Motor vehicle component and method for producing motor vehicle component

Abstract

The invention relates to a motor vehicle component (1) produced from a hardenable steel slab (9) by means of hot forming and press hardening, and to a method for producing a motor vehicle component (1), the motor vehicle component (1) having a reinforcing patch (10) which forms a double-layer structure (11) with the steel slab (9) at least in some regions, according to the invention, the motor vehicle component (1) has an opening (14) produced by thermal cutting in the region of the reinforcement patch (10), such that an opening (14) is formed in the reinforcement patch (10) and an opening (14) is formed in the sheet steel slab (9), and an edge region (16) preferably surrounding the opening (14) is pressed on the sheet steel slab (9) or the reinforcement patch (10) so as to be retracted relative to the other surface (18).

Description

Technical Field

[0001] This invention relates to a motor vehicle component manufactured by thermoforming and pressure hardening.

[0002] The present invention also relates to a method for manufacturing motor vehicle components. Background Technology

[0003] Thermoforming and pressure hardening technologies are known from existing techniques. This is particularly useful in the automotive industry for manufacturing sheet metal components for bodywork or other automotive parts.

[0004] For this purpose, a slab made of hardenable steel alloy is heated to a temperature above Ac3. This temperature is typically around 900°C or higher. This process is also known as austenitization. In this hot state, the component is particularly easy to form. This forming process is called hot forming.

[0005] If the component is formed in one step, it is then pressure-hardened in the next step. This process can also be called quenching hardening. Cooling is so rapid or fast from a temperature above the austenitizing temperature at a cooling rate that can also be called the critical cooling rate, that the previously austenitic structure transforms into a hardened structure, especially martensite. Here, the tensile strength Rm can be adjusted to be greater than 1000 MPa, especially greater than 1300 MPa, and depending on the steel alloy used, it can also be adjusted to be greater than 1500 MPa or greater than 1800 MPa.

[0006] Depending on the requirements, such high-strength or extremely high-strength components may need additional reinforcement. For this purpose, component patches or reinforcing patches are applied locally. The component patches themselves can also be made of hardenable steel alloys. However, component patches can also be made of other metals, especially steel alloys. It is particularly known that actual automotive components made from steel slabs are formed together with reinforcing plates. The reinforcing patches can be coupled to the steel slabs, for example, by welding or also by bonding.

[0007] Furthermore, it is known that such motor vehicle components are cut or perforated in internal or inner areas. For example, these could be openings for threading cables, connecting to other components, or other assembly openings, or mounting openings for other components.

[0008] Furthermore, so-called hot cutting is known in the prior art for this purpose. In this process, the steel slab is cut or pierced while in a hot state, therefore at its austenitizing temperature or in a residual hot state, thus before it is fully hardened. Therefore, the hot cutting process can occur before, during, or after hot forming, but before pressure hardening.

[0009] A motor vehicle component with a reinforcing patch and a method for manufacturing the motor vehicle component are known from DE 10 2011 105 514 A1. Summary of the Invention

[0010] The purpose of this invention is to provide a feasible solution for precise and low-cost geothermal cutting reinforcement of components, based on existing technologies.

[0011] Therefore, this invention specifies that motor vehicle components are manufactured from hardenable steel sheet through hot forming and pressure hardening. Motor vehicle components are particularly motor vehicle pillars, such as A-pillars, B-pillars, or C-pillars, roof frames, or windshield frames. However, motor vehicle components can also be other body or chassis components of a motor vehicle.

[0012] The vehicle component has reinforcing patches that form a double-layer structure with the steel sheet at least partially. Therefore, the vehicle component is locally reinforced at different locations by corresponding reinforcing patches. The vehicle component is manufactured by thermoforming and pressure hardening and preferably has a local tensile strength of at least Rm greater than 1000 MPa, particularly 1300 MPa, and preferably greater than 1500 MPa.

[0013] According to the invention, the motor vehicle component is characterized by having an opening manufactured by thermal cutting within the region of the reinforcing patch. The opening is manufactured continuously, thus extending through the entire wall thickness. Therefore, the material is completely cut through the region of the opening. Thermal piercing can also be used instead of thermal cutting, especially when the opening is circular, particularly preferably circular. However, the opening can also be constructed as elliptical or polygonal. Thus, the opening extends through the formed steel blank and the reinforcing patch. These two openings, namely the opening in the steel blank and the opening in the reinforcing patch, are aligned. In particular, these two openings have the same geometric dimensions because they are manufactured using a cutting tool or a piercing punch.

[0014] According to the invention, it has proven advantageous if the area surrounding the opening is pressed back on a member, and thus on a formed steel blank or reinforcing patch, relative to another surface. The pressed portion is manufactured by pure material displacement. No separation or cutting process is performed in the sense of pressing. This means, in the sense of the invention, that the surface surrounding the opening is retracted or pressed in the direction of the wall. According to the invention, this can thereby compensate for the formation of burrs during hot cutting or punching. Especially in areas of double-layered structures, it is difficult to perform the corresponding cutting or punching processes. By counter-pressing, on the one hand, the total wall thickness in this area is reduced, and on the other hand, the possible formation of burrs is no longer constructed to protrude and therefore does not protrude beyond the surface of the member.

[0015] The retracted pressing portion is retracted by 4% to 40%, preferably 8% to 35%, and especially 12% to 30%, relative to the other surface surrounding the pressing portion itself. 4% to 20% refers to the wall thickness of the steel slab or reinforcing patch having the pressing portion. Therefore, it can be referred to as the pressing portion or the embossed portion.

[0016] Within the scope of this invention, "surrounding" means that the pressed portion is constructed at least on a portion of the circumference of the opening or hole edge. This pressed portion should constitute at least 30%, preferably at least 50%, especially at least 70%, and particularly preferably completely surrounding the opening. Alternatively, the pressed portion may consist of segments along multiple portions of its circumference.

[0017] Therefore, the pressed portion extends radially from the opening in the direction of the wall thickness, i.e., radially circumferentially in the transverse direction, and is at least 0.5 mm, preferably greater than 1 mm. However, it should protrude radially by less than 5 mm. This allows for the compensation of possible tolerances during the cutting process, thus reliably performing subsequent cutting in the area of ​​the pressed portion when initially creating the pressed portion on the precast material, and therefore for flat steel blanks or reinforcing patches.

[0018] Furthermore, preferably, the edge of the opening has burrs after pressure hardening, the length of which is less than 0.3 mm, particularly less than 0.2 mm. Preferably, the opening is constructed approximately burr-free on the exit side of the cutting tool or piercing punch by thermal cutting, especially in combination with a pressing portion and the resulting reduced wall thickness. In alternative structural variations, burrs are formed, particularly in the openings made by thermal cutting or thermal piercing. These burrs are then configured to be biased into the pressing portion. Thus, additional form fit is provided by the burrs.

[0019] Furthermore, particularly preferably, the wall portion of the opening has a smooth cut portion of more than 25%, especially more than 40%. Particularly preferably, the smooth cut portion is approximately >50%. This should be understood as the entire wall portion of the opening. Therefore, it constitutes a double-layer structure formed by the steel slab and the reinforcing patch. In particular, the steel plate (i.e., the reinforcing plate or steel slab) located on the pressing side or the piercing / punching side has a burr-free opening with almost 100% smooth cut portions.

[0020] In another preferred structural variation, a punch nut can be inserted into the opening. The punch nut then performs the punching of the opening itself and remains in the component.

[0021] The aforementioned component according to the invention is manufactured by means of a method having the following characteristics:

[0022] -Provides hardenable steel slabs and reinforcing patches,

[0023] - Coupling the two components in this way creates a double-layer structure between the steel slab and the reinforcing patch.

[0024] -Heating to a temperature above Ac3, wherein the pressing section is introduced after heating and before or during thermoforming.

[0025] - Thermoforming, in which a cutting operation is performed during or after thermoforming.

[0026] - Thermal cutting, wherein the cutting tool cuts on the back of the pressing section and ejects the cut material from the side of the pressing section.

[0027] - Pressure hardening is applied to the formed motor vehicle components.

[0028] Therefore, the first step is to provide steel slabs made of hardenable steel alloys and reinforcing patches that can also be made of hardenable steel alloys.

[0029] In one of the components, pressing is performed in this region, and an opening should subsequently be created in this region. This can be done on a pressing tool. The pressing portion is a reduction in wall thickness produced by the pressing process. Preferably, pressing is performed after heating to an Ac3 temperature. Thus, the pressing portion can be introduced into the material in a soft tectonic state. The pressing portion is then further, particularly preferably, pressed within the thermoforming tool itself. For example, there is an extension of the thermoforming tool present, thus creating the pressing portion, with the component remaining in the thermoforming tool in the thermoforming state, and preferably pierced at least on the opposite side by a piercing punch.

[0030] These two components, therefore the steel slab and the reinforcing patch, can be coupled to each other, for example, by welding or bonding.

[0031] The material is then heated to above Ac3 temperature or undergoes an austenitizing process. The provided molding material is then placed into a thermoforming tool. Hot cutting or hot piercing is then performed during or after the thermoforming process. A corresponding cutting tool (e.g., a piercing punch) initiates the cutting or piercing process on the back side of the pressed portion, causing the cut material on the side of the pressed portion to be ejected. Possible burr formation is based on the fact that the pressed portion, in its geometric extension, is constructed with a retraction relative to the surface compared to the opening to be created.

[0032] During hot cutting, the piercing punch can preferably penetrate the double-layer structure completely, allowing for direct retraction after the piercing motion to avoid thermal compression of the hole edge on the punch. Similarly, during the return motion, optimizing the outer circumferential surface of the piercing punch, for example through a punch geometry that slightly tapers towards the punch tip, can prevent undesirable, prolonged contact between the hole edge and the outer circumferential surface of the piercing punch.

[0033] Subsequently, the automotive components thus manufactured by thermoforming and hot cutting are pressure-hardened and removed from the thermoforming and pressure-hardening tools.

[0034] The pressing section itself can also be constructed on both sides, thus being introduced onto one side and the opposite side of the piercing punch. This facilitates the initial cutting process during the first impact of the piercing punch and accordingly forms burrs on the inlet and outlet sides of the piercing punch.

[0035] Preferably, the pressed portion is formed only in the cut edge region. The pressed portion is particularly constructed in a ring shape, or follows the given contour of the opening.

[0036] Particularly preferably, the cutting process is performed at a temperature between 480°C and 800°C, more preferably between 500°C and 800°C, and especially between 600°C and 730°C. The last temperature range, in particular, ensures a very smooth cut and burr-free opening, at least on the perforated side of the steel plate. Furthermore, the last temperature range is particularly advantageous in terms of tool wear. To prevent tool wear, the perforating male die itself, as well as the perforating female die or the tool protrusion that creates the pressing portion, can be coated with a protective layer, especially a ceramic coating. Attached Figure Description

[0037] Other advantages, features, characteristics, and aspects of the invention are described in the following drawings. These drawings facilitate a simple understanding of the invention. They illustrate:

[0038] Figure 1 The use of a reinforcing member according to the invention in a motor vehicle component is shown;

[0039] Figure 2 A method flow according to the invention for manufacturing a motor vehicle component according to the invention is shown, which is accompanied by the application of a pressing part.

[0040] List of reference numerals in the attached diagram:

[0041] 1. Motor vehicle component; 2. Door ring; 3. A-pillar; 4. B-pillar; 5. Sill; 6. Inner shell; 7. Outer shell; 8. Flange; 9. Steel slab; 10. Reinforcing patch; 11. Double-layer structure; 12. Spot weld; 13. Surface of 9; 14. Opening; 15. Pressed part; 16. Edge area of ​​14; 17. Wall thickness of 9; 18. Surface of 10; R, Radial direction; D15, Diameter of 15; D14, Diameter of 14. Detailed Implementation

[0042] In the accompanying drawings, the same reference numerals are used for the same or similar components, even if repeated descriptions or illustrations are omitted for simplification. The features described above and below can be combined arbitrarily without departing from the scope of the invention.

[0043] In particular, for steel slabs as alternatives or supplements to reinforcing patches, the following steel alloys are selected, described for example as steel A, B, C, or D in the table described below. The other slab of each of the two slabs can be made of the same steel, but can also be formed from one of the non-hardening steels E or F. Alloy element data are in parts by weight (%), with the balance being iron and impurities related to smelting.

[0044]

[0045] For all steels, a pre-coating of metal to prevent corrosion and oxidation can be applied before hot forming, especially AlSi alloys or Zn alloys or combinations thereof in multiple layers.

[0046] Figure 1 a and Figure 1 b illustrates the use of a reinforcing member according to the invention in motor vehicle component 1, in the form of a door ring 2 or a combination of pillars A and B 2, 3 together with a door sill 5. The door ring 2 can also be referred to as a door handle.

[0047] Figure 1 b shows a cross-sectional view according to section line AA. It can be seen that the area of ​​pillar A2 is formed as a closed hollow profile in cross-section by two abutting cap-shaped or C-shaped profiles. Here, the inner shell 6 is constructed as a motor vehicle component 1 according to the invention and coupled to the outer shell 7 via flanges 8. For this purpose, the inner shell 6 is constructed from an unformed steel sheet 9 and additionally has reinforcing patches 10, thus forming a double-layer structure 11 in this area. Therefore, an opening 14 is generally formed, which passes through the double-layer structure 11. For this purpose, a smaller opening 14 and a larger opening 14 relative to this smaller opening are constructed.

[0048] Figure 2 a to Figure 2 d illustrates the method flow according to the present invention. First, according to Figure 2 a provides reinforcement patch 10 and steel slab 9.

[0049] according to Figure 2 b, These two layers form a double-layer structure 11 and are coupled to each other. For this purpose, spot welding 12 can be used, for example.

[0050] according to Figure 2c. Pressing is performed from the surface of the opening 11 to be manufactured. Here, the pressed portion has a larger geometric extension or dimension than the later geometry of the opening. If, for example, a circular opening is constructed, the diameter D15 of the pressed portion 15 is larger than the diameter D14 of the opening 14. Here, the pressed portion can be implemented across the entire surface in the region of the pressed portion. However, the pressed portion 15 can also be wrapped only around the edge region. For example, the pressed portion 15 can be constructed as a circle in the case of the opening 14 to be manufactured as a circle, which is fully pressed and thus retracted relative to the surface 13. However, the pressed portion 15 can also be constructed simply as an annular shape, as shown here. The pressed portion 15 can be manufactured on a preform material. However, it is particularly preferred that the pressed portion 15 is made in the hot tool itself. Here, for example, a tool protrusion can be present to manufacture the pressed portion 15 in a thermoforming process. Then, a cutting or piercing tool enters from the opposite side of the pressed portion 15 and cuts out the opening 14.

[0051] In the context of this invention, the pressing portion 15 can also be constructed on both sides, i.e., on the surface 18 as referenced. Figure 2 c is constructed on the outer surface 13 of the steel slab 9 and on the outer surface 18 of the reinforcing patch 10, however this is in Figure 2 No further explanation is provided in section c.

[0052] according to Figure 2 d. On the completed motor vehicle component, the pressed portion 15 is then retracted relative to the surface 18, either relative to the surface or the opening in the surrounding edge region 14. The pressed portion 15 preferably extends radially around the surface by more than 0.5 mm in the radial direction R. The pressed portion 15 is retracted by 4% to 20% relative to the surface 13, relative to the wall thickness 17 of the steel slab 9 here.

[0053] For the sake of simplicity, the cutting punches and cutting waste, especially those used to create openings, are not shown in detail.

Claims

1. A motor vehicle component (1) manufactured from a hardenable steel slab (9) by thermoforming and pressure hardening, wherein, The motor vehicle component (1) has a reinforcing patch (10) that at least partially forms a double-layer structure (11) with the steel sheet (9). The motor vehicle component (1) has a continuous opening (14) in the area of ​​the reinforcing patch (10) by thermal cutting, thereby forming an opening (14) in the reinforcing patch (10) and an opening (14) in the steel sheet (9), wherein the edge region (16) surrounding the opening (14) is retracted and pressed on the steel sheet (9) or the reinforcing patch (10) relative to another surface (15).

2. The motor vehicle component (1) according to claim 1, characterized in that, The retracted pressing portion retracts by 4% to 40%, preferably 8% to 35%, especially 12% to 30% relative to the other surface (15) with respect to the wall thickness (17) of the steel slab (9) or reinforcing patch (10) having the pressing portion.

3. The motor vehicle component (1) according to any one of claims 1 or 2, characterized in that, The pressing part (15) extends radially around the opening (14) in the transverse direction by at least 0.5 mm, preferably more than 1 mm.

4. The motor vehicle component (1) according to any one of the preceding claims, characterized in that, The opening (14) has burrs at the edge of the hole after pressure hardening, and the length of the burrs is less than 0.3 mm, especially less than 0.2 mm.

5. The motor vehicle component (1) according to any one of the preceding claims, characterized in that, The wall of the opening (14) has a smooth cut portion of more than 25%, especially more than 40%.

6. The motor vehicle component (1) according to any one of the preceding claims, characterized in that, The flange created during thermal cutting extends into the wall of another component on the back side of the component with the embossed portion.

7. The motor vehicle component (1) according to any one of the preceding claims, characterized in that, A punch nut is inserted into the opening (14), wherein the punch nut itself is used to thermally cut the opening (14).

8. A method for manufacturing a motor vehicle component (1) having the features of claim 1, characterized in that... The following are the steps: - Provide steel slabs (9) and reinforcing patches (10), wherein at least one is made of a hardenable steel alloy. - The two components are coupled in such a way that the steel slab (9) and the reinforcing patch (10) form a double-layer structure (11). -Heat to a temperature above Ac3, wherein the pressing section (15) is introduced after heating, during thermoforming, or immediately after thermoforming. - Thermoforming, in which a cutting operation is performed during or after thermoforming. - Thermal cutting, wherein the cutting tool cuts on the back of the pressing part (15) and ejects the cut material on the side of the pressing part (15). -The motor vehicle component (1) thus formed is subjected to pressure hardening.

9. The method for manufacturing motor vehicle component (1) according to claim 8, characterized in that, Cutting should be performed at temperatures between 500°C and 770°C, especially between 600°C and 730°C.

10. The method for manufacturing a motor vehicle component (1) according to claim 8 or 9, characterized in that, The pressing part (15) is formed in a planar shape or in a ring shape.

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