US2289787A - Production of shaped articles from metal powder - Google Patents

Description

gully M l942 K. KAscHKE ET A1. 2,289,?87

PRODUCTION OF SHAPED ARTICLES FROM METAL POWDER Filed Feb. 27, 1939. Y

Patented July 14, 1942 UNIED STATES PATENT OFFICE PRODUCTION OF SHAPED ARTICLES FROM METAL POWDER' Kurt Kaschke, Berlin-Lichterfelde, and Hans Vogt, Berlin-Neukolln, Germany Application February 27, 1939,l Serial No. 258,854

Germany December 24, 1937 6 Claims. (Cl. Z5-22) sures, the invention consists not only of the structures herein pointed out and illustrated by the drawing but includes further structures coming within the scope of what hereinafter may be claimed.

The character ci the invention, however, may be best understood by reference to certain of its structurel forms, as illustrated by the accompanying drawing in which:

Fig. l is an axial section through an extrusion press exemplifying the principles of the present invention.

Fig. 2 is an axial section showing a further modiiled press.

Fig. 2d is a cross sectional view on line ab` of Fig. 2, showing the braking means only.

Fig. 3 is an axial section of a further modied press, with horizontal pressing direction.

Fig. 3a is a side elevation of the braking members of Fig. 3.

Fig. d shows diagrammatically a plant comprising an extrusion press similar to Fig. 3, on a reduced scale, and further apparatus.

Similar reference numerals denote similar parts in the diierent gures.

According to a known technic for forming a cylinder (or bar, or the like) a liquid or thermoplastic-material is placed in a hollow cylinder, is extruded through an orifice in the latter, by means of a piston reciprocating in the cylinder, and is solidiiied- (in its extruded form) by cooling. lt will be understood that this method is only applicable for materials producing very low friction at the walls oi the cylinder and oriilce. On the other hand, where cold metal powder is used as an initial material, it would probably be impossible to extrude bars in this manner at all due to the high friction oi metal powder at the said walls and the fact that it would not be possible to obtain a solid self-sustaining body in this manner.

As an initial material for our novel process,y

any metal powder may be used which is capable of being felted together by mechanicalgcompression. The felting action may be performed by an irregular shape of the metal particles' and/or by suitable additions or adhesives contributing to the felting action (e. g. talc), but preferably the felting action is achieved by the use of porous metal particles, consisting for example, of sponge iron. In this manner, more particularly by the use of spongy metal particle, it is possible to carry out the compression in such a manner that the resulting continuous rod or tube retains a considerable porosity. Such a porous Ametal structure may be very useful for certain special purposes, for example for the production of ilter bodies, metal wicks and more particularly self-lubricating bearing bushes or other anti-friction material. Also plastic metal articles. such as packing rings or washers, packing strips and the like may be made of such porous metal rods. A

For forming spongy iron powder and similar ieltable spongy metal powders into self-sustaining rods having a considerable porosity, the

metal powder could be charged, by portions, into a channel or elongated die of the desired prole, and each portion compressed therein, by means of a plunger orv piston, against an already compressed portion. Continued repetition of these acts would tend to extrude from the channel a solid self-sustaining rod, by employing a suitable counter-pressure against the frictional resistance oi the compressed powder. However, with such an arrangement there exists a certain diculty in so far as the said frictional resistance producing the counter-pressure against compressing action of the piston, if deviating by any reason from its prescribed amount, for example, due to slight dierences in the powder material, shows a tendency to decrease or increase iurther, as the case may be, whereby insufficient compression or obstruction in the die may result. In order to remove this defect, we provide additional resilient braking members, for example, in the manner shown in Figs. l, 2, 2a and 3. According to the invention, the feltable spongelike porous metal powder is progressively compressed, in successive portions, against an already compressed portion of the same powder in a die, whereby the feltable spongy metal powder is formed into a longitudinal object of relatively loosely compacted powder, and thereafter the cross-section of the object is reduced, while same is still contained in the die, by further and lateral compression, the total amount of compression so exerted upon the object being adjusted to produce a continuous self-sustaining object which retains a considerable porosity, whereupon the object is subjected to sintering treatment.

In Fig. 1, I II is a die, I2 is a cooperating plunger, I4 is a funnel-shaped receiver for a supply I5 of feltable spongy metal powder. Die III is formed with slots through which braking members I6 extend which form a conical -constriction in the channel within the die II), the size of which is variable and depends on the pressure exerted by the pressure spring II (the force of which may be variable by adjustment of the members I8) on the one hand and on the pressure exerted by the piston I2 on the other hand. It will thus be understood that an automatic regulation of the counter-pressure set up against the piston I2 is attained.V

In order to ensure an intimate joint between the material already compressed and the charge which is just being compressed, we may provide the piston I2 with a projection, for example, in the form of a central pin I9, Fig. 2, whereby the preceding charge is compressed with a central depression and overlapping with the following charge is produced. Moreover, the outer poru tions of the rod are thus compressed less intenouter conical surfaces lying against an interior conical surface of the die I0, under action of a central pressure spring 4I the pressure of which (and thereby the density of the bar) is adjustcorresponding in diameter to the desired internal diameter of the bar 43.

We contemplate also to arrange the metal bar extrusion press in the form shown in Fig. 3, with a horizontal operating direction. In this machine, the metal powder 1s fed, from a funnel or magazine 3D, into a casing 20 comprising a central mandrel 23 which may move with a reciprocating annular piston 22 or else may be mounted stationarily in the machine. The casing has an extension in the form of a die 24 which is provided with axial slots 50 to form somewhat resilient bridge portions 25 (Fig. 3a). By means of a conical ring 26 which engages inclined projections of the bridge portions 25 and a pressure spring 21 which is adjustable by a set nut 28, the bridge portions may be more or less inwardly pressed for a braking action to be exerted upon a tubular bar 29. It will thus be clear that with each return movement of the piston 22 a certain amount of metal powder 2| will fall from the funnel 30 into the casing 20, and be compressed with forward movement of the piston until the pressure exerted by the respective charge upon the bar 29 already produced exceeds the frictional counter pressure of the bar at the walls of the die 24 and, more particularly, at the braking-portions 25. whereupon the bar is extruded by a. certain amount.

Special steps may be taken to ensure uniform filling of the casing 20 from the funnel 30, by means of shaking action, for instance, or by a stirring arrangement (not shown).

A plant for producing metal bars in accordance wit'h the invention is shown in Fig. 4. The powder 33 moves from the funnel 30 into the die 3l and is compressed by a piston 32 which in turn is actuated by a hydraulic piston and cylinder system 34. The metal bar extruded from the press passes through a heating furnace 35 having a lining 52 of refractory, more particularly ceramic material in helical grooves of which a wire spiral 5I, for instance, of tungsten is arranged which acts upon the bar by heat radiation.

It is also contemplated to effect the heating by means of a high frequency current passed through the wire spiral 5I and producing heat in the bar by induction. A further heating method would be by resistance heating, in such a manner that the required heating current is fed to the bar by contact rollers or brushes at both ends of the furnace.

The bar is thus heated to sintering temperature and sintered together under action of a reducing or inert atmosphere, for instance, hydrogen or nitrogen gas passed through the furnace. In case of a temperature of about 1250 to 1300 C., a relatively short time is required for the sintering operation so that a furnace of moderate dimensions is sufficient, in accordance with the speed at which the bar leaves the press.

The bar leaving .the sintering furnace immediately moves into a cooling channel or chamber 36 through which a cold gas of good heat conductivity, for example, hydrogen, is continuously passed. The gas is circulated through a cooling device 31, under action of a circulation pump 38.

In order to facilitate the extruding process, it is possible to add lubricating agents, such as, small quantities of graphite or 2 or more percent of oil or mineral wax to the metal powder.

By way of alternative, the piston I2 may be replaced by a feed worm by which the powder is continuously fed to the die channel and compressed.

Our novel method permits the production of wires, rods, tubes or profiled bars of various cross sections from metal particles which are adapted to felt together. We contemplate, also, to produce after this process wires of difficultly melting metals such as tungsten, molybdenum and the like. In this case, the metal powder has to be prepared b-y sintering the particles together to larger porous aggregates than can be felted together in the extrusion press. In this case, the metal powder has to be preheated for the extrusion operation to a temperature at which the material is ductile, for instance, by the passage of electric current through a material in the magazine, as from the funnel I4 through the metal powder I5 to the punch I2, Fig. 1 or Fig. 2. It is thereby possible to produce bars or wires of the said metals which may be further worked in a rolling mill or the like.

We are aware that many further changes may be made and numerous details of the process and extrusion press may be varied through a wide range without departing from the principles of this invention.

We claim:

1. A device for the production of a porous metal rod from feltable, sponge-like, porous metal powder by pressing the latter through a nozzle-like passage against a counter-pressure set up by frictional engagement of a previously compressed portion of such metal powder in said passage, comprising a rigid die member forming the fore part of said nozzle-like passage, laterally movable die members having mutually cooperating surfaces defining the after part of said nozzle-like passage, said laterally movable die members being assembled to form a dilatable complete encircling ring and contact each other at planes of` separation which lrun tangentially between the members whereby limited outwardly radial movement of the members is possible without the formation of cracks between the members, and yieldable means for pressing said movable die members inwardly.

2. The improved device defined in claim 1, in which the cooperating surfaces of the laterally movable die members normally define a. constricted zone in the nozzle-like passage adjacent the exit end of the latter.

3. The improved device defined in claim 1, additionally characterized in that the laterally movable die members are pressed inwardly with respect to the passage by means of a spring adapted to exert resilient pressure indirectly upon material pressed through said nozzle-like passage.

4. Apparatus for forming a porous metal rod from feltable, sponge-like, porous metal powder such as iron sponge, which includes a bar press comprising in combination a die composed of a plurality of laterally movable members mutually cooperating to define a passageway there- "through, the laterally movable members presenting planes of division therebetween which have directions tangential to said passageway and said laterally movable members being ar pressure, and a reciprocatable plunger cooperating with the die, said die being so constructed as regards its length, surface character and cross-sectional shape that friction at its inner walls is suflicient for opposing a corresponding resistance to the pressure required for compressing and compacting the sponge-like porous metal powder, the friction ratio being selected to produce a porous metal rod.

5. Process for producing a longitudinal body, such as a solid or hollow rod, of uniform cross section, of porous metal from feltable spongelike porous metal powder of the type of sponge iron, which comprises progressively compressing successive portions of the feltable sponge-like porous metal powder against an already compressed portion of the same powder in a die, whereby to form the powder into a longitudinal object of relatively loosely compacted powder, thereafter reducing the longitudinal object in cross section by further and lateral compression, the total amount of compression exerted being adjusted to produce a continuous self-sustaining rod vwhich retains a considerable porosity, and sintering the resulting rod. i

6. Process for producing a porous metal hollow rod from feltable sponge-like porous metal powder of the type of sponge iron, which. comprises progressively compressing successive portions of the feltable sponge-like porous metal powder against an already compressed portion of the same powder in an annular space defined by a die and a central mandrel, whereby to form the powder into a tubular shape of relatively loosely compacted powder, thereafter and while the tubular shape continues to be in contact with the mandrel exerting inwardly lateral compression upon the tubular shape whereby to re duce its cross section and to form the same into' a self-sustaining but porous tube, and thereafter sintering the self-sustaining but porous tube.

KURT KASCHKE.

f HANS VOGT.

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