Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
  • B21C23/00—Extruding metal; Impact extrusion
  • B21C23/02—Making uncoated products
  • B21C23/20—Making uncoated products by backward extrusion
  • B21C23/205—Making products of generally elongated shape

Definitions

• the invention mainly relates to a precision extrusion process for producing hollow metal parts.
• the invention also relates to a device for implementing such a method.
• hollow metal alloy parts can be made by a succession of operations, namely a stamping operation to 1250 0 C in one piece on hammer pestle followed by a deburring operation in which the burr formed during the stamping operation is severed, then a forging operation in which the deformation of the material is obtained by extrusion.
• the stamping operation consists of heating at high temperature the half-product called billet which is crushed between two dies.
• the back extrusion is a process in which, with reference to FIGS. 1 to 3, which respectively represent the initial, intermediate and final stages of a rear extrusion, a punch 1 is moved in translation in the direction of extrusion A in a jacket 3, or seat 3, having a fixed base 4 for receiving the forged blank 5a to be deformed.
• the diameter D of the punch head 2 which determines the internal diameter of the final hollow metal part 5c, this diameter D being substantially greater than the diameter d of the body of the punch 6 which is misaligned to avoid friction during spinning of the hot metal material.
• the length of the hollow part is not controlled during such an extrusion operation, this part is most often taken up during an additional operation, for example a machining operation. Also, another additional de-clogging operation must be implemented when it is desired to obtain a hollow body opening.
• the obtaining of a hollow metal part opening or not requires several operations, which results in that the tolerances obtained are not always compatible with the requirements of the specifications, in particular because of the deformations induced during the extrusion when sinking the punch into the hot metal material.
• the main objective of the invention is to overcome the aforementioned drawbacks by proposing a method for producing a hollow part opening or not, while simultaneously controlling the volume deformations generated by the extrusion operation.
• Another object of the invention is to reduce the number of operations and thus optimize the tooling required to make the hollow metal part and thereby reduce production costs and improve yields and production times.
• the method of the invention is essentially characterized in that, simultaneously with the depression of the punch in the forged blank during its forward travel in the direction of extrusion, a counter- Compensation pressure is applied to this material in the opposite direction, this compensating back pressure being adjusted both to create a back pressure allowing the material to spin around the punch, and to control the movement of material in the seat. by compensation of the extrusion force of the metal part.
• the compensation counter-pressure to be applied corresponds, at a given temperature, to the difference between the extrusion force of the metal part and the resistance of this part to the necking.
• ⁇ P [(Sl) X 0 (T 1 D 2 -Di)] - [(S2-S1) X ⁇ str iction (T)] in which :
• - Sl is the area corresponding to the section of a punch diameter Dl
• S 2 is the area corresponding to the section of a seat of diameter D 2
• ⁇ ( T , D 2 -D 1) is the stress associated with the metallic material and determined as a function of the difference D 2 -D 1 for a given temperature
• the compensation back pressure is applied at the level of the base on which the metal material rests.
• a deburring operation of the previously stamped metal part is carried out simultaneously with the extrusion operation.
• the punch causes a deburring tool in a position to perform the deburring operation.
• the hollow metal part obtained is disengaged from the punch during the return stroke of this punch in the direction opposite to the direction of extrusion.
• the forward stroke of the punch can be adjusted so that either at the end of the race go, or the head of the punch is contained in the metallic material which results in the realization of a hollow piece non-opening, or the punch passes through the bottom of the piece (60b) which results in the realization of a hollow opening piece.
• the invention also relates to a device for implementing the method described above which comprises a punch capable of moving in the direction of extrusion so as to sink into said forged blank during its course to go in the direction of extrusion and means for applying the compensation back pressure on the receiving bottom of this forged blank which is movable in the direction of extrusion.
• the movable bottom is mounted on at least one hydraulic cylinder to which is applied a pressure corresponding to the compensation back pressure.
• the device of the invention comprises a deburring tool secured to the punch during its travel to a deburring position of the stamped metal part.
• the device may comprise a work extractor which is movable relative to this punch during at least part of its return stroke so that the metal part obtained in which the punch is engaged abuts against the extractor and thus disengages the punch on the move.
• the movable bottom is solid so as to produce a hollow piece that does not open, or the movable bottom has a cavity in which the punch head engages at the end of the stroke, going through the bottom of the hole. this piece so as to make a hollow piece open.
• FIG. 1 is a schematic representation in plan of an extrusion device of the prior art in the initial position
• FIG. 2 represents the device of FIG. 1 during the forward travel of this punch
• FIG. 3 represents the device of FIG.
• Figure 4 "" is a schematic plan view of the device of the invention according to a first embodiment when the punch is in an end position go;
• Figure 5 is a schematic perspective view with a tear of the device of the invention according to the first embodiment when the punch is in the course of course go;
• Figure 6 is a schematic perspective view of the device of the invention according to the first embodiment in course of course go;
• Figure 7A is a schematic representation in plan of the left half of the device of the invention according to the first embodiment (hollow body opening) when the punch is at the end of the race go;
• Figure 7B is a schematic plan view of the right half of the device of the invention of Figure 7A when the punch is in the initial position;
• Figure 8A is a schematic representation in plan of the left half of the device of the invention according to a second embodiment (hollow body non-opening) when the punch is at the end of the race go;
• FIG. 8B is a diagrammatic representation in plan of the right half of the device of the invention of FIG. 8A when the punch is in the initial position; and FIG. 9 represents the rear extrusion abacus at 1100 ° C. giving the stress ⁇ as a function of the ratio D1 / D2 with D1 which is the internal mean diameter of the seat and D2 the average diameter of the punch body.
• the device of the invention comprises a fixed seat 10 which is intended to receive the forged blank not shown in Figure 4 and which is rigidly connected to a standard base plate 11 on which it rests , and to a circular plate 12 mounted concentrically around and in abutment against its upper flange end 13.
• This circular plate 12 is bonded and held parallel to the base plate 11 by means of holding rods 14 which extend along the longitudinal axis XX 1 and which are mounted integral in an intermediate plate 11a in support of connection with the base plate 11 by means of a stepped guide screw V passing through the intermediate plate 11a and mounted integral with the plate base 11, and around which a housing L receives a spring R short stroke.
• the punch 16 is of cylindrical longitudinal general shape and has a frustoconical base 17 in the extension of which extends a cylindrical body 18 terminated by a frustoconical pointed end 19 directed towards the base plate 11.
• the frustoconical base 17 of the punch 16 is rigidly connected to a punch holder piece 20 which is arranged in the longitudinal alignment of the punch and which is itself secured to a punch holder plate 21 surmounted by an upper adapter plate 15. of which she is in solidarity.
• the means for holding and moving the punch plate 21 will be described later.
• the device of the invention also comprises a piece extractor 22 concentrically disposed in sliding contact plane against the base 17 of the punch 16 and whose lower face 22a coincides with the upper face 60c of the forged blank 60a (FIGS. 7A and 8A).
• the lateral external face 30 of the extractor 22 is aligned with the lateral external face 33 of the upper end 13 forming a flange of the seat 10, and the lower face 22a of this extractor 22 further has a shoulder 31. which is opposite the hollow part formed not shown in this figure and whose width corresponds approximately to the thickness of this part, ie the spacing between the punch 16 and the inner surface 32 of the seat 10.
• this extractor 22 is rigidly connected to an extraction plate 23 by means of holding rods 24, this extraction plate 23 being mounted under the punch holder plate 21 and movable along the axis XX 'relative to the base plate 11 by means of longitudinal struts 26 whose upper end 27 is slidably mounted in this extraction plate 23 and which are slidably mounted in an associated guide housing 28 whose base 28a is secured to of the base plate 11.
• the device of the invention also comprises a deburring tool 29 mounted concentrically in plane support sliding contact around the extractor 22 and which, as shown in Figure 4, comes at the end of the race go of the punch, in contact with the upper end of the outer surface 33 of the flange 13 of the seat 10 , so as to section the burr 34 ( Figures 7B and 8B) of the forged preform 60a previously stamped.
• the deburring tool 29 is provided with a cutting section at the edge 36 which is disposed opposite and against the flange 13.
• This deburring tool 29 is rigidly connected to a cutter plate 35 by being mounted in this plate 35 which is disposed under the extraction plate 23 and which is secured to the upper end 38 of a guide ring 40 of a longitudinal guide column 39 whose base 41 is fixed in the base plate 11.
• the guide ring 40 is concentrically disposed in sliding contact plane around the corresponding guide column 39.
• the device of the invention comprises four guide columns 39 connected to the cutter plate 35 in the manner mentioned above.
• the cutter plate 35 is allowed to slide in the direction of extrusion, that is to say along the axis XX ', relative to the base plate by means of the guide columns 39.
• the device of the invention comprises eight guide spacer studs 43 whose head 44 is integral with the punch holder plate 21, whose lower end 45 is integral with the cutter plate plate 35 and whose the cylindrical body 46 passes through the extraction plate 23 by being mounted in sliding contact in this extraction plate 23.
• the gap between the punch plate 21 and the cut gate plate 35 is held fixed by the presence of the studs 43, while the extraction plate 23 is movable in the extrusion direction XX 1 relative to the punch holder plates 21 and cut gate 35, its travel being limited between these two plates 21, 35 and implemented by the extraction rods 26 and which are at the number of two ( Figure 5).
• the mobility in the direction of extrusion XX 1 of the punch plate 23 and the cutter plate 35 is provided by the guide columns 39 which is fixed the cutter plate 35.
• the spacing fixed between the punch plate 21 and the cutter plate 35 is set so that when the punch is at the end of travel go, the cutting tool 22 is in the position described with reference to Figure 4, that is to say against the surface external 33 of the flange 13 of the seat 10 and thus under the burr 34 that this cutting tool 22 has just cut, so that the deburring operation is performed simultaneously with the extrusion operation.
• the device comprises a movable bottom 50 which is a part of revolution comprising a base 51 and a cylindrical body 52 whose diameter corresponds to the internal diameter of the seat 10 taken at its lower portion 53.
• the diameter of the cylindrical body 52 of the movable base 50 is adjusted so as to bear in contact plane sliding against the inner wall 54 of the lower part 53 of the seat 10.
• this movable bottom 50 is mounted floating to a lower adapter plate 59, itself rigidly fixed to the base plate 11 via fixed pads 59a.
• the movable bottom 50 has a cylindrical cavity 56 of diameter substantially equal to the diameter of the body 18 of the punch 16 so that at the end of the race, the lower end 19 of this punch 16 passes through the bottom 57 of the metal part (FIG. 7A) in sinking into the cylindrical cavity 56 of the movable bottom 50 and expelling the cut portion of the metal part, which results in the production of a piece opening.
• the movable bottom 50 is full and the stroke of the punch 16 is such that at the end of the race go, the end 19 of the punch 16 is still contained in the metallic material.
• the movable bottom 50 is mounted on hydraulic cylinders with adjustable retaining pressure 58.
• the pressure P of the cylinders or counter-pressure compensation P is variable depending on the geometry of the metal part to be produced and is calculated in the following manner.
• the movable punch 19 creates during its stroke to go in the fixed seat 10 a back pressure which allows to generate the leak in the opposite direction to the direction of extrusion of the metal material trapped between the punch 16 and the seat 10.
• the extrusion force is determined in the following manner.
• F extrusion Sl x ⁇ ( T ⁇ D2 -Di)
• the necking resistance is determined as follows.
• ⁇ st r ictio n corresponds to the necking resistance of the metal part at HOO 0 C, this resistance being 10 daN / mm 2 .
• This compensating back pressure P corresponds to the pressure to be applied to the cylinders 58 which makes it possible to compensate for the extrusion force. It is this counter-compensation pressure which must be applied to the mobile bottom 50. This compensation effort is achieved by adjusting the hydraulic pressure of the cylinders 58 positioned under the movable bottom 50.
• An adjustment with a hydraulic pressure limiter makes it possible to adjust the correct pressure level.
• the adjustment of the pressure P of the hydraulic cylinders 58 gives this movable bottom 50 two functions.
• the first function is to create a back pressure P in the seat 10 to allow the material to spin around the punch 16 and against pressure is high enough to allow the extrusion of the metal around the punch 10 without creating necking in the spun area.
• the second function of this piston is to compensate for the change in volume during sinking of the punch 16 in the metal material.
• the compensation stroke is calculated in relation to the volume of material displaced during the extrusion of the material.
• the quality of the metal part obtained meets the specifications and the metal part can be made to the desired dimension in a single round trip of the punch 19 of the device.
• FIGS. 7A, 7B, 8A and 8B illustrate, for the two different embodiments, respectively for a through piece and a non-through piece, the state of the device in initial position, while FIGS. 7A and 8A represent the device according to these two embodiments.
• the forged blank 60 is a piece made of metal alloy of any type, heavy or light alloy, which was previously stamped on a hammer at 1250 0 C and can weigh up to 300 kg see more.
• This forged blank 60 is of roughly cylindrical shape and of diameter such that it can be housed in the seat 10 resting on the movable bottom 50.
• the forged blank 60 has an annular flange 61 which rests on the flange 13 of the seat 10 and in the extension of which extends the radial burr 34 resulting from the preliminary stamping operation.
• a press (not shown) applies a force directed in the direction of extrusion C to the upper adapter plate 15 which drives in translation in this direction of extrusion C the punch plate 21, the cutter plate 35 but also the plate extraction 23 when it abuts against the punch holder plate 21 in motion.
• the punch 16 is thus in motion in its forward stroke during which, simultaneously, this punch 16 sinks into the metal material 60, the movable bottom 50 is lowered according to the pressure P which has been applied to the hydraulic cylinders and determined as explained above.
• the metal part 60 is deburred by the deburring tool 29 whose support on the seat 10 is damped by the spring R of the intermediate plate 11a. Then, the metal part 60 is uncorked
• the punch then makes its return stroke by traction force applied to the adapter plate upper 15 which drives in translation in the opposite direction D in the direction of extrusion C the punch plate 21, the cutter plate 35 but also the extraction plate 23 when it abuts against the cutter plate 35 in movement.
• the extraction plate 23 is held fixed by locking the extraction rods 26 while the punch plate 21 continues its translation movement in the opposite direction D to the extrusion direction C, which it follows that the metal part 60, which has remained attached to the punch 16 abuts against the extractor 22, detaches from the punch 16 and falls into the seat.
• the method and device of the invention thus make it possible to produce deep holes by extrusion simultaneously with the deburring operation.
• These method and device are moreover adapted to any part geometry, the compensation counter-pressure P being determined specifically for each part.
• the parts that can be made by such a process are metal parts used in the field of valves, construction, mechanical industry but also in the railway, energy, aeronautics or transport, by example of the hollow pivots of mobile cranes mounted on truck.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Forging (AREA)

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• 2006
  • 2006-04-11 FR FR0651326A patent/FR2899499B1/fr not_active Expired - Fee Related
• 2007
  • 2007-04-11 ES ES07731277.5T patent/ES2451654T3/es active Active
  • 2007-04-11 EP EP07731277.5A patent/EP2004341B1/de not_active Expired - Fee Related
  • 2007-04-11 WO PCT/FR2007/000609 patent/WO2007116151A1/fr active Application Filing

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