Manufacturing process for producing a metal part, metal part and motor vehicle

Description

1 / 30 “MANUFACTURING PROCESS FOR PRODUCING METAL PARTS, METAL PARTS AND MOTOR VEHICLES”

[001] The present invention relates to a process for manufacturing a metal part and the associated metal part. In particular, it relates to the manufacture of complex metal parts, in which the shaping is carried out by stamping.

[002] There is a growing demand in the metal parts manufacturing industry, particularly in the automotive parts manufacturing industry, to produce parts with increasingly complex shapes. This allows, for example, the integration of several separate individual parts into a single piece. This streamlines the production process: only one forming operation replaces the combination of several separate forming operations to produce the individual sub-parts and the corresponding joining process to assemble said individual sub-parts. This also allows for improved part performance, as the assembly points between the individual sub-parts are often weak points that can fail under load, for example, in the event of a collision in the case of automotive parts. Furthermore, simplifying the production process brings other positive effects, such as reducing greenhouse gas emissions during forming and reducing costs.

[003] Stamping is a well-known technique for forming sheet metal that consists of pressing a flat sheet of metal between an upper and a lower die, usually with the shape of the metal part being formed. These dies move relative to each other in a direction called the stamping direction.

[004] During stamping, the pressurized metal flows under the combined forces exerted by the upper and lower dies. Generally, it is not possible to stamp a part if there are abrupt transitions in the direction in which Petition 870250110840, dated 03 / 12 / 2025, page 10 / 61 2 / 30 the metal flows. In fact, in areas where these abrupt transitions occur, the sheet metal needs to flow in two distinct directions, which leads to very high strain rates, excessive thinning, and eventually, cracking. In some cases, this also leads to wrinkling of the part.

[005] This limits the diversity of shapes accessible by the traditional stamping process. Japanese patent application JP 2007029966 provides a first solution for the manufacture of complex metal parts by stamping. The proposed solution is to provide a metal blank that is an assembly of several partially overlapping blank sub-parts, such that the blank sub-parts can move relative to each other in the overlapping regions during stamping. Thus, in areas where the metal blanks need to flow in two distinct directions, each of the two overlapping blank sub-parts is free to move in said distinct directions, apparently solving the problem of excessive thinning, cracking, and wrinkling.

[006] However, the inventors encountered serious problems of thinning, cracking and excessive bending when trying to apply the teachings of document JP 2007029966 in practice, as will be demonstrated in the examples below.

[007] One objective of the present invention is to provide a metal forming process that allows stamping complex shapes in which the sheet metal needs to flow in several distinct directions without excessive thinning, cracking, or bending. A further objective of the present invention is to provide a part manufactured according to the inventive process and possessing a complex shape, not achievable using the stamping technology of the current state of the art.

[008] The objective of the present invention is achieved by applying a parts manufacturing process according to claim 1, Petition 870250110840, dated 03 / 12 / 2025, page 11 / 61 3 / 30 optionally comprising the features of claims 2 to 14, taken individually or in any possible combination. The present invention also relates to a metal part according to claim 15, optionally comprising the features of claims 16 or 17, taken individually or in any possible combination. The present invention also relates to a motor vehicle according to claim 18.

[009] Other aspects and advantages of the invention will become apparent after reading the following description, given by way of example and made with reference to the accompanying drawings, which are by no means limiting, in which: Figure 1 is a perspective view of a specific embodiment of a metal part for which the present invention provides a manufacturing process. Figure 2 is a top view of a flexible raw piece according to the present invention. Figure 3A is a top view of a punch and binder of a stamping tool according to the state of the art. Figure 3B is a top view of a punch and binder of a stamping tool according to the invention. Figure 4 is a perspective view of the beginning of a stamping operation according to the present invention - for clarity, the upper die is not shown in this figure. Figure 5 is a perspective view of the same stamping operation as in Figure 4, this time representing the end of the stamping operation. Figure 6A is a top view of a punch and binder of a stamping tool according to the invention. Figure 6B is a top view of a tool. Petition 870250110840, dated 03 / 12 / 2025, p. 12 / 61 4 / 30 conformation according to a particular embodiment of the present invention, Figure 7 is a perspective view of another embodiment of a metal part for which the present invention provides a manufacturing process. Figure 8 is a perspective view of another embodiment of a metal part for which the present invention provides a manufacturing process. Figure 9A is a perspective view of a metal part formed using state-of-the-art techniques. Figure 9B is a perspective view of a metal part formed using state-of-the-art techniques. Figure 9C is a perspective view of a metal part formed according to the present invention. Figure 10A is a cross-section of a flexible blank according to a specific embodiment of the invention, taken along the cutting line AA shown in Figure 2. Figure 10B is a cross-section of a metal part according to one embodiment of the invention, taken along the cutting line BB shown in Figure 8. Figure 11 is a perspective view of a specific embodiment of a metal part for which the present invention provides a manufacturing process.

[010] In the following figures and descriptions, spatial orientations and references are all made using X, Y, and Z coordinates associated with the following directions: - X is a longitudinal direction in the horizontal plane, with the axis X oriented so that the X coordinates increase in the direction from the front to Petition 870250110840, dated 03 / 12 / 2025, p. 13 / 61 5 / 30 backwards, meaning a position located further back will have a larger X-coordinate than a position located further forward. Y is a transversal direction in the horizontal plane. Z is a direction of elevation, with the Z-axis oriented so that the Z coordinates increase from a lower to a higher position; that is, a first position located below a second position will have a lower Z coordinate value.

[011] The reference frame is represented in each figure. When the figure is a 2D planar representation, the axis that is outside the figure is represented by a point in a circle when it points towards the reader and by a cross in a circle when it points away from the reader, following established conventions.

[012] In particular, the terms “top”, “above”, “upper”, “above”, “lower”, “below”, “below”, etc. are defined according to the direction of elevation. The terms “front”, “rear”, “back”, “forward”, “backward”, etc. are defined according to the longitudinal direction. The terms “left”, “right”, “transverse”, etc. are defined according to the transverse direction. The term “horizontal” refers to the orientation of the plane that includes both the longitudinal and transverse directions. The term “vertical” refers to any orientation that includes the direction of elevation.

[013] By “substantially parallel” or “substantially perpendicular” is meant a direction that may deviate from the parallel or perpendicular direction by no more than 15°.

[014] A metal sheet refers to a flat sheet of steel. It has an upper and a lower face, which are also referred to as the top and bottom sides or the top and bottom surfaces. The distance between these faces is designated as the thickness of the sheet. The thickness can be measured, for example, with a micrometer, whose spindle and anvil are Petition 870250110840, dated 03 / 12 / 2025, p. 14 / 61 6 / 30 positioned on the top and bottom faces. Similarly, thickness can also be measured on a formed part.

[015] The average thickness of a part, or of a portion of a part, is understood to be the total average thickness of the material that makes up the part after it has been formed into a three-dimensional part from an initially flat sheet.

[016] Custom welded blanks are made by assembling, for example by laser welding, several sheets or cut blanks of steel, known as blank sub-pieces, to optimize the performance of the part in its different areas, reduce the overall weight of the part, reduce the overall cost of the part and reduce material scrap. The blank sub-pieces that form the custom welded blanks can be assembled with or without overlap, for example, they can be butt laser welded (without overlap) or they can be spot welded to each other (with overlap).

[017] A flexible blank is a combination of several blank sub-parts that includes overlapping regions, allowing the blank sub-parts to move in different directions during the forming operation.

[018] In contrast to a custom welded blank, a monolithic blank refers to a blank that consists of a single blank subpiece, without multiple blank subpieces being combined.

[019] A custom rolled blank is a blank with various sheet thicknesses obtained by differential rolling during the steel sheet production process.

[020] Maximum tensile strength, yield strength, and elongation are measured according to ISO 6892-1, published in October 2009. Tensile test specimens are cut from flat areas. If necessary, small-sized tensile test samples are collected. Petition 870250110840, dated 03 / 12 / 2025, page 15 / 61 7 / 30 to accommodate the total flat area available on the piece.

[021] The bending angle is measured according to the VDA-238 bending standard. For the same material, the bending angle depends on the thickness. For simplicity, the bending angle values ​​of the present invention refer to a thickness of 1.5 mm. If the thickness is different from 1.5 mm, the bending angle value needs to be normalized to 1.5 mm by the following calculation, where α1.5 is the bending angle normalized to 1.5 mm, t is the thickness, and αt is the bending angle for thickness t: Equation 1 α1,5 = (at χ Vt) / Vl ,5.

[022] Cold stamping is a metal forming technology that involves shaping a sheet metal into a formed part by pressing it between an upper and lower die, called a cold stamping tool. For example, the cold stamping tool has a blank holder that allows it to hold the sheet metal on its sides. For example, the cold stamping tool consists of several stages, each involving an upper and lower die to produce complex shapes and / or perform other operations, such as punching holes in the part or trimming its sides.

[023] Hot stamping is a steel forming technology that involves heating a steel blank, or a pre-formed part made from a steel blank, to a temperature at which the microstructure of the steel has at least partially transformed into austenite, forming the blank or pre-formed part at high temperature, stamping it and simultaneously tempering the formed part to obtain a microstructure with very high strength, possibly with an additional step of parting or quenching in the heat treatment.

[024] A multi-stage hot stamping process Petition 870250110840, dated 03 / 12 / 2025, page 16 / 61 8 / 30 is a particular type of hot stamping process that includes at least one stamping step and consists of at least two process steps performed at high temperatures, above 300 °C. For example, a multi-step process might involve an initial stamping operation and a subsequent hot cutting operation, so that the finished part, upon exiting the hot stamping process, does not require further trimming. For example, a multi-step process might involve several successive stamping steps to manufacture parts with more complex shapes than can be obtained using a single stamping operation. For example, parts are automatically transferred from one operation to another in a multi-step process, for instance, using a transfer press.For example, the parts remain in the same tool, which is a multi-functional tool that can perform different operations, such as an initial stamping and a subsequent cutting operation in the tool.

[025] A partial hardening hot stamping process is a hot stamping process in which the thermal profile to which the blank is subjected is purposefully tailored to be different in different areas of the blank in order to obtain different material properties in those different areas at the end of the hot stamping process. For example, this allows producing hot stamped parts using a single metallic blank made of a single material that will have different levels of hardness and elongation in different areas of the final part. For example, this allows producing parts with soft zones and hard zones, the said soft zones being able to deform under an impact load to absorb energy, while the said hard zones will resist intrusion by resisting deformation. There are several different technologies for implementing partial hardening. For example, the material can be heated to different temperatures. Petition 870250110840, dated 03 / 12 / 2025, page 17 / 61 9 / 30 temperatures in different areas of the blank, the higher temperature areas will be fully austenitic at the exit of the austenitizing furnace, resulting in a very hard microstructure after hot stamping, while the lower temperature areas will have an intercritical ferrite / austenite microstructure at the exit of the austenitizing furnace, resulting in a lower hardness microstructure after hot stamping. For example, the material can be quenched at different quenching speeds in different areas of the blank during the hot stamping step itself; the areas quenched at a higher quenching speed will have a higher hardness than those quenched at a lower speed.

[026] Referring to Figures 1 and 11, it is an object of the present invention to manufacture a metal part (1) comprising at least the following sub-parts: - a first subpart (11) generally extending along a first direction (D1). In the remainder of the description, this first direction will conventionally be chosen as the longitudinal direction.The aforementioned first direction is perpendicular to a stamping direction (S), which will be conventionally chosen in the present description as the elevation direction, and comprises at least one first side wall (111) (in the case of Figure 1, there are two side walls (111 and 112)), substantially parallel to said stamping direction, and a first upper section (113) connected to at least said first side wall (111), and generally extending in a plane perpendicular to said stamping direction (S), - a second subpart (12) connected to said first subpart (11) and generally extending along a second direction (D2), also perpendicular to said stamping direction and forming with said first direction an angle α strictly greater than 0°, comprising at least two vertical walls (121 and 122). Petition 870250110840, dated 03 / 12 / 2025, p. 18 / 61 10 / 30 substantially parallel to said stamping direction, and a second upper section (123), connecting said two vertical walls (121, 122), generally extending in a plane perpendicular to said stamping direction.

[027] The metal part (1) shown in Figure 1 is a particular embodiment in which the sub-parts are generally omega-shaped, with straight vertical walls and flat, straight upper sections. However, this is not limiting to the invention; the sub-parts may, for example, have a curved cross-section in the shape of an inverted U, i.e., curved vertical walls and an upper section limited to a two-dimensional line. This is, for example, the case of the first sub-part (11) of the metal part (1) shown in Figure 11.

[028] In one particular embodiment, the angle α between the two principal directions (D1, D2) of the subpieces (11, 12) is between 30° and 90°, more specifically between 60° and 90°, and even more specifically between 80° and 90°.

[029] When shaping the metal part (1) by stamping a flat metal blank along the stamping direction (S), the first vertical wall (111) is formed by the flow of material in the direction (F1), transverse to (D1), as shown in Figure 1. If the first sub-part (11) also contains a second vertical wall (112), it is formed by a flow of material in the direction (F1'). Simultaneously, the material flows in the opposite directions (F2) and (F2'), both transverse to (D2), to form the vertical walls (121 and 122) of the second sub-part (12). In the transition regions (11T12) between the sub-parts (11 and 12), the material must flow simultaneously in the directions (F1) and (F2) or in the directions (F1) and (F2'). The angle between the aforementioned directions will be α or its complement to 180°, and since α is strictly greater than 0°, this leads to a simultaneous flow of material in different directions, which overloads the material, leading to excessive thinning and, Petition 870250110840, dated 03 / 12 / 2025, page 19 / 61 11 / 30 eventually, to the formation of cracks in the transition regions.

[030] This is illustrated by Figure 9A, which is an example of a stamping simulation of a metal part corresponding to the description above, in which cracks (6) appear in the transition regions (11T12) due to the concurrent deformation directions described above.

[031] A first part of the solution for manufacturing a metal part according to the invention consists in using a flexible blank (10), as illustrated in Figure 2. Said flexible blank (10) comprises at least: - two raw sub-pieces (101, 102), each corresponding substantially, respectively, to the aforementioned first and second sub-pieces (11, 12), - at least one overlapping area (100) in which the said raw sub-pieces (101, 102) overlap each other, - said overlapping area (100) comprising at least one sliding area (1001) in which said blank sub-parts (101, 102) are free to slide over each other during said stamping operation and a fixed pre-assembly area (1002) in which said blank sub-parts cannot move relative to each other during the stamping operation.

[032] During the stamping operation, the area of ​​the flexible blank corresponding to the transition regions (11T12), where cracking normally occurs, becomes double-layered thanks to the presence of the overlapping region (100), and both layers are free to slide over each other, thus avoiding the problem described above of excessive thinning and cracking due to contradictory material flow directions. For example, in the configuration of Figure 1, the blank subpiece material (101), corresponding to the vertical wall (111), will be free to move. Petition 870250110840, dated 03 / 12 / 2025, page 20 / 61 12 / 30 in direction (F1), while the raw sub-piece material (102), corresponding to the vertical walls (121 and 122), will be free to move in directions (F2) and (F2').

[033] The inventors discovered that, surprisingly, providing only the flexible blank described above is not sufficient to manufacture a metal part free from stamping defects in the transition regions (11T12). Figure 9B is an exploded view of the result of performing a stamping operation on a flexible blank as described above. The sub-parts (11 and 12) were disassembled to highlight the forming problems encountered. As can be seen, cracks (6) appear in both the first and second sub-parts (11, 12).

[034] The inventors discovered that it was possible to stamp a metal part according to the invention, by modifying the stamping process.

[035] A stamping tool generally comprises a punch and a die. The die can be seen as a mold in which the part will be shaped, while the punch is used to transfer the shape of the part onto the blank by pressing it against the die in the stamping direction. A stamping tool may optionally also comprise a binder, also known as a blank holder, which is used to hold the blank in place during stamping and thus control the material flow to achieve a good quality shape.

[036] Figure 3A is a top view of a punch (2) and a binder (3), according to the state of the art. Referring to Figure 3B, the inventors found that, surprisingly, it was possible to solve the problem of cracking in the transition zones by using a flexible blank, providing a punch (2) with a gap (4) between the punch areas. Petition 870250110840, dated 03 / 12 / 2025, p. 21 / 61 13 / 30 corresponding to the first sub-piece (11) and the second sub-piece (12).

[037] Figure 9C is an example of a stamping simulation of a flexible raw part, according to the invention, using a stamping tool according to the invention, i.e., with a clearance (4) between the punch areas (3) corresponding to the first and second sub-parts. No cracks were observed in the transition areas (11T12) in this last simulation.

[038] In a specific embodiment, the inventors found that the required length of said clearance (4) (i.e., the distance (g) indicated in Figure 3B) is linked to the height of the vertical walls of the two contiguous subpieces in the corresponding transition region (11T12). In fact, the reason why cracking occurs when there is no clearance is linked to the material flow to form said vertical walls, and the amount of material flow is linked to the height of said vertical walls. Stamping a piece with higher walls means that more material needs to flow to form said walls. Therefore, the higher the vertical walls, the greater the required length of the clearance.On the other hand, the required length of the gap (g) will never exceed the maximum height of the vertical walls, because as we move away from the connection between the two adjacent subpieces, the effect of the transition region on the material flow decreases and is almost zero when the distance from the connection region begins to exceed the height of the vertical walls.

[039] In a specific embodiment, the length (g) of the gap (4), expressed in mm, is greater than or equal to 30%, preferably 50%, preferably 70% of the height of the highest vertical wall in the transition region (11T12) and less than or equal to said same height of the highest vertical wall in the transition region (11T12).

[040] In summary, the inventors discovered that it is possible Petition 870250110840, dated 03 / 12 / 2025, page 22 / 61 14 / 30 manufacture a metal part with the characteristics described above without excessive thinning or cracking in the transition zones, applying the following manufacturing process: - Provide at least two raw metal sub-pieces (101, 102) corresponding to the two sub-pieces (11, 12) of the metal piece (1), - Pre-assemble said at least two metal blank sub-pieces in a pre-assembly area to form a flexible metal blank (10), said flexible blank comprising at least one overlapping area (100) in which said blank sub-pieces overlap each other, said overlapping area comprising at least one sliding area (1001) in which said blank sub-pieces are free to slide over each other during said stamping operation and a fixed pre-assembly area (1002) in which said blank sub-pieces cannot move relative to each other during the stamping operation, - Perform a stamping operation by pressing the said flexible metal blank between a punch (2) and a die that move relative to each other in a stamping direction (S), wherein said punch (2) comprises at least one clearance (4) between the areas corresponding to said first and second sub-pieces (11, 12).

[041] The stamping of a flexible blank according to the invention is represented in Figures 4 and 5. Figure 4 represents the beginning of the stamping operation, at the point where the flexible blank (10) is fed into the stamping tool - in Figure 4, the punch (2) and the binder (3) are represented, but not the die, for visibility purposes. The punch and die close following the stamping direction (S) to form the metal part at the end of the stamping operation, as represented in Figure 5. Petition 870250110840, dated 03 / 12 / 2025, page 23 / 61 15 / 30

[042] In one specific embodiment, the stamping operation is a cold forming. In one specific embodiment, the stamping operation is hot stamping, optionally multi-stage hot stamping, optionally hot stamping with partial hardening.

[043] The blank sub-pieces (101, 102) are assembled together in the fixed pre-assembly area (1002), which allows them to be easily handled before stamping. For example, the blank sub-pieces are assembled by resistance spot welding in the pre-assembly area (1002) to form the spot welds (1003), as illustrated in Figure 2. For example, the blank sub-pieces are assembled by laser welding, for example, by remote laser welding in the pre-assembly area (1002). For example, the blank sub-pieces are assembled by gluing in the pre-assembly area (1002).

[044] After the forming operation, the sub-pieces are assembled together only in the fixed pre-assembly areas (1002), which can be the cause of structural fragility in the metal part. It is advantageous to additionally assemble the formed sub-pieces to increase the structural strength of the final part. In a specific embodiment, as illustrated in Figure 2, the sliding area (1001) of the overlapping area (100) of the raw sub-pieces further comprises at least one post-assembly area (1004) in which the said first and second sub-pieces (11, 12) still overlap each other after the said stamping operation. In this specific embodiment, the manufacturing process further comprises a post-assembly step after the stamping operation, during which at least the said first and second sub-pieces are joined in the said post-assembly areas (1004).For example, the sub-pieces are joined by spot welding to form spot welds (7), as illustrated in Figure 8. For example, the sub-pieces are laser welded, optionally. Petition 870250110840, dated 03 / 12 / 2025, page 24 / 61 16 / 30 laser welded joints remotely.

[045] For example, when applying the present invention to a metal part of a motor vehicle, this allows integrating longitudinal and transverse structural elements into a single metal part. For example, this allows integrating longitudinal front side rails and a crossmember of the instrument panel into a single part. For example, this allows integrating side sills and seat crossmembers into a single part. For example, this allows integrating roof rails and crossmembers into a single part. For example, this allows integrating rear side rails and crossmembers into a single part. By combining several structural elements into a single part, the manufacturing process is simplified and the part becomes more robust, as its longitudinal and transverse components are an integral part of the same piece and therefore cooperate ideally.

[046] In a specific embodiment, the stamping step is followed by a forming step, in which the shape of the metal part is further adjusted in the transition areas (11T12). In fact, due to the presence of the clearance (4) in the stamping tool punch (2), the raw material in the transition areas (11T12), corresponding to the clearance in the punch, is not pressed against the die. The shape of the metal part in this area will therefore not perfectly reproduce that of the die. In a specific embodiment, as shown in Figures 6A and 6B, a forming tool is used having a punch (21) with a smaller clearance (41) between the areas corresponding to the aforementioned first and second sub-parts. Figure 6A represents a stamping punch (2), according to the invention, with a clearance (4), and Figure 6B represents a forming punch (21), according to the invention, with a smaller clearance (41).By reducing the clearance (41) within the forming tool, the material is pressed more firmly against the die and therefore conforms better to it. Petition 870250110840, dated 03 / 12 / 2025, page 25 / 61 17 / 30 desired shape in the transition areas (11T12). It is possible to reduce the clearance (41) in the forming tool because the part has already been formed by stamping and the forces exerted by the forming operation on the rest of the part will be much smaller than during stamping, so that cracks will not occur in the transition areas. In any case, it will still be necessary to have a forming clearance (41) greater than 0 mm. In a specific embodiment, the length of the forming clearance (41) is comprised of 10% to 80% of the initial clearance length of the stamping punch (4), preferably 10% to 70%, preferably 10% to 50%, preferably 20% to 70%, preferably 20% to 50%.

[047] In one particular embodiment, the stamping operation and the forming operation are performed as two successive steps of a transfer press. For example, they are performed as two successive steps of a cold stamping transfer press. For example, they are performed as two successive steps of a multi-step hot stamping process using a transfer press.

[048] In a specific embodiment, the stamping operation and the forming operation are performed successively using an adjustable punch, in which the clearance (4) in the stamping stage can be reduced to the clearance (41) in the forming stage, for example, by sliding the punch element corresponding to the sub-part (2) closer to the punch element corresponding to the sub-part (11).

[049] The configuration described above of the metal part, comprising at least a first and a second subpart (11, 12), should be understood as the most basic possible configuration of a metal part according to the invention. Referring to Figure 7, said metal part (1) may, for example, comprise at least two first parts. Petition 870250110840, dated 03 / 12 / 2025, p. 26 / 61 18 / 30 subparts (11) generally extending along said first direction (D1), each connected to said at least one second subpart (12) generally extending along said second direction (D2). In this case, the flexible metal blank (10) comprises at least three subparts substantially corresponding to each of said subparts, said flexible blank further comprising at least two overlapping areas in which each blank subpart extending in a first direction overlaps the blank subpart extending in a second direction, each of said overlapping areas comprising at least one fixed area and one sliding area. Furthermore, the stamping tool used to manufacture said metal part will comprise a punch (2) having, in this case, at least two clearances (4), each corresponding to an area between the first subparts (11) and the second subpart (12).

[050] Any other combination between the first and second subpieces extending along directions (D1) and (D2) is also possible according to the invention. In fact, the essence of the invention is to provide a manufacturing process that allows the forming of the blank material in the transition regions (11T12) without the occurrence of cracks.

[051] In fact, the invention can be generalized to configurations of metal parts in which there are even more than two principal directions (D1) and (D2). In fact, the stamping problems solved by the invention occur locally in each transition region (11T12) and each set of transition regions is, in fact, independent of the others.

[052] In a specific embodiment, as illustrated in the upper part of Figure 1, the upper sections (113 and 123) of the first and second subpieces extend at different elevation levels; in other words, the difference in elevation levels (dz), as represented in Petition 870250110840, dated 03 / 12 / 2025, page 27 / 61 19 / 30 upper part of Figure 1, is different from 0. This type of configuration is very common for structural parts, for example, for automotive structural parts, because the strength requirement can vary in different directions and, with these requirements, the height of the vertical walls of the different sub-parts will be adjusted. Furthermore, in the case of a complex structure, such as the frame of a vehicle, the structural parts need to fit into a determined volume, which can limit the height of the walls in certain areas of the part. The inventors discovered that this elevation difference can lead to part failure during stamping. In fact, the material in the sliding area (1001) needs to move considerably to accommodate the elevation difference (dz), while the material in the fixed pre-assembly area (1002) cannot move during stamping.The significant shear forces thus generated between the two raw subpieces can exert excessive stress on the mounting points in the fixed pre-assembly area (1002), leading to assembly failure. Or, if the pre-assembly points do not fail, the material in the corresponding high-deformation zone of the sliding area may fail due to excessive thinning or cracking. These problems are even more significant if the elevation difference (dz) is significant.

[053] Referring to Figures 2, 8, 10A and 10B, the problem described above is illustrated by the variation in distance between two points represented in the figures by a star and a triangle. The first point, represented by a star, belongs to the fixed pre-assembly area (1002) of the flexible blank and is located in an area corresponding to the upper section (113) of the first sub-piece. The second point, represented by a triangle, belongs to the sliding area (1001) of the flexible blank and is located in an area corresponding to the upper section (123) of the second sub-piece. In the current description, the term “distance” designates the shortest path between two points, measured along the blank or metal part. The distance between the two referred to Petition 870250110840, dated 03 / 12 / 2025, page 28 / 61 20 / 30 points is X1 on the flexible raw part, before stamping, and X2 on the metal part, after stamping. Due to the elevation difference (dz) between the upper sections (113 and 123), which is transmitted during the stamping operation, the distance between said points must be increased by at least dz, i.e., X2 > X1 + dz.

[054] The inventors discovered that it was possible to solve this problem by providing, in the overlapping area (100), an extensible area (1005) connecting said fixed pre-assembly area (1002) and said sliding area (1001), wherein said pre-assembly area has a shear strength RS, expressed in MPa, said extensible area has a plastic deformation strength RP, expressed in MPa, and wherein RP < RS. Said shear strength RS of the fixed pre-assembly area (1002) is defined as the stress, measured in MPa, required to break the assembly between the two blank sub-pieces (101, 102), when said stress is applied on one side to the blank sub-piece (101) and on the other side to the blank sub-piece (102), in the direction of the force generated during the stamping operation.Similarly, the said resistance to plastic deformation RP of the extensible area (1005) is defined as the stress, measured in MPa, required to compensate for the plastic deformation of the extensible area (1005) when applying said stress to one side of the blank subpiece (101) and to the other side of the blank subpiece (102), in the direction of the force generated during the stamping operation.

[055] During stamping, the extensible area (1005) will begin to deform before the shear force exerted on the pre-assembly area reaches the critical value of RS. This deformation of the extensible area, in turn, will reduce the shear force exerted on the pre-assembly area, since the contradiction between the movement of the sliding area and the fixed pre-assembly area is resolved by the elongation of the extensible area. The area Petition 870250110840, dated 03 / 12 / 2025, page 29 / 61 The 21 / 30 extendable design therefore protects the pre-assembly area and resolves the problem described above of decohesion within the pre-assembly area.

[056] An iterative set of stamping simulations can be performed to successfully design the said extensible area (1005). For example, in a first iteration, a first extensible area (1005) is provided, the stamping operation is simulated, and the resulting RP and RS values ​​are deduced from the stamping simulation (these elements can be provided by the stamping simulation software used). If RP is greater than RS, i.e., if the assembly in the fixed pre-assembly area (1002) fails before the extensible area begins to flow in plastic deformation, then RS is increased, providing a stronger assembly (e.g., by adding spot welds in the case of a spot-welded assembly) or RP is decreased (e.g., by reducing the thickness of the extensible area, or using a material with lower yield strength, or adjusting the geometry of the said extensible area (1005)), or both.Next, an additional stamping simulation is performed, and the same necessary simulations are executed incrementally if, again, RP is greater than RS, until the desired situation of a flexible configuration is reached where RP < RS.

[057] For example, if spot welds (1003) are used to assemble the raw sub-pieces (101, 102) in the fixed pre-assembly area (1002), the mechanical behavior of said spot welds can be simulated as follows, applying the method developed in the Fosta 806 project: “P 806 - Simplified characterization and modeling of the fracture behavior of spot welds of ultra-high strength steels for collision simulation, considering the effects of the joints on the behavior of the components” (Fosta stands for “Forschungsvereinigung Stahlanwendung”, i.e., Research Association for Steel Application). The failure behavior and the calculation of the associated excluded elements can be simulated using the cards of Petition 870250110840, dated 03 / 12 / 2025, page 30 / 61 22 / 30 materials MAT123 and MAT_ADD_EROSION. Further explanations of the methodology can be found, for example, in “Simulation of Spot Welds and Weld Seams of Pressure Hardened Steel (PHS) Assemblies”, Stanislaw Klimek, International Automotive Body Congress 2008.

[058] The method described above for adjusting RP and RS using stamping simulation can also be performed using a physical stamping tool in which the design is adjusted, although this method, involving actual physical testing and iterative production of actual adjusted physical flexible blanks, may be more time-consuming and costly than the numerical simulation method.

[059] In a specific embodiment, said extensible area (1005) is characterized in that the length of said extensible area, measured along the molded metal part between the point where it is connected to the fixed area and the point where it is connected to the sliding area, increases after said stamping operation. In the attached figures, the star and triangle of Figures 2, 8, 10A and 10B correspond to the aforementioned attachment points of the extensible area (1005), respectively to the fixed area (1002) and the sliding area (1001). The term attachment point should be understood generically as an area of ​​attachment, not limited to a one-dimensional point, and possibly covering a more or less large part of the ends of said fixed and sliding areas (1002, 1001).

[060] The exact configuration of the extensible area (1005) will depend on the part design, structural requirements, available tooling, etc. For example, as represented in the attached figures, said extensible area can be made of the same material as the rest of the corresponding blank sub-part, using a convoluted shape in the flexible blank sub-part, such as an S-shape, which is then at least partially straightened during stamping. Petition 870250110840, dated 03 / 12 / 2025, page 31 / 61 23 / 30

[061] Other means of implementing the extensible area (1005) include, for example, the use of a multi-material blank, in which the material of the extensible area (1005) has very high formability (possibly with lower mechanical strength). For example, this is done by using a custom-welded blank with different materials for the extensible area and the other areas. Another possibility is to provide material with a smaller thickness in the extensible area (1005), which will reduce the resistance to plastic deformation of said area.

[062] For example, the extensible area (1005) is made of material folded into an accordion-like shape, which unfolds under the forces exerted during the stamping operation. As the resistance required to unfold a sheet is generally less than that required to extend it, this can be a way to reduce the RP of said extensible area.

[063] The present invention further encompasses a metal part corresponding to the characteristics listed above, considered individually or according to any possible combinations, and manufactured by the process detailed above, including all possible combinations of optional characteristics of said process.

[064] A significant advantage of the said metal part manufactured according to the said process is that it is possible, in a specific embodiment, to manufacture a metal part comprising at least one set of contiguous sub-parts with at least one set of two contiguous vertical walls, for example, (112) and (121), wherein the radius of curvature measured in the transition area (11T12) between said two contiguous vertical walls is extremely low. This is not possible in the state-of-the-art stamping technique without a flexible blank, because the shape in the transition region needs to be soft, i.e., with a radius of Petition 870250110840, dated 03 / 12 / 2025, p. 32 / 61 24 / 30 high curvature, in order to provide a progressive change in the direction of the flow of the material that makes up said contiguous vertical walls. For example, in a specific embodiment, the radius of curvature measured in the transition area (11T12) between said two contiguous vertical walls is equal to or less than twenty times, more specifically, less than ten times, and even more specifically, less than five times, the smallest sheet metal thickness of said two sub-pieces. In a specific embodiment, said radius of curvature is less than 100 mm, more specifically, less than 50 mm, more specifically, less than 20 mm, more specifically, less than 10 mm, and more specifically, less than 5 mm. In a specific embodiment, said radius of curvature is 0 mm, which means that said sub-pieces form an acute angle with each other.Providing a metal structural element with a low or even non-existent radius of curvature between adjacent side walls allows for optimal resistance of the element in the case of compressive stresses, for example, where different sub-elements extending in different directions need to cooperate with each other to resist compression. For instance, in the case of automotive structural elements, this is advantageous for resisting transverse and longitudinal collisions with the same elements.

[065] In a particular embodiment, the metal part (1) is produced by cold stamping from a flexible blank (10) comprising one of the following materials, either in the form of monolithic blanks or custom-rolled blanks or combined in the form of custom-welded blanks: - Steel having a chemical composition comprising, in % by weight: 0.13% < C < 0.25%, 2.0% < Mn < 3.0%, 1.2% < Si < 2.5%, 0.02% < Al < 1.0%, with 1.22% < Si+Al < 2.5%, Nb < 0.05%, Cr < 0.5%, Mo < 0.5%, Ti < 0.05%, the remainder being Fe and unavoidable impurities, and having a microstructure Petition 870250110840, dated 03 / 12 / 2025, page 33 / 61 25 / 30 comprising 8% to 15% retained austenite, the remainder being ferrite, martensite, and bainite, where the sum of martensite and bainite fractions is between 70% and 92%. With this composition, the steel sheet exhibits, measured in the rolling direction, a yield strength of between 600 MPa and 750 MPa and a maximum tensile strength of between 980 MPa and 1300 MPa, maintaining a total elongation above 19%. - Steel having a chemical composition comprising, in % by weight: 0.15% < C < 0.25%, 1.4% < Mn < 2.6%, 0.6% < Si < 1.5%, 0.02% < Al < 1.0%, with 1.0% < Si+Al < 2.4%, Nb < 0.05%, Cr < 0.5%, Mo < 0.5%, the remainder being Fe and unavoidable impurities, and having a microstructure comprising 10% to 20% retained austenite, the remainder being ferrite, martensite and bainite. With this composition, the steel sheet exhibits, measured in the rolling direction, a yield strength of 850 MPa to 1060 MPa and a maximum tensile strength of 1180 MPa to 1330 MPa, maintaining a total elongation above 13%. - Fully martensitic steel wherein the composition of the fully martensitic steel comprises, in % by weight: 0.15% < C < 0.5%, - Dual-phase steel with a microstructure comprising at least martensite and ferrite and with a UTS of at least 590 MPa, - Dual-phase steel with a microstructure comprising at least martensite and ferrite and with a UTS of at least 780 MPa, - Dual-phase steel with a microstructure comprising at least martensite and ferrite and with a UTS of at least 980 MPa.

[066] In a particular embodiment, the metal part is produced by hot stamping from a flexible blank (10) comprising one of the following materials, either in the form of monolithic blanks or custom-rolled blanks or combined in the form of custom-welded blanks: Petition 870250110840, dated 03 / 12 / 2025, page 34 / 61 26 / 30 - Steel having a composition comprising in % by weight: 0.06% < C < 0.1%, 1% < Mn < 2%, Si < 0.5%, Al < 0.1%, 0.02% < Cr < 0.1%, 0.02% < Nb < 0.1%, 0.0003% < B < 0.01%, N < 0.01%, S < 0.003%, P < 0.020% less than 0.1% of Cu, Ni and Mo, the remainder being iron and unavoidable impurities resulting from the manufacturing process. With this composition range, the yield strength of the corresponding area after hot stamping is between 700 and 950 MPa, the tensile strength is between 950 MPa and 1200 MPa, and the bending angle is greater than 75°. - Steel having a maximum tensile strength after hot stamping of between 1300 MPa and 1650 MPa and a yield strength of between 950 MPa and 1250 MPa, - Steel having a maximum tensile strength after hot stamping between 1300 MPa and 1650 MPa, a yield strength between 950 MPa and 1250 MPa, and a bending angle greater than 75°, - Steel having a composition comprising, in weight percentages: 0.20% < C < 0.25%, 1.1% < Mn < 1.4%, 0.15% < Si < 0.35%, Cr < 0.30%, 0.020% < Ti < 0.060%, 0.020% < Al < 0.060%, S < 0.005%, P < 0.025%, 0.002% < B < 0.004%, the remainder being iron and unavoidable impurities resulting from the manufacturing process. With this composition range, the maximum tensile strength of the corresponding area of ​​the part after hot stamping is between 1300 MPa and 1650 MPa, and the yield strength is between 950 MPa and 1250 MPa. - Steel having a tensile strength after press hardening greater than 1800 MPa, - Steel having a composition comprising, in weight percentages: 0.24% < C < 0.38%, 0.40% < Mn < 3%, 0.10% < Si < 0.70%, 0.015% < Al < 0.070%, Cr < 2%, 0.25% < Ni < 2%, 0.015% < Ti < 0.10%, Nb < 0.060%, 0.0005% Petition 870250110840, dated 03 / 12 / 2025, page 35 / 61 27 / 30 < B < 0.0040%, 0.003% < N < 0.010%, S < 0.005%, P < 0.025%, %, the remainder being iron and unavoidable impurities resulting from the manufacturing process. With this composition range, the tensile strength of the corresponding area after hot stamping is greater than 1800 MPa. - Steel having a composition comprising, in weight percent: C: 0.15 - 0.25%, Mn: 0.5 - 1.8%, Si: 0.1 - 1.25%, Al: 0.01 - 0.1%, Cr: 0.1 - 1.0%, Ti: 0.01 - 0.1%, B: 0.001 - 0.004%, P < 0.020%, S < 0.010%, N < 0.010% and optionally comprising one or more of the following elements, in weight percent: Mo < 0.40%, Nb < 0.08%, Ca < 0.1%, the remainder of the composition being iron and unavoidable impurities resulting from casting, - Steel having a composition comprising, in weight percent: C: 0.26 - 0.40%, Mn: 0.5 - 1.8%, Si: 0.1 - 1.25%, Al: 0.01 - 0.1%, Cr: 0.1 - 1.0%, Ti: 0.01 - 0.1%, B: 0.001 - 0.004%, P < 0.020%, S < 0.010%, N < 0.010% and optionally comprising one or more of the following elements, in weight percent: Ni < 0.5%, Mo < 0.40%, Nb < 0.08%, Ca < 0.1%, the remainder of the composition being iron and unavoidable impurities resulting from casting. With this composition range, the tensile strength of the corresponding area after hot stamping is greater than 1350 MPa and the bending angle is greater than 70°. - Steel having a composition comprising, in weight percent: C: 0.2 - 0.34%, Mn: 0.50 - 1.24%, Si: 0.5 - 2%, P < 0.020%, S < 0.010%, N < 0.010%, and optionally comprising one or more of the following elements, in weight percent: Al: <0.2%, Cr < 0.8%, Nb < 0.06%, Ti < 0.06%, B < 0.005%, Mo < 0.35%, the remainder of the composition being iron and unavoidable impurities resulting from casting. With this composition range, the tensile strength of the corresponding area after hot stamping is equal to or greater than 1000 MPa and the bending angle is greater than 55°. - Steel having a composition comprising, in % by weight: C: Petition 870250110840, dated 03 / 12 / 2025, pp. 36 / 61 28 / 30 0.13 - 0.4%, Mn: 0.4 - 4.2%, Si: 0.1 - 2.5%, Cr < 2%, Mo < 0.65%, Nb < 0.1%, Al < 3.0%, Ti < 0.1%, B < 0.005%, P < 0.025%, S < 0.01%, N < 0.01%, Ni < 2.0%, Ca < 0.1%, W < 0.30%, V < 0.1%, Cu < 0.2%, and verifying the following combination: 114 - 68*C - 18*Mn + 20*Si - 56*Cr - 60*Ni - 36*Al + 38*Mo + 79*Nb - 17691*B < 20, the remainder of the composition being iron and impurities. inevitable byproducts of casting. For example, this composition is used when hot stamping the part using a multi-step process. - Steel that is coated with an aluminum-based metallic coating. By aluminum-based coating is meant a coating comprising at least 50% aluminum by weight. For example, the metallic coating is an aluminum-based coating comprising 8-12% Si by weight. For example, the metallic coating is applied by immersing the base material in a molten metal bath. Advantageously, applying an aluminum-based metallic coating prevents the formation of surface fouling during the heating stage of the hot stamping process, which in turn allows parts to be produced by hot stamping without a subsequent sandblasting operation. Furthermore, the aluminum-based coating also provides corrosion protection to the metal part during use, for example, in a motor vehicle. - Steel that is coated with an aluminum-based metallic coating comprising 2.0 to 24.0% by weight of zinc, 1.1 to 12.0% by weight of silicon, optionally 0 to 8.0% by weight of magnesium and, optionally, additional elements chosen from Pb, Ni, Zr or Hf, the weight content of each additional element being less than 0.3% by weight, the balance being aluminum and, optionally, unavoidable impurities. Advantageously, this type of metallic coating provides very good corrosion protection to the part, as well as a good surface appearance after hot stamping. Petition 870250110840, dated 03 / 12 / 2025, pp. 37 / 61 29 / 30

[067] In a specific embodiment, at least one element of the back structure is manufactured by hot stamping from a laser-welded blank comprising at least one blank subpiece having an aluminum-based metallic coating and said aluminum-coated blank subpieces are pre-prepared by ablating at least part of the metallic coating at the edges to be welded. Advantageously, this removes some of the aluminum present in the coating, which would pollute the weld seam and deteriorate its mechanical properties.

[068] In a specific embodiment, at least one blank sub-piece of the flexible blank (10) comprises at least one area having at least one side covered with an emissivity-enhancing top layer. Said emissivity-enhancing top layer is applied to the outermost surface of said blank sub-piece. Said emissivity-enhancing top layer allows the surface of said blank sub-piece to have a higher emissivity compared to the same blank sub-piece that is not coated with said emissivity-enhancing top layer. Said emissivity-enhancing top layer may be applied to the top or bottom side of a blank sub-piece. Said emissivity-enhancing top layer may also be applied to both sides of said blank sub-piece.If the aforementioned raw sub-part comprises a metallic coating, as described previously, the emissivity-enhancing top layer is applied to the top of said metallic coating. In fact, for the emissivity-enhancing top layer to increase the surface emissivity, it needs to cover the outermost surface of the raw sub-part. Advantageously, said emissivity-enhancing top layer will allow for an increase in the heating rate of said raw sub-part and, therefore, increase the productivity of the heating stage of the process. Petition 870250110840, dated 03 / 12 / 2025, pp. 38 / 61 30 / 30 hot stamping. When using multiple blanks of different thicknesses, the aforementioned emissivity-enhancing top layer is advantageously applied to the blanks with the greatest thickness in order to decrease the difference in heating time between the different blanks and thus increase productivity, increase the hot stamping process window and, overall, allow obtaining a final part with homogeneous surface properties.

[069] The present invention further encompasses a metal part in the body of a motor vehicle corresponding to the characteristics listed above, taken individually or according to any possible combinations, and manufactured by the process detailed above, including all possible combinations of optional characteristics of said process.

[070] The present invention also covers the use of such metal part to assemble the body of a motor vehicle.

[071] The present invention also encompasses a motor vehicle comprising at least one of these metal parts. Petition 870250110840, dated 03 / 12 / 2025, pp. 39 / 61

Claims

1 / 5 Claims 1. MANUFACTURING PROCESS FOR PRODUCING A METAL PART (1) by stamping a flexible metal blank (10) according to a stamping direction (S), the metal part (1) comprising at least: - a first sub-part (11) generally extending along a first direction (D1), perpendicular to the stamping direction (S), and comprising at least a first side wall (111), substantially parallel to the stamping direction (S), connected to a first upper section (113), generally extending in a plane perpendicular to the stamping direction (S), - a second sub-part (12) connected to the first sub-part (11) and generally extending along a second direction (D2), perpendicular to the stamping direction (S) and forming with the first direction (D1) an angle α strictly greater than 0°, comprising at least two vertical walls (121, 122), substantially parallel to the stamping direction (S),and a second upper section (123) connecting the two vertical walls (121, 122), generally extending in a plane perpendicular to the stamping direction (S), the flexible metal blank (10) comprising at least: - two blank sub-pieces (101, 102), each substantially corresponding to the first and second sub-pieces (11, 12), - at least one overlapping area (100) in which the blank sub-pieces (101, 102) overlap each other, - the overlapping area (100) comprising at least one sliding area (1001) in which the blank sub-pieces (101, 102) are free to slide over each other during the stamping operation and a fixed pre-assembly area (1002) in which the blank sub-pieces (101, 102) do not Petition 870250110840, of 03 / 12 / 2025, page 40 / 61 2 / 5 can move relative to each other during the stamping operation,characterized by the manufacturing process comprising at least the steps of: - providing at least two metal blank sub-pieces (101, 102), - pre-assembling the at least two metal blank sub-pieces (101, 102) in the fixed pre-assembly area (1002) to form the flexible flat metal blank (10), - performing the stamping operation by pressing the flexible metal blank (10) between a punch (2) and a die that move relative to each other in the stamping direction (S), wherein the punch (2) comprises at least a clearance (4) between the areas corresponding to the first and second sub-pieces (101, 102).

2. MANUFACTURING PROCESS, according to claim 1, characterized in that the first and second directions (D1, D2), along which the first and second sub-pieces extend, form an angle α between them of 30° to 90°.

3. MANUFACTURING PROCESS, according to claim 2, characterized by the first and second directions (D1, D2), along which the first and second sub-pieces extend, forming an angle α between them of 60° to 90°.

4. MANUFACTURING PROCESS, according to claim 3, characterized by the first and second directions (D1, D2), along which the first and second sub-pieces extend, forming an angle α between them of 80° to 90°.

5. MANUFACTURING PROCESS, according to any one of claims 1 to 4, characterized by the raw sub-pieces (101, 102) being assembled together in the fixed pre-assembly area (1002) by welding to the point.

6. MANUFACTURING PROCESS, according to any one of claims 1 to 4, characterized in that the raw sub-pieces (101, 102) are assembled together in the fixed pre-assembly area (1002) by laser welding.

7. MANUFACTURING PROCESS, according to any one of claims 1 to 6, characterized in that the stamping operation is carried out by hot stamping.

8. MANUFACTURING PROCESS, according to any one of claims 1 to 6, characterized in that the stamping operation is carried out by cold stamping.

9. MANUFACTURING PROCESS, according to any one of claims 1 to 8, characterized in that the sliding area (1001) of the overlapping area (100) further comprises at least one post-assembly area (1004) in which the first and second sub-parts (11, 12) are still overlapping each other after the stamping operation is performed, and in which the manufacturing process further comprises a post-assembly step after the stamping operation, in which at least the first and second sub-parts (11, 12) are joined in at least one post-assembly area (1004).

10. MANUFACTURING PROCESS, according to claim 9, characterized in that the post-assembly step is carried out by spot welding.

11. MANUFACTURING PROCESS, according to claim 9, characterized in that the post-assembly step is performed by laser welding.

12. MANUFACTURING PROCESS, according to any one of claims 1 to 11, characterized in that the stamping operation is followed by a forming operation using a forming punch Petition 870250110840, dated 03 / 12 / 2025, page 42 / 61 4 / 5 (21) comprising a forming clearance (41) between the areas corresponding to the first and second sub-pieces, the forming clearance (41) being smaller than the clearance (4) of the initial stamping tool (2).

13. MANUFACTURING PROCESS, according to any one of claims 1 to 12, characterized in that the metal part (1) comprises at least two sub-parts (11) generally extending along the first direction (D1) and each being connected to at least one second sub-part (12) generally extending along the second direction (D2), wherein the flexible metal blank (10) comprises at least three blank sub-parts, each of which substantially corresponds to the sub-parts, the flexible blank further comprising at least two overlapping areas (100), in which each blank sub-part (101), which extends in a first direction (D1), overlaps the blank sub-part (102), which extends in a second direction (D2), each of the overlapping areas (100) comprising at least one fixed pre-assembly area (1002) and one sliding area (1001).

14. MANUFACTURING PROCESS, according to any one of claims 1 to 13, characterized in that at least the first and second sub-pieces (11, 12) have upper sections (113, 123) that extend at different elevation levels and in that the overlapping area (100) between the two corresponding blank sub-pieces (101, 102) further comprises an extensible area (1005) connecting the fixed pre-assembly area (1002) and the sliding area (1001), in that the fixed pre-assembly area (1002) has a shear strength RS, expressed in MPa, the extensible area (1005) has a plastic deformation strength RP, expressed in MPa, and in that RP < RS.

15. METAL PART (1), characterized by being manufactured as defined in any of claims 1 to 14. Petition 870250110840, dated 03 / 12 / 2025, page 43 / 61 5 / 5 16. METAL PART (1), according to claim 15, characterized by comprising at least one set of contiguous sub-parts (11, 12) having at least one set of two contiguous vertical walls (111, 121), wherein the radius of curvature measured in the transition area (11T12) between the two contiguous vertical walls is equal to or less than twenty times the smaller thickness of said two sub-parts.

17. METAL PART (1), according to any one of claims 15 to 16, characterized in that it is designed to be used in the body of a motor vehicle.

18. MOTOR VEHICLE, characterized by comprising at least one metal part (1), as defined in claim 17. Petition 870250110840, dated 03 / 12 / 2025, page 44 / 61

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