Integrated high-strength steel multi-cavity automobile door sill reinforcing beam and processing method thereof

Abstract

The application discloses an integrated high-strength steel multi-cavity automobile door sill reinforcing beam and a processing method thereof. The reinforcing beam is integrally formed by roll bending of a high-strength steel plate and has a multi-cavity structure with four closed cavities in a cross section; the reinforcing beam comprises an outer part and an inner part which are stacked one above the other, the outer part is a Chinese character 'Ri' type structure, the inner part is a horizontally arranged Chinese character 'Ri' type structure, and a shared beam wall is arranged between the outer part and the inner part; the reinforcing beam has a variable cross section with a narrow upper part and a wide lower part in the whole cross section, and a connecting portion of the outer part and the inner part is transitioned through a slope. The door sill reinforcing beam has excellent mechanical properties and safety, greatly improves the inertia moment of the cross section to the vertical bending moment, can effectively resist the intrusion of a collision object, can maintain the structural integrity under a severe column impact working condition, simultaneously reduces material cost and processing cost, and realizes efficient production of the door sill reinforcing beam and product light weight.

Description

Technical Field

[0001] This invention relates to the field of automotive technology, and in particular to an integrated high-strength steel multi-cavity automotive door sill reinforcement beam and its processing method. Background Technology

[0002] With the increasing prevalence of the automotive industry, people are paying more and more attention to the safety performance of cars. The safety performance of automotive safety protection systems is particularly important, especially the various supporting components that significantly impact vehicle safety. The door sill reinforcement beam is a crucial structural safety component in the side of the vehicle body. Located between the longitudinal beams of the frame below the door, it runs through the area from the A-pillar to the C-pillar, playing a key role in absorbing collision energy and preventing impact debris from intruding into the passenger compartment during side collisions. Currently, mid-to-high-end models, especially new energy vehicles, commonly use aluminum alloy extruded profiles as door sill reinforcement beams. Aluminum alloy extrusion facilitates the production of closed multi-cavity cross-sections, and the low density of aluminum alloy is beneficial for lightweighting. However, its material cost is high, and its absolute strength for the same cross-section is often lower than that of high-strength steel, limiting its ability to withstand harsh collision conditions. Increasing strength often requires increasing the cross-sectional height or wall thickness, which leads to difficulties in space arrangement and limits the lightweighting effect.

[0003] To reduce costs and increase strength, existing technologies also employ high-strength steel to manufacture door sill reinforcement beams. Traditional steel solutions are mostly based on conventional multi-piece welding processes: multiple simple open or closed cross-section parts are first manufactured by stamping or roll forming, and then these parts are welded together to form a multi-cavity structure. Although this approach utilizes the high specific strength of steel, the multi-piece welding process has a series of inherent drawbacks in terms of manufacturing efficiency, structural integrity, and performance optimization, limiting its further application in advanced vehicle bodies. Specifically: 1. Numerous processes, slow production cycle, and high processing costs. Welding multiple parts requires separate stamping or roll forming of each part, as well as welding assembly and post-weld straightening, among other discrete processes. Each group of parts requires an independent mold or roll forming device, resulting in a large production line footprint and frequent transfers between workstations, making it difficult to achieve continuous and rapid production cycles. Furthermore, the cumulative tolerances from multiple processes pose a challenge to the dimensional consistency of the finished product, often necessitating additional offline fitting and repair welding steps, leading to high manufacturing costs and significant management difficulties.

[0004] 2. There are many welded joints, and the joints are prone to become weak points of the structure, affecting the overall stiffness and fatigue performance. The sill beam bears complex bending, torsion and vibration loads during collisions and daily use. There are tissue gradients and residual tensile stresses in the heat-affected zone of the weld, and its hardness and toughness are usually significantly different from those of the base metal. A large number of welded joints not only interrupt the continuity of the material fibers, but also initiate fatigue cracks in stress concentration areas such as the weld toes, resulting in a significant reduction in the fatigue life of the sill beam. During a side impact, the solder joints or welds often crack first, destroying the integrity of the force transmission path and weakening the structure's ability to protect the occupants and the battery;

[0005] 3. It is difficult to achieve continuous optimization of the cross-sectional shape, which is not conducive to lightweight design. The multi-piece welded structure is composed of assembled separate parts, and the material thickness and cross-sectional geometry can only change stepwise at the part boundaries, and cannot achieve continuous gradual change of material distribution like a single formed part. This results in the same cross-sectional parameters being forced to be used in the high-stress area and low-stress area of the sill beam, making it difficult to achieve equal-strength design; at the same time, the sudden change in stiffness at the mutation will also cause stress concentration and deformation incoordination, affecting the controllability of the collision energy absorption sequence and the crushing mode, and it is difficult to fully exploit the lightweight potential.

[0006] Therefore, there is an urgent need to develop a new structure and processing method for an automotive sill reinforcement beam that can both exert the material cost and performance advantages of high-strength steel, achieve integrated and efficient forming of complex closed cross-sections, and have excellent crashworthiness, lightweight and low manufacturing costs. Summary of the Invention

[0007] To solve the above problems existing in the prior art, the purpose of the present invention is to provide an integrated high-strength steel multi-cavity automotive sill reinforcement beam and its processing method.

[0008] To solve the above technical problems, the technical solution adopted by the present invention is: An integrated high-strength steel multi-cavity automotive sill reinforcement beam, the reinforcement beam is a multi-cavity structure with a cross-section of four closed cavities formed by roll bending a high-strength steel plate; the reinforcement beam includes an outer part and an inner part stacked up and down, the outer part is in a "day" shape structure, the inner part is a horizontally placed "day" shape structure, and there is a shared beam wall between the outer part and the inner part; the cross-sectional width of the outer part is smaller than the cross-sectional width of the inner part, the overall cross-section of the reinforcement beam is in a variable cross-section form with a narrow upper part and a wide lower part, and the connection between the outer part and the inner part is transitioned by an inclined surface. <A further improvement of the present invention is that: the outer part of the vehicle is a rectangular structure formed by an outer lower wall, an outer left wall, an outer upper wall, and an outer right wall; the movable end of the outer lower wall is folded back upward along the outer right wall to form an outer right reinforcing wall, and then bent to the left to form a first central support leg; the first central support leg is horizontally arranged, and its end is welded and fixed to the outer left wall; the first central support leg divides the outer part of the vehicle into a first cavity and a second cavity arranged vertically. The interior of the vehicle is a rectangular structure formed by an inner left wall, an inner lower wall, an inner right wall, and an outer lower wall. The movable end of the inner left wall is folded back along the outer lower wall to form an inner upper wall, and then bent downward to form a second central support leg. The second central support leg is set vertically, and its end is welded and fixed to the inner lower wall. The second central support leg divides the interior of the vehicle into a third cavity and a fourth cavity arranged side by side.

[0010] A further improvement of the present invention is that the movable ends of the first central support leg and the second central support leg are fixed by stacking welding.

[0011] A further improvement of the present invention is that the outer right wall and the inner right wall are connected by a reinforcing diagonal brace, and the inner left wall and the inner upper wall are connected by a transitional diagonal wall.

[0012] A further improvement of the present invention is that the angle α between the reinforcing diagonal brace and the vertical direction, and the angle β between the transition diagonal wall and the vertical direction are 45°.

[0013] A further improvement of the present invention is that the plate used to prepare the threshold reinforcement beam is high-strength or ultra-high-strength steel with a tensile strength of 500MPa or more.

[0014] A method for fabricating a sill reinforcement beam includes the following steps: S1. Unwind and level the high-strength steel strip coil; S2. Pre-punch various process holes and assembly holes on the leveled board; S3. The sheet material is fed into the roll forming device, where it is bent and shaped by multiple sets of rollers and welded at fixed points to complete the forming and closing of four independent cavities. S4. Cut and blank the roll-formed profile to the required length.

[0015] The specific process of the S3 roll forming is as follows: First, the steel strip is bent from both sides to form the welding process outline of the second and third cavities, the first central support leg, and the second central support leg. Then, the upper support wall and side support wall of the second and third cavities are bent in sequence, while simultaneously forming the 45° oblique process edge of the third cavity. When the second and third cavities are closed, they are welded together at the stacked material position. Then, the rounded corners and support walls of the first and fourth cavities are bent and formed, while simultaneously forming the 45° oblique process edge of the fourth cavity, until the first and fourth cavities are completely closed. Then, the stacked material is penetrated and seam welded. Finally, the cross-section is finished, thus completing the forming of the four independent cavity structures of the sill reinforcement beam.

[0016] In step S3, the cold bending forming process of the sheet metal includes ten stages: In the first stage, the steel strip is first bent from both sides to form the second and third cavities through welding processes, and then the first and second central support legs are formed; a total of 9 forming processes are involved. In the second stage, the upper support walls of the second and third cavities are bent to a certain angle on both sides of the strip, while the third cavity is formed at a 45° angle; a total of 4 forming passes are performed. In the third stage, the side support walls of the second and third cavities are bent to a certain angle on both sides of the material strip; a total of 5 forming passes are performed. In the fourth stage, multiple bending and springback control processes are performed to complete the upper support wall and side support wall of the second and third cavities, and the 45° inclined process edge of the third cavity to the theoretical angle. The stacked material positions are then welded to achieve the cut-off closure. A total of 4 forming processes are involved. In the fifth stage, the lower support wall of the first cavity is bent to a certain angle, and the lower support wall of the fourth cavity begins to be formed during the forming process; a total of 5 forming passes are performed. In the sixth stage, the lower support wall of the fourth cavity is bent and shaped to a certain angle, and the side support wall of the first cavity begins to be shaped during the process; a total of 3 shaping passes are required. In the seventh stage, the side support wall of the fourth cavity is bent to a certain angle; a total of 3 forming passes are required. The eighth stage involves bending and forming the fourth cavity at a 45° angle; this process is completed in four stages. In the ninth stage, multiple bending and springback control processes are performed to bring the lower and side support walls of the first and fourth cavities to the theoretical angle. Then, stacked material penetration welding and seam welding are carried out to achieve the closure of the cross-section; a total of 4 forming processes are involved. In the tenth stage, the sizing mill unit performs more precise cross-sectional accuracy control; a total of 3 forming passes are required.

[0017] In the fourth stage, the second and third cavities are sealed by two overlapping welding operations; in the ninth stage, the first cavity is sealed by overlapping through welding, and the fourth cavity is sealed by seam welding.

[0018] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows: This invention discloses a novel automotive door sill reinforcement beam structure. Formed integrally from a single high-strength steel plate through continuous roll bending, it features four closed cavities, effectively improving the strength, rigidity, and bending resistance of the door sill beam. Furthermore, it enables rapid force transfer and cushioning upon impact. Its advantages are mainly reflected in the following aspects: 1. Excellent mechanical properties and safety. The width of the exterior portion of the door sill reinforcement beam in this invention is smaller than the width of the interior portion, and the exterior and interior portions are smoothly transitioned through a 45° reinforced diagonal brace and a transitional inclined wall. In the event of a side collision, the exterior portion is prone to controlled crushing in the initial stage of the collision, efficiently converting the collision kinetic energy into plastic deformation energy, effectively absorbing the collision energy, and playing a role in buffering and reducing the peak collision force. The 45° reinforced diagonal brace and transitional inclined wall play a role in guiding and dispersing the force, smoothly and directionally transferring the unabsorbed residual load to the interior portion, avoiding local stress concentration and weld cracking. The interior is divided into a wide, transverse H-shaped structure, with the second central support leg in the middle providing extremely high vertical bending stiffness, greatly improving the moment of inertia of the section about the vertical bending moment, effectively resisting the intrusion of the colliding object, and maintaining structural integrity even under harsh pole impact conditions, achieving a significant improvement in collision safety performance and maximizing the integrity of the passenger compartment.

[0019] In this invention, the free ends of the first central support leg and the second central support leg are provided with welded hooks, which can ensure the connection between the first central support leg and the second central support leg, provide more stable support, and at the same time, can transmit the force more quickly when subjected to force, quickly disperse the impact force, and reduce the local stress.

[0020] The bending angles of the four enclosed cavities in this invention are all rounded, which allows the impact force to be transmitted synchronously along the symmetrically arranged plates when subjected to force, resulting in more uniform force distribution and the absence of blind spots.

[0021] 2. Significant Manufacturing Cost Advantages. This invention uses high-strength steel plates instead of aluminum alloy profiles, significantly reducing raw material costs. In terms of manufacturing process, the traditional multi-part stamping and welding process is replaced by integrated continuous roll forming of a single steel strip. This achieves a complex closed four-cavity structure in one step, eliminating the need for multiple parts forming devices and a large number of welding fixtures. This greatly simplifies the production line length, reduces the number of molds, welding stations, and labor, and decreases the number of operators and welding consumables. Overall, material costs, production line layout, labor, and production auxiliary materials are all significantly reduced. The overall manufacturing cost of a single sill reinforcement beam has a significant advantage over both aluminum alloy solutions and multi-part welded steel solutions.

[0022] 3. High-efficiency production and lightweight design. This invention employs continuous roll forming of a single steel plate, resulting in a fast production cycle and significantly higher efficiency than the intermittent production mode of stamping and welding multiple parts. The one-piece forming structure of this invention avoids redundant materials resulting from welding. Under the same or better collision safety performance, the structural weight of the sill reinforcement beam of this invention is effectively reduced, achieving structural lightweighting.

[0023] 4. Excellent processability and environmental friendliness. Roll forming is a continuous plastic processing method, eliminating the waste of sheet metal caused by stacking sheets in traditional forming processes. Waste is only generated at the end-length cutting and a small number of process holes, resulting in high material utilization and low waste. Compared with aluminum alloy production, the steel industry is mature, with a well-established scrap steel recycling system, which is more in line with low-carbon and environmental protection requirements. The roll forming process is low-noise, produces no hazardous waste emissions or dust, and meets the requirements of clean production.

[0024] 5. Integrated processing method ensures structural precision and consistency. This invention also discloses a processing method for the sill reinforcement beam. High-strength or ultra-high-strength steel with a tensile strength of over 500MPa is selected as the forming material. The strength and toughness of the steel itself provide a fundamental guarantee for the strength and impact resistance of the sill reinforcement beam. During processing, a total of forty-four rolling processes are used to gradually process the steel strip into a four-closed cavity structure. During each rolling, the high-strength steel undergoes only small and uniform plastic deformation, reducing the forming force. The internal metal fibers remain intact and continuous, effectively overcoming the problems of low elongation, easy micro-fracture during cold bending, and weak structure of ultra-high-strength steel. There are no abrupt changes in mechanical properties caused by welding joints, resulting in a sill reinforcement beam with outstanding characteristics such as good cross-sectional dimension consistency, low residual stress level, and uniform stiffness along the length direction, ensuring the reliability and consistency of the product under collision and fatigue conditions. The welding method uses laser welding, which concentrates heat input, has a large weld depth-to-width ratio, and a narrow heat-affected zone. This ensures that the strength of the closed weld is no less than that of the base material, and the welding deformation is minimal. It can precisely maintain the product size and cross-sectional shape, thereby ensuring the stability and high strength of the threshold reinforcement beam structure.

[0025] The processing method of this invention has strong versatility. Depending on the vehicle model's requirements for the sill reinforcement beam, the material, plate wall thickness, and dimensions of the sill reinforcement beam can be adaptively adjusted. During processing, only the rolling parameters of the corresponding rolling mechanism need to be adjusted to achieve the processing of sill reinforcement beams of different sizes, significantly reducing the difficulty of developing new products. Attached Figure Description

[0026] Figure 1 This is a schematic cross-section of the threshold reinforcement beam of the present invention. Figure 1 ; Figure 2 This is a schematic cross-section of the threshold reinforcement beam of the present invention. Figure 2 ; Figure 3 This is a schematic diagram of the sill beam structure of the present invention; Figure 4 This is a schematic diagram of the deformation during the 1-22 roller pressing passes of the processing method of the present invention; Figure 5 This is a schematic diagram of the deformation during the 23-44 roller pressing passes in the processing method of the present invention; Figure 6 This is a schematic diagram of the roller pattern of the present invention; Figure 7 This is a connection block diagram of the processing production line of the present invention; Figure 8 This is a schematic diagram of the equipment connection of the processing production line of the present invention; In the diagram, 1. Exterior part of the vehicle; 1-1. Lower outer wall; 1-2. Left outer wall; 1-3. Upper outer wall; 1-4. Right outer wall; 1-5. Right outer reinforcing wall; 1-7. First central support leg; 2. Interior part of the vehicle; 2-1. Left inner wall; 2-2. Lower inner wall; 2-3. Right inner wall; 2-4. Upper inner wall; 2-5. Second central support leg; 3. First cavity; 4. Second cavity; 5. Third cavity; 6. Fourth cavity; 7. Reinforcing diagonal brace; 8. Transition diagonal wall; 9. Weld point; A. Outer sill plate; B. Inner sill plate; C. Sill reinforcing beam. 10. Uncoiling machine; 20. Leveling machine; 30. Mechanical press; 40. Servo feeding mechanism; 50. Missing punch detection mechanism; 60. Pit bridge; 70. First cold bending forming unit; 80. First welding mechanism; 90. Second cold bending forming unit; 100. Second welding mechanism; 110. Cutting mechanism; 120. Receiving mechanism. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] A one-piece high-strength steel multi-cavity car door sill reinforcement beam, such as Figure 1As shown, it is a multi-cavity structure formed by roll bending a steel plate integrally, with a cross-section presenting four closed cavities. The reinforcing beam includes an outer part 1 and an inner part 2 stacked up and down. The outer part 1 is located above, and its cross-section is in the shape of a Chinese character 'Ri', having two vertically arranged closed cavities; the inner part 2 is located below the outer part 1, and its cross-section is in the shape of a horizontally placed Chinese character 'Ri', having two horizontally arranged closed cavities. A common beam wall is shared between the bottom of the outer part 1 and the top of the inner part 2 to achieve enclosure.

[0029] To ensure the strength and anti-collision performance of the sill reinforcing beam, the steel used in this invention is high-strength steel, such as high-strength or ultra-high-strength steel with a tensile strength above 500 MPa.

[0030] As Figure 2 shown, the cross-sectional width of the outer part 1 is smaller than that of the inner part 2. The width of the outer part 1 is W1, and the width of the inner part 2 is W2, where W1 < W2, making the cross-section of the sill reinforcing beam in the form of a variable cross-section with a narrower upper part and a wider lower part. As can be seen from the figure, the area of the two closed cavities in the outer part 1 is smaller than the area of the two closed cavities in the inner part 2.

[0031] When the raw material is 500 - 1000 MPa high-strength steel, W2 - W1 is not less than 6 times the material thickness; when the raw material is 1000 - 1500 MPa high-strength steel, W2 - W1 is not less than 8 times the material thickness.

[0032] The cavities of the sill reinforcing beam are in a rectangular or nearly rectangular structure, with a regular shape and strong support force; a common beam wall is used to achieve enclosure between the bottom of the outer part 1 and the top of the inner part 2. Only one weld spot is provided on one side of the connection between the outer part 1 and the inner part 2 on the surface of the sill reinforcing beam, and the rest of the surface is a continuous smooth surface formed by bending and plasticity of the sheet material without welded joints, without stress weak points, which is beneficial for assembly. A reinforcing diagonal brace 7 is provided at the continuous transition between the outer part 1 and the inner part 2 to enhance the connection strength between the outer part 1 and the inner part 2.

[0033] Specifically, the outer part 1 is a rectangular structure enclosed by an outer lower wall 1-1, an outer left wall 1-2, an outer upper wall 1-3, and an outer right wall 1-4. The movable end of the outer lower wall 1-1 is folded upward along the outer right wall 1-4 to form an outer right reinforcing wall 1-5, and then bent leftward to form a first central leg 1-6. The first central leg 1-6 is horizontally arranged, and its end is welded and fixed to the outer left wall 1-2; the first central leg 1-6 divides the outer part 1 into a first cavity 3 and a second cavity 4 arranged vertically. As Figure 1As shown, the first cavity 3 is formed by the outer right wall 1-4, the outer upper wall 1-3, the outer left wall 1-2, and the first central support leg 1-6, and the second cavity 4 is formed by the outer right reinforcing wall 1-5, the first central support leg 1-6, the outer left wall 1-2, and the outer lower wall 1-1.

[0034] The interior portion 2 is a rectangular structure enclosed by an inner left wall 2-1, an inner lower wall 2-2, an inner right wall 2-3, and an outer lower wall 1-1. The movable end of the inner left wall 2-1 is folded back along the outer lower wall 1-1 to form an inner upper wall 2-4, and then bent downwards to form a second central support leg 2-5. The second central support leg 2-5 is vertically arranged, and its end is welded and fixed to the inner lower wall 2-2. The second central support leg 2-5 divides the interior portion 2 into a third cavity 5 and a fourth cavity 6 arranged side by side. Figure 1 As shown, the third cavity 5 is formed by the inner upper wall 2-4, the inner left wall 2-1, the inner lower wall 2-2, and the second central support leg 2-5; the fourth cavity 6 is formed by the second central support leg 2-5, the inner lower wall 2-2, the inner right wall 2-3, and the outer lower wall 1-1.

[0035] The movable ends of the first central support leg 1-6 and the second central support leg 2-5 are fixed by overlapping welding. Generally, the overlapping length is not less than 4.5 times the material thickness to ensure welding strength and impact resistance of the final profile product.

[0036] The connection between the exterior part 1 and the interior part 2 is achieved through a beveled transition to enhance the strength of the sill reinforcement beam. Specifically, as follows... Figure 2 As shown, the outer right wall 1-4 and the inner right wall 2-3 are connected by a reinforcing diagonal brace 7, and the inner left wall 2-1 and the inner upper wall 2-4 are connected by a transitional diagonal wall 8 to form a diagonal brace structure. The presence of the reinforcing diagonal brace 7 and the transitional diagonal wall 8 increases the connection strength between the outer part 1 and the inner part 2, and also makes the force transmission path of the outer part 1 smoother, allowing the impact force to be transmitted more smoothly from the outer part 1 to the inner part 2, and quickly dissipating the force.

[0037] The angle α between the reinforcing brace 7 and the vertical direction, and the angle β between the transition inclined wall 8 and the vertical direction are 45°. At this point, the structural stability and impact transmission performance of the sill reinforcement beam are optimal.

[0038] In this invention, except for the transition inclined wall 8, the corners of the first cavity 3, the second cavity 4, the third cavity 5, and the fourth cavity 6 are all rounded, which reduces stress points and increases anti-collision performance.

[0039] In the profile of this invention, the thickness of the plates for the outer lower wall 1-1, outer left wall 1-2, outer upper wall 1-3, outer right wall 1-4, inner left wall 2-1, inner lower wall 2-2, inner right wall 2-3, first central support leg 1-6, and second central support leg 2-5 can be the same or different, and all are within the protection scope of this invention. It should be noted that in this embodiment, the plate thickness at each location of the sill reinforcement beam is the same; however, if the user requires different wall thicknesses at certain locations of the sill reinforcement beam due to actual requirements on the strength, installation space, or overall weight, this can be achieved by using plates of unequal thickness.

[0040] A type of threshold beam, such as Figure 3 As shown, it includes an outer sill plate A and an inner sill plate B that are installed together, and an integrated high-strength steel multi-cavity automotive sill reinforcement beam C is installed between the outer sill plate A and the inner sill plate B.

[0041] The processing method of the integrated high-strength steel multi-cavity automotive door sill reinforcement beam includes the following steps: S1. Unwind and level the high-strength steel strip coil; S2. Pre-punch various process holes and assembly holes on the leveled board; S3. The sheet material is fed into the roll forming device, where it is bent and shaped by multiple sets of rollers and welded at fixed points to complete the forming and closing of four independent cavities. S4. Cut and blank the roll-formed profile to the required length.

[0042] The roll forming process of S3 is as follows: First, the steel strip is bent from both sides to form the welding process outline of the second and third cavities, the first central support leg, and the second central support leg. Then, the upper support wall and side support wall of the second and third cavities are bent in sequence, while simultaneously forming the 45° oblique process edge of the third cavity. When the second and third cavities are closed, they are welded together at the stacked material position. Then, the rounded corners and support walls of the first and fourth cavities are bent and formed, while simultaneously forming the 45° oblique process edge of the fourth cavity, until the first and fourth cavities are completely closed. Then, the stacked material is penetrated and seam welded. Finally, the cross-section is finished, thus completing the forming of the four independent cavity structures of the sill reinforcement beam.

[0043] like Figure 4-6 As shown, the cold bending forming process of the sill reinforcement beam includes ten stages: In the first stage, after 1-9 sets of roller pressing, the steel strip is first bent from both sides to form the second and third cavities through welding and edge-finding processes, the first central support leg, and the second central support leg; a total of 9 forming processes are performed. In the second stage, the material strip is bent into the upper support walls (i.e., the outer right reinforcing wall and the inner upper wall) of the second and third cavities by 10-13 sets of roller pressing to a certain angle, while the third cavity is formed at a 45° angle (i.e., the transition inclined wall); a total of 4 forming passes are performed. In the third stage, the material strip is bent into the side support walls (i.e., the outer lower wall and the inner left wall) of the second and third cavities by 14-18 sets of rollers to a certain angle; a total of 5 forming passes are required. In the fourth stage, after 19-22 sets of roller pressing, multiple bending and springback control, the upper support wall and side support wall of the second and third cavities and the 45° inclined process edge of the third cavity are completed to the theoretical angle. The stacked material position is welded to achieve the cut-off closure; a total of 4 forming passes are required. In the fifth stage, the lower support wall of the first cavity is bent to a certain angle through 23-27 sets of roller pressing, and the lower support wall of the fourth cavity begins to be formed during the forming process; a total of 5 forming passes are required. In the sixth stage, after 28-30 sets of roller pressing, the lower support wall of the fourth cavity is bent and formed to a certain angle. During the forming process, the side support wall of the first cavity begins to be formed. A total of 3 forming passes are required. In the seventh stage, after 31-33 sets of roller pressing, the side support wall of the fourth cavity is further bent to a certain angle; a total of 3 forming passes are required. In the eighth stage, the fourth cavity is formed by bending and shaping the fourth cavity at a 45° angle (i.e., reinforcing diagonal brace) through 34-37 sets of roller pressing; a total of 4 forming passes are required. In the ninth stage, after 38-41 sets of roller pressing, multiple bending and springback control, the lower support wall and side support wall of the first cavity and the fourth cavity are completed to the theoretical angle. Stacked material penetration welding and seam welding are then performed to achieve the closure of the section. A total of 4 forming passes are required. In the tenth stage, the sizing unit uses 42-44 sets of rollers to achieve more precise control over the cross-sectional accuracy; a total of 3 forming passes are required.

[0044] In the fourth stage, the second and third cavities are closed through two overlapping welds; in the ninth stage, the first cavity is closed through one overlapping through-weld, and the fourth cavity is closed through one seam weld. These four welds create four closed cavities, ensuring the stability and strength of the structure. The welding method can be arc welding or fusion welding, selected based on the manufacturer's actual processing capabilities and ease of processing; laser welding is preferred due to its fast welding speed and high welding strength, ensuring not only welding strength but also improving the overall processing efficiency of the sill reinforcement beam.

[0045] In the aforementioned stage, "forming to a certain angle" refers to the target bending angle at this stage, which is not the final theoretical angle, but rather an intermediate angle determined by retaining a specific fillet that is temporarily excluded from forming, thereby maintaining the necessary opening. Its specific value is determined by the following factors: the roller inlet width of the area to be formed, the radius of the fillet that is temporarily excluded from forming, the included angle between its adjacent walls, and the yield strength and springback characteristics of the material. This control method allows the corner to be directly compacted by the rollers in an open state, ensuring sufficient material flow, full fillet forming, reducing unnecessary transition bends, and thus improving forming accuracy.

[0046] The aforementioned "multiple bending" refers to the progressive forming process in the same characteristic area of ​​the same cavity, through no less than two passes, with each bending angle increment not exceeding 30°, in order to avoid excessive material hardening or local necking.

[0047] The aforementioned "springback control" refers to setting the forming angle to the theoretical angle plus the springback compensation value in the final pass, based on the material's yield strength and actual springback test data. After final forming, the actual angle deviation is controlled within ±1°.

[0048] The ten stages of the cold bending forming process of this invention strictly follow the overall sequence of "first the two ends, then the middle; first the inside, then the outside; first forming, then closing." Its process principle lies in: 1. Due to its complex internal structure, it needs to be formed first to ensure accuracy. The second and third cavities of the multi-cavity threshold reinforcement beam contain complex features such as welded edges and 45° angled process edges. If these internal features are attempted to be formed after the cavity is closed, the rollers cannot enter the closed section; therefore, they must be completed first while the cavity is open.

[0049] 2. Pre-forming the internal structure ensures that each rounded corner is firmly pressed. The core of cold bending forming lies in actually pressing the material (rather than freely bending) in each pass. In this scheme, all internal fillets are formed pass by pass within a fully constrained roller gap in the first to fourth stages, avoiding the risk that the fillet area cannot be compacted due to subsequent closure.

[0050] 3. The order of working from both sides to the middle ensures overall stability. After the second and third cavities are closed, a "rigid skeleton" is formed, which provides a stable force boundary for the subsequent bending of the first and fourth cavities, and avoids twisting or displacement during the asymmetric forming process.

[0051] 4. Closed finishing The first and fourth cavities are then formed and closed using the same logic in stages five through nine. Finally, the tenth-stage sizing unit performs overall precision correction to avoid premature sizing that could lead to subsequent bending damage to the formed cross-section.

[0052] Production lines based on the above processing methods, such as Figure 7 , Figure 8 As shown, it includes an uncoiler 10, a leveler 20, a mechanical press 30, a servo feeding mechanism 40, a hole punching detection mechanism 50, a pit bridge 60, a first cold bending forming unit 70, a first welding mechanism 80, a second cold bending forming unit 90, a second welding mechanism 100, a cutting mechanism 110, and a receiving mechanism 120.

[0053] The uncoiler 10 and leveler 20 are used for uncoiling and leveling high-strength steel plates, preparing the plates before roll forming to ensure the accuracy of roll forming. The mechanical press 30 is used for pre-punching the mounting holes of the plates to meet the installation and connection requirements of the sill reinforcement beam and other components. Downstream of the mechanical press 30, there are a servo feeding mechanism 40 and a missing punch detection mechanism 50. The servo feeding mechanism 40 is used to assist in the fixed-length feeding of the pre-punched holes, and the missing punch detection mechanism 50 is used to check whether there are any missing punches in the stamping unit.

[0054] Since the punching speed and the metal sheet feeding speed are not necessarily the same, a pit bridge 60 is provided upstream and downstream of the mechanical press 30 to store metal sheet materials. This ensures that the upstream and downstream processing is not affected when the production speeds are different. It is mainly used for the mechanical press 30 and the material belts required upstream and downstream to correct deviation.

[0055] Both the first cold bending forming unit 70 and the second cold bending forming unit 90 are equipped with multiple pressure rollers. The shape and arrangement of the pressure rollers are set according to the cross-section of the sill reinforcement beam. When the cross-section of the sill reinforcement beam is modified, the adjustment can be achieved by changing the number of passes and the shape of the pressure rollers in the corresponding cold bending forming unit. Different structural products can be processed with relatively minor equipment modifications.

[0056] Specifically, the first cold bending forming unit 70 is mainly used for forming the first cavity and the fourth cavity, and a first welding mechanism 80 for welding and closing the first cavity and the fourth cavity is provided downstream of the first cold bending forming unit 70. The second cold bending forming unit 90 is mainly used for forming the second cavity and the third cavity, and a second welding mechanism 100 for welding and closing the second cavity and the third cavity is provided downstream of the second cold bending forming unit 90.

[0057] The welding machine in the first welding mechanism 80 can be a spot welder, an arc welder, or a fusion welder, preferably a dual-laser welder; the welding machine in the second welding mechanism 100 can be an arc welder or a fusion welder, preferably a laser welder. During welding, to ensure welding accuracy and effect, welding fixtures are also installed at both ends of the welding machine. These fixtures allow for pre-shaping of the profile to be welded, effective clamping and limiting of the profile during welding, and post-weld shaping and fixing of the rolled profile, preventing weld and profile deformation. The structure of the welding fixtures is adapted to the welding position.

[0058] The cutting mechanism 110 is used to cut the processed profile to a fixed length, and the receiving mechanism 120 is used to receive the sill reinforcement beam product after cutting.

[0059] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A one-piece high-strength steel multi-cavity automotive door sill reinforcement beam, characterized in that: The reinforcing beam is a multi-cavity structure with four closed cavities in cross-section, formed by rolling and bending a high-strength steel plate. The reinforcing beam includes an outer part (1) and an inner part (2) that are stacked on top of each other. The outer part (1) is a H-shaped structure and the inner part (2) is a horizontally placed H-shaped structure. There is a common beam wall between the outer part (1) and the inner part (2). The cross-sectional width of the outer part (1) is smaller than that of the inner part (2). The cross-section of the reinforcing beam is a variable cross-section that is narrower at the top and wider at the bottom. The connection between the outer part (1) and the inner part (2) is made by a slope transition.

2. The integrated high-strength steel multi-cavity automobile door sill reinforcement beam according to claim 1, characterized in that: The vehicle exterior (1) is a rectangular structure formed by the outer lower wall (1-1), outer left wall (1-2), outer upper wall (1-3), and outer right wall (1-4). The movable end of the outer lower wall (1-1) is folded back upward along the outer right wall (1-4) to form an outer right reinforcing wall (1-5), and then bent to the left to form a first central support leg (1-6). The first central support leg (1-6) is horizontally arranged, and its end is welded and fixed to the outer left wall (1-2). The first central support leg (1-6) divides the vehicle exterior (1) into a first cavity (3) and a second cavity (4) arranged vertically. The interior part (2) is a rectangular structure formed by the inner left wall (2-1), the inner lower wall (2-2), the inner right wall (2-3), and the outer lower wall (1-1). The movable end of the inner left wall (2-1) is folded back along the outer lower wall (1-1) to form the inner upper wall (2-4), and then bent downward to form the second central support leg (2-5). The second central support leg (2-5) is set vertically, and its end is welded and fixed to the inner lower wall (2-2). The second central support leg (2-5) divides the interior part (2) into the third cavity (5) and the fourth cavity (6) arranged side by side.

3. The integrated high-strength steel multi-cavity automobile door sill reinforcement beam according to claim 2, characterized in that: The movable ends of the first central support leg (1-6) and the second central support leg (2-5) are fixed by stacking welding.

4. The integrated high-strength steel multi-cavity automobile door sill reinforcement beam according to claim 2, characterized in that: The outer right wall (1-4) and the inner right wall (2-3) are connected by a reinforcing diagonal brace (7), and the inner left wall (2-1) and the inner upper wall (2-4) are connected by a transitional diagonal wall (8).

5. The integrated high-strength steel multi-cavity automobile door sill reinforcement beam according to claim 4, characterized in that: The angle α between the reinforcing diagonal brace (7) and the vertical direction, and the angle β between the transition diagonal wall (8) and the vertical direction are 45°.

6. The integrated high-strength steel multi-cavity automobile door sill reinforcement beam according to any one of claims 1 to 5, characterized in that: The plate used to prepare the threshold reinforcement beam is high-strength or ultra-high-strength steel with a tensile strength of 500MPa or more.

7. A method for processing a sill reinforcement beam as described in any one of claims 1-6, characterized in that... Includes the following steps: S1. Unwind and level the high-strength steel strip coil; S2. Pre-punch various process holes and assembly holes on the leveled board; S3. The sheet material is fed into the roll forming device, where it is bent and shaped by multiple sets of rollers and welded at fixed points to complete the forming and closing of four independent cavities. S4. Cut and blank the roll-formed profile to the required length.

8. The processing method according to claim 7, characterized in that, The specific process of the S3 roll forming is as follows: First, the steel strip is bent from both sides to form the welding process outline of the second and third cavities, the first central support leg, and the second central support leg. Then, the upper support wall and side support wall of the second and third cavities are bent in sequence, while simultaneously forming the 45° oblique process edge of the third cavity. When the second and third cavities are closed, they are welded together at the stacked material position. Then, the rounded corners and support walls of the first and fourth cavities are bent and formed, while simultaneously forming the 45° oblique process edge of the fourth cavity, until the first and fourth cavities are completely closed. Then, the stacked material penetration welding and seam welding are performed. Finally, the cross-section is finished, thus completing the forming of the four independent cavity structures of the sill reinforcement beam.

9. The processing method according to claim 8, characterized in that, In step S3, the cold bending forming process of the sheet metal includes ten stages: In the first stage, the steel strip is first bent from both sides to form the second and third cavities through welding processes, and then the first and second central support legs are formed; a total of 9 forming processes are involved. In the second stage, the upper support walls of the second and third cavities are bent to a certain angle on both sides of the strip, while the third cavity is formed at a 45° angle; a total of 4 forming passes are performed. In the third stage, the side support walls of the second and third cavities are bent to a certain angle on both sides of the material strip; a total of 5 forming passes are performed. In the fourth stage, multiple bending and springback control processes are performed to complete the upper support wall and side support wall of the second and third cavities, and the 45° inclined process edge of the third cavity to the theoretical angle. The stacked material positions are then welded to achieve the cut-off closure. A total of 4 forming processes are involved. In the fifth stage, the lower support wall of the first cavity is bent to a certain angle, and the lower support wall of the fourth cavity begins to be formed during the forming process; a total of 5 forming passes are performed. In the sixth stage, the lower support wall of the fourth cavity is bent and shaped to a certain angle, and the side support wall of the first cavity begins to be shaped during the process; a total of 3 shaping passes are required. In the seventh stage, the side support wall of the fourth cavity is bent to a certain angle; a total of 3 forming passes are required. The eighth stage involves bending and forming the fourth cavity at a 45° angle; this process is completed in four stages. In the ninth stage, multiple bending and springback control processes are performed to bring the lower and side support walls of the first and fourth cavities to the theoretical angle. Then, stacked material penetration welding and seam welding are carried out to achieve the closure of the cross-section; a total of 4 forming processes are involved. In the tenth stage, the sizing mill unit performs more precise cross-sectional accuracy control; a total of 3 forming passes are required.

10. The processing method according to claim 9, characterized in that, In the fourth stage, the second and third cavities are sealed by two overlapping welding operations; in the ninth stage, the first cavity is sealed by overlapping through welding, and the fourth cavity is sealed by seam welding.

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