US 2900708 A
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Description (OCR text may contain errors)
Aug. 25, 1959 R. B. POND APPARATUS FOR PRODUCING ALLOY AND BIMETALLIC FILAMENTS Filed Feb. 16, 1956 APPARATUS FOR PRODUCING ALLOY AND BINIETALLIC FILAMENTS Application February 16, 1956, Serial No. 565,814
4 Claims. (Cl. 29-194) This invention relates to a method of producing metal fibers and filaments and, more particularly, to the produc tion of anisotropic filaments.
Anisotropic bodies, such as bimetallic filaments, wires and like bodies are generally formed by welding or cladding metals whereby the metals at their adjacent surfaces are brought to a sufliciently high temperature either with or without applied pressure to produce an interdifiusion of one metal into the surface of the other metal. The bond thus formed is sufficient to form a unitary body. Wires or filaments formed of an alloy, on the other hand, have a substantially uniform composition laterally across the body.
The term filament is used herein and in the claims to designate bodies or elements having a relatively great or indefinite length with respect to their transverse sectional dimensions.
One of the purposes of the present invention is to provide a method for the production of anisotropic metallic filaments.
Another object of this invention is to provide a method for the production of bimetallic filaments.
A further object of this invention is to provide metallic alloy filaments wherein the composition of the filaments varies transversely across the filaments.
Other objects and advantages of this invention will become apparent from the description and claims which follow.
In the accompanying drawings:
Figure l is a cross-sectional view of an ejector tube adapted for the practice of this invention;
Figure 2 is a cross-sectional View of a further embodiment of an ejector tube for the practice of this invention;
Figure 3 is a perspective diagrammatical view showing one form of means for forming metal filaments;
Figure 4 is a sectional diagrammatic view showing another embodiment of apparatus for forming filaments in accordance with this invention;
Figures 5, 6, 7, 8 and 9 are diagrammatic cross-sectional views of products formed in accordance with the present invention; and
Figure is a cross-sectional view of another form of ejector tube.
The method of the present invention contemplates joining or bringing together two or more streams of molten metals to form a single stream of molten metal and converting the stream into solid filaments. The present invention further contemplates an extrusion nozzle having separate ducts or channels for different metals, the ducts being so arranged as to bring together the streams of molten metal.
One embodiment of the products of this invention consist of filaments formed of two different metals which alloy with each other wherein the composition varies progressively in a direction transverse to the filament. In
rates Patent a second embodiment, the'filaments comprise two sepa- Patented Aug. 25, 1959 rate metals which do not alloy with each other but interdiifuse and adhere to each other.
As illustrated in Figure 1, there is provided a suitable ejector tube or cylinder 1 including a partition 2 adapted to contain the molten metals A and B and from which the molten metals are extruded under pressure. chamber may be in the nature of a crucible having heating means and the metals may be melted within the crucible or the molten metals may be supplied from crucibles 3 and 4. An extrusion die 5 formed of a suitable ceramic or other refractory material is removably mounted at one end of the chamber 1. The die is provided with extrusion ducts or orifices 6 and 7 each of which communicates with one of the chambers within the cylinder. The extrusion ducts may be of any desired size and are arranged at an angle so as to direct the streams of molten metal toward each other. The opposite end of the cylinder 1 is closed by means'o-f a rem'ovably mounted plate which is provided with gas ducts 8 and 9 which communicate with a source of gas under pressure. In the operation of the device, the molten metals are extruded by supplying gas under pressure. The streams of metal are joined or brought together while both metals are in a molten state.
The apparatus as shown in Figure 2 includes a like ejector tube or crucible 10 having a movable partition 11. The separate chambers may be supplied with molten metals A and B as described. The extrusion die 12 having an extrusion duct or orifice 13" communicates with the chambers of the cylinder through a conical throat 14. A truncated conical plug 15 is secured at the lower end of the partition 11 and is so arranged to extend into the throat 14 in the die. In order to provide a continuous stream of molten metal, the metals are extruded under pressure which may be supplied by a gas supplied to the conduits 16 and 17 in the closure for the cylinder. The molten metals thus flow from their respective chambers toward the extrusion orifice 13 through the ducts or channels formed between the throat 14 and the plug 15 and the molten metals are joined or brought together as they approach the extrusion orifice.
If it is assumed that the orifices 6 and 7 in the die 5 (Figure 1) are of the same size and if it is assumed that the partition 11 and plug 15 (Figure 2) are centrally disposed with respect to the die 12, equal volumes of the two metals will be brought together to form a continuous stream of molten metal. The stream of molten metal as provided by the apparatus of Figure 1 or Figure 2 may be converted into a solid filament by the method as disclosed in my copending application Serial No. 387,187, now Patent No. 2,825,108, issued March 4, 1958. The apparatus shown in my copending application is shown diagrammatically in Figure 3 of this application. The continuous stream of molten metal 18 is impinged on the concave surface of a rapidly rotating chill block or plate 19. The chill block is formed of a metal of a high heat conductivity and possesses sulficient mass or is provided with cooling means so as to dissipate the superheat and heat of fusion of metal as it impinges on the chill block. The molten stream of metal is transferred into a solid during the brief contact (as shown at 20) with the chill plate and a continuous filament 21 is cast off by the centrifugal force resulting from the rapid rotary motion of the chill block. The filaments as formed by this method have a more or less rectangular cross-section imparted as the stream of molten metal is converted into the solid form on the chill block. This method and type of apparatus for forming the molten metal into a solid filament is satisfactory for the non-refractory metals which do not have a high vapor pressure at the temperatures required for extruding them to form the continuous stream of metal. 1
In my copending applications Serial No. 563,541 and Serial No. 563,615, both filed February 6, 1956, there are disclosed methods and apparatus for transforming continuous streams of molten metal into filaments of any desired cross-sectional configuration from non-refractory metals. The apparatus of these applications are illustrated diagrammatically in Figure 4. The extrusion apparatus of the present invention may be utilized in this method and apparatus to form the filaments of two or more metals.
The ejector tube 22 is positioned at the top of a suitable tower 23 at the bottom of which there is disposed a suitable collecting box or truck 24. Gas conduits 25 and 26 communicate with the interior of the tower at the bottom and top, respectively. For metals which do not readily oxidize in air such as 'lead and tin, for example, the molten metal may be extruded in air. For metals which oxidize readily in air, the tower may be supplied with an inert gas such as nitrogen, helium or the like through conduits 25 and 26. Where the gas is heavier than air, the gas may be supplied to the tower through conduit 25 whereby the air is flushed from the tower at the top through conduit 26. For gaseslighter than air, the gas is supplied at the top of the tower through conduit 26 and the air flushed from the tower through conduit 25. In those instances where the metal has a high vapor pressure at the extrusion temperatures, the gas within the tower may be maintained under sufficient pressure to overcome the vapor pressure of the metal. In all instances, the pressure within the ejector tube 22 must be regulated to provide a continuous stream of molten metal leaving the extrusion cylinder and where the gas within the tower is maintained under pressure, the pressure in the ejector tube 22 must, of course, be greater than the pressure within the tower. For example, where one of the metals being extruded is zinc,
the gauge pressure within the tower may be maintained at about ten pounds per square inch.
In one embodiment where the two metals readily alloy with each other, for example, if the metal A is lead and the metal B is tin, the resulting filament will consist of an alloy. In view of the fact that the molten metals solidify in a very brief period of time, the composition will not be uniform transversely of the filament. If it is further assumed for purposes of illustration that a round filament is formed as shown in Figure by utilizing the apparatus of Figure 4, the composition on one side of the filament will be substantially entirely metal A or lead and on the other side the filament will be substantially all metal B or tin. The relative proportions of metals A and B in the alloy vary progressively across the filament because the time in which the two metals are in contact in molten condition with each other is not sufiicient to permit a thorough solution of one metal throughout the other metal. It will be understood, however, that where the combined stream of molten metals is very small, the product may not have edges or sides consisting of substantially pure metal but may consist of an alloy where the edges or sides are rich on one of the metals;
In another embodiment where the two metals do not readily alloy with each other but adhere to each other, the product will be a bimetallic filament as illustrated diagrammatically in Figure 6. One portion of the wire will consist of metal A and the other portion will consist of the metal B separated by an alloy zone or a boundary layer where there has been a slight diffusion of one metal into the other as indicated by the broken line 27.
In transforming the molten metal stream into the solid fiber by the use of apparatus as illustrated in Figure 3,
the filament 21 has a more or less rectangular cross-' section. The foregoing discussion 'with respect to the composition and structure of the filaments also applies to such rectangular filaments. It is-obvious that the variation of composition of these rectangular filaments may be varied depending upon the relative positions of the metals A and B as the combined molten metal stream impinges on the rotating chill block. Where, for example, the ejector tube is so positioned that the chamber containing one metal is above the chamber containing the other metal, the composition will vary across the minor cross-sectional axis of the filament. Thus, if the two metals do not alloy with each other and the chamber containing metal B is above the chamber containing metal A, the top portion of the filament would consist of metal B and the bottom portion consist of metal A. Where the ejector tube is so arranged that the chambers containing the two different metals are side-by-side in a horizontal direction, the filament would have the variatic'n in composition along its major cross-sectional axis.
The foregoing discussion has been based upon an assumption that the extrusion orifices 6 and 7 (Figure 1) are of equal cross-sectional area and that the plug 15 (Figure 2) is centrally positioned within the throat of the extrusion nozzle 12. Anisotropic or bimetallic elements consisting of a major proportion of one metal may be formed by varying the relative volumes of the metals which are extruded. For example, a product consisting of a major portion of metal B and a minor or skin portion on one side of the metal A as illustrated diagrammatically in Figure 7 may be formed by providing the extrusion nozzle 5 with an orifice 6 which is relatively small with respect to the extrusion nozzle 7 or by moving the plug 15 to the left side of the extrusion nozzle 12 of Figure 2. If the orifice 7 in extrusion nozzle 5 is of relatively small cross-section with respect to orifice 6 or if the plug 15 is moved to the right side of the nozzle 12, the product would be as represented by Figure 8 wherein the metal A constitutes the major portion of the filament and metal B, the minor portion. Where the metals do not alloy with each other but merely interditfuse to bond them together, the individual metals are separated by a boundary layer 27 as described hereinbefore.
These embodiments may be illustrated specifically, merely for the purposes of illustration, by reference to the production of filaments of lead and tin. The extrusion temperature may, for example, be about 350 C. which is roughly 20 above the melting point of lead and about above the melting point of tin. Where the apparatus of Figure 2 is employed to form the continuous stream of molten metal, the temperature must necessarily be above the melting point of the lowest melting metal. In the use of apparatus as shown in Figure l, partition 2 may be formed of a suitable refractory and insulating material so that the temperature of the lowest melting metal need not be about the same as that of the higher melting point metal. It is, however, necessary that the temperature of both metals be such that the streams of metal when they contact each other or become joined are both in molten state. The extrusion orifices 6 and 7 in the case of the apparatus of Figure 1 may be of a diameter of about 1.5 mils. For the apparatus as shown in Figure 2, the extrusion orifice may be about 2 mils in diameter. The pressure applied to the surfaces of the molten metals within the ejector tube may be in the neighborhood of about six pounds to about ten pounds per square inch (gauge) so as to form the continuous stream of molten metal. The rotating chill block may be formed of aluminum and may be about three inches in diameter. The chill or upper surface has a radius of curvature of about five inches and the angle at which the stream of molten metal impinges on the-chill block may be about 30. The resulting filament is a ribbon-like filament which may vary in thickness and width depending upon the velocity of the rotating chill block. At impingement velocities of 2 to 300 feet per second, the thickness is of the order of about 0.2. mil to about 0.4 mil and the width from about 15 to about 38 mils. The thickness may be decreased and the width increased by increasing the velocity of the chill block or the thickness may be increased and the Width decreased by reducing the velocity of the chill block.
Although the invention is illustrated specifically by reference to the production of lead-tin alloy filaments formed by the use of apparatus shown in Figure 3, the invention is not restricted to such products and apparatus or method. The lead-tin filaments also may be formed by the use of any other suitable apparatus such as that shown in Figure 4. Filaments may be formed in like manner of other alloys such, for example, as copper-nickel alloys, aluminum-zinc alloys and the like. Bimetallic filaments may be formed in like manner as described hereinbefore from combinations of metals such, for example, as copper-iron, aluminum-copper, aluminum-nickel, zinc-tin and the like. Where the alloys or one or both of the metals oxidize readily in air at the required extrusion or ejection temperature, the filaments are produced by the use of an inert atmosphere in apparatus of the type shown in Figure 4. Where one or both of the metals has a high vapor pressure at the required extrusion or ejection temperature, for example, in producing copper-zinc filaments, the filaments are produced by the use of apparatus as illustrated in Figure 4 and the gas in the tower or chamber is maintained under a pressure at least as high as the vapor pressure of the metal at the extrusion temperature.
In a further embodiment as illustrated diagrammatically in Figure 9, the composition of the filament varies radially along a transverse section of the filament; that is, the filament has a core 28 surrounded by a sheath 29. Where the metals do not alloy with each other, the metals will be separated by a boundary layer 30. In those instances where the metals alloy with each other, the center of the core may be composed entirely of one metal and the outer surface of the sheath composed of the other metal with progressively changing proportions of the two metals along the radius.
A further embodiment of apparatus of this invention particularly adapted for the production of filaments of this type is shown in Figure 10. The ejector tube or cylinder 31 comprises an outer crucible 32 and an inner crucible 33 mounted concentrically with respect to each other. The outer crucible is provided with a conical exit port 34 at one end and a closure at its other end. The inner crucible is formed with a closure at its upper end and a conical terminal end "35 having the desired size extrusion orifice. The slope or angle of the terminal end may be substantially the same as the slope of the exit port 34 so that the extrusion orifices for the two metals are at an acute angle with respect to each other. The inner crucible is preferably so arranged that it may be moved axially with respect to the outer crucible, thereby permitting a convenient means for regulating the thickness of the sheath. Suitable conduits are provided to introduce molten metal and to supply a gas under pressure to the crucibles as described hereinbefore. The operation of the apparatus is similar to that of the device illustrated in Figure 2. The molten metals are continuously extruded by the pressure of the gas and brought together as they emerge from the extrusion orifices. The thickness of the sheath may be varied by altering the relative positions of the crucible which, of course, alters the width of the annular orifice between the port 34 of the outer crucible and the conical end 35 of the inner crucible.
In the production of filaments by the use of this embodiment of the apparatus, the same factors must be considered as in the use of the previous described embodiments. For example, in formingtin-lead filaments, the temperatures, pressures and other factors may be as described hereinbefore. The ejector tube may be utilized with a tower as illustrated in Figure 4 and the atmosphere and pressure of the atmosphere in the tower are maintained to meet the requirements of the particular metals. Filaments may be formed from other metals which alloy with each other, for example, copper and nickel, aluminum and zinc, copper and silver, etc. Bimetallic filaments or clad filaments may be formed of metals which do not alloy with each other, for example, aluminum-uranium, copper-iron, aluminum-copper, aluminum-nickel, zinc-tin, etc. Where one or both of the metals has a high vapor pressure at the particular temperatures involved in the extrusion, for example, in forming an aluminum clad uranium filament, the apparatus of Figure 4 is utilized and the atmosphere in the tower is maintained suificiently high to prevent vaporization or volatilization of the metal of high vapor pressure, aluminum in this specific instance. If it is desired, for example, to completely sheath one metal such as uranium with another metal such as aluminum, the flow of the metal forming the sheath is first initiated and then the core metal extruded. In terminating the filament, the extrusion of the core metal is first arrested and finally the flow of the sheath metal is arrested.
It is well known that alloy wire or filament has a uniform composition in a direction transverse of the wire or filament. This invention provides for the first time alloy filaments or wire where the composition is not uniform but varies progressively across the filament as described hereinbefore.
The products of this invention differ completely in crystal or grain structure as compared to prior art products in that there has been no deformation of the crystals. The rapid chilling and solidification produces a cast structure while in prior art products the grains or crystals are elongated because of the mechanical working of the metal in producing wire or sheet forms. In the case of the bimetallic filaments of this invention, the chemical composition of the filaments may be substantially the same as that of bimetallic products produced by conventional methods. However, the grain or crystal structures of the products of this invention and the conventional methods differ completely as described with respect to alloy products.
As pointed out in detail in my copending application Serial No. 387,187, filed October 20, 1953, and when utilizing the chill plate, the cast metal filaments are solidified in a rectilinear shape with only one mold wall, namely, the smooth polished open surface of the chill block. Actually, the top and bottom surfaces of the cast metal ribbon-type filaments formed are separately and clearly identifiable, only the bottom surface bearing any indications of having engaged a mold surface. The upper surface of the filaments is characterized by shrinkage marks, relief dendrites, and line striae or marnmiforms, whereas the bottom surface which has engaged the chill block is smooth with the exception of polishing pit marks, buffing marks, and the imprint caused by any engraving or the like on the block.
Cast filaments may be formed at solidification rates of from 50 to 1000 feet per'second. As will be appreciated from the foregoing description these rates may be controllably varied to effect various desired results.
In view of the great speed of solidification effected, it is pertinent to note the method of measuring the solidification rate. The cast filaments formed carry on their bottom surfaces the impression of any mark placed on the chill surface. Since the surface tension of all molten metals is high it is obvious that the metal must have solidified while on the chill surface. The metal is never on the chill surface for one complete revolution of the surface (for if it was it would result in overlay or piling up of the material). In fact, with the present invention as described, only about one-half inch of the filament contacts the surface at any one time, that is to say, the molten metal goes onto the surface of the chill block at the same rate that the solid cast metal comes off. Then, since it is transformed from a liquid to a solid while on the rotating chill block, its minimum velocity of solidification can be calculated knowing the speed of the surface at the point of impingement and the length of filament making contact at any one time.
The foregoing description and specific examples are not intended as limitations of the invention but are to be considered as being illustrative. It is apparent that various changes and modifications may be made without departing from the spirit and scope of the invention.
1. An article of manufacture comprising a cast metallic anistropic filament formed of at least two metals substantially simultaneously solidified wherein the composition varies continuously and progressively throughout the transverse direction of the filament from substantially 100% of one metal on one side of the filament to substantially 100% of the other metal on the other side of the filament.
2. In a method for producing filaments formed of at least two metals comprising the steps of continuously extruding each of the metals in a molten state to form streams of molten metals, bringing the streams of molten metals together to form a continuous, single stream of molten metal and thereafter solidifying the stream of molten metal into a filament having a composition vary ing in the transverse direction of the filament from sub stantially 100% of one metal on one side to substantially 100% of the other metal on the other side of the filament.
3. In a method according to claim 2 including the step of bringing the metals in a molten state together to form a continuous single stream of molten metal through a gaseous cooling medium maintained under pressure until the stream has solidified into a filament.
4. The method for producing filaments formed of at least two metals which comprises bringing the metals in a molten state together to form a continuous single stream of molten metal, impinging the continuous single stream of molten metal against a concave chill surface, rotating the concave chill surface on an axis coincident with the center of concavity of the surface so that the surface moves relative to the stream of metal as it impinges upon the moving surface, solidifying the stream of molten metal on the chill surface so as to form a filament having a composition varying continuously and progressively throughout the transverse direction thereof.
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