Customized products for motor vehicles

Abstract

The utility model relates to a kind of customized products 1 for motor vehicle, it includes at least two steel plates 4,5,steel plate 4,5 at least partially superposed and mutually welded. At least two adjacent steel plates have the overlapping portion 3 of length at least 100 millimeters, transverse width at least 15 millimeters along edge. The total thickness of the overlapping portion is 1.6 millimeters to 6.0 millimeters, further include a plurality of laser weld with annular joint 10.Each annular joint is circular or oval with outer ring diameter of 5 millimeters to 12 millimeters. The joint width 13 of each annular joint is 1.0 millimeter to 3.0 millimeter. The minimum distance S between adjacent laser weld is at least 25 millimeters. The maximum protrusion height 11 of annular joint is 0.5 millimeter, measured from the outer surface 6 of the overlapping portion 3 of the steel plate of customized product. Improve welding strength and welding reliability and product lightweight potential, while reducing manufacturing cost.

Description

Technical Field

[0001] This utility model relates to a customized product for motor vehicles, particularly for structural components or body parts of vehicles. Background Technology

[0002] The use of high-strength materials is becoming increasingly common in order to reduce the weight of motor vehicles and lower their fuel consumption. It is also crucial to compensate for the increased weight of modern vehicles in terms of entertainment, active safety, and comfort.

[0003] One approach to achieving lightweighting goals is to use relatively expensive lightweight metal alloys, such as magnesium, aluminum, or plastic composites. Besides the cost disadvantages, this is generally not the optimal solution from a CO2 emissions perspective. Therefore, for structural components in motor vehicles, high-strength steel solutions are typically the most common and efficient.

[0004] To further enhance lightweighting potential, it is known that so-called custom blanks can be used as semi-finished products to manufacture structural components. These custom blanks can be manufactured through different processes, but the underlying principle is that the steel sheet thickness and / or steel sheet alloy are customized and selected in specific parts of the custom blank according to different specific requirements.

[0005] An example of such customized blanks is a tailor-rolled blank (TRB) made from a steel sheet blank or coil along its length (the rolling direction of the coil). Typically, the thinnest part of such a tailor-rolled blank is not less than 1 mm thick, and in one or more thickness gradients, each thickness gradient is not greater than 0.4 mm.

[0006] Another known technology is tailor-welded blank (TWB) technology, in which multiple blank portions are cut from at least one sheet steel coil and welded together with butt welds or lap welds. In this case, thickness gradients exceeding 0.4 mm are possible, which is an advantage for TRB. Another advantage of TRB is the ability to combine different grades of steel; for example, it can provide more ductile sections to meet specific crash performance requirements or offer more flexible connections during body assembly.

[0007] Another technique, sometimes referred to as TWB, is the butt welding blank technique. The difference between TWB and conventional butt welding blanks is that the smaller butt welding blank is placed entirely on top of the larger base blank and welded together, while conventional butt welding uses laser butt welding with no overlap or only partial overlap, resulting in a smaller surface area and resistance spot welding.

[0008] TRB, TWB, and welded blanks are all semi-finished products, which are then cold-formed or hot-formed after welding. This helps reduce the number of production equipment, production space, and logistics required to manufacture such custom products based on the aforementioned welded plate technology. While these technologies have become increasingly popular and applied to mass production in recent years, this common method of manufacturing such custom parts also has some drawbacks.

[0009] One disadvantage of using resistance spot welding for TWB (tie-wax bonding) of butt weld blanks or lap weld joints (especially in custom products where a large number of weld points are required) is the long welding time or the need for multiple robotic welding stations, thus occupying a significant amount of space. Because electrode contact is required, the parts must always be able to contact from both sides.

[0010] This drawback is even more pronounced for common custom-made products, which are made by connecting pre-formed components together using resistance spot welding, rather than by directly welding flat blanks. Processing pre-formed components requires more space and more precise welding equipment.

[0011] One approach to reducing the aforementioned drawbacks of welding blanks, other lapped blanks, and welded shaped parts to manufacture custom products is to use laser welding. Recently, so-called remote laser welding has been implemented in the automotive industry for attaching shaped structural components to the vehicle body. While it avoids some of the disadvantages of resistance spot welding, there is still room for improvement in welding speed, cost, joint strength, and even optical quality.

[0012] Furthermore, in the field of battery cell manufacturing, it is well known that laser spot welding can be used to assemble cell components with high precision and speed. In this context, it is also well known that so-called spiral welding can be used to quickly and reliably weld metal parts together. However, this application does not involve high-strength steel products, steel plates with a total thickness exceeding 1.5 mm, or steel plates that require specific mechanical and corrosion requirements for structural components and bodies of motor vehicles. Utility Model Content

[0013] This utility model relates to a customized product for motor vehicles.

[0014] A custom product for motor vehicles is made of at least two steel plates, which are at least partially stacked and welded together. At least two adjacent steel plates have overlapping portions along their edges, with a length of at least 100 mm and a width of at least 15 mm transversely to the edges. The total thickness of the overlapping portions is 1.6 mm to 6.0 mm, which is the sum of the thicknesses of the steel plates in the overlapping portions. The overlapping portions include multiple laser welds. The invention is characterized in that the laser welds are annular joints, each annular joint being an eighth circle with an outer diameter of 5 mm to 12 mm or an ellipse with a first length of 7 mm to 15 mm and a second length of 4 mm to 9 mm transversely to the first length. The joint width of each annular joint is 1.0 mm to 3.0 mm (viewed from the surface). Measured from the geometric center of adjacent laser welds, the minimum distance between adjacent laser welds is at least 20 mm, preferably at least 25 mm.

[0015] Measured from the outer surface of the overlapping portion of the custom product, the maximum protrusion height of the annular seam is 0.5 mm.

[0016] According to this utility model, the term "joint" refers to the weld nugget, which is mainly composed of a mixture of pre-melted materials from the steel plate.

[0017] The main advantage of this custom product lies in its annular weld joint. The cross-sectional dimensions of its weld (or weld nugget) are comparable to traditional weld joints, but the welding speed is faster, simpler, and less risky. In particular, it avoids excessive heat input from the laser beam, preventing overheating at the weld center and the resulting thermal tension during welding and subsequent self-cooling. This suppresses welding defects (such as micro or macro cracks) and residual stress in the weld joints of custom components. This last advantage is especially important when the custom product is a cold-formed high-strength steel product and / or a hot-formed and compression-hardened product (not made from welded plates, but from components formed by laser welding).

[0018] Preferably, in a cross-sectional view passing through the center of the laser weld seams in the overlapping portion, the upper steel plate portion is located on top of the lower steel plate portion, and multiple laser weld seams respectively form a wavy topology in the lower steel plate portion, the wavy topology contacting the previously molten material (melt nugget) of the upper and lower steel plate portions. The wavy topology is characterized by having at least two peaks on each side of a symmetrical vertical centerline, each peak having a height of at least 0.2 mm. According to this invention, "upper" and "lower" refer to the orientation of the overlapping steel plate portions relative to the laser beam. The upper steel plate faces the laser beam, and the lower steel plate portion is located below the upper steel plate and faces away from the laser beam.

[0019] The multiple peaks are primarily a result of the spiral laser beam path and multiple rotations during welding, as well as the precise heat input of the beam. Therefore, preferably, the peak distance, measured laterally to the peak height and between the centers of adjacent peaks, is in the range of 0.4 mm to 0.9 mm. These peaks within the lower steel plate are located on the side facing the laser welding beam. The main advantage of this wavy topology and multi-peak structure is that it significantly improves the joint strength by increasing the surface dimensions and contact area of ​​both the previously formed and unformed steel compared to large weld nuggets with a substantially flat bottom, or large deep weld nuggets with no unformed material in the lower steel below the nugget.

[0020] According to another preferred embodiment, multiple laser weld seams are formed by a single laser beam point moving and rotating along a helical path 2 to 8 times, with no laser beam point movement within the inner surface. The inner surface has an inner diameter of at least 4 mm, or an inner elliptical dimension of at least 6 mm along the main axis and at least 3 mm along the secondary axis. This path and single-point laser technology greatly facilitate shaping the wavy topology of the annular joint. The number of rotations is preferably 4 to 6 times to achieve an optimal balance between welding speed and weld nugget topology and joint strength.

[0021] Correspondingly, a next preferred feature is that each of the multiple laser weld seams is formed by a single laser beam point moving solely along a helical path from the inside to the outside. This inside-out welding direction optimizes heat transfer within the overlapping portions of the steel plates, preventing overheating at the center. In this invention, "solely" means that the laser beam does not oscillate, rotate, or undergo any other secondary motion while moving along the helical path; otherwise, this would shorten the welding time, reduce the overall quality and strength of the wavy topology and the annular joint, and potentially lead to overheating and cracking risks at the weld points.

[0022] Preferably, the multiple laser welds are formed by a single laser beam point moving only once from the inside to the outside along a helical path. This helps to maintain a short welding time, a good wavy topology, and the overall quality and strength of the annular joint.

[0023] In a preferred embodiment of the customized product, one or more overlapping portions are not pretreated before welding and / or not post-treated with a laser beam after welding. If pre-coated steel sheets are used, costly decoction (ablation) can be avoided. Like most structural components in a car body, the customized product according to this invention only requires electrophoresis along with the entire body-in-white. Furthermore, since overheating at the weld center is avoided, no post-heat treatment, such as stress-relief annealing, is required.

[0024] In a preferred embodiment of the customized product, at least one steel plate is made of thermoformable, hardenable, or thermoformable and hardenable alloy steel. The first option means the customized product is a semi-finished product, i.e., a flat sheet metal blank similar to the customized welded or welded blank described at the outset. The second option means the customized product comprises at least one overlapping portion with an circumferential seam, wherein welding is performed after the individual components are formed separately.

[0025] In theory, the individual components can also be molded separately, then welded together to form the annular laser connector according to this invention, and then heated and thermoformed into the final customized product.

[0026] Figure 4 The table shows examples of hot-formable steel grades. "Steel A" and "Steel B" are conventional hot-formable steel grades with a pre-hardened microstructure of ferrite and pearlite, and a tensile strength of approximately 450 MPa to 600 MPa. After compressive hardening, due to their fully or almost fully martensitic microstructure, the tensile strength reaches 1350 MPa to 1600 MPa.

[0027] "Steel C" and "D" are advanced hot-formed steel grades with high carbon content and a small amount of niobium. These steel grades can have tensile strengths exceeding 1700 MPa, and their microstructure is entirely martensitic.

[0028] "Steel E" and "F" are steel grades used for both cold and hot forming. Their significantly lower carbon content reduces hardenability, resulting in a tensile strength of approximately 900 MPa to 1050 MPa after hot forming. Under cold forming conditions, the tensile strength is approximately 400 MPa to 550 MPa.

[0029] In a preferred embodiment of the customized product, at least one steel sheet includes a surface coating. The surface coating comprises at least one layer primarily composed of aluminum (Al) and / or zinc (Zn), and optionally up to 10% silicon (Si), manganese (Mn), and / or magnesium (Mg), with a thickness of at least 5 micrometers to 40 micrometers. For hot forming, the pre-coating helps prevent scaling on the surface of the billet during austenitizing heating and can also serve as the first anti-corrosion layer in the final customized product.

[0030] If the steel sheet is a hot-formed and press-quenched alloy steel, i.e., a pre-formed component, the surface coating is an alloy coating, which also includes at least one iron-rich layer and / or an intermetallic compound layer. This alloying is carried out as part of the hot-forming process during the austenitizing heating process.

[0031] According to another embodiment of this customized product, the laser-welded annular joint contains an average of 0.1% to 1.0% (by weight) aluminum (Al) and / or 0.1% to 1.0% zinc (Zn), as well as less than 0.5% nickel (Ni) and less than 0.5% chromium (Cr). This composition is a result of the wire-free joining operation. It avoids the use of welding wires containing expensive alloying elements (such as Cr or Ni), and / or avoids the slow welding speed caused by the need to melt the welding wire. Due to the helical path of the laser beam, there is no need to ablate a pre-coating (such as AlSi or Zn(ZnO)), while still meeting the Al and Zn content limits. During the welding process, part of the pre-coating is evaporated and / or ablated. Particularly preferably, the thickness of the aluminum-based pre-coating is less than 20 micrometers, and the aluminum content of the annular joint is less than 0.5%.

[0032] According to another embodiment of the customized product, multiple steel plates after laser welding undergo thermoforming and compression hardening treatment. At least one steel plate has a tensile strength (Rm) of at least 1000 MPa. The laser weld is compression hardened, and the hardness variation at the weld and within a 20 mm radius around the weld is less than 10%. This means a very uniform hardness distribution is achieved, making the customized product highly reliable in simulated impact test behavior. The thermoformed component has no or almost no heat-affected zone.

[0033] According to a preferred embodiment of this customized product, a small flat patch of steel plate is arranged on top of a larger flat steel plate to completely overlap with the other steel plate. This can serve as a welding blank for the customized product, which can be further processed after cold forming or hot forming. However, it can also be welded after the various components have been cold-formed or hot-formed according to this invention.

[0034] According to another preferred embodiment, the customized product is flat; the length of the overlapping portion along the edge is at least 100 mm, and the width of the overlapping portion transverse to the edge is at most 50 mm, particularly at most 30 mm. This can be the lap weld blank mentioned at the beginning, and can be further processed after cold forming or hot forming.

[0035] Preferably, the penetration depth of the annular joint (melt nugget) into the lower steel plate portion is at most 90% of the thickness of the lower steel plate portion. More preferably, the penetration depth is in the range of 30% to 70% of the thickness of the lower steel plate portion. The lower steel plate portion does not face the laser beam during welding.

[0036] Preferably, the annular seam (melt nugget) protrudes from the outer surface of the overlapping upper plate portion by a maximum of 15% of the upper plate portion thickness. This allows for sufficient tool contact during cold forming, especially during hot forming and compression hardening. It also meets surface roughness and other tolerance requirements. No post-processing is required. The upper plate portion faces the laser beam during welding.

[0037] The customized products according to this utility model can combine the above-mentioned customized blank technologies. The spliced ​​blank can be combined with the butt-welded blank, or it can be combined with the rolled blank. In this case, the small patch is preferably placed on the outer side of the thickness step portion. The butt-welded blank can also be combined with the lap-welded blank. Even the lap-welded blank can be used as a splice, with the small patch serving as a third steel plate, preferably placed on the outer side of the overlapping portion of the first and second steel plates. Another combination is that the rolled blank and the second steel plate are lap-welded at the overlapping portion. In all these cases, the overlapping portion includes multiple annular seams as laser welds. Attached Figure Description

[0038] This utility model will be further described in the following drawings. Identical or very similar functions or geometric details will have the same reference numerals. All embodiments shown are merely examples of customized products based on this utility model and are not intended to limit the scope of protection.

[0039] Even though this utility model is described using only the B-pillar as an example in the following drawings, any other structural component of a motor vehicle according to this utility model is also part of this disclosure. Examples include other parts of the vehicle sidewall (e.g., the A-pillar), the entire sidewall (double door ring), the front or rear portion of said sidewall (front door ring, rear door ring), floor frame, subframe, front H-frame or rear H-frame, roof frame with or without window frame members, front bumper system or rear bumper system, battery tray inner frame, battery tray outer frame, and to name just a few other automotive applications.

[0040] Figure 1 Different customized products based on this utility model;

[0041] Figure 2 : A magnified top view of the overlapping portion of an embodiment of the customized product;

[0042] Figure 3a , Figure 3b , Figure 3c , Figure 3d , Figure 3e Cross-sectional and top views of laser welds according to various embodiments of the present invention;

[0043] Figure 4 The preferred steel alloy watch for customized products according to this utility model;

[0044] Figure 5 The laser beam path for annular seams of overlapping portions of customized products according to an embodiment of the present invention.

[0045] Figure label:

[0046] 1. Customized product; 2. B-pillar; 3. Overlapping part; 4. Upper steel plate; 5. Lower steel plate; 6. Outer surface of overlapping part; 7. Upper end of 4; 8. Lower end of 5; 9. Edge of 3; 10. Circular joint; 11. Protrusion height; 12. Penetration depth; 13. Joint width; 15. Peak; 16. Peak height; 17. Peak spacing; 18. Outer diameter of joint; 19. Inner diameter of joint; 20. Patch; 21. Large steel plate; 22. Welded plate; 23. Butt weld; 24. Thickness of 4; 25. Thickness of 5; 50. Laser beam path; 51. Path start point; 52. Path end point; 53. Ring closure; C. Centerline; H. Height of 2; L. Length of 3; W. Width of 3; S. Joint distance; HAZ. Heat-affected zone. Detailed Implementation

[0047] All accompanying drawings are schematic diagrams and simplified illustrations. Figure 1 All embodiments shown represent structural components of a motor vehicle sidewall, in the form of a B-pillar. A B-pillar typically includes an inner closure panel (inner shell), a main central structural component, and a skin panel (outer shell). This invention primarily relates to the main central component. It should be understood that other shells, as well as, for example, airbag and vehicle lock support brackets, can be assembled to said main structural component. Hereinafter, this main central component will be referred to as the B-pillar, as a customized product according to this invention.

[0048] In the first example, such as Figure 1 As shown in a), column B2 comprises an upper steel plate 4 and a lower steel plate 5. The two steel plates 4 and 5 are only partially overlapped and welded together. Here, in Figure 1 In all embodiments discussed herein, the terms “upper” and “lower” refer to positions in the drawing plane, rather than the relationship between the corresponding steel plate and the laser beam side during the welding process.

[0049] The upper end 7 of the upper steel plate 4 is widened to connect to the roof longitudinal beam member (not shown) of the vehicle side wall. The lower end 8 of the lower steel plate 6 is also widened, but by a greater margin, to connect to the lower rocker arm (not shown). Between the upper end 7 and the lower end 8, the steel plates 4 and 5 include an overlapping portion 3 along the edge 9, the length L of which is approximately 150 mm to 250 mm, and the width W transverse to the edge is at least 15 mm to at most 50 mm. The length L of the overlapping portion is the width of the B-pillar in that area. The total (wall) thickness of the overlapping portion 3 is 1.6 mm to 6.0 mm. For B-class to E-class vehicles, the thickness 24, 25 of the B-pillar and its steel plate is typically 1.4 mm to 2.5 mm, so the total thickness can be 2.8 mm to 5 mm. The overlapping portion 3 includes multiple laser welds. These laser welds are circumferential joints 10. Details can be found in [link to relevant documentation]. Figure 3a .

[0050] The minimum distance S between adjacent laser welds having annular joints 10 is at least 20 mm, preferably 25 mm, measured from the (virtual) center of the adjacent laser welds. The maximum protrusion height 11 of the annular joint 10 is 0.5 mm, measured from the surface 6 of the overlapping portion 3 of the custom product 1. This is in Figure 2 You can see it better in the middle.

[0051] For details of the laser weld, please refer to Figure 2 Each annular joint 10 or weld nugget is an eighth of a circle, with an outer ring diameter of 5 mm to 12 mm; or it is elliptical, with a first length of 7 mm to 15 mm and a second length (measured transversely to the first length) of 4 mm to 9 mm. Viewed from surface 6, the joint or weld nugget width W of each annular joint 10 is 1.0 mm to 3.0 mm. The inner ring diameter is equal to the outer diameter minus the joint width.

[0052] from Figure 1 As can be seen from a), the overlapping part 3 is located at approximately 1 / 3 of the total height H of column B.

[0053] exist Figure 1 In the second example shown in b), column B2 and Figure 1 The B-pillar described in section a) is essentially the same, but an additional patch 20 is welded to the upper steel plate 4. The patch 20 extends upwards from near the overlap portion 3 to the upper end 7 of the upper steel plate 4, but does not reach the widened upper end 7. The patch 20 serves as local reinforcement for the central portion of the B-pillar, where it needs to withstand the highest specific load and tensile stress. The patch 20 overlaps with the upper steel plate 4 at the overlap portion 3'. The patch 20 encompasses the upper steel plate 4 and is secured to it via the same laser-welded joint as in the overlap portion 3. Of course, if the patch thickness differs from the thickness 15 of the lower steel plate 5, the geometric details may differ.

[0054] Figure 1 a) and Figure 1 The example in b) can also be combined so that the patch is no longer a separate steel plate, but rather a component of the lower steel plate and the overlapping portion itself, but this is not shown in the figure. This combination limits the freedom of choice in the material and thickness of the area of ​​maximum load, but helps to reduce costs.

[0055] Figure 1c) shows column B 2, which employs a well-known conventional welded plate with butt welds 23, combined with patch 20, which is laser-welded to welded plate 22 having multiple annular seams 10. Smaller steel plates serve as small patches 20, arranged on top of larger steel plates to completely overlap. The larger steel plate 21 comprises an upper steel plate 4 and a lower steel plate 5, which may have the same or different thicknesses and / or steel grades. While this custom product 1 can be constructed from a substantially flat blank, column B and patch 20 may also have been cold-formed or hot-formed and pressure-hardened before being joined at their overlapping portion 3' by laser welds of multiple annular seams 10.

[0056] Figure 1 (d) shows a B-pillar 2 constructed of a large steel plate 21, with its lower end connecting to the door sill and its upper end connecting to the roof longitudinal beam. A small patch 20 is located in the center to reinforce the large steel plate 21. The patch 20 completely overlaps the large steel plate 21, forming an overlapping portion 3'. The patch 20 extends between the widened upper end 7 and lower end 8 of the large steel plate 21. The small patch is laser-welded to the large steel plate 21 through multiple annular seams 10. Similar to the previous example, the B-pillar 2, as a custom product 1, can be in a substantially flat and undeformed state. However, the custom product 1 can also be pre-formed to its final geometry.

[0057] Figure 2 Shown in top view format Figure 1 b) to Figure 1 The enlarged area of ​​the overlapping portions 3 and 3' in d). The minimum distance S between adjacent laser welds with annular joints 10 is at least 20 mm, preferably 25 mm, and this distance is measured from the (virtual) center of the adjacent laser weld points. The laser welds are mostly arranged in a basically straight line along the length of the patch 20. However, the arrangement of the weld points can also be more uneven.

[0058] Figure 3a A top view of a laser weld seam having an annular joint 10 according to the present invention is shown. The annular joint 10 or weld nugget is a circle with an outer ring diameter D of 5 mm to 12 mm; or it may be an ellipse with a first length of 7 mm to 15 mm and a second length of 4 mm to 9 mm, the second length being measured transversely to the first length.

[0059] In both cases, when viewed from the surface, the joint width W of each annular joint 10 is 1.0 mm to 3.0 mm.

[0060] Figure 3bA cross-sectional view of the annular joint 10 according to an embodiment of the present invention is shown. In the figure, the vertical center line C represents the axis of symmetry of the weld nugget ring. The joint 10 or weld nugget can be seen on both sides of the center line. Measured from the upper surface 6 of the overlapping portion of the custom product 1, the maximum protrusion height 11 of the annular joint is 0.5 mm. The upper outer surface 6 is the face pointing towards the laser beam during welding. The joint / weld nugget width 13 of each annular joint 10 is 1.0 mm to 3.0 mm. The measurement of the width 13 of the joint 10 is most reliable in the macroscopic cutting analysis of the cross-section. The width 13 is measured at the center of the joint between the two plates, such as... Figure 3b As shown. The depth 12 of the annular joint 10 penetrating the lower steel plate portion 5 is at most 90% of the thickness 25 of the lower steel plate portion 5. The bottom of the lower steel plate portion 4 and the weld or weld nugget 10 has a wavy structure, wherein the pre-melted material of the upper steel plate portion 4 and the pre-melted material of the lower steel plate portion 5 are in contact with each other. The wavy topology is characterized by four (lower) peaks 15 on each side of the symmetrical vertical centerline, each peak height 16 being at least 0.2 mm. In this illustrative example, there are also three upper peaks on opposite sides. The number of peaks 15 indicates the number of rotations of the laser beam during the helical path welding process. The peak spacing 17, measured transversely to the peak height direction and starting from the center of the adjacent peaks 15, is 0.4 mm to 0.9 mm. Between the left and right weld nuggets, the upper steel 4 is mainly composed of material that was not completely melted during the welding process. The same is true for the portion below (wavy) and immediately adjacent to the bottom of the weld or weld nugget 10. When custom products are in the form of basic flat blanks or after cold forming, a heat-affected zone (HAZ) may exist.

[0061] However, if the custom product is a thermoformed and press-quenched part, and the annular seam has been laser-welded before forming and quenching, then there is no heat-affected zone. This can be seen from... Figure 3c From this, we can see that Figure 3c The rest of the parts and Figure 3b same.

[0062] Figure 3d Another embodiment according to the present invention is shown, with Figure 3b The embodiments described above are very similar. However, although annular seams are also present, the bottom of the annular seam or weld nugget 10 does not have a characteristic wavy topology. Unlike the peaks of the aforementioned wavy topology, the bottom exhibits only relatively minor unevenness. This can be achieved by increasing the size of the laser beam spot, thereby reducing the gap between beam paths during welding.

[0063] and Figure 3c similar, Figure 3e A custom-made product 1, which has undergone thermoforming and hardening, is shown, and has no heat-affected zone near the weld of the overlapping portion 3. However, in this case, no similar [condition] is observed. Figure 3d The wave-shaped topology of the embodiment shown.

[0064] Figure 4 Selected and preferred steel alloys (grades) for manufacturing customized products according to this invention are disclosed. All percentages given are by weight. For each steel alloy, the balance is iron and unavoidable impurities.

[0065] Figure 5 The path of the laser beam during welding and its preferred direction from the inside out are shown. The starting point 51 or path 50 is closer to the center of the subsequently formed annular joint. After the laser beam rotates two revolutions, the helical trajectory changes to close the ring. This example shows the minimum number of rotations according to the present invention, i.e., two revolutions, and the additional ring closure 53, which closes with a circumferential angle of approximately 120°.

Claims

1. A custom product for motor vehicles, comprising at least two steel plates, said steel plates being at least partially stacked and welded to each other, said at least two adjacent steel plates having an overlapping portion along their edges with a length of at least 100 mm and a transverse width of at least 15 mm, said overlapping portion having a total thickness of 1.6 mm to 6.0 mm; The overlapping portion includes multiple laser weld seams; Its features are: The laser weld is an annular joint, and each annular joint is an eighth circle with an outer ring diameter of 5 mm to 12 mm or an ellipse with a first length of 7 mm to 15 mm and a second length of 4 mm to 9 mm measured transversely to the first length. The joint width of each of the aforementioned annular joints is 1.0 mm to 3.0 mm; Measured from the center of adjacent laser welds, the minimum distance between adjacent laser welds is at least 25 mm; Measured from the outer surface of the overlapping portion of the custom product, the maximum protrusion height of the annular seam is 0.5 mm.

2. The customized product of claim 1, wherein, In a cross-sectional view passing through the center of the laser weld in the overlapping portion, the upper steel plate portion is located on top of the lower steel plate portion, and the plurality of laser welds respectively form a wavy topology in the lower steel plate portion, the wavy topology being in contact with the previously molten material of the upper and lower steel plate portions; The wavy topology is characterized by having at least two peaks on each side of the symmetrical vertical center line, and each peak having a height of at least 0.2 mm.

3. The customized product of claim 1, wherein, The plurality of laser welds are formed by a single laser beam point moving and rotating along a spiral path for 2 to 8 turns, and no laser beam point moves within the inner surface; the inner surface has an inner diameter of at least 4 mm, or an inner elliptical dimension of at least 6 mm along the main axis and at least 3 mm along the auxiliary axis.

4. The customized product of claim 1, wherein, Each of the aforementioned laser weld seams is formed by a single laser beam point moving only along a spiral path from the inside to the outside.

5. The customized product of claim 1, wherein, Each of the aforementioned laser weld seams is formed by a single laser beam point moving only once from the inside to the outside along a spiral path.

6. The customized product of claim 1, wherein, The overlapping portion was not pre-treated before welding and / or not post-treated using a laser beam after welding.

7. The customized product of claim 1, wherein, At least one of the steel plates is made of alloy steel that is thermoformable, hardenable, or both thermoformable and hardenable.

8. The customized product according to claim 1, wherein, At least one of the steel plates includes a surface coating, the surface coating comprising at least one layer with aluminum (Al) and / or zinc (Zn) as the main components, and optionally a layer comprising up to 10% silicon (Si), manganese (Mn), and magnesium (Mg), with a thickness of at least 5 micrometers and up to 40 micrometers; wherein, when the steel plate is a hot-formed and press-quenched alloy steel, the surface coating is an alloy coating, and further includes at least one iron-rich layer and / or an intermetallic compound layer.

9. The customized product of claim 1, wherein, The laser-welded annular joint contains 0.1% to 1.0% by weight of Al and / or Zn, and less than 0.5% of nickel (Ni) and less than 0.5% of chromium (Cr).

10. The customized product of claim 1, wherein, The multiple steel plates after laser welding undergo thermoforming and compression hardening treatment, and at least one of the steel plates has a tensile strength (Rm) of at least 1000 MPa. The laser weld is subjected to compression hardening treatment, and the hardness change at the weld and within a 20 mm range is less than 10%.

11. The customized product of claim 1, wherein, One of the steel plates is a small flat patch arranged on top of a larger flat steel plate to completely overlap with the other steel plate.

12. The customized product of claim 1, wherein, The customized product is flat; the length of the overlapping portion along the edge is at least 100 mm, and the width of the overlapping portion transverse to the edge is at most 50 mm.

13. The customized product of claim 1, wherein, The maximum penetration depth of the annular joint into the lower steel plate is 90% of the thickness of the lower steel plate.

14. The customized product of claim 1, wherein, The penetration depth of the annular joint into the lower steel plate portion is in the range of 30% to 70% of the thickness of the lower steel plate portion.

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