Method for producing a motor vehicle component

Abstract

The invention relates to a method for producing a motor vehicle component which is produced from a hardenable steel slab (9) by means of hot forming and press hardening, 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, the motor vehicle component (1) having an opening (12) in the region of the reinforcing patch (10), the reinforcing patch (10) and the steel sheet blank (9) are arranged such that an opening (12) is formed in the reinforcing patch (10) and an opening (12) is formed in the steel sheet blank (9), one of the two openings (14) is larger than the other, and the smaller opening (13) is opened during or after hot forming.

Description

Technical Field

[0001] This invention relates to a method for manufacturing motor vehicle components. Background Technology

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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.

[0008] According to DE 10 2011 105 514 A1, there is a type of motor vehicle component that is constructed entirely by pre-drilling.

[0009] An opening is cut from a sheet metal component using a laser beam, according to DE 10 2011 120 670 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 technology.

[0011] Motor vehicle components are manufactured from hardenable steel slabs through thermoforming and pressure hardening. The components have reinforcing patches that form at least partially a double-layer structure with the steel slab. Body components, such as vehicle pillars, are particularly suitable for manufacturing as motor vehicle components, especially A-pillars, B-pillars, or C-pillars. However, other motor vehicle components may also fall under the scope of this invention or be manufactured using the method according to the invention.

[0012] First, the steel slab is fitted with reinforcing patches. These elements are coupled to each other. This coupling can be achieved, for example, by bonding or welding. The steel slab with reinforcing patches is placed above the austenitizing temperature and then hot-formed and pressure-hardened. In the context of this invention, it is primarily described that the steel slab is made of a hardenable steel alloy. Preferably, the patch or the patch blank is also made of a hardenable steel alloy. However, the patch blank may be made of a non-hardenable steel alloy. It is also conceivable that only the patch blank is made of a hardenable steel alloy, while the actual steel slab of the vehicle component is made of a non-hardenable steel alloy.

[0013] To allow cutting or perforation in the internal region while hot according to the invention, the following solution is proposed. The vehicle component has an opening in the region of the reinforcing patch. The opening itself completely penetrates the vehicle component, thus completely penetrating the region of the steel slab and the region of the reinforcing patch in cross-section. Therefore, the opening completely penetrates or is completely cut off from the wall thickness. Thus, the opening in the region of the steel slab and the opening in the reinforcing patch are visible. The two openings are constructed substantially aligned with each other. It is now specified according to the invention that one of the two openings, either the opening in the steel slab or the opening in the reinforcing patch, is larger than the second opening. The larger opening (hereinafter also referred to as a pre-hole) has previously been opened into the corresponding component according to the invention, thus being opened into the steel slab or the reinforcing patch in the cold and relatively soft initial state of the steel material.

[0014] Then, according to the invention, a second opening is created using a thermal cutting process, thus creating an opening with a smaller geometrical elongation. Here, the cutting temperature is particularly important, preferably between 500°C and 800°C, and very particularly preferably between 600°C and 730°C. Excessively high cutting temperatures result in an undefined cut edge structure and thus lead to higher burr formation. However, especially due to the double-layer structure, the steel slab and the reinforcing patch are in close contact with each other, and due to the larger heat capacity of the double-layer structure, the temperature in this area is higher or lasts longer.

[0015] However, preferably, the perforation of the corresponding steel alloy is opened at least when the temperature of the martensitic steel is above 450°C.

[0016] Particularly preferably, the opening itself is circular in its cross-section. Therefore, according to the invention, the cutting is implemented as a perforation in the internal region. However, other cross-sectional geometries of the opening are also possible. Thus, the opening can be constructed as circular, but it can also be constructed as polygonal or elliptical.

[0017] Furthermore, it has proven advantageous that the smaller opening is at least 5% smaller than the larger opening. In particular, the smaller opening is 6% to 20% smaller than the larger opening. However, the smaller opening should not be more than 50% smaller than the larger opening.

[0018] While maintaining the above parameters, it is feasible, particularly within the scope of the invention, to perform almost burr-free edge cutting in the opening created by thermal cutting. However, burrs are particularly characterized by a length of less than 0.3 mm, especially less than 0.2 mm.

[0019] A burr can also be formed from a smaller diameter hole, and then extended into a larger hole. Preferably, the burr then terminates as flush as possible on the opposite side of the larger hole. Thus, the burr protrudes relative to the blank with the smaller hole, but does not protrude outward beyond the blank with the larger hole. This creates an additional form fit. The burr in this case can also be referred to as a curl.

[0020] It is also feasible to create a smooth cut portion of more than 30%, especially more than 40%, and particularly preferably about 50% in the area of ​​the wall of the opening.

[0021] Furthermore, it has proven preferable, in the sense of the present invention, that the smaller opening has a flange that at least partially extends into the larger opening. Here, the flange can be formed directly during piercing or punching, wherein the flange is formed before the end of pressure hardening. Alternatively, piercing can be performed first, followed by flange stretching.

[0022] Furthermore, it has proven advantageous to directly cut a self-punching connecting element in a smaller opening, which in particular partially closes the smaller opening. A punched nut is particularly preferred here. Furthermore, it is particularly preferred that the self-punching connecting element, especially the punched nut, can then at least partially extend into a larger opening.

[0023] Motor vehicle components are manufactured using the method according to the present invention, which has the following characteristics:

[0024] - Provides hardenable steel slabs and reinforcing patches, with a larger opening in one of these two components.

[0025] - The two components are coupled in such a way that the steel slab and the reinforcing patch form a double-layer structure.

[0026] -Heat to above Ac3 temperature.

[0027] - A smaller opening is thermally cut, with one cutting tool passing through the larger opening to make a cut.

[0028] - Thermoforming, in which a cutting operation is performed during or after thermoforming.

[0029] - Pressure harden the formed motor vehicle components.

[0030] Therefore, the individual components are provided first. This consists of a steel slab made of a hardenable steel alloy and reinforcing patches. These two components are coupled, which is specifically manufactured by welding. The steel slab with the reinforcing patches is then heated to above the Ac3 temperature.

[0031] One of the two components already has an opening, which is a large opening. The heated preformed material, i.e., a steel blank with reinforcing patches, is then placed into a hot forming tool. In particular, these hot forming tools are those with combined cutting or punching tools. Specifically, this allows for a cutting process to be performed during or after hot forming. Preferably, this is done at a temperature of 500°C to 800°C. The heated steel blank is cooled by first contacting the tool of the hot forming tool. However, the cutting process is performed especially before the original pressure hardening, and therefore before liquid or water cooling of the hot forming tool. Therefore, it can be particularly ensured that the optimal cutting temperature is maintained between 550°C and 800°C. Subsequently, a pressure hardening process is performed, and the thus hardened component is preferably removed with a tensile strength exceeding 1000 MPa, particularly exceeding 1300 MPa, and particularly preferably exceeding 1500 MPa. Therefore, the opening created within the component has the highest precision, wherein the piercing tool or cutting blade undergoes only minimal wear due to the hot cutting process. Attached Figure Description

[0032] Other advantages, features, and characteristics of the invention are the subject of the following description. Preferred design variations are shown in the schematic diagrams. These drawings aid in a simple understanding of the invention. They illustrate:

[0033] Figure 1 The use of a reinforcing member according to the invention in a motor vehicle component is shown;

[0034] Figure 2 The first design variant of the invention is shown, which has pre-drilled holes in a thin slab, is formed into a motor vehicle component, and has perforated reinforcing patches;

[0035] Figure 3 A second embodiment of the invention is shown, wherein the reinforcing patch is pre-perforated and the formed steel slab is perforated.

[0036] Figure 4 This illustrates a third design variation of the invention;

[0037] Figure 5 Another design variation of the present invention with the introduction of a punched nut is shown.

[0038] List of reference numerals in the attached diagram:

[0039] 1. Motor vehicle components; 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. Opening; 13. Smaller opening; 14. Larger opening; 15. Spot weld; 16. Flange; 17. Punch-cut nut. Detailed Implementation

[0040] In the accompanying drawings, the same reference numerals are used for the same and similar components, even if repeated descriptions or arrangements are omitted for simplicity. The embodiments described above and below can be combined with each other arbitrarily within the scope of the invention without departing from it.

[0041] In particular, for steel slabs, alternatives or supplements to reinforcing patches are selected from the following steel alloys, which are described, for example, as steels A, B, C, or D in the table described below. The other billet in each of the two billets 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.

[0042]

[0043] 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.

[0044] 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.

[0045] 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 12 is generally formed, which passes through the double-layer structure 11. A smaller opening 13 and a relatively larger opening 14 are constructed for this purpose.

[0046] Then Figure 2 a to Figure 2 The manufacturing method according to the invention is further described in section e. First, a steel slab 9 is prepared, and an opening 12 is made in the steel slab 9. This may involve, for example, pre-piercing in the steel slab 9. In this case, a larger opening 14 is made. For example, a circular cut may be involved, which then has a corresponding diameter. Then, according to... Figure 2 A reinforcing patch 10 is placed and coupled to the steel slab 9, for example, by spot welding 15. According to Figure 2 d, and then a thermoforming process is performed, thus creating the shape. For simplicity, the area of ​​opening 12 is shown precisely during the shaping process. However, this area can also be formed three-dimensionally, for example, in a deep drawing process or other forming process. The reinforcing patch 10 and the steel blank 9 are also almost in contact with each other, which is shown here with the smallest visible gap for simplicity. Then, after thermoforming, a smaller opening 13 is made in the reinforcing patch 10. This is done using a piercing punch (not shown in detail), either through the larger opening 14, and thus from bottom to top with respect to the drawing plane. Alternatively, the piercing punch 15 can be brought onto the reinforcing patch 10 from the rear and brought down with respect to the drawing plane, so that the blanking material falls out through the larger opening 14. Immediately following is a pressure hardening process, and the component is thus thermoformed and pressure hardened, and has a particularly high tensile strength Rm.

[0047] Figure 3 a to Figure 3 e illustrates a similar process. However, here, the pre-piercing is not performed on the steel slab 9 but on the reinforcing patch 10. The larger opening 14 is therefore located within the reinforcing patch 9. Therefore, the smaller opening 13 is located according to… Figure 3 e is made in a formed steel slab 9 during or after the thermoforming process.

[0048] Figure 4 a to Figure 4 e also illustrates a similar process. Here, the reinforcing patch 10 is also pre-perforated. However, compared to... Figure 2 and Figure 3 The difference is that instead of creating a completely smaller opening 13, the smaller opening 13 is guided through the larger opening 14 according to the principle of flange stretching. Therefore, the composite structure of the reinforcing patch 10 and the formed steel slab 9 is further strengthened. Similarly, assembly can be simplified here, for example, by screwing threads into the flange 16 or threading cables through the flange 16.

[0049] Figure 5 a to Figure 5 e shows and Figure 4 A similar process is followed, except that a threaded flange 16 is not used here. A blanking member, in this case a blanking nut 17, is cut into the hot-formed steel slab 9. The blanking nut 17 can be secured by a form-fit connection from the blanking process. However, welding can also occur simultaneously.

[0050] Figure 4 and Figure 5 The implementation method can also change the position of the larger pre-piercing in the reinforced blank, so that the larger pre-piercing is like Figure 2 It is formed in the steel slab in that way.

Claims

1. A method for producing a motor vehicle component (1), characterized in that, The method comprises the following method steps: - providing a steel blank (9) and a reinforcement patch (10) which can be hardened, and opening a larger opening (14) in one of the two components, - coupling the two components such that the steel blank (9) and the reinforcement patch (10) at least partially form a double-layer structure (11), - heating to above the Ac3 temperature, - hot cutting of a smaller opening (13), wherein a cutting tool cuts through the larger opening (14), - hot forming, wherein the cutting operation is performed during or after the hot forming, - press-hardening of the thus formed motor vehicle component (1).

2. The method for producing a motor vehicle component (1) according to claim 1, characterized in that Cutting at a temperature of between 500°C and 800°C, in particular between 600°C and 730°C.

3. The method for producing a motor vehicle component (1) as claimed in claim 1 or 2, characterized in that The openings (12, 14) are configured circular in cross section.

4. The method for producing a motor vehicle component (1) according to any one of the preceding claims, characterized in that The larger opening (14) is opened in the steel blank (9) and the smaller opening (13) is opened in the reinforcement patch (10), or the larger opening (14) is opened in the reinforcement patch (10) and the smaller opening (13) is opened in the steel blank (9).

5. The method for producing a motor vehicle component (1) according to any one of the preceding claims, characterized in that The smaller opening (13) is at least 5% smaller than the larger opening (14), in particular the smaller opening (13) is 6% to 20% smaller than the larger opening (14).

6. The method for producing a motor vehicle component (1) according to any one of the preceding claims, characterized in that The hole edge of the smaller opening (13) has burrs after press-hardening, the length of which is less than 0.3 mm, in particular less than 0.2 mm.

7. The method for producing a motor vehicle component (1) according to any one of the preceding claims, characterized in that The wall of the smaller opening (13) has a smooth cutting portion of more than 25%, in particular more than 40%.

8. The method for producing a motor vehicle component (1) according to any one of the preceding claims, characterized in that The smaller opening (13) has a flange (16) which at least partially projects into the larger opening (14).

9. The method for producing a motor vehicle component (1) according to any one of the preceding claims, characterized in that The smaller opening (13) is at least partially closed by a self-piercing connecting element, in particular the smaller opening (13) itself is perforated and partially closed by a punched nut.

10. The method for producing a motor vehicle component (1) according to the preceding claim, characterized in that The self-piercing connecting element at least partially projects into the larger opening (14). The self-piercing connecting element at least partially projects into the larger opening (14).

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