US3191413A

US3191413A - Extrusion apparatus with removable die insert

Info

Publication number: US3191413A
Application number: US219917A
Authority: US
Inventors: Walter H Stulen
Original assignee: Baldwin Lima Hamilton Corp
Current assignee: Baldwin Lima Hamilton Corp
Priority date: 1962-08-28
Filing date: 1962-08-28
Publication date: 1965-06-29
Anticipated expiration: 1982-06-29
Also published as: GB1012388A

Description

June 29, 1965 w. H. STULEN 3,

EXTRUSION APPARATUS WITH REMOVABLE DIE INSERT Filed Aug. 28. 1962 3 Sheets-Sheet l INVENTOR. WALTER H. STULE/V ATTORNEY EXTRUSION APPARATUS WITH REMOVABLE DIE INSERT Filed Aug. 28, 1962 June 29, 1965 w. H. STULEN 3 Sheets-Sheet 2 United States Patent 3,191,413 EXTRUSION APPARATUS WITH REMOVABLE DIE INSERT Waiter H. Stulen, North Caldwell, NJ., assignor to Baldwin-Lima-Hamilton Corporation, Philadelphia, 2a.,

a corporation of Pennsylvania Filed Aug. 28, 1962, Ser. No. 219,917

23 Claims. (CI. 7241) This invention relates to an extrusion apparatus, and more particularly to an extrusion apparatuswherein the extrusion die is provided with a removable insert.

A-substantial amount of time, effort and money has been expended within recent years in order to explore the concept of using a ceramic or cermet insert in an extrusion die. As a result of all of this research which has been conducted heretofore, the conclusion of all parties associated with the project was to the effect that ceran'iic or cermet inserts at the throat of an extrusion die orifice is not practical due to the low tensile strength of the insert.

It has been recognized heretofore that an extrusion die having a ceramic insert at the throat of the orifice is desirable. A die having such an insert would enable extrusions to have a smoother finish, extrusions may be accomplished-at higher temperatures, and the life span of the die would be substantially increased. While all of the evidence heretofore indicates that ceramic inserts in an extrusion die are impractical, I have found that the main stumbling block, namely the low tensile and impact strength of the ceramic, can be avoided in a manner which is simple, inexpensive and reliable.

In the extrusion apparatus of the present invention, the extrusion orifice ofthe die is the inner diameter of an annular ceramic or cermet insert. The insert is mounted in a well in the die. The diameter of the well is slightly greater than the diameter of the insert so that an annular chamber having a width of between about .003 inch to .007 inch is provided between the walls defining the well and the outer diameter of the insert. Means are provided to facilitate the introduction of a movable medium such as a lubricant, insulating fluid, etc., into a low pressure zone on the land of the die adjacent the well. At the end of the stroke where the flowing metal approaches zero velocity, such flowing metal applies a pressure to the medium so that the forces exerted in a radial direction on the insert during the instantaneous approach to zero velocity of the flowing metal are balanced. U r

The introduced medium into the low pressure zone on the land of the die or in the container assembly liner ad: jacent the die facilitates the introduction of a lubricant during the extrusion process notwithstanding the fact that pressures with-in the container assembly may approach 150,000 pounds per square inch when extruding steels. Since the lubricant medium is introduced into a low pressure zone, it may generally be pumped thereint-o at a pressure below 400 pounds per square inch. In order to preventthe flowing metal from bypassing the die orifice as the flowing metal approaches zero velocity at the end of the extrusion stroke, the conduit system for conveying the lubricant medium to the die is provided with a line condition responsive valve which automatically closes. Since the lubricant medium is incompressible, or substantially so, the flowing metal will not enter the low pressure 3,191 ,413 Patented June 29, 1965 zone notwithstanding the fact that the flowing metal is free from laterally restrictive forces in the low pressure zone.

It is an object of the present invention to provide a novel apparatus and method for extruding materials.

It is another object of the present invention to provide a novel apparatus and method for extrusion of hard materials such as steel, stainless steel, titanium, etc.

It is another object of the present invention to provide an extrusion apparatus wherein the die is provided with a ceramic or cermet insert at the orifice.

It is still another object of the present invention to provide a novel extrusion die wherein the orifice thereof is formed by a ceramic or cermet insert.

It is a still further object of the present invention to provide a novel extrusion apparatus or method wherein the radial compressive forces on a die insert are substantially balanced.

It is still another object of the present invention to provide a novel extrusion apparatus or method wherein an extrusion die is provided with a low pressure zone adjacent the outer periphery of a die insert to facilitate the ease with which an extrusion process may be accomplished and to facilitate the flow of a medium between the die and the insert to equalize radial pressures on the insert as flowing metal approaches zero velocity.

It is yet another object of the present invention to provide a novel die for use in an extrusion apparatus or method.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a top plan view of an extrusion apparatus in accordance with the present invention.

FIGURE 2 is a longitudinal sectional view of the container assembly illustrated in FIGURE 1.

FIGURE 3 is a partial sectional view similar to FIG- URE 2, but illustrating another embodiment of the present invention.

FIGURE 4 is a sectional view of a die in accordance with another embodiment of the present invention.

FIGURE 5 is .a partial sectional view of the die in FIG- URE 4 as the flow metal reaches 'zero velocity.

Referring to the drawing in detail, wherein like numerals indicate like elements, there is shown in FIGURE 1 an extrusion apparatus designated generally as 10.

The extrusion apparatus 10 includes a container assembly 12 having a bore therein which is adapted to receive a reciprocably mounted stem 14. Stem 14 is provided with a dummy block 16 and a removable mandrel 18. The stem 14 is supported by a crosshead 20 and is connected to .a piston or ram disposed within the main cylinder 22. Whenthe stem 14 is' caused to reciprocate to the left in FIGURE 1 under the pressure in the cylinder 22, the crosshead 20 is guided and supported by

guide members

24 and 26.

The container assembly 12 includes a cylindrical liner 28 having a main bore 30. As shown more clearly in FIGURE 2, the main bore 30 is provided with an enlarged diameter portion 32 at the lefthand end thereof. A reduced diameter portion of a die 34 is received within the portion 32 of the liner 28. Means, not shown, will be provided to maintain the relationship between the die 34 and liner 28.

. The inlet side of the die 34 is provided with a converging land 35 which applies a radially constrictive force on the material to be extruded thereby directing the same toward the extrusion orifice 37. The extrusion orifice 37 is backed up by

relief bores

38 and 40.

The die 34 is provided with a well 42 concentric with the

bores

38 and 40. The diameter of well 42 is greater than the diameter of bore 38 thereby providing a radially outwardly directed shoulder 44. A die insert 46 is disposed within the well 42 and is in abutting contact with the shoulder 44. The extrusion orifice 37 is the inner diameter of the insert 46.

The insert 46 is provided with a converging land 48.

The difference in the angle of convergence of lands 36 and.

48 results in a rapidly changing contour of the surface exposed to the flowing metal thereby providing an annular low pressure zone 50. The outer diameter of the insert 46 is smaller than theinner diameter of the well 42 thereby resulting in an annular zone having a width of between .003 inch and .007 inch. .This annular zone is in communication with the low pressure zone 50.

A means is provided to facilitate the introduction of a medium such as a lubricant, a separator material, etc. into the low pressure zone 50. Such means includes flow passages 52 and 54 which extend through the die 34. Conduit 56 is in communication with passage 52 to facilitate the introduction of a medium thereinto. Conduit 56 is preferably provided with a one-way line condition responsive valve such as check. valve 55. Conduit 58 is in communication with passage 54 to facilitate the introduction of a medium thereinto. Conduit 58 is provided with a one-way line condition responsive valve such as check valve 57. The purpose of valves 55 and 57 will be made clear hereinafter.

When making a solid extrusion, the mandrel 18 will be removed so that the stem 14 terminates in a dummy block 16 having an imperforate metal engaging face. When it is desired to produce a hollow extrusion, a mandrel 18 will be provided. Mandrel 18 may have an enlarged diameter portion 62 at the end thereof adjacent the dummy block 16. The rapid change in the diameter between portion 62 and the remainder of the mandrel 18 results in the provision of a low pressure zone 64. P35? sages 66 and 68 may be provided through thestem 14, dummy block 16, and portion 62 so that a medium may be introduced into zone 64. The low pressure zone 64 is an area at which the flowing metal laterally restrictive forces.

The operation of apparatus is as follows:

A billet or the like will be disposed within the liner 28. When the billet is a hard metal such as steel, the billet will be at a temperature approximating 2200 F. Pressure on the piston in cylinder 22 will cause the stem 14 and dummy block 16 to reciprocate to the left in FIG- URES 1 and 2 thereby exerting a substantial amount of pressure on the billet to cause the same to flow toward the die orifice. The flowing metal is designated as 60 in FIGURE 2. As the flowing metal 60 contacts the land 36, it is subjected to radially constrictive forces and its velocity is increased rapidly. Due to the velocity of the flowing metal 60, it does not enter the low pressure zone 50 but merely continues on to the throat of the orifice 37.

Since the flowing metal 60 is free of radially constrictive forces as it passes the low pressure zone 56 a lubricant or other medium may be introduced through the passages 52 and 54 to ease the extrusion of the metal 60 and/or protect the die. The medium introduced into zone 50 may be pressurized to a pressure as low as 400. pounds per square inch. Such medium flows into the space between the insert 56 and the axially extending wall of well 42. As the flowing metal 6i} approaches zero velocity at the end of the stroke, the flowing metal exerts will be free of a substantial amount of pressure on the medium in zone 50 and passages 52 and 54. The back pressure on the lubricant medium will close the valves 55 and 57 thereby preventing loss of the flowing metaL' When the hot extrusion metal contacts the lubricating medium such as grease, instant flashing and vaporization of the medium occurs since the flash point is well below the temperature of the metal and the resultant pressure of the medium exerts a radially inwardly directed pressure on the insert 46 which substantially equalizes with the pressure exerted radially outwardly on the insert 46 by the flowing metal 60 as it is being extruded. These actions are accomplished almost instantaneously as-the flowing metal approaches zero velocity.

Test run with ceramic die inserts have'indicated that the failure of the ceramic inserts took place at the end of the stroke. The provision of a means for equalizing the radial pressures on the insert 46 prevents failure of the insert in compression. The insert 46 may be f a material commonly referred to as a ceramic or a cermet. A ceramic is a clay bearing material capable of being fired. A cermet is a ceramic having metallic particles therein. I have obtained excellent results with an insert 46 made from aluminum oxide fired to 2750 F.

It will be appreciated by those skilled in the art that a wide variety of ceramic materials may be utilized for the die insert an. The body of the die'34 may be a metal, a ceramic, or a cermet. The medium introduced through the passages 52 and 54 to tr e low pressure zone 54 may include grease, flaked graphite, soapstone, mica, any one of a Wide variety of insulating materials, etc. At the end of the extrusion cycle, I have found it advisable to flow pressurized air through-conduits 5d and 58, passages 52 and 54 respectively, to the lowpressure zone 50 to clear the same prior to the next extrusion cycle.

The insert 46 will maintain the tolerances of the orifice 37 substantially longer than a conventional die. When the insert 46 shows indications of wear, it is capable of being readily replaced with another insert. The ability to substitute an inexpensive insert greatly reduces the cost incident to replacement parts subject to wear in an extrusion apparatus.

When it is desired to extrude a hollow extrusion 61, a mandrel 18 will be provided which may have a separate actuator in addition to being responsive to movement of stem 14. The manner in which the mandrel 18 pierces the billet thereby initiating the inner diameter of the extrusion 61 is conventional and need not be described in detail. When extruding a hollow member such as extrusion 61, the above description as to the operation in relation to the outer diameter of extrusion 61 occurs. Further, the flowing metal 60 as it passes the low pressure zone 64 is free of radially constructive forces on the inner diameter of the flowing metal. A lubricant or other medium may be introduced through passages 66 and 68 to the low pressure zone 64 thereby facilitating the ease with which the extrusion 61 may be produced and increasing'the life span of the surfaces of the tools which contact the flowing metal 60 during the extrusion process.

In FIGURE 3, there is disclosed another embodiment of the present invention wherein a die 34' may be substituted for the die 34. The die 34' is provided with a well 42'- concentric with bore 38'. An insert 46 made from a clay bearing material capable of being fired is disposed within the well 42' in the same manner as described above. The land 36 is provided with a low pressure zone '70 having a passage 54' in communication therewith as .described above.

The insert 46 is provided with a groove 72 on its outer peripheral surface to increase the width of the annular space between the periphery of the insert 46' and the axially extending surface of the well 42. This increase is necessitated by the high viscosity of certain lubricants or insulating mediums which are to be introduced into the low pressure zone 70. The high viscosity of these mediums requires the space into which they areto flow to be substantially greater than the figures mentioned above. When the space is increased so as to facilitate the introduction and flow of high viscosity mediums into the space between the insert 46' and the axially extending surface of the well 42', the insert 46' becomes too loose. The desired tightness of the insert within the well 42' is accomplished by the provision of the groove 72. The fact that the insert 46 or 46' may not be exactly concentric with the bore 38 prior to the commencement of the extrusion process is of no moment since the flow of the metal through the orifice in the insert 46 will automatically centralize the

insert

46 or 46.

As illustrated more clearly in FIGURE 3, the die orifice nee-d not be only the inner diameter of the insert 46 or a portion thereof, but may incude the bore 38'. In this case, bore 40' will be the only relief bore.

The liner 28 and the container there'around may be provided with a passage 74 which is in communication with a low pressure zone 76 formed at the intersection of surfaces defining land 36 and portion 32 of the bore 30. The introduction of a lubricating o1- insulating medium into zone '76 facilitates the ease with which the flowing metal 60 will flow across surface 36' thereby increasing the useful life of die 34. All other features, characteristics or operation of the embodiment illustrated in FIGURE 3 may be identical as that described above and therefore need not be described in detail.

In FIGURES 4 and 5, there is disclosed another embodiment of a die having a ceramiciinsert which may be substituted for the die and insert illustrated in FIG- URES 13. The die in FIGURES 4 and 5 is designated generally as 34" and is identical with die 34 except as will be made clear hereinafter.

The die 34" is adapted to be utilized in conjunction with a container assembly such as assembly 12, and a reciprocally mounted stem such as stem 14. The die 34" is provided with a converging land 36 which applies a radially constrictive force on the material to be extruded thereby directing the material toward the extrusion orifice. r r

The land 36 terminates at its most radially inwardly point in an axially extending bore 80. Die 34" is provided with a second axially extending bore 8 8 having a larger diameter than bore '80 and separated therefrom by a shoulder 82. A'die insert designated generally as 83 is reciprocally supported within the bore 88. Insert 83 is provided with an annular end face '84 juxtaposed to the shoulder 82. The outer peripheral surface of the insert '83 is spaced from the bore 88 thereby defining an annular channel 89 therebetween.

The corner of the die insert 83 adjacent endface 84 is provided with a plurality of serrations 90 which provide communication between the channel 89 and a low pressure zone resulting from the angular disposition of bore 80 and the converging land 92 on the insert 83. Insert '83 may be made of the same material as

inserts

46 and 46. Insert 83 is provided with a bore 94 constituting the orifice or throat of the die 34".

The insert 83 is provided with an end face 96 at the end thereof opposite from end face 84. A first backup ring 98 is provided within a third bore of the die 34". Backup ring 98 is recessed to receive a portion of the insert 83 and has a bore therethrough which functions as a relief for the orifice in insert 83.

Backup ring 98 is provided with an annular groove 100 on one face thereof and juxtaposed to the end face 96 on insert 83. The backup ring 98 is provided with a large annular groove 100 on the opposite face from that containing the groove 100. A plurality of passages 104 extend through the ring 98 providing communication between the

grooves

102 and 100. A conduit 106 extends through a portion of die 34" and is in communication with groove 102. A backup ring 108 maintains the backupjring 9 8 in the illustrated position.

The embodiment illustrated in FIGURES 4 and 5 functions in the same manner as the embodiments illustrated above except as will be made clear hereinafter. Immediately before initiating the extrusion of the materials, lubricant, coolant, or other flowable medium may be introduced through conduit 106, groove 102, passages 104, groove 100, channel 89, and serrations into the low pressure zone. a

The end face of the insert 83 will be juxtaposed to and abutting the shoulder 82 as a result of the pressure of the lubricant acting against the end face 96. The surface area on end face 96 which is subjected to the pressure of thelubricant is substantially greater than the surface area at the orifice subjected to the pressure of the flowing material which is being extruded. Any gases generated by contact between a lubricant and the flowing material may build up pressure. Such pressure will reciprocate the die insert 83 to the left in FIGURE 4 so that the elements assume the position illustrated in FIGURE 5. Such movementof the insert'83 interrupts the introduction of lubricant'or other medium into the low pressure zone. Hence, the insert 83 acts as a valve member. After the gases dissipate themselves, the com ponents will resume the position illustrated in FIGURE 4.

As the flowing metal reaches zero velocity, the pressure of the flowing metal on the insert 83 is greater than the pressure of the lubricant or flowable medium acting against end face 96. Hence, the insert 83 will reciprocate to the left thereby assuming the position illustrated in FIGURE 5. Also, the lubricant trapped in channel 89 will be pressurizedby the flowing material so that the insert '83 will be subjected to equalized or balanced radial forces. 1

The reciprocatory movement of the die insert 83 may be obtained by eliminating the shoulder 82, if desired. The flowing material will perform the function of shoulder 82 if the initial introduction of lubricant or other flowable medium is timed so as to occur at substantially the same time as the flowing metal contacts the land 36". Q Any one of the embodiments of the die and removable insert-of the present invention may be utilized on an inverse'extrusion press. Hence, the dies with their inserts will be supported by the moving ram instead of being stationary as illustrated. Either arrangement is considered to be within the scope of the claims set forth hereinafter. Hence, it will be seen that I have invented an apparatus and method wherein extrusion of hard metal such as steel as well as easy to extrude materials may be more easily accomplished as a result of the creation of low pressure, zones into which a lubricant 0r insulating medium may be introduced to coat the outer and/or inner surface of the flowing metal prior to and during the passage of the flowing metal through the die ori fice. The die orifice may be the inner diameter of an annular die insert made from a clay bearing material capable of being fired, and commonlyreferred to as a ceramic or cermet.

The die insert is structurally interrelated with the die so that compressive forces in a radial direction are substantially balanced at the end of the stroke when the flowing metal approaches zero velocity thereby preventing failure of the insert. A valve means is provided in the flow line for the lubricating or insulating medium to prevent the flowing metal from bypassing the die orifice. The die insert is capable of being readily removed and a new die insert may be substituted therefor. The simplicity and low cost of the apparatus and method of the present invention overcomes many disadvantages of the prior art while increasing the quality of the surface finish on the extruded parts, decreases the amount of ram pressure in the main cylinder, facilitates the extrusion of hard metals, increases the useful life of the die, facilitates the replacement of only the orifice hearing portion of the die thereby decreasing the cost of replacement parts, eliminates excess handling of ingots and extruded parts associated with the prior art, and facilitates the extrusion of metals at higher temperatures than those contemplated or practical with the devices proposed heretofore.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the inven tion. 7

I claim: '1. In an extrusion apparatus comprising a container assembly adapted to support a billet therewithin, a die means having an orifice, ram means associated with said assembly for applying pressure on a billet in the container assembly to force the billet to flow through said orifice, means for providing a low pressure zone wherein the flowing material of the billet is free of laterally restrictive forces, said die means having an annular die insert made from a clay bearing material capable of being fired, and means for introducing a flowable medium into said low pressure zone and around said die insert so that the flowable medium is between the periphery of said insert and the juxtaposed portion of said die means.

2. In an apparatus in accordance with claim 1 wherein the orifice of the die means is the inner diameter of the insert.

3. In anapparatus in accordance with claim 1 wherein said insert is a ceramic.

4. In an apparatus in accordance with claim 1 wherein said insert is a cermet.

5. In an apparatus in accordance with claim 1 wherein the outer periphery of said insert is provided with a radial: 1y inwardly directed groove adapted to be in contact with the flowable medium.

6. In an apparatus in accordance. with claim 1 wherein said die means has a radially inwardly converging land which causes the velocity of flowing metal to increase rapidly, and means providing a low pressure zone upstream of said land, and passage means extending through said container assembly into communication with said last mentioned zone to facilitate the introduction of a medium into said last mentioned zone thereby easing the flow of moving metal across said land.

7. In an extrusion apparatus comprising a container assembly, a die associated with said assembly in a manner so that material in said assembly will be caused to flow through an orifice of said die, said die having an insert, said orifice being at least partially defined by the inner diameter of said insert, and means for equalizing the radially applied forces exerted on the insert in a radialdirection at the end of an extrusion stroke wherein the flowing material approaches Zero velocity, said last-mentioned means including the provision of an annular space around said insert, and means for introducing a medium into said space,

8. In an apparatus in accordance with claim 7 wherein said insert is provide-d with a radially inwardly directed groove on its outer peripheral surface thereby increasing the width of the portion of said space.

9. In an apparatus in accordance with claim 7- wherein said insert is made from a clay bearing material capable of being fired.

10. Apparatus in accordance with claim 7 wherein said insert is reciprocally supported by said die for movement in an axial direction with respect to said container assembly.

11. Apparatus in accordance with claim 7 wherein said insert is reciprocally supported by said die for movement in an axial direction with respect to said space, and means including said insert for controlling flow of the medium into said space.

8 12. An article of manufacture comprising a die adapted to be utilized in conjunction with an extrusion apparatus, said die having a bore therethro-ugh, said die having an annular well substantially concentric with said bore, a removable insert in said well, said insert being annular, the inner diameter of said insert forming the orifice of said die, and the outer periphery of said insert being spaced from an axially extending surface of said well by a distance of at least .003 inch, and means facilitating the introduction of a flowable medium therebetween whereby the radially applied-forces on the insert may be balanced.

13. An article in accordance with claim 12 wherein said insert is made from a clay bearing material capable of beingfired.

14. An article in accordance with claim 12 wherein said insert is provided with a radially inwardly extending groove on its outer peripheral surface.

15. An article in accordance with claim 12 wherein said insert is reciprocally supported by said die for movement in an axial direction with respect to said annular well.

16. An article in accordance with claim 15 including a flow passage in said die, said'flow passage being radially inwardly from the outer peripheral surface of said insert, one end of said passage being in communication with the space between the outer periphery of said insert and the axially extending surface on said well in one reciprocatory position of said insert, and said insert interrupting communication between said last mentioned space and said passage in another of its reciprocatory positions.

17. An article in accordance with claim 12 including a land on said die converging toward said orifice, a low pressure zone on said land, and at least one passag extending through the die in communication with said low pressure zone.

18. In an extrusion method comprising the steps of providing an extrusion die with a removable insert, forcing material to flow through an orifice of the die partially defined by a surface of the insert, and balancing the radially applied forces'on the insert at the end of the extrusion stroke as the flowing metal approaches zero velocity, said balancing step including transmitting the pressure of said material through a flowable medium to an outer peripheral surface of said insert.

19. In an extrusion method comprising the steps of providing an extrusion die with a removable insert, forcing material to flow through an orifice of the die partially defined by a surface of the insert, and balancing the radially applied forces on the insert at the end of the extrusion stroke as the flowing metal approaches zero velocity, said balancing step includes transmitting the pressure of the metal to the outer periphery of the insert by way of a substantially non compressible flowable medium,

20. In an extrusion method comprising the steps of providing an extrusion die with an annular insert having an orifice, heating material whose cross sectional area is greater than the cross sectional area of said orifice, forcing the heated material to flow through the orifice, and transmitting the pressure of said material through a fiowable medium as it is flowing toward the orifice to the outer periph'e'ry of said insert for balancing the radially applied forces on the insert at the end of the extrusion stroke as the flowing material approaches zero velocity.

21. In a method in accordance with claim 20 including the step of relieving the flowing material of laterally constrictive forces and applying a flowable medium to the flowing material at the point where the flowing material is free from laterally restrictive forces, thereby easing the extrusion of the material through the orifice.

22. In an extrusion method for extruding hollow metals comprising the steps of providing a container assembly adapted to support a heated billet, providing an extrusion die with a removable ceramic insert having an orifice in communication with the interior of said assembly, piercing the billet with a mandrel, forcing material to flow through the orifice and around a mandrel extending through the orifice, and balancing the radially outwardly directed forces on the insert at the end of the extrusion stroke as the flowing metal approaches zero velocity, said balancing step including transmitting the pressure of said material through a fiowable medium to the outer periphery of said insert.

23. In a method in accordance with claim 22 including the step of relieving the flowing metal of radially inwardly and outwardly restrictive forces over an annular portion of the periphery area thereof, and introducing a lubricant into said areas.

References Cited by the Examiner UNITED STATES PATENTS Wallace 20710 McTear 205--26 Schultz 207-17 Simons 207-l7 Ridgway et a1 205-26 Stulen 207--17 Ryshkewitch et al 106-44 Altwicker 20717 MICHAEL V. BRINDISI, Primary Examiner,

CHARLES W. LANHAM, Examiner.

Claims

1. IN AN EXTRUSION APPARATUS COMPRISING A CONTAINER ASSEMBLY ADAPTED TO SUPPORT A BILLET THEREWITHIN, A DIE MEANS HAVING AN ORIFICE, RAM MEANS ASSOCIATED WITH SAID ASSEMBLY FOR APPLYING PRESSURE ON A BILLET IN THE CONTAINER ASSEMBLY TO FORCE THE BILLET TO FLOW THROUGH SAID ORIFICE, MEANS FOR PROVIDING A LOW PRESSURE ZONE WHEREIN THE FLOWING MATERIAL OF THE BILLET IS FREE OF LATERALLY RESTRICTIVE FORCES, SAID DIE MEANS HAVING AN ANNULAR DIE INSERT MADE