CA2887230C

CA2887230C - Extrusion press die assembly

Info

Publication number: CA2887230C
Application number: CA2887230A
Authority: CA
Inventors: Mark R. Denison
Original assignee: Manchester Copper Products LLC
Current assignee: Manchester Copper Products LLC
Priority date: 2012-10-12
Filing date: 2013-10-11
Publication date: 2020-12-22
Anticipated expiration: 2033-10-11
Also published as: WO2014059293A1; RU2652671C2; CN104936714B; CN104936714A; MX2015004146A; KR20150067245A; AU2013329044B2; BR112015006775B1; CA2887230A1; EP2906371B1; AU2013329044A1; AR093009A1; MY178480A; ES2845300T3; HK1213840A1; EP2906371A4; RU2015117640A; EP2906371A1; CL2015000909A1; US20140102159A1

Abstract

Systems, devices, and methods for continuous extrusion of material billets are provided. A die assembly for press extrusion of a material includes a plurality of die plates forming a die body. The die body has an entrance and an exit having a diameter smaller than the entrance, with a tapered surface between the entrance and the exit. Each die plate has a center bore with a tapered interior surface, and the interior surfaces form the tapered surface that extends from the entrance to the exit. A base is coupled to the die body, and rotation of the base causes rotation of the die body. A billet pressed into the die body is heated by friction between the interior surface and an outer surface of the billet. The billet is heated to a deformable temperature and is extruded into a tube product as the billet is pressed from the entrance to the exit of the die body.

Description

EXTRUSION PRESS DIE ASSEMBLY
Background [0001] Tubing material, such as metal piping formed from copper, aluminum, metal alloy, or other metals, is often manufactured by extrusion processes. In an extrusion process, a large block of metal, referred to as a billet, is worked through a die structure having a circular or other configuration with an opening smaller than the size of the billet used to form the tubing material. The billet may be pre-heated to a high temperature before a piercing rod is forced through the center of the billet to form a channel therethrough. A
large pressure, typically on the order of 1,000 to 100,000 pounds-per-square-inch, is then applied to the billet to force the pre-heated material over the piercing rod and through the die opening. The pressure forces the material to deform and extrude, exiting the back of the die as a tube having a diameter similar to the diameter of the opening of the die.

[0002] In order to produce large quantities of metal tubing by extrusion, large billets and manufacturing machinery are required, and billets used in extrusion processes to create metal tubing often reach or exceed 1,000 pounds in weight. The size of the machines and billets requires large manufacturing facilities to produce the tubing, and the size requirements of the extrusion process lead to large start-up and maintenance costs for the manufacturing operation. Furthermore, limitations of the processes, such as extruding only one billet at a time, lead to inefficiencies from billet sizes.
Summary [00031 Disclosed herein are systems, devices and methods for extruding materials using a rotating extrusion press die assembly. In certain embodiments, the systems, devices and methods allow for continuous extrusion of a plurality of material billets.
Such continuous extrusion allows for relatively smaller billets to be efficiently used to produce a desired quantity of extruded material, and therefore the scale and size requirements of such continuous extrusion press systems can be smaller than conventional extrusions processes.
[0004] In one aspect, a die assembly for extruding a material includes a plurality of die plates coupled together to form a die body. The die body has a passage defining an entrance and an exit, and the diameter of the exit is smaller than the diameter of the entrance. A

3 PCT/US2013/064571 tapered surface is located between the entrance and the exit. Each of the die plates has a center bore with a tapered interior surface around the center bore, and an interior surface of a center bore in a first die plate is tapered at a smaller angle relative to an axis of the passage than an interior surface of a center bore in a second die plate positioned adjacent to a front face of the first die plate. A base is coupled to the die body, and rotation of the base causes the die body to rotate.
[0005] In certain implementations, the second die plate is positioned nearer to the entrance of the die body than the first die plate. The die assembly may include a third die plate having a center bore with an interior surface that is tapered at a larger angle relative to the axis than an interior surface of a center bore in a die plate positioned adjacent to a front face of the third die plate. The die plate positioned adjacent to the front face of the third die plate may be the first die plate, and the third die plate may be positioned nearer to the exit of the die body than the first die plate.
[0006] In certain implementations, the die assembly includes a third plate that forms a portion of the die body, and the third plate has a central bore with an interior surface around the center bore that is not tapered at an angle relative to the axis of the passage. The center bore of the third plate defines the entrance of the die body. In certain implementations, the base includes a center bore, and the center bore of the base has a diameter that is greater than a diameter of the die body exit.
[0007] In certain implementations, the die body is configured to receive a billet of material for extrusion, and the billet is not pre-heated before entering the die body.
Rotation of the die body creates friction between the tapered interior surface and a billet advanced through the entrance and into the interior passage of the die body. The friction heats the billet to a temperature that is sufficient to cause deformation of the billet material, and the heated billet is deformable under a deformation force that does not exceed mechanical property limits of the billet material. Friction between the billet and a mandrel over which the billet is advanced heats the billet and the mandrel. A cooling system provides cooling fluid to an interior portion of the mandrel.
[0008] In certain implementations, at least one of the die plates is formed from two different materials, with a first material forming a perimeter of a bore in the die plate and a second material forming an outer portion of the die plate. At least one of the first and second materials is a ceramic material, a steel, or a consumable material. In certain implementations, a front face of the die body near the entrance is configured to mate with a centering insert having a diameter substantially equal to the diameter of the entrance. The centering insert and a perimeter of the entrance are formed from the same material.
[0009] In certain implementations, the die body is configured to receive a mandrel tip through the entrance such that the mandrel tip is positionable within the interior passage of the die body. The interior surface of the die body includes a complementary portion having an angle that corresponds to an angle of an outer surface of the mandrel tip.
The die body is configured to receive a billet pressed through the interior passage of the die body to form an extruded product, the extruded product having an outer diameter corresponding to the diameter of the exit of the die body and an inner diameter corresponding to a diameter of the mandrel tip.
[00101 In one aspect, a die assembly includes a means for extruding a material that includes a plurality of plate means. The means for extruding has a passage means defining an entrance and an exit of the means for extruding, and the diameter of the exit is smaller than the diameter of the entrance. The means for extruding also has a tapered surface means between the entrance and the exit. Each of the plate means has a center bore with a tapered surface around the center bore, and an interior surface of a center bore in a first plate means is tapered at a smaller angle relative to an axis of the passage means than an interior surface of a center bore in a second plate means positioned adjacent to a front face of the first plate means. The die assembly also includes a means for coupling the means for extruding to a rotation means, and rotation of the means for coupling causes the means for extruding to rotate.
[00111 In certain implementations, the second plate means is positioned nearer to the entrance of the means for extruding than the first plate means. The means for extruding may include a third plate means having a center bore with an interior surface that is tapered at a larger angle relative to the axis than an interior surface of a center bore in a plate means positioned adjacent to a front face of the third plate means. The plate means positioned adjacent to the front face of the third plate means may be the first plate means, and the third plate means may be positioned nearer to the exit of the means for extruding than the first plate means.
[0012] In certain implementations, the die assembly includes a third plate means that forms a portion of the means for extruding, the third plate means having a central bore with an interior surface around the center bore that is not tapered at an angle relative to the axis. The center bore of the third plate means defines the entrance of the means for extruding. In certain implementations, the means for coupling includes a center bore. The center bore of the means for coupling has a diameter that is greater than a diameter of the exit of the means for extruding.
[0013] In certain implementations, the means for extruding is configured to receive a billet of material for extrusion, and the billet is not pre-heated before entering the means for extruding. Rotation of the means for extruding creates friction between the tapered surface means and a billet advanced through the entrance and into the passage means of the means for extruding. The friction heats the billet to a temperature that is sufficient to cause deformation of the billet material. The heated billet is deformable under a deformation force that does not exceed mechanical property limits of the billet material.
Friction between the billet and a rod means over which the billet is advanced heats the billet and the rod means, and a means for cooling provides cooling fluid to an interior portion of the rod means.
[0014] In certain implementations, at least one of the plate means is formed from two different materials, with a first material forming a perimeter of a bore in the plate means and a second material forming an outer portion of the plate means. At least one of the first and second materials is a ceramic material, a steel, or a consumable material. In certain implementations, a front face of the means for extruding near the entrance is configured to mate with a means for centering a billet, the means for centering having a diameter substantially equal to the diameter of the entrance. The means for centering and a perimeter of the entrance are formed from the same material.
[0015] In certain implementations, the means for extruding is configured to receive a rod tip means through the entrance such that the rod tip means is positionable within the interior passage of the means for extruding. The tapered surface means of the means for extruding comprises a complementary portion having an angle that corresponds to an angle of an outer surface of the rod tip means. The means for extruding is configured to receive a billet pressed through the passage means of the means for extruding to form an extruded product, the extruded product having an outer diameter corresponding to the diameter of the exit of the means for extruding and an inner diameter corresponding to a diameter of the rod tip means.
[0016] Variations and modifications of the embodiments discussed herein will occur to those of skill in the art after reviewing this disclosure. The foregoing features and aspects may be implemented in any combination and sub-combination, including multiple dependent combinations, and sub-combinations with one or more other features described herein. The various features described or illustrated herein, including any components thereof, may be combined or integrated in other systems. Moreover, certain features may be omitted or not implemented.

- 4 -Brief Description of the Drawings [0017] The foregoing and other objects and advantages will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings in which like-referenced characters refer to like parts throughout.
[0018] Figure 1 shows a perspective view of an illustrative extrusion press die assembly.
[0019] Figure 2 shows a side elevation view of an illustrative extrusion press system.
[0020] Figure 3 shows a side elevation view of the extrusion press die assembly of Figure 1.
[0021] Figure 4 shows an illustrative steel end holder of the extrusion press die assembly of Figure 1.
[0022] Figure 5 shows an illustrative entry plate of the extrusion press die assembly of Figure 1.
[0023] Figure 6 shows an illustrative first intermediate plate of the extrusion press die assembly of Figure 1.
[0024] Figure 7 shows an illustrative second intermediate plate of the extrusion press die assembly of Figure 1.
[0025] Figure 8 shows an illustrative exit plate of the extrusion press die assembly of Figure 1.
[0026] Figure 9 shows an illustrative base plate of the extrusion press die assembly of Figure 1.
[0027] Figure 10 shows an illustrative cross-section view of the extrusion press die assembly of Figure 1.
[0028] Figure 11 shows an illustrative mandrel bar tip.
[0029] Figure 12 shows an illustrative cross-section of the extrusion press die assembly of Figure 1 with the mandrel bar tip of Figure 11 advanced into the die assembly.
[0030] Figure 13 shows a cross-sectional view of the die assembly and mandrel bar tip of Figure 12 during extrusion of a material.
Detailed Description [0031] To provide an overall understanding of the systems, methods, and devices described herein, certain illustrative embodiments will be described. Although the embodiments and features described herein are discussed for use in connection with extrusion press systems, it will be understood that the components, connection mechanisms, manufacturing methods,

- 5 -and other features outlined below may be combined with one another in any suitable manner and may be adapted and applied to systems to be used in other manufacturing processes.
Furthermore, although the embodiments described herein relate to extruding metal tubing from hollow billets, it will be understood that the systems, devices, and methods described herein may be adapted and applied to systems for extruding any suitable type of material.
[0032] Figure 1 shows a die assembly 1 for forming extruded tubing, which may include seamless extruded tubing, in a press extrusion system. The die assembly 1 may provide for continuous extrusion of a plurality of billets to produce a seamless extruded tubing product according to various seamless tubing standards including, for example, the Standard Specification for Seamless Copper Water Tube. The seamless extruded tubing may also comply with the standards under NSF/ANSI-61 for Drinking Water System Components. The die assembly 1 includes a mandrel bar 10 over which material billets, such as billet 17, are passed in the direction of arrow A and through the die assembly to form an extruded tubing product. The billet 17 may be formed from any suitable material for use in extrusion press systems including, but not limited to, various metals including copper and copper alloys, or any other suitable non-ferrous metals such as aluminum, nickel, titanium, and alloys thereof, ferrous metals including steel and other iron alloys, polymers such as plastics, or any other suitable material or combinations thereof. The billets passing over the mandrel bar 10 are advanced through a centering insert 9 and a die body 18, which is composed of a stack of die plates 3-7 and a base plate 8, and through a cooling system 13 to form the tube product. While die assembly 1 includes five plates coupled to a base plate, a die assembly may include more plates or fewer plates, and a die body may be longer or shorter than the die body 18 in certain applications.
[0033] During extrusion, the die body 18 rotates while billet 17 is pressed through the die body. The billet 17 is held by grippers 44 of the centering insert 9, which does not rotate, and thus the billet 17 does not rotate as it enters the rotating die body 18 at the entrance 11 to the center passage through the die body. The rotation of the die body 18 creates friction with the outer surface of the non-rotating billet 17 as it is pressed through the die, and the friction heats the billet 17 to a temperature sufficient for the billet material to deform. For example, a metal billet may be heated by the friction to a temperature greater than 1000 F for deformation. The temperature requirements of different materials and different metals may vary, and billet temperatures less than 1000 F may be suitable in some applications. In contrast to other extrusion systems, the die assembly 1 does not require pre-heating of billets

- 6 -before extrusion, as the rotation of the die body 18 and the friction created by contact with the non-rotating billet 17 provide energy that heats the billet to a deformable temperature.
100341 The die assembly 1 may be used for forming an extruded material in any suitable extrusion system, including, for example, the extrusion press system described in U.S. Patent Application No. 13/650,977, filed October 12, 2012. For example, the die assembly 1 may be implemented in the extrusion press system 57 shown in Figure 2 for continuous material extrusion. The extrusion press system 57 includes a mandrel carriage section 58 and a platen structure section 59. The mandrel carriage section 58 includes a mandrel bar 74, water clamps or cooling elements 60 and 61, mandrel grips or gripping elements 62 and 63, and a billet delivery system. The mandrel carriage section 58 is supported by a physical carriage structure, which is not shown in Figure 2 to avoid overcomplicating the drawing, but which carriage structure serves as a mount for the components of the mandrel carriage 58. The platen structure section 59 includes an entry platen 65 and a rear die platen 66, press-ram platens 67 and 68, a centering platen 69, and a rotating die 70 that presses against the rear die platen 66. The platen structure section 59 is supported by a frame 71 that also serves as a mount for the motor 72 and related gearbox components (not shown). The direction along which billet loading, transport, and extrusion occurs according to the extrusion press system 57 is denoted by arrow B. The extrusion press system 57 may be operated, at least in part, by a PLC system that controls aspects of the billet delivery subsystem 77, extrusion subsystem 78, and a cooling subsystem of the extrusion press system 57 100351 The mandrel grips 62, 63 comprise a mandrel bar gripping system 73 designed to hold the mandrel bar in place while allowing a plurality of billets to be continuously fed along and about the mandrel bar 74 to provide for continuous extrusion. The mandrel grips 62, 63 may be controlled by the PLC system to securely hold in place and prevent the mandrel bar 74 from rotating such that at any given time during the extrusion process, at least one of the mandrel grips 62, 63 is gripping the mandrel bar 74. The mandrel grips 62, 63 set the position of the mandrel bar 74 and prevent the mandrel bar 74 from rotating.
When the mandrel grips 62, 63 are in a gripping position, thereby gripping the mandrel bar 74, the mandrel grips 62, 63 prevent billets from being transported along the mandrel bar 74 through the grips.
100361 The mandrel grips 62, 63 operate by alternately gripping the mandrel bar 74 to allow one or more billets to pass through a respective mandrel grip at a given time. For example, the upstream mandrel grip 62 may release the mandrel bar 74 while the downstream mandrel

7 grip 63 is gripping the mandrel bar 74. At any given time, at least one of the mandrel grips 62, 63 is preferably gripping or otherwise engaged with the mandrel bar 74. One or more billets queued or indexed near the upstream mandrel grip 62, or being transported along the mandrel bar 74, may pass through the open upstream mandrel grip 62. After a specified number of billets have passed through the open upstream mandrel grip 62, the mandrel gripper 62 may close and thereby return to gripping the mandrel bar 74, and the billets may be advanced to the downstream gripping element 63. The downstream gripping element 63 may remain closed, thereby gripping the mandrel bar 74, or the downstream mandrel grip 63 may open after the upstream mandrel grip 62 re-grips the mandrel bar 74.
Although two mandrel grips 62, 63 are shown in the extrusion press system 57, it will be understood that any suitable number of mandrel grips may be provided.
[0037] The water clamps 60, 61 comprise a mandrel bar water delivery system 75 designed to supply cooling water along the interior of the mandrel bar 74 to the mandrel bar tip during the extrusion process. The water clamps 60, 61 may be controlled by the PLC
system to .. continuously supply process cooling water to the mandrel bar during the extrusion process while allowing a plurality of billets to be continuously feed along and about the mandrel bar 74. The water clamps 60, 61 operate such that there is no or substantially no interruption to the supply of process cooling water to the mandrel bar tip during the extrusion process.
Similar to the operation of the mandrel grips 62, 63 discussed above, when the water clamps 60, 61 are clamped to or engaged with the mandrel bar 74, the water clamps 60, 61 prevent billets from being transported along the mandrel bar 74 through the water clamps.
[0038] The water clamps 60, 61 operate such that at any given time during the extrusion at least one of the water clamps is clamped to or engaged with the mandrel bar 74 and thereby delivers cooling water into the mandrel bar 74 for delivery to the tip of the mandrel bar.
.. When a billet passes through one of the water clamps 60, 61, the respective water clamp discontinues delivering cooling water and releases or disengages the mandrel bar 74 to allow the billet to pass therethrough before re-clamping the mandrel bar 74 and continuing to deliver cooling water. While one of the water clamps 60, 61 is unclamped or disengaged from the mandrel bar 74, the other water clamp continues to deliver cooling water to the mandrel bar.
[0039] For example, the upstream water clamp 60 may release the mandrel bar 74 while the downstream water clamp 61 is clamped to the mandrel bar 74. At any given time, at least one of the water clamps 60, 61 is preferably clamped to the mandrel bar 74 to continuously deliver cooling water. One or more billets queued or indexed near the upstream water

- 8 -clamp 60, or being transported along the mandrel bar 74, may pass through the open upstream water clamp 60. After a specified number of billets has passed through the open upstream water clamp 60, the water clamp 60 may close and thereby return to clamping the mandrel bar 74 and delivering cooling water, and the billets may be advanced to the downstream water clamp 61. The downstream water clamp 61 may remain closed, thereby clamping the mandrel bar 74, or the downstream water clamp 61 may open after the upstream water clamp 60 re-clamps to the mandrel bar 74. Although two water clamps 60, 61 are shown in the extrusion press system 57, it will be understood that any suitable number of water clamps may be provided.
[0040] The mandrel bar 74 extends along substantially the length of the extrusion press system 57 and is positioned to place the mandrel bar tip through the rotating die 70. The rotating die 70 may incorporate the die body 18 shown in Figure 1. The adjustment to properly position the mandrel bar tip through the die 70 is accomplished by moving the mandrel carriage section 58, thus moving the mandrel bar 74. The adjustments to the mandrel bar 74 and the mandrel carriage section 58 may be towards or away from the die 70.
The mandrel bar 74 and the mandrel carriage section 58 preferably cannot be adjusted while the extrusion press system 57 is in operation, although it will be understood that in certain embodiments the mandrel bar 74 and/or mandrel carriage section 58 may be adjusted during operation.
.. [0041] As discussed above, the extrusion press system 57 includes a platen structure section 59 having an entry platen 65 and a rear die platen 66, press-ram platens 67 and 68, a centering platen 69, and a rotating die 70 presses against the rear die platen 66. Near the entry platen 65 is the press-ram platen assembly 76 that includes a first press-ram platen 67, or A-Ram, and a second press-ram platen 68, or B-Ram. The first and second press-ram platens 67, 68 feed billets into the centering platen 69, which grips the billets and prevents the billets from rotating prior to entering the rotating die 70, which presses against the rear die platen 66.
[0042] The press-ram platens 67, 68 operate by gripping the billets and providing a substantially constant pushing force in the direction of the extrusion die stack 70. At any given time at least one of the press-ram platens 67, 68 grips a billet and advances the billet along the mandrel bar 74 to provide the constant pushing force. The press-ram platens 67, 68 form the final part of the billet delivery subsystem 77 before the billet enters the centering insert 69 and the rotating die 70 of the extrusion subsystem 78. Similar to the billet feed track section before the entry platen 65, the section prior to the press-ram platens 67, 68

- 9 -preferably continuously indexes the billets to minimize any gaps between a billet that is gripped by the press-ram platens 67, 68 and the next billet.
[0043] As discussed above, the press-rams 67, 68 continuously push billets into the rotating die 70. The press-rams 67, 68 alternate gripping and advancing billets towards and into the rotating die 70 and then ungripping the advanced billets and retracting for the next gripping/advancing cycle. There is preferably an overlap between the time when one press-ram stops pushing and the other press-ram is about to start pushing so that there is always uniform pressure on the rotating die 70. The press-rams 67, 68 advance and retract via press-ram cylinders coupled to the respective press-ram. As shown there arc two press-ram cylinders 79, 80 per press-ram. A first set of press-ram cylinders 80 is located on the left and right of the entry platen 65 (although the right-side press-ram cylinder is hidden from view behind the left-side press-ram cylinder). The first set of press-ram cylinders 80 couples with the first press-ram platen 67 and is configured to move the first press-ram 67 as the first press-ram 67 advances billets and retracts to grab a following billet. A
second set of press-ram cylinders 79 is located to the top and bottom of the entry platen 65. The second set of press-ram cylinders 79 couples with the second press-ram platen 68 and is configured to move the second press-ram 68 as the second press-ram 68 advances billets and retracts to grab a following billet. Although two press-ram cylinders are shown for each of the first and second press-ram platens 67, 68, it will be understood that any suitable number of press-ram cylinders may be provided, and in certain embodiments press-ram cylinders may be coupled to both the first and second press-rams 67, 68.
[00441 The centering platen 69 receives billets advanced by the press-rams 67, 68 and functions to hold the billets during the extrusion process prior to entry of the billets into the rotating die 70. When the centering platen 69 is positioned in place for the extrusion process, the centering platen 69 substantially becomes part of the extrusion die 70.
That is, a centering insert of the centering platen 69 substantially abuts the rotating die 70. The centering platen 69 itself, however, and the components therein including the centering insert, do not rotate with the rotating die 70. The centering platen 69 prevents the billets that are no longer held by the second press-ram from rotating while the die 70 rotates by gripping the billets and thereby preventing the billets from rotating prior to entry of the billets into the rotating die 70.
[0045] Referring back to the die assembly 1 of Figure 1, when the assembly is used in an extrusion process, for example in the extrusion system of Figure 2, the centering insert 9 is advanced to the front edge of the die body 18, such that a front surface 55 of the centering

- 10 -insert 9 contacts a front surface 16 of the die body 18. This orientation of the die body 18 and the centering insert 9 during extrusion is shown in Figure 3. In this orientation, the contact between the faces 55 and 16 of the centering insert 9 and die body 18, respectively, prevents material from escaping the die body 18 during the extrusion process.
To begin the extrusion, a billet 17 is advanced over the mandrel bar 10 in the direction of arrow A and through the die assembly 1 to press the billet 17 into an extruded tube product. Before entering the die assembly 1, the billet 17 is advanced into the opening 15 of the centering insert 9, where grippers 44 engage the outer surface of the billet 17. As the billet 17 is advanced through the opening 15, these grippers 44 prevent rotation of the billet 17 when the billet 17 is contacted by the rotating interior surface 14 of the die body 18.
[00461 While the billet 17 and centering insert 9 do not rotate during the extrusion process, the die body 18 and base plate 8 to which the die body is connected are rotated by the motor-driven spindle 56. As the billet 17 is advanced through the centering insert 9, it passes through the entrance 11 of the die body 18 and contacts the interior surface 14 of the die body 18. A torsional force is applied to the outer surface of the billet 17 due to the interference contact between the rotating die 18 and the billet 17. The grippers 44 of the centering insert 9 resist this torsional force and prevent the billet 17 from rotating before it enters the die body 18, creating friction and producing the energy that heats the billet 17.
[00471 The profile of the tapered interior surface 14 of the die body 18 is defined by the shape and orientation of central bores that pass through the plates in the die body 18. The die body 18 is formed of a stack of die plates, including a steel end holder 3, an entry plate 4, a first intermediate plate 5, a second intermediate plate 6, and an exit plate 7. This series of plates that makes up the die body 18 are stacked together, secured to one another by a fastener, such as the bolt 2 in Figure 1, and connected to the base plate 8.
The bolt 2 is placed into each of the through-holes 12, which pass through each of the plates 3-8.
The base plate 8 is then coupled to motor-driven spindle 56, which rotates the plate 8, as well as the plates 3-7 of the die body 18. In certain implementations, a die body may be employed that includes more or fewer than the five plates 3-7 shown in die body 18.
[00481 The interior surface 14 created by the central bores of the plates of the die body 18 exhibits a tapered profile that narrows the interior passage through the die body 18 from the entrance 11 to an exit of the passage at the exit plate 7. Thus, when force is applied to the billet 17 to press the billet through the die body 18, the material of the billet 17 is extruded as the outer diameter of the material is forced to decrease to pass through each of the plates 3-7.

-11-The dimensions of the plates 3-7, and the interaction between the interior surface 14 and the billet 17, is described in more detail below with respect to Figures 4-13.
[0049] Figures 4-9 show each of the plates 3-7 in the die body 18, and the base plate 8 to which the die body 18 is connected. Figure 4 shows the steel end holder 3 of the die body 18 that forms the front face 16 of the die body and the entrance 11 to the interior passage of the die body. The steel end holder 3 includes a central circular bore 21 that defines the diameter of the opening entrance 11 when stacked in the die body 18. As shown in Figure 4, the steel end holder 3 is formed from two materials, with the outer perimeter 19 of the plate formed from one material and the perimeter 20 of the bore 21 formed from a different material. The two materials that make up the steel end holder 3 may be chosen to form complementary interfaces between the steel end holder 3 and both the centering insert 9 and the entry plate 4.
For example, the outer perimeter 19 may be formed of a steel, such as H13 steel, that is the same as or similar to the material that forms an outer perimeter of the entry plate 4, while the bore perimeter 20 may be formed of a different material, such as an inconel steel, that is the same as or similar to the material used to form the centering insert 9. By matching the material of the bore perimeter 20 and the centering insert 9, the front face 23 of the bore perimeter 20 that contacts the front face 55 of the centering insert 9 provides a complementary interface that reduces wear when the die assembly 1 is in use.
Because the die body 18 rotates and the centering insert 9 remains stationary, friction may be created between the face 23 and the face 55. By forming the bore perimeter 20 and the centering insert 9 from the same material or similar materials, along with adjusting the pressure of surface 55 against surface 16, the wearing effect of this friction can be minimized, particularly during start up and shut down of the extrusion process when rotation of the die body 18 starts or stops.
[0050] The second plate in the die body 18 is the entry plate 4, shown in Figure 5. As with the steel end holder 3, the entry plate 4 is formed from two different materials. One material forms the outer perimeter 25 of the plate while a second material forms the bore perimeter 24 around the central bore 26 through the center of the plate. The outer perimeter 25 may be made of the same material or a similar material as the outer perimeter of the steel end holder 3, for example H13 steel material. The perimeter 24 of the bore 26 is formed from a wear-resistant material, for example a ceramic material, that resists degradation when a billet, such as billet 17, is pressed through the bore 26 and contacts the interior surface 27.
[0051] The entry plate 4 begins the taper of the interior surface 14 of the die body 18 from the entrance 11 to the exit of the die body. The interior surface 27 of the perimeter 24 is

- 12 -angled such that the diameter across the diameter of the center bore 26 is greater at the front face of the plate 4 that abuts the back face of the steel end holder 3 and smaller at the back face of the entry plate 4 that abuts the first intermediate plate 5. When billet 17, having a diameter that is equal to the diameter of the bore 26 at the front face, is pressed through the entry plate 4, the tapering of the surface 27 creates friction between the rotating plate 4 and the billet 17. This friction generates energy that heats the billet 17 as it is advanced into the rotating die body 18, beginning the deformation of the billet through the tapered interior surface 14. In contrast to extrusion processes in which contact between a pre-heated billet and a non-rotating die creates heat energy as a by-product, the friction heating of the non-pre-heated billet 17 is necessary for extrusion as it is needed to heat the billet to a temperature adequate for deformation.
[0052] Figure 6 shows the first intermediate plate 5 that is located behind the entry plate 4 in the stack of plates that make up the die body 18. The first intermediate plate 5 includes an outer perimeter 29, formed from a first material, and a bore perimeter 28, formed from a second material. The outer perimeter 29 may be formed of the same materials or similar materials as the outer perimeters of the other plates in the stack, for example an H13 steel.
Perimeter 28 of the center bore 30 through the plate is formed from a wear-resistant material, for example a ceramic material, as discussed with respect to bore perimeter 24 of the entry plate 4. The inner surface 31 of the bore perimeter 28 is tapered from the front face of the first intermediate plate 5 that abuts the entry plate 4 in the stack to the back face of the first intermediate plate 5 that abuts the second intermediate plate 6 in the plate stack. The angling of the inner surface 31 tapers the center bore 30 from the front face to the rear face and further tapers the interior passage and surface 14 of the die body 18, as discussed above with respect to the center bore 26 of the entry plate 4.
[0053] The degree at which the inner surface 31 tapers with respect to a center axis of the central bore 30 in the first intermediate plate 5 relative to the taper angle of the inner surface 27 of the entry plate 4 is dependent on the material being extruded and the total overall number of die plates. In certain implementations for a particular material, the degree at which the inner surface 31 tapers may be less than the taper angle of the inner surface 27 of the entry plate 4. This change in the angle of the inner surface and the smaller diameter of the center bore 30 relative to the center bore 26 may spread the frictional interface with the billet 17 and the work required to deform the billet 17 more evenly over the entry plate 4 and the first intermediate plate 5, reducing material wear and extending the lifetime of the die plates as well as improving concentricity and uniformity of an extruded product. This

- 13 -spreading of work and frictional force and the correlation between materials and the degree of surface tapering is discussed more fully below with respect to the cross sections shown in Figures 10, 12 and 13.
[00541 The second intermediate plate 6, which follows the first intermediate plate 5 in the die stack, is shown in Figure 7. Similar to plates 3-5, the second intermediate plate 6 has an outer perimeter 32, formed of a first material, and a perimeter 33 around a center bore 34, formed of the second material. The first material that forms outer perimeter 32 may be the same as or similar to the other plates in the stack, for example an H13 steel, and the material that forms the bore perimeter 33 may be a wear-resistant material, such as a ceramic. The interior surface 35 of the perimeter 33 around the central bore 34 is angled from a front face of the plate 6 that abuts the first intermediate plate 5 to a back face of the plate 6 that abuts the exit plate 7.
[00551 The final plate in the plate stack that makes up the die body 18 is the exit plate 7, which is shown in Figure 8. The exit plate 7, similar to plates 3-6, has an outer perimeter 36 formed from a first material, such as an H13 steel, and a perimeter 37 around a central bore 38 formed from a second material, for example a wear-resistant ceramic. The diameter of exit plate 7 is substantially smaller than the diameter of the opening 11 at the steel end holder 3 shown in Figure 4 as a result of the tapering of the interior surface 14 from the steel end holder 3 to the exit plate 7. The interior surface 39 that surrounds the central bore 38 of exit plate 7 is angled with respect to a central axis of the center bore 38. The narrowest section of the center bore 38 defines the narrowest portion of the passage through the die body 18, and thus sets the outer diameter of an extruded tube that is produced when a billet 17 is pressed through the die body 18. This diameter and the dimensions of the extruded product created using the die assembly 1 are discussed in more detail below with respect to Figure 13.
[00561 Figure 9 shows the base plate 8, which couples the stacked plates that form the die body 18 to a rotational power source. For example, as shown in Figures 1 and 3, the base plate 8 in the die assembly 1 couples the die body 18 to a spindle 56. The spindle 56 is driven to rotate by a motor that powers the rotation of the spindle 56 at a set rotational speed.
The spindle 56 is connected to the base plate 8 by bolts which pass through outer through-holes 43 around the perimeter of the base plate 8 and transfer the rotational force of the spindle 56 to the base plate 8. The base plate 8 is also rotationally coupled to the plates in the die body 18 by bolts, such as bolt 2 shown in Figure 1, that pass through the through-holes 12 of the die body 18 and into the holes 42 in the base plate 8.

- 14 -[0057] The base plate 8 includes a central bore 40 having an interior surface 41. The bore 40 and the interior surface 41 define an opening in the base plate 8 that may have a wider diameter than the diameter of the bore in the exit plate 7. The wider diameter of the base plate bore 40 allows the extruded material to exit the die body 18 without directly contacting .. the interior surface 41 and may allow for a cooling component, such as a fluid source, to partially enter the base plate 8 and apply a cooling fluid to extruded material exiting the exit plate 7 near the exit of the die body 18. The exit plate 7 may also include a relief angle near the back face of the plate that further facilitates the application of cooling fluid, as discussed below with respect to Figure 13.
[00581 The die assembly 1 is assembled prior to extrusion by stacking plates 3-7 and connecting the die body 18 formed by the plates to the base plate 8 with bolts placed into the through-holes 12 of the die body plates and into the holes 42 of the base plate. The stacking of these plates to form the die body 18 forms the interior profile of the die body 18 that causes extrusion of billets pressed through the die assembly 1. This inner profile and the orientation of the stacked plates are shown in the cross-sectional view of the die assembly 1 in Figure 10.
[00591 The cross section in Figure 10 shows the die body 18 and the centering insert 9 positioned for extrusion. The die plates 3-7 are coupled together and fastened to the base plate 8 by bolts 2 inserted into the series of through-holes 12 in the outer perimeters 19, 25, 29, 32, and 36 of the plates. In this orientation, the opening 11 of the interior passage 54 in the die body 18 is aligned with the centering insert 9 to receive a billet pressed through the opening 15 of the centering insert 9 and into the die body 18 along the center axis 45 of the interior passage 54.
[00601 Each of the bore perimeters 23, 24, 28, 33, and 37 of the die plates 3-7 abuts bore perimeters in adjacent plates to form the tapered interior surface 14 that outlines the interior passage 54 through the die body 18. The inner surface 14 narrows the interior passage 54 from the largest diameter of the passage at the opening 11 to the smallest diameter at the exit 81, and the narrowing of the passage 54 causes the narrowing deformation and extrusion of a billet pressed into the rotating die body 18 during operation. The extrusion requires friction energy to be produced at the interface of the inner surface 14 to heat the billet, and the energy can create wear on the bore perimeters of the die plates 3-7. To reduce the effect of the friction wear and produce uniform stresses across the interior surface 14 during extrusion, the inner surfaces 27, 31, 35, and 39 are designed to spread the friction interface and reduce the concentration of energy and friction on any one plate. The design of the inner surfaces and

- 15 -the profile of the interior surface 14 may differ for different applications, and in particular for the extrusion of different materials. Depending on the material properties of billets used for extrusion, for example heat transfer properties that may affect the heating of the billets during extrusion, the inner profile of die plates in a die body may be varied to spread work and wear over the die plates. In addition, the die rotation speed may be varied to increase the efficiency of the die and avoid exceeding material properties of the billets.
For example, a die rotation speed between about 200 rpm and about 1000 rpm may be used. In certain implementations, a slower rotation speed, for example about 300 rpm, may be desired to avoid applying a high level of torsional sheer to a billet while still heating the billet to a sufficient temperature for deformation. A faster speed, for example about 800 rpm, may be used for a material that is not adversely affected by a higher torsional sheer or that requires more energy, and thus greater friction, to heat to a deformation temperature.
In other implementations, die rotation speeds in excess of 100 rpm may be desired for extrusion.
[00611 As shown in Figure 10, the inner surfaces 27, 31, 35, and 39 do not taper at uniform angles with respect to the central axis 45. Each surface in the depicted die is tapered at an angle that decreases from the entry plate 4 near the opening 11 to exit plate 7 at the exit 81.
This decreasing angle design may be desired for a particular extrusion material or application of the die assembly 1. In certain embodiments, however, the taper angle of the interior surface 27 with respect to the central axis 45 may be equal to or less than the taper angle of the adjacent surface 31. In the embodiment shown in Figure 10, the angle 46 at which the interior surface 27 of the entry plate 4 is tapered is greater than the angle 47 at which the interior surface 39 of the exit plate 7 is tapered. The differences in taper angles between the plates spreads the frictional energy and stress over the plates as a result of the differences in diameters of the center bores from the opening 11 to the exit 81.
[0062] Each plate has an entrance diameter, for example diameter d5 of plate 4, and an exit diameter, for example diameter d7 of plate 4. When a billet is pressed into the plate, a threshold amount of energy must be generated to heat and deform the billet from the diameter d5 to the diameter d7. This amount of energy is affected by the percent reduction in diameter, in particular the resulting percent reduction in cross-sectional area of a billet as it passes through the plate 4. If the central bores in plates 3-7 were each tapered at a single uniform angle, the diameter change from the entrance to the exit of each plate would be equal, and thus the percent reduction in billet cross-sectional area would increase for each successive plate. For example, if the absolute difference between diameters d5 and d7 of plate 4 were equal to the absolute difference between diameters d6 and d8 of plate 7, the

- 16 -percent reduction in the diameter of the central bore would be higher in plate 7 than plate 4, and a greater amount of stress and energy could cause plate 7 to wear faster than plate 4.
[0063] In addition to the percent area reduction of a billet over a plate, mechanical and thermal properties of the billet materials may dictate the number and design of plates in a die stack. For example, a billet material having high thermal conductivity may heat up to a deformable temperature more quickly than a material having a low thermal conductivity, and thus a shorter die with fewer plates may be used for the high conductivity material. In addition, the tapering angles of the inner surface of a die may be greater for the high conductivity material as a result of the quicker heating of the billet. In other implementations, dies of equal size having the same number of plates may be used, and the tapering angles of the dies may differ to accommodate the different thermal properties and heat the billets to a deformable temperature while spreading work and wear as evenly as possible over the die surface and the surface of a mandrel tip within the die.
[0064] A billet pressed through the die body 18 produces an extruded tube product through exit 81 of the die body 18 having an outer diameter that is similar to the diameter d8, the diameter at the narrowest portion of exit plate 7. The inner diameter of the extruded product is selected by advancing the mandrel bar 10 into the die body 18 with a mandrel tip having an end dimension, selected to create the inner diameter of the tube product, at the end of the mandrel bar 10. Figure 11 shows a mandrel tip 48 that may be coupled to the end of the mandrel bar 10 to create a desired inner diameter for extruded tubing. The mandrel tip 48 has an open end 82 that is configured to couple to the end of the mandrel bar 10.
The friction energy and heat generated during extrusion may heat the mandrel tip 48, and the open end 82 may receive cooling fluid, such as water or gas, from a cooling system that runs through the mandrel bar 10 to cool the mandrel tip 48.
[0065] Opposite the open end 82 of the mandrel tip 48 is a closed end 51. The diameter of the closed end 51 is the dimension that sets the inner diameter of a tube extruded over the tip 48, and the tip 48 can be selected from a series of tips having different diameters to achieve extrusions with different inner diameter dimensions. Between the open end 82 and the closed end 51 are three portions 49, 83, and 50 of the tip outer surface 84. During extrusion, a billet is pressed over the mandrel bar 10 and the tip 48 in the direction of arrow C
such that the billet passes over a deformation region including tip portions 49 and 83, and an end portion 50. When the tip 48 is positioned for extrusion, the tip is advanced into a die until the closed end 51 extends beyond the rear exit of the die at which the die diameter is narrowest. A billet having a hollow core diameter substantially equal to the outer diameter of the tip portion 49 is

- 17 -then passed over the mandrel bar 10 and the tip 48. At the tip portion 49, the diameter of the surrounding die narrows, and friction between the die and the billet creates energy that heats the billet as the outer diameter of the billet is compressed. The heated billet then passes over the tip portion 83, and the inner diameter of the hollow core of the billet decreases to the outer diameter of end portion 50 as the material extrudes. This extrusion over the mandrel tip 48 is discussed in more detail below with respect to Figures 12 and 13.
[0066] Figure 12 shows the die assembly 1 with the mandrel 10 and mandrel tip advanced through the centering insert 9 and into the center passage 54 of the die body 18.
The mandrel 10 is positioned such that the mandrel tip 48 extends through the exit 81 in the exit plate 7. As discussed above with respect to Figure 2, gripping elements in an extrusion press system may be used to hold the mandrel bar 10 and in the orientation shown in Figure 12 and to resist rotation while the die body 18 is rotated and a billet passes over the mandrel bar 10.
[0067] Figure 13 shows the die assembly and mandrel tip configuration of Figure 12 as the billet 17 is passed through the die body 18 and extruded to form tubing 53.
During extrusion, the die body 18 is rotated while the mandrel bar 10 and centering insert 9 are held stationary.
The billet 17 is pressed into the die body 18 in the direction of arrow A and contacts the interior surface 14 of the die body 18 at a first contact point 85. The interference contact between the interior surface 14 and the billet 17 begins at the contact point 85 and generates the energy that heats the billet 17 to a plastic deformable temperature.
[0068] As the billet 17 is advanced over the first portion 49 of the mandrel tip 48, the taper of the interior surface 14 applies a compression force to the outer surface of the billet 17 that presses the billet 17 inwards towards the mandrel tip 48. Because the billet 17 is in a plastic deformation state, the material in the billet extrudes in the direction of portion 83 of mandrel tip 48 as the die body 18 decreases the outer diameter of the billet 17 from the original diameter d2. When the billet 17 reaches the tip portion 83, the taper of the tip portion 83 towards the end portion 50 causes the inner diameter of the billet 17 to extrude and decrease from the original diameter dl as the billet advances further over the mandrel tip 48. The tapered surface of the mandrel tip 48 at the tip portion 83 may substantially correspond to the angle of the interior surface 14 in the area surrounding the tip portion 83 to create substantially uniform extrusion in that portion. For example, the outer and inner diameters of the billet 17 may decrease by substantially the same amount or by substantially the same percentage from the end of tip portion 83 proximate first tip portion 49 to the end of tip portion 83 proximate end portion 50.

- 18 -[0069] When the extruding billet 17 reaches the end portion 50, the inner diameter of the billet is reduced from the original diameter dl to the final diameter d3 of the end tubing product. As the billet 17 passes over the end portion 50, the outer diameter of the billet 17 continues to decrease to the final outer diameter d4 when the extruded tubing product 53 exits the exit plate 7. At the point of exit, the formation of the extruded product 53 is complete.
Due to the friction and heating within the die body 18, the product 53 is at a heightened temperature upon exit from the die body 18, and a cooling element may be applied to prevent further deformation or increase operational safety of the extrusion press, eliminate the escape of extruded material, or maintain desired material characteristics. The bore 40 in the base plate 8 is shown in Figure 13 with a diameter larger than the exit diameter of the exit plate 7.
This configuration may be preferable in order to allow cooling elements and cooling fluid to reach into the base plate 8 and contact the extruded product 53 as soon as it exits the final bearing in the exit plate 7 for earlier cooling. The exit plate 7 includes an angled relief surface 86 to further facilitate the introduction of a fluid material as near as possible to the exit 81 of the die body 18. After the product 53 exits the base plate 8 and passing through a cooling system, the extrusion process is complete, and the product 53 may be gathered for post-processing.
[0070] It is to be understood that the foregoing description is merely illustrative and is not to be limited to the details given here in. While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems, devices and methods and their components may be embodied in many other specific forms without departing from the scope of this disclosure.
[0071] Various modifications will occur to those with skill in the art after reviewing this disclosure. The disclosed features may be implemented in any combination and sub-combinations, including multiple-dependent combinations and sub-combinations with one or more features described herein. The various features described or illustrated above, including any components thereof, may be combined or integrated into other systems, Moreover, certain features may be omitted or not implemented. Examples of changes, substitutions and alterations are ascertainable by one skilled in the art and can be made without departing from the scope of the information disclosed herein. All references cited herein are incorporated by reference in their entirety and made part of this application.

- 19 -

Claims

What is claimed is:

1. A die assembly for extruding a material, comprising:
a plurality of die plates coupled together to form a die body having:
a passage defining an entrance and an exit, wherein the diameter of the exit is smaller than the diameter of the entrance; and a tapered interior surface between the entrance and the exit;
wherein each of the die plates has a center bore with an interior surface around the center bore, an interior surface of a center bore in a first die plate being tapered at a smaller angle relative to an axis of the passage than an interior surface of a center bore in a second die plate positioned adjacent to a front face of the first die plate; and wherein the die body is configured to receive a mandrel tip through the entrance such that the mandrel tip is positionable within the passage, and the tapered interior surface comprises a complementary portion having an angle that corresponds to an angle of an outer surface of the mandrel tip such that the mandrel tip is able to press a billet completely through the die body; and a base coupled to the die body, wherein rotation of the base causes the die body to rotate.

2. The die assembly of claim 1, wherein the second die plate is positioned nearer to the entrance of the die body than the first die plate.

3. The die assembly of claim 1 or 2, further comprising a third die plate having a center bore with an interior surface that is tapered at a larger angle relative to the axis than an interior surface of a center bore in a die plate positioned adjacent to a front face of the third die plate.

4. The die assembly of claim 3, wherein the die plate positioned adjacent to the front face of the third die plate is the first die plate.

5. The die assembly of claim 3 or 4, wherein the third die plate is positioned nearer to the exit of the die body than the first die plate.

6. The die assembly of claim 1, further comprising a third plate that forms a portion of the die body, the third plate having a central bore with an interior surface around the center bore that is not tapered at an angle relative to the axis.

7. The die assembly of claim 6, wherein the center bore of the third plate defines the entrance of the die body.

8. The die assembly of any one of claims 1 to 7, wherein the base comprises a center bore.

9. The die assembly of claim 8, wherein the center bore of the base has a diameter that is greater than a diameter of the die body exit.

10. The die assembly of any one of claims 1 to 9, wherein the die body is configured to receive a billet of material for extrusion, and the billet is not pre-heated before entering the die body.

11. The die assembly of claim 10, wherein rotation of the die body creates friction between the tapered interior surface and the billet advanced through the entrance and into the interior passage of the die body.

12. The die assembly of claim 11, wherein the friction heats the billet to a temperature that is sufficient to cause deformation of the billet material.

13. The die assembly of claim 12, wherein the heated billet is deformable under a deformation force that does not exceed mechanical property limits of the billet material.

14. The die assembly of claim 13, wherein friction between the billet and a mandrel over which the billet is advanced heats the billet and the mandrel.

15. The die assembly of claim 14, wherein a cooling system provides cooling fluid to an interior portion of the mandrel.

16. The die assembly of any one of claims 1 to 15, wherein at least one of the die plates is formed from two different materials, with a first material forming a perimeter of a bore in the die plate and a second material forming an outer portion of the die plate.

17. The die assembly of claim 16, wherein at least one of the first and second materials is selected from the group consisting of a ceramic material, a steel, and a consumable material.

18. The die assembly of any one of claims 1-17, wherein a front face of the die body near the entrance is configured to mate with a centering insert having a diameter substantially equal to the diameter of the entrance.

19. The die assembly of claim 18, wherein the centering insert and a perimeter of the entrance are formed from the same material.

20. The die assembly of claim 1, wherein the die body is configured to receive a billet pressed through the interior passage of the die body to form an extruded product, the extruded product having an outer diameter corresponding to the diameter of the exit of the die body and an inner diameter corresponding to a diameter of the mandrel tip.

21. A die assembly, comprising:
means for extruding a material, said means comprising a plurality of plate means and having:
passage means defining an entrance and an exit of the means for extruding, wherein the diameter of the exit is smaller than the diameter of the entrance;
and tapered surface means between the entrance and the exit;
wherein each of the plate means has a center bore with a tapered surface around the center bore, an interior surface of a center bore in a first plate means being tapered at a smaller angle relative to an axis of the passage means than an interior surface of a center bore in a second plate means positioned adjacent to a front face of the first plate means; and wherein the means for extruding is configured to receive a rod tip means through the entrance such that the rod tip means is positionable within the passage, and the tapered interior surface comprises a complementary portion having an angle that corresponds to an angle of an outer surface of the rod tip means such that the rod tip means is able to press a billet completely through the means for extruding; and means for coupling the means for extruding to a rotation means, wherein rotation of the means for coupling causes the means for extruding to rotate.

22. The die assembly of claim 21, wherein the second plate means is positioned nearer to the entrance of the means for extruding than the first plate means.

23. The die assembly of claim 21 or 22, further comprising a third plate means having a center bore with an interior surface that is tapered at a larger angle relative to the axis than an interior surface of a center bore in a plate means positioned adjacent to a front face of the third plate means.

24. The die assembly of claim 23, wherein the plate means positioned adjacent to the front face of the third plate means is the first plate means.

25. The die assembly of claim 23 or 24, wherein the third plate means is positioned nearer to the exit of the means for extruding than the first plate means.

26. The die assembly of claim 21, further comprising a third plate means that forms a portion of the means for extruding, the third plate means having a central bore with an interior surface around the center bore that is not tapered at an angle relative to the axis.

27. The die assembly of claim 26, wherein the center bore of the third plate means defines the entrance of the means for extruding.

28. The die assembly of any one of claims 21 to 27, wherein the means for coupling comprises a center bore.

29. The die assembly of claim 28, wherein the center bore of the means for coupling has a diameter that is greater than a diameter of the exit of the means for extruding.

30. The die assembly of any one of claims 21 to 29, wherein the means for extruding is configured to receive a billet of material for extrusion, and the billet is not pre-heated before entering the means for extruding.

31. The die assembly of claim 30, wherein rotation of the means for extruding creates friction between the tapered surface means and the billet advanced through the entrance and into the passage means of the means for extruding.

32. The die assembly of claim 31, wherein the friction heats the billet to a temperature that is sufficient to cause deformation of the billet material.

33. The die assembly of claim 32, wherein the heated billet is deformable under a deformation force that does not exceed mechanical property limits of the billet material.

34. The die assembly of claim 33, wherein friction between the billet and a rod means over which the billet is advanced heats the billet and the rod means.

35. The die assembly of claim 34, wherein a means for cooling provides cooling fluid to an interior portion of the rod means.

36. The die assembly of any one of claims 21 to 35, wherein at least one of the plate means is formed from two different materials, with a first material forming a perimeter of a bore in the plate means and a second material forming an outer portion of the plate means.

37. The die assembly of claim 36, wherein at least one of the first and second materials is selected from the group consisting of a ceramic material, a steel, and a consumable material.

38. The die assembly of any one of claims 21 to 37, wherein a front face of the means for extruding near the entrance is configured to mate with a means for centering a billet, the means for centering having a diameter substantially equal to the diameter of the entrance.

39. The die assembly of claim 38, wherein the means for centering and a perimeter of the entrance are formed from the same material.

40. The die assembly of claim 21, wherein the means for extruding is configured to receive a billet pressed through the passage means of the means for extruding to form an extruded product, the extruded product having an outer diameter corresponding to the diameter of the exit of the means for extruding and an inner diameter corresponding to a diameter of the rod tip means.