EP0667196A1 - Method for the production of solid-headed mechanical structures from tubes and apparatus therefor - Google Patents

Abstract

The tube (1) is gripped in the jaws (2), touching the die (4) and a calculated length of end segment is electrically heated by current passing between the jaws and the die. The tube is forced upwards by a ram (7), and the heated head of the tube is deformed by the die. The tube may be filled to prevent buckling, and a plug of metal is inserted in the head of the tube for fusion with it. The body of the tube may also be upset along its length in forming blanks for e.g. cam shafts.

Description

The subject of the invention is a new method and a device for its implementation which allow the manufacture of parts comprising at least one forged end, thereby producing parts of great robustness.

In many industrial fields, for example in automobile construction, various bars are used, for example torsion bars, anti-roll bars, steering rods, suspension arms and the like which are produced by forging. and / or forging of solid bars and bars. It is the same for certain other parts developed for example crankshafts for engines.

Forged parts are known for their high mechanical characteristics compared to molded parts, for example cast iron parts. Forging is also a popular manufacturing operation in the use of light metals such as aluminum alloys.

If the forged or stamped parts according to the nature of the metals have advantages as regards their mechanical characteristics, they nevertheless have the disadvantage of being heavy, since massive, which is harmful in particular in their use on vehicles whose resistance weight equal should be as low as possible.

The invention starts from the observation that it is important to lighten many parts used in the industry, in particular in the automobile industry, without reducing their resistance while making it possible to obtain at least equivalent operating characteristics and in some cases better aerodynamics.

The invention also starts from the observation that the forgings which have to work on bending or twisting are intrinsically heavy since they are massive. In addition, the metal extending along the neutral fiber as well as in the vicinity thereof does not work or only of little use.

The method of the invention allows the production of parts having mechanical characteristics at least equivalent to existing forgings while reducing the weight significantly and improving, if desired, the external shape of said parts so that they work in the best conditions according to the constraints they are brought to bear and the aerodynamic conditions in which they are placed.

In accordance with the invention, the method for producing mechanical structures with a full head is characterized in that at least one end segment of a tube is subjected to heating bringing it to a temperature favoring plastic deformation, in that there is exerted on the heated end segment a force causing the metal to be forced back over a section of tube of length calculated to form a solid shaped head and in that said head is subjected at least to a forging operation performed hot or cold and then a deburring operation.

According to another characteristic of the invention, the device for producing tubular structures with at least one solid end is characterized in that it comprises clamps for holding a primary tube to distance from its end, at least one shaping anvil, means for applying a current between the clamps and the anvil to cause resistance heating at least of a tube end segment included between said clamps and said anvil shaping and means for pushing the material of a portion of tube segment projecting beyond the clamps in the form of a solid head shaped by said anvil.

Various other characteristics of the invention will also emerge from the detailed description which follows.

Embodiments of the subject of the invention are shown, by way of nonlimiting examples, in the accompanying drawing.

Figs. 1 and 1 a are explanatory diagrams of the method of the invention and of the device for its implementation.

Fig. 2 is a schematic section illustrating a phase of execution of the method of the invention.

Fig. 3 is a section, similar to FIG. 2, of another embodiment of the same phase of the process.

Fig. 4 is a partial explanatory section of a development of the invention.

Figs. 5 to 11 are elevations illustrating the application of the invention to the production of a suspension part for motor vehicles.

Fig. 12 is a schematic section illustrating a development of the invention.

Fig. 13 is an exploded and schematic section of another development of the invention.

Fig. 1 illustrates a tube 1 made of steel or another metal, for example aluminum alloy, intended to be used for the production of a work piece, for example as a torsion tube or as an elastic component or not of an assembly for example of a suspension mechanism for vehicles or the like.

The tube 1 is held between conductive clips 2, 2 a forming electrodes arranged at a distance from the end 1 a of the tube 1 and clamped according to the arrows 3, 3 a .

An anvil 4 also constitutes an electrode is contacted with the end 1a of the tube and held by an applicator member 5 which may be constituted by the frame of the device. The free end 1b of the tube rests on the bottom of a cradle 6 or other support movable by a jack 7 in the direction shown by the arrow.

The anvil 4, on the one hand, and the clamps 2, 2 a , on the other hand, are connected to a welding current generator (not shown) which is thus caused to pass through the part of the tube 1 which extends between the clamps 2, 2 a and the bottom of the anvil 4. This part of the tube is, in this way, heated by resistance and, when the temperature is sufficiently high taking into account the nature of the metal or of the alloy constituting the tube, the jack 7 is controlled to exert pressure on the tube 1 so that the part thereof extending from the end 1 a is pushed back, the internal walls of the tube thus being first of all progressively close together then welded by pressure at the same time as a solid head 9 of metal is formed as shown in fig. 1 a .

The clamps 2, 2 a are preferably mounted to allow the tube 1 to slide between them. In this way, the tube is only heated over a sufficiently short segment, which prevents buckling. The sliding of the tube under the action of the jack 7 is then controlled to cause the development of the head 9. The anvil 4 can be provided to be movable relative to the clamps 2 in order to vary the width of the segment of tube subjected to repression.

The head 9 is then brought into dies 10 subjecting it to a forging action which ensures the shaping of the head 9.

The successive actions of delivery and forging or stamping according to the nature of the metal or of the alloy have the effect of creating in the metal a fibrous structure in the extension of the initial fibrous structure of the tube and this fibrous structure extends throughout the shaped part, which gives the end of the tube thus worked all the qualities specific to forgings.

The forging carried out by the dies 10 which are carried by a press known in itself allows the head 9 to have a precise but possibly complex shape without there being any initiation of rupture in the part of junction with the tube 1. If desired and taking into account the nature of the metal constituting the tube 1, a flux, for example a borax, can be used to coat the internal wall of the part of the tube 1 intended to undergo the backflow and the welding by forging.

Welding of the internal wall is thus facilitated as it is pushed back, this welding then being perfect by the forging operation undergone by the application of the dies 10.

Fig. 2 shows dies working perpendicular to the direction of the longitudinal axis of the tube 1. It is also possible, if desired, taking into account the shape to be given to the head 9, to use dies working in the direction of the axis of the tube 1 as illustrated in FIG. 3.

According to the shape to be given to the end part of the tube 1, and at the junction between the end parts of the tube at the base of the head 9 the working part of the anvil 4 is shaped to present various shapes as illustrated at 11, on the one hand, and 11 a , on the other hand, in FIG. 4. It is thus possible to more or less flare the head 9 or, on the contrary, to lengthen it to direct the fibers in the preferred direction which is then given by the forging operation.

Figs. 5 to 11 illustrate an example of application of the invention to the production of a structural part of a suspension of a vehicle. According to these figures, one proceeds first of all to the preparation of tube segments 1 of a length L which is chosen taking into account the delivery length l which it is necessary to ensure as shown in FIG. 6 for obtaining a head 9 of sufficient volume for the production of a fixing head 9 a at one end of the tube 1.

As described in the foregoing, the head 9 a is then subjected to the forging operation, which is illustrated in FIG. 7, then to a deburring operation with separation of the chute illustrated in 9 '. A first end of the structural part is thus produced completely.

The tube 1 is then turned over to be worked in the same way as described with reference to FIG. 1 in order to form, from its free end, a second head 9 b which, in turn, is forged as illustrated in FIG. 10, the drop 9 'being separated by a deburring operation to finally obtain the structural part illustrated in FIG. 11 which has two solid heads connected by the tube 1.

The heads 9 a , 9 b can, if necessary, then undergo machining operations, in particular rectification and drilling to allow them to be joined to other parts.

In the foregoing, the forging operation is described to be carried out when the head 9 obtained initially by discharge is at high temperature, for example between 1200 and 1300 ° C in the case of a steel.

It would not be departing from the scope of the invention to carry out the cold forging or die-forging operation from structures comprising rough formation heads 9.

The hot push-back operation makes it possible to significantly reduce the forces necessary for pushing back and this also makes it possible to ensure a primary forging favorable to obtaining improved mechanical characteristics for the heads.

Depending on the shape and the length of the tubes 1 used as primary parts, the arrangement of the anvil 4 and the clamps 2, 2 a as well as that of the cradle 6 can be vertical as shown in FIG. 1, or horizontal.

It is also possible in applications such as those described in figs. 5 to 11 to produce the two heads 9 a , 9 b in a single working pass by providing two sets of pliers 2, 2 a and two anvils 4 disposed respectively opposite the two ends of the primary tube. In this case, it is the anvils that are mounted to be mobile along a stroke corresponding to the length of the tube segments 1 to be driven.

Fig. 12 illustrates a development of the invention according to which the bore 12 of the tube 1 is filled with a solid core 13.

To allow the above realization during the manufacture of a part to have two forged ends, the solid core 13 is introduced after the forging of one of the ends 9 or 9a has been carried out and the second forging is then carried out as explained. in the above.

The core 13 can be made of a homogeneous or composite material or even a liquid or a pulverulent material according to the technique considered and the problem to be solved which may consist, for example, in improving the elasticity of the structure or in standardizing thermal conduction.

Fig. 13 illustrates another development of the invention according to which a solid core 14 is engaged in the bore 12 of the tube 1 then is subjected at the same time as the end of this tube to the heating and forging operations. The forged ends, or at least one of them, may also have characteristics different from those of the tube.

The invention is not limited to the exemplary embodiments, shown and described in detail, since various modifications can be made thereto without departing from its scope. In particular, the invention applies by using tubes of section other than circular, in particular for the production of parts which must have improved aerodynamic characteristics, which may be the case for suspension arms.

Claims (12)

Method for producing mechanical structures with a full head, characterized in that at least one end segment of a tube (1) is subjected to heating bringing it to a temperature favoring plastic deformation, in that a force is exerted on the heated end segment causing the metal to flow back over a length of tube of calculated length to form a solid shaped head and in that said head is subjected at least to a forging operation carried out hot or cold and then a deburring operation. Method according to claim 1, characterized in that the length of the heated end segment is adjusted to prevent buckling during the delivery. Method according to claim 1, characterized in that a solid, liquid or pulverulent core (13) is inserted into the bore (12) of the tube 1. Method according to one of Claims 1 to 3, characterized in that a core (14) is engaged in at least one of the ends of the tube (1) and is subjected to the heating and then forging operations at the same time as this. tube. Device for producing tubular structures with at least one solid end, characterized in that it comprises clamps (2) for holding a primary tube (1) at a distance from its end (1a), at least one anvil (4) for shaping, means for applying a current between the clamps (2) and the anvil (4) to cause heating by resistance of a tube end segment included between said clamps and said shaping anvil and means for conveying material from a portion of a protruding tube segment beyond the clamps in the form of a solid head (9) shaped by said anvil. Device according to claim 5, characterized by a cradle or support (6) connected to a jack (7) causing its displacement as well as that of the tube towards the anvil, said tube sliding between the clamps (2, 2 a ). Device according to one of claims 5 and 6, characterized by dies (10, 10 a ) for shaping the head (9), respectively of a core (14), previously shaped by said anvil (4) . Device according to one of Claims 5 to 7, characterized in that the shaped head (9) and respectively the core (14) is subjected to a deburring operation. Device according to one of Claims 5 to 8, characterized in that the two ends of the same tube are subjected to the upsetting, forging and deburring operations successively or simultaneously. Device according to one of Claims 5 to 8, characterized in that the primary tube has any shape in section. Application of the structure of one of Claims 1 to 10 to the production of structures for vehicles. Process for the production of mechanical structures with a full head from tubes and device for its implementation as described and shown in the accompanying drawings.

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