Rolling laser welding process and structural member of galvanized martensitic steel

Abstract

The application provides a galvanized martensitic steel roll pressing laser welding process and a structural member, and relates to the technical field of welding.The process comprises the following steps: performing scraping treatment on a to-be-welded area of a galvanized martensitic steel plate to obtain a pretreated galvanized martensitic steel plate; performing first roll pressing forming on the pretreated galvanized martensitic steel plate to obtain a first intermediate profile with a semi-closed structure; performing knurling treatment on a predetermined area of a to-be-welded part of the first intermediate profile during the first roll pressing forming; performing welding on the first intermediate profile by using a four-spot coaxial laser to obtain a second intermediate profile; and performing subsequent processing on the second intermediate profile to obtain a structural member.For the preparation of a galvanized martensitic steel structural member by using a 'roll pressing forming + laser welding' process, the method can effectively inhibit the spatter and burst hole problems in the laser welding process, and is beneficial to improving the weld continuity and joint strength.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and more specifically, to a roll forming laser welding process and structural component for galvanized martensitic steel. Background Technology

[0002] With the increasing demands for lightweight and safety in new energy vehicles, ultra-high strength galvanized martensitic steel, represented by MS1500, combines excellent ultra-high strength with corrosion resistance and is widely used in core safety structural components such as anti-collision door sill beams and battery pack edge beams, making it the mainstream choice for new energy vehicle body materials. For the industrial production of these structural components, the industry generally adopts a "roll forming + laser welding" process: first, galvanized martensitic steel sheets are roll-formed into predetermined cross-sections such as B-shapes and U-shapes; then, the longitudinal open seams are closed by laser penetration welding to obtain the finished parts. This process combines the advantages of high forming precision, fast production efficiency, and good weld strength, making it suitable for large-scale mass production needs.

[0003] However, the presence of the galvanized layer presents an inherent and intractable challenge for laser welding: zinc has a boiling point of approximately 906°C, far lower than the melting point of steel (approximately 1540°C). When the laser penetrates the weld joint, the galvanized layer at the weld interface vaporizes rapidly before the base steel, forming high-pressure zinc vapor within the narrow joint gap. If the zinc vapor cannot escape smoothly before the molten pool solidifies, it will violently erupt, carrying molten metal with it, ultimately forming porosity and blowhole defects at the weld, while also generating a large amount of welding spatter, increasing subsequent cleaning costs. This problem is particularly prominent in galvanized martensitic steel: unlike ordinary steel, martensitic steel is extremely sensitive to welding heat input, with a very narrow usable process window. The blowholes and spatter caused by zinc vapor not only disrupt the weld continuity but also cause localized stress concentration, directly weakening the mechanical properties of the weld. Summary of the Invention

[0004] The problem solved by this invention is: for galvanized martensitic steel structural parts prepared by the "roll forming + laser welding" process, how to reduce defects such as pores and spatter caused by zinc vapor during laser welding, so as to ensure weld continuity and joint strength.

[0005] To address the above problems, this invention provides a roll forming laser welding process for galvanized martensitic steel, comprising: Step S1: Scrape the area to be welded on the galvanized martensitic steel sheet so that the thickness of the residual zinc layer in the area to be welded is the preset thickness, and obtain the pretreated galvanized martensitic steel sheet. Step S2: The pretreated galvanized martensitic steel sheet is subjected to a first roll forming to obtain a first intermediate profile with a semi-closed structure; during the first roll forming process, the predetermined area of ​​the first intermediate profile to be welded is knurled to produce concave and convex stripes. Step S3: Weld the first intermediate profile using a four-spot coaxial laser to obtain a second intermediate profile; wherein, the four spots of the four-spot coaxial laser are divided into two columns along the welding direction, with two spots arranged side by side in each column perpendicular to the welding direction; Step S4: Perform further processing on the second intermediate profile to obtain a structural component.

[0006] Optionally, the structural component includes a first cavity and a second cavity arranged in parallel; the first intermediate profile includes a first upper wall, a left side wall, a lower wall, a right side wall, a second upper wall, and a middle inclined wall connected in sequence; the end of the first upper wall away from the left side wall is a free end; the middle inclined wall overlaps the upper surface of the lower wall to form a first overlapping area, the first overlapping area dividing the lower wall into a lower left wall segment located to the left of the middle inclined wall and a lower right wall segment located to the right of the middle inclined wall; the left side wall, the first upper wall, the middle inclined wall, and the lower left wall segment are used to subsequently enclose and form the first cavity, and the middle inclined wall, the second upper wall, the right side wall, and the lower right wall segment are used to subsequently enclose and form the second cavity.

[0007] Optionally, the predetermined area of ​​the first intermediate profile to be welded is the middle area of ​​the upper surface of the lower wall corresponding to the first overlap area.

[0008] Optionally, in step S2, the first roll forming is performed on a multi-pass continuous roll forming production line. During the first roll forming process, the intermediate inclined wall gradually moves closer to the lower wall as the roll forming progresses. When the distance between the upper surface of the intermediate inclined wall and the lower wall is reduced to a preset distance, a knurling wheel integrated on the current pass roll is used to knurl the middle area of ​​the upper surface of the lower wall at the position corresponding to the first overlapping area, thereby processing concave and convex stripes on the upper surface of the lower wall. The preset distance is 0.5 mm to 1 mm larger than the diameter of the knurling wheel.

[0009] Optionally, in step S2, the depth of the raised and recessed stripes is 0.10 mm to 0.15 mm, the stripe spacing is 0.2 mm to 0.5 mm, the width is 6 mm to 10 mm, and the intersection angle of the raised and recessed stripes is 30 degrees to 60 degrees.

[0010] Optionally, in step S1, the preset thickness is less than 5 μm.

[0011] Optionally, in step S3, the power of the four-spot coaxial laser is 4kW to 8kW.

[0012] Optionally, in step S3, the welding speed is 3 m / min to 8 m / min.

[0013] Optionally, in step S4, the subsequent processing of the second intermediate profile to obtain a structural component includes: performing a second roll forming on the second intermediate profile so that the free end of the first upper wall overlaps the upper end of the intermediate inclined wall to form a second overlapping area; and performing welding on the second overlapping area so that the intermediate inclined wall is fixedly connected to the first upper wall to obtain the structural component.

[0014] The present invention also provides a structural component manufactured using the roll forming laser welding process of galvanized martensitic steel as described above.

[0015] Compared with related technologies, this invention first controls the thickness of the residual zinc layer in the area to be welded within a reasonable range through scraping, thereby reducing the total amount of zinc vapor generated during the welding process from the source and lowering the overall pressure of zinc vapor overflow. This creates the basic conditions for subsequent venting and fusion. Knurling is simultaneously completed during the first roll forming process, forming raised and recessed stripes, providing a continuous and unobstructed escape channel for zinc vapor. Finally, welding is performed using a specially arranged four-spot coaxial laser. The four spots are arranged in two rows along the welding direction, with two spots arranged side-by-side in each row perpendicular to the welding direction. The two side-by-side spots on the front side can preheat the area to be welded. The design allows the surface zinc layer to vaporize and escape in advance, further reducing the zinc vapor pressure inside the molten pool. It also effectively widens the leading edge of the molten pool, thus significantly increasing the weld width. The two parallel heat spots on the rear side can supplement the heating of the molten pool, promoting the complete escape of zinc vapor and reducing spatter through the post-heating effect. This arrangement structure can form a wider molten pool with more uniform heat input, which can completely cover the gap reserved by the knurling. Even if there are slight fluctuations in the gap, it can ensure that the two plates are completely fused. At the same time, the orderly heat input suppresses liquid metal spatter, thereby effectively suppressing spatter and bursting problems, which is conducive to improving weld continuity and joint strength. Attached Figure Description

[0016] Figure 1 This is a cross-sectional schematic diagram of the structural component in an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the process of the middle inclined wall gradually moving towards the lower wall direction during the first roll forming process in an embodiment of the present invention; Figure 3 This is a schematic cross-sectional view of the first intermediate profile in an embodiment of the present invention; Figure 4 This is an image of the first weld seam of the structural component manufactured in Embodiment 1 of the present invention; Figure 5 This is an image of the first weld seam of the structural component produced in Comparative Example 1 of the present invention; Figure 6 This is an image of the first weld seam of the structural component produced in Comparative Example 2 of the present invention.

[0017] Explanation of reference numerals in the attached figures: 1. First cavity; 2. Second cavity; 3. First upper wall; 4. Left side wall; 5. Lower wall; 51. Lower left wall segment; 52. Lower right wall segment; 6. Right side wall; 7. Second upper wall; 8. Middle inclined wall; 9. First overlapping area; 10. Second overlapping area. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0020] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used to distinguish different objects, not to describe a specific order or hierarchy. 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 indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0021] This invention provides a roll forming laser welding process for galvanized martensitic steel, used for manufacturing structural components, such as... Figure 1 As shown, the structural component is a closed structure formed by multiple roll forming and laser welding of a galvanized martensitic steel sheet, including a first cavity 1 and a second cavity 2 arranged side by side; the roll forming and laser welding process of the galvanized martensitic steel includes: Step S1: Scrape the area to be welded on the galvanized martensitic steel sheet so that the thickness of the residual zinc layer in the area to be welded is the preset thickness, and obtain the pretreated galvanized martensitic steel sheet. Step S2, as follows Figure 2 As shown, the pretreated galvanized martensitic steel sheet is subjected to a first roll forming to obtain a first intermediate profile with a semi-closed structure; during the first roll forming process, a predetermined area of ​​the first intermediate profile to be welded is knurled to produce concave and convex stripes. Step S3: Weld the first intermediate profile using a four-spot coaxial laser to obtain a second intermediate profile; wherein, the four spots of the four-spot coaxial laser are divided into two columns along the welding direction, with two spots arranged side by side in each column perpendicular to the welding direction; Step S4: Perform further processing on the second intermediate profile to obtain a structural component.

[0022] This invention first controls the thickness of the residual zinc layer in the area to be welded to a reasonable range through scraping, reducing the total amount of zinc vapor generated during welding from the source and lowering the overall pressure of zinc vapor overflow. This creates a foundation for subsequent venting and fusion. During the first roll forming process, knurling is simultaneously completed, forming raised and recessed stripes that provide a continuous and unobstructed escape channel for zinc vapor. Finally, welding is performed using a specially arranged four-spot coaxial laser. The four spots are arranged in two rows along the welding direction, with two spots arranged side-by-side in each row perpendicular to the welding direction. The two side-by-side spots on the front side can preheat the area to be welded. This arrangement allows the surface zinc layer to vaporize and escape in advance, further reducing the zinc vapor pressure inside the molten pool. At the same time, it can effectively widen the leading edge of the molten pool, thereby significantly increasing the weld width. The two parallel light spots on the rear side can supplement the heating of the molten pool, promoting the complete escape of zinc vapor and reducing spatter through the post-heating effect. This arrangement structure can form a wider molten pool with more uniform heat input, which can completely cover the gap reserved by knurling. Even if there are slight fluctuations in the gap, it can ensure that the two plates are completely fused. At the same time, the orderly heat input suppresses liquid metal spatter, thereby effectively suppressing spatter and bursting problems, which is conducive to improving weld continuity and joint strength.

[0023] In this embodiment of the invention, by linking three core steps—scraping pretreatment, knurling with reserved gap, and four-spot coaxial laser welding—a complete solution is constructed to address the core difficulties in laser welding of galvanized martensitic steel (such as porosity and spatter caused by zinc vapor): scraping pretreatment controls the total amount of zinc vapor from the source, avoiding venting failure caused by insufficient knurling gap capacity, and providing a feasible basis for the knurling gap venting scheme; the uniform gap reserved by knurling accommodates the zinc vapor venting requirements after the scraping reduction, solving the problem of rapid solidification of the four-spot molten pool when there is no pre-venting channel. The problem of trapping zinc vapor is solved, and the stable gap also avoids the risk of insufficient weld width failing to cover the lap area. The specially arranged four-spot welding is adapted to the process characteristics of knurling with gaps. It relies on the front and rear spot structures to ensure complete fusion of the gapped lap joint, and further promotes the discharge of residual zinc vapor through post-heating, making up for the risk of insufficient venting left by the first two steps. The three are interdependent, and the absence of any one link will lead to a decline in the final welding quality. Only through synergy can the problems of bursting and spatter be solved at the same time, and stable continuous production be achieved.

[0024] Specifically, such as Figure 3 As shown, the first intermediate profile includes a first upper wall 3, a left side wall 4, a lower wall 5, a right side wall 6, a second upper wall 7, and a middle inclined wall 8 connected in sequence; the end of the first upper wall 3 away from the left side wall 4 is a free end; the middle inclined wall 8 overlaps the upper surface of the lower wall 5 to form a first overlapping area 9, which divides the lower wall 5 into a lower left wall segment 51 located to the left of the middle inclined wall 8 and a lower right wall segment 52 located to the right of the middle inclined wall 8; the left side wall 4, the first upper wall 3, the middle inclined wall 8, and the lower left wall segment 51 are used to subsequently enclose and form the first cavity 1, and the middle inclined wall 8, the second upper wall 7, the right side wall 6, and the lower right wall segment 52 are used to subsequently enclose and form the second cavity 2. The predetermined area of ​​the first intermediate profile to be welded is the middle area of ​​the upper surface of the lower wall 5 at the position corresponding to the first overlapping area 9.

[0025] Specifically, in step S3, the first intermediate profile is welded using a four-spot coaxial laser to obtain the second intermediate profile. This includes welding the first overlapping area 9 using a four-spot coaxial laser to fix the intermediate inclined wall 8 to the lower wall 5, thereby forming the second cavity 2 and obtaining the second intermediate profile.

[0026] In some embodiments of the present invention, in step S2, as follows: Figure 2As shown, the first roll forming is performed on a multi-pass continuous roll forming production line. During the first roll forming process, the intermediate inclined wall 8 gradually moves closer to the lower wall 5 as the roll forming progresses. When the distance between the upper surface of the intermediate inclined wall 8 and the lower wall 5 decreases to a preset distance, the knurling wheel integrated on the current pass rolls knurls the middle area of ​​the upper surface of the lower wall 5 at the position corresponding to the first overlapping area 9, thereby processing concave and convex stripes on the upper surface of the lower wall 5. The preset distance is 0.5mm to 1mm larger than the diameter of the knurling wheel. In this embodiment, the preset distance is controlled to be 0.5mm to 1mm larger than the diameter of the knurling wheel, so that the gap between the intermediate inclined wall 8 and the lower wall 5 is just reserved to accommodate the knurling wheel. This allows the knurling to be performed at the final stage when the intermediate inclined wall 8 and the lower wall 5 are close to closing but not yet closed, without interfering with the knurling operation. Since the subsequent roll forming stroke is extremely short, the concave and convex stripes can be avoided from being destroyed by the subsequent roll forming, and the structure that provides an escape gap for zinc vapor can be stably preserved.

[0027] It should be noted that the "middle area" in "knurling treatment on the middle area of ​​the upper surface of the lower wall 5 corresponding to the first overlapping area 9" refers to the middle area in the cross-sectional width direction of the structural component. Figure 1 In the diagram, arrow X indicates the width direction of the structural component's cross-section, and arrow Y indicates the height direction of the structural component's cross-section.

[0028] In some embodiments of the present invention, in step S2, the depth of the raised and recessed stripes is 0.10 mm to 0.15 mm. In this embodiment, controlling the depth of the raised and recessed stripes to 0.10 mm to 0.15 mm ensures that a suitable gap is formed between the overlapping surfaces to allow sufficient zinc vapor to escape. This avoids both insufficient depth leading to inadequate venting and insufficient penetration due to insufficient depth, while also preventing insufficient penetration due to excessive depth, thus balancing venting requirements and the mechanical properties of the welded joint.

[0029] In some embodiments of the present invention, in step S2, the stripe spacing of the raised and recessed stripes is 0.2 mm to 0.5 mm, the width of the raised and recessed stripes is 6 mm to 10 mm, and the intersection angle of the raised and recessed stripes is 30 degrees to 60 degrees. In this embodiment, controlling the stripe spacing of the raised and recessed stripes to 0.2 mm to 0.5 mm, while setting the intersection angle of the raised and recessed stripes to 30 degrees to 60 degrees, can form a uniform and continuous exhaust channel on the overlapping surface, ensuring that zinc vapor can escape fully and avoiding the generation of porosity defects. It also avoids damaging the bonding strength of the overlapping surface due to excessive spacing, and avoids affecting the exhaust effect due to unreasonable angles, thus balancing exhaust efficiency and the structural stability of the joint.

[0030] In some embodiments of the present invention, the preset thickness in step S1 is less than 5 μm. In this embodiment, the preset zinc removal thickness is controlled to be less than 5 μm to remove as much of the zinc-rich layer on the surface of the welding area as possible, which affects the welding stability and reduces the probability of large-scale zinc vapor generation causing porosity.

[0031] In some embodiments of the present invention, in step S3, the power of the four-spot coaxial laser is 4kW to 8kW. In this embodiment, controlling the power of the four-spot coaxial laser to 4kW to 8kW provides sufficient heat input to ensure weld penetration and form a welded joint with acceptable mechanical properties, while avoiding excessive heat input due to excessive power, which could lead to coarse martensite grains and excessive burning of the zinc plating layer. It also avoids excessive thermal deformation that could affect the dimensional accuracy of the structural components.

[0032] In some embodiments of the present invention, the welding speed in step S3 is 3 m / min to 8 m / min. In this embodiment, controlling the welding speed to 3 m / min to 8 m / min can improve welding production efficiency and adapt to the needs of mass production while ensuring sufficient heat input and providing enough time for zinc vapor to escape, thus reducing porosity defects.

[0033] In some embodiments of the present invention, step S4, which involves further processing the second intermediate profile to obtain a structural component, includes: performing a second roll forming on the second intermediate profile so that the free end of the first upper wall 3 overlaps the upper end of the intermediate inclined wall 8 to form a second overlapping area 10; and welding the second overlapping area 10 so that the intermediate inclined wall 8 is fixedly connected to the first upper wall 3, thereby forming the first cavity 1 and obtaining the structural component.

[0034] In some embodiments of the present invention, in step S1, the galvanized martensitic steel plate is made of MS1500 galvanized steel, and the thickness of the galvanized martensitic steel plate is 1mm to 2mm. In this embodiment, controlling the thickness of the galvanized martensitic steel plate to 1mm to 2mm ensures that the overall strength and load-bearing capacity of the final structural component meet the usage requirements, while also conforming to the adaptability range of laser welding for processing thickness. This avoids the problems of increased cost and excessive structural weight caused by excessively thick plates, thus balancing structural strength and lightweight requirements.

[0035] This invention also provides a structural component manufactured using the roll forming laser welding process of galvanized martensitic steel as described above. For example, the structural component is a car door sill beam.

[0036] The present invention will be further described below with reference to specific embodiments.

[0037] Example 1 A1. The area to be welded of the galvanized martensitic steel plate is scraped to make the thickness of the residual zinc layer in the area to be welded 2μm, so as to obtain a pretreated galvanized martensitic steel plate; the material of the galvanized martensitic steel plate is MS1500 galvanized steel, and the thickness of the galvanized martensitic steel plate is 1.5mm.

[0038] A2. The pretreated galvanized martensitic steel sheet is subjected to a first roll forming process on a multi-pass continuous roll forming production line to obtain a first intermediate profile with a semi-closed structure. The first intermediate profile includes a first upper wall, a left side wall, a lower wall, a right side wall, a second upper wall, and a middle inclined wall connected in sequence. The end of the first upper wall away from the left side wall is a free end. The middle inclined wall overlaps the upper surface of the lower wall to form a first overlapping area, which divides the lower wall into a lower left wall segment located to the left of the middle inclined wall and a lower right wall segment located to the right of the middle inclined wall. The left side wall, the first upper wall, the middle inclined wall, and the lower left wall segment are used to subsequently enclose and form the first cavity. The middle inclined wall, the second upper wall, and the middle inclined wall are used to form the first cavity. The right side wall and the lower right wall section are used to subsequently enclose and form the second cavity; during the first roll forming process, the middle inclined wall gradually moves closer to the lower wall as the roll forming progresses. When the distance between the upper surface of the middle inclined wall and the lower wall decreases to a preset distance, the knurling wheel integrated on the current pass roll is used to knurl the middle area of ​​the upper surface of the lower wall at the corresponding position of the first overlapping area, thereby processing concave and convex stripes on the upper surface of the lower wall; wherein, the preset distance is 0.5 mm larger than the diameter of the knurling wheel; the depth of the concave and convex stripes is 0.13 mm, the stripe spacing of the concave and convex stripes is 0.35 mm, the width of the concave and convex stripes is 8 mm, and the intersection angle of the concave and convex stripes is 45 degrees.

[0039] A3. A four-spot coaxial laser is used to weld the first overlapping area to fix the middle inclined wall to the lower wall, thereby forming the second cavity and obtaining the second intermediate profile; wherein, the four spots of the four-spot coaxial laser are divided into two columns along the welding direction, with two spots arranged side by side in each column perpendicular to the welding direction; the total power of the four-spot coaxial laser is 4.8kW, the power of each of the four spots is 1.2kW, and the welding speed is 4.5m / min.

[0040] A4. The second intermediate profile is subjected to a second roll forming so that the free end of the first upper wall overlaps the upper end of the intermediate inclined wall to form a second overlapping area. A four-spot coaxial laser is used to weld the second overlapping area so that the intermediate inclined wall is fixedly connected to the first upper wall, thereby forming the first cavity and obtaining the structural component. The four spots of the four-spot coaxial laser are arranged in two rows along the welding direction, with two spots arranged side by side in each row perpendicular to the welding direction. The total power of the four-spot coaxial laser is 4.8kW, and the power of each of the four spots is 1.2kW. The welding speed is 4.5m / min. The structural component is a car anti-collision sill beam with a length of 2054mm, a cross-sectional width of 128mm, and a cross-sectional height of 67mm.

[0041] Example 2 The difference from Example 1 is that, in step A1, the thickness of the galvanized martensitic steel plate is 1.2 mm, the depth of the raised and recessed stripes is 0.10 mm, and the stripe spacing is 0.25 mm. In step A3, the total power of the four-spot coaxial laser is 4.0 kW, the power of each of the four spots is 1.0 kW, and the welding speed is 5 m / min.

[0042] Comparative Example 1 (without knurling treatment) The difference from Example 1 is that step A2 is as follows: the pretreated galvanized martensitic steel sheet is subjected to a first roll forming on a multi-pass continuous roll forming production line to obtain a first intermediate profile with a semi-closed structure; the first intermediate profile includes a first upper wall, a left side wall, a lower wall, a right side wall, a second upper wall, and a middle inclined wall connected in sequence; the end of the first upper wall away from the left side wall is a free end; the middle inclined wall overlaps the upper surface of the lower wall to form a first overlapping area, the first overlapping area dividing the lower wall into a lower left wall segment located to the left of the middle inclined wall and a lower right wall segment located to the right of the middle inclined wall; the left side wall, the first upper wall, the middle inclined wall, and the lower left wall segment are used to subsequently enclose and form the first cavity, and the middle inclined wall, the second upper wall, the right side wall, and the lower right wall segment are used to subsequently enclose and form the second cavity.

[0043] Comparative Example 2 The difference from Embodiment 1 is that step A3 is: using a single-spot coaxial laser to weld the first overlapping area so that the intermediate inclined wall and the lower wall are fixedly connected, thereby forming the second cavity and obtaining the second intermediate profile; wherein the power of the single-spot coaxial laser is 4.5kW and the welding speed is 4.5m / min.

[0044] Effect Example The first weld of the structural components prepared in Example 1, Comparative Example 1, and Comparative Example 2 was observed, and the results are shown in the figure. Figures 4 to 6 ,from Figures 4 to 6 It can be seen that no spatter or pore defects appeared at the first weld of the structural component prepared in Example 1; obvious spatter and pore defects appeared at the first weld of the structural component prepared in Comparative Example 1; obvious spatter defects appeared at the first weld of the structural component prepared in Comparative Example 2, and some areas showed incomplete fusion. The tensile strength of the joint of the first weld of the structural components prepared in Examples 1, 2, Comparative Example 1, and Comparative Example 2 was tested, and the results are shown in Table 1. It can be seen from Table 1 that the tensile strength of the joint of the first weld of the structural components prepared in Examples 1 and 2 is higher than that of Comparative Examples 1 and 2. It should be noted that the first weld refers to the weld corresponding to the first lap area.

[0045] Table 1

[0046] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A roll forming laser welding process for galvanized martensitic steel, characterized in that, include: Step S1: Scrape the area to be welded on the galvanized martensitic steel sheet so that the thickness of the residual zinc layer in the area to be welded is the preset thickness, and obtain the pretreated galvanized martensitic steel sheet. Step S2: The pretreated galvanized martensitic steel sheet is subjected to a first roll forming to obtain a first intermediate profile with a semi-closed structure; during the first roll forming process, the predetermined area of ​​the first intermediate profile to be welded is knurled to produce concave and convex stripes. Step S3: Weld the first intermediate profile using a four-spot coaxial laser to obtain a second intermediate profile; wherein, the four spots of the four-spot coaxial laser are divided into two columns along the welding direction, with two spots arranged side by side in each column perpendicular to the welding direction; Step S4: Perform further processing on the second intermediate profile to obtain a structural component; The structural component includes a first cavity (1) and a second cavity (2) arranged in parallel. The first intermediate profile includes a first upper wall (3), a left side wall (4), a lower wall (5), a right side wall (6), a second upper wall (7), and a middle inclined wall (8) connected in sequence. The end of the first upper wall (3) away from the left side wall (4) is a free end. The middle inclined wall (8) overlaps the upper surface of the lower wall (5) to form a first overlapping area (9). The first overlapping area (9) divides the lower wall (5) into a lower left wall segment (51) located to the left of the middle inclined wall (8) and a lower right wall segment (52) located to the right of the middle inclined wall (8). The left side wall (4), the first upper wall (3), the middle inclined wall (8), and the lower left wall segment (51) are used to subsequently enclose and form the first cavity (1). The middle inclined wall (8), the second upper wall (7), the right side wall (6), and the lower right wall segment (52) are used to subsequently enclose and form the second cavity (2). The predetermined area of ​​the first intermediate profile to be welded is the middle area of ​​the upper surface of the lower wall (5) corresponding to the first overlapping area (9); In step S2, the first roll forming is carried out on a multi-pass continuous roll forming production line. During the first roll forming process, the middle inclined wall (8) gradually moves closer to the lower wall (5) as the roll forming progresses. When the distance between the upper surface of the middle inclined wall (8) and the lower wall (5) is reduced to a preset distance, the knurling wheel integrated on the current pass roll is used to knurl the middle area of ​​the upper surface of the lower wall (5) at the position corresponding to the first overlapping area (9), thereby processing concave and convex stripes on the upper surface of the lower wall (5). The preset distance is 0.5 mm to 1 mm larger than the diameter of the knurling wheel.

2. The roll forming laser welding process for galvanized martensitic steel according to claim 1, characterized in that, In step S2, the depth of the raised and recessed stripes is 0.10 mm to 0.15 mm, the stripe spacing is 0.2 mm to 0.5 mm, the width of the raised and recessed stripes is 6 mm to 10 mm, and the intersection angle of the raised and recessed stripes is 30 degrees to 60 degrees.

3. The roll forming laser welding process for galvanized martensitic steel according to claim 1, characterized in that, In step S1, the preset thickness is less than 5 μm.

4. The roll forming laser welding process for galvanized martensitic steel according to claim 1, characterized in that, In step S3, the power of the four-spot coaxial laser is 4kW to 8kW.

5. The roll forming laser welding process for galvanized martensitic steel according to claim 1, characterized in that, In step S3, the welding speed is 3 m / min to 8 m / min.

6. The roll forming laser welding process for galvanized martensitic steel according to claim 2, characterized in that, In step S4, the subsequent processing of the second intermediate profile to obtain a structural component includes: performing a second roll forming on the second intermediate profile so that the free end of the first upper wall (3) overlaps the upper end of the intermediate inclined wall (8) to form a second overlapping area (10); performing welding on the second overlapping area (10) so that the intermediate inclined wall (8) is fixedly connected to the first upper wall (3) to obtain the structural component.

7. A structural component, characterized in that, It is manufactured using the roll forming laser welding process for galvanized martensitic steel as described in any one of claims 1 to 6.

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