US2974790A

US2974790A - Cross-extrusion process

Info

Publication number: US2974790A
Application number: US707340A
Authority: US
Inventors: John F Murphy; Stulen Walter
Original assignee: Curtiss Wright Corp
Current assignee: Curtiss Wright Corp
Priority date: 1958-01-06
Filing date: 1958-01-06
Publication date: 1961-03-14
Anticipated expiration: 1978-03-14

Description

March 1961 J. F. MURPHY ETAL 2,974,790

CROSS-EXTRUSION PROCESS Filed Jan. 6, 1958 INVENTORS .JEIHN F. MURPHY WALTER EITLILEN A TORNEY CROSS-EXTRUSION PROCESS John F. Murphy, Snyder, N.Y., and Walter Stulen, North Caldwell, N.J., assignors to Curtiss-Wright Corporation, a corporation of Delaware Filed Jan. 6, 1958, Ser. No. 707,340

1 Claim. (Cl. 207-2) This invention relates to metal forming and is particularly directed to a method and apparatus for extruding metal and to the extruded metal produced thereby.

Metal may be extruded directly from east ingots of a particular metal or from billets forged as by rolling from ingots of said metal. In the case of an ingot, when the ingot cools and solidifies from its molten state the outer portions of the ingot cool first and the central core is last to cool and solidify. This radially inward cooling of a metal ingot, particularly in the case of certain alloys results in a non-uniform distribution of its constituents and/ or other non-uniform internal metallographic structure. Thus, a cast cylindrical ingot generally has a non-uniform internal metallographic pattern across the ingot whichpattern runs axially through the ingot. Such non-uniformityor lack of homogeneity in ingots generally is known as segregation. When aningot having a non-uniform internal metallographic pattern' is forged, this non-uniformity causes so-called flow lines to .be produced in the resulting billet. Thus a'rolled .billet will have axial flow lines running through the billet. .Hence billets forged from ingots having a non-uniform internal metallographic pattern likewise have a nonuniform internal metallo'graphic pattern. i Any non-uniform internal metallographic pattern results in the metal being anisotropic. That is the physical properties of the metal are different in difierent directions. For example the fatigue strength and'ductility of a rolled billet generally are greatest in the direction of its flow'lines and are a minimum at right angles to said flow lines.

In conventional extrusion of metals, a metallic blank, which may be a metallic ingot or billet of cylindrical shape, is heated to its proper temperature for extrusion and is placed in a cylindrical chamber of an extrusion press having a co-axial extrusion die opening at one end, the-cross section of vthe die opening being similar to that desired of, the extruded metal. Pressure is'applied axially 1c the other end of ;the blank to force the metal axially .out through said die opening. With such axialextrusion, if the above diescribedusual anistropy exists in the original ingot or billet itwill at least to. some extent alsojappear in the extruded metal.

An object of the -present invention comprises the provision of; a novel, extrusion method and/or apparatus whereby anisotropy in the extruded metal is minimized. A further lobjectof theinvention comprises the .pro- .vision of a novelextrusion procedure such vthat the extruded metal, flow through the extrusion die opening 2,974,790 Patented Mar. 14, 1961 Fig. 2 is a sectional view of extrusion apparatus embodying the invention;

Fig. 3 is an enlarged sectional view illustrating the extrusion die opening and adjacent portion of the extrusion press, this view being taken along line 3-3 of Fig. 2 but with the extrusion press empty of metal to be extruded;

Fig. 4 is an enlarged sectional view taken along line 4-4 of Fig. 2; and

Fig. 5 is a sectional view taken along line 55 of Fig. 2.

Referring to the drawing, reference numeral 10 designates a cylindrical metal blank to be extruded, the size 'of the blank is such as to fit in the cylindrical container 12 of an extrusion press 14 (Fig. 2). In Fig. 2 the blank is already partly extruded. The blank 10 may be an ingot or a billet having, as is common and described above, a non-uniform metallographic pattern across the blank which runs generally in an axial direction substantially through the blank. Before the blank is placed in the extrusion press 14 it preferably is preheated in air or in a suitable salt bath. In the case of steels and heat and corrosion resistant alloys this preheat temperature may be fi'om 14O0 F. to 1800 F. The metal blank 'is then heated to a temperature satisfactory for extrusion I preferably by soaking the blank in a bath of molten glass maintained at said temperature. For example in the case of a blank having a composition of steels or other heat and corrosion resistant alloys the blank is heated to a temperature of about 2300" F. The molten glass not only heats the blank 10 to the extrusion temperature butvit also acts to dissolve any oxides from the surface of the blank thereby providing a scale-free surface. Although heating in molten glass is preferred other means may be used to heat the blank to 2300 and at the same time provide the blank with a scale-free surface'for example by heating the blank in a reducing atmosphere.

. .Upon removal from the molten glass bath, excess glass is scraped from the blank so as to leave a thin layer 16 of glass, preferably of the'order of% of an inch thick, over the entire surface of the blank. This molten layer or coating of glass protects the surface of the blank from oxidation during the subsequent extrusion of the blank and said layer of glass also functions as a lubricant for the extrusion die as the metal is being extruded through said die.

In lieu of using molten glass as the lubricant coatings of other lubricants, such as graphite or a graphite aluminum mixture, may be applied to the surface of the blank :10 after it has been heated to its extrusion temperature. i

The blank 10 is now ready to be placed in the extrusion press 14 which prior thereto has been preheated to approximately 400 -600 F. This temperature-should be accurately controlled.

The ram 18 of the extrusion press 14 is then retracted from oneend, of the extrusionpress container 12 and the heated blank 10 with its molten glass layer 16 (or other lubricant coating) is placed within said container. The other end of the cylindrical extrusion press container 12 [is closed by a cylindrical ejector member '19. The extrusion press container has an internal liner 20 and a block 22, providing an exn'usion die opening, is mounted in said liner. The extrusion die block 22 is mounted adjacent "to but slightly spaced from the ejector member end of'the extrusion press container 12 and is disposed so that the axis of its opening is directed at right angles to and intersects the axis of the cylindrical extrusion press container 12. I

The inner surface of the die block 22 preferably is flush with inner wall of the container as indicated in Figs. 2

3 and 3 whereby said inner die block surface is. cylindrical... Cast stellite has proved satisfactory for the die block 22. The inner cylindrical surface of the dieblock, which is flush with the inner wall of theextrusion press container, preferably is left in its as-cast conditionwhereby the slight irregularities in said surface function astraps or reservoirs for retaining molten glass lubricant on this surface. The die block 22 is held in position by a breech block 24 having an opening 26 for passage of the extruded metal. 1.

Upon the application of sufiicient pressure on the blank by the ram 18, the metal is extruded as indicated at 30 extruded metal 39 enters a tubular extension 32 of a coiling mechanism '34. The coiling mechanism 34 intangentially and at a small angle to the reel axis so that themetal readily enters the channel 40 of the reel 38.

Means are provided for supplying an inert gas, such as argon, through a passage 42 into the coiling mechanism- 34 in order to minimize oxidation of the extruded metal 30 as it cools from the extrusion temperature.

A suitable stop block 44: is provided to limit motion of the ram 18 into the extrusion press container. After completion of the extrusion stroke of the ram 18 it-is withdrawn from the extrusion press. The ejector member 19 is then raised to shear off the un-extruded metal remaining through the extrusion opening of the die block 22; The 1 in the extrusion press container 12 from the extruded metal in the extrusion die 22. The ejector member 19 is raised sufiiciently to permit removal of said un-extruded metal from the extrusion press container 12 A handle (not shown) preferably is providedpn the structure of the extruded metal beingv more uniform or homogeneous than it would be if the metal were extruded in the conventional manner axially through an extrusion die opening at the bottom of the extrusion press. Because of the greater homogeneity obtained in the extruded products with the extrusion-process and apparatus of this invention there will be less variation in the physical properties of such extruded products-as aresult of differences in the flow lines and/ or segregation in the startingblanks. 7 As illustrated, the surface of the ejector member 19 forming the bottom wall of the extrusion press container .12 is convex as viewed from within said container. [It has been found that this feature is important forobtaining a homogeneous extruded product possibly because it minirm'zes axial flow of the metal from the ejector member end of the extrusion press container toward the extrusion die 22. Similarly the inner surface of the ram 18 preferably is made convex as viewed from within the extrusion ing Wire for aircraft engine valve springs. This invention is particularly useful for extruding metals where a-high degree of homogeneity is desired in the finished product.

While We have described our invention in detail in its present preferred embodiment, it will be obvious to those skilled in .the art, after understanding our invention that various changes and modifications may be made therein :without departing from the spirit or scope. thereof. We

'aim in the appended claim to cover all such modifications.

, .We claim as our invention:

.Apparatus for'- the extrusion of metals comprising: a

stationary billet container having a cylindrical cavity 7 therethrough. for accommodating a previously prepared the cylindrical metal blank for extruding the metal transversely through the extrusion die 22. With this specific cross-extrusion process the molten glass layer 16 about the metal blank appears to flow more readily to'the extrusion die to function as a lubricant for said die as the extrusion proceeds than itwould for example if the-metal were extrudjed' axially through an extrusion die at the bottom of the extrusion press container 12. This would also be true ifanother lubricant layer were used in the extrusion press 14 about the blank 10 in lieu of said molten glass layer 16.

With cross-extru sion'out through a lateral extrusion die opening, the metal apparently flows primarily from the center of the metal blank laterally to the extrusion die whereas with the conventional type of extrusion through an axial die opening the metal. apparently flows to a greater extent from theblank surface to the extrusion die opening. Unless an inert atmosphere isuse'd, the surface of the blank in the extrusion press is subject to oxidation and therefore with saidconventional extrusion practice" the extrusion 'die is subject to greater wear from contact metal billet, said container having anopening through the: wall thereof 'near one of said containers ends; an

which latter is a sliding fit within said cavity, said seating'portion, when seated, holding said convex portion below said die but stillcl osingthe lower end of'said cavity; means for moving said ejector member in a direction up and along the axis of said cavity'toeject an extrusion renma'nt. therefrom; anextrusion ram'which is a sliding fit in said cavity, said 1 am having'a convex end similar to and opposed to the "convexend on'said ejector;

- means 'to move said ramback and forth'along said axis;

with metal oxides. Anotheradvantage of the lateralc'ross the. usual. non-uniform .metallpgraphicpattern' running through it from substantially one end towardlthe' o ther,

cross extrusion results in the 'internal' metallog'raphic whereby, when said rain compresses a billet agains'tfsaid ejector, said billet will extrude'through' said orifice and (Other reference's' page) 5 UNITED STATES PATENTS Mereta Dec. 15, 1908 Mitchell Aug. 28, 1928 Summey Dec. 17, 1929 Deibel May 18, 1937 Farr et a1. May 28, 1946 Sejournet et a1 Apr. 26, 1955 Krit-scher Jan. 17, 1956 Boccon-Gibod et a1 July 24, 1956 Metalworking Lubricants, by E. L. H. Bastian,

6 FOREIGN PATENTS Germany Mar. 16, 1933 France Apr. 5, 1938 Great Britain Nov. 22, 1950 Australia Apr. 11, 1956 OTHER REFERENCES McGraw-Hill Book Co., Inc., 1951, pp. 281-282.