Welding-seam-free carriage bottom plate production process based on extrusion welding

Abstract

The invention relates to a weldless carriage bottom plate production process based on extrusion welding, and belongs to the technical field of extrusion welding, an aluminum alloy coiled material is firstly subjected to multi-pass rolling forming, wrinkling and cracking caused by one-time large deformation are avoided, a precision foundation is laid for follow-up triangular groove forming, then extrusion is conducted through a roller with a triangular cavity, and the weldless carriage bottom plate is obtained. Compared with a rectangular groove, the weldless compartment bottom plate solves the problems that lateral pressure resistance is weak and stress is easy to concentrate when a forklift forks, the pressure resistance is enhanced, a transition angle is formed in the third-pass sharp-corner finish roll extrusion forming process, the sharp-corner cracking risk is eliminated, and the service life of the compartment bottom plate is prolonged. The forking deformation resistance of the forklift is further improved; the top of the triangular groove is welded through laser welding, the problems that traditional welding has many defects and is low in strength are solved, defects such as air holes in a welding seam are reduced or closed through rolling operation after laser welding, residual stress is released, and the compactness of the welding seam is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of extrusion welding, and relates to a production process of a weldless carriage floor based on extrusion welding. BACKGROUND

[0002] In the field of transportation equipment manufacturing, the carriage floor is a core structural component directly in contact with goods and bearing all loads, and its performance runs through the whole life cycle of the vehicle, from static stacking and bearing in daily logistics transportation, to dynamic fatigue resistance in vehicle driving and jolting, to weather resistance and corrosion resistance in outdoor storage, each performance is directly related to the safety of goods transportation and the service life of the vehicle. Especially in high-frequency heavy-load scenarios such as commercial vehicles, logistics heavy trucks, and cold chain transport vehicles, the carriage floor needs to bear a uniform load of 500-1500 kg / m 2 for a long time, and resist rain erosion, high and low temperature alternation, and complex working conditions such as goods friction and impact. Its mechanical properties (tensile strength, bending stiffness, fatigue resistance), weather resistance (corrosion resistance, ultraviolet aging resistance), and structural integrity (no cracks, no splicing gap) have become the core indicators for measuring the quality of vehicle manufacturing.

[0003] The mainstream production process of the carriage floor in the industry always takes "segmented splicing plus traditional welding" as the core mode. The technical path of this process has clear stage characteristics: first, according to the overall size of the carriage, the metal plate (low-carbon steel plate, aluminum alloy plate) in roll form is cut into preset size rectangular unit pieces by a numerical control shearing machine and a laser cutting machine; second, the unit pieces are precisely positioned on the welding platform through a fixture to ensure that the splicing gap is controlled within a certain range; finally, traditional welding methods such as electric arc welding and carbon dioxide gas shielded welding are used to continuously weld along the splicing joint of the unit piece to form a complete carriage floor.

[0004] In order to facilitate the forklift to pick up, the bottom of the rectangular unit piece is usually provided with a concave-convex structure in the form of an equidistant rectangular groove, and its rigidity mainly depends on the "vertical support" of the groove side wall. However, this shape has low stability and is easily impacted by horizontal impact or lateral force when the forklift is picked up, resulting in deformation. SUMMARY

[0005] The purpose of the present application is to provide a production process of a weldless carriage floor based on extrusion welding, which can improve the mechanical strength and avoid side deformation when the forklift picks up through processes such as roll forming, extrusion forming, laser welding, and heat treatment.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] A production process of a weldless carriage floor based on extrusion welding, comprising the following steps:

[0008] Step one: roll the unwound aluminum alloy coil into a concave-convex plate with a rectangular groove at the bottom, and then adjust the inclination angle of the side wall of the rectangular groove through three extrusion forming processes after removing impurities on the surface to obtain a concave-convex plate with a triangular groove at the bottom.

[0009] Step two: weld the top gap of the triangular groove through a laser welding process, immediately roll after welding, and then laser remelt to obtain a weld-free plate, and then perform heat treatment to obtain a weld-free carriage bottom plate.

[0010] Further, the three extrusion forming processes include first pass pre-extrusion forming, second pass angle correction extrusion forming, and third pass sharp angle fine extrusion forming.

[0011] Further, the roller two side angles of the first pass pre-extrusion forming are 90° to 120℃ gradual inclined surface, the roller pressure is 15-20kN, and the speed is 60-80mm / s.

[0012] Further, the roller side angle of the second pass angle correction extrusion forming is 105°, and the roller pressure is the same as the first pass pre-extrusion forming.

[0013] Further, the inverted cone roller of the third pass sharp angle fine extrusion forming has an arc transition angle, the transition angle arc is 1.0mm, and the roller pressure is the same as the first pass pre-extrusion forming.

[0014] Further, the distance between two adjacent triangular grooves is 102mm, the depth is 21mm, and the bottom width is 20mm.

[0015] Further, the forming pass of roll forming is 8-10 passes, the bending angle increment is 30°-35° for the first pass, and the subsequent passes decrease to 8°-12°, the friction coefficient is 0.1-0.15, the forming speed is 150-200mm / s, the roller station spacing is 280-320mm, the roller gap height is 0.7-1.1mm, and the bending radius is ≥1.5mm.

[0016] Further, the parameters of the laser welding process are that the laser power is 500-800W and the temperature is 150-200 during preheating, the welding head is inclined 15°-20° during welding, the welding speed is 100-120mm / s, the laser power is 5000-5200W, and the ratio of central power to annular power is 7:3.

[0017] Further, the welding atmosphere of the laser welding process is one of argon and nitrogen.

[0018] Further, the pressure of roll forming is 8-12kN, and the speed is 110-120mm / s.

[0019] Further, the parameters of the remelting are as follows: the laser power is 3000-3500W, the scanning speed is 80-100mm / s, and the remelting depth is 0.3-0.5mm.

[0020] Further, the preparation process of the weldless carriage floor is as follows:

[0021] Nitrogen is introduced into the heat treatment furnace, and the temperature is raised to 520-540℃ and kept for 30-40min, the weldless plate is put into the heat treatment furnace, and kept for 1-2h, and quenched to obtain the weldless carriage floor.

[0022] Further, the heating rate of the heat treatment furnace is 8-12℃.

[0023] Further, the water temperature during quenching is 80-85℃.

[0024] The beneficial effects of the present application are:

[0025] 1、The present application first multi-pass roll forming of aluminum alloy coiled material, to avoid the wrinkle, cracking caused by one-time large deformation, for the subsequent formation of triangular groove laid the precision foundation, and then through the roller extrusion with triangular cavity, form equidistant triangular groove, compared with rectangular groove, this weldless carriage floor solves the problem of weak resistance to lateral pressure and stress concentration when the forklift forks, the compressive strength is enhanced, and the transition angle is formed in the process of the third pass sharp corner precision extrusion, eliminating the risk of sharp corner cracking, further improving the ability to resist forklift fork deformation.

[0026] The top of the triangular groove is welded by laser welding, solving the problems of many traditional welding defects and low strength, and through the rolling operation after laser welding, reducing or closing the pores and other defects in the weld, releasing residual stress, improving the density of the weld, and further eliminating the micro defects, making the weld surface more smooth, reducing stress concentration, improving the mechanical properties of the weld, realizing the effect of no weld, and improving the tensile strength of the weld through heat treatment.

[0027] 2、The present application first removes the oxide film on the surface of the aluminum alloy, then laser welding is performed on the top of the triangular groove, the inclined surface structure of the triangular groove can disperse the heat input during welding and avoid local overheating, a certain time of preheating is performed before laser welding to reduce the temperature difference of the welding area and make the heat distribution uniform, the argon gas sprayed by the double nozzles ensures that the weld is penetrated and has no pores, the tensile strength is improved, the laser welding is immediately rolled after the laser welding to reduce or eliminate the tiny pores, and the weld is made smoother through laser remelting, and then heat treatment is performed to eliminate the residual heat affected zone after welding, the high temperature makes the coarse grains in the heat affected zone recrystallize into fine grains, avoids the risk of cracking, avoids the strength attenuation caused by the precipitation of strengthening phase, and makes the mechanical strength of the weldless carriage floor after forming higher. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the weldless carriage floor of the present application.

[0029] Figure 2 It is a schematic diagram of the position relationship between the inverted cone roller and the concave-convex plate.

[0030] Figure 3 It is a structural schematic diagram of the concave-convex plate with a rectangular groove at the bottom.

[0031] 1. Inverted cone roller. DETAILED DESCRIPTION

[0032] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the specific embodiments, features and effects according to the present application are described in detail as follows in combination with the preferred embodiments.

[0033] Embodiment 1: The present embodiment provides a weldless carriage floor production process based on extrusion welding, including the following steps:

[0034] S1: The aluminum alloy coiled material with a thickness of 0.8mm and a width of 1380mm is opened by the uncoiler, and is formed by rolling, the forming pass of the rolling forming is 8 passes, the bending angle increment is 30° for the first pass, and is decreased to 8° for the subsequent passes, the friction coefficient is 0.1, the forming speed is 150mm / s, the roller station spacing is 280mm, the roller gap height is 0.7mm, the bending radius is ≥1.5mm, and shearing is performed to obtain a concave-convex plate with a rectangular groove at the bottom (see Figure 3 ).

[0035] S2: Clean the rectangular groove surface of the concave-convex plate with a rectangular groove at the bottom of impurities, mark the center line of the rectangular groove and the boundary of the two side walls by laser positioning instrument, and extrude by three extrusion molding processes. The pressure of the three extrusion molding processes is 15 kN. The first pass of the three extrusion molding processes is pre-extrusion molding at a speed of 60 mm / s through a roller with a triangular cavity. The two side angles of the first pass pre-extrusion molding roller are 90° to 120° gradual inclined surface, forming a preliminary profile. The second pass angle correction extrusion molding is performed. The roller side angle of the second pass angle correction extrusion molding is 105°. The third pass sharp angle fine roller extrusion molding is performed. The inverted cone roller of the third pass sharp angle fine roller extrusion molding has an arc transition angle. The transition angle arc is 1 mm (see Figure 2 ).

[0036] S3: Soak the concave-convex plate with a triangular groove at the bottom in a 10wt% NaOH solution for 5 minutes, remove the oxide film, rinse with deionized water and dry. Preheat the triangular groove area of the concave-convex plate with a triangular groove at the bottom before welding by auxiliary laser. The laser power is 500 W and the temperature is 150℃ during preheating. Then use a CFX-8000 type continuous fiber laser to perform laser welding. Welding is performed at the top gap of the triangular groove. The welding joint is inclined at an angle of 15°. The welding speed is 100 mm / s. The laser power is 5000 W. A closed gas curtain is formed by spraying argon gas through double nozzles (the main nozzle blows vertically to the weld, with a flow rate of 20 L / min; the auxiliary nozzle is inclined at an angle of 30° along the two sides of the groove, with a flow rate of 10 L / min). The ratio of central power to annular power is 7:3. After welding, immediately roll using the same roller device as the third pass sharp angle fine roller extrusion molding. The pressure of the pair of inverted cone rollers in the horizontal direction during rolling is 8 kN, and the speed is 100 mm / s. Then use a CFX-8000 type continuous fiber laser to perform remelting. The remelting parameters are set as follows: laser power 3000 W, scanning speed 80 mm / s, remelting depth 0.3 mm, and protective gas argon. A weld-free plate is obtained (see Figure 1 ).

[0037] S4: Replace the air in the furnace with nitrogen gas, then heat to 520℃ at a rate of 8℃ / min, and keep for 30 min. Put the weld-free plate into the heat treatment furnace and keep for 1 h. Take out the weld-free plate and immerse it in 80℃ water within 5 s for quenching treatment, and continuously stir the water body. Take out, wipe the surface with a 1wt% nitric acid solution, wash with deionized water, and dry to obtain a weld-free carriage bottom plate.

[0038] Embodiment 2: The present embodiment provides a welding seam-free carriage floor production process based on extrusion welding, comprising the following steps:

[0039] S1: The aluminum alloy coil with a thickness of 1.0 mm and a width of 1380 mm is unwound by an uncoiler, and is formed by rolling with 9 passes, the bending angle increment is 32° for the first pass and decreases to 10° for the subsequent passes, the friction coefficient is 0.12, the forming speed is 175 mm / s, the roller station spacing is 300 mm, the roller gap height is 0.9 mm, the bending radius is ≥1.5 mm, and shearing is performed to obtain a concave-convex plate with a rectangular groove at the bottom.

[0040] S2: The rectangular groove surface of the concave-convex plate with a rectangular groove at the bottom is cleaned of impurities, the center line of the rectangular groove and the boundary of the two side walls are marked by a laser positioning instrument, and the plate is extrusion formed by a three-time extrusion forming process, the pressure of the three-time extrusion forming process is 17 kN, the first-time pre-extrusion forming is performed at a speed of 70 mm / s by a roller with a triangular cavity, the two side angles of the first-time pre-extrusion forming roller are a gradual inclined surface with an angle of 90° to 120°, forming a preliminary profile, the second-time angle correction extrusion forming is performed, the side angle of the roller for the second-time angle correction extrusion forming is 105°, the third-time sharp angle precision roller extrusion forming is performed, the inverted cone roller for the third-time sharp angle precision roller extrusion forming has an arc transition angle, the transition angle arc is 1 mm, the distance between adjacent two triangular grooves is 102 mm, the triangular groove depth is 21 mm, and the triangular groove bottom width is 20 mm, to obtain a concave-convex plate with a triangular groove at the bottom.

[0041] S3: The concave-convex plate with a triangular bottom groove is immersed in a 10wt% NaOH solution for 7 minutes to remove the oxide film, washed with deionized water and dried, the triangular groove area of the concave-convex plate with a triangular bottom groove before welding is preheated by auxiliary laser, the laser power is 650W and the temperature is 175℃ during preheating, then laser welding is performed using a CFX-8000 type continuous fiber laser, welding is performed at the top gap of the triangular groove, the welding head is inclined at an angle of 17°, the welding speed is 110mm / s, the laser power is 5100W, a closed gas curtain is formed by spraying argon gas through double nozzles (the main nozzle blows vertically to the weld, the flow rate is 20L / min; the auxiliary nozzle is inclined at an angle of 30° along the two sides of the groove, the flow rate is 10L / min), the ratio of central power to annular power is 7:3, after welding, the same roller pressing device as the third pass sharp corner precision roller extrusion forming is used for immediate roller pressing, the pressure of a pair of inverted cone rollers in the horizontal direction during roller pressing is 10kN, the speed is 110mm / s, then remelting is performed using a CFX-8000 type continuous fiber laser, the remelting parameters are set as laser power 3300W, scanning speed 90mm / s, remelting depth 0.4mm, and the protective gas is argon, to obtain a weldless plate.

[0042] S4: Nitrogen is introduced into a heat treatment furnace (equipment model GWL-1200XB) to replace the air in the furnace, then the temperature is raised to 530℃ at a rate of 10℃, and the temperature is maintained for 35 minutes, the weldless plate is placed in the heat treatment furnace, the temperature is maintained for 1.5h, the weldless plate is taken out and immersed in 82℃ water within 6s, quenching treatment is performed, and the water body is continuously stirred, then the weldless plate is taken out, the surface is wiped with a 1wt% nitric acid solution, washed with deionized water, and dried, to obtain a weldless carriage bottom plate.

[0043] Example 3: The present embodiment provides a weldless carriage bottom plate production process based on extrusion welding, comprising the following steps:

[0044] S1: The aluminum alloy coiled material with a thickness of 1.2mm and a width of 1380mm is unwound by an uncoiler, and is roller formed, the forming passes of roller forming are 10 passes, the bending angle increment is 35° for the first pass and decreases to 12° for the subsequent passes, the friction coefficient is 0.15, the forming speed is 200mm / s, the roller station spacing is 320mm, the roller gap height is 1.1mm, the bending radius is ≥1.5mm, and shearing is performed, to obtain a concave-convex plate with a rectangular bottom groove.

[0045] S2: Clean the rectangular groove surface of the concave-convex plate with a rectangular groove at the bottom of impurities, mark the center line of the rectangular groove and the boundary of the two side walls by a laser positioning instrument, and extrude by a three-time extrusion molding process. The pressure of the three-time extrusion molding process is 20 kN. The three-time extrusion molding process first passes through a roller with a triangular cavity at a speed of 80 mm / s to perform first-time pre-extrusion molding. The two side angles of the roller of the first-time pre-extrusion molding are a gradual inclined surface with an angle of 90° to 120°. A preliminary profile is formed. Second-time angle correction extrusion molding is then performed. The roller side angle of the second-time angle correction extrusion molding is 105°. Third-time sharp angle fine roller extrusion molding is then performed. The inverted cone roller of the third-time sharp angle fine roller extrusion molding has an arc transition angle. The transition angle arc is 1 mm. The distance between two adjacent triangular grooves is 102 mm. The triangular groove depth is 21 mm. The triangular groove bottom width is 20 mm. A concave-convex plate with a triangular groove at the bottom is obtained.

[0046] S3: The concave-convex plate with a triangular groove at the bottom is soaked in a 10wt% NaOH solution for 10 min to remove the oxide film. The concave-convex plate with a triangular groove at the bottom is preheated by auxiliary laser before welding. The triangular groove area of the concave-convex plate with a triangular groove at the bottom is preheated by auxiliary laser before welding. The laser power is 800 W and the temperature is 200℃. Then, a CFX-8000 type continuous fiber laser is used for laser welding. The welding is performed at the top gap of the triangular groove. The welding head is inclined by 20°. The welding speed is 120 mm / s. The laser power is 5200 W. A closed gas curtain is formed by spraying argon with a double nozzle (the main nozzle is perpendicular to the weld, with a flow rate of 20 L / min; the auxiliary nozzle is inclined by 30° along the two sides of the groove, with a flow rate of 10 L / min). The ratio of central power to annular power is 7:3. After welding, the same roller pressing device as the third-time sharp angle fine roller extrusion molding is used for roller pressing immediately. The pressure of the pair of inverted cone rollers in the horizontal direction is 12 kN, and the speed is 120 mm / s. Then, a CFX-8000 type continuous fiber laser is used for remelting. The remelting parameters are set as follows: laser power 3500 W, scanning speed 100 mm / s, remelting depth 0.5 mm, and protective gas argon. A weld-free plate is obtained.

[0047] S4: Nitrogen is introduced into a heat treatment furnace (equipment model GWL-1200XB) to replace the air in the furnace. The temperature is raised to 540℃ at a rate of 12℃ / min, and the temperature is maintained for 40 min. The weld-free plate is placed in the heat treatment furnace and maintained for 2 h. The weld-free plate is taken out and immersed in 85℃ water within 7 s for quenching treatment. The water body is continuously stirred. The weld-free plate is taken out, the surface is wiped with a 1wt% nitric acid solution, washed with deionized water, and dried. A weld-free carriage bottom plate is obtained.

[0048] Example 4: This example provides a production process of a seam-free carriage floor based on extrusion welding, which is different from Comparative Example 1 in that no laser positioner is used for positioning in step S2.

[0049] Example 5: This example provides a production process of a seam-free carriage floor based on extrusion welding, which is different from Comparative Example 1 in that argon is replaced by nitrogen in step S3.

[0050] Example 6: This example provides a production process of a seam-free carriage floor based on extrusion welding, which is different from Comparative Example 1 in that the oxide film is not removed in step S3.

[0051] Comparative Example 1: This comparative example provides a production process of a seam-free carriage floor based on extrusion welding, which is different from Comparative Example 1 in that no steps S2, S3, and S4 are performed, and the concave-convex plate with a rectangular groove at the bottom prepared in step S1 is the seam-free carriage floor.

[0052] Comparative Example 2: This comparative example provides a production process of a seam-free carriage floor based on extrusion welding, which is different from Comparative Example 1 in that the third pass sharp corner fine rolling extrusion forming is not performed in step S2, and a concave-convex plate with a triangular groove at the bottom is obtained.

[0053] Comparative Example 3: This comparative example provides a production process of a seam-free carriage floor based on extrusion welding, which is different from Comparative Example 1 in that no rolling and laser remelting are performed in step S3, and no step S4 is performed, and the seam-free plate prepared in step S3 is the seam-free carriage floor.

[0054] The seam-free carriage floors prepared in Examples 1-6 and Comparative Examples 1-3 are tested for performance:

[0055] Mechanical property test:

[0056] (1) Microhardness test: KB30S full-automatic Vickers hardness tester is used for microhardness test, and the test area includes the entire welding joint. The load used during the test is 100g, and the loading time is 15s. To avoid the randomness during the hardness test, the hardness test is performed on the upper, middle, and lower regions of the welding joint, and then the average value is taken to ensure the reliability of the data. The microhardness test takes the center point of the weld as the test center, and the adjacent test points are spaced 0.2mm apart.

[0057] (2) Tensile test: ISO4136 standard is used, and CMT5202 electronic universal testing machine is used for testing. The original gauge length is marked before the test, and the tensile rate is set to 2mm / min. The tensile strength and the elongation after fracture are obtained after the test.

[0058] (3) Impact test: refer to the standards GB / T2650-2008 “Welded joint impact test method” and GB / T229-2020 “Metal material Charpy pendulum impact test method”. V-shaped notch is selected, the center of the weld is selected as the slotting position, and the impact test is completed by using SANS metal pendulum impact testing machine. In order to avoid the contingency in the test process and reduce the error, the welded joint under each state is tested three times, and the average value of the impact energy is taken for comparison.

[0059] The test results are shown in the following table:

[0060] Table 1 Performance test list

[0061] Item Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Microhardness (HV) 61.5 61.7 62.1 60.9 61.9 61.3 52.3 60.3 53.5 Tensile strength (MPa) 263.9 265.1 266.5 264.9 265.1 264.5 178.3 235.3 197.2 Elongation at break (%) 11.2 11.5 12.1 11.8 11.2 11.5 8.5 11.3 10.2 Impact energy (J) 6.1 6.5 6.9 6.1 6.8 6.6 3.2 4.2 5.5

[0062] As can be seen from Table 1, the mechanical strength in Examples 1-6 is greater than that in Comparative Examples 1-3, which may be because a transition angle is formed in the process of third-pass sharp-angle fine roller extrusion forming, the risk of sharp-angle cracking is eliminated, after laser welding, the defects such as pores in the weld are reduced or closed, the residual stress is released, the density of the weld is improved, and then through laser remelting, the micro defects are further eliminated, and after heat treatment, the heat-affected zone remaining after welding is eliminated, the coarse grains in the heat-affected zone are recrystallized into fine grains at high temperature, the risk of cracking is avoided, the strength attenuation caused by the precipitation of strengthening phase is avoided, and the mechanical strength of the non-welded carriage floor after forming is higher.

[0063] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of the present application. Any modification, equivalent change and modification of the above embodiments made according to the technical essence of the present application, without departing from the technical solution of the present application, are still within the scope of the technical solution of the present application.

Claims

1. A process for producing a weldless carriage floor based on extrusion welding, characterized in that, It comprises the following steps: Step one: roll the unwound aluminum alloy coil into a concave-convex plate with a rectangular groove at the bottom, adjust the inclination angle of the rectangular groove sidewall through three extrusion forming processes after surface impurity removal, and obtain a concave-convex plate with a triangular groove at the bottom; Step two: weld the top gap of the triangular groove through a laser welding process, immediately roll after welding, laser remelting, obtain a weld-free plate, and then heat treatment to obtain a weld-free carriage bottom plate.

2. A process for producing a weld seam free vehicle body floor based on extrusion welding according to claim 1, characterized in that The three extrusion forming processes in step one include first pass pre-extrusion forming, second pass angle correction extrusion forming, and third pass sharp angle fine extrusion forming.

3. A process for producing a weld seam free vehicle body floor based on extrusion welding according to claim 2, characterized in that The roller two side angles of the first pass pre-extrusion forming are 90° to 120℃ gradual inclined surface, the roller pressure is 15-20kN, and the speed is 60-80mm / s.

4. A process for producing a weld seam free vehicle body floor based on extrusion welding according to claim 2, characterized in that The roller side angle of the second pass angle correction extrusion forming is 105°, and the roller pressure is the same as the first pass pre-extrusion forming.

5. A process for producing a weld seam free truck bed floor based on extrusion welding according to claim 2, characterized in that The inverted cone roller of the third pass sharp angle fine extrusion forming has an arc transition angle, the transition angle arc is 1.0mm, and the roller pressure is the same as the first pass pre-extrusion forming.

6. A process for producing a weld seam free truck bed floor based on extrusion welding according to claim 1, characterized in that The forming pass of the roll forming is 8-10 passes, the bending angle increment is 30°-35° for the first pass, and decreases to 8°-12° for the subsequent passes, the friction coefficient is 0.1-0.15, the forming speed is 150-200mm / s, the roller station spacing is 280-320mm, the roller gap height is 0.7-1.1mm, and the bending radius is ≥1.5mm.

7. The process for producing a weld seam free truck bed floor based on extrusion welding according to claim 1, characterized in that The parameters of the laser welding process in step two are: the laser power is 500-800W during preheating, the temperature is 150-200, the welding head is inclined 15°-20° during welding, the welding speed is 100-120mm / s, the laser power is 5000-5200W, and the ratio of central power to ring power is 7:3; The welding atmosphere of the laser welding process is one of argon and nitrogen.

8. A process for producing a weld seam free vehicle floor based on extrusion welding according to claim 7, characterized in that The pressure of the roll in step two is 8-12kN, and the speed is 110-120mm / s; The laser power of the laser remelting is 3000-3500W, the scanning speed is 80-100mm / s, and the remelting depth is 0.3-0.5mm.

9. A process for producing a weld seam free truck bed floor based on extrusion welding according to claim 1, characterized in that The heat treatment method in step two is as follows: Nitrogen is introduced into the heat treatment furnace, heated to 520-540℃, and held for 30-40min, the weld-free plate is put into the heat treatment furnace, held for 1-2h, and quenched to obtain a weld-free carriage bottom plate.

10. A process for producing a weld seam free vehicle floor based on extrusion welding according to claim 9, characterized in that The heating rate of the heat treatment furnace is 8-12℃; The water temperature during quenching is 80-85℃.

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