A welding structure and process for longitudinal beam of automobile body

Abstract

The present invention discloses a welding structure and process of a longitudinal beam of an automobile body, and relates to the field of automobile manufacturing technology. The present invention includes a main longitudinal beam, a secondary longitudinal beam, an internal reinforcement, an upper reinforcement and a side reinforcement; a first mounting seat is provided at the front end of the main longitudinal beam; a first baffle is provided on the outer side of the end of the main longitudinal beam; the secondary longitudinal beam is an unequal-depth "J" shape; the secondary longitudinal beam is plugged into the end of the longitudinal beam; the internal reinforcement is installed inside the main longitudinal beam, and a third baffle is provided on both sides of the front end of the internal reinforcement; the upper reinforcement is an L-shaped plate; the upper reinforcement is attached to the upper end face of the main longitudinal beam; there is a cavity between the upper reinforcement and the main longitudinal beam; a wedge-shaped buffer block is provided in the cavity. The present invention designs a spliced ​​vehicle longitudinal beam, utilizes the plug-in of the main longitudinal beam and the secondary longitudinal beam and the function of the internal wedge-shaped buffer block, and can absorb the collision energy by its own crushing deformation and bending deformation when the vehicle collides at high speed, and buffers the impact force generated during the collision, thereby effectively protecting the safety of passengers in the vehicle.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile manufacturing, and in particular relates to a welding structure and process of a longitudinal beam of an automobile body. Background Art

[0002] The frame is the most important load-bearing component in a car, and the frame longitudinal beam is one of the key parts. The rear longitudinal beam is an important supporting component of the car body load-bearing system, so the longitudinal beam plays an important load-bearing role in the car. The side beam frame, center beam frame, etc. of the car all contain longitudinal beams, which are usually stamped from low-alloy steel plates.

[0003] As the number of cars continues to increase, various traffic accidents are also emerging one after another, among which the incidence of rear-end collisions is relatively high. The longitudinal beams of cars play an extremely important role in rear-end collisions. However, most of the existing longitudinal beams are integrally formed. When the vehicle encounters a high-speed collision, it often cannot withstand the huge impact force generated by the collision, resulting in serious deformation and damage to the vehicle. In serious collisions, it brings hidden dangers to the safety of life and property of passengers in the car. Summary of the invention

[0004] The purpose of the present invention is to provide a welding structure and process for a longitudinal beam of an automobile body. By splicing the longitudinal beams, the longitudinal beams are used to absorb collision energy and buffer the impact force generated during the collision, thereby solving the problem that the existing longitudinal beams of vehicles cannot buffer the impact force of the collision and affect the safety of life and property of passengers in the vehicle.

[0005] To solve the above technical problems, the present invention is achieved through the following technical solutions:

[0006] The present invention is a longitudinal beam welding structure for an automobile body, comprising a main longitudinal beam, a secondary longitudinal beam, an internal reinforcement, an upper reinforcement and a side reinforcement.

[0007] The main longitudinal beam is a U-shaped channel steel; a first mounting seat is arranged at the front end of the main longitudinal beam, and the first mounting seat is used to fix the front engine compartment, and the front engine compartment is used to install the vehicle engine; a first baffle is arranged at the outer side of the end of the main longitudinal beam;

[0008] The secondary longitudinal beam is in the shape of a letter "X" with different depths; the secondary longitudinal beam is plugged into the end of the longitudinal beam; a second baffle plate cooperating with the first baffle plate is arranged on the outer side of the secondary longitudinal beam, and the main longitudinal beam and the secondary longitudinal beam are fixed by welding the first baffle plate and the second baffle plate;

[0009] The internal reinforcement is installed inside the main longitudinal beam, and third baffles are arranged on both sides of the front end of the internal reinforcement; the third baffle is welded inside the U-shaped channel steel;

[0010] The upper reinforcement is an L-shaped plate; the upper reinforcement is attached to the upper end surface of the main longitudinal beam; a second mounting seat is arranged in the middle of the upper reinforcement; a cavity is formed between the upper reinforcement and the main longitudinal beam; a wedge-shaped buffer block is arranged in the cavity; the wedge-shaped buffer block can play a certain buffering role when the vehicle is hit;

[0011] The side reinforcement is an L-shaped plate; the front half of the side reinforcement is attached to the upper reinforcement; and the rear half of the side reinforcement is attached to the secondary longitudinal beam.

[0012] Furthermore, a first punching hole is opened in the middle of the main longitudinal beam; waist-shaped reinforcement grooves are arranged on both sides of the first punching hole; and the first punching hole is used for wiring.

[0013] Furthermore, a reinforcement is movably installed inside the main longitudinal beam; the reinforcement is located at the front side of the internal reinforcement; the reinforcement is a plate body; bridges that cooperate with the waist-shaped reinforcement grooves are arranged on the left and right sides of the reinforcement; a first screw hole is opened on the bridge; a second punching hole corresponding to the first punching hole is opened in the middle of the reinforcement; first limiting plates are arranged on the upper and lower sides of the reinforcement; the reinforcement is clamped in the main longitudinal beam through the first limiting plate; because the first punching hole is opened on the main longitudinal beam, it is easy to bend or deform at the main first punching hole when the vehicle is hit, so the internal reinforcement is installed on the first punching hole to improve the toughness of the main longitudinal beam.

[0014] Furthermore, a mounting groove is also arranged at the upper end of the internal reinforcement member; the bottom surface of the mounting groove is arranged horizontally and a second screw hole is opened on the bottom surface of the groove.

[0015] Furthermore, a screw tube is provided on the top of the wedge-shaped buffer block; the lower end of the screw tube passes through the main longitudinal beam and is placed inside the main longitudinal beam; a spring sheet is provided on one side of the wedge-shaped buffer block; a groove is provided on one edge of the spring sheet; the spring sheet is clamped on the screw tube through the groove; a nut is rotatably installed in the screw tube; the nut passes through the second mounting seat, the screw tube and the second screw hole in sequence and is fixed by a nut to fix the main longitudinal beam, the wedge-shaped buffer block and the upper reinforcement, thereby facilitating welding.

[0016] Furthermore, a lower reinforcement piece is provided below the side reinforcement piece; a channel is formed between the side reinforcement piece, the lower reinforcement piece and the secondary longitudinal beam for wiring.

[0017] The present invention is a welding process for a longitudinal beam of an automobile body, comprising the following steps:

[0018] Step S1, material selection: selecting steel plates with thicknesses of 1.6 mm and 2 mm respectively;

[0019] Step S2, parts preparation: using a press working method to make a 1.6 mm thick steel plate into a main longitudinal beam, using a press working method to make a 2 mm thick steel plate into a secondary longitudinal beam, an internal reinforcement, an upper reinforcement and a side reinforcement;

[0020] Step S3, cleaning before welding: degreasing the surfaces of the manufactured main longitudinal beam, secondary longitudinal beam, internal reinforcement, upper reinforcement and side reinforcement;

[0021] Step S4: Parts clamping: clamp the internal reinforcement piece inside the main longitudinal beam, insert the secondary longitudinal beam from the rear of the main longitudinal beam until it contacts the internal reinforcement piece, place the reinforcement piece on top of the main longitudinal beam, then install the upper reinforcement piece and fix it with bolts, install the side reinforcement piece and the lower reinforcement piece in sequence according to the position relationship, and then clamp it on the welding fixture;

[0022] Step S5: Parts welding: The side reinforcement, the lower reinforcement, the main longitudinal beam and the secondary longitudinal beam are welded together by laser deep penetration welding. The entire welding process is carried out under argon protection. The main welding process parameters are as follows: maximum power 4.0kw, average output power 428.8w, minimum spot diameter 0.15mm, defocus 0mm, welding speed 4mm / s, pulse width 16ms, argon protection flow rate 17L / min;

[0023] Step S6: Post-welding inspection: Check the appearance quality of the longitudinal beam after welding, and test the strength, bending stiffness, torsional stiffness, and corrosion resistance of the longitudinal beam structure to eliminate defective welds.

[0024] Furthermore, in step S6, the test formulas for the strength, bending stiffness and torsional stiffness of the longitudinal beam structure are as follows:

[0025] ;

[0026] ;

[0027] In the formula, represents the decomposed tensile and compressive stresses in the horizontal and vertical directions, represents the decomposed bending stress in the horizontal and vertical directions, represents the decomposed torsional stress in the horizontal and vertical directions, represents the cross-sectional area in the horizontal and vertical directions, is the moment of inertia in the horizontal and vertical directions, is the polar moment of inertia, is an unknown constant, .

[0028] Furthermore, in step S6, it is necessary to perform equivalent stress judgment to eliminate defective welding products, and the specific judgment formula is as follows:

[0029] ;

[0030] In the formula, is the local maximum equivalent stress, is the ultimate stress of the material;

[0031] Substituting the strength, bending stiffness and torsional stiffness test formulas of the longitudinal beam structure into the equivalent stress judgment formula, we obtain:

[0032] .

[0033] The present invention has the following beneficial effects:

[0034] The present invention designs a vehicle longitudinal beam which is spliced ​​together, utilizes the insertion of the main longitudinal beam and the secondary longitudinal beam and the function of the internal wedge-shaped buffer block, and can absorb the collision energy through its own crushing deformation and bending deformation when a high-speed collision occurs in the vehicle, and buffer the impact force generated during the collision, thereby effectively protecting the safety of the passengers in the vehicle.

[0035] The present invention adopts steel plates of different thicknesses to weld automobile body longitudinal beams, wherein the front half is made of 1.6 mm steel plates and the rear half is made of 2 mm steel plates. Since the strengths of the front and rear automobile body longitudinal beams are different, when a high-speed collision occurs, the steel plates of the front part absorb energy and shrink to the limit, and the middle part of the automobile body longitudinal beam shrinks again to absorb energy, thereby reducing the buffering of the vehicle and ensuring the safety of the passengers in the vehicle.

[0036] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0038] Figure 1 This is a schematic diagram of a welding structure of a longitudinal beam of an automobile body;

[0039] Figure 2 for Figure 1 A front view of

[0040] Figure 3 The structural diagram of the main longitudinal beam;

[0041] Figure 4 It is a structural schematic diagram of the secondary longitudinal beam;

[0042] Figure 5 is a structural schematic diagram of the upper reinforcement member;

[0043] Figure 6 It is a structural schematic diagram of a wedge-shaped buffer block;

[0044] Figure 7 It is a schematic diagram of the structure of the internal reinforcement;

[0045] Figure 8 It is a schematic diagram of the structure of the side reinforcement member and the lower reinforcement member;

[0046] Fig. 9 is a structural schematic diagram of a reinforcement member;

[0047] In the figure: 1. main longitudinal beam; 2. secondary longitudinal beam; 3. internal reinforcement; 4. upper reinforcement; 5. side reinforcement; 6. wedge-shaped buffer block; 7. reinforcement; 8. lower reinforcement; 101. first mounting seat; 102. first baffle; 103. first punching hole; 104. waist-shaped reinforcement groove; 201. second baffle; 301. third baffle; 302. mounting groove; 303. second screw hole; 401. second mounting seat; 601. screw tube; 602. spring sheet; 701. bridge; 702. first screw hole; 703. second punching hole; 704. first limit plate. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] See also Figure 1-9 As shown, the present invention is a welding structure of a longitudinal beam of an automobile body, comprising a main longitudinal beam 1, a secondary longitudinal beam 2, an internal reinforcement 3, an upper reinforcement 4 and a side reinforcement 5.

[0050] The main longitudinal beam 1 is a U-shaped channel steel; a first mounting seat 101 is arranged at the front end of the main longitudinal beam 1, and the first mounting seat 101 is used to fix the front engine compartment, and the front engine compartment is used to install the vehicle engine; a first baffle 102 is arranged at the outer side of the end of the main longitudinal beam 1;

[0051] The secondary longitudinal beam 2 is in the shape of a letter "J" with different depths; the secondary longitudinal beam 2 is plugged into the end of the longitudinal beam 1; a second baffle plate 201 cooperating with the first baffle plate 102 is arranged on the outer side of the secondary longitudinal beam 2, and the main longitudinal beam 1 and the secondary longitudinal beam 2 are fixed by welding the first baffle plate 102 and the second baffle plate 201;

[0052] The internal reinforcement member 3 is installed inside the main longitudinal beam 1, and third baffles 301 are provided on both sides of the front end of the internal reinforcement member 3; the third baffles 301 are welded inside the U-shaped channel steel;

[0053] The upper reinforcement member 4 is an L-shaped plate; the upper reinforcement member 4 is attached to the upper end surface of the main longitudinal beam 1; a second mounting seat 401 is provided in the middle of the upper reinforcement member 4; a cavity is provided between the upper reinforcement member 4 and the main longitudinal beam 1; a wedge-shaped buffer block 6 is provided in the cavity; the wedge-shaped buffer block 6 can play a certain buffering role when the vehicle is hit;

[0054] The side reinforcement 5 is an L-shaped plate; the front half of the side reinforcement 5 is attached to the upper reinforcement 4; and the rear half of the side reinforcement 5 is attached to the secondary longitudinal beam 2.

[0055] A first punching hole 103 is opened in the middle of the main longitudinal beam 1; waist-shaped reinforcement grooves 104 are arranged on both sides of the first punching hole 103; and the first punching hole 103 is used for wiring.

[0056] A reinforcement member 7 is also movably installed inside the main longitudinal beam 1; the reinforcement member 7 is located on the front side of the internal reinforcement member 3; the reinforcement member 7 is a plate body; bridges 701 that cooperate with the waist-shaped reinforcement groove 104 are arranged on the left and right sides of the reinforcement member 7; a first screw hole 702 is opened on the bridge 701; a second punching hole 703 corresponding to the first punching hole 103 is opened in the middle of the reinforcement member 7; first limiting plates 704 are arranged on the upper and lower sides of the reinforcement member 7; the reinforcement member 7 is clamped in the main longitudinal beam 1 through the first limiting plate 704; because the first punching hole 103 is opened on the main longitudinal beam 1, when the vehicle is hit, it is easy to bend or deform at the main first punching hole 103, so the internal reinforcement member 3 is installed on the first punching hole 103 to improve the toughness of the main longitudinal beam 1.

[0057] A mounting groove 302 is further provided at the upper end of the internal reinforcement member 3 ; the bottom surface of the mounting groove 302 is horizontally arranged and a second screw hole 303 is opened on the bottom surface of the groove.

[0058] A screw tube 601 is provided on the top of the wedge-shaped buffer block 6; the lower end of the screw tube 601 passes through the main longitudinal beam 1 and is placed inside the main longitudinal beam 1; a spring sheet 602 is provided on one side of the wedge-shaped buffer block 6; a groove is provided on one edge of the spring sheet 602; the spring sheet 602 is clamped on the screw tube 601 through the groove; a nut is rotatably installed in the screw tube 601; the nut passes through the second mounting seat 401, the screw tube 601 and the second screw hole 303 in turn and is fixed by a nut, so as to fix the main longitudinal beam 1, the wedge-shaped buffer block 6 and the upper reinforcement 4 for easy welding.

[0059] A lower reinforcement member 8 is further provided below the side reinforcement member 5 ; a channel is formed between the side reinforcement member 5 , the lower reinforcement member 8 and the secondary longitudinal beam 2 for wiring.

[0060] The following is an analysis of the process. The material is a laser welded blank (TWB) of unequal thickness. The thick plate material is JAC780Y-45 / 45 with a thickness of 1.8mm, and the thin plate material is JAC590R-45 / 45 with a thickness of 1.6mm. Both materials belong to high yield strength ratio dual phase steel (DP steel) in AHSS. The projected size of the part is 841mm×212mm×214mm. The overall structure is in the shape of a "J" with unequal depths, a maximum depth of 82mm, and a minimum depth of 39mm. The forming depth difference is large, and the top and bottom radii are small, both R6mm, and the length and height directions are arc-shaped. Since the yield strength of JAC780Y-45 / 45 and JAC590R-45 / 45 materials is relatively high, and the uniform elongation is low, it is impossible to directly form the final shape of the longitudinal beam, and multiple forming processes are required, including the following steps:

[0061] Step S1, material selection: selecting steel plates with thicknesses of 1.6 mm and 2 mm respectively;

[0062] Step S2, parts preparation: using a press working method to make a 1.6 mm thick steel plate into a main longitudinal beam 1, using a 2 mm thick steel plate into a secondary longitudinal beam 2, an internal reinforcement 3, an upper reinforcement 4 and a side reinforcement 5;

[0063] Step S3, cleaning before welding: degreasing the surfaces of the manufactured main longitudinal beam 1, the secondary longitudinal beam 2, the internal reinforcement 3, the upper reinforcement 4 and the side reinforcement 5;

[0064] Step S4: Parts clamping: the internal reinforcement 3 is clamped inside the main longitudinal beam 1, the secondary longitudinal beam 2 is inserted from the rear of the main longitudinal beam 1 until it contacts the internal reinforcement 3, the reinforcement 7 is placed above the main longitudinal beam 1, and then the upper reinforcement 4 is installed and fixed by bolts, and the side reinforcement 5 and the lower reinforcement 8 are installed in sequence according to the position relationship, and then clamped on the welding fixture;

[0065] Step S5: Parts welding: The side reinforcement 5, the lower reinforcement 8, the main longitudinal beam 1 and the secondary longitudinal beam 2 are welded together by laser deep penetration welding. The entire welding process is carried out under argon protection. The main welding process parameters are as follows: maximum power 4.0kw, average output power 428.8w, minimum spot diameter 0.15mm, defocus 0mm, welding speed 4mm / s, pulse width 16ms, argon protection flow rate 17L / min;

[0066] Laser deep fusion welding is one of the methods of laser welding. When the laser power density reaches 10^6-10^7W / cm^2, the power input is much greater than the rate of heat conduction, convection and radiation heat dissipation, and the material surface vaporizes to form a small hole. The metal vapor pressure in the hole forms a dynamic balance with the static force and surface tension of the surrounding liquid, and the laser can pass through the hole directly to the bottom of the hole. This phenomenon is called the small hole effect. The role of the small hole is the same as that of a black body. It can completely absorb the incident laser energy and melt the metal surrounding the hole. The flow of the liquid outside the hole wall and the surface tension of the wall layer are in a dynamic balance with the steam pressure continuously generated in the hole cavity. The light beam carries a large amount of light energy and continuously enters the small hole, and the material outside the small hole is continuously flowing. As the light beam moves forward, the small hole is always in a stable state of flow. After the small hole moves forward with the leading light beam, the molten metal fills the cavity left after the small hole is removed and then condenses into a weld, completing the welding process. The whole process occurs very quickly, making it easy to reach a welding speed of several meters per minute.

[0067] Step S6: Post-welding inspection: Check the appearance quality of the longitudinal beam after welding, and test the strength, bending stiffness, torsional stiffness, and corrosion resistance of the longitudinal beam structure to eliminate defective welds.

[0068] In step S6, the strength, bending stiffness and torsional stiffness test formulas of the longitudinal beam structure are as follows:

[0069] ;

[0070] ;

[0071] In the formula, represents the decomposed tensile and compressive stresses in the horizontal and vertical directions, represents the decomposed bending stress in the horizontal and vertical directions, represents the decomposed torsional stress in the horizontal and vertical directions, represents the cross-sectional area in the horizontal and vertical directions, is the moment of inertia in the horizontal and vertical directions, is the polar moment of inertia, is an unknown constant, .

[0072] In step S6, it is necessary to perform equivalent stress judgment to eliminate defective welding products. The specific judgment formula is as follows:

[0073] ;

[0074] In the formula, is the local maximum equivalent stress, is the ultimate stress of the material;

[0075] Substituting the strength, bending stiffness and torsional stiffness test formulas of the longitudinal beam structure into the equivalent stress judgment formula, we obtain:

[0076] .

[0077] To ensure that the strength of the welded longitudinal beam is not less than that of the original vehicle longitudinal beam, the following conditions must be met:

[0078] ;

[0079] In the formula, is the local maximum equivalent stress of the original vehicle longitudinal beam, is the ultimate stress of the original vehicle longitudinal beam material.

[0080] Considering that the longitudinal beam is the most critical part of the frontal collision of the car, all improved designs must be based on the premise of not sacrificing its crash safety. Therefore, the crashworthiness analysis of the welded plate longitudinal beam must be carried out to verify the rationality of the design. According to the requirements of the national collision regulations CMVDR294, the vehicle is simulated to hit the rigid wall head-on at an initial speed of 50km / h. The simulation results such as the acceleration value of the lower end of the B-pillar, the crushing shape of key parts, and the dummy injury value are compared with the test results, and it is found that they are quite consistent. This proves the correctness of the constructed vehicle collision model and lays the foundation for the next step of lightweight and optimized design of the vehicle. Now, according to the parameters determined by the lightweight design of the longitudinal beam welded plate, the longitudinal beam grid model and material model are modified, and put into the vehicle finite element model for crash safety analysis. After many simulations, the constraint equations of the strength, bending stiffness and torsional stiffness of the body beam structure were established. On this basis, the size of the welded plate longitudinal beam was designed to meet the strength and stiffness design requirements, which reduced the weight of the longitudinal beam by 17.7%. The crash safety analysis of the longitudinal beam was also carried out to meet the crash resistance requirements of the longitudinal beam.

[0081] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0082] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A longitudinal beam welding structure for an automobile body, comprising a main longitudinal beam (1), a secondary longitudinal beam (2), an internal reinforcement member (3), an upper reinforcement member (4) and a side reinforcement member (5), characterized in that: The main longitudinal beam (1) is a U-shaped channel steel; a first mounting seat (101) is provided at the front end of the main longitudinal beam (1); a first baffle (102) is provided at the outer side of the end of the main longitudinal beam (1); The secondary longitudinal beam (2) is in the shape of an unequal depth "X"; the secondary longitudinal beam (2) is plugged into the end of the longitudinal beam (1); a second baffle plate (201) cooperating with the first baffle plate (102) is arranged on the outer side of the secondary longitudinal beam (2); The internal reinforcement member (3) is installed inside the main longitudinal beam (1), and third baffle plates (301) are provided on both sides of the front end of the internal reinforcement member (3); the third baffle plates (301) are welded inside the U-shaped channel steel; The upper reinforcement member (4) is an L-shaped plate; the upper reinforcement member (4) is attached to the upper end surface of the main longitudinal beam (1); a second mounting seat (401) is provided in the middle of the upper reinforcement member (4); a cavity is provided between the upper reinforcement member (4) and the main longitudinal beam (1); a wedge-shaped buffer block (6) is provided in the cavity; The side reinforcement (5) is an L-shaped plate; the front half of the side reinforcement (5) is attached to the upper reinforcement (4); the rear half of the side reinforcement (5) is attached to the secondary longitudinal beam (2); A first punched hole (103) is provided in the middle of the main longitudinal beam (1); waist-shaped reinforcement grooves (104) are provided on both sides of the first punched hole (103); A reinforcing member (7) is also movably installed inside the main longitudinal beam (1); the reinforcing member (7) is located at the front side of the internal reinforcing member (3); the reinforcing member (7) is a plate body; bridges (701) that cooperate with the waist-shaped reinforcing groove (104) are arranged on the left and right sides of the reinforcing member (7); a first screw hole (702) is provided on the bridge (701); a second punched hole (703) corresponding to the first punched hole (103) is provided in the middle of the reinforcing member (7); first limiting plates (704) are arranged on the upper and lower sides of the reinforcing member (7); the reinforcing member (7) is clamped inside the main longitudinal beam (1) through the first limiting plates (704); The upper end of the internal reinforcement member (3) is also provided with a mounting groove (302); the bottom surface of the mounting groove (302) is arranged horizontally and a second screw hole (303) is opened on the bottom surface of the groove; A screw tube (601) is provided at the top of the wedge-shaped buffer block (6); the lower end of the screw tube (601) passes through the main longitudinal beam (1) and is placed inside the main longitudinal beam (1); a spring sheet (602) is provided on one side of the wedge-shaped buffer block (6); a groove is provided on one side edge of the spring sheet (602); the spring sheet (602) is clamped on the screw tube (601) through the groove; a nut is rotatably installed in the screw tube (601); the nut passes through the second mounting seat (401), the screw tube (601) and the second screw hole (303) in sequence and is then fixed by a nut; A lower reinforcement member (8) is also provided below the side reinforcement member (5); a channel is formed between the side reinforcement member (5), the lower reinforcement member (8) and the secondary longitudinal beam (2) for wiring.

2. A welding process for a longitudinal beam of an automobile body, using a welding structure for a longitudinal beam of an automobile body as claimed in claim 1, characterized in that: The steps include: Step S1, material selection: selecting steel plates with thicknesses of 1.6 mm and 2 mm respectively; Step S2, parts preparation: using a press working method to make a 1.6 mm thick steel plate into a main longitudinal beam (1), using a press working method to make a 2 mm thick steel plate into a secondary longitudinal beam (2), an internal reinforcement (3), an upper reinforcement (4) and a side reinforcement (5); Step S3, cleaning before welding: degreasing the surfaces of the manufactured main longitudinal beam (1), the secondary longitudinal beam (2), the internal reinforcement (3), the upper reinforcement (4) and the side reinforcement (5); Step S4: Parts clamping: the internal reinforcement member (3) is clamped inside the main longitudinal beam (1), the secondary longitudinal beam (2) is inserted from the rear of the main longitudinal beam (1) until it contacts the internal reinforcement member (3), the reinforcement member (7) is placed above the main longitudinal beam (1), and then the upper reinforcement member (4) is installed and fixed by bolts, and the side reinforcement member (5) and the lower reinforcement member (8) are installed in sequence according to the position relationship, and then clamped on the welding fixture; Step S5: Parts welding: The side reinforcement (5), the lower reinforcement (8), the main longitudinal beam (1) and the secondary longitudinal beam (2) are welded together by laser deep penetration welding. The entire welding process is carried out under argon protection. The main welding process parameters are as follows: maximum power 4.0 kW, average output power 428.8 W, minimum spot diameter 0.15 mm, defocus 0 mm, welding speed 4 mm / s, pulse width 16 ms, argon protection flow rate 17 L / min; Step S6: Post-welding inspection: Check the appearance quality of the longitudinal beam after welding, and test the strength, bending stiffness, torsional stiffness, and corrosion resistance of the longitudinal beam structure to eliminate defective welds.

3. The automobile body longitudinal beam welding process according to claim 2, characterized in that: In step S6, the strength, bending stiffness and torsional stiffness test formulas of the longitudinal beam structure are as follows: In the formula, represents the decomposed tensile and compressive stresses in the horizontal and vertical directions, represents the decomposed bending stress in the horizontal and vertical directions, represents the decomposed torsional stress in the horizontal and vertical directions, represents the cross-sectional area in the horizontal and vertical directions, is the moment of inertia in the horizontal and vertical directions, is the polar moment of inertia, is an unknown constant, .

4. The automobile body longitudinal beam welding process according to claim 3, characterized in that: In step S6, it is necessary to perform equivalent stress judgment to eliminate defective welding products. The specific judgment formula is as follows: In the formula, is the local maximum equivalent stress, is the ultimate stress of the material; Substituting the strength, bending stiffness and torsional stiffness test formulas of the longitudinal beam structure into the equivalent stress judgment formula, we obtain: 。

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