Delayed-cracking-resistant ultrahigh-strength steel and variable-curvature automobile anti-collision beam

Abstract

An anti-delayed-cracking ultrahigh-strength steel and variable-curvature automobile anti-collision beam comprises a beam body and patch reinforcers, inner arc faces of transition sections at the two ends of the beam body are cut off through fillets, and the patch reinforcers are fixed to the cut-off positions of the fillets of the inner arc faces. The radian of the patch reinforcer is the same as that of the transition section on the cross beam main body, and the cross beam main body is U-shaped. The patch reinforcer is additionally arranged after the inner arc face of the transition section of the cross beam body is cut off, the machining difficulty of the variable-curvature small-radian transition section anti-collision beam is reduced, the material strength of the patch reinforcer is lower than that of the cross beam body, the delayed cracking risk of the anti-collision beam is effectively reduced, and the safety requirement of a whole vehicle is met.

Description

Technical Field

[0001] The present invention relates to an automobile anti-collision beam, in particular to an ultra-high-strength steel variable-curvature automobile anti-collision beam capable of resisting delayed cracking. Background Art

[0002] Currently, the trend toward electrification of automobiles is evident, creating a huge demand for lightweighting. Simultaneously, automotive crash safety regulations are becoming increasingly stringent. These dual requirements for lightweighting and safety are forcing the development of even lighter vehicle body components, reducing weight and improving safety.

[0003] The traditional anti-collision beam is a fixed-radian anti-collision beam, such as Figure 1 The arc R1 is large and the molding difficulty is moderate, so the risk of delayed cracking caused by internal stress after molding is low. However, this type of anti-collision beam is difficult to integrate with other vehicle components or the overall vehicle shape, resulting in a limited crossbeam length and difficulty in achieving anti-collision function at both ends, affecting the collision safety of the entire vehicle.

[0004] For automotive anti-collision beams, the greater the proportion of the beam to the vehicle's width, the better the overall vehicle safety. To meet extreme operating conditions such as small offset collisions, the length of the anti-collision beam has gradually increased, making it impossible to use the traditional fixed curvature design. Variable curvature is often required at both ends to avoid other components such as headlights and skin.

[0005] Existing variable curvature solutions present different challenges depending on the steel strength. For materials with a tensile strength below 1500MPa, due to process limitations, the curvature (R2) of the variable curvature section is large, resulting in a slow transition. This limits the length of the anti-collision beam. Furthermore, due to material strength limitations, improving anti-collision performance can only be achieved by increasing the cross-section or thickness, which negates the lightweight advantage.

[0006] The variable curvature anti-collision beam made of ultra-high strength steel above 1500MPa (see Figure 2 ) There are the following problems: First, due to the high-strength steel material and the small transition arc R2, the variable curvature processing is much more difficult, difficult to form, or there are many wrinkles after forming, which affects the matching of product parts; Second, due to the small transition arc R2, the internal stress of the product after processing is relatively large. In addition, the martensite content in ultra-high-strength steel is relatively high. This phase is prone to delayed cracking under greater stress, and delayed cracking may cause the product to crack after installation, greatly increasing the risk to automobile safety. Summary of the Invention

[0007] In order to overcome the drawbacks of the existing technology, the present invention provides an ultra-high-strength steel, variable-curvature automobile anti-collision beam that is resistant to delayed cracking. After the inner arc surface of the transition section of the main body of the beam is cut off, a patch reinforcement is added, which reduces the processing difficulty of the anti-collision beam with a small transition section of variable curvature. The strength of the material used for the patch reinforcement is lower than that of the main body of the beam, which effectively reduces the risk of delayed cracking of the anti-collision beam and meets the safety requirements of the entire vehicle.

[0008] The technical solution adopted by the present invention to solve its technical problem is: A delayed cracking-resistant ultra-high-strength steel, variable-curvature automobile anti-collision beam, comprising a crossbeam body and a patch reinforcement. The inner arc surface of the transition section at both ends of the crossbeam body is rounded off, and the patch reinforcement is fixed at the rounded cut-off portion of the inner arc surface. The curvature of the patch reinforcement is the same as that of the transition section on the crossbeam body, and the cross-section of the crossbeam body is a "concave" shape.

[0009] The above-mentioned ultra-high strength steel and variable curvature automobile anti-collision beam that resists delayed cracking has an inner arc surface cut off at the transition section of the beam body with a length equal to the length of the transition section or extending 5 to 100 mm on both sides of the transition section.

[0010] The above-mentioned ultra-high-strength steel and variable-curvature automobile anti-collision beam that is resistant to delayed cracking has a material strength of the patch reinforcement that is different from the material strength of the beam body. The material tensile strength of the patch reinforcement is 450~1200MPa, the material thickness is 1.2~3.5mm, and the length is extended by 20~200mm at both ends along the length direction of the inner arc surface cut-off section.

[0011] The above-mentioned ultra-high strength steel and variable curvature automobile anti-collision beam that is resistant to delayed cracking, the patch reinforcement is a "C"-shaped reinforcement plate, which is buckled to the inner arc surface of the cut transition section and welded to the beam body.

[0012] The above-mentioned ultra-high-strength steel and variable-curvature automobile anti-collision beam that is resistant to delayed cracking, the patch reinforcement includes a first reinforcing metal plate and a second reinforcing metal plate, both of which are arranged in a "C" shape, the first reinforcing metal plate is buckled to the depression in the middle of the "concave"-shaped crossbeam body, and the two adjacent side walls of the two cavities adjacent to the crossbeam body are welded and fixed, the second reinforcing metal plate is buckled to the inner arc surface of the crossbeam body, and the second reinforcing metal plate covers the first reinforcing metal plate.

[0013] The above-mentioned ultra-high-strength steel and variable-curvature automobile anti-collision beam that is resistant to delayed cracking, the patch reinforcement is configured to be tubular, including eight identical metal tubes, the metal tubes are fixed in pairs at the inner arc surface cut-out of the transition section of the beam body, and the two metal tubes located in the same cavity at one end of the beam body are welded and fixed, and the metal tube wall is welded or riveted to the cavity wall of the beam body.

[0014] The beneficial effects of the present invention are: The present invention rounds off the inner arc surface of the transition section of the ultra-high-strength steel variable-curvature anti-collision beam, and then fixes a patch reinforcement in the cut-off area, thereby reducing the process difficulty of the variable-curvature small-arc transition section anti-collision beam assembly; the material strength of the patch reinforcement is lower than the material strength of the crossbeam body, while ensuring that the overall strength of the anti-collision beam is not reduced or the reduction is not large, the anti-delayed cracking ability of the anti-collision beam is greatly improved, thereby improving the safety of the entire vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the structure of a conventional anti-collision beam with a specified curvature; Figure 2 This is a schematic diagram of the structure of a conventional ultra-high-strength steel variable curvature anti-collision beam; Figure 3 This is a schematic diagram of the overall structure of the anti-collision beam of Example 1; Figure 4 This is a schematic diagram of the local structure of the rounded corner cutout of the transition section of the anti-collision beam; Figure 5 This is a schematic diagram of the local structure of the welded patch reinforcement plate in the transition section of the anti-collision beam; Figure 6 This is a schematic diagram of the overall structure of the anti-collision beam of Example 2; Figure 7 This is a schematic diagram of the structure after the transition section is rounded off; Figure 8 Schematic diagram of the sectional direction structure of the resection position; Figure 9 This is a schematic diagram of the local structure after the first reinforcing metal plate is welded; Figure 10 This is a schematic diagram of the local structure after the second reinforcing metal plate is welded; Figure 11 This is a schematic diagram of the overall structure of the anti-collision beam of Example 3; Figure 12 This is a schematic diagram of the metal pipe installation process structure; Figure 13 This is a schematic diagram of the local structure of metal pipe welding; Figure 14 This is a schematic diagram of the local structure of the metal pipe riveting; Figure 15 This is a schematic diagram of the overall structure of the split anti-collision beam of Example 4; Figure 16 This is a schematic diagram of the decomposed structure of the split anti-collision beam; Figure 17 Schematic diagram of the local static pressure crushing structure of the anti-collision beam transition section; Figure 18 This is a schematic diagram of the CAE simulation beam structure with 50% crushing; Figure 19The force value-rigidity indenter displacement curve diagram in the CAE simulation analysis of each embodiment and a conventional anti-collision beam; Figure 20 This is the absorbed energy-rigid indenter displacement curve.

[0016] In the figure: 1. Main body of the crossbeam; 2. Patch reinforcement; 2-1. First reinforcing metal plate; 2-2. Second reinforcing metal plate; 2-3. Metal pipe; 3. Weld; 4. Car skin; 5. Cut-off fillet; 6. Riveted hole; 7. Middle section of the crossbeam; 8. Right section of the crossbeam; 9. Left section of the crossbeam; 10. Left end transition pipe; 11. Right end transition pipe. DETAILED DESCRIPTION

[0017] The main function of the transition section of the variable curvature anti-collision beam is to connect with the energy absorption box as an anti-collision beam assembly, to withstand the impact force in various collision conditions, and to absorb part of the collision energy. Ultra-high-strength steel (above 1500MPa level) anti-collision beams have a great risk of delayed cracking in the transition section due to the large stress in the transition section and the high material strength resulting in more processing defects. In response to this problem, the present invention proposes a method for improving the delayed cracking resistance of ultra-high-strength steel anti-collision beams, in which the inner arc surface of the transition section of the variable curvature anti-collision beam is first rounded, and then a patch reinforcement is added. The patch reinforcement is made of steel that is not sensitive to delayed cracking, and its tensile strength is less than the tensile strength of the beam body, thereby reducing the risk of delayed cracking of the anti-collision beam and ensuring that the anti-collision beam product meets the safety requirements of the entire vehicle. In the cutting direction, the cutting height is to at least remove all the rounded corners of the inner arc surface (see Figure 8 The transition arc length is generally 100-400mm. The resection should be at least the length of the resection, or an additional 5-100mm extension at each end. The material strength of the patch reinforcement is lower than that of the main beam. Steel insensitive to delayed cracking is used, with a tensile strength of 450-1200MPa. The thickness of the reinforcement plate is designed based on the material strength. The general principle is: high material strength corresponds to a thinner plate; low material strength corresponds to a thicker plate. The thickness of the patch reinforcement plate is 1.2-3.5mm. The length of the patch reinforcement extends 20-200mm at each end of the inner arc resection, completely covering the resection.

[0018] The main reason for delayed cracking in the transition area of ​​the anti-collision beam is the use of martensitic steel, which is a material that is extremely sensitive to delayed cracking. The transition area of ​​the anti-collision beam produces plastic deformation during the processing. The martensitic steel, which is sensitive to delayed cracking, plus the plastic deformation is the direct cause of delayed cracking in the transition area. In the present invention, a patch reinforcement plate is used to replace the martensitic material in the transition area. The material strength is between 450 and 1200 MPa, which directly replaces the martensitic steel in the transition area of ​​the anti-collision beam. It can not only ensure the overall impact resistance of the anti-collision beam, but also greatly improve the delayed cracking resistance of the transition section.

[0019] The present invention will be further described below with reference to the embodiments. Example 1

[0020] See Figure 3 The anti-collision beam of the automobile includes a beam body 1 and a patch reinforcement 2. The inner arc surface of the transition section of the beam body is cut off with a fillet 5 and a partial diagram is shown. Figure 4 Patch reinforcement 2 is provided as a "C" shaped reinforcement plate, which is buckled to the inner arc surface of the transition section of the cut, fully covering the cut, the patch reinforcement is welded to the beam body 1, see Figure 5 The welding position of the patch reinforcement plate and the beam body is as follows: the two sides of the patch reinforcement plate are welded to the front and rear side walls of the beam body, and the top horizontal plate of the patch reinforcement plate is welded to the inner arc surface of the beam body. The weld 3 is as follows Figure 5 As shown; the plate thickness of the beam body is 1.6mm, the material tensile strength is 1500MPa, the length of the transition section is 267mm, the cut-off length is 267mm, the plate thickness of the patch reinforcement is 1.4mm, the material tensile strength is 590MPa, and the length of the patch reinforcement is 373mm. Example 2

[0021] See Figures 6 to 10 The arc surface of the transition section of the beam body is rounded and cut off with the same cutting standard as in Example 1 (see Figure 7 and 8 ), and then fix the patch reinforcement. The patch reinforcement 2 includes a first reinforcement metal plate 2-1 and a second reinforcement metal plate 2-2. Both reinforcement metal plates are set in a "C" shape. The first reinforcement metal plate 2-1 is buckled to the depression in the middle of the "concave"-shaped crossbeam body, and is welded and fixed to the adjacent two side walls of the two cavities adjacent to the crossbeam body. The weld 3 is as shown Figure 9 Then the second reinforcing metal plate 2-2 is buckled to the inner arc surface of the beam body 1, and the second reinforcing metal plate 2-2 covers the first reinforcing metal plate 2-1 (as shown Figure 10 The crossbeam body has a plate thickness of 1.6 mm and a material tensile strength of 1500 MPa. The transition section is 267 mm long and has a cutout length of 282 mm. The first reinforcing metal plate has a thickness of 1.6 mm and a material tensile strength of 590 MPa. The first reinforcing metal plate is 268 mm long. The second reinforcing metal plate has a plate thickness of 1.4 mm and a material tensile strength of 590 MPa. The second reinforcing metal plate is 366 mm long.

[0022] Example 3 The standard for cutting the inner arc surface of the transition section of the beam body in this embodiment is the same as that of embodiment 1. The patch reinforcement is a metal tube 2-3 structure with a "mouth" shape, which matches the cavity size of the beam body. The metal tube can be inserted into the cavity of the beam body. Two metal tubes are fixed in one cavity of each transition section of the beam body. The two metal tubes are arranged side by side along the length of the beam body, and the butt ends of the two metal tubes are welded and fixed. The other ends of the two metal tubes are fixed to the beam body (welding or riveting to the side wall, such as Figure 13 and Figure 14 The specific installation process of the metal tube is as follows: first, place a metal tube into a cavity of the cut beam body, push it to one side of the cavity, then install the second metal tube. After the end faces of the two metal tubes are fitted together, pull the two metal tubes in opposite directions for a distance to the predetermined installation position and fix them to the beam body. Figure 12 As shown in the figure, the metal tubes are installed in the same manner in the two cavities at each end of the beam body. The beam body sheet metal is 1.6 mm thick, with a tensile strength of 1500 MPa. The transition section is 267 mm long, with a cutout length of 282 mm. The metal tubes are 1.6 mm thick, with a tensile strength of 590 MPa, and each tube is 183 mm long. Example 4

[0023] The anti-collision beam of this embodiment adopts a split structure, such as Figure 16 , including the middle section of the crossbeam 7, the right section of the crossbeam 8, the left section of the crossbeam 9, the left end transition pipe 10 and the right end transition pipe 11. The left end transition pipe and the right end transition pipe each include two metal pipes, which are arranged side by side at intervals and correspond to the two cavities in the middle section of the crossbeam. The two ends of the left end transition pipe are respectively welded to the middle section of the crossbeam and the left section of the crossbeam, and the two ends of the right end transition pipe are respectively welded to the middle section of the crossbeam and the right section of the crossbeam. Figure 15 The middle section 7, right section 8, and left section 9 of the crossbeam are made of the same metal sheet with the same cross-section, a thickness of 1.6mm, and a tensile strength of 1500MPa. The left and right transition pipes 10 and 11 are made of the same metal sheet with the same cross-section, both in the shape of a "mouth," with a thickness of 1.6mm, a tensile strength of 1180MPa, and a length of 360mm. For this type of anti-collision beam, the transition section's transition R angle can be even smaller, with an R < 900mm.

[0024] CAE simulation analysis was performed on the anti-collision beams obtained in the above embodiments 1 to 4, and the results were compared with those of conventional variable curvature anti-collision beams (such as Figure 2 ) for comparison, the thickness of the conventional variable curvature anti-collision beam is 1.6mm, and the tensile strength of the material is 1500MPa. Figure 19 and 20When the crossbeam reaches 50% crush, the corresponding displacement of the rigid indenter is 50mm. The critical crush stage occurs when the rigid indenter displacement is 30mm-50mm, during which the crossbeam primarily absorbs the collision energy.

[0025] Depend on Figure 19 As shown in Table 1, the four anti-collision beam structures of Examples 1 to 4 of the present invention exhibit comparable or higher force levels than conventional anti-collision beams during the critical crushing phase. Taking the average force values ​​during this critical crushing phase, the anti-collision beam structure of the present invention exhibits an average force value within the 30-50mm range that is no less than that of conventional anti-collision beams. See Table 1 for specific values.

[0026] Table 1 Force values ​​of each embodiment and conventional anti-collision beam in the key crushing area Example Average force within the 30~50mm crushing range / KN Original solution (conventional variable curvature anti-collision beam) 493.5 Example 1 493.5 Example 2 592.5 Example 3 927.5 Example 4 534.5 Depend on Figure 20 It can be seen that when the beam collapse reaches 50%, the energy absorbed by each scheme is as follows: Original solution (conventional variable curvature anti-collision beam): 16KJ; Solution 1 (Example 1): 14KJ, which is 87.5% of the conventional variable curvature anti-collision beam; Solution 2 (Example 2): 15KJ, which is 93.7% of the conventional variable curvature anti-collision beam; Solution 3 (Example 3): 22.5KJ, which is 140.6% of the conventional variable curvature anti-collision beam; Solution 4 (Example 4): 12.5KJ, which is 78.1% of the conventional variable curvature anti-collision beam; From the above analysis, it can be seen that the four structural forms described in the present invention can greatly improve the delayed cracking resistance of the beam while not significantly reducing the impact resistance of the beam in a collision and not causing the main function of the beam to be lost.

Claims

1. An ultra-high-strength steel, variable-curvature automobile anti-collision beam resistant to delayed cracking, characterized by: The automobile anti-collision beam comprises a beam body (1) and a patch reinforcement (2); the inner arc surface of the transition section at both ends of the beam body (1) is rounded off; the patch reinforcement (2) is fixed at the rounded cut-off portion of the inner arc surface; the curvature of the patch reinforcement (2) is the same as the curvature of the transition section on the beam body (1); and the cross-section of the beam body (1) is a "concave" shape.

2. The delayed cracking resistant ultra-high strength steel variable curvature automobile anti-collision beam according to claim 1, characterized in that: The length of the inner arc surface cut off at the transition section of the crossbeam body (1) is the length of the transition section or the length after extending 5 to 100 mm to both sides of the transition section.

3. The delayed cracking resistant ultra-high strength steel variable curvature automobile anti-collision beam according to claim 2, characterized in that: The material strength of the patch reinforcement (2) is different from the material strength of the beam body (1). The material tensile strength of the patch reinforcement (2) is 450-1200 MPa, the material thickness is 1.2-3.5 mm, and the length is 20-200 mm extended on both sides along the length direction of the cut section.

4. The delayed cracking resistant ultra-high strength steel variable curvature automobile anti-collision beam according to claim 3, characterized in that: The patch reinforcement (2) is a C-shaped reinforcement plate, which is buckled to the inner arc surface of the cut transition section and welded to the crossbeam body (1).

5. The delayed cracking resistant ultra-high strength steel variable curvature automobile anti-collision beam according to claim 3, characterized in that: The patch reinforcement (2) comprises a first reinforcement metal plate (2-1) and a second reinforcement metal plate (2-2), both reinforcement metal plates being arranged in a "C" shape, the first reinforcement metal plate (2-1) being buckled to a concave portion in the middle of a "concave"-shaped crossbeam body, and being welded and fixed to two adjacent side walls of two cavities adjacent to the crossbeam body, the second reinforcement metal plate (2-2) being buckled to an inner arc surface of the crossbeam body (1), and the second reinforcement metal plate (2-2) covering the first reinforcement metal plate (2-1).

6. The delayed cracking resistant ultra-high strength steel variable curvature automobile anti-collision beam according to claim 3, characterized in that: The patch reinforcement (2) is configured as a tube and includes eight identical metal tubes (2-3). The metal tubes (2-3) are fixed in pairs at the inner arc cutout of the transition section of the beam body (1). The two metal tubes located in the same cavity at one end of the beam body (1) are welded and fixed to each other, and the metal tube walls are welded or riveted to the cavity wall of the beam body.

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