Rear longitudinal beam hot forming process

Abstract

This invention relates to a thermoforming process for a rear longitudinal beam. This process designs the sidewall surface corresponding to the feature surface at the overlap of the automotive sheet metal rear longitudinal beam and sill beam as an arc shape. This effectively controls the material flow direction, reduces forming friction, and improves wrinkling and cracking phenomena caused by uneven material feeding at the overlap surface. Furthermore, it does not affect the feature surface shape of the rear longitudinal beam, thus achieving a significant improvement in the quality of the corresponding part. Without altering the feature surface shape of the rear longitudinal beam, the sheet metal thickness is reduced, meeting the requirements for automotive lightweighting.

Description

Technical Field

[0001] This invention relates to the field of automobile manufacturing technology, and in particular to a hot forming process for rear longitudinal beams. Background Technology

[0002] In typical designs, the rear longitudinal beams in the rear floor assembly are hot-stamped from 1.8mm thick 22MnB5 material with a tensile strength ≥500MPa. After hot stamping, the tensile strength of the parts reaches 1500MPa. With the same material thickness, hot-formed longitudinal beams significantly improve the strength of the rear floor assembly. However, increasing the material specifications leads to an increase in product net weight, compromising overall vehicle lightweighting and increasing fuel consumption. Therefore, research into the hot-forming process of 1.4mm thick thin-plate rear longitudinal beams is necessary.

[0003] Reducing the material thickness from 1.8mm to 1.4mm presents the following problems:

[0004] 1. With the material thickness reduced from 1.8mm to 1.4mm, the longitudinal beams of the thinner plate are more prone to cracking under the same thinning rate.

[0005] 2. In order to increase the enveloping space of passenger car tires and reduce the corner radius of the rear longitudinal beam, the corner radius R96mm is much smaller than the conventional rear longitudinal beam corner radius R120mm. When the part is formed, the smaller the corner radius, the less smooth the transition between the X and Y directions. The material flows to the R corner from multiple directions, causing material accumulation at the corner, which manifests as wrinkling and cracking in the part. Summary of the Invention

[0006] To address the above problems, this invention provides a hot forming process for rear longitudinal beams, which avoids cracking of the sidewalls of thin-plate rear longitudinal beam stamped and drawn parts without altering the characteristics of the parts.

[0007] The technical solution adopted in this invention is: a hot forming process for rear longitudinal beams, characterized by including the following steps:

[0008] S1. Prepare the rear longitudinal beam blank and reserve process holes at the installation through holes of the trailing arm;

[0009] S2. Prepare the rear longitudinal beam body, and create the process-shaped surface on the basis of the rear longitudinal beam body to form a shaped surface with a drawing process; process and manufacture the thermoforming mold surface according to the process-shaped surface; the lap surface of the sill beam at the rear of the rear longitudinal beam is an arc-shaped surface.

[0010] The sill beam overlap surface extends outward along the outer side of the rear longitudinal beam body to form an extension surface. The rear part of the rear longitudinal beam drawing has a first side wall surface, the angle between the first side wall surface and the extension surface is 120-130°, and a first rounded corner is provided between the first side wall surface and the extension surface. The first side wall surface and the second side wall surface are arranged parallel to each other, the second side wall surface is located on the outer side of the rear longitudinal beam body along the first side wall surface, and a second rounded corner is provided between the first side wall surface and the second side wall surface. The third side wall surface is along the rear side direction of the rear longitudinal beam body, and the angle between it and the first side wall surface is 25°. A third rounded corner is provided between the third side wall surface and the first side wall surface and the second side wall surface.

[0011] S3. After the rear longitudinal beam blank is heated, it is transferred to the thermoforming mold to complete the production of the drawn part;

[0012] S4. Laser cutting of drawn parts, followed by the fabrication of finished longitudinal beam parts.

[0013] Preferably, in step S2, the lap joint surface of the sill beam extends outward by 7mm along the outer side of the rear longitudinal beam body to form an extended surface.

[0014] Preferably, in step S2, the radius of the first fillet is 15mm.

[0015] Preferably, in step S2, the distance between the first sidewall and the second sidewall is 10mm.

[0016] Preferably, in step S2, the radius of the second fillet is 150-200 mm.

[0017] Preferably, in step S2, the radius of the third fillet is 20mm.

[0018] Preferably, step S3 involves heating the rear longitudinal beam blank to 950°C in a heating furnace, transferring the rear longitudinal beam blank to a thermoforming mold for forming, pressure holding, cooling, and removal of the part by the end-effector, thus completing the production of the drawn part.

[0019] Preferably, in step S1, the dimensions of the process hole are as follows: the farthest distance from the center of the circle in the X direction to the blank line is 370mm, the farthest distance from the center of the circle in the Y direction to the blank line is 135mm, the arc diameter is D85mm, the straight segment is obtained by rotating the Y axis clockwise by 40°, and the arc segment and the straight segment are connected by an arc with an arc radius of 25mm.

[0020] Preferably, the thickness of the rear longitudinal beam blank is 1.4 mm.

[0021] The beneficial effects achieved by this invention are as follows: designing the side wall process shaping surface corresponding to the feature surface at the overlap of the rear longitudinal beam and the sill beam of the automobile sheet metal into an arc shape can effectively control the material flow direction, reduce forming friction, improve the wrinkling and cracking phenomenon caused by uneven feeding at the overlap surface, and does not affect the feature surface shape of the rear longitudinal beam, thereby achieving a significant effect of improving the quality of the corresponding part; without changing the feature surface shape of the rear longitudinal beam, the sheet metal thickness is reduced, meeting the requirements of automobile lightweighting. Attached Figure Description

[0022] Figure 1 This is a structural schematic diagram of the rear longitudinal beam blank;

[0023] Figure 2 This is a structural schematic diagram of the process shaping surface of the rear longitudinal beam;

[0024] Figure 3 This is a magnified view of a portion of the curved corner of the surface in the craftsmanship design;

[0025] Figure 4 This is a structural schematic diagram of the rear longitudinal beam drawing section;

[0026] Figure 5 This is a structural schematic diagram of the finished rear longitudinal beam.

[0027] In the diagram: 1. Threshold beam overlap surface; 2. Extension surface; 3. First side wall surface; 4. Second side wall surface; 5. Third side wall surface; 6. First rounded corner; 7. Second rounded corner; 8. Third rounded corner; 9. Fourth rounded corner; 10. Process hole. Detailed Implementation

[0028] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] To achieve the vehicle's lightweight requirements, the thickness of the rear longitudinal beam in the rear floor assembly needs to be reduced from the original 1.8mm to 1.4mm. To meet the tensile strength requirements (above 1500MPa) and the tire's envelopment space, the corner radius of the rear longitudinal beam needs to be reduced to R96mm, significantly smaller than the conventional rear longitudinal beam corner radius of R120mm. During part forming, a smaller corner radius results in a less smooth transition between the X and Y directions, causing material to flow towards the corner from multiple directions, leading to material accumulation at the corner and manifesting as wrinkling and cracking in the part.

[0030] To solve the above problems, such as Figure 1-5As shown, the present invention provides a hot forming process for a rear longitudinal beam, comprising the following steps:

[0031] S1. Prepare the rear longitudinal beam blank (e.g.) Figure 1 A process hole 10 is reserved at the installation hole of the trailing arm; in addition to the positioning hole, a process hole 10 is added to the rear longitudinal beam blank. The requirements for the process hole 10 are: the farthest distance L2 from the center of the circle in the X direction to the blank line is 370mm, and the farthest distance L1 from the center of the circle in the Y direction to the blank line is 135mm. The process hole 10 is composed of an arc segment and a straight segment. Among them, the arc diameter D of the arc segment is 85mm, the straight segment is obtained by rotating the Y axis clockwise by 40°, and the arc transition between the arc segment and the straight segment has a radius of 25mm.

[0032] S2. Prepare the rear longitudinal beam body, and create the process-shaped surface (such as...) on the basis of the rear longitudinal beam body. Figure 2 This process forms a drawing surface; the drawing surface is then processed to create a thermoforming mold surface; combined with... Figure 3 As shown, the sill beam lap surface 1 at the rear of the rear longitudinal beam is an arc-shaped surface. The sill beam lap surface 1 extends outward by 7mm along the outer side of the rear longitudinal beam body to form an extension surface 2. The rear of the drawn part of the rear longitudinal beam is provided with a first side wall 3. The angle between the first side wall 3 and the extension surface 2 is 120-130°. A first rounded corner 6 is provided between the first side wall 3 and the extension surface 2. The radius of the rounded corner 6 is 15mm. The first side wall 3 and the second side wall 4 are arranged parallel to each other and are spaced 1m apart. 0mm, the second side wall 4 is located on the outside of the first side wall 2 along the rear longitudinal beam body, and the first side wall 3 and the second side wall 4 have a second rounded corner 7 with a radius of 150-200mm; the third side wall 5 is along the rear side of the rear longitudinal beam body and forms an angle of 25° with the first side wall 3, and the third side wall 5 is provided with a third rounded corner 8 with a radius of 20mm between the first side wall 3 and the second side wall 4.

[0033] S3. The rear longitudinal beam blank is heated to 950° in the heating furnace. The end effector transfers the blank to the thermoforming mold for forming, pressure holding, cooling, and the end effector removes the part to complete the production of the drawn part.

[0034] S4. Laser cutting of drawn parts, followed by the fabrication of finished longitudinal beam parts.

[0035] In this invention, a second rounded corner 7 is provided between the first sidewall surface 3 and the second sidewall surface 4. The first sidewall surface 3, the second sidewall surface 4, and the two rounded corners 7 together form a sidewall. The angle between this sidewall and the lap surface 1 of the sill beam is 120° to 130°, forming the entire sidewall structure of the process shaping surface. During material forming, this sidewall structure causes the sheet metal to be subjected to tensile stress along the direction of the first rounded corner 6, increasing the material flow friction and slowing down the flow of the sheet metal along the direction of the first rounded corner 6, thereby achieving the effect of slowing down the thinning. At the same time, process holes 10 are added to the rear longitudinal beam blank to supplement the material along the direction of the first rounded corner 9 during material forming, increasing the material flow of the sidewall and achieving the effect of slowing down the thinning.

[0036] It should be noted that the above description of the technical solutions is exemplary, and this specification may be embodied in different forms and should not be construed as limiting it to the technical solutions set forth herein. Rather, providing these descriptions will ensure that the disclosure of this invention is thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Furthermore, the technical solutions of this invention are defined only by the scope of the claims.

[0037] Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention should be considered within the protection scope of the present invention.

Claims

1. A thermoforming process for a rear longitudinal beam, wherein the rear longitudinal beam is the rear longitudinal beam in the rear floor assembly, and its corner radius is R96mm, characterized in that: Includes the following steps: S1. Prepare the rear longitudinal beam blank. The thickness of the rear longitudinal beam blank is 1.4mm. Reserve process holes at the through holes for the trailing arm installation. S2. Prepare the rear longitudinal beam body, and create a process-shaped surface on the basis of the rear longitudinal beam body to form a shaped surface with a drawing process; process and manufacture the thermoforming mold surface according to the process-shaped surface; the sill beam overlap surface at the rear of the rear longitudinal beam is an arc-shaped surface, and the sill beam overlap surface extends outward along the outer side of the rear longitudinal beam body to form an extension surface; the rear of the drawn part of the rear longitudinal beam is provided with a first side wall, the angle between the first side wall and the extension surface is 120~130°, and a first rounded corner is provided between the first side wall and the extension surface; the first side wall and the second side wall are arranged parallel to each other, the second side wall is located on the outer side of the rear longitudinal beam body along the first side wall, and a second rounded corner is provided between the first side wall and the second side wall; the third side wall is along the rear side direction of the rear longitudinal beam body, and the angle between it and the first side wall is 25°, and a third rounded corner is provided between the third side wall and the first side wall and the second side wall. The first sidewall, the second sidewall, and the second rounded corner together form a sidewall. The angle between this sidewall and the sill beam's overlapping surface is 120°~130°, constituting the entire sidewall structure of the process shaping surface. During material forming, this sidewall structure causes the sheet metal to be subjected to tensile stress along the direction of the first rounded corner, increasing the material flow friction and slowing down the flow of the sheet metal along the direction of the first rounded corner, thereby slowing down thinning. At the same time, the process hole replenishes material along the direction of the first rounded corner during material forming, increasing the flow of sidewall material and thus slowing down thinning. S3. After the rear longitudinal beam blank is heated, it is transferred to the thermoforming mold to complete the production of the drawn part; S4. Laser cutting of drawn parts, followed by the fabrication of finished longitudinal beam parts.

2. The hot forming process for the rear longitudinal beam according to claim 1, characterized in that: In step S2, the lap joint surface of the threshold beam extends outward by 7mm along the outer side of the rear longitudinal beam body to form an extended surface.

3. The hot forming process for the rear longitudinal beam according to claim 1, characterized in that: In step S2, the radius of the first fillet is 15mm.

4. The hot forming process for the rear longitudinal beam according to claim 1, characterized in that: In step S2, the distance between the first sidewall and the second sidewall is 10mm.

5. The hot forming process for the rear longitudinal beam according to claim 1, characterized in that: In step S2, the radius of the second fillet is 150~200mm.

6. The hot forming process for the rear longitudinal beam according to claim 1, characterized in that: In step S2, the radius of the third fillet is 20mm.

7. The hot forming process for the rear longitudinal beam according to claim 1, characterized in that: The specific steps of step S3 are as follows: the rear longitudinal beam blank is heated to 950° in the heating furnace, the end pick-up device transfers the rear longitudinal beam blank to the thermoforming mold for forming, pressure holding, cooling, and the end pick-up device removes the part to complete the production of the drawn part.

8. The hot forming process for the rear longitudinal beam according to claim 1, characterized in that: In step S1, the dimensions of the process hole are as follows: the farthest distance from the center of the circle in the X direction to the blank line is 370mm, the farthest distance from the center of the circle in the Y direction to the blank line is 135mm, the arc diameter is D85mm, the straight segment is obtained by rotating the Y axis clockwise by 40°, and the arc segment and the straight segment are connected by an arc with an arc radius of 25mm.

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