Structural components and methods for vehicles

Abstract

1. A structural member for a vehicle frame configured to at least partially support bending loads, the structural member comprising: a main member having a substantially U-shaped cross-section with a bottom, a first side wall and a second side wall, the main member having a region configured to support bending loads; and a first patch having a first patch edge and an opposing second patch edge, the first patch being attached to the main member by a continuous laser weld substantially along the first patch edge and along the second patch edge to an inside of the first patch, at least in the region configured to support bending loads.

Description

[[Technical Field]]

[0001] The present disclosure relates to a structural member for a vehicle frame, wherein the structural member is configured to at least partially support a bending load. The present disclosure further relates to a method for manufacturing such a structural member. This application claims priority to EP21382108 filed on February 11, 2021. [[Background Art]]

[0002] Vehicles such as automobiles incorporate a structural frame designed to withstand all loads that the vehicle may experience during its service life. The structural frame is further designed to withstand and absorb impact in the event of a collision, for example with another vehicle. The structural frame is also designed to be as light as possible, in order to reduce the emission of pollutants such as CO2 into the environment.

[0003] The structural frame of an automobile may include, for example, bumpers, pillars (e.g., A-pillars, B-pillars, C-pillars), side impact beams and rocker panels. These and other structural members may have one or more regions having a substantially U-shaped (also referred to as "hat-shaped") cross-section. These structural members can be manufactured by various methods and can be made of various materials. As mentioned above, lightweight materials that improve vehicle integrity during a collision and improve energy absorption are desired.

[0004] It is generally known in the automotive industry that at least most of the structural members of a vehicle frame are made of ultra-high strength steel (UHSS), which exhibits optimized maximum strength per unit weight and advantageous formability properties.

[0005] In this disclosure, ultra-high-strength steel (UHSS) can be considered as steel having an ultimate tensile strength of at least 1000 MPa. UHSS can achieve such high tensile strength after a hot forming process. Some UHSS require rapid cooling to obtain a martensitic structure and the corresponding high ultimate tensile strength. Other UHSS can achieve high ultimate tensile strength with relatively slow cooling or air cooling ("air hardening"). Some UHSS do not require hot forming and the corresponding austenitization to obtain high ultimate tensile strength, and instead have and maintain high strength after cold forming.

[0006] UHSS steel can exhibit high ultimate tensile strengths of 1500 MPa, and even over 2000 MPa, especially after press hardening. In such operations, the steel blank is heated above its austenitizing temperature, particularly above Ac3, to substantially completely austenitize the blank. After heating above this temperature for a certain period of time, the blank is press-formed to deform it. Simultaneously, the blank is rapidly cooled to substantially "completely harden" it and obtain a martensitic structure. Press hardening is also called "hot stamping," and when rapidly cooled, it is also called "hot forming quenching" (HFDQ).

[0007] In addition to using appropriate materials, patch welding, for example, can impart suitable properties to vehicle structural members in terms of collision behavior and weight reduction. For instance, welding the first patch to a main member can reinforce the main member without adding undesirable weight. Blanks with added patches are sometimes called "patchwork blanks" to distinguish them from "tailor-welded blanks," which are blanks joined together by welding the ends.

[0008] Typically, patches are welded to the main component using spot welding, a well-known and widely used welding technique in the automotive industry. However, spot welding has several limitations.

[0009] These limitations include a certain minimum distance between spot welds (e.g., 5–20 mm), a certain minimum overlap area between spot welds (e.g., approximately 25 mm), and the time required to position the plate and spot welding tool (e.g., approximately 4 seconds). These distances and times vary depending on the material and thickness of the patch and workpiece.

[0010] Another drawback of spot welding is that, because it is a two-sided access technique, welding a patch can be very difficult as the welding gun cannot easily access the area where the patch is placed.

[0011] Furthermore, weld pieces and patches (assemblies also called patchwork) may undergo several post-processing steps that can damage or break some spot welds due to twisting or bending of the patchwork. As a result, patchwork can fall apart. For example, when a patchwork blank is hot-formed, the heat of the furnace (and / or subsequent deformation) can warp the patchwork blank, causing some spot welds to loosen or break. Such phenomena can occur even if the number of spot welds joining the patches and pieces is carefully selected.

[0012] There is also a technique called laser welding. Laser welding generally mimics spot welding. Laser stitching is a localized, typically linear, weld. By creating multiple laser stitches, multiple separate welds are created, which can mimic the welds of spot welding.

[0013] Document WO2020 / 003900A1 discloses the use of laser welding to join a first plate-like member and a second plate-like member, wherein the laser stitch is provided longitudinally along the central region of the second plate-like member. This specification also discloses the use of laser-arc hybrid welding along the outer and longitudinal edges of the second plate-like member. This disclosure aims to provide an improvement to patch welding techniques. [Overview of the Initiative]

[0014] In a first embodiment, a structural member for a vehicle frame is provided, which is at least partially configured to support bending loads. The structural member comprises a main member and a first patch. The main member has a substantially U-shaped cross-section consisting of a bottom, a first side wall, and a second side wall. The main member further comprises a region configured to support bending loads. The first patch has a first patch edge and a second patch edge opposite to it. The first patch is attached to the main member by continuous laser welding, substantially along the first patch edge and along the second patch edge, in the region configured to support bending loads.

[0015] At least two patch edges joined by continuous laser welding provide a seamless connection between the patch and the main member in the continuous laser-welded area. This allows the patch and the main member to function as a single unit, at least in the area configured to support bending loads.

[0016] Therefore, for example, the behavior of structural members during a collision can be improved. Because the patch and main member function as a single unit, the resulting reinforcement is enhanced compared to patchwork welded by, for example, spot welding and / or laser stitching. The strength and deformation behavior of the finished part are improved compared to the same part of the same material and thickness (where the patchwork blank is formed by spot welding).

[0017] Furthermore, continuous laser welding prevents the patchwork components from separating in the welded area, even in the event of collisions like the one described above.

[0018] Throughout this disclosure, the patch should be understood as a piece of material that, when attached to the main member, is entirely contained within the boundaries of the main member. That is, the patch may completely overlap the main member, or vice versa. The overlap of the main member with the entire patch allows the patch and the main member to function as a single unit after continuous laser welding.

[0019] These advantages also apply to the example of introducing the patchwork blank into the furnace described above. If the spot welds break, the patchwork becomes unusable. Continuous laser welding can avoid or at least mitigate this problem.

[0020] In general, continuous laser welding has been shown to be particularly advantageous for structural members that support bending loads.

[0021] In particular, automotive framework components or areas subjected to bending loads include: the upper or middle sections of the A-pillars and B-pillars, the rear rail, the (central longitudinal) tunnel, the floor, the hinge pillar, the rocker area, and the door ring. The embodiments disclosed herein can be used in particular for these components.

[0022] In some embodiments, the first patch can be attached to a region configured to support the bending load of the main member by continuously laser welding along all edges of the patch. In this case, since all edges of the patch are continuously laser welded, the behavior of the patchwork may be further improved. This can enhance the ability of the patchwork to function as a single unit.

[0023] Because there is no minimum distance required between spot welds, the patch size can be further reduced. Consequently, lighter structural members can be obtained.

[0024] In some embodiments, the first patch may extend over the bottom, first side wall, and second side wall of the main member.

[0025] In one embodiment, the first patch may extend on the first side wall at a height of at least 10% of the height of the first side wall, and the first patch may extend on the second side wall at a height of at least 10% of the height of the second side wall. In some embodiments, the first patch may extend over the first and / or the second side wall for at least 25% of the height of the corresponding side wall, more specifically between 25% and 50% of the height of the corresponding side wall.

[0026] These examples reflect the fact that the greater the extension of the patch on the side wall of the main member, the greater the reinforcement, which for example can lead to better behavior of the patchwork during a collision.

[0027] In another embodiment, a first edge of the first patch may extend substantially along a first joint between the first side wall and the bottom of the main member. Further, a second edge of the first patch may extend along a second joint between the second side wall and the bottom of the main member.

[0028] In this case, continuous laser welding of the patch enables good behavior of the patchwork when the structural member is subjected to a bending load, and at the same time enables significant weight reduction.

[0029] In some embodiments, a second patch may be provided. The second patch has a first patch edge and an opposite second patch edge, and the second patch is attached to the main member by continuous laser welding along the first patch edge and the second patch edge, at least in a region configured to bear a bending load.

[0030] Having a plurality of patches attached to the main member may improve the versatility, efficiency, and optimization of the structural member. For example, the number, size, and attachment positions of the patches can be selected to meet the design requirements of the structural member and provide a specific desired kinematic behavior.

[0031] In general, having multiple patches allows for appropriate reinforcement of structural members where appropriate, without unnecessarily increasing the weight of the structural members (i.e., obtaining one or more of the aforementioned advantages of continuous laser welding).

[0032] In some embodiments, the main member may be made of hardened steel. The first and / or second patches may be made of a material more ductile than the hardened steel. Having patches that are more ductile than the main member prevents fracture of the main member during impact, or ensures that fracture occurs only after significantly high deformation. When the main member and patches are joined by continuous laser welding, the main member gains some of the ductility provided by the patches. This improvement in the ductility of the structural member may be greater than, for example, when the patches are more ductile than the main member and the patchwork is joined by conventional spot welding. This is because spot welding cannot make the patchwork function as a single unit.

[0033] Furthermore, the ductility provided by one or more patches may allow the structural member to absorb more energy in the event of a collision. Therefore, the behavior of the structural member may also be improved in this respect.

[0034] One or more patches, which are more ductile than the main component and welded to it by continuous laser welding, can reinforce the main component while simultaneously giving it deformation and energy absorption capabilities. The main component, such as a hardened steel billet, may not be able to obtain these capabilities by other means.

[0035] In a further embodiment, a structural member for a vehicle frame is provided, which is at least partially configured to support bending loads. The structural member comprises a main member and a first patch. The main member has a substantially U-shaped cross-section consisting of a bottom, a first side wall, and a second side wall. The main member further comprises a region configured to support bending loads. The first patch has a first patch edge and a second patch edge opposite to it. The first patch is attached to the main member by continuous laser welding inside the first patch, substantially along the first patch edge and along the second patch edge, in the region configured to support bending loads.

[0036] In some examples, the first patch may be attached to a region configured to support the bending load of the main member by continuous laser welding inside the first patch along all edges of the patch.

[0037] In some examples, a second patch may be provided. The second patch has a first patch edge and an opposing second patch edge, and the second patch is attached to the main member by continuous laser welding inside the second patch along the first and second patch edges, in a region configured to support at least a bending load.

[0038] All the effects and advantages of the first embodiment described above also apply to this embodiment.

[0039] In another embodiment, a method is provided for manufacturing a structural member that is at least partially configured to support a bending load in order to obtain the structural member described in the Disclosure.

[0040] The method includes providing a main blank including a region configurable to support a bending load, and providing at least a first patch blank having a first patch blank edge and an opposing second patch blank edge. The method further includes forming a patchwork blank by attaching at least the first patch blank to the main blank by continuous laser welding substantially along the first patch blank edge and the second patch blank edge, or inside the first patch blank, in at least the region configurable to support a bending load, and forming the patchwork blank to obtain a structural member as disclosed herein.

[0041] This method makes it possible to manufacture structural members with improved behavior as described above. For example, this method may allow the resulting patchwork to function as a single, integrated unit.

[0042] Generally, this method can provide a faster and simpler welding process. This is because, for example, it avoids the need to position the spot welding gun for each spot weld and does not require simultaneous access to both welding sides.

[0043] Furthermore, there is no need to consider the minimum overlap distance, the minimum distance between spot welds, or the number of spot welds.

[0044] In this respect, this method allows for the attachment of a patch along the first joint between the first side wall and the bottom of the main member. This may be impossible with spot welding due to the relatively small size of the patch and technical limitations such as the minimum required distance between spot welds and the minimum required overlapping area of ​​spot welds.

[0045] Furthermore, continuous laser welding allows for optimization of patch shape. For example, patches of different shapes can be used depending on the design requirements. In this respect, this method offers more options compared to spot welding, for instance.

[0046] Furthermore, reducing the size of the patch can also reduce the weight of the final structural member. Non-limiting embodiments of this disclosure are described below with reference to the accompanying figures. [Brief explanation of the drawing]

[0047] [Figure 1A] Figure 1A schematically shows an example of a vehicle structural member that is at least partially configured to support a bending load. [Figure 1B] Figure 1B schematically shows two examples of patch attachment to main members of vehicle structural members that are at least partially configured to support bending loads. [Figure 1C] Figure 1C schematically shows two examples of patch attachment to a main member of a vehicle structural member that is at least partially configured to support a bending load. [Figure 2A] Figure 2A schematically shows two additional examples of vehicle structural members that are at least partially configured to support bending loads. [Figure 2B] Figure 2B schematically shows two additional examples of vehicle structural members that are at least partially configured to support bending loads. [Figure 3A] Figure 3A schematically shows two more examples of vehicle structural members that are at least partially configured to support bending loads. [Figure 3B] Figure 3B schematically shows two more examples of vehicle structural members that are at least partially configured to support bending loads. [Figure 4] Figure 4 is a flowchart of a method for manufacturing a structural member that is at least partially configured to support a bending load. [Figure 5A] Figure 5A is a schematic diagram illustrating examples of structural members and how they can deform under bending loads. [Figure 5B] Figure 5B is a schematic diagram illustrating examples of structural members and how they can deform under bending loads. [Modes for carrying out the invention]

[0048] The figures illustrate exemplary embodiments and are intended solely as an aid to understanding the claimed subject matter, and are not intended to limit it in any way.

[0049] Figure 1A schematically represents a structural member for a vehicle that is at least partially configured to support bending loads. The structural member 100 comprises a main member 110 having a substantially U-shaped cross-section consisting of a bottom 111, a first side wall 112, and a second side wall 113. The main member 110 comprises a region 114 configured to support bending loads.

[0050] Structural members used in a vehicle's framework are generally subject to a variety of loads. These loads stem from the weight of the structure, vehicle acceleration and deceleration, vibrations during driving, and many other factors. However, certain structural members need to be designed and certified to handle specific load conditions, such as collisions or impacts with utility poles, pedestrians, or other vehicles. Some structural members are expected to be subjected to bending loads (such as bumpers and pillars) and are specially designed to withstand such loads. Other structural members (such as crash boxes) are expected to be subjected to compressive loads instead and are specially designed to withstand such loads.

[0051] Structural members of a vehicle's frame, such as an automobile, can be subjected to bending loads throughout their entirety. However, some structural members are expected to be subjected to bending loads only in specific parts or areas, or a structural member may have areas that are expected and designed to be subjected to high bending loads, while other areas are not expected or designed to be subjected to the same high bending loads. The patchwork blanks or patchworks provided herein are most useful in the areas along these regions where bending loads are significant.

[0052] The dots in Figure 1A indicate that the structural member 100 may consist of one or more additional pieces or elements not shown. These one or more additional pieces or elements are not limited in any way, for example, in terms of shape, size, cross-sectional shape, material, and / or how they are attached to the main member 110.

[0053] In this and other figures, the main members are shown having a "hat-shaped" or "U-shaped" cross-section. In all these examples, it will be clear that the components or main members may include side flanges extending outward from the side walls.

[0054] The structural member further comprises a first patch 120. The first patch 120 has a first patch edge 121 and a second patch edge 122 facing it. The first patch 120 is attached to the main member 110 by continuous laser welding along the first patch edge 121 and the second patch edge 122 in a region configured to support at least a bending load 114.

[0055] In this embodiment and other embodiments, the first patch 120 is attached to the inside 105 of the main member 110 (the patch is shown by the dashed line). That is, the patch is attached to the main blank, and the patchwork blank is deformed so that the patch is located inside the U-shape. In other embodiments, the first patch 120 may be attached to the outside 107 of the main member 110, as schematically shown in Figure 2B.

[0056] In this embodiment and other embodiments, the first patch edge 121 and the second patch edge 122 generally extend along the longitudinal direction 116 of the main member 110. In some other embodiments, these patch edges 121, 122 may extend in other directions.

[0057] As described above, the assembly of the patches 120 attached to the main member 110 is sometimes referred to as patchwork.

[0058] By attaching the first patch 120 to the main member 110 by continuous laser welding in areas configured to support the bending load 114, the patchwork can function as a single entity in the areas configured to support the bending load 114. Thus, the reinforcement of the main member 110 by attaching the patch 120 can be improved with respect to other techniques, such as spot welding, where a seamless connection between the first patch 120 and the main member 110 is not achievable.

[0059] Furthermore, if the main member 110 is subjected to bending loads, torsional forces, or forces that tend to separate the main member 110 from the first patch 120 during further processing and manufacturing, the main member 110 and the first patch 120 will not delaminate, or at least delamination will be less than with other patch attachment methods such as spot welding. In addition, the durability of the main member 110, and consequently the durability of the structural member 100, may also be improved.

[0060] Furthermore, while spot welding has limitations as described above (for example, a certain minimum distance between required spot welds), in this embodiment, the size of the patch 120 can be reduced, and the structural member 100 can be made lighter.

[0061] In some embodiments, all edges of the patch 120 are attached to the main member 110 by continuous laser welding in areas configured to support at least the bending load 114. In one embodiment, as shown in Figure 1B, there may be one or more discontinuities in the attachment along the outer circumference of the patch 120. Such small discontinuities generally do not adversely affect the functionality and benefits provided by this disclosure, unless they are located in areas subject to impact or areas with high bending loads. In another embodiment, as shown in Figure 1C, the attachment is made along the entire circumference of the patch 120 so as to be discontinuous in the attachment.

[0062] This improves the level of improvement and reinforcement achieved. Specifically, attaching the main member 110 to the first patch 120 by performing continuous laser welding along the four edges of the first patch 120, particularly along the entire circumference of the first patch 120 as shown in Figure 1C, enhances the advantages commented on herein.

[0063] As used herein, "all around" should be understood to mean that there are virtually no discontinuities in the application area, as shown in Figure 1C. This is in contrast to the situation in Figure 1B, where the application is carried out along the perimeter of the patch, but there is one or more discontinuities in the application.

[0064] One or more discontinuities in the attachment by continuous laser welding may exist regardless of the number of patch edges joined to the main member 110 in this manner.

[0065] Although the first patch 120 is depicted as a rectangle in Figure 1A, the first patch 120 may have any suitable shape. For example, the first patch 120 may be any type of polygon, such as a trapezoid.

[0066] The first patch 120 may extend over the bottom 111, the first side wall 112, and / or the second side wall 113. In some examples, such as Figures 2A and 2B, the first patch 120 extends over the bottom and both side walls 111, 112, and 113. In some other examples, such as Figures 3A and 3B, the patch extends over the bottom and one of the side walls 112 and 113.

[0067] It is also possible to attach additional patches to the main component; see, for example, Figures 3A and 3B. If two or more patches exist, this does not rule out the possibility of overlap between them.

[0068] The region 114 configured to support the bending load can extend entirely or partially over the main member 110. For example, in Figure 1A, the region 114 configured to support the bending load partially extends over the main member 110.

[0069] It should be understood that the region 114 configured to support a bending load is a region positioned or set up to serve the purpose of supporting a bending load. Prior to positioning or setting, region 114 may be named a region (not shown) that can be set up to support a bending load. This positioning or setting may consist of, for example, performing any method, such as hot forming, on the region that can be set up to support a bending load.

[0070] The first patch 120 may partially or completely overlap with the region 114 configured to support bending loads. The first patch 120 may not partially or completely overlap with the region not configured to support bending loads. It should be understood that the region not configured to support bending loads includes any region within the main member 110 that is not configured to support bending loads, in contrast to region 114. That is, this may be a region of a part that is not expected to be subjected to bending loads under normal use. This portion can be used to join the part to other parts of the vehicle frame.

[0071] For example, as shown in Figure 1A, the patch partially extends over the area of ​​the main member 110 configured to support the bending load 114, and partially extends over the area of ​​the main member 110 not configured to support the bending load. In an alternative example, the first patch 120 may extend over the entire area configured to support the bending load 114, and may extend / partially / not extend over the entire area not configured to support the bending load.

[0072] The first patch 120 may be attached to the main member 110 by continuous laser welding over an area configured to support at least the bending load 114. The attachment between elements 110 and 120 may be made at more locations than along the edge of the first patch 110. For example, additional attachments of any type and in any pattern may be made substantially over the central part of the first patch 120.

[0073] Additionally, outside the region configured to support the bending load 114, additional attachments may be made between elements 110 and 120. For example, the main member 110 and the first patch 120 may be attached via spot welding and / or continuous laser welding in the region not configured to support the bending load.

[0074] The main member 110 and the first patch 120 may be made of any suitable material, such as ultra-high-strength steel (UHSS). The main member 110 and the first patch 120 may be made of the same steel, for example, 22MnB5 steel, or different steels.

[0075] Figure 1A shows what are understood to be the dimensions of the main member 110 as "height" 117, "width" 115, and "length" 116.

[0076] Although drawn in a substantially linear fashion, the base 111, the first side wall 112, and the second side wall 113 are not necessarily linear. For example, the base 111 may be curved or bend in any way. The same applies to the side walls 112 and 113. Each element 111, 112, and 113 may have a curvature or bend equal to or different from that of any of the other elements 111, 112, and 113. Furthermore, the side walls 112 and 113 do not have to be symmetrical.

[0077] For example, the height of the first side wall 112 may differ from the height of the second side wall 113. For example, the height 117 along the length 116 of the first side wall 112 and / or the second side wall 113 may also differ. For example, the width 115 of the bottom may differ from the height 117 of the first side wall 112 and / or the second side wall 113. Other examples may include any combination of the above examples. The only limitation is that a person skilled in the art will recognize that the main member 110 has a substantially U-shaped cross-section.

[0078] Figures 2A and 2B schematically show a vehicle structural member 100 configured at least partially to support a bending load according to an embodiment. In Figures 2A and 2B, the first patch 120 extends over the bottom 111, first side wall 112, and second side wall 113 of the main member 110. The first patch 120 is attached by continuous laser welding to at least a portion of the main member 110 configured to support a bending load 114 in any of the methods shown above with respect to Figure 1. Thus, both the configuration of the patch 120 and the main member 110 benefit from the effect of attaching the patch 120 and the main member 110 by continuous laser welding.

[0079] The configuration in Figure 2A allows for greater reinforcement in the area where patch 120 extends. For example, patch 120 can extend over at least 10%, specifically 25%, of the height of the first side wall 112, and the first patch 120 can extend over at least 10%, specifically 25%, of the height of the second side wall 113. In Figure 2A, patch 120 may extend over approximately 75% of each side wall 112, 113.

[0080] Due to continuous laser welding, the patchwork's resistance to damage caused by bending loads that would cause the patchwork to break apart is, in this case, higher than that of configurations other than the one shown in Figure 2A, but only in types of attachment methods used, such as spot welding and / or laser suture welding.

[0081] In the configuration shown in Figure 2B, the first edge 121 of the first patch 120 substantially extends along the first joint 125 (schematically shown by a dotted line) between the first side wall 112 and the bottom 111 of the main member 110. The second edge 122 of the first patch 120 extends along the second joint 126 between the second side wall 113 and the bottom 111 of the main member 110. Extending along the joint can be understood herein as being relatively close to the fillet region at the intersection of the U-shaped side wall and the bottom. That is, this can mean a position less than 2 cm or less than 1 cm from the edge of the fillet.

[0082] This configuration makes it possible to reduce the weight of the structural member 100 while simultaneously reinforcing and strengthening the structural member 100 when subjected to bending loads and reducing the risk of fracture.

[0083] In particular, due to the limitations of spot welding as commented herein, it is not possible to weld near the joints 125, 126 between the bottom 111 and the side walls 112, 113, as is possible with continuous laser welding, which may result in greater weight reduction than, for example, using spot welding. In some examples, the dimensions of the patch 120 in a direction substantially perpendicular to the length 116 of the main member 110 (and substantially parallel to the height 117 and / or width 115 of the main member 110) can be reduced by at least 5 mm, and optionally at least 10 mm, for each side 121, 122 of the patch 120 with respect to the patch spot-welded to the main member 11.

[0084] A similar consideration applies to Figure 3B, where the first patch 120 extends substantially along the first joint between the first side wall 112 and the bottom 111 of the main member 110, and the second patch 130 extends substantially along the second joint between the second side wall 113 and the bottom 111 of the main member 110.

[0085] The configuration in Figure 3B includes the advantages described in relation to Figure 2B, and also includes the advantage of being lighter.

[0086] As already mentioned, any number of patches extending across any of the side walls 112, 113 and / or bottom 111 of the main member 110 can be selected according to design criteria, for example, regarding reinforcement, resistance to bending loads, resistance to the risk of bursting, and / or the weight requirements of the structural member 100.

[0087] Furthermore, in any of the embodiments described herein, the first patch 120 and / or the second patch 130 may be made of a material that is more ductile than the main member 110. In particular, the main member 110 may be made of hardened steel, and the first patch 120 and / or the second patch 130 may be made of a material that is more ductile than hardened steel.

[0088] To avoid decarburization and scale formation during the molding process, 22MnB5 is sometimes coated with an aluminum-silicon coating. The composition of 22MnB5 is summarized below in weight percent (the remainder being iron (Fe) and impurities): C 0.20 - 0.25 Si 0.15 - 1.35 Mn 1.10 - 1.25 P < 0.025 S < 0.008 Cr 0.15 - 0.30 Ti 0.02 - 0.05 B 0.002 - 0.004 N < 0.009

[0089] Several 22MnB5 steels with similar chemical compositions are commercially available. However, the exact amounts of each component in 22MnB5 steel may vary slightly depending on the manufacturer. Other ultra-high-strength steels include, for example, BTR165, which is commercially available from Benteler.

[0090] Usibor® 1500 is supplied in a ferrite-pearlite phase, which has a fine grain structure distributed in a homogeneous pattern. Its mechanical properties are related to this structure. After heating, hot stamping, and subsequent quenching, a martensite microstructure is formed. As a result, maximum strength and yield strength are significantly improved.

[0091] The composition of Usibor(registered trademark) 1500, expressed in weight percent, is as follows (the remainder being iron (Fe) and unavoidable impurities): C Si Mn PS Cr Ti BN 0.24 0.27 1.14 0.015 0.001 0.17 0.036 0.003 0.004

[0092] Usibor® 2000 is a boron steel with even higher strength. The yield strength of Usibor® 2000 can exceed 1400 MPa after hot press die quenching, and the ultimate tensile strength can exceed 1800 MPa. The composition of Usibor® 2000 includes up to 0.37 wt% carbon, up to 1.4 wt% manganese, up to 0.7 wt% silicon, and up to 0.005 wt% boron.

[0093] On the other hand, Ductibor® and other soft steels can also be used for hot forming and hot forming die quenching. However, these steels do not develop a martensitic structure. The resulting steel will have lower ultimate tensile strength and yield strength, but higher elongation at break.

[0094] The ultimate tensile strength of Ductibor® 400 is 450 MPa or higher, Ductibor® 500 is 550 MPa or higher, and Ductibor® 1000 is 1000 MPa or higher.

[0095] CRL-340LA is a steel material commercially available from SSAB. It is a high-strength, low-alloy steel intended for general pressing, bending, and forming purposes. Its composition is as follows (weight %): C 0.1% or less Si 0.040% or less Mn 1% or less P 0.030% or less S max 0.025 Al min 0.015% Nb + Ti max 0.1

[0096] In this embodiment, the patch is designed to have more ductile properties than the main member. The patch can be made from any steel that is suitable for forming, including hot and cold forming, and that provides appropriate mechanical properties after such processing. Ductibor®, CRL-340LA, and similar steels, such as low-alloy steels, are suitable for "softer" patches.

[0097] The combination of the soft patch and the "rigid" main member allows the structural member 100 to absorb more energy, for example, in the event of a collision. Another advantage is that fracture of the main member 110 when subjected to bending load is avoided or occurs only after significant deformation.

[0098] It should be noted that this improvement in the properties of the structural member 100 is particularly due to the effect resulting from the fact that patches 120 and 130 are attached by continuous laser welding and that patches 120 and 130 have higher ductility than the main member 110.

[0099] In other words, when patches 120 and 130 are more ductile than the main member 110 and are attached by spot welding in areas where the patchwork is configured to support a bending load 114, the properties of the structural member 100 are generally not as good as in the case of continuous laser welding, because the patchwork does not function as a single, integrated unit. In particular, under impact and corresponding bending loads, local deformation occurs between the spot welds, and these deformations can lead to localized fracture.

[0100] Similarly, if patches 120 and 130 are less ductile than the main member 110 and are attached by continuous laser welding in areas where the patchwork is configured to support a bending load 114, the properties of the structural member 100 may generally not be as good as when patches 120 and 130, which are more ductile than the main member 110, are used, because the patchwork is less ductile than the main member 110.

[0101] Figure 4 shows a method 400 for manufacturing a structural member 100 that is at least partially configured to support a bending load as disclosed herein, for example, a structural member 100 like the one in Figures 1A, 2A, 2B, 3A, or 3B. The structural member 100 may include one or more attached patches 120 as shown in Figure 1B or 1C, or it may have other configurations as disclosed herein.

[0102] The method includes step 410, which provides a main blank including a region that can be configured to support a bending load.

[0103] The method further includes step 420 of providing at least a first patch blank having a second patch blank edge opposite a first patch blank edge. For example, in some embodiments, only one patch blank is provided. In some other examples, two or more patch blanks are provided.

[0104] The main blank and at least the first patch blank may, for example, have the same or different sizes, shapes, and / or materials.

[0105] For example, in some embodiments, both the main blank and at least the first patch blank are rectangular and of the same size, and both the main blank and the patch blank are made of the same ultra-high-strength steel (UHSS), such as Usibor® 1500.

[0106] In some other examples, the main blank is rectangular, at least the first patch blank is square or rectangular, the main blank is at least larger than the first patch blank, the main blank is made of hardenable steel, e.g., Usibor® 1500, and at least the first patch blank is made of a more ductile steel, e.g., Ductibor® 1000.

[0107] Generally, the main blank and at least the first patch blank can be substantially flat. However, this is not always the case. For example, the main blank and / or at least the first patch blank may be bent in some way.

[0108] The method further includes step 430 of attaching at least a first patch blank to a main blank by substantially continuous laser welding along the first patch blank edge and the second patch blank edge, specifically along all edges of the patch, in a region configured to support a bending load, in order to form a patchwork blank. When attaching at least the first patch blank, one or more discontinuities may be provided.

[0109] As explained above, continuous laser welding allows patchwork blanks to function as a single, integrated unit.

[0110] The method further includes step 430 of forming a patchwork blank to obtain a structural member 100 as disclosed herein with reference to any one of Figures 1A, 1B, 1C, 2A, 2B, 3A and / or 3B.

[0111] Forming imparts the desired shape to the patchwork. The resulting structural member 100 includes a main member 110 having a substantially U-shaped cross-section.

[0112] The forming can include any type of forming, such as hot forming or cold forming. Forming can not only shape the patchwork but also impart additional properties, such as increased strength of the patchwork due to changes in the steel's microstructure, as in hot forming.

[0113] Hot forming may involve heating the patchwork blank to an austenitizing temperature above, specifically above Ac3, for a minimum time, such as several minutes. The patchwork blank is then transferred to a press to deform it and form the part, while simultaneously being rapidly cooled to below 400°C, specifically below 300°C. When hardenable steel is used for the main component and softer steel for the patchwork, the main component has high ultimate tensile strength, but is relatively brittle and exhibits little elongation to fracture. On the other hand, the patchwork material is more ductile and exhibits greater elongation to fracture.

[0114] In some cases, molding and other subsequent processes such as notching, trimming, and calibration can be carried out in a multi-stage system that combines different stations on the same press.

[0115] The same or similar steel as described above may be used. In some examples, a quenchable steel main blank may be zinc-coated. In some embodiments, the steel may be quenched to obtain a martensitic structure, and in other embodiments, the steel may be air quenchable or nearly air quenchable.

[0116] When cold forming is used, in some cases, after forming, the part is heated in a furnace and subjected to heat treatment, including quenching, to obtain the desired structure and corresponding mechanical properties.

[0117] Furthermore, this method offers a further improvement: as shown in Figure 3B, it allows for the attachment of a patch blank along the first joint between the first side wall and the bottom of the main member blank, which may generally be impossible with spot welding due to requirements such as the relatively small size of the patch, the minimum distance between spot welds, and the minimum required overlapping area of ​​spot welds.

[0118] This also means that the desired effect, such as reinforcement, linked to patches 120 and 130 can be achieved with smaller sizes of patches 120 and 130, and thus a lighter structural member 100 may be obtained.

[0119] Furthermore, continuous laser welding can enable optimization of the patch 120 and 130 shapes. The available patch blank shapes may be more limited with spot welding due to the limitations of this technique already commented on. Therefore, this method allows for a wider selection of patch blank shapes than spot welding. Generally, the patch blank shape can be any shape as needed.

[0120] Additionally, the thickness of the patch blank can be selected as needed.

[0121] This method may include additional steps or operations. For example, seam tracking may be used for efficient continuous laser welding.

[0122] Figures 5A and 5B schematically illustrate U-shaped members and how they deform under bending loads. The first example at the top is a fully hardened beam, the second example in the middle relates to a hardened main member with a soft patch similar to the example in Figure 3B, and the third example at the bottom is a hardened main member with a soft patch similar to the example in Figure 3A. In Figures 5A and 5B, the patch is attached to the inside 105 of the main member 110.

[0123] In Figures 5A and 5B, the intermediate structural member is slightly heavier than the upper structural member, and the lower structural member is slightly heavier than the intermediate structural member.

[0124] Figure 5B shows the deformation of the structural member in Figure 5A under a bending load. The bending load may include a force component substantially perpendicular to the bottom 111 of the main member 110.

[0125] The bottom example, i.e., a configuration similar to Figure 3A, was found to be the most beneficial in terms of energy absorption. When the patch is more ductile than the main member, fracture of the main member may be completely avoided, especially in the impact region, and in this example, greater deformation and energy absorption may be possible.

[0126] In the intermediate example, i.e., a configuration similar to Figure 3B, fracture of the main member may not be completely avoided, but it may be substantially reduced. Fracture may also be induced to occur in an area with less danger or risk to the vehicle occupants. Energy absorption may increase compared to the main member without the patch, but it may not be as high as in the lower example.

[0127] When the weights of the structural members in Figures 5A and 5B are normalized so that all structural members have the same weight, the performance of both the intermediate and bottom structural members is satisfactory and (depending on the requirements) superior to the standard structural member made of fully cured material without patches.

[0128] If they have the same weight, both the bottom and middle sections can absorb a similar amount of energy under the same bending load, thus avoiding the problematic fracture of the main member 110, especially in the impact area.

[0129] Throughout this disclosure, terms such as “first” and “second” should not be understood as indicators of order. Similarly, labels in the figures should not be limited to the elements they represent. For example, the “first” patch edge may be any edge of the patch, and the “first” and “second” edges of the patch may be any two distinct edges of the patch.

[0130] Throughout this disclosure, we have referred to "continuous" laser welding. Appropriate laser welding systems can be used, such as gas lasers (e.g., CO2 lasers), diode lasers, and solid-state lasers (e.g., Nd:YAG). Both remote laser welding (where the laser is, for example, half a meter away from the weld) and conventional welding can be used.

[0131] "Continuous laser welding" may be understood throughout this disclosure as a welding technique that uses only a laser for welding. Continuous laser welding may be known to those skilled in the art as laser beam welding. That is, throughout this disclosure, the term continuous laser welding does not cover hybrid laser welding techniques such as, for example, arc-laser hybrid welding. Continuous laser welding does not use welding wire for welding. In continuous laser welding, the laser beam provides a concentrated heat source, enabling narrow and deep welds. High welding speeds and high power densities, for example, on the order of 1 megawatt per square centimeter (MW / cm2), can be obtained.

[0132] While this specification discloses only a number of embodiments, other substitutions, modifications, uses, and / or equivalents are possible. Furthermore, all possible combinations of the embodiments described are also covered. Accordingly, the scope of this disclosure should not be limited by any particular embodiment, but should be determined solely by a fair reading of the subsequent claims.

Claims

1. A structural member (100) for the frame of a vehicle, configured to support a bending load at least partially, A main member (110) having a substantially U-shaped cross-section comprising a bottom (111), a first side wall (112), and a second side wall (113), and having a region configured to support bending loads, A first patch (120) having a first patch edge (121) and a second patch edge (122) located opposite the first patch edge (121), wherein the first patch (120) is attached to the main member (110) by continuous laser welding substantially along the first patch edge (121) and along the second patch edge (122) in a region configured to support at least a bending load, Equipped with A structural member (100) in which the main member (110) is made of hardened steel, and the first patch (120) is made of a material that is more ductile than hardened steel.

2. The structural member (100) according to claim 1, wherein a first patch (120) is attached to a region configured to support a bending load of the main member (110) by continuous laser welding along substantially all edges of the patch.

3. The structural member (100) according to claim 1 or 2, wherein the first patch (120) extends onto the outer or inner surface of the bottom (111), first side wall (112), and second side wall (113) of the main member (110).

4. The structural member (100) according to claim 3, wherein the first patch (120) extends onto the outer or inner surface of the first side wall (112) over at least 10% of the height of the first side wall (112), and the first patch (120) extends onto the outer or inner surface of the second side wall (113) over at least 10% of the height of the second side wall (113).

5. The structural member (100) according to any one of claims 1 to 3, wherein the first patch edge (121) of the first patch (120) substantially extends along the first joint (125) between the first side wall (112) and the bottom (111) of the main member (110), and the second patch edge (122) of the first patch (120) extends along the second joint (126) between the second side wall (113) and the bottom (111) of the main member (110).

6. moreover, A structural member (100) according to claim 1 or 2, comprising a second patch (130) having a first patch edge portion (131) and a second patch edge portion (132) located opposite the first patch edge portion (131), wherein the second patch (130) is attached to the main member (110) by continuous laser welding along the first patch edge portion (131) and the second patch edge portion (132) in a region configured to support a bending load.

7. The structural member (100) according to claim 6, wherein the first patch (120) extends onto the bottom (111) of the main member (110) and the outer or inner surface of the first side wall, and the second patch (130) extends onto the bottom (111) of the main member (110) and the outer or inner surface of the second side wall (113).

8. The structural member (100) according to claim 6, wherein the first patch (120) extends not only on the outer or inner surface of the bottom (111) but also on the outer or inner surface of the first side wall (112), and the second patch (130) extends not only on the outer or inner surface of the bottom (111) but also on the outer or inner surface of the second side wall (113).

9. The structural member (100) according to claim 6 or 7, wherein a first patch (120) substantially extends along a first joint (125) between the first side wall (112) and the bottom (111) of the main member (110), and a second patch (130) substantially extends along a second joint (126) between the second side wall (113) and the bottom (111) of the main member (110).

10. The structural member (100) according to any one of claims 6 to 9, wherein the second patch (130) is made of a material that is more ductile than the hardened steel of the main member (110).

11. A method for manufacturing a structural member (100) that is at least partially configured to support a bending load as described in any one of claims 1 to 10, Step (410) provides a main blank which will be a main member including a region configured to support a bending load, Step (420) of providing at least a first patch blank having a first patch blank edge and a second patch blank edge located on the opposite side of the first patch blank edge, Step (S430) of attaching at least the first patch blank to the main blank by performing continuous laser welding substantially along the first patch blank edge and the second patch blank edge in an area configured to support a bending load, in order to form a patchwork blank which is an intermediate product in which the first patch is attached to the main blank, Step (S440) involves post-processing the patchwork blank to obtain a structural member (100) according to any one of claims 1 to 10, A method that includes this.

12. The method according to claim 11, wherein the post-processing step of the patchwork blank includes hot forming, and the patchwork blank is heated in a furnace before hot forming.

13. The method according to claim 11, wherein the post-processing step of the patchwork blank includes cold forming.

14. The method according to claim 13, wherein the structural member (100) is heat-cured after cold forming.

15. The method according to any one of claims 11 to 14, further comprising using seam tracking during continuous laser welding.

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