MXPA01007798A - Method and device for forming metals. - Google Patents

Abstract

The invention relates to a method for processing a metal part (2) by upsetting in an upset forging device (1) comprised of a clamping device (4), a forging die (5) and an upset hammer (7), wherein the following steps are carried out: a) clamping the metal part (2) in the clamping device (4) by forming an upset chamber (13) in the forging die (5), wherein the part is clamped outside the upset chamber (13) in such a way that the upsetting forces are directly absorbed by the immediate surroundings: b) using an upset hammer (7) on the metal part in such a way that the material (15) of the metal part (2) enters the upset chamber (13) when a force is exerted thereupon; c) prestressing the clamped metal part (2) by exerting pressure on the upset hammer (7) in such a way that the mechanical stress lies within the elastic (Hookean) range; d) providing an impulse with the upset hammer (7) on the metal part (2) during an interval and at a force such that the material (15) of the metal part (2) goes from the elastic to the liquid range, whereby the material (15) can spread into the upset chamber (13), the upset hammer (7) can move forward, wherein the pressure exerted on the material (15) decreases and the material can return to the elastic range and e) periodically repeating steps c) and d) until the upset forging process is completed. Said method makes it possible to obtain products having a homogenous structure.

Description

METHOD AND DEVICE FOR FORMING METALS DESCRIPTIVE MEMORY The present invention relates to a process for the metal processing, in particular to a stressing procedure, for metal workpieces, such as pipes, wires or profiles, as well as to a recessing device. According to the state of the art, the thickenings are generally carried out in such a way that a tube or a metal profile with the greatest wall thickness is presented and the thickness is reduced by appropriate stretching or hammering at the desired sites. This stretching or hammering, coming from the thicker profiles, represents a costly procedure, in particular when the portion of the thickening is simply small, in comparison with the remaining portion of the tube or the profile. Different attempts to swell the profiles for emphasis have failed so far. Several attempts to swell tubes or rods often caused the profiles to extend or bend laterally from the initial phase of the upset, with which ram jumps and landslides occur. In addition, an inhomogeneous crystalline structure of the formed material is achieved in this way, which is inconvenient with respect to stability. This is how wrinkles in the profile originate as well as in the trunk of an elephant.

It was tried to solve the phenomenon of the formation of folds, incorporating several stages of stamp with different form, which represents a very expensive procedure. It is therefore the object of the present invention to provide a method for processing metals by means of which thickenings in tubes, rods or other profiles can be rapidly and economically produced. It has been found that they can be thickened by stressing appropriately desired sites in tubes, rods or other profiles, if the workpiece to be stressed is pre-tensioned in the Hooke interval and the workpiece is pulsed with a hammer. I emphasize. The material of the work piece from the Hooke range is transferred to the plastic range in a short time by means of the drive hammer push-up. The impulse causes the material to flow in the zone of stress; in this way the recess chamber is filled a little, the recessing hammer follows the movement, the pressure descends, whereby the workpiece once again returns to the crystalline state, but is still under pre-tension. Subsequently, more periodic stressing impulses are supplied to the workpiece, whereby this takes place again correspondingly to the plastic range and to a recrystallization. By this way of proceeding, a thickened profile with a homogeneous structure could be obtained.

Therefore, the object of the present invention is the recessing method according to the definition in claim 1 and the recessing device according to the definition in claim 10. The method of the invention is designated as "intermittent recess". It is important in the same that the operating thrust forces are applied so that the driving in the upsetting chamber takes place and then serves to transport the material. For this it is necessary that the profile to be stressed in the recess chamber is free and that the remaining profile is maintained so that the upset forces are equalized outside the recess chamber or neutralized inertly against the walls. Through the dominant pressure relationships, the material is exposed to elevated temperatures. Therefore, the energy thus applied must be unloaded in the clamping space, so that the transition zone does not flow either and the material can not be extended uncontrollably. Before the procedure itself, the material to be shaped must be pre-tensioned with the corresponding hydraulic pressure, so that the conduction of the intermittent impulses is correctly produced. The pre-tension is preferably in a range that is just before the transition to the plastic range. The material is therefore in the state previously tensioned still in the elastic phase. Taking appropriate measures, the pre-tension is maintained during the entire stressing procedure, ie the workpiece to be processed remains under pre-tension between the individual pulses. Advantageously, the tensioned material is preheated, in particular with larger profiles, until precisely before the flow state. The energy to be supplied and the frequency are determined according to Brillouin (Brillouin area). Preferably, the preheating takes place locally in the microwave boost chamber. With thin profiles, preheating can be dispensed with. The pressure impulse can be applied to the previously tensioned and previously heated material, whereby the tensioned material flows. By softening the material, the pressure plunger can move forward and the pressure gives way; the material can be recrystallized. The pre-tension of the material between the individual pressure pulses is maintained. This can be done by using a hydraulic system that includes two hydraulic pumps, namely a pre-tension pump for the pre-tension pressure, for example at 40 bars (4 • 106 Pa), and a smaller pump of impulse for a pressure of up to 700 bars (7 • 107 Pa). The pipes of these piston pumps ("intermittent piston") must be fitted with a check valve. To exert a pressure pulse in the upsetting hammer, a hydraulic system is preferably used. In this way, the impulse of the hydraulic or intermittent piston is transmitted to the recessing hammer. The intermittent piston moves with oil to the material to be stressed, then the pressure is raised in such a way that the oil tensioned in the workpiece produces the desired pre-tension. The pipes between the pumps and the intermittent piston are non-elastic and must be installed without reflection for the pulse frequencies. On the oil previously tensioned, the pressure pulses are modulated for example with a controlled piston control on its frequency, so that a transmission of the impulse of the hydraulic piston to the recessing hammer (compressibility of the hydraulic oil of approximately 10"6) can take place. The time of the stress according to Hooke's law is determined, for which the first half-period of the intermittent frequency is established.For the second half-period, it must be controlled simply if it reaches the time available for recrystallization, With this method, The intermittent frequency is always adjusted to the material After the last distension of the material in the recess interval, the material is still in Hooke's range, ie it must be previously tensioned. hammer I emphasize in the interval of emphasis, since otherwise unwanted thickenings may arise near the int I emphasize. The invention is explained in more detail below with reference to the accompanying drawings. In the same: Figure 1 shows a sectional drawing of an upsetting device for carrying out the method according to the invention: state before the upsetting procedure, figure 2 shows the same device of emphasis as in figure 1, however after the emphasis procedure, Figure 3 shows an alternative embodiment of a device, namely a head upsetting apparatus for carrying out the method according to the invention, applied to another material or product, Figure 4 shows an arrangement of hydraulic pumps in the intermittent piston, figure 5 shows a pressure / stroke diagram of the stressing procedure, figure 6 shows a pressure / time diagram of the process according to the invention, figure 7 shows an enlarged cut of a recessing device similar to that of Figure 1, Figure 8 shows another embodiment of a recessing device that is formed to recal a hollow profile in a range between its ends, figure 9 shows detail D of figures 7 and 8 in enlarged scale, figure 10 shows, in a representation similar to that of figure 7, a device for producing a thickening rotationally non-symmetrical at the end of a tube, figure 11 shows, in a representation similar to that of figure 8, a device for producing a rotationally non-symmetrical thickening between the ends of a tube and figure 12 shows a schematic cross-section through a pulse generator. Figure 1 shows an intermittent recessing device 1 which is intended to emphasize a tube 2 at one end forming a greater wall thickness. A mandrel 3 is inserted in the tube 2, which serves to maintain the profile of the tube, preventing the material from being diverted to the interior part of the material. The tube is held by the clamping device 4 which exerts a counter-tension on the mandrel 3. The clamping device exerts a pressure uniformly around the entire tube. In this way, it avoids that the material is diverted in an uncontrolled way. In addition, the tube 2 to be emphasized stands out in the stamp 5 which is provided with a cooling spiral 6 which is fed by a cooling means 14. Thus the temperatures, hitherto required, which are originated by means of discharge, are discharged. the high pressures. The mandrel 3 protrudes through the tube 2 that is to be partially stressed in the stamp 5. At the end of the mandrel 3, which penetrates the stamp, a hole is provided which serves as a guide for the appendix 8 of the upsetting hammer 7. This appendix defines, together with the stamp, the upsetting chamber 13 to which the tube material can be extended during the upsetting procedure. The necessary pressure or impulses are exerted on the recessing hammer by means of the intermittent piston 10. It is hydraulically operated, the 11 representing the hydraulic pipe and the 12 the chamber for the hydraulic oil that spreads. Before the recessing procedure can begin, the tube to be stressed is placed with the mandrel 3 inserted in the desired position in the clamping device 4 and the clamping device is tightened as necessary. The upset hammer 7 is placed on the front of the tube that is in the stamp. The tube to be stressed is then pretensioned to where the material is still in the elastic range (Hooke interval). Since the hydraulic oil also has a lower elastic pressure range, the pre-tension here has the advantage that not only the metal part to be processed is previously tensioned, but also the hydraulic oil. During the stressing procedure, it is therefore in a range in which it has practically no elasticity. Figure 2 shows the same intermittent recessing device as in Figure 1, however after the separate recessing procedure. The reference numbers have the same meaning as in figure 1. In this figure it can be seen that the intermittent piston 10 has moved to the right in comparison with figure 1. In this way, the intermittent piston 10 was driven to the stamp 5, with which the piece is pointed, oriented towards the recessing hammer, of the tube to be stressed and the recessing chamber according to figure 1 is filled only through the entire upset piece 15 of the tube 2 that has to be stressed. Figure 3 shows an alternative embodiment of an intermittent upsetting apparatus for carrying out the method according to the invention. The apparatus 20 is a head upsetting apparatus. The device serves to emphasize a metal rod or a metal wire at one end, forming a head. A metal wire (not shown) is introduced into the hole 21 of the clamping device 22, until one end enters the hemispherical cavity 23 of the upsetting hammer 24 until it comes to a stop. The upsetting hammer 24 can exert a pressure on the workpiece through the plunger 25, whereby the material can be deflected to the stamp 26 and the hemispherical cavity 23 in the upsetting hammer 24. The plunger 25 is hydraulically actuated. The details of the clamping device and also of the hydraulic system are not illustrated in this figure, since they are obvious to the person skilled in the art. Figure 4 shows a typical arrangement of hydraulic pumps 31, 32 in the plunger 10 (figures 1 and 2) or 25 (figure 3) which exerts pressure on an upsetting hammer (not shown). The larger hydraulic pump 32 serves to maintain a permanent pre-tensioning pressure during the stressing procedure, for example at 40 bars. The smaller pump 31 serves to exert periodic impulse pressures, with a higher pressure, for example of 700 bars, which is sufficient for the transition of the material from the Hooke interval to the plastic range. The pipes 34, 35 of the pumps 31, 32 to the plunger are provided with check valves. For greater clarity, small diagrams 38, 39 are shown above the symbols of the pumps with a schematic indication of the evolution of the pressure.

Figure 5 shows a pressure / stroke diagram for an upsetting procedure according to the invention. The h represents the Hooke interval and the A the point of pre-tension. Figure 6 shows a pressure / time diagram b for an upsetting procedure according to the invention. The pulsating development of pressure during impulses is clearly noticeable. In the interval h, the material in the Hooke interval is pre-tensioned, up to point A of pre-tension. As soon as this point is reached, a first impulse is exerted on the material to be formed, with which the first peak of the curve originates. While this momentum passes the material to be formed from the elastic interval to the flow interval f, in which the shaping takes place, since the material flows. The piston can thus move further forward and the pressure drops to the pre-tension pressure, whereby the material can be recrystallized. The recrystallization phase is represented with the interval r. Next, an impulse is supplied to the material to be shaped, until the tip of the second peak. The same thing happens then as with the first peak: the pressure piston can also be deflected forward, with which the material passes into the plastic range, which allows a conformation. Then the pressure gives way again, which makes another recrystallization possible. This procedure is repeated until the desired conformation is achieved. In the diagram, is the pressure difference also indicated? which is a constant dependent on the material and which must be calculated or determined in another way.

Figure 7 shows important details of an upsetting device that is similarly constructed to the upsetting device according to Figure 1, in enlarged scale with respect to Figure 1. The clamping device generally designated with the 4 consists of several cylinders hydraulic, which act on the clamping jaws 16. In Figures 1 and 7, are represented only two series of cylinders that are in the longitudinal direction of the tube 2, distributed on the periphery of the clamping jaws. In practice, however, three or more series of hydraulic cylinders are preferably provided. It has been shown that good shaping results are achieved, if the holding force is high in the vicinity of the end of the tube 2 to be shaped, and it grows and then decreases again in the direction of the end of the tube 2. such development of the clamping forces, the unwanted flow of the working material of the tube 2 in the clamping zone is prevented. Therefore, the hydraulic cylinders that lie one behind the other in the longitudinal direction of the tube to be shaped, of the embodiment according to FIG. 7, have, in contrast to the embodiment according to FIG. Separate admission for the pressure medium. These intake ducts are not shown in Figure 7. By means of these separate intake ducts, it is possible to attend contiguous hydraulic cylinders with different pressure, in order to achieve the development of the clamping forces described above. In order to further improve the retaining force exerted on tube 2 by means of the clamping device 4, the surfaces of the clamps 2 clamping jaws 16 which come into contact with the tube 2 are provided with a friction-raising coating, in particular tungsten carbide, and at least the surface regions of the tube 2 which come into contact with the jaws 16 are rough . Another measure for raising the holding force, opposite to the forming force in the longitudinal direction of the workpiece, consists of a small rotary recess 19 which is provided between the stamp 5 and the clamping jaws 16. The recess 16 It is shown in figure 9, which represents in an enlarged scale the cut designated with the D in figures 7 and 8. In this recess 19, during the shaping a small emphasis of the working material of the tube 2 is formed, whereby the tube 2 is kept in the longitudinal direction also in form drag. In Fig. 7, the upsetting device is shown immediately before the upsetting procedure. The upsetting chamber 13 is limited in this mode by the contact surface 17 of the upsetting hammer, the appendix 8 of the upsetting hammer 7, the front surface 29 of the mandrel 3 and of course the stamp 5. The upsetting hammer 7 remains adjacent with its contact surface 17 to the front surface of the tube to be formed. Said in a simplified manner, the end region of the tube 2, shaded with crossed lines, is pushed by the shaping process in the direction of the arrows 18 to the upsetting chamber 13. For the force transmitted by the upsetting hammer 7 to be oriented. on the tube actually towards the recess chamber 13, the contact surface 17 of the recessing hammer does not extend at right angles to the longitudinal axis of the tube 2, but slopes in the form of a plate towards the tube 2. In case of it is important that the completely shaped tube 2 has a different front surface of the shape of the contact surface 17 and which is for example at a right angle, it is given its final shape in an additional work cycle by means of a additional stress hammer. In Figure 8, there is shown an embodiment of the upsetting device according to the invention, which is formed to emphasize a tube in the region between its ends. The left half of the device according to FIG. 8 corresponds essentially to the right half of FIG. 7. Completely to the left in FIG. 8, a base 27 can still be seen, on which tube 2 rests. On the right side of the stamp 5, another holding device 4 is present which stops the end of the tube 2. The upsetting hammer is staggered here twice. The first stage is formed by a contact surface 17 which, at the beginning of the forming process, transmits the stress to the tube to be shaped. Since the upsetting force must be transmitted within the right clamping device 4 through the tube 2 to the upsetting chamber 13 and the tube 2 in this clamping device must be pushed according to the degree of conformation to the left towards the chamber of emphasis 13, it is important that the clamping force of the right clamping device 4 can be adjusted. The second stage, formed by the surface 28 slightly inclined, limits the upsetting chamber 13, together with the appendix 8, with the front surface 29 of the mandrel 3 and with the stamp. As soon as the work material is stressed on the surface 28, it also transmits a portion of the upsetting force to the tube 2. It is obviously advantageous if the surfaces 28 and 29 are also inclined in such a way that their perpendicular lines are oriented to the upsetting chamber 13, as described above in more detail for the contact surface 17. It is clear that both the upsetting chamber 7 and the mandrel 3 and / or its orifice 9 can be formed almost arbitrarily, for example multiply stepped, to give a desired shape to the camera of emphasis. It is only to be considered that the upsetting hammer 7 and the mandrel 3 are configured in such a way that they can be displaced again from each other according to the shape they are given, without thereby damaging the formed workpiece. In addition, in all the above described embodiments of the intermittent recessing device, the parts to be formed are rotationally symmetrical. It is easily possible, however, within the scope of the invention to form rotationally non-symmetrical profiles and tubes or to form rotationally non-symmetrical regions in rotationally symmetrical profiles or tubes. Two examples of this are shown in figures 10 and 11. Figure 10 shows, in a representation similar to that of figure 7, a device for producing a rotationally non-symmetrical thickening at the end of a tube 2. The surface 29 ', which limits the recess chamber 13 on the side of the mandrel 3, is not oriented in this embodiment at right angles to the longitudinal axis of the tube 2. As is clearly seen in the drawing, also the clamping jaws 16 and the stamp 5 are formed asymmetrically in accordance with the foregoing. Figure 11 shows, in a representation similar to that of Figure 8, a device for producing a rotationally non-symmetrical thickening between the ends of the tube. In this mode, TS the surface 28 ', which limits the recess chamber 13 on the side of the recess hammer 7, which is not oriented at right angles to the longitudinal axis of the tube 2. According to the above, the clamping jaws 16 of the other device 4 and the stamp 5 are formed asymmetrically. It is necessary to determine empirically for each piece of work the frequency with which the hammer presses. It is then expected to obtain the best results, when a standing wave originates in the region to be formed of the tube 2, between the contact surface 17 of the recess hammer 17 and a virtual wall of reflection in the region of the appendix 19. It is therefore advantageous if the pulse frequency is adjustable and preferably variable even during the forming process. It is possible to determine empirically for each piece of work the frequency with which it presses the hammer of stress. It is expected that the best results can then be achieved, if a standing wave originates in the region to be formed of the tube 2 between the contact surface 17 of the recess hammer 7 and a virtual wall of reflection in the region of the appendix 19. It is therefore advantageous if the pulse frequency is adjustable and preferably variable even during the shaping process. The impulse pump 31 mentioned can be a conventional piston pump. A rotary pulse generator is more efficient. Figure 12 shows a schematic cross section through a possible mode of such a pulse generator 40. A central rotor 41 has at its center a longitudinal hole 42 which is admissible through a rotating package with a high pressure of 700 bars . The rotor is coated, on its cylinder liner surface for the purpose of minimizing wear, of a layer 43 for example of ceramic and surrounded by a stator 44. Radial channels 45 in the rotor conduct the high pressure of the orifice longitudinal 42 outwards. Also in the stator 44 the radial channels 46 are provided which communicate, while rotating the rotor, respectively shortly with their channels 45. At their radially outer end, each channel 46 of the stator 44 has a check valve 47. According to With the present exemplary embodiment, the check valve 47 consists of a sphere with a cylindrical appendix which is guided in the hole of a radial connecting pipe 48. The sphere and the appendage are perforated to ensure the flow of the mean pressure value through the connecting conduit 48 to an outer annular chamber 49, in which the pre-tension pressure predominates, for example at 40 bars. This pre-tension pressure is also that which compresses the ball of the check valve 47 towards its seat, while the channels 45 and 46 are not in communication with each other. All of the check valves 47 are retained in a valve ring 50. Of course, other known check valves can also be used, the valve body of which is for example a cone and is compressed, for example, by a spring towards its seat. Each time a current communication is made between a rotor channel 45 and a stator channel 46, a pressure pulse is finally generated. These pressure impulses reach particularly abrupt flanks, when the channels in the transition interval between the rotor and the stator have a cross section limited by straight lines, ie they are for example at right angles. In the example shown, the four rotor channels communicate with the four stator channels. In this way, the symmetric charge is guaranteed and the average amounts of pressure flowing through the channels are summed. Methods are also conceivable in which the number and arrangement of the channels are such that communications are carried out one behind the other. With such an arrangement, high impulse frequencies can already be achieved at low rotational speeds per unit time of the rotor.

Claims (20)

8 NOVELTY OF THE INVENTION CLAIMS

1. - Process for processing a piece of metal by upsetting in a recessing device, containing a clamping device, a stamp and a recessing hammer, characterized by the following procedure steps: a) embed the metal part in the device of clamping, forming a recess chamber in the die, the part being embedded outside the recess chamber in such a way that the upset forces are absorbed directly by the surrounding means; b) applying an upsetting hammer to the metal part in such a way that, when a force is applied thereto, the material of the metal part can penetrate into the upsetting chamber; c) pre-tension the metal part clamped by exerting pressure on the upset hammer, in such a way that the mechanical tension is within the elastic range (Hooke); d) exerting an impulse by means of the recessing hammer on the metal part, whereby the material of the metal part is transferred from the elastic range to the flowing range, whereby the material can be diverted to the recess chamber, the upset hammer can move forward and the pressure gives way to the material until the previous tension, and can once again go back to the elastic range; and e) periodically repeating steps c) and d) until the stressing procedure has been completed.

2. - Method according to claim 1, further characterized in that the material is a tube, a profile or a rod.

3. Method according to claim 1 or 2, further characterized in that the metal part consists of iron, copper or aluminum or alloys thereof.

4. Method according to any of claims 1 to 3, further characterized in that the jackhammer is driven through a hydraulic system, the pulses being generated by a piston pump and transmitted through the hydraulic piston to the hammer of I emphasize.

5. Method according to claim 4, further characterized in that the hydraulic oil in the hydraulic system is pre-tensioned so that the pre-tension force is achieved and a damping of the impulse is avoided.

6. Method according to any of claims 1 to 5, further characterized in that the piece of metal is heated with microwaves locally in the recess chamber, before it passes to the flow state, so that recrystallization is guaranteed.

7. Method according to any of claims 1 to 6, further characterized in that the excessive heating energy generated by the generation of pressure is supplied by cooling.

8. - Method according to any of claims 2 to 7, further characterized in that the metal part is a tube or a hollow profile, using a mandrel or appendix with adjustment precision there in the cavity where no stressing takes place.

9. Method according to any of claims 1 to 8, further characterized in that at least a part of the surface of the metal part is roughened before embedding it in the recessing device. 10.- Recessing device for processing a piece of metal, which contains a clamping device and a stamp that receive the piece of metal forming an upsetting chamber, an upsetting hammer and means to exert a pushing force on the hammer of I emphasize, characterized by the pulsating means, with which power pulses oriented in a periodically equal manner can be superimposed on the thrust force. 11.- Device of emphasis in accordance with the claim 10, further characterized in that the clamping device has several sources of force disposed one behind the other in the longitudinal direction of the workpiece, whose clamping force exerted on the metal part is individually adjustable. 12.- Device of emphasis in accordance with the claim 10 or 11, further characterized in that the clamping device has the clamping jaws, the surfaces of which come into contact with the workpiece are provided with a coating, in particular tungsten carbide. 13. Recessing device according to claim 12, further characterized in that the clamping jaws penetrate the side of the recess chamber slightly more inwardly than the adjacent staple, so that a rotating appendix is formed on which it is stressed. the work piece during the shaping, so that the retaining force produced by the clamping action, contrary to the longitudinal direction of the work piece, is concentrated by dragging. 14. Recessing device according to any of claims 10 to 13, further characterized in that the front contact surface of the recess chamber, which transmits the forming force to the metal part to be formed, is inclined in such a way that its perpendicular line is oriented towards the upsetting chamber to which the work material has to be pushed. 15. Device for upsetting according to any of claims 10 to 13 for processing a piece of metal, further characterized by another clamping device that is arranged on the side of the recess chamber facing the first clamping device. 16.- Device of emphasis in accordance with the claim 15, further characterized in that the recessing hammer has at least two stages, a first stage being formed by a contact surface with which at least a part of the forming force is transmitted to a front side of the metal part. and a second part being formed by a surface that limits the upsetting chamber. 17. Recessing device according to any of claims 10 to 16, further characterized in that the upsetting chamber is formed rotationally non-symmetrical. 18. Recessing device according to any of claims 10 to 17, further characterized in that the means for exerting a pushing force on the upset hammer consist of a permissible plunger with a pressure fluid. 19. Recessing device according to any of claims 10 to 18, further characterized in that the pulsating means contain the switching means which periodically connect a pressure fluid from a pressure source with higher pressure to the pressure fluid than causes the push. 20.- Adjustment device according to one of claims 10 to 19, further characterized in that the pulsating means has a rotor with a first admissible pressure chamber with a pressure fluid, which is connected to the camera at least one channel radially because the rotor is surrounded by a stator, in which at least one radial channel is provided, which is connected to a second admissible pressure chamber through a pressure fluid and because the channels are arranged in such a way that they communicate periodically with each other during the rotation of the rotor.