DE102021120263A1 - Process and device for producing a coated structural component - Google Patents

Abstract

The present invention relates to a method for producing a coated structural component (10) for a vehicle, comprising the steps: providing a base component (11), hot forming the base component (11) into a molded component (12), electrochemical deburring of the molded component (12), and electrolytic application of an anti-corrosion layer (13) to the deburred molded component (12) to produce the structural component (10). The invention also relates to a device for carrying out a method according to the invention for producing a deburred and coated structural component.

Description

The present invention relates to a method for producing a coated structural component for a vehicle. The invention also relates to a device, in particular an industrial plant, for producing such a structural component.

In the automotive industry, hot-formed components are used to manufacture body shells. Various process variants are known for producing the formed components. On the one hand, uncoated sheet metal components are used, which are hot-formed and hardened from flat, uncoated sheet metal in a so-called direct process. According to a further variant, sheet metal components are coated in the steel works with an alloy, for example an aluminum-silicon alloy, and then also hot-formed and hardened in the direct process. This variant is by far the most commonly used in practice. As an alternative to this process, coated sheet metal components, for example galvanized ones, are used, which are cold-formed and cut to the desired dimensions. Only then is the component heated and hardened in a tool. This process is called the indirect process.

In practice, direct process methods are preferred because they are generally quicker and easier to carry out and are more cost-effective due to lower investment in tools. As an alternative to the methods described above, a method was developed in which the sheet metal components to be produced are first hot-formed in the direct process and then electrolytically coated with an anti-corrosion layer. The components are then tempered to expel any hydrogen from the material. The problem here, however, is that during the forming process, an oxide layer regularly flakes off the sheet metal components, which forms when heated to 900°C, for example. This means that oxide formation on the circuit board before it is placed in the tool cannot usually be completely avoided. The build-up of the oxides in the tool leads to grooves in the component and material to be thrown up in the edge area of the grooves. The throw-up can be sharp-edged and/or form points. If the peaks and/or bulges are too high, they can no longer be adequately covered by a subsequent and/or additional coating. If the vehicle is then subjected to stress during the use phase, for example by moisture and/or salt, there is a risk that the structural component will begin to corrode, starting from these peaks. The allegations should therefore be prevented or at least reduced as far as possible.

The object of the present invention is to at least partially take account of the problems described above. In particular, the object of the present invention is to create a method and a device for producing a coated structural component made from a sheet metal component while avoiding or reducing peaks and/or warps.

The above object is solved by the patent claims. In particular, the above object is achieved by the method according to claim 1 and the device according to claim 10. Further advantages of the invention result from the dependent claims, the description and the figures. Features that are described in connection with the method also apply, of course, in connection with the device according to the invention and vice versa, so that the disclosure of the individual aspects of the invention is and/or can always be referred to alternately.

• - Bereitstellen eines Grundbauteils,
• - Warmumformen des Grundbauteils in ein Formbauteil,
• - elektrochemisches Entgraten des Formbauteils, und
• - elektrolytisches Auftragen einer Korrosionsschutzschicht auf das entgratete Formbauteil.

According to a first aspect of the present invention, a method for producing a coated structural component for a vehicle is provided. The procedure has the following steps:

• - providing a basic component,
• - hot forming of the basic component into a molded component,
• - electrochemical deburring of the molded component, and
• - Electrolytic application of an anti-corrosion layer to the deburred molded component.

Within the scope of the present invention, it was recognized that the process of electrochemical deburring can be advantageously implemented in a direct process for producing a structural component for a vehicle. That is, the method is to be understood in particular as a method for producing a coated structural component for a vehicle according to a direct process. Compared to conventional forming methods, structural components with an improved surface quality, in particular without peaks and/or bulges, which can subsequently lead to damage to the structural component, can thus be created in a simple and reliable manner. Correspondingly advantageous corrosion resistance can be achieved by means of a comprehensive anti-corrosion layer. Electrochemical deburring is already enough a relatively thin anti-corrosion layer in order to achieve the desired surface coverage.

A further advantage of the procedure according to the invention is that no special precautions have to be taken with regard to the base component during hot forming. This means that no special temperature and/or heating curves have to be observed and/or restrictions in this regard have to be taken into account. The heating process can thus be carried out in a correspondingly simple manner. In particular, an uncoated base component, preferably in the form of a sheet metal component, is used for the base component. For example, a simple sheet metal component, in particular a simple sheet steel component such as a sheet metal component made of 22MnB5 steel or manganese-boron steel with a tensile strength of approximately 2000 MPa, can be used. The sheet metal component can be understood to mean a circuit board. The base component can have a thickness in a range between 0.5 mm and 6 mm, in particular in a range between 0.7 mm and 3 mm. Within the specified framework, the base component can have different sheet metal thicknesses and/or different materials at different locations. Furthermore, the base component can have different strengths at different points, which can be achieved, for example, by different cooling curves.

The electrochemical deburring and the electrolytic application of the anti-corrosion layer are preferably carried out in direct succession. This means that after the molded component has been deburred electrochemically, it can be moved immediately afterwards for the electrolytic application of the anti-corrosion layer, for example in an immersion bath and/or at least partially in a suitable electrolyte.

Hot forming is preferably carried out in the direct process. In the context of hot forming, the base component is first heated to a predefinable temperature, for example to a temperature in a range between 800° C. and 1000° C., and then formed or brought into the desired shape. When the base component is heated up, scaling of the base component can be reduced by means of a protective gas in the furnace or by using a vacuum furnace.

The structural component can be understood in particular as a body component for a vehicle. Several structural components can also be produced simultaneously as part of the process. In particular, several molded parts can be deburred electrochemically at the same time.

For the electrochemical deburring of the molded component, the molded component to be deburred is preferably hung in a frame. To smooth or deburr the desired area on the molded component, the cathode or several cathode parts can be positioned in the frame in a targeted manner. The cathode or the cathode parts can follow the geometry of the molded component. The cathode preferably consists of an electrically conductive material, in particular stainless steel or titanium. The cathode is preferably provided as a flat or wire-shaped component. In the deburring process, the molded component forms the anode. The electrochemical deburring is preferably carried out specifically on surface sections of the molded component, ie in particular not or at least not specifically on end edges, end sections and/or projections of the molded component.

According to a further embodiment of the present invention, it is possible for the molded component to have at least one forming edge produced by hot forming with a forming radius in one method, with the electrochemical deburring for deburring at least one surface section adjacent to the at least one forming edge, i.e. for the targeted removal of, for example Grooves in the surface section next to the at least one forming edge is carried out. This means that the electrochemical deburring is carried out in a targeted manner on surface sections of the molded component that are configured next to the at least one forming edge, and in particular not or at least not specifically on the at least one formed edge, end edges and/or end sections of the molded component. Accordingly, the electrolyte, the temperature of the electrolyte, the treatment time for the deburring and in particular the positioning of the at least one cathode on the molded component are designed or specified with reference to the at least one surface section to be deburred. It is fundamentally known in the prior art to electrolytically deburr complex components and/or in particular their cut and/or production edges or end edges. According to the invention, however, electrochemical deburring is now used specifically for deburring segments and/or surfaces of the component that are exposed to relative movement between the workpiece and the tool during forming and are therefore subject to the potential risk of scoring. According to the invention, this can be easily and effectively integrated into the previously known manufacturing process, which includes electrochemical coating of a molded component. Within the scope of the method, at least two forming edges can be produced by hot forming, with the electrochemical deburring for deburring at least one surface section between the at least two forming edging is carried out. In this case, the surface section can be understood in particular as a straight and/or level or, apart from any grooves, straight, level and/or relatively smooth surface section. The forming radius can be understood to mean a bending radius, an inner radius and/or an outer radius of the at least one forming edge and/or on the at least one forming edge.

In a method according to the invention, in particular a zinc coating is applied as the anti-corrosion layer. The zinc coating can be understood to mean a zinc-containing coating and/or alloy. The application of an anti-corrosion layer can therefore be understood as galvanizing. The zinc coating is preferably applied as part of an electrolytic coating. For electrolytic coating of the component, it can remain in the frame described above. The molded component is immersed with the frame in a suitable electrolyte and is connected as a cathode. Zinc that is as pure as possible is used for the anode. Additional anodes can be positioned close to the component to specifically influence the zinc layer. As part of the invention, it is proposed, so to speak, to electrochemically deburr the molded component in the galvanizing process sequence before galvanizing. As already mentioned above, bulges at the edge of the grooves and at least partially the grooves of the at least one molded component or in the area of an oxide layer of the molded component can be reduced to the desired minimum. For the reasons given in the introduction to the description, molded components have hitherto been produced either uncoated, i.e. without corrosion protection, without cathodic corrosion protection, or with, for example, a zinc-iron coating which, although cathodic corrosion protection is provided, has an electrochemical potential for galvanized components. The intermediate step proposed according to the invention of electrochemical deburring and the subsequent electrolytic galvanizing can now achieve the desired corrosion resistance in a simple and reliable manner and without loss of quality. In the case of electrochemical deburring, the molded component represents the anode and is at least partially immersed in an electrically conductive liquid, i.e. an electrolyte, during the process. The temperature of the electrolyte can be adjusted in a range between 30°C and 50°C during deburring. For this purpose, the cathode and/or cathode elements can be adapted to the geometry of the component. Compared to conventional galvanizing processes for uncoated and preformed sheet metal components, significantly smoother surfaces can be coated with a relatively thin, even and closed layer of zinc.

According to a further embodiment variant of the present invention, it is possible that, in a method, after the zinc coating has been applied, a KTL coating is applied to the coated molded component. It has been shown that a KTL coating applied in addition to a zinc coating, for example, regularly does not adequately cover the surface of the structural component due to burrs in the molded component or in the originally formed basic component. In particular, edges and/or peaks, which can still be pronounced in the first corrosion coating, can no longer be adequately covered by the relatively thin KTL coating. In other words, the tips of the grooves and/or chunks, which are usually still covered with zinc, are covered only insufficiently or not at all by the subsequent KTL coating. These spots can be the starting point of corrosion relatively quickly. This problem can be satisfactorily taken into account by deburring according to the invention even before the first coating process.

When carrying out the method according to the invention, it has been shown that a layer thickness of the KTL coating in a range between 10 μm and 40 μm can already be sufficient to provide a comprehensive or covering KTL coating. This means that the KTL coating can be applied with a layer thickness in a range between 10 μm and 40 μm, in particular in a range between 15 μm and 25 μm.

In a method according to the present invention, it is also possible that the electrochemical deburring of the shaped component is carried out by means of a cathode and anode, the shaped component being used as at least part of the anode and the cathode for the electrochemical deburring having a distance of less than 30 mm is positioned at the forming edge to at least one forming edge and/or a surface of the molded component to be deburred. In particular, the cathode can be positioned at a distance in a range between 5 mm and 30 mm, in particular between 10 mm and 20 mm, from the at least one forming edge and/or surface. In tests within the scope of the present invention, this distance has turned out to be particularly advantageous in order to realize the desired deburring reliably and nevertheless with relatively little effort for producing a tool for a suitable positioning of the molded component. The targeted positioning of the cathode in the vicinity of the at least one forming edge causes a effective deburring. The cathode may have multiple cathode elements. The cathode can be designed and/or fixed in a tool, for example in the form of a frame, in which the molded component for the electrochemical deburring is positioned at least partially in an electrolyte in a predefined position.

Furthermore, in a method according to the invention, the electrochemical deburring can be carried out with an electrolytic current density in a range between 5 A/dm ² and 15 A/dm ² . An operating or time period for the electrochemical deburring is preferably set to a value between 3 minutes and 12 minutes, in particular between 5 minutes and 10 minutes. That is, the electrochemical deburring can be performed for an appropriate period of time. For this purpose, the electrodes used, the currents used and/or the electrolyte can be adjusted and/or positioned accordingly. Advantageous deburring can be carried out with the operating time and/or current density described above. In addition, it has proven to be advantageous if an electrolyte with sodium sulphate and sodium chloride is used in a method according to the present invention for electrochemical deburring, with at least twice as much sodium sulphate being used as sodium chloride. An electrolyte with three times as much sodium sulphate as sodium chloride, for example in a ratio of 180 g/l sodium sulphate to 50 g/l sodium chloride, has proven particularly advantageous.

According to a further aspect of the present invention, a device for carrying out a method as described in detail above for producing a deburred and coated structural component in the form of a body component for a vehicle is provided. To carry out the method, the device, in particular in the form of an industrial plant, can have a preparation tool for preparing the basic component. The device also has a mold for forming the base component into the mold component, a deburring tool for carrying out the electrochemical deburring and/or a coating tool for carrying out the electrolytic application of the anti-corrosion layer and/or the KTL protective layer. The device according to the invention thus brings with it the same advantages as have been described in detail with reference to the method according to the invention.

Further measures improving the invention result from the following description of various exemplary embodiments of the invention, which are shown schematically in the figures. All of the features and/or advantages resulting from the claims, the description or the figures, including structural details and spatial arrangements, can be essential to the invention both on their own and in the various combinations.

• 1 ein Ablaufschaubild zum Erläutern eines Verfahrens gemäß einer Ausführungsform der vorliegenden Erfindung,
• 2 ein Ablaufschaubild zum Erläutern weiterer Details des erfindungsgemäßen Verfahrens,
• 3 ein Flussdiagramm zum Erläutern eines beispielhaften Ablaufs zum Herstellen eines erfindungsgemäßen Strukturbauteils, und
• 4 ein im Stand der Technik bekanntes, umgeformtes Strukturbauteil.

They each show schematically:

• 1 a flow chart for explaining a method according to an embodiment of the present invention,
• 2 a flowchart to explain further details of the method according to the invention,
• 3 a flowchart to explain an exemplary process for producing a structural component according to the invention, and
• 4 a formed structural component known in the art.

Elements with the same function and mode of operation are each provided with the same reference symbols in the figures.

1 FIG. 1 shows the various method steps for producing a structural component 10 for a motor vehicle according to a preferred embodiment. As in 1 shown, basic components 11 with a thickness of approx. 1.4 mm are first cut from a coil 18 . The sheet metal components are then heated to approximately 900° C. in an oven 22 and then given the desired shape by a forming tool 20 . That is, the heated and uncoated base members 11 in the form of circuit boards are formed into molded members 12 by the mold 20 . Even before the molded components are coated, they are trimmed and then electrochemically deburred. For this purpose, the molded component 12, which forms an anode 17 via the frame for suspending the molded component 12 in the electrolyte, is positioned on a cathode 16 or on plate-shaped cathode components. More precisely, the cathode 16 or cathode plates are positioned at a distance of approximately 10 mm from the molded component 12 on a surface section 14 between two forming edges 15 on the surfaces to be deburred.

The electrochemical deburring is carried out with an electrolytic current density of about 10 A/dm ² for about 8 minutes. A liquid with approx. 180g/l sodium sulphate and 50g/l sodium chloride at a temperature of approx. 40°C is used as the electrolyte. Subsequently, the electrochemically deburred shaped component 12 for producing the structural component 10 with an in 2 shown anti-corrosion layer 13 coated. More accurate said, a zinc layer is applied to the deburred molded component 12 by moving the deburred molded component 12 through an electrolyte 19 . After applying the corrosion coating 13, an additional in 2 KTL coating 21 shown with a layer thickness of about 20 microns applied over the entire surface of the coated molded part 12. For this purpose, the molded component 12 or structural component 10 coated with the corrosion layer 13 is moved through a KTL immersion bath 23 .

In the 1 The tools and aids shown for carrying out the method can be understood as components of a device for carrying out the method and thus for producing the deburred and coated structural component 10 .

2 shows the deburring and coating process in more detail. As in 2 As can be seen, the shaped component 12 has edges and tips that protrude above average after the forming in the region of a surface section 14 on closer inspection. These are removed or reduced and/or smoothed by electrochemical deburring. The corrosion layer 13 is then applied in the form of the zinc coating. Then the KTL coating 21 is applied.

Regarding 3 further embodiment variants for producing the structural component 10 are then described. In a first step S1, the coil 18 is initially provided, from which the base component 11 is provided in the form of a circuit board in a second step S2. In the direct process, the base component 11 is now heated to approximately 900° C. in step S3 and formed and press-hardened in step S4. In an indirect process, the base component 11 is first cold-formed in step S2a, which is carried out after step S2, and then cut to the desired shape in step S2b. In the indirect process, the heating according to step S3 follows only then. Step S2b can initially be dispensed with in the indirect process. In the direct process, press hardening or hot forming is usually carried out by means of intermediate cooling. Step S3 is followed in the direct process by the trimming of the molded component 12 in step S4 and the cleaning of the molded component 12 in step S5. In step S6, the molded component 12 is now cleaned and deburred electrochemically as described in detail above. In the indirect process, steps S4 and S5 can be skipped. Galvanizing follows in step S7. The molded component 12 can already be regarded as the structural component 10 described above. Step S7 is followed by annealing in step S8. The cleaned, galvanized and tempered structural component 10 is now oiled in step S9 in order to produce transport protection. In the subsequent step S10, possible subcomponents of the structural component 10 can be assembled. Another cleaning process takes place in step S11. Then, in step S12, the structural component 10, which until then can basically also be regarded as a molded component 12, is coated with a KTL coating 21.

4 12 shows a structural component 10a from the prior art in which the shaped component 12 was not deburred prior to galvanizing. In this case, the edges and points are still covered by the first anti-corrosion layer 13 . However, the KTL coating 21 is broken through by the anti-corrosion layer 13, as a result of which the structural component 10a only has a correspondingly lower corrosion resistance.

In addition to the illustrated embodiments, the invention permits further design principles. That is, the invention should not be considered limited to the exemplary embodiments explained with reference to the figures.

Reference List

10

structural component

10a

structural component

11

basic component

12

molded part

13

anti-corrosion layer

14

area section

15

forming edge

16

cathode

17

anode

18

coil

19

zinc bath

20

molding tool

21

KTL coating

22

Oven

23

KTL immersion bath

Claims (10)

Method for producing a coated structural component (10) for a vehicle, comprising the steps: - providing a base component (11), - hot-forming the base component (11) into a molded component (12), - electrochemical deburring of the molded component (12), and - electrolytic application of an anti-corrosion layer (13) to the deburred molded component (12) for producing the structural component (10). procedure after claim 1 , characterized in that the shaped component (12) has at least one forming edge (15) with a forming radius produced by hot forming, the electrochemical deburring for deburring at least one surface section (14) adjacent to the at least one forming edge (15) being carried out. Method according to one of the preceding claims, characterized in that a zinc coating is applied as the anti-corrosion layer (13). procedure after claim 3 , characterized in that after the application of the zinc coating (13), a KTL coating (21) is applied to the coated molded component (12). Method according to one of the preceding claims, characterized in that the KTL coating (21) is applied with a layer thickness in a range between 10 µm and 40 µm. Procedure according to one of claims 2 until 5 , characterized in that the electrochemical deburring of the shaped component is carried out by means of cathode and anode, the shaped component (12) being used as at least a part of the anode (17) and the cathode (16) for the electrochemical deburring with a distance of less than 30 mm to the at least one forming edge (15). Method according to one of the preceding claims, characterized in that the electrochemical deburring is carried out with an electrolytic current density in a range between 5 A/dm ² and 15 A/dm ² . Method according to one of the preceding claims, characterized in that the electrochemical deburring is carried out over a period of time in a range between 3 minutes and 12 minutes. Method according to one of the preceding claims, characterized in that an electrolyte with sodium sulphate and sodium chloride is used for the electrochemical deburring, with at least twice as much sodium sulphate being used as sodium chloride. Device for carrying out a method according to one of the preceding claims for producing a deburred and coated structural component (10) in the form of a body component for a vehicle.

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