Vehicle structural member and method

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, the structural member being configured to at least partially support bending loads. The present disclosure further relates to a method for manufacturing such a structural member. This application claims EP21382108, filed February 11, 2021. [Background technology]

[0002] Vehicles such as automobiles incorporate a structural framework designed to withstand all the loads that the vehicle may be subjected to during its life. The structural framework is further designed to withstand and absorb shocks, for example in the event of a collision with another vehicle. The structural framework also reduces CO2 emissions to the environment. 2 It is designed to be as light as possible to reduce the emission of polluting substances such as

[0003] The structural framework 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 with a substantially U-shaped (also called "hat" shaped) cross section. These structural members may be manufactured in a variety of ways and may be made from a variety of materials. As discussed above, lightweight materials that improve the integrity of the vehicle during a crash as well as improve energy absorption are desired.

[0004] It is generally known in the automotive industry that at least many of the structural components of a vehicle's frame are made from ultra-high strength steels (UHSS), which exhibit optimized maximum strength per unit of weight and advantageous formability properties.

[0005] Ultra-high strength steels (UHSS) in this disclosure may be considered as steels 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 achieve a martensitic structure and corresponding high ultimate tensile strength. Other UHSS can achieve high ultimate tensile strength with relatively slow cooling, or even air cooling ("air hardening"). Some UHSS do not require hot forming and corresponding austenitization to achieve high ultimate tensile strength, but instead have and retain high strength after cold forming.

[0006] UHSS can exhibit high ultimate tensile strengths of 1500 MPa and even 2000 MPa or more, especially after press hardening operations. In such operations, a steel blank is heated above the austenitizing temperature, especially above Ac3, to substantially fully austenitize the blank. After a period of heating above this temperature, the blank is pressed to deform the blank. At the same time, the blank is quenched, substantially "fully hardening" the blank and obtaining a martensitic structure. Press hardening is also called "hot stamping" or, if quenched, "hot formed die quenching" (HFDQ).

[0007] Besides using suitable materials, patch welding can be used to give vehicle structural members suitable properties in terms of crash behavior and weight saving. For example, an initial patch can be welded to a main member to reinforce the main member where necessary without adding undesirable weight. A blank with patches added is sometimes called a "patchwork blank" to distinguish it from a "tailor welded blank", which is a blank joined together by end-to-end welding.

[0008] Typically, the patch is welded to the main component by spot welding, a welding technique that is well known and widely used in the automotive industry, but 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 of ​​the spot welds (e.g., about 25 mm), and the time required to position the plate and the spot welding tool (e.g., about 4 seconds). These distances and times vary depending on the material and thickness of the patch and the workpiece.

[0010] Another disadvantage of spot welding is that it can be very difficult to weld the patch because spot welding is a two-side access technique, meaning the welding gun does not easily have access to the area where the patch is placed.

[0011] In addition, welded pieces and patches (assemblies also called patchwork) may undergo several post-processing steps that may damage or destroy some spot welds due to twisting and bending of the patchwork. Thus, the patchwork may disintegrate. For example, when the patchwork blank is subjected to hot forming, the heat of the furnace (and / or subsequent deformation) may distort the patchwork blank and loosen or break some spot welds. This phenomenon can occur even with careful selection of the number of spot welds joining the patch and the piece.

[0012] There is also a technique called laser welding. Laser welding is typically used to mimic spot welds. A laser stitch is a localized, typically linear, weld. By creating multiple laser stitches, multiple separate welds can be created to mimic the welds of spot welds.

[0013] Document WO2020 / 003900A1 discloses the use of laser welding to join a first plate-like member and a second plate-like member, where a laser stitch is provided longitudinally along a 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. The present disclosure aims to provide an improvement in patch welding technology. Summary of the Invention

[0014] In a first aspect, a structural member for a vehicle frame is provided, the structural member being 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 with a base, a first sidewall, and a second sidewall. The main member further comprises a region configured to support bending loads. The first patch has a first patch edge and an opposing second patch edge. The first patch is attached to the main member by a continuous laser weld substantially along the first patch edge and along the second patch edge, at least in the region configured to support bending loads.

[0015] At least two patch edges joined by a continuous laser weld provide a seamless bond between the patch and the main member in the area of ​​the continuous laser weld, allowing the patch and main member to function as one unit, at least in the area configured to support bending loads.

[0016] The behavior of the structural element in the event of a crash, for example, can thus be improved. The patch and the main element function as one unit, resulting in an increased reinforcement compared to a patchwork welded, for example by spot welding and / or laser stitching. The strength and deformation behavior of the resulting part are improved compared to the same part of the same material and thickness, where the patchwork blank was formed by spot welding.

[0017] Furthermore, continuous laser welding can ensure that the components of the patchwork do not separate at the weld area, for example in the event of a collision as described above.

[0018] Throughout this disclosure, a patch should be understood as a piece of material that, when attached to a main member, is entirely contained within the boundaries of the main member, i.e., the patch may completely overlap the main member or vice versa, allowing the patch and main member to function as one unit after a continuous laser weld has been applied.

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

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

[0021] In particular, automotive framework parts or areas subject to bending loads include the following: the upper or middle A and B pillars, rear rails, the (central longitudinal) tunnel, floor, hinge pillars, rocker areas, and door rings, and the embodiments disclosed herein may be used with these components in particular.

[0022] In some embodiments, the first patch can be attached to the area of ​​the main member configured to support bending loads by laser welding continuously along all edges of the patch, which may further improve the behavior of the patchwork because all edges of the patch are continuously laser welded, thereby enhancing the ability of the patchwork to function as a unitary body.

[0023] Because no minimum distance between spot welds is required, the size of the patch can be further reduced, thus resulting in a lighter structural member.

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

[0025] In certain embodiments, a first patch may extend over a first sidewall by a height of at least 10% of the height of the first sidewall, and a first patch may extend over a second sidewall by a height of at least 10% of the height of the second sidewall. In some embodiments, a first patch may extend over a first and / or second sidewall by at least 25% of the height of the corresponding sidewall, more specifically, between 25-50% of the height of the corresponding sidewall.

[0026] These examples reflect the fact that the greater the extension of the patch on the sidewall of the main member, the greater the reinforcement and the better the patchwork may behave, for example, in a crash.

[0027] In another embodiment, a first edge of the first patch can extend substantially along a first junction of the first sidewall and the bottom of the main member, and a second edge of the first patch can extend along a second junction of the second sidewall and the bottom of the main member.

[0028] In this case, the continuous laser welding of the patches allows for good behavior of the patchwork when the structural member is subjected to bending loads and at the same time allows for significant weight savings.

[0029] In some embodiments, a second patch can be provided having a first patch edge and an opposing second patch edge, the second patch attached to the primary member by a continuous laser weld along the first patch edge and the second patch edge, at least in an area configured to support a bending load.

[0030] Having multiple patches attached to the main member can increase versatility, efficiency, and optimization of the structural member: for example, the number, size, and attachment locations of the patches can be selected to meet the design requirements of the structural member and provide a specific desired kinematic behavior.

[0031] Generally, having multiple patches allows for adequate reinforcement of a structural member where appropriate (i.e., achieving one or more of the aforementioned benefits of continuous laser welding) without unnecessarily increasing the weight of the structural member.

[0032] In some embodiments, the primary member may be made of hardened steel. The first patch and / or the second patch may be made of a material that is more ductile than the hardened steel. By having the patch more ductile than the primary member, fracture of the primary member during an impact may be avoided or may occur only after a significantly higher degree of deformation. When the primary member and the patch are attached by a continuous laser weld, the primary member gains some of the ductility provided by the patch. This increase in ductility of the structural member may be higher than if, for example, the patch is more ductile than the primary member and the patchwork is attached by a typical spot weld, since spot welding does not allow the patchwork to function as a unit.

[0033] Furthermore, the ductility provided by the patch or patches may allow the structural member to absorb more energy in the event of a crash, and therefore may perform better in this respect as well.

[0034] One or more patches, which are more ductile than the primary member and which are welded to the primary member by a continuous laser weld, can simultaneously stiffen the primary member and provide it with deformation and energy absorption capabilities that the primary member, for example a hardened steel piece, may not otherwise have.

[0035] In a further aspect, a structural member for a vehicle frame is provided, the structural member being 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 with a base, a first sidewall, and a second sidewall. The main member further comprises a region configured to support bending loads. The first patch has a first patch edge and an opposing second patch edge. The first patch is attached to the main member by continuous laser welding on an interior side of the first patch, substantially along the first patch edge and along the second patch edge, at least in the region configured to support bending loads.

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

[0037] In some examples, a second patch may be provided having a first patch edge and an opposing second patch edge, the second patch attached to the main member by a continuous laser weld along the first patch edge and the second patch edge on an interior side of the second patch, at least in an area configured to support a bending load.

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

[0039] In another aspect, a method is provided for manufacturing a structural member at least partially configured to support bending loads to obtain a structural member according to the present disclosure.

[0040] The method includes providing a main blank including an area 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 attaching at least the first patch blank to the main blank by continuous laser welding substantially along the first and second patch blank edges or on an interior side of the first patch blank, at least in the area configurable to support a bending load, to form a patchwork blank, and forming the patchwork blank to obtain a structural member as disclosed herein.

[0041] This method can produce structural members with improved behavior as explained above, for example, the method can enable the patchwork created to function as a single unit.

[0042] Generally, this method can provide a faster and easier welding process because, for example, positioning of a spot weld gun to perform each spot weld is avoided and simultaneous access to two weld sides is not required.

[0043] Additionally, there are no considerations regarding minimum overlap distance, minimum distance between spot welds, or number of spot welds.

[0044] In this regard, the method allows for the attachment of a patch along a first juncture between the first sidewall and the bottom of the main member, which may not be possible with spot welding due to the relatively small size of the patch and limitations of the technique, such as the required minimum distance between spot welds and the required minimum spot weld overlap area.

[0045] Continuous laser welding also allows the shape of the patch to be optimized, for example, different patch shapes can be used depending on the design needs, and in this respect there are more options available using this method compared to, for example, spot welding.

[0046] Reducing the size of the patch also reduces the weight of the final structural member. Non-limiting embodiments of the present disclosure are described below with reference to the accompanying drawings. [Brief description of the drawings]

[0047] [Figure 1A] FIG. 1A illustrates generally one example of a vehicle structural member that is at least partially configured to support bending loads. [Figure 1B] FIG. 1B illustrates generally two examples of patch attachment to a main member of a vehicle structural member that is at least partially configured to support bending loads. [Figure 1C] FIG. 1C illustrates generally two examples of patch attachment to a main member of a vehicle structural member configured at least in part to support bending loads. [Figure 2A] FIG. 2A illustrates generally two additional examples of vehicle structural members that are at least partially configured to support bending loads. [Figure 2B] FIG. 2B illustrates generally two additional examples of vehicle structural members that are at least partially configured to support bending loads. [Figure 3A] FIG. 3A illustrates generally two further examples of vehicle structural members that are at least partially configured to support bending loads. [Figure 3B] FIG. 3B illustrates generally two further examples of vehicle structural members that are at least partially configured to support bending loads. [Figure 4] FIG. 4 is a flow chart of a method for manufacturing a structural member configured at least in part to support a bending load. [Figure 5A] FIG. 5A is a schematic diagram illustrating examples of structural members and how they may deform under bending loads. [Figure 5B] FIG. 5B is a schematic diagram illustrating examples of structural members and how they may deform under bending loads. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] The figures depict exemplary embodiments and are merely used as an aid in understanding the claimed subject matter and are not intended to be limiting in any sense.

[0049] 1A is a schematic representation of a structural member for a vehicle configured at least in part to support bending loads. The structural member 100 comprises a main member 110 having a substantially U-shaped cross-section with a base 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 the vehicle frame may generally be subjected to a variety of loads. The loads may result from the weight of the structure, acceleration and deceleration of the vehicle, vibrations caused by travel, and many other factors. However, specific structural members must be designed and certified for specific behavior in case of specific loading situations, e.g., collisions and impacts with utility poles, pedestrians, and other vehicles. Some structural members are expected to be subjected to bending loads (e.g., bumpers and pillars) and are specifically designed to withstand such bending loads. Other structural members (e.g., crash boxes) are expected to be subjected to compressive loads instead and are specifically designed to withstand such loads.

[0051] A structural member of a vehicle frame, such as an automobile, may be subjected to bending loads throughout its entirety. However, there are structural members that are expected to be subjected to bending loads only in certain parts or regions thereof, or the structural members 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. It is along these areas where bending loads are important that the patchwork blanks or patchworks provided herein are most useful.

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

[0053] In this and other figures, the main member is shown as having a "hat" or "U" shaped cross section. It will be apparent that in all of these examples, the components or main members may include side flanges extending outwardly 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 an opposing second patch edge 122. The first patch 120 is attached to the main member 110 by a continuous laser weld along the first patch edge 121 and the second patch edge 122, at least in an area configured to support the bending load 114.

[0055] The first patch 120, in this and other embodiments, is attached to the inside 105 of the main member 110 (patch represented by dashed lines), i.e., the patch is attached to the main blank and the patchwork blank is deformed so that the patch is located on the inside of the U. The first patch 120 may be attached to the outside 107 of the main member 110 in other embodiments, as shown diagrammatically in Figure 2B.

[0056] In this 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, the patch edges 121, 122 may extend in other directions.

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

[0058] Attaching the first patch 120 to the main member 110 by continuous laser welding at least in the area configured to support the bending load 114 allows the patchwork to function as a single entity in the area configured to support the bending load 114. Thus, reinforcement of the main member 110 by attachment of the patch 120 may be improved with respect to other techniques, such as, for example, spot welding, where a seamless bond between the first patch 120 and the main member 110 is not feasible.

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

[0060] Additionally, while spot welding has limitations as discussed above (e.g., certain minimum distances required between spot welds), this embodiment allows the size of patch 120 to be reduced, thereby reducing the weight of structural member 100.

[0061] In some embodiments, all edges of the patch 120 are attached to the main member 110 by a continuous laser weld, at least in the areas configured to support the bending load 114. In one embodiment, such as in FIG. 1B, there may be one or more discontinuities in the attachment along the periphery of the patch 120. Such small discontinuities generally do not adversely affect the functionality and benefits provided by the present disclosure, unless they are located in areas subject to impact or high bending loads. In another embodiment, as shown in FIG. 1C, the attachment is made along the entire periphery of the patch 120 such that there are no discontinuities in the attachment.

[0062] This increases the level of refinement and reinforcement achieved: attaching the main member 110 and the first patch 120 by performing continuous laser welding along the four edges of the first patch 120, and in particular along the entire circumference of the first patch 120 as shown in FIG. 1C, enhances the advantages commented upon herein.

[0063] As used herein, "all around" should be understood to refer to substantially no discontinuities in the application, as in Figure 1C. This is in contrast to the situation in Figure 1B, where attachment occurs along the perimeter of the patch, but where there are one or more discontinuities in the attachment.

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

[0065] 1A as being rectangular, 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 sidewall 112 and / or the second sidewall 113. In some examples, such as in Figures 2A and 2B, the first patch 120 extends over the bottom and both sidewalls 111, 112, 113. In other examples, such as in Figures 3A and 3B, the patch extends over the bottom and one of the sidewalls 112, 113.

[0067] It is also conceivable that further patches are attached to the main member, see for example figures 3A and 3B. If more than one patch is present, it is not excluded that there may be an overlap of any of them.

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

[0069] It should be understood that the region 114 configured to support a bending load is a region that is arranged or set to serve the purpose of supporting a bending load. Prior to the arrangement or setting, the region 114 may be designated a region that is configurable to support a bending load (not shown). This arrangement or setting may consist, for example, of subjecting the region that is configurable to support a bending load to any method, such as hot forming.

[0070] The first patch 120 may overlap partially or completely with the region 114 configured to support bending loads. The first patch 120 may not overlap partially or completely 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 in the main member 110 that is not configured to support bending loads, as opposed to the region 114. That is, this may be an area of ​​the part that is not expected to be subjected to bending loads in normal use. This portion can be used to join the part to other portions of the vehicle framework.

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

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

[0073] Additional attachments may also be made between elements 110 and 120 outside of the area configured to support bending loads 114. For example, main member 110 and first patch 120 may be attached via spot welds and / or continuous laser welds in areas not configured to support bending loads.

[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] FIG. 1A shows what are understood as a “height” 117 , a “width” 115 and a “length” 116 for the dimensions of main member 110 .

[0076] Although depicted as being substantially straight, the base 111, the first sidewall 112 and the second sidewall 113 are not necessarily straight. For example, the base 111 may be curved or curved in any manner. This also applies to the sidewalls 112, 113. Each element 111, 112, 113 may have a curvature or bend that is equal to or different from the curvature or bend of any of the other elements 111, 112, 113. Additionally, the sidewalls 112, 113 do not have to be symmetrical.

[0077] For example, the height of the first sidewall 112 may be different than the height of the second sidewall 113. For example, the height 117 along the length 116 of the first sidewall 112 and / or the second sidewall 113 may also be different. For example, the width 115 of the base may be different than the height 117 of the first sidewall 112 and / or the second sidewall 113. Other examples may include any combination of the above examples. The only limitation is that one skilled in the art may recognize that the main member 110 has a substantially U-shaped cross-section.

[0078] 2A and 2B are schematic diagrams of a vehicle structural member 100 at least partially configured to support bending loads, according to an embodiment. In FIG. 2A and 2B, a first patch 120 extends over a bottom 111, a first sidewall 112, and a second sidewall 113 of a main member 110. The first patch 120 is attached by a continuous laser weld to at least the area of ​​the main member 110 configured to support bending loads 114, in any of the ways shown above with respect to FIG. 1. Thus, both configurations of the patch 120 and the main member 110 benefit from the effect of attaching the patch 120 and the main member 110 by a continuous laser weld.

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

[0080] Due to the continuous laser welding, the resistance of the patchwork to damage caused by bending loads, such that the patchwork would disintegrate, is in this case higher than in configurations that differ from the configuration shown in Figure 2A only in the type of attachment method used, such as, for example, spot welding and / or laser seam welding.

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

[0082] This configuration makes it possible to reduce the weight of the structural member 100 while also enabling the structural member 100 to be reinforced and the risk of fracture to be reduced when subjected to a bending load.

[0083] In particular, limitations of spot welding as commented herein do not allow welding as close to the junctions 125, 126 of the bottom 111 and side walls 112, 113 as continuous laser welding can, potentially resulting in greater weight savings than would be possible using spot welds, for example. In some examples, the dimensions of patch 120 in a direction substantially perpendicular to the length 116 of main member 110 (and in a direction substantially parallel to the height 117 and / or width 115 of main member 110) may be reduced by at least 5 mm, and optionally at least 10 mm, for each side 121, 122 of patch 120 relative to a patch that is spot welded to main member 110.

[0084] Similar considerations apply to FIG. 3B , where the first patch 120 extends substantially along a first junction between the first sidewall 112 and the bottom 111 of the main member 110, and the second patch 130 extends substantially along a second junction between the second sidewall 113 and the bottom 111 of the main member 110.

[0085] The configuration of FIG. 3B includes the advantages discussed in relation to FIG. 2B, and further includes the advantage of reduced weight.

[0086] As previously mentioned, any number of patches extending across any of the side walls 112, 113 and / or bottom 111 of the main member 110 may be selected depending on design criteria relating to, for example, the need for reinforcement, resistance to bending loads, resistance to bursting hazards, and / or weight of the structural member 100.

[0087] Further, in any of the embodiments illustrated herein, the first patch 120 and / or the second patch 130 may be made of a more ductile material 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 forming process, 22MnB5 is sometimes coated with an aluminum-silicon coating. The composition of 22MnB5 is summarized below by weight (the remainder is 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] There are several commercially available 22MnB5 steels with similar chemical compositions, but the exact amounts of each component in 22MnB5 steel may vary slightly depending on the manufacturer. Other ultra-high strength steels include BTR165, available from Benteler.

[0090] Usibor® 1500 is supplied in the ferrite-pearlite phase. This is a fine grain structure distributed in a homogeneous pattern. The mechanical properties are related to this structure. After heating, the hot stamping process and subsequent quenching, a martensitic microstructure is formed. This results in significantly improved ultimate strength and yield strength.

[0091] The composition of Usibor® 1500 by weight is as follows (the remainder is iron (Fe) and inevitable 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 higher strength boron steel. The yield strength of Usibor® 2000 can be greater than 1400 MPa and the ultimate tensile strength can be greater than 1800 MPa after hot press die quench. The composition of Usibor® 2000 includes max 0.37 wt% carbon, max 1.4 wt% manganese, max 0.7 wt% silicon and max 0.005 wt% boron.

[0093] On the other hand, Ductibor® and other mild steels can also be used for hot forming and hot forming die quenching. However, these steels do not form martensitic structures. The resulting steels have lower ultimate tensile strength and yield strength, but higher elongation to break.

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

[0095] CRL-340LA is a steel material marketed by SSAB. It is a high-strength, low-alloy steel intended for general pressing, bending and forming applications. Its composition (wt%) is as follows: C 0.1% or less Si 0.040% or less Mn 1% or less P 0.030% or less S max 0.025 Aluminum 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 suitable mechanical properties after such processing. Ductibor®, CRL-340LA and similar steels, e.g., low alloy steels, are suitable for the "softer" patch.

[0097] The combination of soft patches and "hard" main members allows the structural member 100 to absorb more energy, for example in the event of a crash. Another advantage is that fracture of the main member 110 when subjected to bending loads 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 due in particular to the effect that the patches 120 , 130 are attached by continuous laser welding, which makes the patches 120 , 130 more ductile than the main member 110 .

[0099] That is, if the patches 120, 130 are more ductile than the main member 110 and are attached by spot welds in areas where the patchwork is configured to support bending loads 114, the properties of the structural member 100 will generally not be as good as with continuous laser welding, since the patchwork does not function as a single integral unit. Particularly in the event of an impact and corresponding bending load, localized deformations will occur between the spot welds, and these deformations can result in localized fracture.

[0100] Similarly, if the patches 120, 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 bending loads 114, the properties of the structural member 100 may generally not be as good as with patches 120, 130 that are more ductile than the main member 110, because the patchwork is generally less ductile than the main member 110.

[0101] 4 illustrates a method 400 for manufacturing a structural member 100 at least partially configured to support bending loads as disclosed herein, such as the structural member 100 of FIGs. 1A, 2A, 2B, 3A, or 3B. The structural member 100 may include one or more patches 120 attached as in FIGs. 1B or 1C, or may be of other configurations as disclosed herein.

[0102] The method includes a step 410 of providing a main blank that includes a region configurable to support a bending load.

[0103] The method further includes providing 420 at least a first patch blank having a first patch blank edge and an opposing second 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 a first patch blank can have, for example, the same or different sizes, shapes and / or materials.

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

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

[0107] Generally, the main blank and at least the first patch blank will be substantially planar, however, this is not always the case, for example, the main blank and / or at least the first patch blank may be curved in some manner.

[0108] The method further includes attaching 430 at least a first patch blank to the main blank by substantially continuous laser welding along the first and second patch blank edges, particularly along all edges of the patch, at least in an area configured to support a bending load, to form a patchwork blank. One or more discontinuities may be provided in the attachment of the at least first patch blank.

[0109] As explained above, continuous laser welding allows the patchwork blank to function as a single integral piece.

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

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

[0112] Forming can include any type of forming such as hot forming or cold forming. Forming not only gives the patchwork its shape, but may also impart additional properties such as increased strength to the patchwork by changing the microstructure of the steel, as with hot forming.

[0113] Hot forming can involve heating the patchwork blank above the austenitizing temperature, specifically above Ac3, for a minimum period of time, such as several minutes. The patchwork blank is then transferred to a press where the blank is deformed to form the part while simultaneously quenching to below 400°C, specifically below 300°C. If a hardenable steel is used for the main component and a softer steel is used for the patch, the main component will have a high ultimate tensile strength but will itself be relatively brittle and will have little elongation to break, whereas the patch material will be more ductile and will have a greater elongation to break.

[0114] In some instances, forming and other subsequent processes such as notching, trimming, calibration, etc. may be performed in a multi-stage apparatus combining different stations on the same press.

[0115] The same or similar steels as described above may be used. In some instances, a hardenable steel main blank may be zinc coated. In some embodiments, the steel may be hardened to obtain a martensitic structure, while in other embodiments, the steel may be air hardenable or nearly air hardenable.

[0116] If cold forming is used, in some instances after forming the part may be heated in a furnace and heat treated, including quenching, to achieve the desired structure and corresponding mechanical properties.

[0117] This method can also provide a further improvement in that it allows for the attachment of a patch blank along a first juncture between the first side wall and the bottom of the main member blank, as in FIG. 3B, which may not generally be possible with spot welding due, for example, to the relatively small size of the patch and the requirements for minimum distance between spot welds and minimum spot weld overlap area required.

[0118] This also means that the desired effect associated with the patches 120, 130, e.g. reinforcement, may be achieved with a smaller size of the patches 120, 130, thus resulting in a lighter structural member 100.

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

[0120] The thickness of the patch blank can also be selected as needed.

[0121] The method may include additional steps or operations, such as using seam tracking for efficient continuous laser welding.

[0122] Figures 5A and 5B show schematics of U-shaped members and how they deform under bending loads. The first example at the top is a fully stiffened beam, the second example in the middle is of a stiffened main member with a soft patch similar to the example in Figure 3B, and the third example at the bottom is of a stiffened 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 middle structural member is slightly heavier than the top structural member, and the bottom structural member is slightly heavier than the middle structural member.

[0124] 5B illustrates the deformation of the structural member of FIG. 5A under a bending load, which 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. If the patch is more ductile than the main member, fracture of the main member may be avoided entirely, especially in the impact area, allowing for greater deformation and energy absorption in this example.

[0126] For the intermediate example, i.e., a configuration similar to Figure 3B, failure of the main member may be substantially reduced, if not completely avoided. Failure may also be induced to occur in an area that poses less danger or risk to vehicle occupants. Energy absorption may be increased relative to the unpatched main member, but may not be as high as in the bottom example.

[0127] If 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 middle structural member and the bottom structural member is satisfactory and (depending on the requirements) better than a reference structural member of fully cured material without the patch.

[0128] With the same weight, both the bottom and middle configurations can absorb the same amount of energy under the same bending load, avoiding problematic fracture of the main member 110, especially in the impact area.

[0129] Throughout this disclosure, terms such as "first" and "second" are not to be understood as indications of order. Similarly, labels in figures do not limit the elements to which they are attached. That is, for example, a "first" patch edge may be any edge of the patch, and the "first" and "second" edges of a patch are any two distinct edges of the patch.

[0130] Throughout this disclosure, reference has been made to "continuous" laser welding. 2 Any suitable laser welding system can be used, such as a laser, diode laser or solid-state laser (e.g. Nd:YAG). Both remote laser welding (where the laser has a distance of e.g. half a meter to 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 arc-laser hybrid welding. Continuous laser welding does not use a welding wire for welding. In continuous laser welding, the laser beam provides a concentrated heat source, allowing 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 only a number of embodiments have been disclosed herein, other alternatives, modifications, uses and / or equivalents are possible. Moreover, all possible combinations of the described embodiments are covered. Thus, the scope of the disclosure should not be limited by any particular embodiment, but should be determined solely by a fair reading of the claims that follow.

Claims

1. A structural member (100) for a vehicle frame configured to at least partially support bending loads, comprising: a main member (110) having a substantially U-shaped cross-section with a base (111), a first side wall (112) and a second side wall (113), the main member having an area configured to support a bending load; a first patch (120) having a first patch edge (121) and an opposing second patch edge (122), the first patch (120) being attached to the main member (110) by a continuous laser weld on an inside of the first patch (120) substantially along the first patch edge (121) and along the second patch edge (122), at least in an area configured to support bending loads; Equipped with A structural member (100) having a main member (110) made of hardened steel and a first patch (120) made of a material that is more ductile than hardened steel.

2. 2. The structural member (100) of claim 1, wherein the first patch (120) is attached to the main member (110) in an area configured to support bending loads by a continuous laser weld on an interior side of the first patch (120) substantially along all edges of the patch.

3. 3. The structural member (100) of claim 1 or 2, wherein the first patch (120) extends across the bottom (111), the first sidewall (112) and the second sidewall (113) of the main member (110).

4. 4. The structural member (100) of claim 3, wherein the first patch (120) extends over the first side wall (112) by at least 10%, optionally at least 25%, in particular between 25% and 50% of the height of the first side wall (112) and the first patch (120) extends over the second side wall (113) by at least 10%, optionally at least 25%, in particular between 25% and 50% of the height of the second side wall (113).

5. 4. A structural member (100) as claimed in any one of claims 1 to 3, wherein a first edge of the first patch (120) extends substantially along a first junction (125) between the first sidewall (112) and the bottom (111) of the main member (110) and a second edge of the first patch (120) extends along a second junction (126) between the second sidewall (113) and the bottom (111) of the main member (110).

6. moreover, 3. The structural member (100) of claim 1 or 2, comprising a second patch (130) having a first patch edge (131) and an opposing second patch edge (132), the second patch (130) being attached to the main member (110) by a continuous laser weld on an inside of the second patch (130) along the first patch edge (131) and the second patch edge (132), at least in an area configured to support bending loads.

7. 7. The structural member (100) of claim 6, wherein the first patch (120) extends over the bottom (111) and the first sidewall (113) of the main member (110) and the second patch (130) extends over the bottom (111) and the second sidewall (113) of the main member (110).

8. 7. The structure (100) of claim 6, wherein the first patch (120) extends over the first sidewall (112) further above the bottom (111) and the second patch (130) extends over the second sidewall (113) further above the bottom (111).

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

10. A structural member (100) as described in any one of claims 1 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) at least partially configured to support bending loads according to any one of claims 1 to 10, comprising the steps of: Providing (410) a main blank including an area configured to support a bending load; Providing (420) at least a first patch blank having a first patch blank edge and an opposing second patch blank edge; Attaching at least a first patch blank to the main blank by performing continuous laser welding on an inside of the first patch blank substantially along the first patch blank edge and the second patch blank edge, at least in an area configured to support a bending load (S430), to form a patchwork blank; forming a patchwork blank (S440) to obtain a structural element (100) according to any one of claims 1 to 10; The method includes:

12. The method of claim 11 , wherein the step of forming the patchwork blank comprises hot forming, and optionally the patchwork blank is heated by a furnace prior to hot forming.

13. The method of claim 11 , wherein the step of forming the patchwork blank comprises cold forming.

14. The method of claim 13, wherein the structural member (100) is heat set after cold forming.

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

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