Method for producing press-hardened sheet metal component and sheet metal component having press-in element
By pre-drilling and pre-flanging in the plate components, inserting the press-in elements and then performing heat treatment to form a martensitic structure, the problem of unstable connection in ultra-high-strength steel plate components is solved, efficient and low-cost press-in element connection is achieved, and the stability and safety of the connection are improved.
Patent Information
- Application Number
- CN202480012347.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-03-09
- Filing Date
- 2024-02-09
- Publication Date
- 2025-09-26
AI Technical Summary
In the prior art, joining press-fit elements to press-hardened ultra-high-strength steel plate components results in unstable connections, warping, and geometric deviations, resulting in high connection costs and difficulty in achieving high dimensional accuracy.
By pre-drilling and pre-flanging in the unhardened sheet metal component, inserting the press-in element, heating it to the austenitizing temperature and cooling it to form a martensitic structure, combined with mold forming, a form-locking and force-locking connection between the press-in element and the sheet metal component is achieved, reducing the extrusion pressure and warping.
It achieves efficient connection of pressed-in components, reduces extrusion force requirements, improves connection stability and safety, reduces warping and oxide scale, reduces mold costs, and ensures high dimensional accuracy and safety.
Smart Images
Figure CN120712366A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for producing a press-hardened sheet metal component with a press-fit element having the features of independent claim 1 and to a sheet metal component with a press-fit element having the features of independent claim 8 . Background Art
[0002] In the automotive industry, press-hardened sheet metal components are particularly used in the passenger compartment to improve occupant safety. For example, press-hardened sheet metal components are used in A- and B-pillars or sills. Special joining and connection techniques are used to connect seats and seat belts to ensure and enhance passive safety. To achieve this, press-fit elements (such as rivet nuts and punch nuts) are introduced into the sheet metal components. To create a riveted connection, the sheet metal must be pre-perforated and, depending on the press-fit element, flanged. This is done during the forming steps of the sheet metal component, such as shearing or deep drawing. The press-fit elements are introduced immediately after direct or indirect press hardening. Due to warping and geometric deviations in the prepared holes (caused by the hardening process), high pressing forces are required to compensate for geometric fluctuations and press the press-fit elements into the hardened sheet metal components. Due to the high strength after press hardening, press-fit elements can only be introduced into the components using expensive special processes. The introduction of pressed-in and punched elements prior to press hardening causes warping and geometric deviations in the connecting element and the associated threads of the elements due to the hardening process.
[0003] However, the realization of press-fit connections into press-hardened components is becoming increasingly important, as lightweight construction continues to be a focus in vehicle body development due to the increase in electrification in the automotive industry, especially due to the requirements for driving range. In this regard, the development of ultra-high-strength steels (UHSS) has been further promoted. They have a boron content (for example 22MnB5), are produced by press-hardening methods and have a strength of up to 1900 MPa. Ultra-high-strength steels are absolutely necessary for the passenger cell, precisely in view of the passive safety and various crash scenarios in motor vehicles. Due to the increased requirements for threaded connections (watertightness and superelastic threaded connections), the introduction of conventional press-fit elements is only suitable to a limited extent or not at all. In addition, the introduction of press-fit elements into ultra-high-strength steel is also complex and cost-intensive. Summary of the Invention
[0004] The object of the present invention is therefore to at least partially overcome at least one of the above-mentioned disadvantages of connecting press-in elements to press-hardened sheet metal components. In particular, the object of the present invention is to provide a method for producing a press-hardened sheet metal component with a press-in element, which method simplifies the introduction of the press-in element, is cost-effective, and produces a high dimensional accuracy of the connection.
[0005] The above-mentioned object is achieved by a method for producing a press-hardened sheet metal component with a press-fit element having the features of independent claim 1, and by a sheet metal component with a press-fit element having the features of independent claim 8. Further features and details of the invention are derived from the dependent claims, the description, and the drawings. Features and details described in conjunction with the method according to the invention naturally also apply in conjunction with the sheet metal component according to the invention, and vice versa, such that the disclosures concerning the various aspects of the invention are always mutually referenced or can be mutually referenced.
[0006] According to the invention, a first aspect of the invention provides a method for producing a press-hardened sheet metal component having a press-fit element, the method comprising the following steps:
[0007] - placing an unhardened sheet metal component into a punch of a die, wherein the sheet metal component has a prepared opening;
[0008] - inserting the press-in element into the opening of the sheet metal component;
[0009] - pressing the press-in element into the opening of the sheet metal component by pressing the die of the die onto the punch of the die;
[0010] - heating the unhardened sheet metal component with the pressed-in pressing element to the austenitizing temperature by means of a furnace;
[0011] The heated sheet metal component with the pressed-in pressing element is cooled by means of a cooling die, so that at least the sheet metal component has a martensitic microstructure.
[0012] The sheet metal component is prepared in a previous step. The prepared opening can be pre-punched and / or pre-flanged. In this context, the die can also be understood as a punch. It is conceivable that the sheet metal component undergoes a deep-drawing process beforehand for the first forming step. The process steps of pre-punching or pre-flange can be easily integrated into the deep-drawing process without changing the cycle time. The hardness of the sheet metal component is formed by the phase transformation of the steel produced during the heat treatment. During heating to the austenitizing temperature, an austenitic structure is initially formed, which transforms into the desired martensitic structure upon cooling.
[0013] It is conceivable to press a plurality of press-in elements into the sheet metal component. By pressing the press-in elements before heat treatment (i.e., heating and cooling), the form-locking and force-locking connection between the press-in elements and the sheet metal component is improved. The resulting connection is dimensionally more stable and has reduced warping and less scale. At the same time, the heat treatment can reduce the stresses generated when pressing the press-in elements, which further increases the security of the connection and the sheet metal component itself. In addition, since the sheet metal component has not yet hardened, the connection can be established more efficiently and effectively. This reduces the extrusion force required to press in the press-in elements, making it possible to use other, and in particular smaller and more advantageous, dies. The reduced extrusion force therefore also acts directly on the punch and die of the die, as well as the required dies.
[0014] The material of the press-in element is preferably selected such that it does not undergo a phase change during heat treatment.
[0015] In a method for producing press-hardened sheet metal components, it can be advantageous to form the sheet metal component using a die, particularly a forming die, while the press-in element is being pressed in. This means that the sheet metal component is formed before heating. This is known as cold forming or indirect press hardening. This is particularly advantageous because the stresses generated in the sheet metal component during forming can be reduced by subsequent heating. This increases the safety of the sheet metal component. Furthermore, it is more efficient because forming and pressing occur simultaneously, assuming that only one punch and one die are required for the entire method. This is particularly cost-effective and time-efficient.
[0016] The present invention can provide for cooling a heated sheet metal component with an inserted press-in element using a cooling die with a free form or a contact form. If the cooling die has a contact form, the shape of the cooling die corresponds to the shape of the formed component or its desired final dimensions. This, on the other hand, can compensate for any resulting warping or undesirable dimensional changes. The advantage of a free form is that it has a wider range of applications and is independent of the shape of the sheet metal component.
[0017] Within the scope of this method, it can be provided that, after heating, the sheet metal component is formed using the forming punch and forming die of the cooling die. This method corresponds to hot forming and can also be referred to as direct press hardening. This reduces warping of the sheet metal component because the forming occurs during the cooling process. This allows the structural transformation of the sheet metal component to be influenced locally, for example, to accommodate different thicknesses or different requirements for the sheet metal component.
[0018] In the method for producing a press-hardened sheet metal component, it is also conceivable that the sheet metal component with the press-fit elements is heated in a furnace to an austenitizing temperature between 723° C. (in particular 860° C.) and 1536° C., preferably between 723° C. (in particular 860° C.) and 1200° C., further preferably between 723° C. (in particular 860° C.) and 1000° C. The furnace can be a roller-hearth furnace or a multi-chamber furnace or a hot air preheating device. The temperature and holding time for austenitizing the sheet metal component vary depending on the sheet metal thickness, alloy, sheet metal surface and coating of the respective sheet metal component. In this case, the temperature can be adapted to the composition of the steel of the sheet metal component and / or the desired morphology of the austenitic structure for the transformation into a martensitic structure in the sheet metal component.
[0019]
[0020] In the method, it is also conceivable to heat the sheet metal component with the pressed-in elements in a furnace stepwise or continuously to the austenitizing temperature.
[0021] Stepwise heating is understood to mean first rapidly increasing the temperature by 100 K, 200 K, 300 K, or 500 K and then holding it for a specific time, for example 2 minutes, 5 minutes, 10 minutes, or 20 minutes, until the final temperature is reached. This ensures uniform heating of the sheet metal component.
[0022] Continuous heating is understood to mean a specific increase in temperature over a specific time without additionally maintaining the temperature at a certain level for a specific time.
[0023] The heating method depends on the type of furnace and the size and shape of the sheet metal component and can be selected accordingly. A mixture of stepwise and continuous heating is also possible. For example, to uniformly heat the component, an austenitizing temperature of approximately 860°C is exceeded and held for between 3 and 4 minutes. Roller-hearth furnaces with temperatures between 930°C and 950°C are typically used for this purpose.
[0024] Within the scope of the method for producing a press-hardened sheet metal component, provision can optionally be made for the heating to be carried out at a heating temperature of at least 4 K / min, preferably at least 4.5 K / min, further preferably at least 5 K / min.
[0025] This enables rapid heating to efficiently reach the desired austenitizing temperature without unnecessarily increasing the risk of warping or cracking.
[0026] Furthermore, according to a second aspect of the invention, the aforementioned object is achieved by a sheet metal component according to the invention having a press-in element, produced according to the aforementioned method.
[0027] This heating and subsequent cooling can then achieve the desired strength of the press-hardened sheet metal component of between 1200 MPa and 2200 MPa, in particular between 1500 MPa and 2000 MPa.
[0028] The advantages described in conjunction with the method according to the first aspect of the invention also apply in conjunction with the sheet-metal component with the press-in element according to the second aspect of the invention.
[0029] Precisely in view of the passive safety in motor vehicles and the protection of high-voltage accumulators in various crash situations, extremely high-strength sheet metal components with press-fit elements are absolutely necessary. Here, the high-voltage accumulator is connected to the sheet metal component according to the invention via the press-fit connecting element.
[0030] Furthermore, within the scope of the invention, provision can be made for the sheet metal component to be produced from boron-manganese steel.
[0031] This ensures simple forming of the sheet metal component and simple insertion of the press-in element. Simultaneously, the heat treatment transforms the manganese-boron steel into an ultra-high-strength steel. This increases safety in motor vehicle applications and, consequently, the safety of the connection to another component using the press-in element.
[0032] In connection with the invention, it is conceivable that the sheet metal component has an aluminum-silicon coating or a zinc coating.
[0033] Both the aluminum-silicon coating and the zinc coating have a favorable effect on the hardness of the sheet metal component. The increased hardness increases the security of the sheet metal component and thus also the security of the connection to another component by means of the press-fit element.
[0034] Furthermore, for sheet metal components, it can be provided that the press-in element is a connecting element for connecting components, in particular a nut, such as a rivet nut or a punch nut, or a screw, such as a press-in screw or a rivet screw, or a bushing. The press-in element is preferably made of non-hardenable steel so that no phase changes occur in the press-in element during heat treatment of the sheet metal component having the press-in element.
[0035] The press-in element is used to join or connect to another component, for example, another sheet metal component. The connection can be produced using a self-tapping screw. It is also conceivable for the press-in element to be a bushing that can receive a corresponding element or can be received by means of a corresponding element, for example, in the sense of a clip connection. It is also conceivable for the bushing to serve as a spacer.
[0036] Furthermore, it may be provided that the sheet metal component is made of an alloy which, after heating and cooling, has a strength of between 1200 MPa and 2200 MPa, in particular between 1500 MPa and 2000 MPa. These strength values are particularly advantageous for increasing the safety of the sheet metal component, in particular when it is used in the automotive industry. BRIEF DESCRIPTION OF THE DRAWINGS
[0037] Further advantages, features, and details of the present invention are apparent from the following description, in which several exemplary embodiments of the present invention are described in detail with reference to the accompanying drawings. The features mentioned in the claims and the description may be essential to the present invention individually or in any combination. The present invention is illustrated in the following figures:
[0038] Figure 1 Schematic diagram showing the first and second steps of an indirect method for producing a press-hardened sheet metal component having a press-fit element;
[0039] Figure 2 Schematic diagram showing the third step of the indirect method for producing a press-hardened sheet metal component having a press-fit element;
[0040] Figure 3 Schematic diagram showing the fourth step of the indirect method for producing a press-hardened sheet metal component having a press-fit element;
[0041] Figure 4 Schematic diagram showing the fifth step of the indirect method for producing a press-hardened sheet metal component having a press-fit element;
[0042] Figure 5 Show according to Figures 1 to 4 Schematic diagram of a plate member manufactured by an indirect method;
[0043] Figure 6 Schematic diagram showing the first step of a direct method for producing a press-hardened sheet metal component with press-fit elements;
[0044] Figure 7 Schematic diagram showing the second step of the direct method for producing a press-hardened sheet metal component with press-fit elements;
[0045] Figure 8 Schematic diagram showing the third and fourth steps of the direct method for producing a press-hardened sheet metal component having a press-fit element;
[0046] Figure 9 Show according to Figures 6 to 8 A schematic diagram of a first embodiment of a plate member manufactured by a direct method;
[0047] Figure 10 Show according to Figures 6 to 8 Schematic diagram of a second embodiment of a sheet member manufactured by a direct method. DETAILED DESCRIPTION
[0048] Figures 1 to 4 or Figures 6 to 8 A method 100 for producing a press-hardened sheet metal component 10 with a press-fit element 11 is shown. Figures 1 to 4 The method 100 is an indirect method 100 for producing a press-hardened sheet metal component 10 having a press-fit element 11 and is based on Figures 6 to 8 The method 100 is a direct method 100 for producing a press-hardened sheet metal component with a press-fit element. The indirect method and the direct method 100 for producing a press-hardened sheet metal component 10 with a press-fit element 11 have the following steps:
[0049] - placing 110 the unhardened sheet metal component 10 into the punch 12 of the die 13, wherein the sheet metal component 10 has a pre-punched and pre-flanged opening 14, see Figure 1 or Figure 6 ;
[0050] - inserting 120 the press-in element 11 into the opening 14 of the sheet metal component 10 , see Figure 1 or Figure 6 ;
[0051] - Pressing 130 the press-in element 11 into the opening 14 of the sheet metal component 10 by pressing 140 the die 15 of the die 13 onto the punch 12 of the die 13 , see Figure 2 or Figure 6 ;
[0052] - Heating 150° of the unhardened sheet metal component 10 with the pressed-in pressing element 11 to the austenitizing temperature AT by means of a furnace 16 , see Figure 3 or Figure 7 ;
[0053] - Cooling 160 the heated sheet metal component 10 with the pressed-in pressing element 11 by means of the cooling die 17 so that at least the sheet metal component 10 has a martensitic microstructure, see Figure 4 or Figure 8 .
[0054] In the indirect method 100, the sheet metal component 10 is formed 170 by means of a tool 13, in particular a forming tool, during the pressing 130 of the press-in element 11, as in Figure 2 As shown in .
[0055] In the indirect method 100, the cooling 160 of the heated sheet metal component 10 with the pressed-in pressing element 11 can be carried out by means of a cooling mold 17 with a free form or by means of a cooling mold 17 with a contact form ( Figure 4 ).exist Figure 4 In this case, a cooling mold 17 with a contact shape is used. This reduces warping and dimensional changes during cooling 160.
[0056] In a direct method 100 for producing a press-hardened sheet metal component 10 with a press-fit element 11, as Figure 8 As shown, after heating 150 , the sheet metal component 10 is formed 170 by means of the forming punch 20 and the forming die 21 of the cooling tool 17 .
[0057] In the direct method 100 (see Figure 8 ) and in the indirect method 100 (see Figure 3 ), the sheet metal component 10 with the press-fit element 11 is heated in the furnace 16 by 150°C to an austenitizing temperature AT between 723°C and 1536°C, preferably between 723°C and 1200°C, more preferably between 723°C and 1000°C. Here, the sheet metal component 10 with the press-fit element 11 is heated in the furnace 16 stepwise or continuously by 150°C to the austenitizing temperature AT.
[0058] The heating 150 is carried out continuously at a heating temperature HZ of at least 4 K / min, for example Figure 3 middle.
[0059] exist Figure 5 According to the Figures 1 to 4 The plate member 10 is manufactured by the indirect method 100. Figure 9 According to the Figures 6 to 8 A direct method 100 for manufacturing a sheet member 10.
[0060] The choice of whether to produce the sheet-metal component 10 with the press-in element 11 by an indirect method or a direct method 100 is independent of the basic properties of the sheet-metal component 10 and the press-in element 11 to be pressed in.
[0061] The desired ultra-high strength properties of the press-hardened sheet metal component 10 with the press-fit elements 11 are achieved if the sheet metal component 10 is made of boron-manganese steel. After heat treatment, ie after heating and cooling, the sheet metal component 10 has a strength of 1800 MPa.
[0062] These properties can be additionally improved if the sheet metal component 10 has an aluminum silicon coating. It is also conceivable that the sheet metal component 10 has a zinc coating.
[0063] Not only Figure 5And in Figure 9 In the embodiment, the press-in element 11 is a connecting element 18, in particular a nut. Here, a thread can be introduced into the press-in element 11 by means of a self-tapping screw 22, so that another component 19 is connected to the press-hardened sheet metal component 10.
[0064] Here, the connecting element 18 can also be a bolt or a bushing, as in Figure 10 As shown in the second embodiment of the sheet metal component in FIG. Here, the connecting element 18 is designed as a press-in screw. Here, a thread is applied to the press-in component 11 using a nut 23, in particular a self-threading nut 23, in order to connect another component 19 to the press-hardened sheet metal component 10. This combination of connecting elements can be used not only for indirect methods but also for direct methods.
[0065] Reference Signs List
[0066] 10 Plate components
[0067] 11 Press-fit components
[0068] 12 punch
[0069] 13 mold
[0070] 14 Opening
[0071] 15 Die
[0072] 16 furnaces
[0073] 17 Cooling the mold
[0074] 18 Connecting elements
[0075] 19 components
[0076] 20 Forming punch
[0077] 21 Forming die
[0078] 22 screws
[0079] 100 methods
[0080] 110 put in
[0081] 120 Insert
[0082] 130 Press in
[0083] 140 Press
[0084] 150 Heating
[0085] 160 Cooling
[0086] 170 Molding
[0087] AT austenitizing temperature
[0088] HZ Heating temperature
Claims
1. A method (100) for producing a press-hardened sheet metal component (10) having a press-fit element (11), the method comprising the following steps: - placing (110) an unhardened sheet metal component (10) having a pre-punched and pre-flanged opening (14) into a punch (12) of a die (13); - inserting (120) the press-in element (11) into the opening (14) of the sheet material component (10); - pressing (130) the press-in element (11) into the opening (14) of the sheet metal component (10) by pressing (140) the die (15) of the die (13) onto the punch (12) of the die (13); - heating (150) the unhardened sheet metal component (10) with the pressed-in pressing element (11) to the austenitizing temperature (AT) by means of a furnace (16); The heated sheet metal component (10) with the pressed-in pressing element (11) is cooled (160) by means of a cooling die (17) so that at least the sheet metal component (10) has a martensitic microstructure.
2. The method (100) according to claim 1, characterized in that The sheet metal component (10) is formed (170) by means of the tool (13), in particular a forming tool, during the pressing (130) of the press-in element (11).
3. The method (100) according to at least one of the preceding claims 1 or 2, characterized in that A heated sheet metal component (10) with an inserted pressing element (11) is cooled (160) by means of a cooling die (17) having a free form or a contact form.
4. The method (100) according to claim 1, characterized in that After heating (150), the sheet metal component (10) is formed (170) by means of a forming punch (20) and a forming die (21) of the cooling tool (17).
5. The method (100) according to at least one of the preceding claims, characterized in that The sheet metal component (10) with the press-in element (11) is heated (150) in the furnace (16) to an austenitizing temperature (AT) between 723°C and 1536°C, preferably between 723°C and 1200°C, further preferably between 723°C and 1000°C.
6. The method (100) according to at least one of the preceding claims, characterized in that The sheet metal component (10) with the press-in element (11) is heated (150) stepwise or continuously to the austenitizing temperature (AT) in the furnace (16).
7. The method (100) according to at least one of the preceding claims, characterized in that The heating ( 150 ) is carried out at a heating temperature (Hz) of at least 4 K / min, preferably at least 4.5 K / min, further preferably at least 5 K / min.
8. A sheet-metal component (10) having a press-in element (11) produced according to the method (100) according to at least one of the preceding claims.
9. The sheet material component (10) according to claim 8, characterized in that The plate member (10) is made of boron manganese steel.
10. The sheet metal component (10) according to at least one of the preceding claims 8 or 9, characterized in that The plate member (10) has an aluminum silicon coating or a zinc coating.
11. The sheet metal component (10) according to at least one of the preceding claims 8 to 10, characterized in that The press-in element (11) is a connecting element (18), in particular a nut or a bolt or a bushing, for connecting a component (19).
12. The sheet metal component (10) according to at least one of the preceding claims 8 to 11, characterized in that The sheet metal component is produced from an alloy which, after heating and cooling, has a strength of between 1200 MPa and 2200 MPa, in particular between 1500 MPa and 2000 MPa.