Method for manufacturing a sheet metal component, in particular a part of a motor vehicle body

Abstract

The invention relates to a method for manufacturing a sheet metal component (10), wherein a plurality of sheet metal sections (14, 16) are joined to form a semi-finished product (12). At least one first sheet metal section (14) consists of bake-hardening steel and at least one second sheet metal section (16) consists of a material other than bake-hardening steel, wherein the sheet metal component (10) is formed from the semi-finished product (12) by means of a forming process.

Description

[0001] The invention relates to a method for manufacturing a sheet metal component according to the preamble of claim 1.

[0002] Sheet metal components of the type in question are manufactured by forming a semi-finished product. This process allows for the production of comparatively complex geometries and, thanks in particular to modern materials, the achievement of high strength in the resulting sheet metal components. Prior art patents, such as CN 106 623 675 A, US 2020 / 0338624 A1, and US 2466367 A, disclose methods for manufacturing sheet metal components for motor vehicle bodies by forming processes in which a semi-finished product is formed.

[0003] It is common practice to join multiple sheet metal sections to form a semi-finished product. Such semi-finished products are also referred to as "tailor-welded blanks" or "tailored blanks." This method allows for the production of sheet metal components where different areas of the component exhibit different material properties. This is achieved by using different materials for the sheet metal sections that make up the semi-finished product.

[0004] It has been shown that sheet metal components manufactured in this way can be advantageously adapted to local loads. Nevertheless, the known methods are subject to limitations, for example, with regard to the production of sheet metal components that combine high strength requirements with high degrees of deformation and / or require multi-stage forming processes due to the resulting geometries.

[0005] The invention is therefore based on the objective of demonstrating a method of the type mentioned at the outset that allows for greater flexibility with regard to the design possibilities of the resulting sheet metal components, particularly with regard to the production of large parts of a motor vehicle body.

[0006] The problem is solved by a method having the features of claim 1. The features of the dependent claims relate to advantageous embodiments.

[0007] The process involves joining multiple sheet metal sections to form a semi-finished product. This joining can be achieved through welding. Specifically, the sheet metal sections are butt-welded. Welding can be performed using a laser welding process.

[0008] At least one initial sheet section consists of bake-hardening steel. Bake-hardening steel is defined as steel that undergoes a controlled aging process after being heated to an aging temperature, resulting in increased strength. Specifically, bake-hardening steels are those in which fine precipitates, particularly Cottrell clouds, form during the controlled aging process. These Cottrell clouds are formed by carbon and / or nitrogen atoms dissolved in the iron lattice. During the aging process, atoms embedded in interstitial sites diffuse towards dislocations, thereby impeding dislocation movement and thus increasing strength.

[0009] At least one second sheet metal section consists of a material other than bake-hardening steel. This material may also be a steel.

[0010] Multiple sheet metal sections made of identical bake-hardening steel or different bake-hardening steels can be joined to the semi-finished product. Likewise, multiple second sheet metal sections made of the same additional material and / or of different additional materials other than bake-hardening steels can be joined to the semi-finished product. Accordingly, the resulting component can have multiple areas made of an identical bake-hardening steel and / or multiple areas made of different bake-hardening steels. Similarly, the resulting component can have multiple areas made of an identical additional material and / or multiple areas made of different additional materials. For the sake of simplicity, the term "bake-hardening steel" will be used in the following to refer to both identical and different bake-hardening steels.Similarly, the term "further material" is used collectively for identical and / or different further materials whose common property is that they are not bake-hardening steels.

[0011] The process further stipulates that the sheet metal component is formed from the semi-finished product using a forming process. This forming process, in particular, gives the semi-finished product a three-dimensional structure.

[0012] The forming process can comprise a first forming step and a second forming step performed after the first. Such a two-step forming process makes it possible, in particular, to exploit the different properties of bake-hardening steel and of bake-hardening steels combined with various other materials in conjunction with the forming process.

[0013] The first forming step can be hot forming. Hot forming processes are characterized in particular by the fact that the forming takes place while the temperature of the semi-finished product being formed is above the recrystallization temperature of the material. The advantage of such a hot forming step is that comparatively high degrees of deformation can be achieved.

[0014] The first forming step can involve placing the semi-finished product, at a temperature of at least 750 °C, in particular at least 800 °C, and / or at most 950 °C, in particular 950 °C, into a forming tool used for the first forming step. In this way, hot forming can be achieved.

[0015] The first forming step can involve hot forming using a cooled forming tool. Such hot forming operations with cooled forming tools are also known as die hardening or press hardening. Cooling the formed semi-finished product can increase the strength of the resulting material.

[0016] The material used in at least one second sheet metal section can be a steel that experiences an increase in strength during the forming process due to cooling in a forming tool. In particular, it can be a steel that experiences an increase in strength during the first forming step due to cooling in the forming tool. In this context, the forming tool can be a cooled, especially a water-cooled, forming tool. Such forming tools are able to dissipate the heat energy from the cooling steel in a relatively short time. The steel can experience this increase in strength primarily due to the formation of martensite.

[0017] The process can provide that, after the forming process, the sheet metal component is heated to an aging temperature specific to the bake-hardening steel to increase its strength. In particular, the process can provide that, after the second forming step, the sheet metal component is heated to an aging temperature specific to the bake-hardening steel to increase its strength. Such a process makes it possible to achieve high degrees of deformation during the forming of at least one initial sheet metal section made of bake-hardening steel, while still achieving sufficiently high strength levels.

[0018] The process can provide that the aging temperature is at least 150 °C, in particular at least 160 °C, and / or at most 190 °C, in particular at most 180 °C. Upon reaching these temperatures, a sufficient aging rate is typically achieved in bake-hardening steels.

[0019] Heating the sheet metal component to the aging temperature can be carried out particularly in conjunction with a surface treatment. This surface treatment could, for example, be cathodic dip coating (e-coating). Since heating the sheet metal component is regularly necessary anyway during such surface treatments, the aging step can be combined with the surface treatment to enable an energy-efficient process.

[0020] The process can include a bending process as the second forming step. Bending processes are particularly well-suited for producing localized deformations of workpieces. Areas of the workpiece can be deformed while other areas remain undeformed, although their spatial orientation relative to each other changes due to the bending. Against this background, the bending process is particularly suitable as a second forming step, or as a component of the second forming step, when areas of the workpiece have already undergone an increase in strength and are therefore no longer well-suited for further forming. This can be the case in the described process, in particular, if areas of the material have already experienced an increase in strength during the first forming step.

[0021] Therefore, the bending process can be used advantageously, particularly in the second forming step. The bending process allows, in particular, the modification of the relative spatial orientation of two areas of the sheet metal component relative to each other. These are especially relevant for areas of the sheet metal component formed from second sheet metal sections of the semi-finished product that were formed in the first forming step. In this way, geometries of the sheet metal component can be realized that are difficult to produce using conventional methods. Specifically, sheet metal components with areas angled relative to each other and with three-dimensional shapes can be created.

[0022] The process can, in particular, provide that a section of the sheet metal component formed from the first sheet metal section of the semi-finished product is formed in the second forming step. In this way, the properties of the bake-hardening steel can be advantageously utilized. While, especially during the first forming step, areas of the further material can already experience an increase in strength, the section of the sheet metal component formed from the first sheet metal section of the semi-finished product remains readily formable, so that it can be formed in the second forming step.

[0023] The areas of the sheet metal component formed in the first forming step, whose relative orientation to each other is changed by the second forming step, can be connected to each other, in particular, by the area formed in the second forming step which is formed from the first sheet metal section.

[0024] The process can include a bending procedure comprising multiple bending operations, each of which reshapes multiple areas of the sheet metal component, each area formed from a first sheet metal section of the semi-finished product. The individual bending operations can be performed simultaneously and / or sequentially. This enables the production of complexly shaped sheet metal components, which can be designed to enclose a spatial area from multiple sides.

[0025] The process can be designed for sheet metal components that are part of a vehicle body. Such a body part can be designed to enclose a portion of the vehicle's interior from multiple sides. In this context, the process offers the particular advantage of producing sheet metal components with relatively large, angled, and complex three-dimensional shapes. Advantageously, despite such complex geometry, a strength-enhancing heat treatment can be integrated into the process. This allows for the production of relatively large sections of a vehicle body in just a few process steps.

[0026] The process may, in particular, provide that the sheet metal component has at least two areas formed from second sheet metal sections of the semi-finished product, one area of ​​which forms at least part of the roof or at least part of the floor of the motor vehicle body, and the other area of ​​which forms at least part of an end wall, part of a front, part of a rear, or part of a side of the motor vehicle body. The two areas may be connected by an area formed in the second forming step from the first sheet metal section of the semi-finished product.It has been found that this process is particularly well suited to forming transitions between areas of a motor vehicle body that are oriented at an angle to each other, such as a transition between the underbody and the front wall of a motor vehicle body or the roof and the sides of a motor vehicle body, by means of the second forming step.

[0027] The process can, in particular, provide that the sheet metal component has a plurality of areas formed from second sheet metal sections of the semi-finished product, each of which forms at least a part of the roof or at least a part of the floor, a part of an end wall, a part of a front, a part of a rear, or a part of a side of the motor vehicle body, and which are connected by a plurality of areas formed in the second forming step and formed from first sheet metal sections of the semi-finished product. In this way, large parts of the body of a motor vehicle can be manufactured as a continuous sheet metal component in a comparatively small number of steps.

[0028] The invention also relates to a motor vehicle manufactured according to the described method or to a motor vehicle whose body is manufactured at least in part according to a method described above.

[0029] Further practical embodiments of the invention are described below in connection with the drawings. They show schematically: Fig. 1 an exemplary semi-finished product, Fig. 2 one from the in Fig. 1. The sheet metal component shown in the example semi-finished product is produced after the first forming step. Fig. 3 the sheet metal component made of Fig. 2 after the second forming step, Fig. 4 another alternative embodiment of a sheet metal component after the first forming step, Fig. 5 another alternative embodiment of a sheet metal component after the first forming step.

[0030] In the Fig. 1, Fig. 2 to Fig. Figure 3 shows different stages of an exemplary process for manufacturing a sheet metal component 10. Fig. Figure 1 shows a semi-finished product 12. The exemplary semi-finished product 12 is produced by joining a plurality of sheet metal sections 14 and 16 to form the semi-finished product. The sheet metal sections 14 and 16 can, for example, be joined together by laser welding with a butt joint. As in the example shown, the resulting semi-finished product 12 can have an edge contour 18 adapted to the desired shape of the sheet metal component 10 to be produced, and in particular cut-out areas 20.

[0031] There is at least one first sheet metal section 14, for example as in the one in the Fig. In Example 1, the first sheet metal sections 14 are made of a bake-hardening steel. Furthermore, at least one second sheet metal section 16 is made, for example, as in the example shown in the Fig. 1, Fig. 2 to Fig. In the third example shown, the second sheet metal sections 16 are made of a different material than bake-hardening steels. This other material could also be steel, for example. For visual emphasis, the positions of the first sheet metal sections 14 and the areas 22 of the sheet metal component 10 formed from the first sheet metal sections 14 are highlighted in the figures by dashed outlines.

[0032] The sheet metal component 10 is formed from the semi-finished product 12 using a forming process. As in the example shown in the figures, the forming process can comprise a first forming step and a second forming step, which is carried out after the first forming step. In the Fig. 2 is the sheet metal component 10 after the first forming step and in the Fig. Figure 3 shows the sheet metal component 10 after the second forming step.

[0033] The first forming step can be carried out using a cooled forming tool. This can be used to increase the strength of the subsequent material from which the areas 24 of the sheet metal component 10, formed from the second sheet metal sections 16, are made. The areas 22 of the sheet metal component 10, formed from the first sheet metal sections 14, are made of bake-hardening steel. This remains flexible after the first forming step.

[0034] The second forming step can, as in the example shown, include a bending process. Using the bending process, the spatial orientation of the areas 24, which are formed from the second sheet metal sections 16 formed in the first forming step, can be changed relative to each other. The bending process can be a plurality of bends, as in the examples shown. Fig. 1, Fig. 2 to Fig. The second example shown in section 3 includes bending operations. Each of the bending operations can be, as shown in the... Fig. 2 and Fig. 3 can be seen by way of example, in each case a section 22 of the sheet metal component 10 formed from a first sheet metal section 14 of the semi-finished product 10 is formed.

[0035] As exemplified in the Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. As shown in Figure 5, the sheet metal component 10 can be a part of a motor vehicle body. The method can provide, as in the examples shown, that the sheet metal component 10 has a plurality of areas 24 formed from second sheet metal sections 16 of the semi-finished product 12, each of which forms at least a part of the roof or at least a part of the floor, a part of an end wall, a part of a front, a part of a rear or a part of a side of the motor vehicle body, and which are connected by a plurality of areas 22 formed in the second forming step and formed from first sheet metal sections 14 of the semi-finished product 12.

[0036] In the case of the in the Fig. 1, Fig. 2 to Fig. In the example shown, three areas 24, formed from second sheet metal sections 16, are connected to each other by two areas 22, formed from first sheet metal sections 14. Two of the areas 24 form sides and one area 24 forms the underbody of a motor vehicle body.

[0037] In the Fig. 4 and Fig. In the 5 examples shown, the respective sheet metal component 10 is depicted after the first forming step.

[0038] The in Fig. The sheet metal component 10 shown as an example comprises five sections 24, which are formed from second sheet metal sections 16. The sections 24 are connected to each other by four sections 22, which are formed from first sheet metal sections 14. Two of the sections 24 form sides, and one section 24 each forms a roof, part of a front, and a rear of a motor vehicle body.

[0039] The in Fig. The sheet metal component 10 shown as an example comprises seven sections 24, which are formed from second sheet metal sections 16. The sections 24 are connected to each other by six sections 22, which are formed from first sheet metal sections 14. Two of the sections 24 form sides, and one section 24 each forms a roof, part of a front, a front wall, an underbody, and a rear of a motor vehicle body.

[0040] The features of the invention disclosed in the present description, the drawings, and the claims can be essential for realizing the invention in its various embodiments, both individually and in any combination. The invention can be varied within the scope of the claims and taking into account the knowledge of the person skilled in the art. Reference symbol list 10 sheet metal components 12 semi-finished products 14 first sheet metal section 16 second sheet metal section 18 Edge contour 20 cut-out area 22 area formed from a first sheet metal section 24 Area formed from a second sheet metal section QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] CN 106 623 675 A

[0002] US 2020 / 0338624 A1

[0002] US 2466367 A

[0002]

Claims

Method for producing a sheet metal component (10), wherein a plurality of sheet metal sections (14, 16) are joined to form a semi-finished product (12), wherein at least one first sheet metal section (14) consists of bake-hardening steel and at least one second sheet metal section (16) consists of a material other than bake-hardening steel, wherein the sheet metal component (10) is formed from the semi-finished product (12) by means of a forming process. Method according to claim 1, characterized in that the forming method comprises a first forming step and a second forming step carried out after the first forming step. Method according to claim 1 or 2, characterized in that the first forming step comprises hot forming, in particular hot forming using a cooled forming tool. Method according to one of the preceding claims, characterized in that the further material of the at least one second sheet metal section (16) is a steel which undergoes an increase in strength during the forming process, in particular during the first forming step, by its cooling in a forming tool. Method according to one of the preceding claims, characterized in that the sheet metal component (10) is heated to an aging temperature of the bake-hardening steel after the forming process, in particular after the second forming step, to increase the strength of the bake-hardening steel, in particular wherein the heating is carried out in connection with the execution of a surface treatment of the sheet metal component (10). Method according to one of the preceding claims, characterized in that the sheet metal sections (14, 16) are joined by means of a welding process, in particular a laser welding process. Method according to one of claims 2 to 6, characterized in that the second forming step comprises a bending process, in particular wherein the relative spatial orientation of two areas (24) of the sheet metal component (10) to each other, which are formed from second sheet metal sections (16) of the semi-finished product (12) formed in the first forming step, is changed by means of the bending process, in particular wherein an area (22) of the sheet metal component (10) formed from the first sheet metal section (14) of the semi-finished product (12) is formed by the second forming step. Method according to claim 7, characterized in that the bending method comprises a plurality of bending operations in which one of a plurality of areas of the sheet metal component (10), each formed from a first sheet metal section (14) of the semi-finished product (12), is formed. Method according to one of the preceding claims, characterized in that the sheet metal component (10) is a part of a motor vehicle body. Method according to claim 9, characterized in that the sheet metal component (10) has at least two areas (24) formed from second sheet metal sections (16) of the semi-finished product (12), one area (24) forming at least a part of the roof or at least a part of the floor of the motor vehicle body and the other area (24) forming at least a part of an end wall, a part of a front, a part of a rear or a part of a side of the motor vehicle body, and which are connected by an area (22) formed in the second forming step and formed from the first sheet metal section (14) of the semi-finished product (12).

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