CN111655394B

CN111655394B - Method for manufacturing wheel disc

Info

Publication number: CN111655394B
Application number: CN201880087817.3A
Authority: CN
Inventors: 大卫·皮耶罗纳克; 罗尔夫·达姆斯; 沃尔那·斯特里克; 斯特凡娜·格拉夫
Original assignee: ThyssenKrupp Steel Europe AG; ThyssenKrupp AG
Current assignee: ThyssenKrupp Steel Europe AG; ThyssenKrupp AG
Priority date: 2018-01-25
Filing date: 2018-01-25
Publication date: 2022-04-01
Anticipated expiration: 2038-01-25
Also published as: EP3743228A1; EP3743228B1; CN111655394A; WO2019145032A1

Abstract

The invention relates to a method for producing a wheel disc (1') for a vehicle wheel, comprising an inner region (2) having a wheel contact region (2.1), in which wheel bolt holes (2.3) having a wheel bolt hole geometry and/or a wheel bolt seat surface (2.31) are provided, an outer region (3) having a wheel disc lug (3.1) for attachment to a wheel rim, and a central region (4) connecting the outer and inner regions (2, 3). The invention further relates to a method for producing a wheel.

Description

Method for manufacturing wheel disc

Technical Field

The present invention relates to a method of manufacturing a wheel disc for a vehicle wheel, the wheel disc comprising an inner region having a wheel contact region in which wheel bolt holes having a wheel bolt hole geometry and/or a wheel bolt seat surface are provided, comprising a wheel disc lug having a wheel disc lug for attachment to a wheel rim, and a central region connecting the outer region and the inner region.

Background

Wheels or vehicle wheels are safety components and must therefore be able to permanently withstand large mechanical and dynamic alternating stresses during driving. A conventional "steel wheel" of sheet construction consists of a wheel disc (spoke) which is secured to a wheel hub and a rim (rim) which receives a tire. Wheel assemblies are nowadays produced in multiple steps (up to eleven steps) by cold forming (deep drawing, spin forming, profiling) on a multi-station automatic press. Here, only microalloyed steel (structural steel, fine grain steel) and dual phase steel having a strength of 400 to 600MPa have been used so far. The connection technique provided is preferably MAG welding in combination with a pressure connection (deep bed rim).

The weight of the wheel acts excessively on the energy consumption of the vehicle as a mass of the rotational movement and also on a mass without a spring mounted. It is therefore generally sought to achieve as low a wheel weight as possible in combination with a desirably high stiffness. In comparison with conventionally produced wheels, the lightweight construction potential can be further exploited with steel if, on the one hand, a higher strength or fatigue strength material is used to reliably withstand the working load and, on the other hand, a geometric adaptation, for example stamping, is effected to compensate for the loss of stiffness due to the smaller material thickness. However, as material strength increases, the cold formability of conventional steel (carbon steel), which has typically been nearly exhausted in existing wheel discs, also typically decreases. Therefore, a lightweight structure made of cold-formable high-strength steel faces a technical barrier according to the current wheel manufacturing concept. In addition to the weight of the wheel, the design also plays a critical role. The design freedom and attractiveness of the known steel wheels is therefore also severely limited by the conventional construction methods and materials.

In addition to so-called cold forming, so-called hot forming is also used in vehicle/body construction, which is also known in the art as indirect or direct hot forming. By using thermoforming, the requirements of high formability and high strength of the final formed member can be met at the same time. In the prior art, corresponding forming methods are well known, which involve, for example, a preliminary heat treatment of the workpiece in a separate furnace, in particular hot forming and press hardening of the steel sheet. However, up to now, the use of thermoforming in automotive manufacturing for vital cyclic loading members made of sheet steel, such as transverse links, wheels or axle carriers, has not been established.

As prior art for (sheet metal) hot forming of private car wheels or corresponding wheel discs, which can be press hardened at least in certain areas, reference is made to DE 102007019485 a1, DE 102013114245B 3 and DE 102014108901B 3. The emphasis of these documents is essentially on the local mechanical component properties after hot forming or press hardening, and the corresponding method steps or devices for the display of standard steel wheels without design requirements, which are generally configured to be rotationally symmetrical with respect to the profile outside the wheel contact area (central and outer area).

Documents DE 112007000239T 5 and EP 2495110B 1 disclose methods for producing design-optimized and/or spoke-shaped wheel discs from steel sheets for vehicle wheels by means of multistage cold forming using corresponding devices. The disadvantages of these known methods are the final "high" sheet metal thickness of the wheel disc, which is structurally necessary due to the large area of the ventilation holes (about 5.0-6.0mm), and the limitation in further design optimization due to the almost complete exhaustion of the forming potential. Multi-stage cold forming processes for producing design optimized and/or spoke shaped wheel discs are also not common.

Disclosure of Invention

The object of the present invention is to provide a method for producing a wheel disc for a steel wheel and a corresponding method for producing a wheel, which ensure a high degree of freedom in design, rigidity, weight reduction, operating strength and safety.

This object is achieved by the method according to the invention.

The inventors' fatigue strength studies have shown that hardenable steels with a predominantly martensitic and/or bainitic microstructure are comparable to conventionally used duplex and microalloyed steelsMaterials such as manganese boron steel, hardened and tempered steel and air-hardened steel have a significantly improved periodic alternating bending strength, so that in principle further weight savings can be achieved by reducing the sheet thickness, in particular the thickness of the wheel discs. In addition, the possible reduction in sheet metal thickness has a positive effect on the design of the wheel, since the radius can be designed smaller and therefore the overall design can be more complex. The inventors have found that, without limitation, particularly in the case of direct hot forming of wheel discs, the tooling possibilities are insufficient to produce particularly design-optimized and/or spoke-shaped wheel discs with acceptable sheet metal thinning. For this reason, it is proposed to provide a substantially flat slab consisting of a hardenable steel material (steel plate) which is cold-formed into a disc-shaped preform, wherein the disc-shaped preform is optionally perforated before, during or after production, the disc-shaped preform is cold-formed into a spoke-shaped wheel disc preform, wherein the spoke-shaped wheel disc preform is optionally perforated before, during or after production, and the spoke-shaped wheel disc preform is then heated to at least a_C1To be subsequently deformed or shaped while hot by at least partial press hardening.

According to the present invention, the wheel bolt hole geometry and/or the wheel bolt seat surface of the wheel bolt hole are shaped and/or calibrated during thermoforming. The shaping and/or alignment of the wheel bolt holes is performed during the thermoforming of the spoke-shaped wheel disc preform, wherein shaping is understood to create a substantially conical or spherical wheel bolt seat surface, in particular for receiving bolts or screws, for releasably connecting the wheel to the wheel carrier, in particular in connection with the integral shaping of the wheel bolt holes. The integral forming produces a beveled edge that extends substantially around the edge of the wheel bolt hole with less force and deformation being required to perform the integral forming during hot forming than in cold forming.

At a temperature A_C1Next, the structure begins to transform to austenite if the temperature A is exceeded_C3In particular completely in the austenitic form. The spoke-shaped wheel disc preform is preferably heated toAt least A_C3Such that a substantially austenitic texture is present throughout the component. A. the_C1And A_C3Characteristic values depending on the composition (alloy composition) of the steel used can be obtained from so-called ZTA or ZTU maps. Preferably, the at least partial press hardening is carried out in a tool which is subjected to hot forming, wherein the tool is composed of, for example, at least two tool parts, in particular at least one upper tool part and at least one lower tool part, wherein at least one region in which the press hardening is to be carried out is cooled, in particular actively, such that by contact with the tool parts, in particular with the tool/working surface of the tool parts, a rapid cooling is achieved for transforming the austenite into a hard structure, which in particular mainly comprises martensite and/or bainite. The required cooling rate can likewise be obtained from the ZTU map according to the required organization.

Thermoforming is to be understood as, in particular, converting a spoke-shaped wheel disc preform into the desired final geometry (target geometry) of the wheel disc. In combination with at least partial press hardening, a final part is provided having the final mechanical properties of the wheel disc and an at least partially predominantly martensitic and/or bainitic structure. The wheel disc may also be fully press hardened if desired.

Calibration is to be understood as a suitable measure which leads in particular to an increase in dimensional accuracy or to a maintenance of tolerances. "pure" press hardening is also contemplated.

According to one embodiment, the disc-shaped preform is cold-formed into a spoke-shaped wheel disc preform by forming stamping (impact forming) in at least one tool comprising at least one first tool portion and at least one second tool portion. Here, the disk-shaped preform is placed on the second tool part, in particular the outer region of the disk-shaped preform is in form-fitting contact with the outer region of the second tool part, in particular the tool surface/working surface thereof, at least in certain regions. The first tool part may correspond to an upper tool part of the tool and the second tool part may correspond to a lower tool part of the tool. By closing the tool, firstly the inner region of the first tool part, in particular the tool surface/working surface thereof, is brought into contact with the wheel contact region to be formed, in regions, on the disc-shaped preform, and before reaching the bottom dead center, the outer region of the spoke-shaped wheel disc preform to be produced is held between the outer regions of the two tool parts, in particular between the tool surfaces/working surfaces thereof, in a form-fitting and/or force-fitting manner. The flow/displacement of material to the outside can be prevented or suppressed by a form-fitting and/or force-fitting contact in the outer region, so that material displacement or material flow from the outside to the inside can occur in particular in the critical wheel disk region in a targeted manner. Thereby, critical thinning or reduction of material thickness, which may lead to tearing and thus to scrap, especially in the inner and/or central regions of the spoke-shaped wheel disc preform to be formed, may be substantially avoided. This approach to the targeted outward-inward displacement of material first makes a complex wheel design possible, since premature sheet metal thinning can be counteracted. The spoke-shaped wheel disc preform is formed at the lower dead point of the tool.

Alternatively, the disc-shaped preform may be converted into a spoke-shaped wheel disc preform by stretch forming and/or deep drawing.

According to one embodiment, the at least one hole is introduced before, during or after forming the disc preform or the spoke wheel preform. Preferably, the central hole is introduced before, during or after forming the disc-shaped preform. The central bore serves not only for subsequent centering of the finished wheel when mounted on the vehicle-side wheel carrier, but also allows material removal during cold forming to form the spoke-shaped wheel disc preform, in particular during the forming of the inner region of the spoke-shaped wheel disc preform. For example, during the production of spoke-shaped wheel disc preforms, flanges extending around the central hole are provided, in particular in order to increase the contact area between the wheel disc and the wheel carrier or its hub.

Preferably, the plurality of vent holes and/or the plurality of wheel bolt holes are introduced before, during or after the formation of the spoke shaped wheel disc preform, particularly before thermoforming. It is thereby possible to use already existing tools and trim or perforation is not integrated in the thermoforming tool, so that the complexity of the thermoforming tool and process control is not unnecessarily increased. Particularly preferably, the ventilation openings are introduced in such a way that a spoke-shaped wheel disc preform or wheel disc is formed. In particular, the spoke-shaped wheel disc preform and the wheel disc are designed to be non-rotationally symmetric.

According to one embodiment, a flange is provided that extends at least partially around the vent during thermoforming, thereby increasing the stiffness of the component and reducing the tendency for edge cracking during operation. Alternatively or additionally, if a flange has not been formed during cold forming into the wheel disc preform, a flange extending around the central bore may be provided and/or calibrated. In addition, thermoforming can also improve dimensional accuracy and form tolerances. Particularly preferably, the hot forming with at least partial press hardening takes place in one working stroke. The concentration of thermoforming and at least partial press quenching in one tool results in lower investment costs compared to multiple tools or operating steps.

According to one embodiment, the outer region of the disc-shaped preform or the outer region and/or the inner region of the spoke-shaped wheel disc preform is shaped close to the final contour. Whereby the outer region of the disc preform or the outer region and/or the inner region of the spoke-type wheel disc preform substantially corresponds to the outer region and/or the inner region of the finished or finished wheel disc. This has the advantage that subsequent finishing, in particular on the finished or finished wheel disc, can be dispensed with. Optionally, depending on tolerance specifications, in particular the component edges, in particular the outer regions of the disc preform or spoke-shaped wheel disc preform with the remaining flange, can be punched out, wherein in a subsequent operation the spoke-shaped wheel disc preform or wheel disc can be converted into the final geometry by shaping and/or trimming.

According to one embodiment, the press hardening is carried out at least in the wheel contact region of the wheel disk. If a predominantly martensitic and/or bainitic microstructure is present at least in the wheel contact region of the wheel disc, this advantageously leads to a high cyclic bending fatigue strength in the failure-critical region and allows a high prestress of the wheel bolts or screws, which has a particularly positive effect on the running strength. Depending on the design of the wheel, the coining quench may be performed on the entire wheel disc or in certain portions, such as only the inner region or both the inner and center regions of the wheel disc. The outer region of the wheel disc is preferably not press-hardened completely or completely, so that in particular the wheel disc lugs, when joined preferably by welding, do not suffer from a loss of hardness in the weld seam or in the heat-affected zone formed, since the so-called hardness pocket acts like a metallurgical notch, so that reliable operating strength of the wheel is no longer ensured.

According to one embodiment, the disc-shaped preform and/or the spoke-shaped wheel disc preform and/or the wheel disc can be trimmed and/or post-shaped at least in regions, in particular calibrated at least in regions. In particular, the disk-shaped preform is trimmed, for example, to remove excess material remaining during cold forming. The step of cold forming the substantially planar sheet blank into a disc-shaped preform may be provided by, for example, a deep drawing and/or stretch forming process. Alternatively, the disk-shaped preform can also be produced by rolling, in particular by spinning. Spinning has the advantage that material, in particular additional material, can be placed in defined positions, in particular for subsequent operations. Alternatively or additionally, the spoke-shaped wheel disc preform or wheel disc may be post-shaped at least in regions, for example may be calibrated to meet tolerance requirements. The trimming and/or post-forming is carried out in the tool used to produce the spoke-shaped wheel disc preform or in the thermoforming tool or in a separate tool. The trimming of the wheel disc may also be performed by a laser.

By selecting a suitable hardenable steel material, the normal production line of the wheel manufacturer can be continued to be used and, in connection therewith, since the hardenable steel material has, in its as-delivered or cold worked state, a moderate strength which is comparable to the steels conventionally used hitherto and therefore has a comparable suitable formability which is particularly suitable for cold (pre) forming of wheel discs, it is possible to produce individual components for wheel manufacture economically and efficiently. After (cold) forming, the potential of hardenable steels has not been exhausted. The hardenable steel material provided may be a hot-formed or quenched and tempered steel, in particular of the C22, C35, C45, C55, C60, 42CrMo4 grade, in particular a manganese-containing steel of the 8MnCrB13, 16MnB5, 16MnCr5, 20MnB5, 22MnB5, 30MnB5, 37MnB4, 37MnB5, 40MnB4 grade, a case hardened steel, an air hardened steel or a multi-layer steel composite, for example with three steel layers, at least one of which is hardenable. Particularly preferably, the carbon content of the steel used is at least 0.10% by weight, in particular at least 0.15% by weight, preferably at least 0.22% by weight.

According to another teaching, the present invention provides a method for manufacturing a wheel, the method comprising the steps of: providing a wheel disc manufactured according to the present invention; providing a rim cold formed from steel; non-removably attaching the rim to the wheel disc. In particular, the wheel disc is preferably connected to the rim via the wheel disc lugs in a material-fit manner and in particular by an additional force fit. To avoid repetitions, reference is made to an advantageous embodiment for manufacturing a wheel disc according to the invention.

Drawings

The invention will be explained in more detail below on the basis of the drawings. Like parts carry like reference numerals throughout. In detail:

figure 1 shows a process sequence of a method for manufacturing a wheel disc according to one embodiment of the invention in a schematic sectional view (along line I-I),

fig. 2 shows schematic cross-sectional views along line II-II during cold forming by forming punches for making spoke-shaped wheel disc preforms at different points in time,

figure 3 shows a schematic partial cross-sectional view prior to forming and/or aligning the wheel bolt hole geometry and/or the wheel bolt seat surface of the wheel bolt hole during hot forming with at least partial die quenching,

figure 4 shows a schematic partial cross-sectional view before the formation of a flange extending at least partly around a vent during thermoforming with at least partial press hardening,

FIG. 5 shows a schematic perspective view of a wheel disc, an

Fig. 6 shows a method flow of a method for producing a wheel.

Detailed Description

According to one embodiment of the invention, fig. 1 shows, in a schematic perspective view, a method process for producing a wheel disc (1 "") according to fig. 5, which comprises an inner region (2) with a wheel contact region (2.1) in which wheel bolt holes (2.3) with a wheel bolt hole geometry and/or a wheel bolt seat surface (2.31) are provided, an outer region (3) with a wheel disc lug (3.1) for attachment to a wheel rim and a central region (4) connecting the outer and inner regions (2, 3). Starting from a substantially flat slab (1), it is also conceivable to use a slab of suitable thickness, in particular a tailored product, for example a tailor-welded blank or a slab rolled by spin forming, made of a suitable hardenable steel material (steel plate), wherein the steel material used has a carbon content of at least 0.10 wt.%, in particular at least 0.15 wt.%, preferably at least 0.22 wt.%, in a first step a disc-shaped preform (1') is produced by cold forming, in particular by deep drawing and/or stretch forming methods using suitable means (tools) in one or more stages, or by spin forming, not shown. The disk-shaped preform (1') can already have an outer region (3), in particular a wheel disc lug (3.1), which corresponds to the outer region (3) of the finished wheel disc (1 "") or to the wheel disc lug (3.1), wherein the wheel disc lug (3.1) forms a contact surface with a rim, not shown, by means of which a connection, in particular a material-fit connection and preferably a force-fit connection, is established between the wheel disc (1 "") and the rim.

The disk-shaped preform (1') is preferably converted into a spoke-shaped wheel disk preform (1 ") by means of forming stamping, see fig. 2. The forming punch is carried out in at least one tool (10) having at least one first tool part (11) and at least one second tool part (12). Before insertion into the tool (10), a hole (5), in particular a central hole, can be introduced in the disc-shaped preform (1'). The holes (5) can be introduced into the planar blank (1) in a separate tool, not shown, or during the cold forming into the disk-shaped preform (1') or before the cold forming. The disc-shaped preform (1 ') is placed on the second tool part (12), in particular the outer region (3) of the disc-shaped preform (1') is at least partially in form-fitting contact with the outer region (12.2) of the second tool part (12), in particular the tool surface/working surface thereof. By closing the tool (10), the inner region (11.1) of the first tool part (11), in particular the tool surface/working surface thereof, is brought at least in regions into contact with the wheel contact region (2.1) to be formed on the disc-shaped preform (1'), as indicated by the arrow. Before reaching the bottom dead center, the outer region (3) of the spoke-shaped wheel disc preform (1 ") to be produced is held between the outer regions (11.2, 12.2) of the two tool parts (11, 12), in particular the tool surfaces/working surfaces thereof, in a form-fitting and/or force-fitting manner. The material flow or material displacement is prevented or prevented by a form-fitting and/or force-fitting contact in the outer region (3, 11.2, 12.2), so that the material displacement or material flow can take place in a targeted manner from the outside to the inside, indicated by the arrows, in particular into critical wheel disk regions. This makes it possible to prevent a critical sheet metal thinning or material thickness reduction in the inner region (2) and/or the central region (4) of the spoke-shaped wheel preform (1 '') to be formed. The spoke-shaped wheel disc preform (1') is formed at the lower dead center of the tool (10). A circumferential collar (2.2) is arranged at the central opening (5).

Not shown, the means for introducing a plurality of ventilation holes (4.1) and a plurality of wheel bolt holes (2.3) in the spoke-shaped wheel disc preform (1 ") can be integrated in the tool (10). The holes (2.3, 4.1) may alternatively also be introduced in a separate finishing/perforating tool, not shown. The ventilation holes (4.1) are preferably introduced in such a way that spoke-shaped and in particular rotationally asymmetrical wheel disc preforms (1' ") are formed.

The perforated or spoke-shaped wheel disc preform (1') is heated, for example in a furnace not shown, to at least A_C3Whereby a substantially austenitic structure is present throughout the component. The use of others is also contemplatedA suitable heat source. The completely heated spoke-shaped wheel disc preform (1') is introduced into a thermoforming tool (20) and is shaped or deformed into the final geometry by closing the thermoforming tool (20). The thermoforming tool (20) comprises at least two tool parts, in this embodiment for example four tool parts, an upper tool part (21), a punch-like tool part (24) integrated in the tool part (21) and two lower tool parts (22, 23). The lower tool parts (22, 23) are displaceable or movable separately from one another, for example the tool part (22) can also be constructed rigidly. The lower tool part (22, 23) can also be formed in one piece. In order to perform at least partial press hardening on spoke-shaped wheel disc preforms (1 '), preferably at least partially in the inner region (2) of the wheel disc (1'), the tool part (23) is provided with means (23.1), in particular fluid lines, which are arranged close to the tool part surface and through which a fluid flows and actively cools the tool part (23). The contact between the tool part (23) and the inner region (2) of the spoke-shaped wheel preform (1') leads to rapid cooling and transformation of the austenite into a hard structure which may contain, in particular, predominantly martensite and/or bainite. The tool parts (21, 22, 24) are made of such a material and/or comprise a coating on their tool surfaces/working surfaces which come into contact with the wheel disc preform (1 '), which prevents rapid cooling, in particular in the central region (4) and/or preferably in the outer region (3) of the spoke-shaped wheel disc preform (1'), or can actively regulate the temperature of the tool parts (21, 22, 24) by suitable and not shown means, so that a sub-M is substantially avoided in this region or these regions during the hot forming_STemperature (martensite start temperature) in order to exclude the transformation to a structure mainly consisting of martensite and/or bainite.

During the thermoforming of the spoke-shaped wheel disc preform (1' "), the wheel bolt hole (2.3) is shaped and/or calibrated, wherein the tool portion (23) comprises a recess (23.2) in the region of the wheel bolt hole (2.3) and the tool portion (21) comprises a corresponding recess (21.1), see fig. 3, enlarged. The tool part (23) is moved in the direction indicated by the arrow in the direction of the tool part (21) to shape and/or align or press-quench the wheel bolt hole (2.3) and, in combination with the integral shaping, to form a bevelled edge for a conical or spherical wheel bolt seat surface (2.31), respectively, substantially around the edge of the wheel bolt hole (2.3).

During the thermoforming of the spoke-shaped wheel disc preform (1'), a flange is provided which extends at least sectionally around the ventilation holes (4.1), wherein one or more punch-like tool portions (24) are integrated in the tool portion (21), the tool portion (22) comprising one or more corresponding indentations (22.1), see fig. 4, the dimensions of which are determined according to the number of ventilation holes (4.1). The punch-like tool part (24) is moved in the direction of the tool part (22), indicated by an arrow, and when moved into the recess (22.1) of the tool (22), at least in sections, the peripheral edge of the ventilation opening (4.1) is flanged and/or aligned, not shown.

Fig. 6 shows a method sequence for producing a wheel. A wheel disc (1') manufactured according to the invention and a rim (A, B) which has been cold formed from steel are provided. The rim is connected unreleasably to the wheel disc (1') (C), particularly preferably by means of a material fit and in particular by means of an additional force fit, by means of the wheel disc lugs (3.1).

A complex design can be achieved with the method for manufacturing a wheel disc for a vehicle wheel according to the invention without the risk of premature occurrence of critical sheet metal thinning.

Claims

1. A method of manufacturing a wheel disc for a vehicle wheel, the wheel disc comprising: an inner region having a wheel contact region in which a wheel bolt hole having a wheel bolt hole geometry and/or a wheel bolt seat surface is disposed; an outer region having a wheel disc lug for attachment to a wheel rim; and a central region connecting the outer region and the inner region, the method comprising the steps of:

providing a substantially flat slab consisting of a hardenable steel material,

cold forming the slab into a disc-shaped preform,

cold forming the disc-shaped preform into a spoke-shaped wheel disc preform,

-heating the spoke-shaped wheel disc preform up to at least a_C1Followed by thermoforming with at least partial press hardening, wherein the wheel bolt hole geometry and/or the wheel bolt seat surface of the wheel bolt hole is shaped and/or calibrated during thermoforming.

2. Method according to claim 1, characterized in that the disc-shaped preform is perforated before, during or after the production of the disc-shaped preform.

3. The method of claim 1 wherein the spoke shaped wheel disc preform is perforated before, during or after production of the spoke shaped wheel disc preform.

4. Method according to claim 1, wherein the disc-shaped preform is cold-formed into a spoke-shaped wheel disc preform by shaping stamping in at least one tool comprising at least one first tool part and at least one second tool part, the disc-shaped preform being placed on the second tool part, the tool being closed such that firstly an inner region of the first tool part is brought into contact regionally on the disc-shaped preform with a wheel contact region to be formed and, before reaching the bottom dead center, an outer region of the spoke-shaped wheel disc preform to be produced is held between outer regions of the two tool parts with a form-fit and/or force-fit and the spoke-shaped wheel disc preform is shaped at the bottom dead center of the tool.

5. The method according to claim 1, wherein the disc shaped preform is cold formed into a spoke shaped wheel disc preform by stretch forming and/or deep drawing.

6. The method of claim 1, wherein the at least one hole is introduced before, during, or after forming the disc shaped preform or the spoke shaped wheel disc preform.

7. The method according to claim 1, wherein the central hole is introduced before, during or after forming the disc-shaped preform.

8. The method of claim 1 wherein a plurality of vent holes and/or a plurality of wheel bolt holes are introduced before, during or after forming the spoke shaped wheel disc preform.

9. The method of claim 7 wherein a flange extending around the central bore is provided when manufacturing the spoke-shaped wheel disc preform.

10. The method of claim 1 wherein the notches, flanges extending at least partially around the vent holes and/or flanges extending around the central hole are provided during thermoforming of the spoke shaped wheel disc preform.

11. The method of claim 1, wherein the outer region of the disc shaped preform or the outer region and/or the inner region of the spoke shaped wheel disc preform is shaped to approximate the final contour.

12. The method of claim 1, wherein the press hardening is performed at least in a wheel contact area of the wheel disc.

13. The method of claim 1, wherein the thermoforming with at least partial press quenching is performed in one work pass.

14. The method of claim 1, wherein the disc shaped preform and/or the spoke shaped wheel disc preform and/or the wheel disc is trimmed and/or at least regionally post-formed.

15. The method of claim 14, wherein the disc preform and/or the spoke-shaped wheel disc preform and/or the wheel disc are at least partially calibrated.

16. The method according to claim 1, wherein a steel material having a carbon content of at least 0.15% by weight is used.

17. A method for manufacturing a wheel, the method comprising the steps of:

-providing a wheel disc manufactured according to any of the preceding claims;

-providing a rim cold formed from steel;

-non-removably attaching the rim to the wheel disc.