US2388558A - Metal extrusion press and method of operating same - Google Patents

Description

L. LOEWY Nov. 6, 1945.

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Patented Nov. 6, 1945 METAL nx'musron rasss AND METHOD or OPERATING SAME Ludwig Loewy, Bournemouth, England, asslgnor to The 'Loewy Engineering Company Limited, London, England, a corporation of Great Britain Application July 9, 1941, Serial No. 401,579 In Great Britain May 9, 1941 9 Claims.

This invention refers to extrusion presses on which metal rods, bars and tubes are manufactured, and relates also to methods of operating such presses.

The press according to the invention is charprocess, and'secondly, it allows the extrusion of tubes without undue loss of material through the piercing operation which heretofore was a very wasteful process, especially in the case of tubes of large inner diameter.

It isalready known that billets, when being extruded on an extrusion press, are subjected first to a certain amount of pressure before the extrusion itself is started. This was done merely for the purpose of compressing the billet into the billetreceiving space of the container and, in particular, to cause the billet to flow into the recess at the die end of the container, so that this space was completely and evenly filled by the billet. Nothing in the nature of a forging action was, however, attempted or could be achieved with the known types of extrusion presses, as no means were provided there to prevent'the billet from being inadvertently squirted through the die. To obtain a proper and effective forging action would require a space closed on all sides with the exception of that side where the forging tool would be applied. Such a space could not be provided with the known types of billet containers. I

With a press according to the invention, the bi]- let-receiving space of the container can be completely closed at the die end by special means. Specific pressure of sufiicient magnitude to obtain a forging effect on the billets can therefore be applied at the opposite end of the billet container which remains open as usual. This forging effect results first in breaking up the coarser particles of the internal grain of the billet. Furthermore, the grain structure will become substantially aligned in the direction of'the subsequent extrusion, so that on the whole the internal structure of the billet will be made more homogeneous. In this way, the billet structure will be refined and improved with subsequent beneficial results as regards the quality of the finished extruded products. These will show a uniform structure over their entire length, a result which could not previously be obtained with the known process, in which the fiow of the billet through the die began before the billet material was properly and sumciently worked. A further advantage of the new method is that less power is required for the extrusion and also the wear on the press tools is appreciably reduced.

The specific pressure which is applied for the forging treatment can be easily adjusted by means of the control gears which will be provided for the power drive of the press stem as is well known. After the forging action has been completed, the means for closing the die are withdrawn there from and the extrusion itself can be carried out in the usual manner.

Withregarcl to the extrusion of tubes of large inner diameter for which a press according to the invention is also particularly well suited, it has to be recalled that hitherto such tubes could not be extruded in a satisfactory manner, no matter what method was employed.

When solid billets were used, a central hole of large diameter had to be made first, either by piercing or by drilling through the billets. Both these operations resulted in'a very considerable loss of material through scrap, which in'some cases amounted to as much as half the Weight of the billet or more. In, addition to this, the removal of the pierced-out plugs from the press was diflicult, as the plugs were so heavy that when pushed out by the advancing extruded tube they were liable to cause the comparatively thin tube walls to collapse. The use of hollow instead of solid billets did not offer any solution, since the only way in which hollow billets can be produced so far is by casting, and this in itself is a process which requires a certain amount of skill. Furthermore, the surface of the cast billets is likely to be covered with oxide, including the inside of the bore. No means are, however, yet available to prevent this oxide from penetrating into the extruded product. Even small quantities of oxide are highly detrimental to the prop- I erties of the finished product, and have, in addition, a very deleterious effect on the press tools, the life of which will be considerably shortened. For all these reasons the extrusion of billets having a large inner diameter was not previously an economic proposition, although the demand for such tubes was quiteconsiderable.

In using a press according to the invention for the extrusion of tubes of large inner diameter,

the means for closing the die end of the billet container are rendered effective during the piercing operation. In this way the billet container is transformed into a closed-bottom receptacle while the billet is being pierced, with the result that the billet material which is displaced by the piercing mandrel will, instead of being forced through the die, flow away from the die and so cause the billet to grow in length. It is to be understood that during this stage of the operation the press stem will be held at some distance from the billet in order to leave sufilcient space free for the growth of the billet.

In order to avoid any risk of the piercing mandrel striking at the end of its stroke against the closure means, the billet is preferably not pierced completely through at this stage, and a thin wall is left at its end. In the next stage of operations the closure means are removed and the piercing of the billet continued, whereby the part forming the end wall is pushed out of the billet and through the die in the form of a small plug. This plug is the only portion of the billet material which will be severed from the billet during the piercing operation and it is thus evident that the loss of material during that operation is very considerably reduced as compared with a method in which a plug was formed which was as long as the billet itself. The extrusion of tubes of large inner diameter has, therefore, for the first time become an economically sound proposition.

After the piercing of the billet is completed, the press stem is advanced against the billet and the extrusion itself carried out in the usual way.

When employing the new method, tubes can be extruded from smaller billets than was hitherto possible, and the larger the inner diameter of the tube, the greater will be the saving in billet material. The use of smaller billets leads also to a better use of the available capacity of the preheating furnaces associated with the press installation and to a saving in the energy equired for heating the individual billet. Furthermore, in many cases, billet-handling equipment such as the billet conveyor can be simplified and made lighter, since the capacity of this equipment is determined by the largest billet which is to be handled by the press.

It is to be noted that both new methods described here can be applied subsequently to one and the same billet, that is to say, the billet can pierced in the manner described before. In this case the closing means will remain in position after the forging operation has been carried out until the first stage of the piercing operation has been completed.

As a rule, however, it will be found unnecessary to subject billets which are pierced according to the new method to forging action,- inasmuch as the billet material will be worked through sufliciently by the piercing operation alone. When extruding tubes of small or medium inner diameter an extra forging action may, however, be found to give beneficial results which may or may not be combined with the following Piercing operation according to the new method.

An extrusion press according to the invention is characterised mainly by the arrangement of means for closing the die end of the press container. These means can either consist of a separate closure plate which may be temporarily moved into position after the die has been withdrawn from the container. In thiscase the press will have to be of that type in which the container structure can be moved axially towards and away from the container, so that the necessary clearance for the insertion of the closure member can be established.

As an alternative, a plug-shaped closure member can be provided which fits tightly into the die aperture, so as to seal same completely. In the latter case the die will remain in its working position. This embodiment is particularly suitable for the adaptation of existing presses.

A more detailed description of the invention will be given in the following, reference being made to the drawings which are sectional part elevations of several embodiments of the new press. Only those parts of the press are shown therein which are relevant to the invention, those parts not shown being of conventional design.

Figs. 1 and 2 are views of a press adapted for the extrusion of solid rods or bars, Fig. 1 showing the press parts immediately before, and Fig. 2 during the extrusion.

Figs. 3, 4 and 5 are views of the same press adapted for the extrusion of tubes with large inner diameter, Fig. 3 showing the press parts before, Fig. 4 during, and Fig. 5 after completion of the piercing operation.

Figs. 6 and 7 are views of another type of extrusion press according to the invention, adapted for the extrusion of solid rods or bars, the figures showing the die and the closure means in their operative and inoperative positions respectively.

Figs. 8 and 9 are examples of how an extrusion press of normal design can be adapted for the purposes of the invention, Fig. 8 showing the closure means in their effective, and Fig. 9 in their retracted position. I

In the drawings, l0 indicates the platen of the press and II the holder for the billet container I2. The container holder is axially moveable in relation to the platen by means of a double-acting hydraulic drive shown here to consist of cylinder [3 and piston I! with piston rod l5. Fitted into the end of thecontainer bore is a shaping die 16 withdie-holde I! which are both mounted in a carrier l8. The die-holder carrier can be locked by means of a. locking piece I! which drops into position by its own weight and can be lifted by means of a hydraulic drive, comprising a cylinder 20 and a piston 2|. Arranged opposite to the container is, in the modification shown in Figs. '1 and 2, the solid press stem 22 which is fixed to a holder 23. The main ram and cylinder are not shown in the drawings since they are of conventional design and do not form any part of the invention. In the modification shown in Figs. 3, 4 and 5 the press is adapted for the extrusion of tubes, and therefore the solid press stem is replaced by a hollow press stem 24 and a mandrel 25, the latter being of the same diameter as the bore of the finished tubes. The mandrel is movable independently of the hollow press stem by means of a separate hydraulic drive, as is well known in this art.

According to the invention a closure plate 26 is provided, adapted to obturate the aperture of the die so as to form a seal between the container and the die (Figs. 1, 3 and 4). A tight fit between the closure plate and the container at one side and the die at the other side is obtained by means of the hydraulic system l3 and I by which the container holder, and thereby also the container, is pulled backwards towards the platen. As shown in the drawings, the closure plate is provided with a conical boss on its face on the container side which corresponds in shape with the means or a hydraulic drive, comprising a cylin-' 'der 30 and a piston 3|.

When operating the press for the extrusion of solid bars or rods, a heated billet B is first placed in the container and the closure plate 26 is then allowed to drop into the sealing position in which it obturates the aperture of the die against the,

container. It is understood in this connection that the container and container holder have been withdrawn before this from the platen and its associated parts by means of the hydraulic drive l3 and II to allow the closure plate to take up its position. After that the container is moved backwards to cause a tight fit between the container and the closure plate at one side and the closure plate of the die on the other. The press stem is then moved into the containe under full pressure (Fig. l) and forces the billet first'to fill completely the container bore and subjects it then to a thorough forging action. In doing 'so, the coarser particles of the internal grain of the billet structure are broken up and the structure is made more homogeneous at the same time, so that the extruded product will show a uniform grain structure from one end to the other.

After the forging action is completed, the closure plate is withdrawn into an ineffective position by means of the lifting device, 21, 28 and 29, after the container holder is first moved a short distance away from the platen so as to obtain the necessary clearance for the withdrawal of the closure plate. After that the container is moved back again so that the die comes into close contact with the end of the container bore and the extrusion process is carried out in the wellknown manner (Fig. 2).

When extruding tubes with large inner diameter the closure plate is allowed to drop into position in the same way as in the case of the extrusion of solid bars or rods (Fig. 3). The billet B is then pushed into the container by means of the combined action of the hollow stem 24 and mandrel 25, or by any other means suitable for that purpose. As shown in Fig. 3, the length of the container and that of the billet are so selected that the billet will fill only a part of the container bore, so that after the press stem and the mandrel have been withdrawn there is a certain space left free on that end of the container bore which faces the press stem. The mandrel alone is then moved forward and into the billet (Fig. 4) which is pierced through the greater part of its length. The stroke of the mandrel is so controlled that only a thin wall at the far end ofthe billet is left. The billet material which is displaced by the piercing operation is forced to flow backwards in a direction opposite to that of the mandrel movement whereby the above-mentioned free space at the end of the container bore is almost filled with billet material. After that the closure plate is withdrawn into its ineffective position and the container moved towards the platen so that the die fits closely into the container bore (Fig. 5). The mandrel is then advancedfor a further distance whereby the bottom of the billet is pushed out. The plug thus formed is the only part of the billet which is wasted during the piercing operation and it will be appreciated that this plug represents only a small fraction of a plug which would have been formed during the ordinary piercing process according to which the mandrel is moved into the billet, with the die open. The extrusion proper is then carried out in the usual manner by moving the hollow stem into the container.

Figs. 6 and '7 show a type of extrusion press which is particularly well suited for the arrangement of a closure member. In this form of press the die IS with its holder l1 and the closure plate 26 are both mounted side by side on carrier 30 which can be shifted in a horizontal plane transverse to the press axis. For this purpose a double-acting hydraulic drive is arranged which comprises a cylinder 3| and a piston 32. The container holder l I with the container ll! can be moved towards and away from the platen It as is the case with the type of press described above, by means not shown here. A guide-plate 33 is attached to platen ill for the carrier 30,

This arrangement is very simple, and has also the advantage that the die and the closureplate can interchange their operative positions at one stroke of the driving means, so that the change-over from one stage of operations to the other will be quickly eflected.

In Figs. 6 and '7 the press is shown equipped with a solid press stem 22 for the extrusion of solid bars and rods. For the extrusion of tubes the solid press stem will be replaced by a hollow press stem and mandrel, as described in connection with Figs. 3, 4 and 5. The method of operating the press according to Figs. 6 and 7 is exactly the same as that of the press according to Figs. 1 to 5, so that a detailed description of its'operation is not deemed necessary. It will be understood that various changes can be made in the design of the extrusion press described here, without departing from the spirit of the invention. For instance, the double-acting drive 3i and 32 for shifting carrier 30 can be replaced by two single-acting drives arranged at opposite rod 31. Upon lifting the wedge 36, the die holder carrier 35 and the die may be moved to the rear by hydraulic means, of which only'a part of the ram 41 is shown.

The means for closing the die end of the container are here in the form of a plug 38 which is so arranged that it fits tightly into the aperture of the die [6. Plug 38 is removably attached to a socket 33, so that it can be readily exchanged to suit various contours of the die. Socket 39 is mounted on a shaft 40 and connected by levers 4| to a carriage 42 which can be slid along the run-out trough 43 of the press. A' counterweight 44 is attached to levers 4|. Socket 33 is provided with lugs 45 at its periphery, which co-act with corresponding recesses in die-holder carrier 35 so as to form a bayonet joint. In order to lock and unlock this bayonet joint, shaft is adaptedto be rotated by means of hand lever 48.

Fig. 8 shows the plug 3. in position with the socket 39 locked with the die-holder carrier 3!. The die aperture is completely closed and the forging or piercing operation, as the case may be, can be carried out in the manner described before. In order to withdraw the plug it is only necessary to unlock the bayonet joint by turning the hand lever 46 and then retract the carriage 42 which can be wheeled along run-out trough 43 well beyond the position shown in Fig. 9, so as to avoid obstructing the path of the extruded stock leaving the press.

I claim:

1. A metal extrusion press, comprising in combination a billet-container having a straightthrough bore, an apertured die, adapted to be located at the end of this bore so as to give crosssectional form to the extruded stock, a closure member, adapted to obturate the passage through the die-aperture, means for moving said container away from said die so as to make room for the insertion of said closure member between said container and said die and means for effecting and maintaining a sealing contact between said container and said closure member and saidcontainer and said die.

2. A metal 'extrusion press, comprising in combination a billet-container having a straightthrough bore, an apertured die, adapted to be placed at the end of this bore so as to give crosssectional form to the extruded stock, a closure plate, adapted to obturate the passage through the die-aperture, means for moving said con-' tainer away from said die so as to make room for the insertion of said closure plate between said container and said die and means for moving said container towards said die and closure plate to eflect and maintain a sealing contact between them, said container moving means being formed by a set of hydraulic rams, adapted to be operated in opposite directions and connected to said container.

8. A metal extrusion press, comprising 'in combination a billet-container, having a straightthrough bore, an apertured die, adapted to give cross-sectional contour to the extruded stock, a closure plate, adapted to obturate the passage through the die-aperture, means for displacing said container in an axial direction towards said die, to efiect a sealing contact between said container and said die and said closure plate, and away from said die, to make room for the insertion of said closure-plate, and means for moving said closure plateinto an ineffective position outside the press and removed from the press axis and for,holding it in this removed position.

4. A metal extrusion press, comprising in combination a billet-container, having a straightthrough bore and a conical seat at the end of this bore, an apertured die, adapted to give crosssectionalcontour to the extruded stock when placed onto this seat, a closure plate, adapted to obturate the passage of extruded stock through said die and having a conical boss matching said seat, means for moving said container away from said die to make room for the insertion of said closure plate between said container and said die and means for moving said container towards said die to effect a sealing contact between the boss on the closure plate and the seat in the container bore.

5. A metal extrusion press, comprising, in combination, an apertured shaping die, adapted to assasse give cross-sectional form to an extruded bar, a billet-container having a straight-through bore and movable axially toward and away from said die, a closure plate, adapted to be moved to and from position between the die and billet container, and a plunger, having substantially the same cross-section as the container-bore and being movable in said billet-container to compact a billet while ,said closure-plate is in position between the die and billet-container and to extrude the compacted billet through said die, after withdrawal of said closure plate.

6. A metal tube extrusion press, comprising in combination, an apertured die, adapted to give cross-sectional contour to an extruded tube, a billet-container, having a straight-through bore and being movable axially toward and from said die, a closure-plate, means for moving said elm sure-plate to and from position between the die and billet-container, a plunger or a diameter smaller than the die-aperture and movable through the bore of the container and into the die, and a second plunger 01' a diameter substantially equal to that of the container. bore and movable through that container-bore, said first plunger being adapted to pierce the billet and form it into a tubular body with a closed end against said closure-plate and to eject the end portion of that body through said die, after the closure-plate has been withdrawn from the die, and said second plunger being adapted to compact a billet with said closure-plate in position and to extrude the pierced billet into an extruded tube in cooperation with said first plunger after withdrawal of said closure-plate,

'7. A metal extrusion press comprising in combination an apertured shaping die adapted to give cross-sectional form to an extruded bar, a billet-container having a straight-through bore and movable axially toward and away from said die, a closure plate adapted to be moved to and from position at the end of said bore and into the path of movement of the billet container, means to move said closure plate to and from position at the end of the billet-container, and a plunger having substantially the same cross-sectionas the container bore and being movable in said billet-container to compact a billet while said closure plate .is in position at the end of the billet-container and to extrude the compacted billet through said die when said closure plate is removed from the end of the billet-container and said die is in position at the end of the billet container.

8. A metal extrusion press comprising in combination an apertured shaping die element adapted to give cross-sectional form to the extruded stock, a billet container element having a straight through bore, one of said elements being movable axially toward and away from the other of said elements, a closure member adapted to be moved to and from position at the end of said bore and into the path of relative axial movement of said die element and billet container element, means to move said closure member to and from position at the end of the billet container element, and a plunger having substantially the same cross-section as the billet container bore and being movable in said billet container element to compact a billet while said closure member is in position at the end of the billet container element and to extrude the compacted billet through said die element when said closure member is removed from the end of the billet container element and said die element is means of the billet extruding plunser, piercing In that billet by means of a second plunger. having a diameter. smaller than that oi the die-aperture, both said compacting and said piercing operation being carried out while the die is obturated against the passage of extruded stock by a closure means, and extruding the billet into an extended tube, after the closure means have been withdrawn from the die and the second plunger moved into the die to take up its tube forming position. v

LUDWIG LOEWY.

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