Variable wall thickness hollow beam forming process

Abstract

The application provides a variable wall thickness hollow beam forming process, and belongs to the technical field of vehicle anti-collision beams. In the variable wall thickness hollow beam forming process, the continuous change control of the wall thickness and the pipe diameter of the metal pipe is realized through a hammer forging step and a reducing step. The reducing pipe blank is bent through a bending step, so that the control of the beam body trend is realized. Through a preforming step, the preset of the beam body cross section shape is realized, and the forming of the beam body is realized through a hot gas expansion forming step. The specific cross section shape of the beam body can be controlled by the die used in the hot gas expansion. Compared with the traditional roll forging, bending, pre-forging and final forging mode, the process flow is optimized. The sleeve pipe is sleeved on the transition section with large bearing force, so that the strength of the place can be increased. The hollow beam rotary forging equipment can quickly realize the hammer forging step and the reducing step. The anti-collision beam produced by the above-mentioned variable wall thickness hollow beam forming process has high structural strength and can realize light weight.

Description

Technical Field

[0001] This application belongs to the field of vehicle anti-collision beam technology, and more specifically, it relates to a forming process for a hollow beam with variable wall thickness. Background Technology

[0002] A crash beam is a device used to absorb collision energy when a vehicle is involved in a collision, and it plays a crucial role in the structural design of a car. Compared to open-section crossbeams, closed-section crossbeams offer better bending resistance, and their variable cross-section and curvature shapes are used to meet regulatory requirements.

[0003] CN113335211A (publication date: September 3, 2021) discloses a method for manufacturing a closed-section anti-collision beam and crossbeam with variable cross-section and variable curvature, which achieves high anti-collision performance through its variable cross-section and variable curvature shape. However, with the increasing demand for vehicle lightweighting, the need for weight reduction also increases. The aforementioned patent's solution produces an anti-collision beam with a uniform wall thickness. Considering the uneven stress distribution throughout the anti-collision beam, rationally designing the wall thickness of different parts—that is, designing relatively thicker walls for parts with higher stress and relatively thinner walls for parts with lower stress—can promote lightweighting. Therefore, providing suitable forming processes and equipment to manufacture anti-collision beams with uneven wall thickness and continuously varying cross-sections is particularly important. Summary of the Invention

[0004] In a first aspect, the present invention provides a process for forming hollow beams with variable wall thickness, which can produce hollow closed-section anti-collision beams with uneven wall thickness distribution and continuously changing cross-section.

[0005] To achieve the above objectives, the technical solution adopted in this application is: to provide a process for forming hollow beams with variable wall thickness, comprising:

[0006] Hammering steps: Heat the metal tube to the hammering temperature, insert a mandrel into the metal tube, and hammer the metal tube circumferentially from the outside. The hammering stroke gradually decreases from the middle to both ends of the metal tube, forming a metal tube blank with a continuously varying wall thickness along the axial direction. The wall thickness of the metal tube blank gradually decreases from both ends to the middle.

[0007] Reduction step: Remove the mandrel from the metal tube blank, heat the metal tube to the forging temperature, and perform circumferential forging on the metal tube blank from the outside. The forging stroke increases from the middle to both ends of the metal tube blank, forming a reduced-diameter tube blank with the outer diameter gradually decreasing from the middle to both ends.

[0008] Sleeving process: Sleeves are attached to both ends of the reduced diameter tube blank, with the two sleeves symmetrically arranged on both sides of the reduced diameter tube blank.

[0009] Bending steps: Bend the reduced diameter tube blank near both ends to form an arched tube blank;

[0010] Preforming step: The arched tube blank is stamped with a stamping die to form a preformed tube blank with a continuously changing cross-sectional shape from the middle to both ends; the preformed tube blank is divided into a middle preformed section, a transition preformed section and an end preformed section from the middle to both ends. The sleeve is located in the transition preformed section, and the bending point of the preformed tube blank is located between the transition preformed section and the end preformed section.

[0011] Hot gas expansion forming steps: The preformed tube blank is processed into the main beam body using the hot gas expansion forming process. The middle preformed section is formed into the middle section, the transition preformed section is formed into the transition section, and the end preformed section is formed into the end section.

[0012] Optionally, in the preforming step, the cross-section of the middle preforming section is "I" shaped, and the cross-sections of the transition preforming section and the end preforming section are "L". The bottom wall width of the transition preforming section is greater than the bottom wall width of the end preforming section, and the height of the transition preforming section is greater than the height of the end preforming section.

[0013] In the hot gas expansion forming step, the middle section and the transition section are both in the shape of "I", and the end section is in the shape of "convex". The bottom wall width of the transition section is greater than the width of the middle section and the end section, the top wall width of the transition section is less than the width of the middle section and the end section, and the height of the transition section is greater than the height of the middle section and the end section.

[0014] Optionally, in the sleeve step, the sleeve and the reduced diameter tube blank are connected by welding or bonding.

[0015] Optionally, the metal tube material is Q550, and the forging temperature range is 800℃ to 950℃.

[0016] Optionally, in the bending step, the reduced diameter tube blank is bent using a pressure bending process or a wrapping bending process.

[0017] Secondly, the present invention provides a hollow beam rotary forging equipment for the above-mentioned hammer forging and diameter reduction steps, to produce a diameter-reduced tube blank with varying wall thickness and continuously varying outer diameter.

[0018] To achieve the above objectives, the technical solution adopted in this application is: to provide a hollow beam rotary forging equipment, including a forging device, a pipe clamping device and a mandrel transfer device, wherein the pipe clamping device and the mandrel transfer device are respectively located on both sides of the forging device, and the forging device includes a plurality of punches distributed in a ring;

[0019] The pipe clamping device includes a first support base and a pipe clamping mechanism. The pipe clamping mechanism is slidably disposed on the first support base along the arrangement direction of the pipe clamping device, the forging device and the mandrel transfer device. The pipe clamping mechanism is rotatably disposed with clamping components for clamping the pipe towards the side wall of the forging device.

[0020] The mandrel transfer device includes a second support base and a mandrel transfer mechanism. The mandrel transfer mechanism is slidably arranged on the second support base along the arrangement direction of the pipe clamping device, the punching and forging device, and the mandrel transfer device. A mandrel is installed on the side wall of the mandrel transfer mechanism facing the punching and forging device.

[0021] The arrangement centers of the clamping components, the multiple punches, and the axis of the mandrel coincide with each other.

[0022] Optionally, the pipe clamping mechanism includes a first sliding seat, a first transfer motor, and a rotating motor. The first transfer motor and the rotating motor are both installed on the first sliding seat. The first support base is provided with a first slide rail and a first rack arranged in parallel with the first slide rail. The first sliding seat is slidably arranged on the first slide rail. The first transfer motor is drivingly connected with a first gear meshing with the first rack. The clamping component is a material clamp drivingly connected with the rotating motor.

[0023] Optionally, the mandrel transfer mechanism includes a second sliding seat, a second transfer motor, and a three-jaw chuck. The second transfer motor and the three-jaw chuck are both installed on the second sliding seat. The second support base is provided with a second slide rail and a second rack arranged in parallel with the second slide rail. The second sliding seat is slidably arranged on the second slide rail. The second transfer motor is drivingly connected with a second gear meshing with the second rack. The end of the mandrel is clamped by the three-jaw chuck.

[0024] Optionally, a heating coil is coaxially arranged between the clamping component and the multiple punches.

[0025] In a third aspect, the present invention provides an anti-collision beam, which achieves lightweight while ensuring strength.

[0026] To achieve the above object, the technical solution adopted by the present application is: to provide an anti-collision beam, including a beam main body with a hollow closed cross-section. The beam main body is arched. The beam main body includes a middle section, a transition section, and an end section arranged in sequence from the middle to the two ends. The bending part of the beam main body is located between the middle section and the end section.

[0027] The cross-sectional shapes of the middle section, the transition section, and the end section are smoothly transitioned and the wall thickness continuously increases. The cross-sectional shapes of the middle section and the transition section are both in the shape of "I", and the cross-sectional shape of the end section is in the shape of a "convex-like" "I". The width dimension of the bottom wall of the transition section is greater than the width dimensions of the middle section and the end section. The height dimension of the transition section is greater than the height dimensions of the middle section and the end section. The width dimension of the top wall of the transition section is less than the width dimensions of the middle section and the end section.

[0028] A sleeve is sleeved on the outer side wall of the transition section, and a solid fist head part is installed at the end of the end section far from the transition section.

[0029] The beneficial effects of the technical solution of the present application compared with the prior art are as follows:

[0030] Continuous control over the wall thickness and diameter of the metal tube is achieved through hammer forging and diameter reduction steps. Bending the reduced-diameter tube blank in a bending step controls the beam's orientation. A pre-forming step presets the beam's cross-sectional shape, and finally, a hot-air expansion forming step completes the beam's final shape. The specific cross-sectional shape of the beam can be controlled by the mold used for hot-air expansion. This allows for the production of beams with controllable wall thickness, cross-sectional shape, and extension shape. Compared to traditional processing methods involving roll forging, bending, pre-forging, and final forging, this optimizes the process flow. A sleeve step is used to install sleeves in the high-stress transition sections to increase strength at those points.

[0031] Hollow beam rotary forging equipment uses multiple punches to continuously hammer metal tubes axially. With the support of heating coils and mandrels, it can quickly complete the hammer forging and diameter reduction steps, thus improving efficiency.

[0032] The anti-collision beam produced by the aforementioned variable wall thickness hollow beam forming process has a wall thickness that increases progressively from the middle to both ends, ensuring both lightweight construction and structural strength. Furthermore, sleeves are fitted into the high-stress transition sections to increase strength at those points. The cross-sectional shape of the anti-collision beam transitions from an "I" shape in the middle to an "I" shape in the transition section, and finally to a "convex" shape at the ends, exhibiting high structural strength and facilitating forming through a hot air expansion process. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the hammer forging process;

[0035] Figure 2 This is a schematic diagram of the first type of metal tube blank structure;

[0036] Figure 3 This is a schematic diagram of the second type of metal tube blank structure;

[0037] Figure 4 This is a schematic diagram of the diameter reduction process;

[0038] Figure 5 A schematic diagram of a reduced-diameter tube blank with a sleeve attached;

[0039] Figure 6 This is a schematic diagram of an arched tube blank structure;

[0040] Figure 7 This is a schematic diagram of the bending process;

[0041] Figure 8 This is a schematic diagram of the bending process;

[0042] Figure 9 This is a front view of the preformed tube blank structure;

[0043] Figure 10 for Figure 9 Cross-sectional view at point AA;

[0044] Figure 11 for Figure 9 Cross-sectional view at point BB;

[0045] Figure 12 for Figure 9 Cross-sectional view at CC;

[0046] Figure 13 This is a schematic diagram of the preforming process;

[0047] Figure 14 This is a front view of the main beam structure.

[0048] Figure 15 This is a top view of the main beam structure;

[0049] Figure 16 for Figure 14 Cross-sectional view at point DD;

[0050] Figure 17 for Figure 14 Cross-sectional view at the EE section;

[0051] Figure 18 for Figure 14 Cross-sectional view at the middle FF section;

[0052] Figure 19 This is a schematic diagram of the thermal expansion process;

[0053] Figure 20 This is a schematic diagram of the anti-collision beam structure;

[0054] Figure 21 This is a front view of the hollow beam rotary forging equipment.

[0055] Figure 22 This is a top view of the hollow beam rotary forging equipment.

[0056] Figure 23 This is a schematic diagram of a punch forging process.

[0057] Figure 24 This is a schematic diagram of the punch structure.

[0058] Icons: 101. Metal tube; 102. Metal tube blank; 103. Reduced diameter tube blank; 104. Sleeve; 105. Arched tube blank; 106. Preformed tube blank; 107. Beam body; 108. Middle preformed section; 109. Transition preformed section; 110. End preformed section; 111. Middle section; 112. Transition section; 113. End section; 114. Solid fist section; 11. Stamping die; 12. Hot air expansion upper die; 13. Hot air expansion lower die; 14. Air source; 15. Air pipe; 16. Sealing pusher; 17. Hydraulic cylinder; 2. Mandrel; 201. Stamping section; 3 1. Forging device; 301. Punch; 302. Driven wheel; 303. Cam; 4. Tube clamping device; 401. First support seat; 402. First transfer motor; 403. Rotary motor; 404. First slide rail; 405. First rack; 406. First gear; 407. Material clamp; 408. First sliding seat; 5. Mandrel transfer device; 501. Second support seat; 502. Second transfer motor; 503. Three-jaw chuck; 504. Second slide rail; 505. Second rack; 506. Second gear; 507. Second sliding seat; 601. Heating coil. Detailed Implementation

[0059] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0060] It should be noted that when a component is referred to as being "fixed" or "set" to another component, it can be directly or indirectly attached to that other component. When a component is referred to as being "connected" to another component, it can be directly or indirectly connected to that other component.

[0061] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0062] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0063] Example 1:

[0064] This embodiment provides a forming process for hollow beams with variable wall thickness, used to produce hollow beams with variable cross-section and variable wall thickness, specifically the beam body 107 (attached) in a crash beam. Figure 14 (as shown), including:

[0065] S1, Forging Steps: Based on Figures 1 to 3 As shown, the metal tube 101 is heated to the forging temperature, and a mandrel 2 is inserted into the metal tube 101. The metal tube 101 is then forged circumferentially from the outside. Heating the metal tube 101 is done to ensure it reaches a suitable forging temperature. The inner wall of the metal tube 101 is supported by the mandrel 2, and the circumferential forging process continuously thins the wall thickness of the metal tube 101. The forging stroke decreases gradually from the middle to both ends of the metal tube 101; that is, the distance between the punch 301 and the outer wall of the mandrel 2 gradually increases during the forging process, forming a metal tube blank 102 with a continuously varying wall thickness along the axial direction. The wall thickness of the metal tube blank 102 gradually decreases from both ends to the middle. Due to the support of the mandrel 2, the axial fluctuation of the tube diameter of the metal tube 101 is not significant during the forging process.

[0066] In this embodiment, there are two ways to achieve the variation of the wall thickness of the metal tube 101. The first way is that the diameter of the mandrel 2 is the same at all points, and the distance between the punch 301 and the outer wall of the mandrel 2 is controlled by changing the distance the punch 301 moves, ultimately forming... Figure 2 The metal tube blank 102 shown has a uniform inner diameter but different outer diameters. The second method involves keeping the punch 301's movement distance constant while the mandrel 2's axial diameter continuously changes. By aligning the different diameters of the mandrel 2 with the punch 301, the distance between the punch 301 and the outer wall of the mandrel 2 is controlled, ultimately forming... Figure 3 The metal tube blank 102 shown has a uniform outer diameter but a different inner diameter.

[0067] In this embodiment, the metal tube 101 is made of Q550 material, and its forging temperature is 900°C, or any temperature between 800°C and 950°C, to achieve the optimal forging state.

[0068] S2, diameter reduction step: based on Figure 4 and Figure 5 As shown, the mandrel 2 is removed from the metal tube blank 102, and the metal tube 101 is heated again to the forging temperature. The metal tube blank 102 is forged circumferentially from the outside. At this time, since there is no mandrel 2 for support, the wall thickness of the metal tube blank 102 will not change drastically, but the outer diameter will change. The forging stroke increases sequentially from the middle to both ends of the metal tube blank 102, forming a reduced-diameter tube blank 103 whose outer diameter gradually decreases from the middle to both ends, and whose wall thickness gradually decreases from both ends to the middle.

[0069] S3, Casing step: Based on Figure 5 As shown, sleeves 104 are sleeved on both ends of the reduced-diameter tube blank 103, and the two sleeves 104 are symmetrically arranged on both sides of the reduced-diameter tube blank 103. The connection method between the sleeve 104 and the reduced-diameter tube blank 103 can be welding or bonding, and a reasonable selection is made according to different materials and actual requirements.

[0070] S4, Bending step: Based on Figure 6 As shown, the positions of the reduced-diameter tube blank 103 near both ends are bent to form an arched tube blank 105.

[0071] In this embodiment, the bending of the reduced-diameter tube blank 103 can adopt Figure 7 the press-bending process of pressing with a press brake as shown or Figure 8 the roll-bending process of bending with a tube bender as shown. For the press-bending process, the cross-sectional shape of the arched tube blank 105 will change to a certain extent after press-bending. However, since the cross-sectional shape of the arched tube blank 105 needs to be adjusted through the pre-forming and hot gas bulging steps later, the change in the cross-sectional shape of the arched tube blank 105 in the press-bending process does not affect the subsequent operations and the state of the finished product.

[0072] S5, Pre-forming step: Based on Figures 9 to 13 As shown, the arched tube blank 105 is stamped with a stamping die 11. By reasonably setting the shape of the die groove of the stamping die 11, a pre-formed tube blank 106 with a continuously changing cross-sectional shape from the middle to both ends is formed. The pre-formed tube blank 106 includes a middle pre-forming section 108, a transition pre-forming section 109, and an end pre-forming section 110 in sequence from the middle to both ends. The sleeve 104 is located in the transition pre-forming section 109, and the bending position of the pre-formed tube blank 106 is between the transition pre-forming section 109 and the end pre-forming section 110.

[0073] In this embodiment, for the automotive bumper beam, its cross-sectional shape can be set as follows: Based on Figure 10 [ As shown, the cross-section of the middle pre-forming section 108 is in the shape of a "work" character. Based on Figure 11 and Figure 12 As shown ( Figure 11 the sleeve 104 is omitted in

[0074] The middle preformed section 108, the transition preformed section 109, and the end preformed section 110 of the above shape are all symmetric about the left and right. The left half and the right half of the three are convenient for designing the stamping die 11, and can be formed by stamping with the die at one time. Through the preforming step, a preformed tube blank 106 with a cross-sectional shape close to the final product can be manufactured. The preforming step serves as a transition, facilitating the implementation of the subsequent hot gas expansion step. Otherwise, the cross-sectional shape of the product will change too much at one time during the hot gas expansion step and cause fracture.

[0075] In other embodiments, according to the different cross-sectional shapes of the final bumper beam, the cross-sectional shapes of the middle preformed section 108, the transition preformed section 109, and the end preformed section 110 can be reasonably set, specifically controlled by the shape of the die groove in the stamping die 11.

[0076] S6, hot gas expansion forming step: Based on Figure 14 and Figure 15 As shown, the preformed tube blank 106 is processed into the beam body 107 by using the hot gas expansion forming process. The middle preformed section 108 correspondingly forms the middle section 111, the transition preformed section 109 correspondingly forms the transition section 112, and the end preformed section 110 correspondingly forms the end section 113. The hot gas expansion forming process is an existing mature process. After heating the preformed tube blank 106, high-pressure inert gas is filled into the inside of the preformed tube blank 106 to make the preformed tube blank 106 expand and deform, and fit with the inner side of the hot gas expansion forming die to complete the forming of the beam body 107 in the final bumper beam.

[0077] In this embodiment, based on Figures 16 to 18 As shown, both the middle section 111 and the transition section 112 are in the shape of "I", the end section 113 is in a shape similar to "convex". The width dimension of the bottom wall of the transition section 112 is larger than the width dimensions of the middle section 111 and the end section 113. The width dimension of the top wall of the transition section 112 is smaller than the width dimensions of the middle section 111 and the end section 113. The height dimension of the transition section 112 is larger than the height dimensions of the middle section 111 and the end section 113.

[0078] For the beam body 107 actually used in automotive anti-collision beams, the middle section 111 experiences the least stress, while the transition section 112 experiences the greatest stress. Through the aforementioned forging step S1, and with the sleeve fitted onto the transition section 112, the overall wall thickness of the beam body 107 at the transition section 112 is greater than that of the middle section 111, and the bottom wall width of the transition section 112 is greater than the width of the middle section 111 and the end section 113, and the height of the transition section 112 is greater than the height of the middle section 111 and the end section 113, ensuring that the strength of the transition section 112 is greater than that of the middle section 111. Since the wall thickness of the middle section 111 is the thinnest, the weight per unit length of the middle section 111 is less than the weight per unit length of the transition section 112. Simultaneously, by setting the top wall width of the transition section 112 to be smaller than that of the middle section 111 and the end section 113, the top wall width of the transition section 112 is reduced while ensuring the strength of the bottom wall, achieving weight reduction while maintaining strength.

[0079] based on Figure 20 As described above, for the complete anti-collision beam, based on the main beam 107, solid fist-shaped sections 114 are connected to both ends. The ends of the fist-shaped sections are inserted into and fixedly connected to the end sections 113. Therefore, the end sections 113 are designed in a convex shape to facilitate the insertion and positioning of the fist-shaped sections. At the same time, the wall thickness of the end sections 113 is thicker than that of the middle sections 111 and the transition sections 112 to ensure connection strength.

[0080] based on Figure 19 As shown, the hot air expansion forming mold used in this embodiment includes a hot air expansion upper mold 12, a hot air expansion lower mold 13, an air source 14, an air pipe 15, a sealing pusher 16, and a hydraulic cylinder 17. In use, both ends of the preformed tube blank 106 are connected to the air source 14 via the sealing pusher 16 and the air pipe 15. The hydraulic cylinder 17 is connected to the sealing pusher 16 to open or close it. The preformed tube blank 106 is closed between the hot air expansion upper mold 12 and the hot air expansion lower mold 13. High-pressure inert gas is injected into the preformed tube blank 106 from both ends through the air source 14, or by closing one side of the sealing pusher 16 and injecting high-pressure inert gas only from the other side, causing the preformed tube blank 106 to expand and deform, fitting against the inner side of the hot air expansion forming mold, thus completing the forming of the final anti-collision beam body 107.

[0081] In this embodiment, the sleeve step can be located between the diameter reduction step and the bending step, or between the bending step and the preforming step, without affecting the connection of the sleeve 104 to the subsequent forming.

[0082] Example 2:

[0083] This embodiment provides a hollow beam rotary forging equipment for the hammer forging and diameter reduction steps in Embodiment 1, to produce a diameter reduction tube blank 103 with varying wall thickness and continuously varying outer diameter.

[0084] based on Figures 21 to 24 As shown, the device includes a forging apparatus 3, a tube clamping device 4, and a mandrel transfer device 5. The tube clamping device 4 and the mandrel transfer device 5 are located on both sides of the forging apparatus 3. The forging apparatus 3 includes a plurality of punches 301 arranged in a ring. The tube clamping device 4 includes a first support base 401 and a tube clamping mechanism. The tube clamping mechanism is slidably disposed on the first support base 401 along the arrangement direction of the tube clamping device 4, the forging apparatus 3, and the mandrel transfer device 5. The tube clamping mechanism has clamping components rotatably disposed on the side wall of the forging apparatus 3 for clamping the tube. In use, one end of the metal tube 101 or the metal tube blank 102 is clamped in the clamping components. The tube clamping mechanism slides on the first support base 401, allowing both to extend between the plurality of punches 301 arranged in a ring. The ring punches 301 hammer forge the metal tube 101 or the metal tube blank 102 from the circumference outwards. Simultaneously, as the pipe clamping mechanism slides on the first support 401, the punch 301 hammers the entire metal pipe 101 or metal blank 102 along the extension direction of the metal pipe 101 or metal blank 102. Since the clamping component is rotatably mounted on the pipe clamping mechanism, the metal pipe 101 or metal blank 102 can rotate axially, ensuring that both are opposite to the punch 301 in all circumferential directions.

[0085] In this embodiment, there are four punches 301, which are spaced 90 degrees apart. Of course, in other embodiments, the number of punches 301 can also be set to three or six, etc. The ring-shaped distribution of punches 301 can apply force evenly to the metal tube 101 or the metal tube blank 102, which can improve the forging efficiency and prevent the two or the mandrel 2 from deflecting or bending under the punching action of the punches 301.

[0086] The mandrel transfer device 5 includes a second support base 501 and a mandrel transfer mechanism. The mandrel transfer mechanism is slidably disposed on the second support base 501 along the arrangement direction of the tube clamping device 4, the forging device 3, and the mandrel transfer device 5. A mandrel 2 is mounted on the side wall of the mandrel transfer mechanism facing the forging device 3. The mandrel transfer mechanism slides on the second support base 501, causing the mandrel 2 to extend into or move out of the inner side of the annularly distributed punches 301. The clamping components, the arrangement center of the multiple punches 301, and the axis of the mandrel 2 coincide with each other. In the hammer forging step, both the metal tube 101 and the mandrel 2 extend into the interior of the annular punches 301, and the metal tube 101 is sleeved on the outside of the mandrel 2. Through the continuous hammer forging of the punches 301 and the rotation and axial movement of the metal tube 101 itself, combined with the supporting effect of the mandrel 2, the wall thickness of the metal tube 101 is continuously reduced. Simultaneously, the through-hole controls the minimum distance between the punch 301 and the outer wall of the mandrel 2, forming a metal tube blank 102 with a continuously varying wall thickness along the axial direction. During the diameter reduction step, the metal tube blank 102 is clamped in the clamping component, with only the metal tube blank 102 extending into the inside of the punch 301, while the mandrel 2 moves out of the annular punch 301. At this time, the punch 301 hammers the metal tube blank 102. Without the support of the mandrel 2, and in conjunction with the change in the stroke of the punch 301, a diameter-reduced tube blank 103 with a continuously varying outer diameter along the axial direction is formed. To prevent the portion of the metal tube 101 or metal tube blank 102 that is clamped by the clamping component from being unable to be hammered, both portions can be removed and flipped after partial forging, with the forged end clamped in the clamping component, and the other end extending to the punch 301 for further hammering.

[0087] Furthermore, based on Figure 21 and Figure 22 As shown, the pipe clamping mechanism includes a first sliding seat 408, a first transfer motor 402, and a rotary motor 403. Both the first transfer motor 402 and the rotary motor 403 are mounted on the first sliding seat 408. A first support base 401 is provided with a first slide rail 404 and a first rack 405 arranged parallel to the first slide rail 404. For stability during sliding, the number of first slide rails 404 can be two or more. The first sliding seat 408 is slidably disposed on the first slide rail 404. The first transfer motor 402 is driven by a first gear 406 meshing with the first rack 405. The transmission method between the first transfer motor 402 and the first gear 406 can be conventional transmission methods such as gear transmission, belt transmission, or chain transmission. The first transfer motor 402 drives the first gear 406 to move along the first rack 405, thus realizing the sliding of the pipe clamping mechanism along the first support base 401. The clamping component is a material clamp 407 driven by the rotary motor 403. The material clamp 407 is driven by the output shaft of the rotary motor 403 to achieve rotation. The transmission connection between the material clamp 407 and the rotary motor 403 can also adopt conventional transmission methods such as gear transmission, belt transmission or chain transmission.

[0088] Furthermore, based on Figure 21 and Figure 22 As shown, the mandrel transfer mechanism includes a second sliding seat 507, a second transfer motor 502, and a three-jaw chuck 503. Both the second transfer motor 502 and the three-jaw chuck 503 are mounted on the second sliding seat 507. The second support seat 501 is provided with a second slide rail 504 and a second rack 505 arranged parallel to the second slide rail 504. Similarly, for sliding stability, the number of second slide rails 504 can be set to two or more. The second sliding seat 507 is slidably disposed on the second slide rail 504, and the second transfer motor 502 is driven by a second gear 506 meshing with the second rack 505. The transmission method between the second transfer motor 502 and the second gear 506 can be conventional transmission methods such as gear drive, belt drive, or chain drive. The second transfer motor 502 drives the second gear 506 to move along the second rack 505, thus realizing the sliding of the mandrel transfer mechanism along the second support seat 501. The end of the mandrel 2 is clamped in the three-jaw chuck 503. When hammer forging the metal tube 101, the mandrel 2 is clamped on the three-jaw chuck 503. When hammer forging the metal tube blank 102, the mandrel 2 is removed from the three-jaw chuck 503. At the same time, depending on the diameter of the metal tube 101, different specifications of mandrel 2 can be replaced.

[0089] Furthermore, based on Figure 21 and Figure 22 As shown, a heating coil 601 is coaxially arranged between the clamping component and multiple punches 301. The metal tube 101 or metal blank 102 is first heated to the hammer forging temperature by extending into the heating coil 601 before extending to the punch 301 for hammer forging. This eliminates the need for preheating before clamping the metal tube 101 or metal blank 102 onto the clamping component, simplifying the process. Simultaneously, while the punch 301 is hammer forging, the heating coil 601 heats the subsequent unforged portions, improving processing efficiency. Furthermore, compared to heating the metal tube 101 or metal blank 102 as a whole before clamping it onto the clamping component, the hammer forging temperature at each location remains consistent, preventing temperature variations due to different forging times.

[0090] In the method of controlling the wall thickness of the metal tube 101 by changing the stroke of the punch 301 while keeping the diameter of the mandrel 2 constant, the punch 301 can be driven by a cylinder to reciprocate, and the stroke of the punch 301 is controlled by the moving distance of the cylinder end. Alternatively, based on Figure 24 As shown, a driven wheel 302 is provided at the end of the punch 301, and the driven wheel 302 is clamped between two cams 303. The rotation of the cams 303 drives the reciprocating motion of the punch 301. The stroke of the punch 301 is controlled by the rotation angle of the cams 303. A metal tube 101 is formed. Figure 2 The metal tube blank 102 shown has a uniform inner diameter.

[0091] based on Figure 1 As shown, with the stroke of the punch 301 remaining constant, the mandrel 2 achieves varying distances between the punch 301 and the outer wall of the mandrel 2 by aligning different diameters of the punch 301. The mandrel 2 has a tapered stamping section 201. During the hammer forging step, the mandrel 2 aligns the different diameter sections of the stamping section 201 with the punch 301 by axial movement. At this time, the punch 301 can be controlled to reciprocate via a reciprocating mechanism or cylinder, etc. A metal tube 101 is formed. Figure 3 The metal tube blank 102 shown has a uniform inner diameter. The large-diameter end of the stamping section 201 is positioned towards the tube clamping device 4, and the taper of the stamping section 201 facilitates material flow along the extension direction and intermittent cooling.

[0092] Example 3:

[0093] This embodiment provides a crash beam for use in the hammer forging and diameter reduction steps of Embodiment 1, achieving lightweight while ensuring strength.

[0094] In this embodiment, based on Figures 14-18 ,as well as Figure 20 As shown, the crash beam includes a hollow, closed beam body 107. The beam body 107 is arched and includes a middle section 111, a transition section 112, and an end section 113 arranged sequentially from the middle to both ends. The bending point of the beam body 107 is located between the middle section 111 and the end section 113. In actual use, the middle section 111 of the beam body 107 experiences the least stress, while the transition section 112 experiences the greatest stress. Therefore, it is necessary to reasonably set its wall thickness and cross-sectional shape to ensure strength.

[0095] Specifically, the cross-sectional shapes of the middle section 111, the transition section 112, and the end section 113 are smoothly transitioned and the wall thickness continuously increases. The cross-sectional shapes of both the middle section 111 and the transition section 112 are in the shape of a "worker" character, and the cross-sectional shape of the end section 113 is in the shape of a "convex" character. The width dimension of the bottom wall of the transition section 112 is greater than the width dimensions of the middle section 111 and the end section 113, and the height dimension of the transition section 112 is greater than the height dimensions of the middle section 111 and the end section 113, so as to ensure that the strength of the transition section 112 is greater than that of the middle section 111. Since the wall thickness of the middle section 111 is the thinnest, the weight of the middle section 111 per unit length is less than the weight of the transition section 112 per unit length, enabling the middle section 111 to achieve lightweight. The width dimension of the top wall of the transition section 112 is less than the width dimensions of the middle section 111 and the end section 113. The transition section 112 reduces the width dimension of the top wall while ensuring the strength of the bottom wall, achieving lightweight of the transition section 112 while ensuring the strength. A sleeve 104 is sleeved on the outer wall of the transition section 112 to further improve the strength of the transition section 112. A solid fist head 114 is installed at the end of the end section 113 away from the transition section 112. The solid fist head 114 can be connected to the end section 113 by means of welding, bonding, or bolt connection. The end section 113 is set in the shape of a "convex" character to facilitate the plug-in positioning of the fist head. At the same time, the wall thickness of the end section 113 is thicker than that of the middle section 111 and the transition section 112 to ensure the connection strength.

[0096] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A variable wall thickness hollow beam forming process, characterized by, include: Hammering steps: Heat the metal tube (101) to the hammering temperature, insert the mandrel (2) into the metal tube (101), and hammer forge the metal tube (101) circumferentially from the outside. The hammering stroke gradually decreases from the middle to both ends of the metal tube (101) to form a metal tube blank (102) with a continuously varying wall thickness along the axial direction. The wall thickness of the metal tube blank (102) gradually decreases from both ends to the middle. Reduction step: Take out the mandrel (2) from the metal tube blank (102), heat the metal tube blank (102) to the hammer forging temperature, and hammer forge the metal tube blank (102) circumferentially from the outside. The hammer forging stroke increases from the middle to both ends of the metal tube blank (102) to form a reduced diameter tube blank (103) with the outer diameter gradually decreasing from the middle to both ends. Sleeve installation steps: Sleeves (104) are attached to both ends of the reduced diameter tube blank (103), and the two sleeves (104) are symmetrically arranged on both sides of the reduced diameter tube blank (103). Bending steps: Bending the reduced diameter tube blank (103) near both ends to form an arched tube blank (105); Preforming step: The arched tube blank (105) is stamped using a stamping die to form a preformed tube blank (106) with a continuously changing cross-sectional shape from the middle to both ends; the preformed tube blank (106) consists of a middle preformed section (108), a transition preformed section (109) and an end preformed section (110) from the middle to both ends, with the sleeve (104) located in the transition preformed section (109) and the bending point of the preformed tube blank (106) located between the transition preformed section (109) and the end preformed section (110); Hot gas expansion forming step: The preformed tube blank (106) is processed into beam body (107) by hot gas expansion forming process, the middle preformed section (108) is formed into middle section (111), the transition preformed section (109) is formed into transition section (112), and the end preformed section (110) is formed into end section (113). In the preforming step, the cross-section of the middle preforming section (108) is "I" shaped, and the cross-sections of the transition preforming section (109) and the end preforming section (110) are "L". The bottom wall width of the transition preforming section (109) is greater than the bottom wall width of the end preforming section (110), and the height of the transition preforming section (109) is greater than the height of the end preforming section (110). In the hot gas expansion forming step, the middle section (111) and the transition section (112) are both in the shape of "I", and the end section (113) is in the shape of "convex". The bottom wall width of the transition section (112) is greater than the width of the middle section (111) and the end section (113). The top wall width of the transition section (112) is less than the width of the middle section (111) and the end section (113). The height of the transition section (112) is greater than the height of the middle section (111) and the end section (113).

2. The variable wall thickness hollow beam forming process of claim 1 wherein: In the sleeve step, the sleeve (104) and the reduced diameter tube blank (103) are connected by welding or bonding.

3. The variable wall thickness hollow beam forming process of claim 1 wherein: The metal tube (101) is made of Q550, and the hammer forging temperature range is 800℃ to 950℃.

4. The variable wall thickness hollow beam forming process of claim 1 wherein: In the bending step, the bending of the reduced diameter tube blank (103) is performed by press bending or rotary bending.

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