interface between the bit blank and the molten materials, which can result in the formation of cracks within the bit body that can be difficult or impossible to inspect. When such bonding defects are present and/or detected, the drill bit is often scrapped during or following manufacturing or the lifespan of the drill bit may be dramatically reduced. If these defects are not detected and the drill bit is used in a job at a well site, the bit can fail and/or cause damage to the well including loss of rig time.

DETAILED DESCRIPTION

The present disclosure relates to oilfield tool manufacturing and, more particularly, to insulation enclosures that help control the thermal profile of drill bits during manufacture to prevent manufacturing defects.

The embodiments described herein provide an insulation enclosure that includes a thermal mass arranged at the top of the insulation enclosure that resists the net rate of heat loss from the mold and otherwise helps resist heat flow from the mold in the axial direction as it cools. In some cases, the thermal mass may be a resistive thermal mass that incorporates additional insulating materials or insulating techniques that resist heat flow and thereby retard the radiative heat flux from the top of the mold. In other cases, the thermal mass may be a passive or active heating thermal mass that emits thermal energy toward the top of the mold to alter the heat flux profile of the mold and reduce heat loss from the top of the mold. In either case, the thermal mass positioned above the mold, in conjunction with cooling below the mold via a thermal heat sink, may facilitate a more controlled cooling process for the mold and optimize the directional solidification of the molten contents within the mold along the longitudinal, or axial, direction.

FIG. 1illustrates a perspective view of an example of a fixed-cutter drill bit100that may be fabricated in accordance with the principles of the present disclosure. As illustrated, the fixed-cutter drill bit100(hereafter “the drill bit100”) may include or otherwise define a plurality of cutter blades102arranged along the circumference of a bit head104. The bit head104is connected to a shank106to form a bit body108. The shank106may be connected to the bit head104by welding, such as using laser arc welding that results in the formation of a weld110around a weld groove112. The shank106may further include or otherwise be connected to a threaded pin114, such as an American Petroleum Institute (API) drill pipe thread.

In the depicted example, the drill bit100includes five cutter blades102, in which multiple pockets or recesses116(also referred to as “sockets” and/or “receptacles”) are formed. Cutting elements118, otherwise known as inserts, may be fixedly installed within each recess116. This can be done, for example, by brazing each cutting element118into a corresponding recess116. As the drill bit100is rotated in use, the cutting elements118engage the rock and underlying earthen materials, to dig, scrape or grind away the material of the formation being penetrated.

During drilling operations, drilling fluid (commonly referred to as “mud”) can be pumped downhole through a drill string (not shown) coupled to the drill bit100at the threaded pin114. The drilling fluid circulates through and out of the drill bit100at one or more nozzles120positioned in nozzle openings122defined in the bit head104. Formed between each adjacent pair of cutter blades102are junk slots124, along which cuttings, downhole debris, formation fluids, drilling fluid, etc., may pass and circulate back to the well surface within an annulus formed between exterior portions of the drill string and the interior of the wellbore being drilled (not expressly shown).

FIGS. 2A-2Care schematic diagrams that sequentially illustrate an example method of fabricating a drill bit, such as the drill bit100ofFIG. 1, in accordance with the principles of the present disclosure. InFIG. 2A, a mold200is placed within a furnace202. While not specifically depicted inFIGS. 2A-2C, the mold200may include and otherwise contain all the necessary materials and component parts required to produce a drill bit including, but not limited to, reinforcement materials, a binder material, displacement materials, a bit blank, etc.

For some applications, two or more different types of matrix reinforcement materials or powders may be positioned in the mold200. Examples of such matrix reinforcement materials may include, but are not limited to, tungsten carbide, monotungsten carbide (WC), ditungsten carbide (W2C), macrocrystalline tungsten carbide, other metal carbides, metal borides, metal oxides, metal nitrides, natural and synthetic diamond, and polycrystalline diamond (PCD). Examples of other metal carbides may include, but are not limited to, titanium carbide and tantalum carbide, and various mixtures of such materials may also be used. Various binder (infiltration) materials that may be used include, but are not limited to, metallic alloys of copper (Cu), nickel (Ni), manganese (Mn), lead (Pb), tin (Sn), cobalt (Co) and silver (Ag). Phosphorous (P) may sometimes also be added in small quantities to reduce the melting temperature range of infiltration materials positioned in the mold200. Various mixtures of such metallic alloys may also be used as the binder material.

The temperature of the mold200and its contents are elevated within the furnace202until the binder liquefies and is able to infiltrate the matrix material. Once a specified location in the mold200reaches a certain temperature in the furnace202, or the mold200is otherwise maintained at a particular temperature within the furnace202for a predetermined amount of time, the mold200is then removed from the furnace202. Upon being removed from the furnace202, the mold200immediately begins to lose heat by radiating thermal energy to its surroundings while heat is also convected away by cold air from outside the furnace202. In some cases, as depicted inFIG. 2B, the mold200may be transported to and set down upon a thermal heat sink206. The radiative and convective heat losses from the mold200to the environment continue until an insulation enclosure208is lowered around the mold200.

The insulation enclosure208may be a rigid shell or structure used to insulate the mold200and thereby slow the cooling process. In some cases, the insulation enclosure208may include a hook210attached to a top surface thereof. The hook210may provide an attachment location, such as for a lifting member, whereby the insulation enclosure208may be grasped and/or otherwise attached to for transport. For instance, a chain or wire212may be coupled to the hook210to lift and move the insulation enclosure208, as illustrated. In other cases, a mandrel or other type of manipulator (not shown) may grasp onto the hook210to move the insulation enclosure208to a desired location.

In some embodiments, the insulation enclosure208may include an outer frame214, an inner frame216, and insulation material218positioned between the outer and inner frames214,216. In some embodiments, both the outer frame214and the inner frame216may be made of rolled steel and shaped (i.e., bent, welded, etc.) into the general shape, design, and/or configuration of the insulation enclosure208. In other embodiments, the inner frame216may be a metal wire mesh that holds the insulation material218between the outer frame214and the inner frame216. The insulation material218may be selected from a variety of insulative materials, such as those discussed below. In at least one embodiment, the insulation material218may be a ceramic fiber blanket, such as INSWOOL® or the like.

As depicted inFIG. 2C, the insulation enclosure208may enclose the mold200such that thermal energy radiating from the mold200is dramatically reduced from the top and sides of the mold200and is instead directed substantially downward and otherwise toward/into the thermal heat sink206or back towards the mold200. In the illustrated embodiment, the thermal heat sink206is a cooling plate designed to circulate a fluid (e.g., water) at a reduced temperature relative to the mold200(i.e., at or near ambient) to draw thermal energy from the mold200and into the circulating fluid, and thereby reduce the temperature of the mold200. In other embodiments, however, the thermal heat sink206may be any type of cooling device or heat exchanger configured to encourage heat transfer from the bottom220of the mold200to the thermal heat sink206. In yet other embodiments, the thermal heat sink206may be any stable or rigid surface that may support the mold200, and preferably having a high thermal capacity, such as a concrete slab or flooring.

Accordingly, once the insulation enclosure208is arranged about the mold200and the thermal heat sink206is operational, the majority of the thermal energy is transferred away from the mold200through the bottom220of the mold200and into the thermal heat sink206. This controlled cooling of the mold200and its contents (i.e., the matrix drill bit) allows a user to regulate or control the thermal profile of the mold200to a certain extent and may result in directional solidification of the molten contents of the drill bit positioned within the mold200, where axial solidification of the drill bit dominates its radial solidification. Within the mold200, the face of the drill bit (i.e., the end of the drill bit that includes the cutters) may be positioned at the bottom220of the mold200and otherwise adjacent the thermal heat sink206while the shank106(FIG. 1) may be positioned adjacent the top of the mold200. As a result, the drill bit may be cooled axially upward, from the cutters118(FIG. 1) toward the shank106(FIG. 1). Such directional solidification (from the bottom up) may prove advantageous in reducing the occurrence of voids due to shrinkage porosity, cracks at the interface between the bit blank and the molten materials, and nozzle cracks.

WhileFIG. 1depicts a fixed-cutter drill bit100andFIGS. 2A-2Cdiscuss the production of a generalized drill bit within the mold200, the principles of the present disclosure are equally applicable to any type of oilfield drill bit or cutting tool including, but not limited to, fixed-angle drill bits, roller-cone drill bits, coring drill bits, bi-center drill bits, impregnated drill bits, reamers, stabilizers, hole openers, cutters, cutting elements, and the like. Moreover, it will be appreciated that the principles of the present disclosure may further apply to fabricating other types of tools and/or components formed, at least in part, through the use of molds. For example, the teachings of the present disclosure may also be applicable, but not limited to, non-retrievable drilling components, aluminum drill bit bodies associated with casing drilling of wellbores, drill-string stabilizers, cones for roller-cone drill bits, models for forging dies used to fabricate support arms for roller-cone drill bits, arms for fixed reamers, arms for expandable reamers, internal components associated with expandable reamers, sleeves attached to an uphole end of a rotary drill bit, rotary steering tools, logging-while-drilling tools, measurement-while-drilling tools, side-wall coring tools, fishing spears, washover tools, rotors, stators and/or housings for downhole drilling motors, blades and housings for downhole turbines, and other downhole tools having complex configurations and/or asymmetric geometries associated with forming a wellbore.

According to the present disclosure, controlling the thermal profile of the mold200may be enhanced by modifying the configuration and/or design of the insulation enclosure208. More specifically, the embodiments described herein provide an insulation enclosure that includes a thermal mass arranged at the top of the insulation enclosure to resist heat flow in the axial direction above the mold200as it cools. In some embodiments, the thermal mass may be a resistive thermal mass that incorporates additional insulating materials or techniques to resist heat flow and thereby retard the heat flux emanating from the top of the mold200. In other embodiments, the thermal mass may be a passive or active heating thermal mass that emits heat or thermal energy toward the mold200from the top of the insulation enclosure, and thereby alters the heat flux profile of the mold200by reducing heat loss from the top of the mold200. In either case, the thermal mass positioned above the mold200, in conjunction with cooling below the mold via the thermal heat sink206, may facilitate a more controlled cooling process for the mold200and optimize the directional solidification of the molten contents within the mold200(e.g., a drill bit) along the longitudinal, or axial, direction. Through directional solidification, any potential defects (e.g., voids) may be formed at higher and/or more outward positions of the mold200where they can be machined off later during finishing operations.

FIG. 3illustrates a cross-sectional side view of an exemplary insulation enclosure300, according to one or more embodiments. The insulation enclosure300may be similar in some respects to the insulation enclosure208ofFIGS. 2B and 2Cand therefore may be best understood with reference thereto, where like numerals indicate like elements or components not described again. The insulation enclosure300may include a support structure306that defines or otherwise provides the general shape and configuration of the insulation enclosure300. In some embodiments, the support structure306may be an open-ended cylindrical structure having a top end302aand a bottom end302b. The bottom end302bmay be open or otherwise define an opening304configured to receive the mold200within the interior of the support structure306as the insulation enclosure300is lowered around the mold200. The top end302amay be closed and provide the hook210(or similar device) on its outer surface, as described above.

In some embodiments, as illustrated, the support structure306may include the outer frame214and the inner frame216, as generally described above. In other embodiments, however, one of the outer or inner frames214,216may be omitted from the support structure306such that the support structure306alternatively includes only one of the outer and inner frames214,216, without departing from the scope of the present disclosure.

The support structure306, including one or both of the outer and inner frames214,216, may be made of any rigid material including, but not limited to, metals, ceramics (e.g., a molded ceramic substrate), composite materials, combinations thereof, and the like. In at least one embodiment, one or both of the outer and inner frames214,216may be a metal mesh. The support structure306may exhibit any suitable horizontal cross-sectional shape that will accommodate the general shape of the mold200including, but not limited to, circular, ovular, polygonal, polygonal with rounded corners, or any hybrid thereof. In some embodiments, the support structure306may exhibit different horizontal cross-sectional shapes and/or sizes at different locations along the height of the insulation enclosure300.

In some embodiments, as illustrated, the insulation enclosure300may further include insulation material308supported by the support structure306. The insulation material308may generally extend between the top and bottom ends302a,bof the support structure306and also across the top end302a, thereby substantially surrounding or otherwise encapsulating the mold200with the insulation material308(except for the bottom end302b).

The insulation material308may be similar to the insulation material218ofFIGS. 2B and 2Cand may include, but is not limited to, ceramics (e.g., oxides, carbides, borides, nitrides, and silicides that may be crystalline, non-crystalline, or semi-crystalline), polymers, insulating metal composites, carbons, nanocomposites, foams, fluids (e.g., air), any composite thereof, or any combination thereof. The insulation material308may further include, but is not limited to, materials in the form of beads, particulates, flakes, fibers, wools, woven fabrics, bulked fabrics, sheets, bricks, stones, blocks, cast shapes, molded shapes, foams, sprayed insulation, and the like, any hybrid thereof, or any combination thereof. Accordingly, examples of suitable materials that may be used as the insulation material308may include, but are not limited to, ceramics, ceramic fibers, ceramic fabrics, ceramic wools, ceramic beads, ceramic blocks, moldable ceramics, woven ceramics, cast ceramics, fire bricks, carbon fibers, graphite blocks, shaped graphite blocks, polymer beads, polymer fibers, polymer fabrics, nanocomposites, fluids in a jacket, metal fabrics, metal foams, metal wools, metal castings, metal forgings, and the like, any composite thereof, or any combination thereof.

The insulation material308may be supported by the support structure306via various configurations of the insulation enclosure300. For instance, as depicted in the illustrated embodiment, the outer and inner frames214,216may cooperatively define a cavity310, and the cavity310may be configured to receive and otherwise house the insulation material308therein. In some embodiments, the support structure306may further include a footing312at the bottom end302bof the insulation enclosure300that extends between the outer and inner frames214,216. The footing312may serve as a support for the insulation material308, and may prove especially useful when the insulation material308includes stackable and/or individual component insulative materials, such as ceramic blocks (molded or cast), fire bricks, graphite blocks, metal foams, metal castings, and metal forgings that may be stacked atop one another within the cavity310.

In other embodiments, however, as indicated above, one of the outer and inner frames214,216may be omitted from the insulation enclosure300and the insulation material308may alternatively be supported by the footing312as extended from either the outer or inner frame214,216(depending on which remains in the configuration). In yet other embodiments, the insulation material308may alternatively be coupled directly to the outer and/or inner frames214,216using, for example, one or more mechanical fasteners (e.g., bolts, screws, pins, etc.), without departing from the scope of the disclosure.

The insulation enclosure300may further include a thermal mass314arranged at or near the top end302aof the insulation enclosure300(i.e., the support structure306). As described herein, the thermal mass314may be useful in resisting heat flow from a top316of the mold200during cooling. More particularly, the thermal mass314may help slow the cooling process of the top316of the mold200in the axial direction A and subsequently through the top end302aof the insulation enclosure300. Accordingly, arranging the thermal mass314“at or near” the top end302aof the insulation enclosure300may allow the thermal mass314to thermally communicate with the top316of the mold200.

The thermal mass314may be coupled to or arranged on the insulation enclosure300at various locations at or near the top end302aof the support structure306. In the illustrated embodiment, for instance, the thermal mass314is depicted as being positioned within the interior of the insulation enclosure300(i.e., the support structure306) and otherwise secured to an inner surface318of the support structure306. In other embodiments, however, the thermal mass314may alternatively be positioned between the outer and inner frames216,214at the top end302aof the support structure306. In yet other embodiments, the thermal mass314may be arranged on the exterior of the insulation enclosure300, such as on an exterior surface of the outer frame214(or an exterior surface of the inner frame216in the event the outer frame214is omitted), without departing from the scope of the disclosure.

In the illustrated embodiment, the thermal mass314may be secured to the inner surface318of the support structure306using one or more mechanical fasteners320(two shown), such as bolts, screws, pins, etc. In other embodiments, however, or in addition thereto, the thermal mass314may be permanently attached to the inner surface318of the support structure306by attachment processes such as welding, brazing, or diffusion bonding.

As used herein, the “inner surface318of the support structure306” may refer to an inner surface of the inner frame216, as illustrated, but may equally refer to the inner surface of the outer frame214in the event the inner frame216is omitted. Moreover, the “inner surface318of the support structure306” may also refer to horizontal as well as vertical inner surfaces of either the outer or inner frames214,216, without departing from the scope of the disclosure. For instance, while the thermal mass314is depicted inFIG. 3as being mechanically fastened to a horizontal inner surface318of the support structure306with the mechanical fasteners320, the thermal mass314may equally be mechanically fastened to a vertical or sidewall inner surface318, or a combination of both.

The thermal mass314inFIG. 3may be characterized as a “resistive thermal mass” in that the thermal mass314resists heat flow from the top316of the mold200by incorporating increased insulative capacity or properties at the top end302a. In some embodiments, this may be accomplished by using additional insulating material322in the thermal mass314to retard the heat flux from the top316of the mold200through the top end302aof the insulation enclosure300. The additional insulating material322may be the same type of insulation as the insulating material308. In some embodiments, for instance, the insulating material322may comprise a monolithic block of ceramic (e.g., alumina), steel (e.g., 316L stainless steel) or another type of metal. In other embodiments, the insulating material322may comprise multiple layers of an insulating blanket, such as a ceramic fiber blanket (e.g., INSWOOL® or the like). Alternately, the insulating material322may consist of ceramics, ceramic fibers, ceramic fabrics, ceramic wools, ceramic beads, ceramic blocks, moldable ceramics, woven ceramics, cast ceramics, fire bricks, carbon fibers, graphite blocks, shaped graphite blocks, metal fabrics, metal foams, metal wools, metal castings, any composite thereof, and any combination thereof. Furthermore, the thermal mass314may exhibit increased insulating properties by containing a fluid in an enclosure, such as a cavity or one or more tubes. Also, the thermal mass314may have a composite or hybrid structure, such as ceramic beads in a metallic frame or metallic foam in a ceramic enclosure that may be completely or partially enclosed.

Furthermore, one or more thermal properties of the insulation enclosure300may be modified or altered at or near the top end302ato further resist heat flow from the top316of the mold200in the axial direction A and subsequently through the top end302aof the insulation enclosure300. For example, an insulative coating, such as a thermal barrier coating, may be applied to one or both of the outer and inner walls at the top end302aor at least one surface of the thermal mass314. Such an insulative coating may prove advantageous in providing a thermal barrier that may help redirect thermal energy back toward the thermal mass314and/or toward the mold200. In other embodiments, or in addition thereto, the materials used for the support structure306and the insulation material308at or near the top end302amay exhibit lower thermal conductivities as opposed to the materials used for the support structure306and the insulation material308at or near the bottom end302b. At least one example of a material that exhibits low thermal conductivity is ceramic, such as a ceramic coating. However, those skilled in the art will readily recognize other materials that exhibit low thermal conductivities that may be equally effective, without departing from the scope of the disclosure. Using such lower thermally conductive materials may prove advantageous in increasing the insulating properties of the insulating can300at the top end302a.

FIG. 4illustrates a cross-sectional side view of another exemplary insulation enclosure400, according to one or more embodiments. The insulation enclosure400may be similar in some respects to the insulation enclosure300ofFIG. 3and therefore may be best understood with reference thereto, where like numerals represent like elements not described again. Similar to the insulation enclosure300ofFIG. 3, the insulation enclosure400may include the support structure306, including the outer and inner frames214,216, and the insulation material308supported on the support structure306, as generally described above. In other embodiments, however, as mentioned above, at least one of the outer and inner frames214,216may be omitted from the insulation enclosure400.

Moreover, the insulation enclosure400may also include a thermal mass402arranged at or near the top end302aof the insulation enclosure400(i.e., the support structure306) and used to resist heat flow from the top316of the mold200in the axial direction A. As with the thermal mass314ofFIG. 3, the thermal mass402may be coupled to or arranged on the insulation enclosure400at various locations at or near the top end302aof the support structure306. For instance, the thermal mass402may be positioned within the interior of the insulation enclosure400(i.e., the support structure306) and otherwise secured to the inner surface318of the support structure306, but may also be positioned between the outer and inner frames216,214at the top end302aof the support structure306, or on the exterior of the insulation enclosure400, such as on an exterior or interior surface of the outer frame214(or an exterior surface of the inner frame216in the event the outer frame214is omitted). In the illustrated embodiment, the thermal mass402is depicted as being secured to the inner surface318of the support structure306using mechanical fasteners320, but could also (or in addition thereto) be permanently attached thereto using one or more attachment processes, such as welding, brazing, or diffusion bonding.

Unlike the thermal mass314ofFIG. 3, however, the thermal mass402may be characterized as a “heating thermal mass” configured to impart thermal energy or heat404to the mold200. More particularly, instead of retarding the heat flux from the mold200, as is the case with the thermal mass314, the thermal mass402may either passively or actively provide heat404to the top316of the mold200such that its thermal profile is altered and reduces heat loss through the top316of the mold200.

One example of a passive-type heating thermal mass402is one that is preheated prior to lowering the insulation enclosure400around the mold200. Preheating the thermal mass402may prove advantageous in slowing radiative heat flux from the top316of the mold200. More specifically, once removed from the furnace202(FIG. 2A), the radiant heat flux from the mold200is proportional to the difference between its temperature raised to the fourth power and the temperature of its immediate surroundings raised to the fourth power (temperature measured in an absolute scale, such as Kelvin). The mold200may exit the furnace202at a temperature in the 1800° F. to 2500° F. range (1255K to 1644K) and immediately radiate thermal energy at a high rate to the room-temperature surroundings (approximately 293K). Once the insulation enclosure400is lowered over the mold200, thermal energy continues to radiate from the mold200at a high rate until the temperature of the insulation enclosure400is elevated to at or near the temperature of the mold200. Accordingly, preheating the thermal mass402may slow the radiative heat flux from the mold200.

In such embodiments, the thermal mass402may be made of a material that can act as a thermal reservoir406. Suitable materials for the thermal reservoir406include, but are not limited to, a monolithic block of ceramic (e.g., alumina), steel (e.g., 316L stainless steel or another type of metal), or a mass of high heat-capacity material, such as fireclay, fire bricks, stones, ceramic blocks, graphite blocks, and any combination thereof. Alternately, the thermal reservoir406may consist of ceramics, ceramic fibers, ceramic fabrics, ceramic wools, ceramic beads, ceramic blocks, moldable ceramics, woven ceramics, cast ceramics, fire bricks, carbon fibers, graphite blocks, shaped graphite blocks, metal fabrics, metal foams, metal wools, metal castings, any composite thereof, and any combination thereof. The thermal mass402may be preheated, such as within the furnace202ofFIG. 2Aor another type of furnace. In some embodiments, one or more thermal elements (not shown) may be used to preheat the thermal mass402. For instance, the thermal element(s) may be situated adjacent the thermal mass402or otherwise embedded within the thermal mass402and activated to increase the temperature of the thermal mass402. Alternately, the thermal element(s) may be temporarily placed near the thermal mass402to preheat the mass before the insulation enclosure400is lowered over the mold200. The resulting preheated thermal mass402may provide a reservoir for surplus heat404to be emitted toward the top316of the mold200once the insulation enclosure400is lowered over the mold200for cooling.

Furthermore, one or more thermal properties of the insulation enclosure400may be modified at or near the top end302ato further resist heat flow from the top316of the mold200in the axial direction A. For example, an insulative coating, such as a thermal barrier coating, may be applied to one or both of the outer and inner walls at the top end302aor at least one surface of the thermal mass402. In other embodiments, or in addition thereto, the materials used for the support structure306and the insulation material308at or near the top end302amay exhibit lower thermal conductivities as opposed to the materials used for the support structure306and the insulation material308at or near the bottom end302b.

FIG. 5illustrates a cross-sectional side view of another exemplary insulation enclosure500, according to one or more embodiments. The insulation enclosure500may be similar in some respects to the insulation enclosure400ofFIG. 4and therefore may be best understood with reference thereto, where like numerals represent like elements not described again. Similar to the insulation enclosure400ofFIG. 4, the insulation enclosure500may include the support structure306, including the outer and inner frames214,216, and the insulation material308supported on the support structure306, as generally described above.

Moreover, the insulation enclosure500may also include a thermal mass502arranged at or near the top end302aof the insulation enclosure500(i.e., the support structure306) for resisting heat flow from the top316of the mold200in the axial direction A. As with the thermal mass402ofFIG. 4, the thermal mass502may be coupled to or arranged on the insulation enclosure500at various locations at or near the top end302aof the support structure306. For instance, the thermal mass502may be positioned within the interior of the insulation enclosure500(i.e., the support structure306) and otherwise secured to the inner surface318of the support structure306. The thermal mass502may likewise be positioned between the outer and inner frames216,214at the top end302aof the support structure306or on the exterior of the insulation enclosure500, such as on an exterior surface of the outer frame214.

Similar to the thermal mass402ofFIG. 4, the thermal mass502may be characterized as a “heating thermal mass” that imparts thermal energy or heat404to the top316of the mold200. Unlike the thermal mass402, however, the thermal mass502may be an active-type heating thermal mass502capable of actively providing a source of the heat404to the top316of the mold200. More particularly, the thermal mass500may include or otherwise comprise one or more thermal elements504(one shown) in thermal communication with the top316of the mold200. In the illustrated embodiment, the thermal element504is depicted as an induction coil or heating element that extends into the interior of the insulation enclosure500, but may equally be any device or mechanism capable of imparting thermal energy (e.g., heat404) to the mold200and, more particularly, through the top316of the mold200. Suitable thermal elements504include, but are not limited to, a heating element, a heat exchanger, a radiant heater, an electric heater, an infrared heater, an induction heater (coil), a heating band, heated coils, heated fluids (flowing or static), an exothermic chemical reaction, or any combination thereof. Suitable configurations for a heating element may include, but not be limited to, coils, plates, strips, finned elements, and the like, or any combination thereof.

The thermal element504may be in thermal communication with the top316of the mold200via a variety of configurations. In the illustrated embodiment, for instance, the thermal element504is depicted as being embedded within the thermal mass502, which could be made of a material selected from the group consisting of a block of ceramic (e.g., alumina), steel (e.g., 316L stainless steel or another type of metal), a mass of high heat-capacity material, such as fireclay, fire bricks, stones, ceramic blocks, graphite blocks, and any combination thereof. Alternately, the thermal reservoir406may consist of ceramics, ceramic fibers, ceramic fabrics, ceramic wools, ceramic beads, ceramic blocks, moldable ceramics, woven ceramics, cast ceramics, fire bricks, carbon fibers, graphite blocks, shaped graphite blocks, metal fabrics, metal foams, metal wools, metal castings, any composite thereof, and any combination thereof. In other embodiments, however, the material for the thermal mass502may be omitted and the thermal element504may alternatively extend alone into the interior of the insulation enclosure300. In yet other embodiments, the thermal element504may be arranged between the outer and inner frames216,214at the top end302aof the support structure306or on the exterior of the insulation enclosure500, such as on an exterior surface of the outer frame214(or an exterior surface of the inner frame216in the event the outer frame214is omitted), without departing from the scope of the disclosure. The thermal element504may be useful in helping to facilitate the directional solidification of the molten contents of the mold200as it provides thermal energy (i.e., heat404) to the top316of the mold200, while the thermal heat sink206draws thermal energy out the bottom220of the mold200.

In one or more embodiments, the thermal element504may be selectively controlled to optimize directional solidification of the molten contents of the mold200. For example, in at least one embodiment, the thermal element504may be activated before the insulation enclosure500is lowered over the mold200to preheat the thermal mass502, and thereby provide the benefits described above with reference to the preheated thermal mass402ofFIG. 4. In other embodiments, the thermal element504may be activated once the insulation enclosure500is placed around the mold200. The thermal element504may be activated to provide heat504to the mold300for a predetermined amount of time, after which the thermal element504may be disabled or deactivated to allow the top316of the mold200to cool.

In some embodiments, one or more additional thermal elements (not shown) may be placed along the sides of the insulation enclosure500to help facilitate directional cooling of the mold200. For example, such thermal elements could be placed along the top third of the sidewalls of the insulation enclosure500and otherwise adjacent the thermal mass502and the top316of the mold200.

FIG. 6illustrates a cross-sectional side view of another exemplary insulation enclosure600, according to one or more embodiments. The insulation enclosure600may be similar in some respects to the insulation enclosure400ofFIG. 4and therefore may be best understood with reference thereto, where like numerals represent like elements not described again. Similar to the insulation enclosure400ofFIG. 4, the insulation enclosure600may include the support structure306, including the outer and inner frames214,216, and the insulation material308supported on the support structure306, as generally described above.

Moreover, the insulation enclosure600may also include a thermal mass602arranged at or near the top end302aof the insulation enclosure600(i.e., the support structure306) for resisting heat flow from the top316of the mold200in the axial direction A. The thermal mass602may be coupled to or arranged on the insulation enclosure600at various locations at or near the top end302aof the support structure306. For instance, as illustrated, the thermal mass602may be positioned within the interior of the insulation enclosure600(i.e., the support structure306) and otherwise secured to the inner surface318of the support structure306. In other embodiments, the thermal mass602could be positioned between the outer and inner frames216,214at the top end302aof the support structure306or on the exterior of the insulation enclosure600, such as on an exterior surface of the outer frame214.

Similar to the thermal mass402ofFIG. 4, the thermal mass602may be a passive-type thermal mass602configured to impart thermal energy or heat404to the top316of the mold200. More particularly, the thermal mass602may include a molten material604positioned within a vessel606situated above the top316of the mold200. In some embodiments, the molten material604may be a molten metal that is progressing through a phase change from a liquid state to a solid state. Other suitable molten materials604include, but are not limited to, a molten metal that remains molten throughout the cooling process of the mold200or a molten salt. As the molten material604cools and, therefore, proceeds through a phase change process (if applicable), latent heat involved with the phase change may be emitted from the molten material604in the form of heat404until the molten mass solidifies. As will be appreciated, the time required for the molten material604to solidify may prove advantageous in providing additional time to remove thermal energy out of the bottom220of the mold200via the thermal heat sink206, and thereby help directionally solidify the molten contents within the mold200.

In other embodiments, the vessel606may be filled with other types of materials and/or substances that serve to slow the cooling process of the mold200in the axial direction A. For example, in at least one embodiment, the vessel606may enclose a gas608and the gas608may be configured to act as an insulator for the insulation enclosure600. Suitable gases that may be sealed within the vessel606include, but are not limited to, air, argon, neon, helium, krypton, xenon, oxygen, carbon dioxide, methane, nitric oxide, nitrogen, nitrous oxide, trichlorofluoromethane (R-11), dichlorodifluoromethane (R-12), dichlorofluoromethane (R-21), difluoromonochloromethane (R-22), sulpher hexafluoride, or any combination thereof. The gas608may be used in the vessel606as an insulator. Accordingly, the thermal mass602may alternatively be characterized as a resistive thermal mass, similar to the thermal mass314ofFIG. 3.

Moreover, in some embodiments, the vessel606may include at least one connection to an exterior reservoir or source configured to heat the gas608and thereby allow the thermal mass602to act as a heating thermal mass. In this manner, the heated gas608may be used to fill the vessel606once, or the heated gas608may continuously cycle gas through the vessel606to provide a suitable thermal reservoir. In other embodiments, the gas608may be omitted from the vessel606and a vacuum may alternatively be formed within the vessel606.

In yet other embodiments, the thermal mass603may exhibit a composite or hybrid structure, where a solid material is ceramic beads positioned within the vessel606. In one embodiment, for instance, the vessel606may be a metallic frame and ceramic beads may be positioned therein. In another embodiment, the vessel606may be a ceramic enclosure and metallic foam may be positioned therein. In either case, the vessel606may be completely or partially enclosed.

In some embodiments, the thermal mass602may be preheated, such as within the furnace202ofFIG. 2Aor another type of furnace. In some embodiments, one or more thermal elements (not shown) may be used to preheat the thermal mass602. For instance, the thermal element(s) may be situated adjacent the thermal mass602or otherwise embedded within the thermal mass602and activated to increase the temperature of the thermal mass602. Alternately, the thermal element(s) may be temporarily placed near the thermal mass602to preheat the mass before the insulation enclosure600is lowered over the mold200. The resulting preheated thermal mass602may provide a reservoir for surplus heat404to be emitted toward the top316of the mold200once the insulation enclosure600is lowered over the mold200for cooling.

While the insulation enclosures300,400,500, and600described herein are described as including particular configurations, designs, and operations of the corresponding thermal masses314,402,502, and602, those skilled in the art will readily appreciate that variations in the designs of the insulation enclosures300,400,500, and600are possible, without departing from the scope of the disclosure. For example, it will be appreciated that the configurations, designs, and operations of the thermal masses314,402,502, and602disclosed herein may be combined in any combination, in keeping within the scope of this disclosure.

A. An insulation enclosure that includes a support structure having a top end, a bottom end, and an opening defined at the bottom end for receiving a mold within an interior of the support structure, and a thermal mass arranged at the top end of the support structure to thermally communicate with a top of the mold and resist heat flow from the top of the mold in an axial direction.

B. A method that includes removing a mold from a furnace, the mold having a top and a bottom, placing the mold on a thermal heat sink with the bottom adjacent the thermal heat sink, lowering an insulation enclosure around the mold, the insulation enclosure including a support structure having a top end, a bottom end, and an opening defined at the bottom end for receiving the mold within an interior of the support structure, the insulation enclosure further including a thermal mass arranged at the top end to thermally communicate with the top of the mold, and resisting heat flow from the top of the mold in an axial direction with the thermal mass.

Each of embodiments A and B may have one or more of the following additional elements in any combination: Element 1: further comprising insulation material supported by the support structure, the insulation material being selected from the group consisting of ceramics, ceramic fibers, ceramic fabrics, ceramic wools, ceramic beads, ceramic blocks, moldable ceramics, woven ceramics, cast ceramics, fire bricks, carbon fibers, graphite blocks, shaped graphite blocks, polymer beads, polymer fibers, polymer fabrics, nanocomposites, fluids in a jacket, metal fabrics, metal foams, metal wools, metal castings, metal forgings, any composite thereof, and any combination thereof. Element 2: wherein the support structure comprises an outer frame and an inner frame and the insulation material is positioned within a cavity defined between the outer and inner frames. Element 3: wherein the support structure includes at least one of an outer frame and an inner frame. Element 4: wherein the insulation enclosure further comprises an insulative coating positioned on at least one of the inner frame and the outer frame. Element 5: wherein the thermal mass is positioned between the outer and inner frames. Element 6: wherein the thermal mass is positioned within the interior of the support structure. Element 7: wherein the thermal mass is arranged on an exterior of the support structure. Element 8: wherein the thermal mass comprises an insulating material selected from the group consisting of ceramic, steel, multiple layers of an insulating blanket, ceramic fiber, ceramic fabric, ceramic wool, ceramic beads, ceramic blocks, moldable ceramic, woven ceramic, cast ceramic, fire brick, carbon fiber, graphite blocks, shaped graphite blocks, metal fabric, metal foam, metal wool, a metal casting, any composite thereof, and any combination thereof. Element 9: wherein the thermal mass is preheated and imparts thermal energy to the top of the mold, the thermal mass comprising a material selected from the group consisting of a ceramic block, a steel block, fireclay, firebrick, stone, a graphite block, ceramic fiber, ceramic fabric, ceramic wool, ceramic beads, moldable ceramic, woven ceramic, cast ceramic, carbon fiber, graphite blocks, shaped graphite blocks, metal fabric, metal foam, metal wool, a metal casting, any composite thereof, and any combination thereof. Element 10: wherein the thermal mass comprises one or more thermal elements in thermal communication with the top of the mold, the one or more thermal elements being selected from the group consisting of a heating element, a heat exchanger, a radiant heater, an electric heater, an infrared heater, an induction heater (coil), a heating band, heated coils, heated fluids (flowing or static), an exothermic chemical reaction, and any combination thereof. Element 11: wherein the one or more thermal elements is embedded within the thermal mass and the thermal mass comprises a material selected from the group consisting of a ceramic block, a steel block, fireclay, firebrick, stone, a graphite block, ceramic fiber, ceramic fabric, ceramic wool, ceramic beads, moldable ceramic, woven ceramic, cast ceramic, carbon fiber, graphite blocks, shaped graphite blocks, metal fabric, metal foam, metal wool, a metal casting, any composite thereof, and any combination thereof. Element 12: wherein the thermal mass comprises a substance positioned within a vessel situated above the top of the mold, the substance being selected from the group consisting of a molten metal, a molten salt, a gas, ceramic beads, a metallic foam, and any combination thereof. Element 13: wherein the gas is selected from the group consisting of air, argon, neon, helium, krypton, xenon, oxygen, carbon dioxide, methane, nitric oxide, nitrogen, nitrous oxide, sulpher hexafluoride, trichlorofluoromethane, dichlorodifluoromethane, dichlorofluoromethane, difluoromonochloromethane, and any combination thereof.

Element 14: further comprising insulating the mold with insulation material supported by the support structure, the insulation material being selected from the group consisting of ceramics, ceramic fibers, ceramic fabrics, ceramic wools, ceramic beads, ceramic blocks, moldable ceramics, woven ceramics, cast ceramics, fire bricks, carbon fibers, graphite blocks, shaped graphite blocks, polymer beads, polymer fibers, polymer fabrics, nanocomposites, fluids in a jacket, metal fabrics, metal foams, metal wools, metal castings, metal forgings, any composite thereof, and any combination thereof. Element 15: wherein the thermal mass comprises an insulating material and resisting the heat flow from the top of the mold in the axial direction comprises resisting the heat flow with the insulating material. Element 16: wherein resisting the heat flow from the top of the mold in the axial direction comprises preheating the thermal mass, and imparting thermal energy to the top of the mold with the thermal mass. Element 17: wherein the thermal mass comprises one or more thermal elements in thermal communication with the top of the mold and resisting the heat flow from the top of the mold in the axial direction comprises activating the one or more thermal elements, and imparting thermal energy to the top of the mold with the one or more thermal elements. Element 18: further comprising activating the one or more thermal elements for a predetermined amount of time while in thermal communication with the top of the mold. Element 19: wherein the thermal mass comprises a molten material positioned within a vessel situated above the top of the mold and resisting the heat flow from the top of the mold in the axial direction comprises imparting thermal energy in the form of latent heat to the top of the mold while the molten material transitions from a liquid state to a solid state. Element 20: wherein the thermal mass comprises a gas positioned within a vessel situated above the top of the mold and resisting the heat flow from the top of the mold in the axial direction comprises resisting the heat flow with the gas. Element 21: further comprising drawing thermal energy from the bottom of the mold with the thermal heat sink.