EP2106309B1 - Method for the production of a forged part, forged part, and forging die - Google Patents

Abstract

The invention relates to the production of a forged part (11) having at least one unilateral extension (8), particularly a segment shaft, wherein round material is pressed to a blank (10) having unilaterally accumulating material in a first mold (7) by lateral extrusion, and is subsequently forged in a forging die (15), wherein a favorable fiber orientation is obtained. The invention also relates to a forged part, and to a forging die.

Description

The invention relates to a method for producing a forged part, in particular segment shaft, formed with a three teeth, one-sided, asymmetric extension and the forging produced thereon in particular segment shaft in a substantially elongated shape with a one-three teeth, unilateral asymmetric extension and the forging die for carrying out the method.

The DE 32 35 115 A1 (HITACHI Ltd) refers to the production of flange shafts. The flanges are loaded only on their peripheral area to pressure - but there are no rising flanks, which are typical for teeth and subject to special loads. The degree of deformation for an asymmetric segment shaft is much higher and the load on the teeth is different.

There are known segment shafts with a one-sided extension with three or more teeth. These segment waves are subject to a high load, especially on the flanks of the teeth. They are preferably installed in the motion train of a steering of commercial vehicles. Previous segments have been milled from solid material. However, this requires a high cycle time, high material consumption, and high tooling costs. In addition, the flanks do not have the required strength and must be reworked, e.g. hardened, become. The fiber course does not correspond to the ideal force curve.

It is an object of the present invention to provide a simpler method for producing a forged part, a forging part and a forging die which satisfies the strength requirements of a segment shaft.

The object is achieved by a method having the features of claim 1 a forging with the features of claim 8 and a forging die with the features of claim 10. Advantageous developments emerge from the dependent claims.

It is pressed round material to a blank with a one-sided material accumulation by lateral cross extrusion in a first mold and then forged in a forging sink. The combination of forming of cross extrusion presses and forging leads to a forging with minimal machining allowance. In addition, a favorable fiber profile is generated on the one-sided extension transversely to the direction of extension of the shaft, which leads to a high strength of the forging. A broken, deflected or split by machining fiber flow would significantly reduce the strength of the component.

In a press, round material is extruded cross-sectionally on the face, so that the material flows transversely to the pressing direction into a one-sided extension. Subsequently, the Querfließgepresste blank is removed with lateral extension of the pressing tool and fed to a forging die, in which the blank is forged to a forging part to near final shape.

In order to apply lower pressing forces, the round material is heated before the transverse extrusion. The round material is easier to reshape, the fiber flow is better coherent. In cross-extrusion, the pressing movement is much slower than hammer-striking forging.

It has surprisingly been found that when the blank is pressed into a forging die with at least one engraving extension having at least one expansion joint, the fiber flow in a forging is very well preserved. A deflection, compression or breakage of the fiber flow in the region of the one-sided extension on the forging is avoided. The strength of the forged part, in particular on the flanks of the claimed with high forces extension is further increased. Due to the at least one expansion joint at the end of the engraving extension excess material, scale, lubricant, etc. can escape. If the engraving extension has several ends, e.g. For teeth, an expansion joint is formed at each tooth end.

The raw material is preferably rolled round steel, in particular coke-rolled round steel. This raw material advantageously leads to an end product with the required high strength.

In order to apply sufficient forging forces, the forging is preferably standing, i. in the axial direction of the blank, forged in the gravitational direction. The weight of the forging hammer is thus exploited.

Preferably, in order to have the shortest possible cycle time, as well as machine time per forging, the blank is hot forged in one stroke.

To convert the forging into a finished product, the forging is machined with at least one extension at least at the end of the at least one extension. The excess material is preferably ground down to the final dimension. The fiber flow in the extension is not disturbed or broken and remains as desired.

In a preferred embodiment, the forging is a segment shaft with three teeth as an asymmetrical extension. The segment shaft is intended for use in commercial vehicles, in particular in their steering systems. The highest forces and torques act on the tooth flanks of the middle tooth. Therefore, it is necessary that the fiber flow in the flanks of the tooth is formed particularly well parallel to the flanks. This is achieved by transverse extrusion of round stock and subsequent drop forging of the blank.

It is a forged part in a substantially elongated shape with at least one unilateral extension of rolled round steel, in particular Koksgewalztem round steel, preferably produced by the method described above, wherein a fiber flow is formed in the forging parallel to the flank of the at least one extension. The extension with due to the Querfließpressens parallel to the extension edge extending fiber profile leads to an increased, desired strength of the forged as a whole and the one-sided, asymmetrical extension. A break, upsetting or deflection of the fiber flow in the region of the extension are essentially absent.

The extension of the forging preferably has at least one tooth, in particular three teeth, in order to advantageously obtain a forged part which can be used as a segment shaft in commercial vehicles.

Advantageously, especially the central tooth of a segment shaft substantially has a fiber flow running parallel to the flank of the tooth. This leads to a very high strength of the most loaded tooth, especially in the flank area. It is thus achieved a long service life of the forging. The manufacturing costs, in particular the cycle time, are lower than in conventional machining production processes.

The ends of the at least one extension, in particular of the teeth, are machined, preferably ground. As a result, disturbing burrs are removed due to the expansion joint of the forging die, whereby the favorable fiber progressions are retained.

For the forging method described above, in particular, a forging die is suitable which has at least one expansion joint in engraving end extensions for receiving excess material, scale, lubricant, etc. The die according to the invention allows the fiber courses, which are favorably deformed in the transverse extrusion method, to exist, in particular at the end of the extensions, and further presses the fiber progressions or the fiber flow. A breaking, upsetting or deflection of the fiber flow on a gravure wall is essentially avoided due to the expansion joint at the corresponding engraving area. Excess material can escape into the expansion joint or expansion groove in the die.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the respectively indicated combination but also in other combinations.

• Fig. 1 eine schematische Querschnittsansicht beim seitlichen Querfließpressen,
• Fig. 2 einen radialen Querschnitt des gemäß Fig. 1 hergestellten Rohlings,
• Fig. 3 eine Seitenansicht eines erfindungsgemäßen Schmiedeteils,
• Fig. 4 eine Querschnittsansicht des Schmiedeteils gemäß Fig. 3 im radialen Querschnitt und
• Fig. 5 das erfindungsgemäße Schmiedeteil in perspektivischer Ansicht.

The invention will be explained in more detail below with reference to an embodiment with reference to the drawings. It shows:

• Fig. 1 a schematic cross-sectional view of the lateral cross extrusion,
• Fig. 2 a radial cross section of according to Fig. 1 produced blanks,
• Fig. 3 a side view of a forged part according to the invention,
• Fig. 4 a cross-sectional view of the forging according to Fig. 3 in radial cross-section and
• Fig. 5 the forging of the invention in a perspective view.

The Fig. 1 shows in a schematic cross-sectional view of a first process step for producing a forged part of a cylindrical round material 1. The round material 1 is coke-rolled round steel and has a fiber profile 2a, 2b parallel to the walls. At the end faces 3, 4 of the round material 1 press punches 5, 6 are arranged, which press the round material 1 in a first mold 7 transversely. The round material 1 is pressed by the lateral Querfließpressen to a blank with a one-sided material accumulation in an extension 8. For this purpose, the first mold 7 has a one-sided engraving recess 9. The fiber profiles 2a, 2b, also called fiber flow, which are seen in cross-section, extend in the direction of the extension 8 without being broken during the transverse extrusion molding. The round material is heated before the transverse extrusion, thus the pressing forces for the cross extrusion are low.

The Fig. 2 shows in the radial cross-section of the resulting by the extrusion extrusion blank 10. The extension preform 8 is not yet clearly formed. The one-sided extension shape is achieved only by subsequent forging in a forging die and subsequent machining. The fiber courses 2a, 2b are nevertheless advantageously formed parallel to flanks of the extension 8 or they extend straight towards the extension end.

The Fig. 3 shows the standing forged in the longitudinal direction of the blank 10 forging 11. The forged part 11 has in this embodiment, pronounced teeth 12, 13 and a hidden tooth 14 on. The forging 11 is forged in the forging very close to the final dimensions.

The Fig. 4 shows in cross-section the forging die 15 with forged forging 11 in radial cross-section.

At each engraving area for extension ends, an expansion joint or expansion groove 16 is formed in the engraving end extensions of the forging die 15. The expansion joints 16 serve to absorb excess material, scale, lubricant etc. during forging so that material can escape into the expansion joints and the fiber courses 2a, 2b are not broken. Continuous fiber progressions are particularly advantageous for a forged part 11 with high strength.

The one-sided extension 8 on the forging 11 is, as in the Fig. 2 and 4 shown formed into three teeth 12, 13, 14. In particular, the center tooth 12 is exposed to particularly high loads when the forged part 11 is used as a segment shaft in commercial vehicles.

The central tooth 12 has a fiber path 2 b running essentially parallel to the flank 20. In the case of the lateral teeth 13, 14, the fiber flows to the flank 19 can be slightly oblique, since they are adjacent to the side edges of the extension 8.

Due to the expansion joints 16 at Gesenkgravurendbereichen 18 arise at the ends of the teeth 12, 13, 14 burrs that are removed by machining, in particular by grinding. Thus, by a small post-processing a finished segment shaft according to Fig. 5 from a forging part 11 with a one-sided extension, which is formed with three teeth 12, 13, 14, created.

All figures show only schematic not to scale representations.

Although the invention has been described in terms of various embodiments, it is by no means limited to these embodiments. Rather, these embodiments are merely exemplary embodiments. Modifications of the above exemplary embodiments will be apparent to those skilled in the art and others without departing from the scope of the invention. The scope of the invention is defined solely by the claims as explained by the description.

LIST OF REFERENCE NUMBERS

1

round material

2a

grain

2 B

Fiber course in extension

4

front

5

stamp

6

stamp

7

first form

8th

extension

9

material collection

10

blank

11

forging

12

middle tooth

13

tooth

14

tooth

15

forging

16

Dehnrille

19

lateral tooth flank

20

Tooth flank center

Claims (10)

1. Method for the production of a forged part, especially sector shafts (11) having an extension (11, 12, 13) that is designed as a unilateral, asymmetric part with three teeth, whereas

   - in a first form (7) round material (1) is pressed to a blank (10) by transverse impact extrusion accumulating material at one side and, subsequently, forged in a forging die (15) until the final form of the forged part has nearly been reached, so that the fibers in the flanks of the middle tooth are aligned parallel to the flanks and, thus, increase the strength of the middle tooth.
2. Method according to claim 1, characterized in that the round material (1) is heated prior to the transverse impact extrusion.
3. Method according to claim 1 or 2, characterized in that the blank (10) is pressed into a forging die (15) with at least one die cavity extension with at least one expansion joint (16, 17, 18).
4. Method according to one of the previous claims 1 to 3, characterized in that the feedstock is made of rolled round steel, in particular of coke-rolled round steel.
5. Method according to one of the previous claims 1 to 4, characterized in that the forged part (11) is forged in standing position axially to the blank (10).
6. Method according to claim 3, characterized in that the forged part (11) is, due to the expansion joint (16, 17, 18) in the forging die (15), shape-cut with an extension (8) that is designed as a unilateral, asymmetric part with three teeth at least at the end of the teeth.
7. Method according to one of the previous claims 1 to 6, characterized in that the forged part (11) is a sector shaft with three teeth (12, 13, 14).
8. Forged part, in particular sector shaft (11) essentially of longish design with an extension that is designed as a unilateral, asymmetric part with three teeth (11, 12, 13), produced according to a method according to one of the claims 1 to 7, whereby the fibers (2a, 2b) within the flanks of the middle tooth are aligned parallel to the flanks.
9. Forged part (11) according to claim 8, characterized in that the ends of the three teeth of the unilateral, asymmetric extension (8) are shape-cut.
10. Forging die (15) for the production of a sector shaft with an extension (11, 12, 13) that is designed as a unilateral, asymmetric part with three teeth and for the implementation of this method according to one of the claims 1 to 7, whereby the forging die (15) has at least one expansion joint (16) within the gravure expansions to accept excessive material or forged part scales etc.

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