Patent Application
20240316632
The present invention relates to machinery and specific attributes recycling particulate metal by deformation at high temperature in a vacuum environment, and more specifically to containers to contain the particulate metal material and vacuum environment and a method of coupling with a machine architecture.
Various forms of melting and casting under a vacuum are significant steps in the recycling of numerous useful metals such as nickel alloys, titanium, and some iron-based metals. These processes are very energy intensive, costly, and typically require numerous subsequent hot deformation steps to produce desired geometric forms and wrought microstructures commonly desired in wire, bar, and billet.
Solid-state deformation (SSD) methods represent a potential means of producing these same products at or close to finished form with less energy required given the absence of melting and size reduction to refine cast microstructures. In these methods particulate metals, such as chips, turnings, granules, or flakes, are deformed below the melting temperature to consolidate the mass into an effectively fully dense material with wrought microstructure. Of these various methods, those which imparted significant plastic strain, such as hot extrusion based processes, prove more effective at producing homogeneous wrought microstructures from course or mixed microstructure starting material as would be expected from chips and turnings.
In order for the metals to bond together under compression, oxides cannot be present on the outer surfaces of the particles. These form when heating occurs while exposed to gases or atmosphere. The dominant method of protecting these materials is to seal them within a canister
Alternative methods have been sought to replace this multiple step process of casting and hot deformation reducing, for raw mill stock production. One pursuit has been around solid-state deformation (SSD) of powder or machined chips into a compaction to form a solid specimen of equivalent quality to traditionally produced mill products. Sealing material in a vacuum environment within an airtight canister while subjected to a hot deformation process is an effective method of enabling solid state consolidation of metal particulate. However, the cost of manufacturing and steps associated with removing the canister have been detrimental in the adoption of this process as a low-cost recycling method. As such the mitigation of the cost of the manufacturing of a canister and the cost to remove the canister following consolidation is a major advantage to the economics of a solid-state recycling process. Additionally, a number of process attributes also enable for a SSD processes to robustly deliver usable mill product directly from clean but unprocessed revert or scrap chips. These parameters include fully maintain vacuum environment around chips until compaction, isolation from contaminants prior to compaction, working temperature aligned with the hot working temperature of the material, and a large, imparted strain. Regarding, the introduction of atmosphere, even momentarily before consolidation, can cause oxide formation or gas entrapment between metal particles. As a result, first, incomplete inter-particulate bonding or retained voids can remain. Second, any non-gaseous contaminants that can reach the particulate material have the potential to become entrapped in the material as it consolidates and compromising quality. Third, the utilization of deformation within hot working temperature zones, as with standard metalworking processes, avoids negative material effects the compromise material properties. Forth and finally, the imparting of significant strain separates processes that can refine particles that do not have ideal microstructure instead of just consolidating a finely granulated powder as is the case for powder metallurgy processes. A recycling process should be able to accommodate a broad spectrum of particulate sizes and refine the microstructure of particulate with undesirable microstructures. These metrics are presented to clearly highlight the advantages of the present invention over the prior art in solid state deformation capable of recycling.
In prior arts U.S. Pat. Nos. 4,040,162, 3,611,546, 3,723,109, 3,824,097, 3,899,821, EP 2 785 482 B1, U.S. Pat. No. 8,303,289, US 2017/0 202 735, U.S. Pat. Nos. 7,942,308, 11,117,190, and 7,344,675 all utilized single use canisters that do not persist after the process. They also have to be separated from the material within them after the process. These prior art fail to address the foundational economic limiters for use as a recycling process.
One prior art aimed to case in the subsequent removal of the consumable canister. In patent GB 2,062,685 a canister was manufactured of a material that melts at a temperature non-detrimental to contained material so that the canister can be removed by a melting process and its material recycled. This, however, does not address the cost of manufacture of the canister and requires an additional heat treatment cycle to remove the canister.
In prior art U.S. Pat. No. 4,094,672 a method of removal of a sealed canister from a compaction utilizing an internal gas pressure to expand the canister from the consolidated material was presented. This allowed for the reuse of the manufactured canister. However, in this invention a distinct parting and removal operation is required. Additionally, the canister must initially be manufactured for use.
One prior art sought to eliminate the manufacture and removal of consumed canister by making a canister that persists unaltered through a consolidation process. In U.S. Pat. No. 4,647,426 a machined canister body and machined lower body accepts a sealing disk to enclose a material within a vacuum for consolidation and/or extrusion. While the main body of the of the canister can be reused through multiple cycles with this invention, the seal disk is still consumable and must be replaced. The extrusion also results in a discard or “butt” that represents a material loss following the extrusion, representing further material inefficiency. In addition, the machined canister has a manufacturing cost that must be amortized over its useful life, whatever that may be. In addition to the efficiency metrics, the prior art fails to maintain vacuum continuously through consolidation as the seal disk must be sheared on approach. While the art does provide a sequence within the hot deformation for removal of the consolidated material without leaving the equipment, the pushing material through a canister during extrusion or ejection poses issues at the interface. The consolidation of metal within a metallic canister is going to tend to want to stick together and be difficult to remove unless parting agents or lubricants are used. In the prescribed scenario of lubricant use the likely contamination of the compact would be expected from these materials or a difficult ejection or extrusion would be expected.
One prior art aims to eliminate the cost and losses of a canister's removal by creating a canister that is substantially matching chemistry and becomes part of the final product. In patent application US 2017/0233850 A1 titanium sponge was vacuum sealed inside a canister made of commercially pure titanium metal sheet with matching chemical composition. The canister was then deformed to yield a structure with core material that has increased density. Because the materials match chemically the removal of the canister is no longer required as with prior art, thus improving the yield. The canister is fully consumed and must be remanufactured each time. This is an improvement over other consumed canisters as it is not simply discarded but sold as part of the finished product. However, the construction costs of making the canister for each piece are appreciable and detract from the cost efficiency of the delivered bulk solid.
In the current invention the extrusion remnant of the novel indirect extrusion architecture forms the body of a canister for the next operation. This can be repeated indefinitely as the canister is reforged each cycle. The canister body remnant form a prior extrusion must be rescaled by a joining process with a lid and joining material of substantially matching chemistry that become part of the canister and compaction during compaction and extrusion. As such, all constituent metal ends up residing in the canister body or as part of the extruded material. This invention has no wasted metal material as even the extrusion discards, common in all extrusion processes, are contained within the canister body and simply reused in the next extrusion. In addition, this invention meets the goals of maintained vacuum through consolidation, avoidance of solid contamination, high level imparted strain, and imparting work within hot working zones. The details and specifics of the current invention are presented below in greater depth.
The present invention delivers on the aim of generating a fully dense or near fully dense metal solid from metal revert, turnings, chips, sponge, granules, solids, powders or mixtures thereof without the necessity for costly melting practices or granulation refinement beyond cleaning. Similar to powdered metallurgy processes it applies deformation and pressure at high temperatures within a vacuum sealed canister to yield substantially fully dense material. However, the present invention aims to address the limitations observed, particularly when working with courser starting input material such as turnings or machining chips. Specific limitations addressed are high material and manufacturing cost of consumable vacuum sealed containers and insufficient deformation to refine remnant microstructural artifacts from input material such as course or mixed microstructures, irregular shaped pieces, or minor oxide films on particulate surfaces.
The method of delivering this invention is through the implementation of a vacuum canister that bonds with the contained input fill material during consolidation but as the specialized indirect extrusion process continues to shape the contained material and finishes, a new starting canister body is geometrically re-formed. Since the method automatically regenerates a new starting canister the term autogenic canister is used. This extrusion process incorporates a sealing device, sometimes called a ring or retainer, around a solid compaction ram, sometimes called a punch or die, or an extrusion ram, sometimes also called a punch or die, with at least one extrusion orifice. Clean metal particulate is sealed under vacuum, within the repeatedly reforming canister, by a lid, sometimes called a disk or cover, of any suitable starting geometry, and is attached to the autogenic canister body by a suitable means—which is preferably a welding process. The chemistry of the canister body, lid, attachment material, and recycled metal particulate are of substantially equivalent chemistry. During compaction and extrusion all mentioned bodies metallurgically bond into one body or mass and begin extruding through the orifice of the extrusion ram. The indirect extrusion methodology does not complicate bonding to the canister, unlike the significant surface shearing of direct extrusion where a ram pushes material through a container toward an orifice on the opposite side of the container. At the maximum travel of the extrusion ram, the material remaining within the tooling matches the starting geometry of the canister body, with the exception of extrusion parting and lid addition. As a result, all material is either extruded out as finished material or formed into the canister body for the next cycle of the process. No specific manufacturing, besides the lid attachment, is required with each cycle and no material is lost with the process. Even the sealing lid and attachment material end up in either the autogenic canister body or the extrusion. Additionally, the lack of metal losses of the process, enables a thicker and more durable canister body to be used without negative economic impacts to the process. This results in a more durable canister that is less susceptible to puncture or loss of vacuum resulting from handling throughout the process.
Since canister exterior surfaces do not find their way onto extrusion surfaces and the lid is fully compacted and bonded to interior material before being extruded, common extrusion canister folding or wrinkling surface defects, that must be removed in other technologies, are avoided as well as their associated financial losses. In this embodiment, the extruded material is severed by an acceptable parting means to allow removal of extrusion and autogenic canister separately. In this embodiment, the remaining extrusion end is either sealed below the canister lid or the lid is sealed around the protruding end, depending on the desired placement of the cut. The lid affixed to re-establish the vacuum chamber can be flat, have any desirable curvature, or have constant or varying thicknesses.
The indirect extrusion architecture that results in this autogenic canister body, would use a tapered container walls, supporting solid container base, and a sealing structure around the advancing ram(s) from the front of the container. The sealing structure is an advancing carriage that contacts with the container structure and blocks material from advancing from the gap between the ram and the container, thus constricting the orifice, or multiple thereof, on the face of the ram as the only means of outflow, or extrusion, of the contained material. The sealing structure may be advanced by any suitable force supplying mechanism and held against the container by the advance mechanism or any suitable locking mechanism, during the press stroke(s). The tapered container would allow the canister to be re-inserted into the liner structure when reheated without removal of material from the outer surface to create a clearance fit, as would be required with simple cylindrical structures.
One variant of the present invention lies in the method of parting the indirect extruded material from the canister remnant after the indirect extrusion stroke. In contrast to the prior embodiment, an alternative method for severing the extruded material from the canister is to utilize a shear tool from the back or underside of the canister. It is acknowledged that this invention can be carried out either vertically or horizontally without incident, but is depicted oriented vertically for consistency. This tool pushes the extrusion upward while shearing the base material of the autogenic canister holding it to the canister. Once sheared, the extrusion can be pulled free of the canister. This practice does result in a hole in the bottom of the canister that must also be sealed along with the addition to a lid on the top of the canister.
A variant of the present invention involves the use of a lid structure with increased thickness corresponding to the orifice(s) on the main ram to increase compacting pressure immediately prior to breakthrough, or beginning of outflow of material in the extrusion.
Another variant of the prior embodiments involves the use of a solid face ram without an exit orifice to force compaction of material contained within the canister prior to the extrusion process. The solid ram may have a flat face or any desired geometric profile to sculpt the compacted particulate within the autogenic canister prior to the extrusion initiation. This compaction step occurs to the filled and sealed canister prior to extrusion. This compaction can occur within the same container structure that extrusion will occur in or it can take place in a completely separate set of tooling or press equipment. This compaction will also be done at an elevated temperature but may be at a different set point temperature that the extrusion step, which will be within the acknowledged hot work temperature zones of the material being recycled. It may also be performed during the same heating cycle as the extrusion or re-heating may be done prior to the extrusion step.
The resulting extrusion material are substantially fully dense with refined wrought microstructure and high-quality surfaces. The automatic formation of the canister body required for the recycling process avoids significant fabrication costs, removal costs, and material losses associated with the canister. Additionally, this process requires less energy than melting based recycling process, has fewer processing steps, and does not produce metal losses. As such the present invention has an environmental and economic advantage over all prior art in solid state recycling of metals.
The description in this embodiment is for illustrative purposes and is not intended to be restrictive to the scope in any way. As depicted in
The material of the autogenic canister body 20 and lid 24 is to be substantially equal chemistry to the particulate material 22 filling the canister in order to deliver a homogenous chemistry when the autogenic canister lid 24 or portions of the autogenic canister 20 pass through with the extrusion. Once filled with revert, powder, sponge, solids, or mixtures thereof, the air around the filling particulate material 22 is evacuated and a autogenic canister lid 24 is scaled on the top rim, typically through welding, in order to maintain a vacuum around the material, within the autogenic canister 20 during the heating and extrusion process. Prior partial compaction of filling particulate material 22 may be performed to increase metal content within the autogenic canister 20 so long as compaction does not partition the voids surrounding the particulate material 22 prior to gas evacuation. After partitioning into unconnected cavities, it becomes increasingly difficult to remove gases from the mixture to avoid their reaction with the metal mixture. Upon sealing the filling particulate material 22 in an entrapped vacuum, the application of heat to the material will not result in surface oxidation of entrapped the material, preserving the metal particulate's ability to metallurgically bond together and form homogeneous solids.
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In order to provide a clearer illustration of the impact, novelty, and advantages of the invention, the specifics of an application are provided. This example is not to constrict the scope of the invention and is to be considered in no way limiting.
A specific example of using a variant of the autogenic canister to create wire from cleaned 17-4 stainless steel machining chips demonstrates the unique advantages of the canister in conjunction with this unique architecture of indirect extrusion.
In this specific example the dimensions of the autogenic canister interior are 2.96 inch [75.3 mm] diameter and 5.4 inch [137 mm] deep. The exterior of the autogenic canister diameter is 4.5 inch [101.6 mm] at the top with a height of 5.65″ [143.5 mm]. This results in a thickness of the base of 0.25 inch [6.4 mm]. The outside diameter of this specific canister tapers at a 5-degree slope to a diameter of 3.51 inch [89.2 mm]. The significant taper allows an autogenic canister virtually unaltered from a prior extrusion run to be fully reinserted into the container. In traditional cylindrical containers, a clearance fit is generally required for re-insertion requiring material removal and losses. Additionally, significant is that the air gap in the prior art must be filled by the initial deformation of the can prior to extrusion. The lack of deformation to “fill” voids in the container means the can has more support and predictable deformation during the process.
In addition to the taper, the wall thickness of the canister is not required to be kept to a minimum, as in cases where the canister is consumed. The wall thickness is 0.77 inch [19.6 mm] at the top and 0.28″ [7.0 mm] at the bottom of the canister. This is appreciable in comparison to the diameter of the canister body, but since the canister is reformed repeatedly without material losses, this is no longer detrimental to the economics of the process efficiency. This thicker wall has numerous advantages including integrity during heating, resistance during handling damage, buckling resistance, and case of ejection. A loss of vacuum either during heating or during transfer to the press will result in a loss of material as air will enter the autogenic canister and form oxides on the surface of the machining chips. This oxide will remain dispersed in the material even after deformation and compromise properties. The large rim face provides for a larger than typically allowed area for weld between the autogenic canister and the lid to ensure a strong seal. This larger area also provides a larger area for the sealing ring to apply pressure and assist in securing the periphery of the lid during consolidation. The thicker wall will resist puncture by whichever handling mechanism is employed to transfer the canister to the press. The buckling, folding, or wrinkling of the exterior canister during deformation or during ejection is a common problem facing canned extrusions. Thin-walled canisters in traditional extrusion processes will buckle and be drawn through the die with the extrusion. When this happens lubricants and oxides from the exterior surface prevent the folded material from joining to the extrusion resulting in a lap or plain of un-bonded material in the extrusion. In all cases this must be removed. The geometry of the autogenic canister avoids the causes of these defects and improves the mitigation of defects seen in prior arts.
A hemispherical lid, similar to that embodied in
In this embodiment, stainless steel chips that have been cleaned, removed of oxide scale, and dried would be loaded into an autogenic canister made of 17-4 stainless steel. The autogenic canister would be of a comparable cleanliness on the inner surfaces so as not to contaminate the metal chips. No potential contaminants, such as extrusion lubricants used in prior arts, are to be present within the canister body. The entire sealed autogenic canister would then be heated in a gas furnace to between 1950° F. and 2150° F. prior to forging. The heated autogenic canister would be placed into a tapered container having an 5° inside diameter slope matching that of the autogenic canister outside diameter. A flat container base seals the bottom of the tapered container. Force is maintained between the tapered container and the container base with dedicated hydraulic cylinders. Prior to deformation, the sealing ring would be forced down against the rim of the autogenic canister until reaching a hard stop position on the top of the container. In this example dedicated hydraulic rams maintain constant force between the ring and the container. This fulfills many important aspects of the autogenic canister extrusion process. First this ensures that the canister is fully seated within the container and applies high pressure to secure the lid periphery to the autogenic canister rim. This force aids in the seal between the lid and autogenic canister so that if the weld ruptures the seal can be maintained by simple pressure against the mating faces. Additionally, this sealing rim allows for appreciable extrusion ratios in spite of the thicker walls of the autogenic canister. Without the sealing ring a gap would exist between the ram and the container approximately as wide as the thickness of the top rim of the container. In virtually all desirable extrusion ratios, or the ratio of extrusion ram cross sectional area to extruded cross sectional area (area of the extrusion orifice), the material in the liner would prefer to exit around the ram instead of through it. This is the path of least resistance and would compromise the ability to deliver a repeatable autogenic canister for further recycling operations. The use of the sealing ring blocks this outer area with very relatively tight clearance preventing material from trying to exit around the ram. This present ring also geometrically forms the shape of the rim for sealing the lid on the next cycle.
A fiberglass pad is placed on the lid of the canister for lubrication of the exiting material prior to engagement with the extrusion ram. With the sealing ring in place the extrusion ram applies 350 tons of force to consolidate prior to metal breakthrough and then extrude the contents of the autogenic canister. Fill material exits a single orifice in the center of the extrusion ram forming a wire of 0.296 inch [7.5 mm] diameter representing an extrusion ratio of 100:1. This represents a true strain of approximately 4.61 which is important to enable refinement of courser input stock such as machining chips. The exiting material is fully dense without microstructural remnants of the starting machine chips. The processing of material in the hot deformation temperature region prevents material defects common with high strain deformations. Following deformation, the extrusion ram is retracted and the extrusion material is severed with powered mechanical shears. The extrusion is pulled through the extrusion ram from the front of the extrusion press by a powered carriage on a linear drive. The tapered container and solid container base are separated and a block is placed between the base of the autogenic canister and the container base. Utilizing the dedicated hydraulic rams to press the tapered canister against the container base, with the block in place, results in the autogenic canister being ejected from the container. This canister geometry will be refilled, resealed, and used in subsequent recycling processes.
In this particular example considerable energy is saved by avoiding the casting and breakdown of much larger cast product down to the 0.296″ diameter wire through repeated working processes on open die presses and a rolling mill(s). Though this particular example illustrates how small product such as wire can be made directly, the underlying principles and benefits are scalable to much larger end products.
What has been described above are the preferred embodiment of the claimed subject matter. These are not the only embodiments of the claimed inventive. Accordingly, the claimed subject matter is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the claims herein.
The present application claims priority to, and the benefit of, U.S. Provisional Application No. 63/441,284, which was filed on Jan. 26, 2023, and is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63441284 | Jan 2023 | US |
