US3034642A - Extrusion of metal - Google Patents

Description

A. B. GRAHAM EXTRUSION OF METAL May 15, 1962 2 Sheets-Sheet 1 Filed Aug. 4, 1958 ALEXANDER B. GRAHAM INVENTOR.

ATTORNEY y 1 1962 A. B. GRAHAM 3,034,642

EXTRUSION 0F METAL Filed Aug. 4, 1958 2 Sheets-Sheet 2 w LTLH% n IO C :3 f m 0) N 2 LL ALEXANDER B. GRAHAM INVENTOR.

ATTORNEY 3,034,642 EXTRUSION F METAL Alexander Barbour Graham, Whitecraigs, Glasgow, Scotland, assignor to The International Nickel Company, lino, New York, N.Y., a corporation of Delaware Filed Aug. 4, 1958, Ser. No. 752,334 Claims priority, application Great Britain Oct. 11, 1957 2 Claims. (Cl. 207-9) The present invention relates to extrusion of metal, and more particularly to a special extrusion die and apparatus for extruding hard, refractory metals and/or alloys, to improve the quality of the extruded surface thereof and to a process for accomplishing the same.

As is well known to those skilled in the art, relatively soft metals and alloys such as aluminum, tin, lead, zinc, brass, etc., generally can be extruded with facility in accordance with modern techniques. However, extrusion of hard, refractory, difiicultly workable metals and/or alloys presents problems not normally encountered in extruding the comparatively soft metals such as those enumerated above. For example, the hardness of refractory metals, e.g., nickel alloys, necessitates the utilization of extremely high pressures, e.g., over 100,000 pounds per square inch (p.s.i.) being not uncommon, and temperatures, e.g., 900 C. (1652 F.) to upwards of 1300 C. (2372 F.), in order to achieve the necessary state of plasticity for deformation of the material during extrusion, A a consequence of such high pressures and temperatures, there is undue wear on the dies necessitating frequent replacement and the extruded pieces have been prone to exhibit surface defects.

One of the primary surface defects characteristic of extruded hard, refractory metals and/or alloys is oxide scale. As a consequence of the hot working procedures employed to bring the metal to extrusion temperature, the metal is in a condition in which it is inherently prone to the development of surface oxides. Of course, such oxides must be removed from the extruded piece and it is not difficult to appreciate the significant loss of metal incurred in removing the oxides, particularly when it is considered that extrusion ratios of 40 or 60 to 1 are not uncommon in practice. Moreover, the severe extrusion pressures exerted tend to promote a deeper penetration of the contaminating oxides inward of the longitudinal axis of the extruded piece which necessitates removal of a section of greater thickness than might be the case in other metallurgical operations. The removal of surface oxides from the extruded product is not a simple task and often requires expensive and tedious operations, e.g., scalping, chipping, grinding, turning, etc.

Heretofore, the art has endeavored to obviate the problem by recourse to elaborate and varied precautionary measures directed to the prevention of the formation of surface oxides prior to the extrusion operation. For example, during the course of pro-heating a billet of hard, refractory metal furnace temperatures and atmospheres are carefully controlled. Such procedures entail the use of special and sensitive apparatus to insure, for example, the provision of a reducing atmosphere in the furnace. Special furnaces, e.g., low frequency induction furnaces, h ve also been proposed to meet the problem. Even with the use of such costly procedures or special apparams, the metal too often exhibits surface oxide defects immediately prior to extrusion. When the metal billets are shaped by extrusion, the oxidized surface layers and other surface defects on the billet cause defects to appear on the surface of the extruded product and cause increased die wear. If the metal to be extruded is soft, e.g., brass, this drawback of surface oxide contamination is commonl avoided by using a ram which cuts through the metal and leaves a thin stocking of the billet metal in the extrusion container, the oxidized layers and surface defects being in this stocking. If, however, the metal is of a hard refractory nature, this conventional method is not practicable, as the rim on the ram will not withstand the wear involved.

Although many attempts were made to overcome the foregoing difliculties and other disadvantages, none, as far as I am aware, was entirely successful when carried into practice commercially on an industrial scale.

It has now been discovered that billets or ingots of metal and/or alloys, particularly hard, refractory metals and/or alloys, having surface defects such as oxide scale can be extruded such that the extruded product is characterized by markedly improved surface qualities through the utilization of a novel extrusion die having special structural features.

It is an object of the present invention to provide an extrusion process for improving the surface quality of the extruded product.

Another object of the invention is to provide a novel extrusion die of special configuration for enhancing the surface quality of the extruded metal and/ or alloy.

The invention also contemplates providing an extrusion process and die of special structure for improving the surface quality of extruded hard, refractory metals and/ or alloys.

It is a further object of the invention to provide an extrusion process and die which remove surface defective metal from and impart improved surface qualities to the metal extruded. The invention further contemplates an extrusion apparatus for accomplishing the foregoing.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is an axial sectional view through an illustrative extrusion press featuring the special die structure of the invention; and

FIGURE 2 depicts a section similar to FIGURE 1 showing a different working position.

Generally speaking, the present invention contemplates a die of novel structural configuration and a process and apparatus for extruding metals and/or alloys, particularly hard, refractory metals and/or alloys, having surface defects, e.g., oxide scale. In accordance with the invention, the skin of the billet to be extruded and which contains the surface defects is extruded simultaneously but apart from the desired product. This is accomplished by providing a second die surrounding the first to leave a continuous narrow annular space at the end of and just inside the wall of an open end container. The dies are correlated structurally to cooperatively form a continuous and uninterrupted annular orifice substantially concentric to the product die orifice and adapted to remove the surface skin from the billet or ingot during the extrusion thereof. It is most advantageous that the internal radius of the wall of the annular orifice be substantially the same as the interior wall of the extrusion container or chamber to thereby form therebetween an uninterrupted surface.

In accordance with the invention, hard, refractory metals including nickel, chromium and cobalt and alloys thereof such as nickelchromium alloys, nickel-chromiumiron alloys, nickel-chromium-cobalt alloys, cobalt-chromium alloys, stainless and heat-resisting steels, etc, having surface defects, e.g., oxide scale, can be satisfactorily extruded.

For the purpose of giving those skilled in the art a better understanding of the invention and/or a better appreciation of the advantages of the invention, reference is now made to the drawings which illustrate, by way of example, a preferred embodiment of the extrusion die assembly in operation in accordance with the invention.

Referring to FIGURE 1, there is shown a cylindrical Patented May 15;, 1962 billet B inserted in a cylindrical open end container 1 of an extrusion press. The container 1 is surrounded by a housing 2 which is in contact with a second housing 3. At the forward end of the container there is a circular product die 4 with a central opening and an annular die 5 which surrounds the die 4 and, as shown, is of the same internal radius as the container 1. It will be noted that the substantially concentric die structure, as described, provides a continuous and uninterrupted annular scalping orifice 25 through which the surface defective skin of the metal to be extruded passes. Moreover, since the internal radius of the annular die is the same as the radius of container 1, there is provided an uninterrupted and smooth passage wall for extruding the skin 14 which, as mentioned hereinbefore, is advantageous for achieving highly satisfactory results.

The die 4 is carried by a holder 6 which, as shown, is bolted to an annular block 7 which lies in a circular opening in the housing 3. The coupling between the die 4 and the holder 6 is shown by way of illustration as the breech-block type and is made or broken by relative rotary movement of the holder and die.

Annular die 5 is held in position in a recess in the housing 2 and against the container 1 by an annular plate 8 which is bolted to the housing 2.

The block 7 is engaged by and can be moved axially by a tube 21 operated by, for example, hydraulic means. When block 7 is in the operating position shown, it is held by two opposed blocks 9 slidable into and partly out of cylinders 10 in the housing 3.

The two dies 4 and 5, the plate 8, the block 7 and the holder 6 are shaped to form an annular cavity or passage 11 in communication with the annular space (orifice) between the dies. Preferably, the annular passage 11 has a closed end, i.e., is a blind passage, as shown in FIGURE 1. Communicating passage or cavity 11 can be advantageously of frustro-conical configuration, as shown, although other suitable configurations may be employed.

When the billet is forced to the left as, for example, by ram 12, some of the metal is forced through the die 4 to emerge as the desired extruded product 13, and the skin 14 of the billet passes through the annular opening (orifice 25) between the dies 4 and 5 into the blind cavity 11. The free end of the skin metal can strike the blind end of the cavity or passage and buckle more or less as shown at 15 if the original billet is long. This advantageously provides for extruding relatively long billets and eliminates otherwise premature disassembly of the apparatus.

At the end of the extrusion operation the blocks 9 supporting the block 7 are withdrawn at right angles to the line of extrusion. The whole assembly of the block 7, holder 6 and die 4 can be withdrawn by operation of the tube 21. There is, of course, some of the original billet still in the container 1 as a discard 16, and if this should be wedged in the container the main ram 12 may also be used to assist the movement from the position shown in FIGURE 1 to that shown in FIGURE 2.

It is a further advantageous feature of the invention that the discard 16 and the skin 14 which is attached to it can both be readily disposed of while simultaneously separating the extruded product therefrom in a single operation. This is achieved by gripping the discard in a double-acting vise, each jaw 17 being operated by suitable means such as a hydraulic ram. Next the die assembly is moved back while the discard is still held by the vise, and then a circular saw 18 driven by a motor 19 carried by a support 20 is brought into action. The support 20 is guided to slide and is moved hydraulically inwards to cause the saw to cut through the skin 14 and the product 13.

In the application of the invention to heat-resisting and creep-resisting alloys such as those having a nickelchromium base, glass may be used as a lubricant, a pad of glass fiber being inserted between the billet and the die 4, and further glass fiber being interposed between the billet and the wall of the container 1.

The thickness of the skin 14 can of course be regulated by varying the width of the annular space between the dies 4 and 5 and by this means also the total extrusion ratio is varied. By thus reducing the ratio, it is possible to produce from a billet of given diameter a product of much smaller cross-sectional area than would be possible if the skin were not extruded through the outer annular orifice in accordance with the present invention.

The present invention is particularly applicable to the extrusion of billets and/or ingots made from hard, refractory and difficultly workable metals and/or alloys to produce products having improved surface character istics. The invention is also applicable to the extrusion of billets and/or ingots made from soft metals and/or alloys, e.g., lead, tin, aluminum, brass, etc., to provide extruded products having improved surface characteristics. In the extrusion of either type of metal, the invention provides the advantage that the annular skin of metal removed from the workpiece is easily removed from the product and no difiiculty is encountered in removing the skin from the extrusion tools. As mentioned hereinbefore, hard, refractory metals and alloys include the metals nickel, chromium and cobalt and alloys thereof such as nickel-chromium alloys, nickel-chromium-iron alloys, nickel-chromium-cobalt alloys, cobalt-chromium alloys, stainless and heat-resisting steels, etc. As is known, such alloys often contain relatively substantial amounts of other alloying elements such as, aluminum, titanium, tungsten, vanadium, molybdenum, columbium, silicon, manganese, etc. Copper, copper-base alloys, mild steel, etc., may also be satisfactorily extruded in accordance with the invention.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. For example, a plurality of product die orifices may be employed, if so desired. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

I claim:

1. An extrusion apparatus for extruding solid hard refractory metal while simultaneously extruding surface defects therefrom which comprises an open end extrusion container of constant internal diameter and adapted to receive metal to be extruded, a concentric die assembly at one end of the container and comprised of a die structure formed of an outer annular die and a substantially concentric axially movable inner product die maintained in fixed position during extrusion, the outer die being cooperatively positioned in concentric relationship to the inner die such that the inner wall of the outer die and the outer wall of the inner die form therebetween a continuous and uninterrupted annular die scalping orifice independent of the container and adapted to extrude surface-defective metal, said inner die and outer die being positioned outside the container with the outer die being separate from but in abutting relation with the container and having at the plane of abutment an internal diameter which is the same as the diameter of the inner wall of the container, an axially movable die holder in engagement with the inner product die, and an axially movable annular die block in engagement with the die holder and having an annular passage therein in communication with the annular die orifice to receive extruded surfacedefective material from the annular die orifice, whereby when hard refractory metal is extruded the surface defects thereof pass through the annular die orifice while the desired solid extruded product simultaneously passes through the product die.

2. An extrusion apparatus for extruding solid hard refractory metal while simultaneously extruding surface defects therefrom comprising, in combination, an open end container of constant internal diameter and adapted to receive metal to be extruded, a concentric die assembly at one end of the container and comprised of a die structure formed of an outer annular die and a substantially concentric axially movable inner product die maintained in fixed position during extrusion, the outer die being cooperatively positioned in concentric relationship to the inner die such that the inner wall of the outer die and the outer wall of the inner die form therebetween a continuous and uninterrupted annular scalping die orifice independent of the container and adapted to extrude surface-defective metal, said inner die and outer die being positioned outside the container with the outer die being separate from but in abutting relation with the container and having at the plane of abutment an internal diameter which is the same as the diameter of the inner wall of said container, an axially movable die holder in engagement with the inner product die, an axially movable annular die block in engagement with the die holder and having an annular passage therein in communication with said annular die orifice to receive extruded surface-defective metal from the annular die orifice, a holding device comprised of slidably opposed supporting blocks engaging the annular die block to substantially prevent relative movement between the die assembly and container during extrusion, a retractable member movable axially to the container and being in engagement with the annular die block and adapted to simultaneously withdraw the solid extruded product, the surface-defective material and discard metal to a position away from the container subsequent to the extrusion operation, a power device for withdrawing the retractable member to a desired position away from said container, a gripping device comprised of slidably opposed members for holding the withdrawn solid extruded metal, surface-defective metal and discard metal in a relatively fixed position, and a cutting device adapted to simultaneously separate the solid extruded metal from the surface-defective metal and from the discard metal in a single cutting operation.

References Cited in the file of this patent UNITED STATES PATENTS 796,223 Kaub Aug. 1, 1905 1,049,641 Astfalck Jan. 7, 1913 2,379,622 Butler July 3, 1945 2,630,220 Sejournet Mar. 3, 1953 2,674,373 Latin Apr. 6, 1954 2,720,970 Roux Oct. 18, 1955 2,773,283 Malamoud et a1. Dec. 11, 1956 2,832,468 Krause Apr. 29, 1958 FOREIGN PATENTS 271,378 Germany Mar. 11, 1914 535,847 Canada Ian. 15, 1957 552,423 Germany July 7, 1932 701,846 Great Britain Jan. 6, 1954 769,604 Great Britain Mar. 13, 1957 OTHER REFERENCES Mechanical Engineering, vol. 80, No. 3, March 1958, p. 217, pub. by ASME, 29 W. 39th St., New York 18, New York.

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