EP1252947B1 - Method for the manufacture of an axle element for a motor vehicle - Google Patents

Abstract

A bar-shaped semi-finished part (1) of aluminum is heated to forming temperature, its first end (2) is upset in a mold (4) of a forming tool (3) by a first die (5), and the second end (9) is pressed into the mold by a second die (8). Displaced material is forced into a bypass (10) of the mold and formed into a leg (11). The semi-finished part is finished in a forging process. The forging temperature is lower than 520 degrees C, e.g. between 420 degrees C and 480 degrees C. Forging temperature is approx. 520 degrees C.

Description

The invention relates to a method for producing a pivot bearing for motor vehicles.

Axle elements of motor vehicles, in particular pivot bearings for the front axle, are relatively complex, cast or forged one-piece components, which are made of a cast steel material or aluminum. At Schwenklagern attack considerable forces, which is why these components are usually made of a solid material. For reasons of weight saving, light metals such as aluminum are increasingly being used.

In the forge production of aluminum swivel bearings extruded round material is used as a blank. However, finished forged pivot bearings have a very uneven mass distribution, which is not associated with the cylindrical shape of the blank. However, in order to have sufficient material for the forging process in areas where more mass is required than in other areas, sufficiently large blanks are used. The disadvantage of the blanks used is that a relatively large amount of energy is required to heat the blank to the forging temperature required for hot working. On the other hand, the proportion of waste in areas with lower mass accumulations is relatively high. This is particularly disadvantageous in terms of cost, because aluminum is a comparatively expensive material. The above problems are not only true for pivot bearings, but for axle elements in general.

The JP-A-06 315734 discloses a method for producing a pivot bearing, a motor vehicle, in which a curved rod-shaped semi-finished Heated aluminum and compressed in an engraving of a forming tool. The engraving has three different branches corresponding to the rough contour of the pivot bearing. The three branches are each at an angle to each other. In at least two of the branches of the engraving engages a punch, wherein the cooperating stamp compress the bar-shaped semifinished product together in such a way that in the third branch a leg is formed, so that a Vorschmiedestück arises, which can be finally final molded.

The invention is therefore based on the object of demonstrating an improved method for producing a pivot bearing for motor vehicles from a rod-shaped semi-finished aluminum, in which the amount of energy to be supplied for forming is reduced and production-related material losses are reduced.

The solution according to the invention lies in a method for producing a pivot bearing for motor vehicles, according to claim 1.

With the invention it is achieved that the uniform mass distribution of the rod-shaped semifinished product, in particular a round material, is changed with respect to the axle element to be manufactured so that more material is provided in areas with larger mass accumulations in a preliminary stage of the actual forging process, as in other areas and Thus, a mass distribution is achieved similar to that of the axle to be manufactured.

For the upsetting the forming tool has an engraving, which allows a thickening of the material in discrete areas. Depending on the engraving, the first end can be pushed up directly by the stamp. However, it can also be provided a recess of the engraving at a distance from the first end of the semifinished product, in which results in the upsetting process accumulation of material by compressed material. The geometric shape of the engraving is determined taking into account specific diameter / compression ratio. To avoid puckering on the surface, the compression length should not exceed a fivefold of the diameter of the semifinished product. For upsetting the first punch is moved up to the semifinished product and then moves at a speed of up to 150 mm / s to the specified compression length.

Subsequent to the upsetting of the first end, a second punch acts on the second end of the semifinished product and presses it into the engraving. The compressed material flows backwards into a branch of the engraving, which is at an angle to the central longitudinal axis of the rod-shaped semi-finished product. Here, the pressed material is formed into a leg. The branch can be formed halfway upset length. Advantageously, the engraving is designed such that a neutral fiber is formed in the region of the central longitudinal plane of the formed leg. This ensures that in the subsequent finished forging in the die this neutral fiber flows into the ridge and thus a perfect directional microstructure in the component is made possible. The neutral fiber is influenced by the parameters of punch speed, temperature of the forming tool and the semifinished product, geometry of the engraving and friction on the surface of the engraving in their recrystallization behavior. By optimizing these parameters, recrystallization can be reduced to a minimum.

With this invention, two different methods are combined with each other in a single forming tool. On the one hand, the end-side upsetting of the semifinished product and on the other hand extruding to form a leg, without the rod-shaped semi-finished product would have to be fed between these two manufacturing steps another forming tool.

The semifinished product thus formed into a pre-forged piece is subsequently finally shaped in a forging process.

The advantages of the method can be seen in the fact that semi-finished products, such as extruded round material with a smaller output cross-section can be used and yet a favorable forging mass distribution is achieved by the preforming. At the same time, the energy to be applied for heating the semifinished product is lower due to the lower mass of the semifinished product. Finally, due to the close-to-net contouring of the pre-forged piece, lower burr losses occur during the forging process, so that less starting material has to be used from the outset.

From a technical point of view, the sensible division of forces for upsetting and Rückwärtsfließpressen is necessary, these operations are advantageously carried out in the horizontal direction. In order to keep the forming tool closed during the forming process, the clamping force acting on the forming tool must be approximately ten times the force applied by the first punch and the second punch.

The second end of the semifinished product is pressed against the holding force of the first stamp in the engraving. This means that after the Aufstauchvorgang the first punch this acts as a counter-holder and without loss of time or implementation of the workpiece, the extrusion process can be initiated by the second punch. Conversely, the second punch also serves as an anvil during the upsetting process.

While raw parts are heated in the warm forging to a temperature above the recrystallization temperature, so that no permanent solidification of the workpiece material occurs, it is sufficient for the production of a Aluminum forging, that the forming temperature is lower than 520 ° C (claim 2). Rather, a forming temperature between 420 ° C and 480 ° C for the deformation of the semifinished product suffice (claim 3).

According to claim 4, the first end of the preformed semi-finished product is further compressed before the forging process in a second forming tool. This can be particularly advantageous if the forces applied by the first stamp for upsetting must not exceed a certain level, so that material does not flow uncontrollably into the branch of the engraving, but is introduced controlled by the extrusion process by the second punch in the branch , A second forming tool thus enables even more near-contour contouring of the pre-forging.

In order to prevent a permanent solidification of the workpiece material, it is provided according to claim 5, to heat the pre-forging before the forging process to a forging temperature, which is advantageously heated above the recrystallization temperature. Here are about 520 C appropriate (claim 6).

The above-described method is suitable for the production of differently configured shaft elements, but in particular for the production of pivot bearings.

Figur 1

ein stabförmiges Halbzeug aus Aluminium;

Figur 2

das Halbzeug aus Figur 1 mit einem aufgestauchten ersten Ende;

Figur 3

das zu einem Vorschmiedestück umgeformte Halbzeug gemäß Figur 2 mit einem angeformten Schenkel an seinem anderen Ende;

Figur 4

ein aus dem Vorschmiedestück gemäß Figur 3 endgeformtes Schwenklager;

Figur 5

im Schnitt eine Vorrichtung zur Durchführung des Verfahrens, wobei in einem ersten Verfahrensschritt das erste Ende des Halbzeugs aufgestaucht wird, und

Figur 6

die Vorrichtung gemäß Figur 5, wobei der Schenkel ausgeformt wird.

The invention is explained in more detail with reference to an embodiment shown in schematic drawings. Show it:

FIG. 1

a rod-shaped semi-finished product made of aluminum;

FIG. 2

the semifinished product FIG. 1 with an upset first end;

FIG. 3

the semi-finished product formed into a pre-forged piece according to FIG. 2 with a molded leg at its other end;

FIG. 4

one from the pre-forging piece according to FIG. 3 end-formed pivot bearing;

FIG. 5

in section, an apparatus for carrying out the method, wherein in a first method step, the first end of the semifinished product is upset, and

FIG. 6

the device according to FIG. 5 , wherein the leg is formed.

FIG. 1 shows a rod-shaped semi-finished product 1 made of aluminum, concretely an extruded round material. This semifinished product 1 is heated in a production step, not shown, to a temperature of 450 ° C and then formed in two steps.

The first production step is an upsetting of the first end 2 of the semifinished product 1 to a diameter D2, which is approximately twice as large as the diameter D1 of the semifinished product 1. The remaining uncompressed length L2 of the semifinished product 1 is slightly more than half of the initial length L1 of the uncompressed semifinished product 1.

The upsetting of the semifinished product 1 takes place in a forming tool 3 according to FIG. 5 , For this purpose, the semifinished product 1 is inserted into an engraving 4 of the forming tool 3 and enclosed by the forming tool 3. A first punch 5 acts on the first end 2 of the semifinished product 1 and upsets it in accordance with the contouring of the engraving 4 of the forming tool 3. The first

At the end of 2 undergoes a transformation to a cylindrical end portion 6 with the diameter D2 (see. Fig. 2 ), which is tapered over a conical intermediate section 7 to the diameter D1 of the semifinished product 1.

So that the semifinished product 1 is securely held in the forming tool 3 during upsetting, another ram 8 brings a counter-holding force to the second end 9 of the semifinished product 1.

After the upsetting, the first punch 5 serves as an anvil, while the second punch 8 presses the second end 9 of the semifinished product 1 into the engraving 4. Here, the pressed material is fed to an end open branch 10 of the engraving 4, wherein a leg 11 is formed at the second end 9 of the semifinished product 1, as shown in the pre-forging 12 produced from the semifinished product 1 FIG. 3 can be seen. The leg 11 is formed according to the contour of the branch 10 so that the extrusion results in a favorable fiber flow in the pre-forging, that is, the branch 10 and the leg 11 is provided in the transition to the semifinished product 1 longitudinal engraving with radii , so that a smooth transition results.

In a further process step, not shown, the semi-finished product 1 formed into the pre-forged piece 12 is removed from the forming tool 3 and heated to a forging temperature of about 520 ° C. Subsequently, the in FIG. 3 shown forge piece 12 to the pivot bearing shown in Figure 4 forging final.

REFERENCE NUMBERS

1. 1 - semi-finished product
2. 2 - first end v. 1
3. 3 - forming tool
4. 4 - Engraving in 3
5. 5 - first stamp
6. 6 - cylindrical end section v. 2
7. 7 - conical intermediate section v. 2
8. 8 - second stamp
9. 9 - second end v. 1
10. 10 - branching v. 4
11. 11 - thighs
12. 12 - forging piece
13. 13 - pivot bearing

• L1 - length v. 1
• L2 - length v. 2
• D1 - diameter v. 1
• D2 - diameter v. 2, 6

Claims (6)

1. Method of producing a steering knuckle for motor vehicles, in which a bar-shaped semi-finished product (1) made of aluminium is heated to a forming temperature and the first end (2) of the semi-finished product (1) is upset in an impression (4) of a forming tool (3) by a first punch (5), while a second punch (8) applies a counterholding force to the second end (9) of the semi-finished product (1), and then the second end (9) is pressed into the impression (4) by a second punch (8), while the first punch (5) applies a counterholding force to the upset first end (2), wherein the semi-finished product (1) is straight before the upsetting by the first punch (5), and wherein the stroke movements of the punches (5, 8) lie on a common straight axis, wherein material pressed by the second punch (8) is forced into a branch (10) of the impression (4) to form a leg (11) and then the semi-finished product (1) formed into a pre-forged part (12) is finish-formed in a forging operation.
2. Method according to Claim 1, characterized in that the forming temperature is lower than 520°C.
3. Method according to Claim 1 or 2, characterized in that the forming temperature is between 420°C and 480°C.
4. Method according to one of Claims 1 to 3,
   characterized in that the first end (2) of the preformed semi-finished product (1) is upset once more in a second forming tool before the forging operation.
5. Method according to one of Claims 1 to 4,
   characterized in that the pre-forged part (12) is heated to a forging temperature before the forging operation.
6. Method according to Claim 5, characterized in that the forging temperature is about 520°C.

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