Shear-Assisted Extrusion Tool Components

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The current application claims the benefit of and priority under 35 U.S. C. § 119(e) to U.S. Provisional Ser. No. 63/709,231 , entitled “Shear-Assisted Extrusion Tool Components” filed Oct. 18, 2024. The disclosure of U.S. Provisional Ser. No. 63/709,231 is hereby incorporated by reference in its entirety for all purposes.

FIELD OF THE INVENTION

This disclosure generally refers to systems and methods for die tooling in shear assisted extrusion presses.

BACKGROUND

Shear assisted extrusion combines linear and rotational shear to impart severe deformation in a feedstock during an extrusion process. The deformational forces imparted by the added rotational shear result in metal extrusions with microstructural grain and intermetallic refinement and improved structural and functional properties. In addition, the deformation induced during the shear assisted extrusion process refines and disperses intermetallic compounds that are commonly found in post-consumer scrap allowing for the use of scrap materials as feedstocks for extruded materials.

Shear assisted extrusion can use metal feedstock, such as a billet, and press the feedstock against an extrusion die within the rotating head. Heat is generated by friction and deformation at the die and feedstock interface, which softens the material just enough to extrude through the rotating die. The combination of linear pressing and rotational mixing causes extreme deformation, which enables material chemistries and structures that are not possible with conventional extrusion.

SUMMARY OF THE INVENTION

Systems and methods in accordance with some embodiments of the invention are directed to die tooling in shear assisted extrusion presses.

Some embodiments include a die tooling, comprising: a die stack comprising: a baff ring comprising a front surface, wherein the front surface is configured to interface with a billet and a container of a shear assisted direct extrusion press; a mandrel on an opposite side of the front surface of the baff ring; a locking feature on the baff ring; a die cap in contact with the mandrel and is on an opposite side of the baff ring; a backer in contact with the die cap and is on an opposite of the mandrel; and a die slide interfaces with the die stack.

In some embodiments, the locking feature is a locking key or a locking flat.

In some embodiments, the baff ring is configured to at least one of: cool, lubricate the die assembly.

In some embodiments, the baff ring further comprises a cooling channel inside the baff ring, wherein the cooling channel is configured to flow a gas to cool the die tooling.

In some embodiments, the gas is a compressed gas.

In some embodiments, the gas is selected from the group consisting of: air, nitrogen, carbon dioxide, helium, and argon.

In some embodiments, the baff ring further comprises a lubrication channel on the front surface, wherein the lubrication channel is configured to flow a lubricant to reduce wear between the baff ring and the container.

In some embodiments, the lubrication channel is configured to receive a lubricant back pressure to facilitate a flow of the lubricant.

In some embodiments, the lubricant is an oil, a grease, or a gas.

In some embodiments, the baff ring transfers a torque from the billet to the baff ring via the locking feature such that the mandrel and the die cap sustain a minimum torque during a shear assisted extrusion process.

In some embodiments, the baff ring comprises a porting through the baff ring, wherein the porting has a tapered shape with a smaller diameter on the front surface.

In some embodiments, the porting has a shape selected from the group consisting of: a square, a rectangular, a circle, a triangle, and a trapezoid.

In some embodiments, the baff ring comprises: one-porting, two-porting, or four-porting, and wherein each porting has a tapered square shape.

In some embodiments, the front surface comprises at least one feature selected from the group consisting of: a ridge, a radial ridge, a dimple, a trajectory driven rib, a ripple, an indented dot, a cleated dot, a convex shape, and a concave shape.

In some embodiments, the at least one feature is located: at a center of the front surface, at a peripheral of the front surface, or across the front surface.

In some embodiments, the front surface comprises a coating selected from the group consisting of: a diamond-like carbon coating and a physical vapor deposition coating.

In some embodiments, the die stack further comprise a die ring that engages with the baff ring, wherein the die ring is positioned between the baff ring and the die slide.

In some embodiments, the die tooling comprises a material selected from the group consisting of: a steel, a carbon steel, an alloy steel, a hot-work tool steel, a cold-work steel, and a high-speed steel.

In some embodiments, the billet has a diameter greater than or equal to 7 inches.

In some embodiments, the billet comprises a metal selected from the group consisting of: aluminum, iron, copper, silicon, magnesium, manganese, zinc, chromium, nickel, titanium, and zirconium.

In some embodiments, the billet comprises an aluminum alloy selected from the group consisting of: a 3xxx series aluminum alloys, a 5xxx series aluminum alloy, a 6xxx series aluminum alloy, a 7xxx series aluminum alloy, and an 8xxx series aluminum alloy.

In some embodiments, the billet comprises a metallic material in a form selected from the group consisting of: powder, flake, scrap and solid.

Some embodiments include a die tooling, comprising: a baff ring, wherein the baff ring comprises: a front surface, wherein the front surface is configured to interface with a billet and a container of a shear assisted direct extrusion press; a cooling channel inside the baff ring, wherein the cooling channel is configured to flow a gas to cool the die assembly; and a lubrication channel on the front surface, wherein the lubrication channel is configured to flow a lubricant to reduce wear between the baff ring and the container.

Some embodiments further comprise a mandrel on an opposite side of the front surface of the baff ring; a locking feature on the baff ring; a die cap in contact with the mandrel and is on an opposite side of the baff ring; a backer in contact with the die cap and is on an opposite of the mandrel; and a die slide interfaces with the baff ring, the mandrel, the die cap, and the backer.

In some embodiments, the baff ring transfers a torque from the billet to the die ring via the locking feature such that the mandrel and the die cap sustain a minimum torque during a shear assisted extrusion process.

In some embodiments, the baff ring comprises a porting through the baff ring, wherein the porting has a tapered shape with a smaller diameter on the front surface.

In some embodiments, the porting has a shape selected from the group consisting of: a square, a rectangular, a circle, and a trapezoid.

In some embodiments, the baff ring comprises: one-porting, two porting, or four-porting, and wherein each porting has a tapered square shape.

In some embodiments, the gas is a compressed gas.

In some embodiments, the gas is selected from the group consisting of: air, nitrogen, carbon dioxide, helium, and argon.

In some embodiments, the lubrication channel is configured to receive a lubricant back pressure to facilitate a flow of the lubricant.

In some embodiments, the lubricant is an oil, a grease, or a gas.

In some embodiments, the front surface comprises at least a feature selected from the group consisting of: a ridge, a radial ridge, a dimple, a trajectory driven rib, a ripple, an indented dot, a cleated dot, a convex shape, and a concave shape.

In some embodiments, the front surface comprises a coating selected from the group consisting of: a diamond-like carbon coating and a physical vapor deposition coating.

Some embodiments further comprise a die ring that engages with the baff ring, wherein the die ring is positioned between the baff ring and the die slide.

In some embodiments, the die assembly comprises a material selected from the group consisting of: a steel, a carbon steel, an alloy steel, a hot-work tool steel, a cold-work steel, and a high-speed steel.

In some embodiments, the billet has a diameter greater than or equal to 7 inches.

In some embodiments, the billet comprises a metal selected from the group consisting of: aluminum, iron, copper, silicon, magnesium, manganese, zinc, chromium, nickel, titanium, and zirconium.

In some embodiments, the billet comprises an aluminum alloy selected from the group consisting of: a 3xxx series aluminum alloys, a 5xxx series aluminum alloy, a 6xxx series aluminum alloy, a 7xxx series aluminum alloy, and an 8xxx series aluminum alloy.

In some embodiments, the billet comprises a metallic material in a form selected from the group consisting of: powder, flake, scrap and solid.

Some embodiments include a shear assisted direct extrusion process, comprising: applying an axial and rotational movement to a billet of a shear assisted direct extrusion press; and extruding a part through a die tooling from the billet by transmitting a torque from the billet to the die tooling, wherein the die tooling comprises a die stack comprising a baff ring comprising a front surface, wherein the front surface is configured to interface with a billet and a container of a shear assisted direct extrusion press; a mandrel on an opposite side of the front surface of the baff ring; a locking feature on the baff ring; a die cap in contact with the mandrel and is on an opposite side of the baff ring; a backer in contact with the die cap and is on an opposite of the mandrel; and a die slide interfaces with the die stack.

In some embodiments, the baff ring is configured to at least one of: cool, lubricate the die tooling.

In some embodiments, the baff ring further comprises a cooling channel inside the baff ring, wherein the cooling channel if configured to flow a gas to cool the die tooling.

In some embodiments, the baff ring further comprises a lubrication channel on the front surface.

In some embodiments, the baff ring transfers the torque from the billet to the die ring via the locking feature such that the mandrel and the die cap sustain a minimum torque during the shear assisted direct extrusion process.

In some embodiments, the baff ring comprises a porting through the baff ring, wherein the porting has a tapered shape with a smaller diameter on the front surface.

In some embodiments, the porting has a shape selected from the group consisting of: a square, a rectangular, a circle, and a trapezoid.

In some embodiments, the baff ring comprises: one-porting, two porting, or four-porting, and wherein each porting has a tapered square shape.

Some embodiments further comprise flowing a gas through the cooling channel to cool the die tooling.

In some embodiments, the gas is a compressed gas.

In some embodiments, the gas is selected from the group consisting of: air, nitrogen, carbon dioxide, helium, and argon.

Some embodiments further comprise flowing a lubricant through the lubrication channel to reduce wear between the baff ring and the container.

Some embodiments further comprise applying a lubricant back pressure to the lubrication channel to facilitate a flow of the lubricant.

In some embodiments, the lubricant is an oil, a grease, or a gas.

In some embodiments, the front surface comprises at least a feature selected from the group consisting of: a ridge, a radial ridge, a dimple, a trajectory driven rib, a ripple, an indented dot, a cleated dot, a convex shape, and a concave shape.

In some embodiments, the front surface comprises a coating selected from the group consisting of: a diamond-like carbon coating and a physical vapor deposition coating.

In some embodiments, the die stack further comprise a die ring that engages with the baff ring, wherein the die ring is positioned between the baff ring and the die slide.

In some embodiments, the die tooling comprises a material selected from the group consisting of: a steel, a carbon steel, an alloy steel, a hot-work tool steel, a cold-work steel, and a high-speed steel.

In some embodiments, the billet has a diameter greater than or equal to 7 inches.

In some embodiments, the billet comprises a metal selected from the group consisting of: aluminum, iron, copper, silicon, magnesium, manganese, zinc, chromium, nickel, titanium, and zirconium.

In some embodiments, the billet comprises an aluminum alloy selected from the group consisting of: a 3xxx series aluminum alloys, a 5xxx series aluminum alloy, a 6xxx series aluminum alloy, a 7xxx series aluminum alloy, and an 8xxx series aluminum alloy.

In some embodiments, the billet comprises a metallic material in a form selected from the group consisting of: powder, flake, scrap and solid.

Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the disclosure. A further understanding of the nature and advantages of the present disclosure may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The description will be more fully understood with reference to the following figures, which are presented as embodiments of the invention and should not be construed as a complete recitation of the scope of the invention, wherein:

FIG. 1 illustrates a portion of a direct extrusion press in accordance with the prior art.

FIGS. 2A through 2C illustrate conventional die assemblies in accordance with the prior art.

FIGS. 3A and 3B illustrate material flow profile at the container and die interface in accordance with embodiments.

FIGS. 3C and 3D illustrate plastic strain maps of the die in accordance with embodiments.

FIGS. 4A through 4D illustrate a die tooling with protruding features in accordance with prior art.

FIG. 5A illustrates a die tooling in accordance with an embodiment.

FIGS. 5B and 5C illustrate die stack in accordance with embodiments.

FIG. 5D illustrates a die tooling of a different configuration in accordance with an embodiment.

FIGS. 6A through 6E illustrate locking features and the dish profile of the die tooling in accordance with embodiments.

FIGS. 7A and 7B illustrate a 2-porting baff ring in accordance with an embodiment.

FIG. 8 illustrates various surface features on the baff ring in accordance with embodiments.

FIGS. 9A through 9C illustrate a baff ring with tapered 4-porting in accordance with embodiments.

FIGS. 10A and 10B illustrate the cooling channels of the die tooling in accordance with embodiments.

FIGS. 11A through 11C illustrate the cooling channels of the die tooling in accordance with embodiments.

FIGS. 12A and 12B illustrate the lubrication channels of the die tooling in accordance with embodiments.

FIGS. 13A through 13D illustrate various die tooling structures in accordance with embodiments.

FIGS. 13E through 13H illustrate simulation of material flow through various die tooling structures in accordance with embodiments.

FIGS. 14A and 14B illustrate entry and exit of the mandrel in accordance with embodiments.

FIGS. 15A and 15B illustrate support structures for the mandrel in accordance with embodiments.

FIGS. 16A and 16B illustrate different entry and exit pocket shapes of the mandrel in accordance with embodiments.

FIGS. 17A and 17B illustrate different entry shapes of the baff ring in accordance with embodiments.

DETAILED DESCRIPTION OF THE INVENTION

It will be understood that the components of the embodiments, as generally described herein and illustrated in the appended figures, may be arranged and designed in a variety of different configurations. Thus, the following more detailed description of various embodiments, as represented in the figures, is not intended to limit the scope of the present disclosure but is merely representative of various embodiments. While various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive.

Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present invention should be or are in any single embodiment of the invention. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, discussions of the features and advantages and similar language throughout this specification may, but do not necessarily, refer to the same embodiment.

Furthermore, the described features, advantages, and characteristics of the invention may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the invention can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the invention.

Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the indicated embodiment is included in at least one embodiment. Thus, the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may but do not necessarily, all refer to the same embodiment.

The shear assisted direct extrusion presses in accordance with many embodiments produce commercial scale extrusions. The extrusion of commercial scale parts will impart higher forces (such as, but not limited to, torques) and/or cause additional wear and/or heat generation to the die tooling of the shear assisted extrusion press. In order to comply with the commercial scale extrusion press, many embodiments provide die tooling that are compatible with commercial scale extrusions. Several embodiments provide various structures for the die tooling that can transfer the high torques, reduce wear, and/or reduce overheating for commercial scale extrusions. In this disclosure, the shear assisted direct extrusion is also referred to as the direct extrusion, unless specified otherwise. In this disclosure, the die tooling is also referred to as die assemblies.

Die Tooling

Direct extrusion is a mode of operation for extrusion processes. In direct extrusion without shear assistance, the billet moves axially towards the die tooling while the container stays stationary such that the outer shell of the billet moves relative to the container as extrusion proceeds. Thus, in direct extrusion the surface of the billet is sheared at, or slides along, the container wall. Lubricant can be applied (but not necessary) between the interface of the die tooling and the billet during direct extrusion to ease the operation. Part of the extrusion load, depending on the length of the billet, is expended in overcoming the friction between the billet and the container, or in shearing the inner material from the slower-moving peripheral layer adjacent to the container wall.

Extrusion dies are essentially thick, circular steel disks containing one or more openings to create the desired profile of an extrudate. They can be constructed from steel (such as H-13 die steel) and heat-treated to withstand the pressure and heat of the billet as it is pushed through the die.

FIG. 1 illustrates a portion of an extrusion press. In the extrusion press, a container comprising a container liner can have an opening located concentrically within the container. A billet can be loaded into the opening of the container. A stem (or an extrusion stem, or a pressing stem) can be inserted into the container to drive the movement of the billet. A dummy block can be placed between the stem and the billet to transfer the torque from the moving stem to the billet. In an extrusion process, the stem and the dummy block rotate and move axially to extrude a part from the billet. In a direct extrusion process, the container rotates with the billet. The billet moves axially through the container. The container does not move axially. A die tooling comprising a die and a die backer can be loaded to an opposite end of the billet from the dummy block to shape the extrudate. The die tooling stays stationary during the extrusion process.

FIG. 2A illustrates a solid die tooling. A solid die creates a final shape that has no enclosed voids or openings, such as a rod, a beam or an angle. As such, a solid die is typically less expensive to manufacture than other die types. Producing a solid product profile may need a solid die tooling. The solid die tooling comprises a set of parts (also referred to as a die stack). This die stack can include a feeder plate, a die plate, a backer plate, and a bolster. The feeder plate controls or directs the metal flow through the die orifice. Feeders are not uncommon in solid die assemblies. The function of the feeder is mainly to direct the flow. The die plate can form the shape of the extrudate. The backer plate supports the tongue of the die to prevent collapse or distortion. The bolster supports the extrusion load transmitted from the die plate and the backer plate. During extrusion, the feeder plate is in contact with the billet and an extrudate extrudes through the die tooling and exits from the bolster.

FIG. 2B illustrates a hollow die tooling. A hollow die can produce profiles with one or more voids, such as a tube with one void or a complex profile with many detailed voids. Producing a hollow shape may need a hollow die tooling, which includes a mandrel, a die cap, and a bolster. The mandrel is located inside the die and has two or more port holes to generate the internal features of the profile and to control the flow of metal. During extrusion, the billet separates into each port and rejoins in the weld chamber before entering the bearing area. The ports are separated by webs, also known as legs, which support the core or mandrel section. Because of these extra components, a hollow die has a higher material and tooling cost and can get more expensive when more voids are included. The die cap is a multi-piece die which makes the shape. The bolster supports the extrusion load transmitted from the die cap and mandrel. Hollow dies rarely use feeders.

FIG. 2C illustrates a semi-hollow die tooling. A semi-hollow die extrudes a shape that is nearly hollow, partially enclosing a void. Similar to a hollow die, a semi-hollow die set includes a mandrel with port holes (but without cores to make a complete void) as well as a die cap and a bolster. While a solid die may also partially enclose a void, the difference is the ratio of the area of the void to the size of the gap where the tongue is connected to the main body of the die. This ratio is called the tongue ratio. For semi-hollow dies, the tongue ratio is larger than the ratio in solid dies, which creates more complexity when manufactured, and in turn higher cost. Like hollow dies, semi-hollow dies rarely use feeders.

Shear assisted extrusion processes may incorporate rotational movement or rotational components during the extrusion operation, distinguishing these methods from conventional extrusion approaches that rely solely on axial forces. Shear assisted direct extrusion represents an advanced metal forming process that combines linear extrusion forces with rotational shear forces to achieve enhanced material properties and processing capabilities. In some cases, this combination of forces may enable the processing of materials that would otherwise be unsuitable for conventional extrusion methods. The simultaneous application of axial and rotational forces during the extrusion process may result in severe plastic deformation of the feedstock material at the die interface, leading to microstructural refinement and improved mechanical properties in the final extruded product.

The integration of rotational shear forces with linear extrusion forces may provide several processing advantages over conventional extrusion methods. In some cases, the rotational component may generate frictional heating at the interface between the feedstock and the extrusion die, which may soften the material and reduce the overall force requirements for extrusion. The severe deformation induced by the combined forces may also result in grain refinement and homogenization of the material microstructure. Additionally, the shear forces may break down and redistribute intermetallic compounds that are commonly present in recycled or scrap materials, potentially enabling the use of lower-grade feedstocks to produce high-quality extruded products.

In order to achieve plastic deformation of the feedstock material at the die interface, maximum shear may need to be generated at the die interface. The rotational shear generates friction and shear at the feedstock's surface as it enters the die, locally heating and softening the metal. Higher shear at the feedstock's surface leads to more heating that creates advanced materials with refined microstructures. The die interface that interacts with the feedstock (such as the baff ring) can have various features in order to generate a maximum shear at the interface.

Due to the integration of rotational motion and axial motion of the feedstock, the flow profile of the feedstock in the container of the shear assisted direct extrusion may differ from conventional direct extrusion. The different feedstock flow profile can lead to different requirements of die structures, in particular die interface structures that interact with the feedstock, for the shear assisted direct extrusion.

FIG. 3A illustrates a feedstock flow profile for conventional direct extrusion. During conventional direct extrusion, the feedstock 301 moves axially in a stationary container 302. Maximum flow of the feedstock 301 occurs around the center of the die 303. The feedstock 301 flows through the die 303 interface (such as a baff ring) and through the mandrel to extrude a part.

FIG. 3B illustrates a feedstock flow profile for shear assisted direct extrusion. During the shear assisted direct extrusion, rotational shear force and axial force are applied to the feedstock 311. The container 312 rotates but may not move axially. This configuration may result in increased friction forces between the feedstock 311 and the container 312 walls due to the relative motion between these components during material flow. Thus, increased flow of the feedstock 311 can occur near the corners of the container 312. The center of the feedstock 311 has reduced flow compared to the conventional direct extrusion shown in FIG. 3A. Due to the change in flow profile, the die 313 interface may need different features in order to generate maximum shear to cause plastic deformation in the feedstock 311 while still allowing the feedstock 311 to flow through the mandrel to extrude a part.

The integration of shear rotation and linear extrusion forces result in higher plastic strain on the die tooling compared to conventional direct extrusion. The increased plastic strain can reform the microstructures of the feedstock and lead to extrudates with improved structures and properties. On the other hand, the increased plastic strain may lead to additional functions in the die tooling, such as stability, cooling, lubrication.

FIG. 3C illustrates a plastic strain map of a die tooling with an extrudate during a direct extrusion process. FIG. 3D illustrates a plastic strain map of a die tooling with an extrudate during a shear assisted direct extrusion process. The shear assisted direct extrusion generates higher plastic strain on the die tooling.

Protruding structures from the die face have been implemented to generate shear at the die and feedstock interface. However, the protruding structures would not allow the continued use of a billet during extrusion processes. FIG. 4A illustrates a die tooling and a shear blade of an extrusion press. FIG. 4B illustrates an enlarged view of the die tooling interface. FIG. 4C illustrates a front view of a nose cone of a die face. FIG. 4D illustrates a profile view of a nose cone of a die face. The die tooling 401 interacts with a billet 402 in a container 404. The die tooling 401 has a die face 408 with a protruding structure (a nose cone) 403 be inserted into the billet 402 and to generate shear at the billet 402 interface during extrusion. A shear plane 405 exists between the die tooling and the container 404. The nose cone 403 extends from the die face 408 beyond the shear plane 405. With the nose cone 403 protruding from the die face 408, this would not allow the use of a shear blade 407 to remove the unextruded billet at the end of an extrusion process and would not allow for continuous extrusion. In commercial use, operators of the shear extrusion press need to have the ability to generate a clean surface between billets by removing the remnant billet via a shearing operation.

The conventional die assemblies are designed for extruding parts of lab scale, where only relatively small billets with maximum dimensions of 1.5 to 2 inches are used. In comparison, scaling the conventional shear assisted extrusion process for use at commercial scale (with billets with diameters of at least 7 inches as opposed to the 1 or 2 inches at lab scale) introduces system requirements in extrusion force, torque, time scale, cost, and/or temperature that are not obtainable with the current apparatus. For example, the range of extrusion force and torque required for a press size of 1 to 2 inches, such as that demonstrated by the conventional shear assisted extrusion system, is relatively small (extrusion force less than 1.5 MN & torque less than 12000 Nm), whereas at commercial scales these requirements increase by more than an order of magnitude to about 35 MN's of extrusion force and greater than about 180000 Nm's of torque for extruding a 9 inches billet.

To extrude parts in commercial scale (such as a billet diameter of at least 7 inches), the die tooling needs improved structures in order to transfer a higher torque, reduce wear, and reduce overheating. It would be more advantageous if the die tooling has extended lifetime and/or reduced production cost for commercial use. Commercial scale shear assisted extrusion will need excessive torque transmission to the mandrel and/or the die cap of the die tooling, resulting in rotational deflection of the die tooling and geometric misalignment and leading to poor geometric tolerancing of the extrudate's cross sections. The wear between the cylindrical circumference of the bearing surfaces between the die tooling and the billet (for example at the shear plane) may increase for commercial extrusion. The conventional die tooling may pose potential interferences with the nose cone (as shown in FIGS. 4A through 4D) and press hardware, which may prevent the use of the shear blade to trim the end of billets between runs. In addition, excessive heat generation and/or overheating at the die interface due to the large shear deformation (during shear assisted extrusion) can occur during commercial size extrusions. Due to the large transmitted torque, rotation of the die may occur during commercial extrusion. Further, non-optimal coefficient of friction on the die face can result in excess heat generation or too little heat generation at the billet and die interface. The performance requirements for commercial scale extrusion may reduce the lifetime of a conventional die tooling when used for commercial extrusion (due to higher torque, wear, geometric constraint, heat, etc.) and thus increase the cost of tooling.

Many embodiments provide die assemblies suitable for commercial scale extrusion. The die assemblies can accommodate various billet sizes, such as diameters less than about 7 inches; greater than or equal to about 7 inches; or diameters greater than or equal to about 8 inches; or diameters greater than or equal to about 9 inches; or diameters greater than or equal to about 10 inches. In several embodiments, the baff ring of the die tooling implements structures and components that enable maximum shear generation at the die and billet interface. In many embodiments, the die tooling is optimized for the shear to take place at the interface between the die tooling (e.g. the baff ring surface) and the billet. Heat can be generated by friction and deformation at the interface. The shear can result in extrudates with reformed microstructures and improved structural and mechanical properties.

The die tooling in accordance with many embodiments comprises a baff ring that interfaces with the billet, a mandrel, a die cap, and a backer. The two-piece baff ring-mandrel designs in accordance with many embodiments are uncommon in conventional extrusion. Due to the rotational shear and axial force during the shear assisted direct extrusion, the baff ring and mandrel configuration aims to transfer the majority or all of the torque to the baff ring with minimum torque transferred to the mandrel so the die tooling can stay geometrically stable while producing the extrudates with desired microstructures. In conventional extrusion, it is often not necessary to consider torque and/or transmission of torque through the die face and tooling.

Some embodiments optimize the features of the baff ring surface that is in contact with the billet to generate the desired shear. These features can be in the center area of the baff ring surface; or in the peripheral area of the baff ring surface; or distributed across the baff ring surface. In several embodiments, the baff ring has surface features that do not interfere with the shear plane of the billet shearing blade. Some embodiments use surface texturing techniques (such as using structures like dimples, radial ridges, or using techniques like CNC texturing, smoothing, PVC coating, etc.) to engineer the coefficient of friction of the baff ring surface.

The conventional die assemblies are not typically cooled in the region adjacent to the front face of the die. During shear assisted direct extrusion at commercial scale, excessive heating may occur due to localized high shear at the baff ring and billet interface. The baff rings in accordance with many embodiments implement cooling channels to allow for independent cooling of the die face.

The baff ring in accordance with several embodiments have locking features and dishing designs that can enable torque transfer sufficiently and completely to the die ring. Such design ensures that there is almost no torque transmission to the mandrel and/or the die cap and results in more geometrically stable die assemblies. In some embodiments, the baff ring allows for lubrication (such as grease that can withstand high operating temperatures) to be pre-applied in grooves along the cylindrical circumference of the surfaces and a reservoir (such as channels). By application of back pressure, lubricant may be continuously applied during operation, reducing the wear on the mating surfaces of the die tooling and the rotating container. Conventionally, the die tooling design does not need to take into consideration of potential wear or reducing wear via lubrication. In many embodiments, the baff rings are designed to be easily manufactured. Baff ring can be made with certain porthole opening geometries (e.g. one version for a 1-out profile, one version for a 2-out profile) to simplify the overall design process.

In several embodiments, the die tooling can be made with various metallic materials such as (but not limited to) steel, carbon steel, alloy steel, hot-work tool steel, cold-work tool steel, and/or high-speed steel. As can be readily appreciated, any material can be used for the die tooling as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.

Die Tooling for Shear Assisted Direct Extrusion

Many embodiments are directed to die tooling structures that can generate necessary rotational shear and direct the material flow during extrusion. When the rotating billet contacts with the die, rotational shear occurs at the baff ring surface. The shear generates localized heat and imparts severe plastic deformation. While the billet is pushed axially through the die tooling, the die tooling stays stationary during shear assisted extrusion. The die tooling includes support structures such as a die ring and a die slide to keep the die stack still. The billet can be pushed through the die stack to extrude a part with desired geometry. The die ring and the die slide provide structural support for the die stack and keep it still during extrusion.

FIG. 5A illustrates a die tooling. The die tooling 500 comprises a die stack 510, a die ring 505, and a die slide 506. The die ring 505 and the die slide 506 support the die stack 510. The die slide 506 and the die ring 505 have flats 507 to keep the die ring 505 from rotating during the extrusion process so the shear can occur at the baff ring surface. The die stack 510 can be aligned concentrically with the container and the billet. The alignment is important and the die ring 505 and the die slide 506 ensure the alignment during extrusion. The die tooling can be made with various metallic materials such as (but not limited to) steel, carbon steel, alloy steel, hot-work tool steel, cold-work tool steel, and/or high-speed steel.

FIG. 5B illustrates an assembled die stack. The die stack 510 comprises a baff ring 501, a mandrel 502, a die cap 503, and a backer 504. The baff ring 501, the mandrel 502, the die cap 503, and the backer 504 align concentrically. The back side of the baff ring 501 (the opposite side of the baff ring surface) interfaces with the mandrel 502. The die cap 503 is positioned between the mandrel 502 and the backer 504. The backer 504 forms the back side of the die stack 510.

FIG. 5C illustrates exploded views of the baff ring 501, the mandrel 502, the die cap 503, and the backer 504. The baff ring surface 508 interfaces with the billet. Surface structures on the baff ring surface 505 contribute to maximizing the shear at the interface to deform the material microstructure. The billet flows through the openings of the baff ring 501, and through the mandrel 502, the die cap 503, and the backer 504 that form the inside shape (such as hollow and/or multi-celled shape) of the extrudates. As can be readily appreciated, the surface features of the baff ring, the opening structures of the mandrel and the die cap shown in FIGS. 5A through 5C are exemplary. Any other features can be used as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.

FIG. 5D illustrates a die tooling without a die ring. The die tooling includes a die stack 550 and a die slide. The baff ring 552 of the die stack engages with the die slide directly. The die stack does not sit inside a die ring. The die stack 550 includes the baff ring 552, the mandrel 554, the die cap, and the backer.

The die tooling implements various locking features to keep the baff ring still during extrusion. In some embodiments, torque keys are positioned between the baff ring and the die ring to lock the die tooling in place when the large torque is transmitted from the billet to the die tooling. In some embodiments, locking flats are positioned on the baff ring and the die ring such that the baff ring can slide into the die ring and the locking flats can keep the die tooling in place.

FIG. 6A illustrates a cross-section view of the die tooling. A pair of locking keys 512 interface with the baff ring 501, the mandrel 502, and the die ring 505. The locking keys 512 lock the baff ring 501 and the die ring 505 together during extrusion so shear can be generated at the baff ring surface 508.

The baff ring 501 can have a dished profile 514 in the exit of the baff ring 501. The dished profile 514 can help take pressure off the mandrel 502. During extrusion, the baff ring 501 can transfer the torque from the billet to the die ring 505 via the locking keys 512. In this way, the mandrel 502 and the die cap 503 do not rotate and receive minimum or no torque. The die tooling 500 can prevent or minimize the rotation of the mandrel 502 with the die cap 503. In other words, the torque is transferred from the billet to the baff ring 501, from the baff ring 501 to the die ring 505, from the die ring 505 to the die slide 506. The locking keys 512 and the dished profile 514 enable torque shedding.

FIG. 6B illustrates a top view of the locking features. The locking keys 512, interfacing the die ring 505 and the baff ring 501, are positioned about 180 degrees apart from each other. The locking keys 512 can reduce manufacturing costs by reducing the number of machining parts on the and. Although the locking keys 512 are positioned across the baff ring as shown in FIG. 6B, the locking keys 512 can be positioned at any other location as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.

FIG. 6C illustrates a cross-section view of the locking features. The locking keys 512 can be inserted and fitted into the die ring 505 and the baff ring 501.

FIG. 6D illustrates a dished profile of the baff ring. The dished profile 514 is positioned at the exit of the baff ring 501, facing the mandrel 502. The dished profile 514 can have a range of height. Examples of the height include (but are not limited to) greater than or equal to about 0.03 inches.

FIG. 6E illustrates locking flats that lock the baff ring and the die ring in place. The locking flats 513 can be machined in the baff ring 501 and the die ring 505 respectively. When inserting the baff ring 501 into the die ring 505, the locking flats 513 mate together and prevent sliding or rotating between the baff ring 501 and the die ring 505. The baff ring 501 can have two locking flats 513 with each of them positioned about 180 degrees apart. The die ring 505 can have two locking flats 513 that can lock with the ones on the baff ring 501.

The baff ring in accordance with several embodiments can have various geometries, surface features, and/or surface finishes to generate the desired shear. The baff ring can have a number of port openings to shape the material flow to the mandrel. In some embodiments, the baff ring may not have any port openings. The structures of the baff ring can affect the mandrel, for example, the baff ring may reduce the face pressure on the mandrel during extrusion. The baff ring can have cooling channel to cool the front face of the baff ring due to the heat generated by the shear.

During extrusion, the baff ring transports the material through the porting(s). The mandrel can divide the material and shape the geometries of the part being extruded. The die cap closes the mandrel to extrude the part. The baff ring may limit the bulk geometry of the extrudate, but using this process, the baff ring can be used for extruding parts of different geometries.

FIGS. 7A and 7B illustrate the front side and the back side of the baff ring respectively in accordance with an embodiment. The front side (shown in FIG. 7A) interfaces with the billet. The back side (shown in FIG. 7B) interfaces with the mandrel. The baff ring 501 has two portings 516.

In several embodiments, the baff ring incorporates surface features to generate shear. The features can be on the front face of the baff ring that interfaces with the billet. The features can be in the center of the front face, or in the peripheral of the front face, or across the front face. The center of the baff ring front face has lower rotational movement compared to the peripheral areas. The surface features should be able to generate maximum shear while allowing the material to flow into the mandrel. In many embodiments, the baff ring surface can be engineered to have various functions such as (but not limited to) increasing co-efficient of friction, or reducing co-efficient of friction, or promoting tortuosity of flow to the billet in the (plasticized) shear extrusion zone of the process. To increase the co-efficient of friction, some embodiments implement surface texturing of the front surface of the baff ring. Surface texturing can be done via a computer numerical control (CNC) process or a laser surface treatment. To decrease the co-efficient of friction, some embodiments implement processes such as smoothing or polishing, or coating. Coating can include diamond-like carbon (DLC) coating or physical vapor deposition (PVD) coating. DLC coating can be used to reduce adhesion between the die assembly (such as, tool steel) and the billet (such as, aluminum) at high temperatures. PVD coating can reduce sticking and interaction between the die assembly (such as, tool steel) and billet (such as, aluminum) at high temperatures. To enhance tortuosity of flow, some embodiments implement features such as radial ridges and/or dimples on the baff ring surface.

FIG. 8 illustrates various surface features. The features can be on the front face of the baff ring that interfaces with the billet. 801 illustrates a baff ring with two open portings. The baff ring has features such as trajectory driven ribs extending from the center and across the front surface. 802 illustrates a baff ring with two open portings. The baff ring has a rippled surface. The ripples may increase the pathway that it takes for the material to move into the porting(s) on the baff ring. 803 illustrates a baff ring with two open portings. The baff ring has a surface comprising a plurality of indented dots. 804 illustrates a baff ring with two open portings. The baff ring has a surface comprising a plurality of cleated dots. The indented dots and/or the cleated dots can roughen the baff ring surface. The baff ring surfaces of 805 and 806 have a convex shape. The swept taper shown in 805 has a more pointed surface than the swept arc shown in 806, which has a smoother surface. The baff ring surfaces of 807 and 808 have a concave shape. The inverted swept taper shown in 807 has a more pointed inward surface than the inverted swept arc shown in 808, which has a smoother inward surface. 809 illustrates a circular ring feature around the two portings on the baff ring. 810 illustrates a baff ring with two open portings. The baff ring has ridges comprising a plurality of cleated dots near the center of the baff ring front face and a plurality of cleated dots distributed on the rest of the front face. 811 illustrates a baff ring with no open portings. The center of the front face has a spike feature with a plurality of indented grooves around the edge. 812 illustrates a baff ring with no open portings. The center of the front face has a round disk feature. 813 illustrates a baff ring with four open portings. The baff ring has a concave shape with protruding ridges in the center. The protruding ridges are lower than the surface of the front face such that the blade can remove the unused billet at the end of an extrusion cycle. 814 illustrates a baff ring with four open portings. The baff ring has a concave shape with protruding features in the center. 815 illustrates a baff ring with four open portings. The baff ring has protruding features in the center with ridges and grooves around the edge of the front surface. 816 illustrates a baff ring with four open portings. The baff ring has protruding features extending from the center to the inner edge of the front surface.

The baff ring can have various numbers of porting through the front and back side. In some embodiments, the baff ring can have one porting (also referred to as 1-out tooling, not shown). In some embodiments, the baff ring can have two-porting (also referred to as 2-out tooling). In some embodiments, the baff ring can have four-porting (also referred to as 4-out tooling). The porting(s) can shear and control the first flow of the material (such as heated billet). Baff rings with the same porting(s) designs can be used for extruding parts of different shapes and/or structures. In this way, the same baff ring can be used for extruding different parts, which can reduce the total production and/or tooling cost. The porting(s) can have a tapered shape with a smaller diameter on the front side and a larger diameter on the back side (referred to as a reverse tapered shape). In several embodiments, the reverse tapered shape can provide a larger shearing surface area against the billet during shear assisted extrusion. In contrast, conventional die assembly that has a feeder plate may have tapered porting(s) with a larger diameter on the front side and a smaller diameter on the back side.

FIGS. 9A through 9C illustrate the front and the cross-sectional views of the baff ring in accordance with an embodiment. The baff ring 501 has four portings. The portings can have a tapered shape, with a smaller diameter on the front side and a larger diameter on the back side (a reverse tapered shape). Each of the portings 516 has a triangular shape on the front side. As can be readily appreciated, any suitable shape of the porting(s) (such as, but not limited to, rectangular shapes, trapezoid shapes, circular shapes) can be used as appropriate to the requirements of specific applications in accordance with various embodiments of the invention. The size (such as diameter) of the porting(s) can limit the bulk size (such as diameter) of the extrudate. The number, location, size, shape, and taper of the porting(s) 516 can enable efficient shearing of billet on the front face.

The shear extrusion process can generate a lot of heat at the die billet interface. The baff ring implements internal cooling functions to cool the front surface of the baff ring. Cooling can allow for reduced working temperature of the die/billet interface. Cooling can also enable an increased rotation (such as revolutions per minute, RPM) during shear extrusion process. Lower die/billet interface temperatures enable higher RPM and results in higher shear strain in the extruded material (potential for better refinement in the final extruded product). Cooling channels can be included in the baff ring to implement cooling. Cooling fluid can enter from the operator side of the die slide and exit through the backer in the die ring. Cooling fluid can include cooling liquid, cooling gas, compressed gas, or cryogenic fluid. Cooling fluid can be air, nitrogen, argon, helium, carbon dioxide, or any type of fluid that does not interfere with the die tooling functions. Some embodiments use machining methods and/or gun drilled holes to manufacture the cooling channels. Some embodiments may use additively manufactured (or 3D printed) to manufacture the cooling channels of the baff ring.

FIGS. 10A and 10B illustrate the cooling channels of the die tooling. The cooling channels 518 can cool the baff ring during the extrusion process. The cooling channels 518 can be located on the front face of the baff ring 501. The cooling channels 518 can extend across the surface of the baff ring 501. The cooling channels 518 can have a V shape. Compressed gas can flow through the cooling channels 518 during extrusion to reduce the working temperature of the die tooling. The inlet 519 of the cooling channels can connect with the die slide on the operator side and the cooling fluid can be added to the inlet 519. The outlet 520 of the cooling channels can locate on the backer 504.

FIGS. 11A through 11C illustrate a different routing of the cooling channels of the die tooling. The cooling channels 518 can have a circular shape on the front face of the baff ring. Cooling fluid (such as compressed nitrogen gas) can be fed through the die cap 503 via the inlet 518, into the mandrel 502, and carried up to the interface outlet 520. As can be readily appreciated, the cooling channel sizes, dimensions, and/or positions shown in FIGS. 10A through 11B are exemplary. Any cooling channel sizes, dimensions, and/or positions can be selected based on the baff ring geometries, cooling fluid, flow rate, and/or cooling duration as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.

Lubrication can be applied to the baff ring and container interface to reduce wear during shear extrusion process. The baff ring can include lubrication channels to flow a lubricant that is compatible with the operating temperature of the die tooling and/or the baff ring. The lubricant can be in liquid form such as (but not limited to) grease or oil, or in gas form.

FIGS. 12A and 12B illustrate the lubrication channels of the die tooling. The lubrication channels 522 can be positioned in the baff ring 501. The lubrication channels 522 can be located on the front side of the baff ring to be in contact with the container such that the lubricant can reduce wear. Lubrication back pressure 524 can be applied to the lubrication channels 522 to facilitate the flow. The flow of the lubricants can last a desired amount of time (such as a few hours) for operation. As can be readily appreciated, the lubrication channel sizes, dimensions, and/or positions shown in FIGS. 12A and 12B are exemplary. Any lubrication channel sizes, dimensions, and/or positions can be selected based on the baff ring geometries, expected lubricant viscosity, consumption rate, and/or operating back pressure as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.

The structures of the die tooling can be optimized depending on the requirements of the extrusion. The die tooling can be adjusted to reduce flow volume, or to reduce die pocket depth, or to have tapered bottom (where the feedstock exits the mandrel). FIG. 13A illustrates a baseline design of a die tooling. FIG. 13B illustrates an updated design from the baseline to reduce flow volume. FIG. 13C illustrates an updated design from the baseline to reduce die pocket depth. FIG. 13D illustrates an updated design from the baseline to have tapered bottom. FIG. 13E through 13H illustrate simulations showing material flow through the die tooling in FIG. 13A through 13D respectively. The die tooling with squared bottom shows material flow dead zones (flow velocity is 0) in the corners. The tapered bottom shows improved material flow into the die as shown in FIG. 13H.

The open portings on the baff ring and/or the mandrel can have various sizes to accommodate material flow. The ports grow in volume from the inside out and span of the pocket on the entry and exit of the mandrel can be optimized. FIG. 14A shows the back side of a mandrel where material flow exits the mandrel. FIG. 14B shows the front side of the mandrel where material flow enters the mandrel. The size of the portings 1401 can be optimized.

The mandrel can include added support between the cores. This can be done to tie the cores together for strength and can help with shifting caused by flow timing issues. These modifications were made based on simulation results. The ports are the same volume inside to out. FIG. 15A shows the mandrel with added support 1501 between the cores. FIG. 15B shows the mandrel without the added support.

The entry pocket of the mandrel can have various sizes. FIG. 16A shows the front side of a mandrel with a smaller span of the entry pocket compared to the mandrel in FIG. 16B. The added material 1601 in FIG. 16A can help support the webs allowing for a thinner mandrel.

The baff ring can have various sizes of entry and exit pockets to optimize the volume of the portings. FIG. 17A illustrates the entry and exit of the baff ring are made smaller to help lower the port volume, and the span on the entry of the mandrel has been shortened, compared to the baff ring shown in FIG. 17B. Shorten the span can help reduce the mandrel and baff thickness.

Doctrine of Equivalents

This description of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications. This description will enable others skilled in the art to best utilize and practice the invention in various embodiments and with various modifications as are suited to a particular use. The scope of the invention is defined by the following claims.

As used herein, the singular terms “a,” “an,” and “the,” may include plural referents unless the context clearly dictates otherwise. Reference to an object in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.”

As used herein, the terms “approximately” and “about” are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation. When used in conjunction with a numerical value, the terms can refer to a range of variation of less than or equal to ±10% of that numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1 %, less than or equal to ±0.5%, less than or equal to ±0.1 %, or less than or equal to ±0.05%.

Additionally, amounts, ratios, and other numerical values may sometimes be presented herein in a range format. It is to be understood that such range format is used for convenience and brevity and should be understood flexibly to include numerical values explicitly specified as limits of a range, but also to include all individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly specified. Where ranges are described, the range should be understood to include the endpoints of the ranges, and the endpoints of such ranges are also contemplated to stand on their own as inventive, individual data points and to form the endpoints of other ranges. For example, a ratio in the range of about 1 to about 200 should be understood to include the explicitly recited limits of about 1 and about 200, but also to include individual ratios such as about 2, about 3, and about 4, sub-ranges such as about 1 to about 10, about 10 to about 50, about 20 to about 100, about 100 to about 200, and so forth, and related ranges such as greater than about 1 or less than about 200.