Hole flanging method for improving flanging performance of inner edge of plate, pre-forming device and plate-shaped structural part

Abstract

The invention discloses a hole flanging method for improving the flanging performance of the inner edge of a plate, a pre-forming device and a plate-shaped structural part. The plate-shaped structural part comprises a base plate and a flanging hole formed in the base plate. The flanged hole is obtained by punching, pre-forming, re-punching and flanging the base plate, and the pre-forming process is to perform pre-forming processing on the punched plate by using a pressing core and a male die of a pre-forming device; the flanged hole of the plate-shaped structural part is free of cracking defects, and the strain value of the end of the flanged hole is smaller than or equal to 50%. The method can adapt to the forming characteristics of different materials, the risk that the inner edge of the plate-shaped structural part is turned and cracked due to hole flanging forming is reduced, and the hole expanding performance of the materials is improved to the maximum extent.

Description

Technical Field

[0001] This invention relates to the field of cold forming technology of sheet metal, and more specifically, to a method for flanging, a preforming device, and a sheet-like structural component for improving the flanging performance of the inner edge of sheet metal. Background Technology

[0002] In recent years, automotive chassis suspensions have been developing towards modularization and lightweighting. For example, Volkswagen proposed the MQB platform, and Toyota proposed the TNGA platform, further improving the commonality of key components on the basis of existing chassis platforms, moving from "platformization" to "modularization." Lightweighting is a significant development trend in chassis suspensions. BMW, Volkswagen, Ford, and Dongfeng Peugeot-Citroën have already achieved mass production application of 800MPa-level ultra-high-strength steel in their main models, while also proposing development requirements for 1000MPa-level steel. Although Toyota, Nissan, and GM's mass production applications are mainly below 600MPa levels, they are already conducting evaluations for 800MPa and 1000MPa levels. Automotive chassis control arms and triangle arms, due to their positioning and installation requirements, have a certain depth of borehole characteristics. This characteristic also poses a bottleneck problem in the manufacturing process of high-strength control arms and triangle arms.

[0003] Flanging refers to a stamping process that uses a die to turn the edge of a hole on a sheet metal into a flange (vertical straight edge). There are two existing types of flanging methods: one is a two-stage flanging process, where a small hole is pre-punched using a pre-punching die, and then the hole is turned using a flanging die (e.g.,...). Figure 1 , Figure 2 (As shown); another type is one-time flanging by directly breaking through the sheet metal. The former method involves pre-punching a small hole in the sheet metal and then flanging it at the next workstation. This is the most common process, but the flange height produced by this method is limited because pre-punching removes some material, reducing the material available for flanging and thus affecting the flange height. The second method, direct one-time flanging, involves directly tearing the sheet metal, resulting in a high, uneven flange with very sharp edges that can easily injure people during use and handling. Therefore, it is rarely used in industrial production.

[0004] In the prior art, Chinese patent application number 201811061089.7 proposes a method for turning holes in automotive parts. This method includes the following steps in sequence: making a raised bump, making a raised platform, pre-punching, turning the hole, reverse-drilling the turned hole end face, and hole inspection. This technology focuses on the fact that the processes of making a raised bump, making a raised platform, pre-punching, turning the hole, and reverse-drilling the turned hole end face are all performed on one device, reducing the handling process and simplifying the entire process. Moreover, the reverse-drilling of the turned hole end face process can tighten the vertical edge of the turned hole, increase the strength of the vertical edge, and remove the reverse material barbs. However, this technology does not mention how to improve the inner edge processing (i.e., turning hole) performance of the material.

[0005] For example, Chinese patent application No. 201510167803.0 proposes an integrated progressive forming and flanging tool and flanging process for hole opening and enlarging. This method completes the two-step process of cutting the hole and forming the hole without changing the tool by installing the cutting milling cutter on the flanging surface tool head. This reduces the number of tools and tool changing steps required in traditional progressive forming, improves processing efficiency, and can form flanged parts with less thinning and uniform thickness distribution.

[0006] The existing hole-expanding test methods all achieve the inner edge processing of materials (i.e., hole-flipping) by pre-forming bosses, then pre-punching, and then flipping holes, or achieve one-time forming of punching and flipping through integrated design to improve production efficiency. None of them involve how to improve the hole-expanding performance of materials. Summary of the Invention

[0007] In view of the deficiencies in the existing technology, the purpose of this invention is to provide a flanging method, preforming device and plate-shaped structural component that improves the flanging performance of the inner edge of the plate. It can be adapted to the forming characteristics of different materials, reduce the risk of inner edge cracking of the plate-shaped structural component due to flanging forming, and maximize the flanging performance of the material.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] The first aspect of the present invention provides a plate-shaped structural member with a flip hole, including a substrate and the flip hole formed thereon;

[0010] The flanging is obtained by punching, preforming, re-punching and flanging the substrate. The preforming process is to use the pressure core and punch of the preforming device to preform the punched plate.

[0011] The plate-shaped structural member has no cracking defects on the flanged holes, and the end strain value of the flanged holes is ≤50%.

[0012] Preferably, the substrate is made of CP800 material.

[0013] A second aspect of the present invention provides a preforming device for improving the inner edge flanging performance of sheet metal, comprising a die, a punch, a blank holder, and a blank holder ring;

[0014] The die cavity is provided with a recessed hole in the middle that matches the punch. The recessed hole matches the process hole of the plate-shaped structural part. The corners of the recessed hole that contact the plate are provided with die cavity rounded corners.

[0015] The corner where the punch contacts the sheet metal is provided with a punch radius;

[0016] The pressure core is disposed in the recess of the die; the pressure core is used to press the sheet metal above the punch to assist in the forming of the sheet metal;

[0017] The pressure ring has a through hole in the middle for the punch to pass through, and the pressure ring cooperates with the die to fix the sheet metal.

[0018] Preferably, the radius of the fillet of the die is 1.0 to 1.5 times the radius of the fillet of the hole on the plate-shaped structure.

[0019] Preferably, the radius of the fillet of the punch is 1mm to 5mm.

[0020] Preferably, both the punch and the pressure core are cylindrical, and the outer diameter of the pressure core is smaller than the outer diameter of the punch.

[0021] A third aspect of the present invention provides a method for improving the flanging performance of the inner edge of a sheet metal, comprising the following steps:

[0022] S1, punching process, punching holes in sheet metal to obtain punched sheet metal with punched holes;

[0023] S2, Preforming process: The perforated plate is preformed using a preforming device as described in the second aspect of the present invention to improve the inner edge flanging performance of the plate, thereby obtaining a preformed plate with punched holes.

[0024] S3, re-punching process, re-punching the punched holes of the preformed plate to obtain a re-punched plate with punched holes;

[0025] S4, Flanging process, involves flanging the inner edge of the re-punched plate to obtain a plate structure with flanged holes.

[0026] Preferably, in step S2, the blank holder and punch of the preforming device are used to preform the punched plate, and the pressure of the blank holder on the punched plate is 10 to 100 kN.

[0027] Preferably, in step S2:

[0028] The forming height H1 of the preformed plate is 30 to 80% of the hole height H2 of the plate structure obtained after hole turning;

[0029] The sidewall angle θ0 on both sides of the punching hole of the preformed plate is 30° to 80°, and the radius R of the die fillet on the outer side of the punching hole of the preformed plate is... d The radius R of the punch corner on the inner side of the punching hole of the preformed plate is 1.0 to 1.5 times the radius of the fillet of the hole. p The diameter is 1mm to 5mm.

[0030] The beneficial effects of this invention are:

[0031] 1. This invention can be adapted to the forming characteristics of different metal materials and maximizes the material's hole-making performance;

[0032] 2. Compared with traditional stamping processes (preforming, punching, and flanging), this invention can better utilize the material's ability to coordinate deformation. In addition, by removing the concentrated strain around the punched hole generated in the preforming process through re-punching, the inner edge flanging cracks generated in the subsequent flanging process can be greatly reduced, thus improving the flanging performance of the material. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the shape of a plate-shaped component in the first punching process of a traditional flanging process.

[0034] Figure 2 This is a schematic diagram of the shape of the plate-shaped component in the second flanging process of the traditional flanging method;

[0035] Figure 3 This is a schematic diagram of the preforming device for improving the inner edge flanging performance of sheet metal according to the present invention;

[0036] Figure 4 This is a schematic diagram of the shape of the punched plate in the punching process of the present invention;

[0037] Figure 5 This is a schematic diagram of the shape of the preformed plate in the preforming process of the present invention;

[0038] Figure 6 This is a schematic diagram of the shape of the re-punched plate in the re-punching process of the present invention;

[0039] Figure 7 This is a schematic diagram of the shape of the plate-shaped structural component in the hole-flipping process of the present invention;

[0040] Figure 8 This is a schematic diagram of the plate-shaped structural component of Embodiment 1 of the present invention.

[0041] In the diagram, 01 represents the sheet metal used in the traditional flanging process; 02 represents punching; 03 represents flanging; 1 represents a punched hole; 2 represents a punched hole; 3 represents a punched hole; 4 represents flanging; 10 represents a die; 20 represents a blank holder; 30 represents a blank holder ring; 40 represents a punch; a represents a punched sheet; b represents a pre-formed sheet; c represents a re-punched sheet; d represents a sheet-like structural component; φ1 represents the diameter of the punched hole in the punched sheet; φ2 represents the diameter of the punched hole in the pre-formed sheet; φ3 represents the diameter of the punched hole in the re-punched sheet; and φ4 represents the diameter of the flanged hole in the sheet-like structural component. Detailed Implementation

[0042] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0043] In view of the current situation where existing technologies cannot combine the performance characteristics of materials to improve the flanging performance of materials, the present invention provides a preforming device, flanging method and plate-shaped structural component for improving the flanging performance of the inner edge of a plate, which can be adapted to the forming characteristics of different materials and maximize the flanging performance of materials.

[0044] Combination Figure 7 As shown, the first aspect of the present invention provides a plate-shaped structural member d with a flip hole, including a substrate and a flip hole 4 formed thereon;

[0045] The flanging 4 is obtained by punching, preforming, re-punching and flanging the substrate. The preforming process is to use the pressure core 20 and punch 40 of the preforming device to preform the punched plate.

[0046] There are no cracks on the flanges of the plate-shaped structural components, and the strain value at the end of the flange is ≤50%.

[0047] The substrate is made of CP800.

[0048] Combination Figure 3 As shown, a second aspect of the present invention provides a preforming apparatus for improving the flanging performance of sheet metal inner edges. This preforming apparatus is used to prepare the aforementioned sheet-like structural component with flanged holes. The preforming apparatus includes a die 10, a punch 40, a pressure core 20, and a pressure ring 30. The die 10 has a recessed hole in the center that matches the punch 40, and the recessed hole matches the process hole of the sheet-like structural component. The corners of the recessed hole that contact the sheet metal are provided with die fillets. The corners of the punch 40 that contact the sheet metal are also provided with punch fillets. The pressure core 20 is disposed within the recessed hole of the die 10; the pressure core 20 is used to press down on the sheet metal above the punch 40, assisting in the forming of the sheet metal. The pressure ring 30 has a through hole in the center for the punch 40 to pass through, and the pressure ring 30 cooperates with the die 10 to fix the sheet metal.

[0049] Combination Figure 3As shown, the radius of the die fillet is 1.0 to 1.5 times the radius of the fillet of the hole on the plate-shaped structure; the radius of the punch fillet is 1 mm to 5 mm.

[0050] Combination Figure 3 As shown, the diameter of the concave hole of the die 10 is larger than the diameter of the through hole of the pressure ring 30; the punch 40 and the pressure core 20 are both cylindrical (e.g., cylindrical), and the outer diameter of the pressure core 20 is smaller than the outer diameter of the punch 40.

[0051] A third aspect of the present invention provides a method for improving the flanging performance of the inner edge of a sheet metal, specifically including the following steps:

[0052] S1, punching process, punching holes in sheet metal to obtain punched sheet metal with punched holes;

[0053] The punching process, as the first stamping process, involves punching holes in the sheet metal to obtain... Figure 4 The perforated plate a shown has a punched hole 1 with a diameter of φ1. Furthermore, the hole diameter φ1 of the perforated plate is larger than... Figure 1 The hole diameter of punch 02 in the traditional flanging process shown is small.

[0054] S2, Preforming process: The preforming device with the above-mentioned improved inner edge flanging performance of the sheet metal is used to preform the punched sheet b to obtain a preformed sheet b with punch holes 1.

[0055] Combination Figure 3 As shown, the preforming process, as the second stamping process, uses a cylindrical punch 40 and a blank holder 20 of the preforming device to preform the punched plate a. Thus, the following is obtained: Figure 5 The preformed plate b is shown with a punched hole 2 of diameter φ2. The forming height of the preformed plate b is H1, the sidewall angle is θ0, and the punch fillet radius is R. p The fillet radius of the die is R d .

[0056] In this preforming process, the preformed plate b has two areas of relatively large strain. The first is the strain around the punch hole 2. Before preforming, the periphery of the punch hole 1 is expanded, thus increasing the strain around the punch hole 2. This strain is called edge concentrated strain. The second is the strain in the contact area with the rounded corner of the punch and the area formed during the preforming process. Figure 5 The strain in the sidewall region shown is called the in-plane concentrated strain.

[0057] In this preforming process, the forming height H1 of the preformed plate b is greater than that of the final perforation (see...). Figure 7The forming height H1 of the preformed plate b is too low. If the forming height H1 of the preformed plate b is too low, the deformation amount of the subsequent hole turning will be large, which is prone to causing edge cracks in the later process. On the other hand, if the forming height H1 of the preformed plate b is too high, it is easy to cause edge cracks or in-plane necking due to excessive concentrated strain at the edge or in-plane. Therefore, the forming height H1 of the preformed plate b needs to be designed by comprehensively considering the final hole turning height H2 of the plate structure and the hole enlargement performance of the material; therefore, the forming height H1 of the preformed plate b is 30% to 80% of the hole turning height H2 of the plate structure obtained after hole turning.

[0058] Similarly, if the sidewall angle θ0 is too small, the deformation of the subsequent hole-making process will be large, which can easily cause cracks on the inner edge of the hole in later processes. Conversely, if the sidewall angle θ0 is too large, it can easily cause edge cracks or in-plane necking in the preformed plate b due to the aforementioned excessive concentrated strain at the edge or in-plane. Typically, the sidewall angle θ0 is designed to be in the range of 30° to 80°. When the material has good elongation properties and moderate hole-expanding properties, the sidewall angle θ0 is designed to be larger; conversely, when the material has moderate elongation properties and good hole-expanding properties, the sidewall angle θ0 is designed to be smaller.

[0059] Punch fillet radius R p The typical design radius for the die fillet is 1mm to 5mm, and the radius R is... d The design radius is generally 1.0 to 1.5 times the fillet radius of the final product (i.e., the sheet metal structural part d obtained after flanging); the fillet radius R of the punch is usually... p Die fillet radius R d The smaller the design, the smaller the concentrated strain at the edge of the preformed plate b, and the larger the concentrated strain in the plane.

[0060] Combination Figure 3 As shown, this preforming process employs a pressure core 20 to assist in the forming design. The pressure core 20 can adjust the concentrated strain at the edge and in-plane of the preformed plate b based on the material's performance characteristics. Once the preforming device is determined, without a pressure core, the concentrated strain at the edge and in-plane of the preformed plate b is almost impossible to change, making it unsuitable for the forming characteristics of different materials. With the pressure core 20, when the material has good elongation properties and moderate hole-expanding properties, the pressure of the pressure core can be increased, thus reducing the concentrated strain at the edge of the preformed plate b while increasing the concentrated strain in the in-plane; conversely, when the material has moderate elongation properties and good hole-expanding properties, the pressure of the pressure core can be decreased, thus increasing the concentrated strain at the edge of the preformed plate b while decreasing the concentrated strain in the in-plane. The preforming device can adapt to the forming characteristics of different materials and maximize the material's hole-expanding performance.

[0061] During the preforming process described above, the pressure exerted by the pressure core on the punched plate is 10-100 kN.

[0062] S3, re-punching process, re-punching the punching hole 2 of the preformed plate b to obtain a re-punched plate c with punching hole 3;

[0063] After the preforming process, the third stamping process, re-punching, is performed on the punched holes 2 of the preformed plate b to obtain the desired result. Figure 6 The plate c shown has a punched hole 3 with a diameter of φ3. This process is a fine punching process, and the diameter of φ3 is combined with the final hole height design of the plate structure. In addition, this punching process removes the concentrated strain around the punched hole produced in the pre-forming process, which can greatly reduce the inner edge cracks caused by the hole forming in the subsequent process.

[0064] S4, Flanging process, performs inner edge flanging forming on the re-punched plate c to obtain plate structural part d with flanged holes 4.

[0065] After re-punching, flanging, as the fourth punching process, involves flanging the inner edge of the re-punched plate c to achieve the desired result. Figure 7 The final stamped part with a hole diameter of φ4 and a hole height of H2 is shown, as well as the plate structure d with a hole 4.

[0066] This invention is adaptable to the forming characteristics of different materials and maximizes the material's turning performance. The method comprises four stamping processes: punching, preforming, re-punching, and turning. Compared to traditional stamping processes (preforming, punching, turning), this method better utilizes the material's coordinated deformation capabilities. Furthermore, the re-punching process removes the concentrated strain around the punched hole generated in the preforming process, significantly reducing inner edge cracks caused by the subsequent turning process and improving the material's turning performance. Additionally, the preforming device with a pressure core used in the preforming process is adaptable to the forming characteristics of different materials and maximizes the material's turning performance.

[0067] Example 1

[0068] This embodiment uses CP800 material with a thickness of 2.5 mm. The test material has a yield strength of 740 MPa, a tensile strength of 850 MPa, and an elongation of 12%. The test specimen is a circular plate with a diameter of 160 mm, and a center-flanged hole with an inner diameter of 70 mm, a bottom corner radius R3 = 3 mm, and a total flanging height H2 = 15 mm (e.g., a center-flanged hole). Figure 8 (As shown).

[0069] Combination Figure 3As shown, the pre-forming device for improving the inner edge flanging performance of sheet metal in this embodiment includes a die 10, a punch 40, a pressure core 20, and a pressure ring 30. The die 10 has a recessed hole in the center that matches the punch 20, and the recessed hole matches the process hole of the sheet metal component. The corners of the recessed hole that contact the sheet metal are provided with die fillets. The corners of the punch 40 that contact the sheet metal are also provided with punch fillets. The pressure core 20 is disposed within the recessed hole of the die; the pressure core 20 is used to press down on the sheet metal above the punch 20, assisting in the forming of the sheet metal. The pressure ring 30 has a through hole in the center for the punch 40 to pass through, and the pressure ring 30 cooperates with the die 10 to fix the sheet metal. The radius of the die fillet is twice the radius of the flanging hole on the sheet metal component, i.e., the die fillet radius is 6mm; the diameter of the punch 40 is 60mm, and the radius of the punch fillet on the punch 40 is 3mm. The diameter of the concave hole of die 10 is larger than the diameter of the through hole of pressure ring 30; the outer diameter of pressure core 20 is slightly smaller than the outer diameter of punch 40.

[0070] The preforming device and hole-flipping method of this invention are used for hole-flipping processing. Before the test, a circular grid is printed on the sample to facilitate subsequent strain measurement at the hole end. First, a 40mm diameter punch is formed through a punching process. Next, in the preforming process with a pressure core, a cylindrical punch with a diameter of 60mm and a punch radius of 3mm is used to complete the preforming process with a forming height H1 = 10mm. The pressure of the top pressure core is 20KN. After preforming, the diameter of the punched hole in the preformed plate is 46.5mm. Then, a re-punching process is performed to complete the punching of a 56.5mm diameter hole, resulting in a re-punched plate. Finally, a hole-flipping process is performed using a cylindrical punch with a diameter of 70mm and a punch radius of 3mm. The final hole-flipping height of the plate-shaped structure is H2 = 15mm. Using the above method, the part is well-formed, without cracking defects, and the strain value at the hole end is 31.5%.

[0071] Comparative Example 1

[0072] A traditional punching and flanging process was used, with the same materials and samples as in Scheme 1, to conduct flanging tests. A punching process was used to create a 48.5mm diameter hole. The flanging process employed a 70mm diameter cylindrical punch with a 3mm radius corner, resulting in a final flanging height of 15mm on the sample. The formed sample showed no cracking defects, but the strain value at the end of the circular hole was as high as 45.2%.

[0073] Comparative Example 2

[0074] Using the traditional flanging method (pre-forming + punching + flanging), and with the same materials and samples as in Scheme 1, a flanging processing test was conducted. See [link / reference]. Figure 1 , Figure 2As shown. The preforming process uses a cylindrical punch with a diameter of 60mm and a punch radius of 3mm to complete the preforming process with a forming height of 10mm. Then, a turning device is used to turn the punch. Finally, the sample has cracks in the contact area of ​​the top punch radius, making it impossible to carry out subsequent processing.

[0075] As can be seen from the above embodiments and comparative examples, the method of the present invention can better utilize the material's internal synergistic deformation capability, transforming the concentrated deformation at the end into synergistic deformation at the end and in the plane, effectively reducing the strain value at the end of the circular hole; in addition, the method of the present invention can be adapted to the forming characteristics of different materials, control the magnitude of in-plane strain and end strain, and maximize the material's hole-making performance.

[0076] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A plate-shaped structural component with a perforated hole, characterized in that: This includes the substrate and the vias formed thereon; The flanging is obtained by punching, preforming, re-punching and flanging the substrate. The preforming process is to use the pressure core and punch of the preforming device to preform the punched plate. The plate-shaped structural member has no cracking defects on the flanged holes, and the end strain value of the flanged holes is ≤50%.

2. The plate-shaped structural member with a perforated hole according to claim 1, characterized in that: The substrate is made of CP800 material.

3. A preforming device for improving the inner edge flanging performance of sheet metal, characterized in that, Includes die, punch, blank holder, and blank holder ring; The die cavity is provided with a recessed hole in the middle that matches the punch. The recessed hole matches the process hole of the plate-shaped structural part. The corners of the recessed hole that contact the plate are provided with die cavity rounded corners. The corner where the punch contacts the sheet metal is provided with a punch radius; The pressure core is disposed in the recess of the die; the pressure core is used to press the sheet metal above the punch to assist in the forming of the sheet metal; The pressure ring has a through hole in the middle for the punch to pass through, and the pressure ring cooperates with the die to fix the sheet metal.

4. The preforming device for improving the inner edge flanging performance of sheet metal according to claim 3, characterized in that: The radius of the fillet of the die cavity is 1.0 to 1.5 times the radius of the fillet of the hole on the plate-shaped structure.

5. The preforming device for improving the inner edge flanging performance of sheet metal according to claim 3, characterized in that: The radius of the fillet of the punch is 1mm to 5mm.

6. The preforming device for improving the inner edge flanging performance of sheet metal according to claim 3, characterized in that: Both the punch and the blank holder are cylindrical, and the outer diameter of the blank holder is smaller than the outer diameter of the punch.

7. A method for improving the flanging performance of the inner edge of a sheet metal, characterized in that, Includes the following steps: S1, punching process, punching holes in sheet metal to obtain punched sheet metal with punched holes; S2, Preforming process: The preforming device for improving the inner edge flanging performance of the sheet metal as described in any one of claims 3 to 6 is used to preform the punched sheet metal to obtain a preformed sheet metal with punching holes. S3, re-punching process, re-punching the punched holes of the preformed plate to obtain a re-punched plate with punched holes; S4, Flanging process, involves flanging the inner edge of the re-punched plate to obtain a plate structure with flanged holes.

8. The method for improving the flanging performance of the inner edge of a sheet metal according to claim 7, characterized in that, In step S2, the blank holder and punch of the preforming device are used to preform the punched plate. The pressure of the blank holder on the punched plate is 10 to 100 kN.

9. The method for improving the inner edge flanging performance of a sheet metal according to claim 7, characterized in that, In step S2: The forming height H1 of the preformed plate is 30 to 80% of the hole height H2 of the plate structure obtained after hole turning; The sidewall angle θ0 on both sides of the punching hole of the preformed plate is 30° to 80°, and the radius R of the die fillet on the outer side of the punching hole of the preformed plate is... d The radius R of the punch corner on the inner side of the punching hole of the preformed plate is 1.0 to 1.5 times the radius of the fillet of the hole. p The diameter is 1mm to 5mm.

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