EP4126442A1

EP4126442A1 - Method for manufacturing a steel vehicle wheel, and steel vehicle wheel manufactured accordingly

Info

Publication number: EP4126442A1
Application number: EP21718003.3A
Authority: EP
Inventors: Marco Queller; Felix Schürmann; Achim Bandorski; Burkhard Tetzlaff; Erwin Blumensaat; Chris Schmidtke; Peter Ohse
Original assignee: ThyssenKrupp Steel Europe AG
Current assignee: ThyssenKrupp Steel Europe AG
Priority date: 2020-04-02
Filing date: 2021-03-23
Publication date: 2023-02-08
Also published as: WO2021197542A1; DE102020204310B3

Abstract

The present invention relates to a method for manufacturing a steel vehicle wheel (3), the method comprising the following steps: - providing a first component, which corresponds to a rim (1), and a second component, which corresponds to a wheel disk (2); - thermally, integrally joining the first component and the second component in order to produce an assembled steel vehicle wheel (3). The invention also relates to a steel vehicle wheel (3), comprising a wheel rim (1) with a wheel disk (2) thermally, integrally joined to the wheel rim (1).

Description

Process for the production of a steel vehicle wheel and a correspondingly produced steel vehicle wheel

Technical Field

The invention relates to a method for producing a steel vehicle wheel, the method comprising the following steps: providing a first component made of steel, which corresponds to a wheel rim, and a second component made of steel, which corresponds to a wheel disc; - Thermal, cohesive joining of the first and the second component to produce an assembled steel vehicle wheel. The invention also relates to a steel vehicle wheel comprising a wheel rim with a wheel disk that is thermally and cohesively joined to the wheel rim.

Technical Background (Background Art)

In the manufacture of steel wheels for motor vehicles, gas-shielded metal (MIG / MAG) welding is predominantly used for the thermally cohesive connection between a wheel disc and a wheel rim to produce a vehicle wheel. Due to the process, the welding speed is usually limited to less than 1.5 m / min. For example, the fatigue strength may be limited due to a strong notch effect. The notch effect is not only due to the geometry of the joining zone in the transition between the wheel disk / wheel rim and the joint seam (geometric notch effect), but can also have a negative effect in the form of an influence on the structure due to the thermal effect of the joining process (metallurgical notch effect). In the MSG welding process, an arc burns between a melting wire electrode and the component (s) to be joined. The amount of filler material used (wire electrode), expressed by the deposition rate, is directly linked to the amount of energy introduced, depending on the process. Wire electrodes for low-alloy steels according to DIN EN ISO 14341 and shielding gases according to DIN EN ISO 14175 are used. The heat input during MSG welding of conventional steel vehicle wheels is very high due to the slow welding speed. The connection between the wheel disc and the wheel rim is conventionally made as a fillet weld at the lap joint between the wheel rim and the wheel disc. Here, the connection seam is of subordinate importance as "securing the position", since the operational stress is borne by the frictional connection between the wheel disc and the wheel rim (drop center rim, drop center wheel). Fillet welds at overlap joints are unfavorable for components with fatigue stress due to the notches that appear (metallurgical and geometrical), but can hardly be avoided with conventionally manufactured steel vehicle wheels with this welding process. Conventionally weldable steels with a maximum tensile strength of 700 MPa with good formability are used as base materials for wheel rims and wheel disks. Higher strength or ultra-high strength steels have a high potential for improving performance, but have so far not been used due to their limited suitability for forming and joining compared to normal-strength steels and the comparatively low load capacity under fatigue stress, so that the potential of ultra-high-strength steels such as manganese -Bor steels cannot be used meaningfully so far, especially if the joining zone is welded using the MSG process and is exposed to high fatigue loads. Even with normal-strength steels, the joining zone is often the area in which failure occurs under fatigue stress. The laid-open specification DE 11 2004 000 312 T5 describes an example of a method for producing a steel vehicle wheel using the MSG method.

In the production of steel vehicle wheels, at least with regard to the thermal stress (metallurgical notch effect), it was already recognized in EP 1 184 202 B1 that a MSG soldering process can create a more material-friendly (soldering) connection between the wheel rim and the wheel disc. Furthermore, it is known from EP 3 610 983 A1 to prefer a laser welding process for reducing the heat-affected zone when joining a wheel rim to a wheel disk in the manufacture of steel vehicle wheels instead of an MSG welding process.

With regard to the state of the art, there is a need for optimization in the production of steel vehicle wheels comprising a wheel rim with a wheel disk that is thermally and cohesively joined to the wheel rim.

Summary of Invention

The invention is therefore based on the object of providing a method for producing a steel vehicle wheel, with which the aforementioned disadvantages and problems can be essentially avoided or at least substantially reduced, and to provide a corresponding steel vehicle wheel. This object is achieved by a method with the features of claim 1. This object is achieved by a steel vehicle wheel with the features of claim 7.

According to the invention, it is provided that a laser-MSG flybridge method is used for thermal, material-locking joining. The joint between the wheel rim and the wheel disk is therefore a laser-MSG-Flybrid joint.

The inventors have found that by using a laser MSG flybridge method for the thermal, cohesive joining of a wheel rim and a wheel disc to produce a steel vehicle wheel with a laser MSG hybrid joining connection between the wheel rim and the wheel disc, a steel vehicle wheel a high load-bearing capacity under operating loads, high connection stiffness and a reduced geometric notch in combination with a low expansion of the joint connection and heat-affected zone, so that the structural influence and the resulting metallurgical notch can be reduced. This results from a joining speed that is up to 5 times higher than conventional MSG welding for the production of steel vehicle wheels, which results in a reduction in the heat input and thus among other things. the distortion as well as the residual stresses. Compared to laser beam welding, this results in an improved gap bridging capability and thus a reduction in the demands on the tolerance of the components for secure welding and thus the possibility of one-sided joining with full connection of the laser-MSG hybrid joint. The laser-MSG hybrid process combines a laser welding process with a MSG (metal shielding gas) welding process. This advantageously combines the advantages of the two individual methods.

Further advantageous configurations and developments emerge from the following description. One or more features from the claims, the description and also the drawing can be combined with one or more other features from them to form further embodiments of the invention. One or more features from the independent claims can also be linked by one or more other features.

According to one embodiment of the method according to the invention, a laser arrangement can be guided in the joining direction before or after an MSG arrangement. Is preferred Laser arrangement guided in front of the MSG arrangement. The material of the component (s) with a small spot diameter is melted by means of a laser beam. Due to the high energy density, the laser beam can penetrate deeply into the material of the component (s), melt it and connect it. In the MSG welding process, filler material is introduced and the weld pool is enlarged due to the divergence of the arc. The filler material compensates for the cross-section reduction resulting from the air gap between the components to be connected as well as the shrinkage stresses and creates a secure flank connection. A laser-MSG hybrid joint connection resulting from this can have a high welding depth with high seam quality.

The parameters for the laser welding process and the MSG welding process can be set individually and / or independently of one another. In this way, the shape and depth of the joint seam / connection can be adapted to the component conditions in order, for example, to achieve optimal seam quality.

A fiber laser, for example a Yb, Nd: YAG or Yb: YAG laser, can be used as the laser. The use of a gas laser, for example a CO 2 laser, is also conceivable.

According to one embodiment of the method according to the invention, the joining speed is between 1 and 5 m / min. In order to reduce the introduction of heat, the joining speed can in particular be increased to at least 1.3 m / min, preferably to at least 1.6 m / min, preferably to at least 1.8 m / min.

According to one embodiment of the method according to the invention, the power of the laser is between 3 and 10 kW. In order to increase the depth of the welding, the laser power can in particular be increased to at least 3.5 kW, preferably to at least 4 kW.

The laser spot diameter can be selected between 100 and 1500 pm.

The focus position of the laser can be selected between -5 and +5 mm in relation to the surface of the component.

The focal length of the laser welding optics can be selected between 50 and 500 mm. The collimation of the laser welding optics can be selected between 50 and 500 mm.

The angle of the laser to the surface of the component and at right angles to the joining direction can be selected between - 45 and + 45 °. 0 ° corresponds to a perpendicular or right-angled alignment to the surface of the workpiece / component. In the case of one-sided and / or limited accessibility, the angle of the laser to the surface of the component transversely to the joining direction can be between -45 and -2 ° or +2 and + 45 °. At right angles to the joining direction means that the alignment is to be considered at right angles to the joining direction.

Additionally or alternatively, the angle of the laser (laser axis or the axis of the laser beam) to the surface of the component and in the joining direction between -25 and + 25 ° can be selected. 0 ° corresponds to a perpendicular or right-angled alignment to the surface of the component.

The distance between the center point (laser axis) of the spot diameter and the center point (tip) of the filler metal can be selected between 0.5 and 10 mm, in particular between 1 and 5 mm. For example, both methods (laser / MSG) or their arrangements can be spatially and temporally arranged in such a way that they do not act in a common weld pool.

The speed of the filler material can be selected between 3 and 28 m / min, in particular between 8 and 25 m / min.

The thickness of the filler metal can be selected between 0.8 and 1.6 mm.

The welding current of the MSG process can be selected between 100 and 400 A, in particular between 120 and 380 A.

The welding voltage of the MSG process can be selected between 15 and 35 V, in particular between 18 and 32 V.

According to one embodiment of the method according to the invention, an iron-based or copper-based filler material can be used for the MSG welding method. Preferably, a filler material with a yield point is used which essentially corresponds to the yield point of the component with the lower yield point.

According to one embodiment of the method according to the invention, the second component and / or first component can consist of steel material with the following chemical composition in% by weight:

C = 0.05 to 0.5, in particular C = 0.15 to 0.45, Mn = 0.3 to 3.0, Si = 0.05 to 1.7, P to 0.1, S to 0 , 1, N to 0.1, and optionally one or more alloy elements from the group (Al, Ti, V, Nb, B, Cr, Mo, Cu, Ni, Ca):

AI up to 1.0,

Ti up to 0.2,

V up to 0.5,

Nb up to 0.5,

B to 0.01,

Cr up to 1.0,

Mon to 1.0,

Cu up to 1.0,

Ni up to 1.0,

Ca to 0.1,

Remainder Fe and unavoidable impurities. In particular, the steel material has been austenitized and hardened before being made available. The steel material can be austenitized and hardened in the course of direct or indirect hot forming. Direct hot forming is based on an essentially flat sheet metal blank (steel material), which is hot formed and hardened, in particular press hardened. Indirect hot forming is based on a preform (steel material) which has been cold preformed from a sheet metal blank, which is postformed in the warm state and / or calibrated to final dimensions and hardened, in particular press hardened. The steel material, whether flat or preformed, is in particular heated or austenitized to a temperature of at least Ac3, preferably heated to a temperature which is higher than Ac3, so that a complete and global conversion into austenite can be ensured. That (Press) hardening takes place in at least one (press) hardening tool, which in particular is actively cooled and provides corresponding (critical) cooling speeds in order to set the conversion of austenite into a hard structure comprising essentially martensite and / or bainite in the second component to be able to. Parameters such as Acl, Ac3, (critical) cooling rates etc. depend on the composition of the steel material used and can be derived from so-called ZTU or ZTA diagrams.

The first and / or second component, which is preferably hardened, can have a structure made of martensite with at least 50%, in particular at least 60%, preferably at least 70%, preferably at least 80%, particularly preferably at least 90%, with others or remaining Structural components in the form of bainite, austenite, retained austenite, cementite, pearlite and / or ferrite can be present. In particular, the remaining non-martensitic structural component consists for the most part of bainite, it being possible for pearlite and / or ferrite to be present with up to 10%, preferably with up to 5%. The structure preferably consists of 100% martensite, whereby the highest possible hardness, in particular in connection with the corresponding alloying elements used, can be provided. The structure can optionally have up to a maximum of 2% production-related, unavoidable structural components such as cementite and / or other precipitates such as carbides, nitrides and / or oxides and their mixed forms.

All information on the contents of the alloying elements specified in the present application are based on weight, unless expressly stated otherwise. All contents are therefore to be understood as figures in% by weight. The specified structural components are determined by a suitable evaluation method, e.g. B Evaluation of light or electron microscopic examinations, in particular, determined on one or more micrographs and are therefore to be understood as area proportions in area%, unless expressly stated otherwise. An exception to this is the structural component austenite or retained austenite, which is specified as a volume percentage in% by volume, unless expressly stated otherwise.

According to a second aspect, the invention relates to a steel vehicle wheel comprising a wheel rim with a wheel disc that is thermally and cohesively connected to the wheel rim. According to the invention, the joint between the wheel rim and the wheel disk is a laser-MSG hybrid joint. In order to avoid repetition, reference is made to the explanations relating to the method according to the invention.

According to a preferred embodiment of the steel vehicle wheel according to the invention, the wheel rim and the wheel disc are joined together in the flanged joint and the joint comprises a joint which has a depth (T) and a width (B) with a ratio of T / B> = 1. The ratio T / B can in particular be> = 1.3, preferably> = 1.5, preferably> = 1.7 in order to create a joint connection between the wheel rim and the wheel disk in such a way that the highest possible load-bearing capacity results under operating loads. For example, unlike conventional constructions, the structure carrying the tire flanks and producing the tightness cannot be formed by the wheel rim, but is created by welding the wheel disc to the wheel rim, particularly preferred in so-called full-face steel vehicle wheels. Depth means the alignment of the joint seam in its longest extent in cross section from the top layer to the root or corresponds to the seam thickness, and width means the alignment of the joint seam in its longest extent essentially at right angles to the depth in cross section or seam width , whereby the heat affected zone is not taken into account in this view. The expression “essentially” can be understood to mean deviations between +/- 20%, in particular between +/- 10%, preferably between +/- 5, which means at right angles and 90 ° that the maximum range is from 72 ° to 108 ° is to be understood as essentially rectangular.

In order to reduce the geometric notch effect, according to a further embodiment of the steel vehicle wheel according to the invention, the wheel rim can have a flange for joining to the wheel disc, which defines an extension or width which corresponds to a radius with which the flange is smaller than or equal to the remaining part the wheel rim is bent. In particular, the extent or width is <= 0.8 * radius, preferably <= 0.6 * radius. The extension or width can be understood as the length between the front edge of the flange and the transition into the radius. The extension can also be 0, so that there is then no classic flange but only the transition or part of the transition of the curved area of the wheel rim. Particularly preferably, the area of the front edge of the flange or the curved sub-area of the wheel rim can also be covered by the joining seam, either part of the front edge (in certain areas) or the front edge is completely covered by the joining seam. The second component or the wheel disc can have a thickness of 3 to 6 mm. The steel vehicle wheel is preferably intended for use on passenger vehicles.

The second component or the wheel disc can have a thickness of 4 to 10 mm. The steel vehicle wheel is preferably intended for use on trucks or utility vehicles.

Brief Description of Drawings

The invention is explained in more detail below with reference to drawings. The same parts are provided with the same reference symbols. Show in detail:

1 shows a part of a steel vehicle wheel in cross section produced by means of a conventional joining process,

2 shows a part of a steel vehicle wheel in cross section according to a first embodiment of the invention,

3 shows a part of a steel vehicle wheel in cross section according to a second embodiment of the invention and

4 shows a part of a steel vehicle wheel in cross section according to a third embodiment of the invention.

Description of the Preferred Embodiments (Best Mode for Carrying out the Invention)

Figures 1 and 2 show a comparison of a steel vehicle wheel joined by means of MSG welding process, Figure 1, and a steel vehicle wheel according to the invention joined by means of laser MSG hybrid process (3), Figure 2. In both cases, a first component (1 ) made of steel and a second component (2) made of steel, which corresponded to a wheel rim (1) and a wheel disc (2), an assembled steel vehicle wheel being produced by means of different thermal, cohesive joining of the first and second components. The joint connection in FIG. 1 is an MSG joint connection and that in FIG. 2 is a laser-MSG hybrid joint connection (4), which were each formed in the flanged joint. The embodiments shown in this case relate to a full-face steel vehicle wheel. The first component (1) was made from one Steel material of quality S420MC formed, for example by means of profiling and / or pressure rolling. The wheel rim (1) has a flange (1.1) for joining to the wheel disc (2), which defines an extension (bl) which is less than or equal to the radius (rl) with which the flange (1.1) is separated from the rest of the part the wheel rim (1) is bent over. The flange (1.1) had a thickness of 1.8 mm. The second component (2) was each formed from a manganese-boron steel material of the quality 22MnB5, which was preferably austenitized and hardened. The thickness of the second component (2) was 4.35 mm.

The MSG welding process was carried out as MAG welding on a welding system from SKS Welding, with a filler material, which is available under the trade name Union K 56, in wire form with a diameter of 1 mm and a wire feed rate of 9 m / min, with a protective gas of 90% argon and 10% carbon dioxide and a gas throughput of approx. 13 l / min. The welding current and voltage were 180 A and 25 V. The joining speed was approx. 0.7 m / min, with high heat input. As can be seen from FIG. 1, it was not possible to produce a flawless joint seam. The illustration in FIG. 2 is different. A system comprising a laser arrangement with a fiber laser with the trade name "YLS-10000" from IPG, which was operated with the following parameters: Ytterbium laser with a wavelength of 1070 nm, power of 4, 5 kW, focus position of +/- 0 mm, fiber diameter 400 pm, spot diameter 600 pm, collimation 200 mm, focal length 300 mm, joining speed 2 m / min, angle (a) across the joining direction + 5 °, angle in joining direction 0 °, Distance between the center (laser axis) of the spot diameter and the center (tip) of the filler material 3 mm, whereby the laser was guided leading in the joining direction; and downstream MAG welding arrangement with the trade name "TransPuls Synergie 5000 CMT" from Fronius, which was operated with the following parameters: Filler material Union K 56 in wire form with a diameter of 1 mm and a wire feed rate of approx. 22 m / min, shielding gas 82% Argon and 18% carbon dioxide with a gas throughput of approx. 25 l / min, welding current 356 A, welding voltage 24.8 V. The heat input was lower compared to the pure MSG welding process.

In FIGS. 3 and 4, further designs are shown, the same parameters as those used in the design of FIG Width (bl) is defined and corresponds to a radius (rl) with which the flange (1.1) has been bent over from the remaining part of the wheel rim (1), where bl <= rl, see FIG. 2, in particular bl <= 0.8 * rl, see FIG. 3, preferably bl <= 0.6 * rl, see FIG. 4. The joint seam (5) preferably encompasses the front edge (1.2) of the flange (1.1) or the front edge of the curved sub-area of the wheel rim (1) in certain areas or completely, see FIGS. 3 and 4. The depth (T) and the width (B) the joint seam (5) can be designed to be particularly resilient, the ratio T / B being> = 1, in particular> = 1.3, preferably> = 1.5, preferably> = 1.7. As a result of the deep and qualitatively very robust design of the joint connection (4), additional weight can be saved by adapting the extension (bl) of the flange (1.1) of the wheel rim (1), which on the one hand benefits the rotating mass and the geometric notch.

The features described can all be combined with one another as far as technically possible. The design of the steel vehicle wheel is not limited to the full-face design (joining seam in the full flow of force), but can also be advantageously transferred to steel vehicle wheels with a drop center (additional force / form fit) and others. This applies to steel vehicle wheels for passenger cars as well as for trucks or utility vehicles.

Claims

Expectations

1. A method for manufacturing a steel vehicle wheel (3), the method comprising the following steps:

- Providing a first component made of steel, which corresponds to a wheel rim (1), and a second component made of steel, which corresponds to a wheel disc (2);

- Thermal, cohesive joining of the first and the second component in order to produce an assembled steel vehicle wheel (3), characterized in that a laser-MSG hybrid process is used for the thermal, cohesive joining.

2. The method according to claim 1, wherein a laser arrangement is guided in the joining direction before or after an MSG arrangement.

3. The method according to any one of the preceding claims, wherein the joining speed is between 1 and 5 m / min.

4. The method according to any one of the preceding claims, wherein the power of the laser is between 3 and 10 kW.

5. The method according to any one of the preceding claims, wherein a filler material is used for the MSG welding process based on iron or copper.

6. The method according to any one of the preceding claims, wherein the second component and / or the first component consists of a steel material with the following chemical composition in% by weight:

C = 0.05 to 0.5,

Mn = 0.3 to 3.0,

Si = 0.05 to 1.7,

P to 0.1,

S to 0.1,

N to 0.1, and optionally one or more alloy elements from the group (Al, Ti, V, Nb, B, Cr, Mo, Cu, Ni, Ca): AI up to 1.0,

Ti up to 0.2,

V up to 0.5,

Nb up to 0.5,

B to 0.01,

Cr up to 1.0,

Mon to 1.0,

Cu up to 1.0,

Ni up to 1.0,

Ca to 0.1,

The remainder is Fe and unavoidable impurities, the steel material having been austenitized and hardened before being made available.

7. Steel vehicle wheel (3) comprising a wheel rim (1) with a wheel disc (2) thermally and cohesively connected to the wheel rim (1), characterized in that the joint connection (4) between the wheel rim (1) and the wheel disc (2) is a laser MSG Flybrid joint.

8. Steel vehicle wheel according to claim 7, wherein the wheel rim (1) and the wheel disc (2) are joined to one another in the flanged joint and the joining connection (4) comprises a joining seam (5) which has a depth (T) and a width (B ) with a ratio of T / B> = 1.

9. Steel vehicle wheel according to claim 7 or 8, wherein the wheel rim (1) has a flange (1.1) for joining to the wheel disc (2) which defines an extension (bl) which corresponds to less than or equal to the radius (rl) , with which the flange (1.1) is bent over from the remaining part of the wheel rim (1).

10. Steel vehicle wheel according to claim 8 or 9, wherein the joining seam (5) partially or completely covers the front edge (1.2) of the flange (1.1) or the front edge of the curved portion of the wheel rim (1).

11. Steel vehicle wheel according to claim 7 or 8, wherein the wheel disc (2) has a thickness of

3 to 6 mm and is intended as a steel vehicle wheel (3) for use on a passenger car.

12. Steel vehicle wheel according to claim 7 or 8, wherein the wheel disc (2) has a thickness of

4 to 10 mm and is provided as a steel vehicle wheel (3) for use on a truck or commercial vehicle.