Integral rear side member structure for vehicle and method

Abstract

The invention relates to an integral rear side member structure for a vehicle frame. The integral rear side member structure includes a first rear side member, a second rear side member, and one or more cross members connecting the first rear side member to the second rear side member. The integral rear side member structure is formed by deforming a single composite blank. The single combined blank includes at least a first blank joined to a second blank such that the first blank partially overlaps the second blank to form one or more overlapping regions. The disclosure further relates to a method for manufacturing such an integral rear side member structure.

Description

[0001] This application claims the benefit of European Patent Application No. 22382942.5, filed on October 6, 2022. The present disclosure relates to an integral rear longitudinal beam structure for a vehicle, the integral rear longitudinal beam structure comprising a first rear longitudinal beam and a second rear longitudinal beam and one or more cross beams connecting the rear longitudinal beams. The present disclosure further relates to a method for manufacturing such an integral rear longitudinal beam structure. Background Art

[0002] Vehicles such as automobiles include a structural framework designed to withstand the loads that the vehicle may be subjected to during its service life. The structural framework is further designed to withstand and absorb impacts in the event of, for example, a collision with other automobiles or road structures.

[0003] The demand for weight reduction in the motor vehicle industry has led to the development and implementation of lightweight materials or components and related manufacturing processes and tools. The demand for weight reduction is particularly driven by the goal of reducing carbon dioxide emissions. The increasing concern for occupant safety has also led to the adoption of materials that improve the integrity of the vehicle during a collision while increasing the energy absorption rate.

[0004] A process known as hot forming die quenching (HFDQ) typically uses boron steel sheets to produce stamped parts with ultra-high strength steel (UHSS) properties, having a tensile strength of, for example, 1500 MPa or 2000 MPa, or even higher. The increase in strength allows the use of thinner gauge materials, which results in weight reduction compared to traditional cold-stamped low-carbon steel parts. Throughout the present disclosure, UHSS can be regarded as a steel having an ultimate tensile strength of 1000 MPa or more after a press hardening process.

[0005] In the HFDQ process, the blank to be hot formed can be heated to a predetermined temperature, such as the austenitization temperature or a higher temperature (especially a temperature between Ac3 and, for example, the evaporation temperature of the coating of the blank). A furnace system can be used for this purpose. Depending on the specific requirements, the furnace system can be equipped with additional heaters, such as induction heaters or infrared heaters. By heating the blank, the strength of the blank is reduced and the deformability is increased, i.e., to facilitate the hot stamping process.

[0006] There are several known ultra-high strength steels (UHSS) for hot stamping and hardening. The blank can be made of coated or uncoated boron steel, such as (22MnB5) available from ArcelorMittal.

[0007] Hot forming die quenching can also be referred to as "press hardening" or "hot stamping". These terms will be used interchangeably throughout the present disclosure.

[0008] Typical vehicle components that can be manufactured using the HFDQ process include: door beams, bumper beams, cross / side beams, A / B pillar reinforcements, front and rear longitudinal beams, seat cross-members, and roof longitudinal beams.

[0009] Due to the excellent strength and formability of boron steel, its hot forming is becoming increasingly popular in the motor vehicle industry. As a result, many structural components that were traditionally cold-formed from low-carbon steel are being replaced by hot-formed equivalents with significantly increased strength. This allows for a reduction in material thickness (and thus weight) while maintaining the same strength. However, the ductility and energy absorption rate of hot-formed components in the formed state are both at very low levels.

[0010] To increase the ductility and energy absorption rate of specific regions of a component, it is known to introduce softer regions within the same component. This increases ductility locally while maintaining the overall high strength required. By locally customizing the microstructure and mechanical properties of certain structural components to include regions with very high strength (very hard), i.e., regions with high ultimate tensile strength and high yield strength, and regions with increased ductility (softer), i.e., regions with lower ultimate tensile strength, lower yield strength, and increased elongation before fracture, the overall energy absorption rate of the component can be increased, its structural integrity can be maintained during a collision scenario, and its overall weight can also be reduced. In the case where the component ruptures under impact, such soft regions can also advantageously alter the motion behavior.

[0011] Known methods for creating regions with increased ductility ("soft regions" or "soft zones") in structural components of a vehicle include providing a tool comprising a pair of complementary upper and lower die units, each unit having a separate die element (steel block). The blank to be hot-formed is pre-heated to a predetermined temperature (e.g., the austenitization temperature or higher) by, for example, a furnace system to reduce its strength, i.e., to facilitate the hot stamping process.

[0012] The die elements can be designed to operate at different temperatures so as to have different cooling rates in different regions of the part being formed during the quenching process, resulting in different material properties in the final product. For example, a soft region will typically have a lower ultimate tensile strength and lower yield strength but allow for a greater elongation before fracture. For example, one die element can be cooled to quench the corresponding region of the component being manufactured at a high cooling rate, thus rapidly reducing the temperature of the component and obtaining a hard martensitic microstructure. Another adjacent die element can be heated to ensure that the corresponding part of the component being manufactured cools at a lower cooling rate, so as to obtain a softer microstructure, including, for example, bainite, ferrite, and / or pearlite. When the component exits the die, such regions of the component can remain at a higher temperature than the rest of the component.

[0013] Other methods for obtaining hot-stamped components with regions of different mechanical properties include, for example, customized or differential heating prior to stamping and local heat treatment after the stamping process to alter the local microstructure and obtain different mechanical properties. Further possibilities include the use of patchwork blanks and tailor-welded blanks (TWBs), which combine different thicknesses and / or materials in the blank.

[0014] Several methods for differential heating prior to stamping are known. In one example, for instance, when the blank is still in the furnace system, a nozzle or a group of nozzles can discharge a fluid stream, such as compressed cooling air, towards the part of the blank to be cooled. The other parts of the blank can be maintained at a higher temperature. This enables obtaining a blank with a customized temperature distribution along its length and / or width. In some examples, the blank can undergo further heating in an oven before being subjected to the stamping process.

[0015] In other examples, an array of infrared heaters can be used, which can be independently controlled to control the temperature along the blank.

[0016] Some elements of the structural skeleton of a vehicle, such as pillars (A-pillar, B-pillar, C-pillar), integral door rings, sills, floor panels, and woven sills, etc., can have one or more regions with a cross-section that is generally U-shaped (also known as "hat" shaped). These structural components can be manufactured in various ways and can be made of various materials. Lightweight materials that maintain the integrity of the vehicle while increasing the energy absorption during a collision are desirable.

[0017] Throughout this disclosure, a U-shaped cross-section can be understood to refer to a structural member that has a bottom wall and two side walls in its cross-section (usually in a transverse plane that is generally perpendicular to the longitudinal axis of the structural member). The U-shaped cross-section is generally known for having a good moment of inertia to weight ratio. The two side walls can form an obtuse angle with the bottom wall, for example, between 90° and 135°. The two side walls can include outwardly extending side flanges. The bottom wall and the side walls can be generally straight, but they can also include transition portions, curved parts, depressions, or protrusions.

[0018] In addition to the ultra-high-strength steels mentioned earlier, in parts of the structural skeleton where energy absorption is required, steels with greater ductility can also be used. Examples of ductile steels include 500, 1000 and CRL-340LA.

[0019] UHSS can exhibit a tensile strength of up to 1500 MPa or even 2000 MPa or more, especially after a press hardening operation. Once hardened, UHSS will have a martensitic microstructure. This microstructure can enhance the maximum tensile strength and yield strength per unit weight.

[0020] Some ductile steels can also be heated and pressed (i.e., used in a hot stamping process), but they do not have a martensitic microstructure after this process. Therefore, they will have a tensile strength and yield strength lower than that of UHSS, but they will have a higher elongation at break.

[0021] Although ductile steels can achieve energy absorption of structural components, it may not be easy to control and predict how the structural components behave during a vehicle collision. In addition, the overall weight of the vehicle frame is preferably as low as possible to reduce fuel consumption. Moreover, it is not easy to enhance energy absorption while maintaining a certain structural integrity of the structural components.

[0022] The present disclosure aims to provide improvements in reducing weight and controlling the deformation and energy absorption of an integral rear longitudinal beam structure for a vehicle frame when subjected to a load. SUMMARY OF THE INVENTION

[0023] In a first aspect, there is provided an integral rear longitudinal beam structure for a vehicle frame. The integral rear longitudinal beam structure includes a first rear longitudinal beam, a second rear longitudinal beam, and one or more cross beams connecting the first rear longitudinal beam to the second rear longitudinal beam. The integral rear longitudinal beam structure is formed by deforming a single combined blank. The single combined blank at least includes a first blank, which is joined to a second blank such that the first blank partially overlaps the second blank to form one or more overlapping regions.

[0024] According to this aspect, a structure with a simplified manufacturing process is provided. Since the integral rear longitudinal beam structure is manufactured by deforming a single blank, the manufacturing time and associated costs can be reduced. Further, other post-manufacturing processes that may affect the mechanical properties of the component, such as welding, are avoided. At the same time, the provided structure can have sufficient strength, stiffness, and energy absorption rate to protect the passengers of the vehicle in the event of an impact (e.g., a rear impact).

[0025] Since the combined blank formed into the integral rear longitudinal beam structure is composed of several blanks, these blanks can be configured to both absorb energy in an impact and transfer the impact load to a suitable area of the vehicle frame. Thus, the provided structure can prevent deformation of the safety zone inside the vehicle. The blanks that together form the combined blank are referred to herein as "blanks", but can also be regarded as "sub-blanks", i.e., blanks that form part of a larger blank. One or more individual blanks combined into the combined blank may also include smaller blanks or sub-blanks.

[0026] Moreover, setting overlapping regions can locally improve the mechanical properties of these regions of the structure and customize the strength and stiffness according to the structural requirements. Thereby, the overall strength of the structure per unit weight can be increased. At the same time, the overlapping regions can provide local restriction against deformation, saving the interior space of the vehicle.

[0027] Throughout this disclosure, the reference to "the mechanical properties of a part" can be understood as the mechanical properties of the material forming the part. Thus, unless otherwise specified, the comparison of the mechanical properties of various parts, components or other parts is directed to the material, rather than its geometry or other characteristics.

[0028] In this document, higher mechanical properties can be understood as higher ultimate tensile strength and / or higher yield strength, while lower mechanical properties can be understood as lower ultimate tensile strength and / or lower yield strength. The ultimate tensile strength and yield strength are regarded as the material properties of the material after the manufacturing process in this document. The ultimate tensile strength and yield strength can be determined in a standardized tensile strength test, for example, using A30, A50 or A80 specimens in a quasi-static load test.

[0029] The same test conditions and specimen sizes should be used for the comparison of lower and higher mechanical properties. To compare the yield strength of different parts, specimens made of the same material as the parts of the main soft zone can be prepared and tested in a universal testing machine (UTM).

[0030] In each example, the integral rear longitudinal beam structure can be made by hot stamping, and the structure can be formed in a single forming step. Further, if desired, when applying hot stamping, different regions of the structure can be subjected to different temperature treatments, resulting in regions with different mechanical properties.

[0031] In each example, the overlapping regions generally correspond to one or more transition portions between one longitudinal beam in the longitudinal beam and one cross beam in the cross beam. This creates a connection with improved mechanical properties between the longitudinal beam and the cross beam and enhances the overall movement behavior of the structure. Thus, the transition portion between the longitudinal beam and the cross beam can be designed to have higher mechanical properties compared to the rest of the integral rear longitudinal beam structure.

[0032] In some examples, the first rear longitudinal beam and the second rear longitudinal beam include a first region configured to attach the integral rear longitudinal beam structure to the chassis. Further, the first region has an ultimate tensile strength of 1500 MPa or more after hot stamping. This provides a firm connection between the integral rear longitudinal beam structure and the chassis of the vehicle and establishes a strong load path to transfer the load from the impact point to certain components of the vehicle frame.

[0033] In some examples, the first rear longitudinal beam and the second rear longitudinal beam include a second region that is more ductile than the first region. The second region may have an ultimate tensile strength between 700 Mpa and 1200 MPa after hot stamping and may have a yield strength between 500 Mpa and 900 MPa after hot stamping. The second region being more ductile than the rest of the rear longitudinal beam can enhance energy absorption during an impact. This can reduce the acceleration of the vehicle after an impact and allow control of the deformation of the longitudinal beam and avoid loads or deformations reaching other regions of the integral rear longitudinal beam structure.

[0034] In various examples, the first region and the second region have different microstructures. This can be achieved by applying different temperature treatments to the first region and the second region. Thus, in various examples, a single blank having a substantially uniform material composition can be used to form a rear longitudinal beam having separate regions with different mechanical properties.

[0035] In some examples, a single combined blank can include different thicknesses and / or materials. Regions with increased thickness can be located where loads and stress concentrations are likely to be higher in the event of an impact. Specifically, the regions with increased thickness can be formed by overlapping two blanks. Further, materials with high mechanical properties can be located in regions intended to reduce the deformation of the structure. On the other hand, materials with low mechanical properties can be located in regions intended to absorb impact energy and deform during an impact.

[0036] In some examples, at least one of the longitudinal beam and the cross beam of the integral rear longitudinal beam structure has a substantially U-shaped cross-section. The U-shaped cross-section includes a bottom wall, a first side wall, a second side wall, a first lateral flange protruding outwardly at one end of the first side wall, and a second lateral flange protruding outwardly at one end of the second side wall. The U-shaped cross-section increases the moment of inertia of the region in which it is formed and improves the resistance of the member to impacts (specifically impacts at an angle relative to the longitudinal direction of the member).

[0037] In various examples, the integral rear longitudinal beam structure can further include a cover plate attached to the rear longitudinal beam and substantially enclosing the U-shaped cross-section. The cover plate can be made of the same or a different material as the rear longitudinal beam and can enhance the energy absorption and stiffness of the integral rear longitudinal beam structure.

[0038] In some examples, the integral rear longitudinal beam structure may further include at least a portion of the floor panel. For example, the rear longitudinal beams may be connected to each other through a portion of the floor panel. In various examples, the floor panel may be formed from a blank that is joined to other blanks to form a combined blank. The floor panel may include any features related to materials and the like as disclosed herein with respect to the rear longitudinal beams and cross members. In various examples, the floor panel may be integrated into the cross member, i.e., it may have structural members connecting the first rear longitudinal beam and the second rear longitudinal beam.

[0039] In another aspect, a method for manufacturing an integral rear longitudinal beam structure for a vehicle frame as described in the present disclosure is provided. The integral rear longitudinal beam structure includes a first rear longitudinal beam, a second rear longitudinal beam, and one or more cross members.

[0040] The method includes providing a combined blank. The method further includes providing a first blank and a second blank, and arranging the first blank and the second blank such that the first blank partially overlaps the second blank in an overlapping region. Further, the method includes joining the first blank to the second blank at the overlapping region to form a combined blank. Additionally, the method includes heating the combined blank at least partially above the austenitizing temperature and press hardening the heated combined blank to form the integral rear longitudinal beam structure.

[0041] The method can reduce the manufacturing costs associated with multi-component structures that require multiple manufacturing and assembly steps. Thus, the disclosed method allows for a reduction in manufacturing time and floor space in a manufacturing facility, etc. Further, the method provides an integral rear longitudinal beam structure having enhanced mechanical properties both in terms of impact resistance and deformation behavior. Additionally, compared to alternative methods, the disclosed method provides an integral rear longitudinal beam structure having an improved impact protection weight ratio.

[0042] The combined blank is to be understood herein as a blank forming the main member, such as a sheet metal or a flat metal plate. The combined blank may be at least partially made of a hardenable steel, specifically boron steel. The thickness of the combined blank may generally be between 1 mm and 2.5 mm. The combined blank may be made by joining two or more blanks to each other. The blanks forming the combined blank themselves may be made of further (sub-blanks), e.g., one of the blanks forming the combined blank may be joined to another blank by overlapping, and itself may be a tailor welded blank (TWB).

[0043] In some examples of the method, at least one of the overlapping regions between the first blank and the second blank may generally correspond to the transition portion between the longitudinal beam and the cross beam. Traditionally, the longitudinal beam and the cross beam are manufactured separately and joined to each other. By joining multiple blanks to obtain a single integrally formed rear longitudinal beam structure, some material is lost at the transition portion between the longitudinal beam and the cross beam. To compensate for this material loss, the thickness can be increased by precisely establishing overlapping regions where needed, thereby locally increasing the strength. Such an overlap can be relatively small compared to using tailor welded blanks (TWBs) that require different materials or thicknesses over a larger area, and is thus more effective. It is also more efficient and effective than, for example, high pressure die casting of aluminum, because high pressure die casting requires a large amount of aluminum to achieve the same strength as, for example, a hot stamped UHSS component.

[0044] In some examples of the method, the first blank and the second blank can be attached to each other by spot welding.

[0045] In some other examples, the first region of the integral rear longitudinal beam structure can have an ultimate tensile strength of 1500 MPa or more after press hardening. Further, the second region of the integral rear longitudinal beam structure can have an ultimate tensile strength between 700 MPa and 1200 MPa after press hardening.

[0046] Thus, the first region can be configured to generally bear the load during impact. Therefore, the first region can be the region configured to connect the integral rear longitudinal beam structure to other structural components of the vehicle (such as the chassis). Further, the second region can be configured to absorb energy and deform during impact to reduce the acceleration experienced by the vehicle's passengers and limit the transfer of the load to other components of the vehicle.

[0047] In some examples, the first region of the combined blank is subjected to a different heat treatment compared to the second region of the combined blank. This allows, for example due to differences in microstructure, the formation of regions with different mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Non-limiting examples of the present disclosure will be described below with reference to the drawings, in which:

[0049] Figure 1 A bottom view schematically showing an example of an integral rear longitudinal beam structure for a vehicle according to the present disclosure;

[0050] Figure 2 An exploded view schematically showing a part of another example of the integral rear longitudinal beam structure according to the present disclosure;

[0051] Figure 3 Schematically shows across Figure 1 a cross-sectional view of the plane A-A' in

[0052] Figure 4 A cross-sectional view schematically showing another example of the integral rear longitudinal beam structure according to the present disclosure;

[0053] Figure 5 Another example view schematically showing a part of another example of the integral rear longitudinal beam structure;

[0054] Figure 6A A top view schematically showing another example of the integral rear longitudinal beam structure for a vehicle according to the present disclosure;

[0055] Figure 6B Schematically shows Figure 6A The bottom perspective view of the example of the integral rear longitudinal beam structure in

[0056] Figure 7A Schematically shows a single blank before forming another example of the integral rear longitudinal beam structure;

[0057] Figure 7B and Figure 7C Schematically shows after Figure 7A A part of the component obtained after hot stamping the single blank of

[0058] Figure 8 Schematically shows a single blank before forming yet another example of the integral rear longitudinal beam structure;

[0059] Figure 9 Is a flowchart of a method for manufacturing a structural component at least partially configured to support bending loads.

[0060] The accompanying drawings refer to example embodiments and are only used to assist in understanding the claimed subject matter and do not limit it in any sense. Detailed Description

[0061] Figure 1 A bottom view schematically showing an example of an integral rear longitudinal beam structure 100 for a vehicle frame. The integral rear longitudinal beam structure 100 includes a first rear longitudinal beam 10, a second rear longitudinal beam 20, and one or more cross beams 30, 40 connecting the first rear longitudinal beam 10 to the second rear longitudinal beam 20. Further, the integral rear longitudinal beam structure 100 is formed by deforming a single blank. The single blank at least includes a first blank, which is joined to a second blank such that the first blank partially overlaps the second sub-blank to form one or more overlapping regions 50.

[0062] In Figure 1In the example shown, the integral rear longitudinal beam structure 100 includes two cross beams 30, 40, but in other examples, other numbers of cross beams may be used. For example, the integral rear longitudinal beam 100 may include only one cross beam, or include three or more cross beams. Additionally, the cross beams 30, 40 may be distributed in different ways. For example, depending on the specifications of the integral rear longitudinal beam structure 100, the spacing between the cross beams 30, 40 may be increased or decreased.

[0063] Since the rear longitudinal beam structures disclosed herein are made of integral (one-piece formed) elements, there are no separate components that meet the requirements of longitudinal beams or cross beams, and the boundaries between them are not very clear. Therefore, the terms "longitudinal beam portion" and "cross beam portion" can be used to represent the respective portions of the same element that function as longitudinal beams or cross beams.

[0064] In the example shown, the integral rear longitudinal beam structure 100 can be made by hot stamping. For example, it can be made by a direct hot stamping manufacturing process or an indirect hot stamping manufacturing process. In other examples, the integral rear longitudinal beam structure 100 can be made by cold stamping or by other manufacturing processes. More details regarding the manufacturing processes of the components will be described in connection with FIGS. 6 to Figure 8 Describe more details about the manufacturing processes of the components.

[0065] In some examples, the integral rear longitudinal beam structure 100 can be made of boron steel, such as For example 1500 (or 22MnB5 steel with or without a protective coating), 2000 (or any 37MnB5 steel) or any martensitic steel or ultra-high strength steel (UHSS). Available from ArcelorMittal.

[0066] 1500 is supplied in a ferrite-pearlite phase. It is a fine-grained structure distributed in a uniform pattern. Its mechanical properties are related to this structure. After heating, the hot stamping process, and subsequent quenching, a martensitic microstructure is produced. Therefore, the tensile strength and yield strength are significantly increased.

[0067] The composition of 1500 is generally as follows by weight percentage (the rest is iron (Fe) and impurities):

[0068] Carbon (C) maximum percentage (%): 0.25

[0069] Silicon (Si) maximum percentage (%): 0.4

[0070] Manganese (Mn) maximum percentage (%): 1.4

[0071] Phosphorus (P) maximum percentage (%): 0.03

[0072] Maximum proportion of sulfur (S) (%): 0.01

[0073] Aluminum (Al) (%): 0.01 - 0.1

[0074] Maximum proportion of titanium (Ti) (%): 0.05

[0075] Maximum proportion of niobium (Nb) (%): 0.01

[0076] Maximum proportion of copper (Cu) (%): 0.20

[0077] Maximum proportion of boron (B) (%): 0.005

[0078] Maximum proportion of chromium (Cr) (%): 0.35

[0079] 2000 is another type of boron steel with higher strength. After the quenching process of the hot stamping die, The yield strength of 2000 can be 1300 MPa or above, and its ultimate tensile strength can be above 1800 MPa.

[0080] The composition of 2000 is summarized as follows by weight percentage (the rest is iron (Fe) and impurities):

[0081] Maximum proportion of carbon (C) (%): 0.36

[0082] Maximum proportion of silicon (Si) (%): 0.8

[0083] Maximum proportion of manganese (Mn) (%): 0.8

[0084] Maximum proportion of phosphorus (P) (%): 0.03

[0085] Maximum proportion of sulfur (S) (%): 0.01

[0086] Aluminum (Al) (%): 0.01 - 0.06

[0087] Maximum proportion of titanium (Ti) (%): 0.07

[0088] Maximum proportion of niobium (Nb) (%): 0.07

[0089] Maximum proportion of copper (Cu) (%): 0.20

[0090] Maximum proportion of boron (B) (%): 0.005

[0091] Maximum proportion of chromium (Cr) (%): 0.50

[0092] Maximum proportion of molybdenum (Mb) (%): 0.50

[0093] 22MnB5 can be provided with an aluminum-silicon coating to avoid decarburization and scaling during the forming process.

[0094] Several 22MnB5 steels with similar chemical compositions are available. However, the exact amount of each component in the 22MnB5 steel may vary slightly depending on the manufacturer. Other ultra-high-strength steels include, for example, BTR165 available from Benteler.

[0095] In the examples, the integral rear longitudinal beam structure 100 may include members made of different materials. For example, the first rear longitudinal beam 10 and the second rear longitudinal beam 20 may be made of UHSS (such as 22MnB5 or another boron steel) in one area, while made of a more ductile steel in another area, and the cross beam 30 may be made of UHSS.

[0096] Moreover, depending on the requirements, the type of UHSS can be different. For example, 22MnB5 or 1500 can be used for the harder areas of the longitudinal beams, and the first cross beam 30 and the second cross beam 40 can be made of, for example, 37MnB5 or 2000. Depending on the desired dynamic response and mechanical properties, other materials can be selected to form the integral rear longitudinal beam structure 100. Additionally, a given member can have areas made of different materials. For example, the first rear longitudinal beam 10 and the second rear longitudinal beam 20 can have a first area 11 made of 2000 and a second area 12 made of 1500 or 1000.

[0097] is a steel with much higher ductility than the material, and components made of this material can be effective in absorbing energy during impact. The yield strength of 500 can be 400 MPa or higher, and the ultimate tensile strength can be 550 MPa or higher.

[0098] The composition of 500 is summarized by weight percentage as follows (the rest is iron (Fe) and impurities):

[0099] Maximum proportion of carbon (C) (%): 0.1

[0100] Maximum proportion of silicon (Si) (%): 0.5

[0101] Maximum proportion of manganese (Mn) (%): 1.7

[0102] Maximum proportion of phosphorus (P) (%): 0.03

[0103] Maximum proportion of sulfur (S) (%): 0.025

[0104] Aluminum (Al) (%): 0.015 - 0.2

[0105] Maximum proportion of titanium (Ti) (%): 0.09

[0106] Maximum proportion of niobium (Nb) (%): 0.10

[0107] Maximum proportion of copper (Cu) (%): 0.20

[0108] Maximum proportion of boron (B) (%): 0.001

[0109] Maximum proportion of chromium (Cr) (%): 0.20

[0110] The yield strength of 1000 can be 800 MPa or above, and the ultimate tensile strength can be 1000 MPa or above. The composition of 1000 is summarized by weight percentage as follows (the rest is iron (Fe) and impurities):

[0111] Maximum proportion of carbon (C) (%): 0.10

[0112] Maximum proportion of silicon (Si) (%): 0.6

[0113] Maximum proportion of manganese (Mn) (%): 1.8

[0114] Maximum proportion of phosphorus (P) (%): 0.03

[0115] Maximum proportion of sulfur (S) (%): 0.01

[0116] Aluminum (Al) (%): 0.01 - 0.1

[0117] Maximum proportion of titanium (Ti) (%): 0.05

[0118] Maximum proportion of niobium (Nb) (%): 0.10

[0119] Maximum proportion of copper (Cu) (%): 0.20

[0120] Maximum proportion of boron (B) (%): 0.005

[0121] Maximum proportion of chromium (Cr) (%): 0.20

[0122] Such as Figure 1As shown, the overlapping region 50 may generally correspond to one or more transition portions between one of the longitudinal beams 10, 20 and one of the cross beams 30, 40. Thereby, the mechanical properties of the connection between the components are improved. The transition portion between the longitudinal beam portion and the cross beam is the region where the longitudinal beam portion intersects the cross beam portion, or in other words, it is the region where the body arranged substantially longitudinally changes to the body arranged substantially transversely.

[0123] In the illustrated example, the first rear longitudinal beam 10 and the second rear longitudinal beam 20 may include first regions 11, 21 configured to attach the integral rear longitudinal beam structure 100 to the chassis. The regions joined to the chassis may require higher stiffness and strength. The first regions 11, 21 may be made of a suitable UHSS, such as 22MnB5 or similar materials, and may have an ultimate tensile strength of higher than 1500 MPa or above, more specifically higher than 1800 MPa or above after hot stamping.

[0124] Furthermore, the first rear longitudinal beam 10 and the second rear longitudinal beam 20 may further include second regions 12, 22, which have an ultimate tensile strength between 700 MPa and 1200 MPa and a yield strength between 500 MPa and 900 MPa after hot stamping. These second regions 12, 22 may be configured to absorb energy and deform during impact. These second regions 12, 22 may be made of or other suitable steels that are more ductile than the steel used for the first regions. The transition portion between the second regions 12, 22 and the rest of the rear longitudinal beam may include an overlapping region. In other examples, the second regions 12, 22 and the rest of the rear longitudinal beams 10, 20 may be formed as tailor-welded blanks, i.e., individual blanks may be welded to each other in an edge-to-edge welding process ("butt joint").

[0125] Furthermore, different regions of the integral rear longitudinal beam structure 100 may be made of blanks using the same (base) material but having different local microstructures. For example, the first regions 11, 21 and the second regions 12, 22 may be made of materials having substantially the same composition but different local microstructures. This may be obtained by applying different heat treatments before, during, or after the stamping process. For example, local heat treatment using induction heating or laser after the stamping process may result in regions 11, 21, 12, 22 having different mechanical properties.

[0126] In Figure 1 the illustrated example, the first regions 11, 21 of the rear longitudinal beams 10, 20 may have a martensitic microstructure, and the second regions 12, 22 of the rear longitudinal beams may have a microstructure including bainite, ferrite, and / or pearlite.

[0127] The overlapping region 50 may have a width between 10 mm and 100 mm, specifically between 20 mm and 60 mm, and more specifically between 20 mm and 50 mm. That is, the overlapping region may extend over the entire width of the cross member 30 and extend into the longitudinal beam portion, for example, by 20 mm to 60 mm.

[0128] The area of the overlapping region at the transition between one of the rear longitudinal beams and the cross member in the rear longitudinal beam may be, for example, 20 cm 2 to 600 cm 2 , specifically 30 cm 2 to 500 cm 2 , more specifically between 40 cm 2 and 450 cm 2 .

[0129] Figure 2 A partial exploded view schematically showing another example of the integral rear longitudinal beam structure 100 according to the present disclosure is shown. The exploded view shows the first rear longitudinal beam 10 and the cross member 30. It should be clear that even though the longitudinal beam and the cross member are shown as separate components in this exploded view, they are actually formed as a single integral structure.

[0130] Figure 2 The overlapping region 50 between these two components is shown. It can be seen that due to a single forming operation, the first rear longitudinal beam 10 and the cross member have a matching geometry within the overlapping region 50. It should be noted that the overlapping region 50 has been marked with a rectangular box with a dashed line, and the overlapping region 50 is only partially shown here because it can extend over the entire width of the cross member 30.

[0131] Figure 2 It is further shown that the first rear longitudinal beam 10 may have a generally U-shaped cross section. The U-shape has a bottom wall 15, a first side wall 16, a second side wall 17, and a first lateral flange 18 protruding outwardly at one end of the first side wall 16. Although not shown, in this example (e.g., at another longitudinal position) or other examples, the U-shaped cross section may also have a second lateral flange protruding outwardly at one end of the second side wall 17.

[0132] In some examples, the (multiple) lateral flanges 18 may have a microstructure different from that of the (multiple) side walls to which they are attached. More specifically, the (multiple) lateral flanges may have lower mechanical properties than the (multiple) lateral walls in which they are located to facilitate connection to other components (such as other vehicle frame components). For example, local heat treatment may be performed on the portion of the flange that engages the adjacent structure, or differential cooling may be applied in a hot pressing device.

[0133] Figure 2It is also shown that the crossbeam 30 can also have a U-shaped cross-section. Further, any member of the integral rear longitudinal beam structure 100 can define other cross-sectional geometries. For example, any member of the integral rear longitudinal beam structure 100 can define an L-shaped cross-section along at least a portion of its length, a W-shaped cross-section along a portion of its length, or other cross-sections.

[0134] Although not shown in the Figure 2 example, the bottom wall 15 can be curved or include depressions or protrusions along the bottom. The same applies to the side walls 16, 17, which are not necessarily completely straight. The side walls 16, 17 can include straight portions with curved transition regions therebetween. Further, the side walls 16, 17 can be symmetric or asymmetric. For example, the height of the first side wall 16 can be different from the height of the second side wall 17. In some examples, the height along the longitudinal direction of the first side wall 16 and / or the second side wall 17 can also vary. In each example, the width of the bottom wall 15 can also vary along the longitudinal direction of the bottom wall 15. Further, the width of the bottom wall 15 can be different from the height of the first side wall 16 and / or the second side wall 17. Other examples can include any combination of the above examples.

[0135] Figure 2 It is also shown that the integral rear longitudinal beam structure can include a cover plate 60. The cover plate 60 can be formed by one or more cover components 61, 62. In fact, in this example, the cover plate 60 includes a first cover component 61 configured to enclose the U-shaped cross-section of the first rear longitudinal beam 10 and a second cover component 62 configured to enclose the U-shaped cross-section of the crossbeam 30. As previously mentioned, the cover plate 60 can also be manufactured in a single molding step. The cover plate 60 can be shaped to at least partially enclose the cross-section (U-shaped or other shape) of each member to increase stiffness, specifically torsional stiffness.

[0136] In Figure 2 the example shown, the first cover component 61 includes a vertical flange 63 configured to be coupled to the vertical region of the second side wall 17 of the first rear longitudinal beam 10. Further, the first cover component 61 includes a horizontal flange 64 configured to be coupled to the first flange 18 of the rear longitudinal beam 10. Thus, the first cover component 61 can be coupled to the first rear longitudinal beam 10 by welding through the flanges 63, 64. In addition, the second cover component 62 can be coupled to the crossbeam 30 in a similar manner, i.e., by welding through flanges to the crossbeam 30. Both remote laser welding and spot welding can be used.

[0137] Further, the first cover member 61 and the second cover member 62 may have different mechanical properties. In fact, the cover members 61, 62 may also have regions with different mechanical properties. For example, the flanges 63, 64 may be made of a material having lower mechanical properties than the rest of the cover member 61. According to the present disclosure, other numbers of cover members (i.e., three or more) and other relative sizes and geometries may be included in the cover plate 60.

[0138] Figure 3 Schematically shows a cross-sectional view across Figure 1 the plane A-A' in Figure 3 shows the transition between a portion of the first rear longitudinal beam 10 and a portion of the cross beam 30, but it is equally applicable to the transitions between other components of the integral rear longitudinal beam structure 100. In this example, the first rear longitudinal beam 10 includes a U-shaped cross-section having a bottom wall 15, a first side wall 16, a second side wall 17, and a first lateral flange 18 that projects outwardly at one end of the first side wall 16. The flange 18 overlaps a portion of the cross beam 30 to form an overlapping region 50.

[0139] In this example, the flange 18 of the longitudinal beam portion and the cross beam 30 are attached together by spot welding. It should be noted that the spot welds 51 have been schematically shown as dots. Multiple spot welds 51 may be used to connect the first rear longitudinal beam 10 to the cross beam 30. In other examples, other joining techniques may be used, specifically other welding techniques such as laser welding. It should also be noted that although the spot welds are indicated in the final product, the spot welding (or other joining) actually occurs before deforming the blank, i.e., before the hot stamping process. The welding can thus be performed on the flat blank, which makes the welding easier.

[0140] As previously discussed, the width of the overlapping region 50 can be adapted to the specifications of the structure 100. Thus, when the integral rear longitudinal beam structure 100 is designed to withstand higher impact loads (e.g., a higher vehicle mass), the width can be increased.

[0141] Figure 3 Also shown is that the connection between the cross beam 30 and the first rear longitudinal beam 10 leaves a vacant space 55 in which other vehicle components (e.g., electronic components) can be located. In this example, making the rear longitudinal beam structure an integral structure creates additional space for vehicle components.

[0142] Figure 4 Shows a cross-sectional view as Figure 3 but for another example of the integral rear longitudinal beam structure 100. More precisely, Figure 4 the integral rear longitudinal beam structure 100 inFigure 3 As discussed, multiple spot welds 51 can be used to connect the structural members.

[0143] In Figure 4 the example shown, the combined blank that is deformed to form the integral rear longitudinal beam structure 100 is formed from multiple blanks. Thus, the first blank can be formed to have a generally L-shaped cross-section, and the second blank can be formed such that it mates with the first blank and forms the U-shaped rear longitudinal beam 10. Additionally, the second blank can also form a U-shaped cross-section (not visible in the view shown).

[0144] Figure 5 Another part of another example of an integral rear longitudinal beam structure 100 including a cover plate 60 is schematically shown. In this example, the integral rear longitudinal beam structure 100 includes a first rear longitudinal beam 10 and a cross beam 30, both of which have a closed cross-section. A second rear longitudinal beam (not shown) can also have a closed cross-section. Further, FIG. 6 shows that the overlapping region 50 generally corresponds to the transition portion between the longitudinal beam 10 and the cross beam 30, and the arrangement between these structural members can provide a vacant space 55 in which other components of the vehicle (such as electronic components) can be placed.

[0145] As regarding Figure 2 what is discussed, the closed cross-section can be formed by attaching a cover plate 60 to the rear longitudinal beam and the cross beam (e.g., attaching to the first rear longitudinal beam 10 and the cross beam 30 both having a U-shaped cross-section). The cover plate 60 can be attached to the rear longitudinal beam and the cross beam by spot welding.

[0146] Figure 6A and Figure 6B Another example of an integral rear longitudinal beam structure 100 for a vehicle according to the present disclosure is schematically shown. Figure 6A A top view of the integral rear longitudinal beam 100 is shown, Figure 6B and a bottom perspective view of the integral rear longitudinal beam 100 is shown.

[0147] In Figure 6A the example, the overlapping region 50 is shown hatched.

[0148] Figure 6A It is shown that the integral rear longitudinal beam structure 100 includes a first rear longitudinal beam 10, a second rear longitudinal beam 20, and a cross beam 30. The integral rear longitudinal beam structure 100 can be made by hot stamping a single (combined) blank. In this example, the combined blank is made from seven smaller blanks: two blanks for each of the longitudinal beams and three blanks for the cross beam.

[0149] The cross member 30 of the integral rear longitudinal beam structure 100 can be made of three blanks 31, 32, 33 and is configured to connect the first rear longitudinal beam 10 and the second rear longitudinal beam 20. Thus, the cross member 30 can be made of two blanks 31, 33 and a central blank 32. The blanks 31, 33 roughly correspond to the transition portions between the longitudinal beams 10, 20 and the cross member 30, and the central blank 32 connects the two lateral members 31, 33 together.

[0150] As Figure 6A can be seen in, the overlapping regions 50 between different blanks can be designed to have different widths. For example, the overlapping region 50 that roughly corresponds to the transition portions between the longitudinal beams 10, 20 and the cross member 30 can have a width between 30 mm and 60 mm, such as a width combined with roughly the entire width of the cross member (i.e., across the U-shape and preferably including the flange of the U-shape). Alternatively, the overlapping region can extend at least in the region of the transition from the longitudinal beam to the cross member across the entire width of the rear longitudinal beams 10, 20 and, for example, across the entire width of the cross member.

[0151] Furthermore, the width of the overlapping region 50 between the blanks 31, 33 and the central blank 32 can be between 10 mm and 30 mm. In this case, the overlapping portion extends across the width of the central blank 32 (i.e., the width of the cross member), and the overlapping portion extends in the lateral direction of the vehicle (the longitudinal direction of the cross member) by, for example, 10 mm to 30 mm. The width of the overlapping region 50 can be modified to adapt the mechanical properties of the integral rear beam structure 100 to different applications.

[0152] Furthermore, Figure 6A shows that the rear longitudinal beams 10, 20 can include two regions made of materials with different mechanical properties. For example, the first regions 11, 21 of the first rear longitudinal beam 10 and the second rear longitudinal beam 20 can be made of steel with high mechanical properties, such as 22MnB5 or 37MnB5. In addition, the second regions 12, 22 of the first rear longitudinal beam 10 and the second rear longitudinal beam 20 can be made of steel with lower mechanical properties, such as more ductile steel. The blanks of the first regions 11, 21 and the second regions 12, 22 of each rear longitudinal beam 10, 20 can also define the overlapping region 50. The width of the overlapping region in the longitudinal beam can be at least 10 mm, specifically between 10 mm and 50 mm (i.e., the overlapping region roughly extends across the width of the longitudinal beam portion, and the overlapping portion is 10 mm to 20 mm in the longitudinal direction of the vehicle).

[0153] In some examples, the cross member 30 can be formed from materials with different mechanical properties. For example, the blanks forming the lateral sides 31, 33 of the cross member 30 can be made of the same steel or different materials as the blanks forming the central portion 32 of the cross member 30. The materials used to manufacture the cross member 30 can be any of those previously disclosed and material, or any other suitable steel.

[0154] Figure 6B It shows that the first rear longitudinal beam 10, the second rear longitudinal beam 20 and the cross beam 30 can define a substantially U-shaped cross-section. Further, it also shows that the geometry of the cross-section of the integral rear longitudinal beam 100 can vary along its length and width. Further, the cross-section can include one or more flanges, and this can also be changed at different regions of the first rear longitudinal beam 10, the second rear longitudinal beam 20 and the cross beam 30.

[0155] In the illustrated example, it can be seen that the rear longitudinal beam can have (mounting) flanges on the inner side, while having no flanges on its outer side, or it only has flanges from the transition part to in front of the cross beam.

[0156] In the example of FIG. 6, as well as in other examples, the blanks forming the overlapping region can be joined using spot welding or laser welding. Laser welding can include using a plurality of "stitches", such as short straight welds. Laser welding can additionally or alternatively include continuous welding along one or more edges (specifically all edges) of the overlapping region.

[0157] Using longer welds instead of spot welds can avoid the stress concentration that may occur around the spot welds. Avoiding stress concentration can avoid or delay cracking when the vehicle is impacted or collided.

[0158] In cases where fluid tightness is required, using continuous welds along the edges of the overlapping region can be preferred. In some areas of the vehicle, avoiding fluid (such as liquid) leakage can be important. Using spot welds may leave some spaces between the sub-blanks or between the blanks assembled with each other to form a combined blank, and the fluid may escape through these small spaces.

[0159] Using longer welds, especially using laser welding, can also improve the stamping process and avoid potential separation between the blanks or sub-blanks during the stamping process.

[0160] Figure 7A A top view schematically showing an example of a combined blank 1000 for forming an integral rear longitudinal beam structure 100 according to the present disclosure is shown. The combined blank 1000 in this example includes four blanks 1100, 1200, 1300, 1400. The first blank 1100 and the second blank 1200 can be configured to form the rear longitudinal beam structures 10, 20, and the third blank 1300 and the fourth blank 1400 can be configured to form the cross beams 30, 40.

[0161] The blanks 1100, 1200, 1300, 1400 can be made of different materials and / or thicknesses. For example, the first blank 1100 and the second blank 1200 can be made of UHSS with a given thickness, or can be formed into a tailor-welded blank that includes a more resistant material (such as UHSS) and a more ductile material (e.g., near the load receiving end). The third blank and the fourth blank can be formed of UHSS or other steels, and each blank can have the same or different thicknesses.

[0162] All the blanks can be joined to each other to form a combined blank 1000. Then, the combined blank 1000 can be subjected to a forming operation (such as a hot stamping operation) to form the integral rear longitudinal beam structure 100 as disclosed above.

[0163] In some examples, parts of the structure (or parts of the combined blank 1000) can be subjected to different heat treatments from other parts of the structure. For example, the first parts 1110, 1210 originally belonging to the first blank 1100 and the second blank 1200 can be cooled at a high cooling rate to rapidly reduce the temperature of this part and obtain a hard martensitic microstructure; while the second parts 1120, 1220 originally belonging to the first blank 1100 and the second blank 1200 can be cooled at a lower cooling rate to obtain a softer microstructure, including, for example, bainite, ferrite, and / or pearlite.

[0164] In Figure 7A In the example shown, all the blanks 1100, 1200, 1300, 1400 have a thickness between 1 mm and 2.5 mm, but blanks with other thicknesses can also be used.

[0165] Furthermore, Figure 7A Some of the blanks 1100, 1200, 1300, 1400 in

[0166] Figure 7B and Figure 7C schematically shows a part of an example of the resulting integral rear longitudinal beam structure. In these figures, an overlapping region 50 can be seen at the transition between the longitudinal beam part 20 and the cross beam part 30.

[0167] It can be seen that the overlapping region has a considerable length and width to increase the stiffness and strength at the transition between the longitudinal beam and the cross beam. As Figure 7BAs indicated, the length of the overlapping region can be, for example, between 15 cm and 30 cm, particularly between 20 cm and 25 cm. As can be seen in the bottom view of FIG. 7, the overlapping region extends along the length of the cross beam by about 12 cm to 20 cm and extends substantially over the entire bottom of the U-shape of the longitudinal beam portion.

[0168] In this example, the width of the overlapping region corresponds to the width of the cross beam portion 30. And the width of the overlapping region can flare outwards, optionally forwards and backwards in the longitudinal beam portion, as Figure 7C shown. For example, the transition region can flare backwards and forwards by 2 cm to 10 cm, specifically by 3 cm to 8 cm.

[0169] As discussed with respect to the integral rear longitudinal beam structure 100, the composite blank 1000 can include a different number of blanks. For example, the composite blank 1000 can include two blanks, three blanks or more than four blanks.

[0170] Figure 8 A top view schematically shows another example of a composite blank 1000 for forming an integral rear longitudinal beam structure 100 according to the present disclosure. Figure 8 The composite blank in also includes four blanks 1100, 1200, 1400, 1600. The first blank 1100 and the second blank 1200 are configured to form the rear longitudinal beam structure ( Figure 1 10, 20 in), and the third blank 1400 is configured to form the cross beam ( Figure 1 30 or 40 in). Additionally, the composite blank 1000 includes a fourth blank 1600 configured to form at least a portion of the floor panel. In some examples, due to lower mechanical requirements, the fourth blank 1600 can be made of a thinner material, such as between 0.7 mm and 1.5 mm, and can have lower mechanical properties than the rest of the composite blank 1000 after forming.

[0171] Figure 9 A block diagram shows a method 200 for manufacturing an integral rear longitudinal beam structure 100 according to various examples of the present disclosure, the integral rear longitudinal beam structure 100 including a first rear longitudinal beam and a second rear longitudinal beam and one or more cross beams.

[0172] Method 200 includes providing a first blank 1110 and a second blank 1300 at block 201. The method further includes arranging the first blank 1100 and the second blank 1300 at block 202 such that the first blank 1100 partially overlaps the second blank 1300 in an overlap region 1500. Further, the method includes joining the first blank 1100 to the second sub - blank 1300 at the overlap region 1500 at block 203 to form a combined blank 1000. Additionally, the method includes heating the combined blank 1000 at least partially above an austenitizing temperature at block 204. And, method 200 includes press - hardening the heated combined blank 1000 at block 205 to form an integral rear longitudinal beam structure 100.

[0173] Further, providing the combined blank 1000 includes providing the first blank 1100 and the second blank 1300 such that the first blank 1100 partially overlaps the second blank 1300, thereby forming one or more overlap regions 1500. Additionally, the formed integral rear longitudinal beam structure 100 includes a first rear longitudinal beam 10 and a second rear longitudinal beam 20 as well as one or more cross - beams 30, 40.

[0174] As previously described, the provided method 200 allows for forming the integral rear longitudinal beam structure 100 in a single forming step. Further, the formed integral rear longitudinal beam structure 100 has improved mechanical properties, specifically in the transition portions between the sub - blanks 1100, 1200, 1300, 1400 due to the overlap regions 1500, 50.

[0175] The combined blank can be made of any type of hardenable steel, particularly boron steel as previously discussed for the integral rear longitudinal beam structure 100.

[0176] In various examples, at least one of the overlap regions 1500, 50 between the first blank 1100 and the second blank 1300 substantially corresponds to the transition portion between the longitudinal beam 10 and the cross - beam 30.

[0177] Further, method 200 can include joining the first blank 1100 and the second blank 1300 together by spot welding.

[0178] And, the heating step 202 of method 200 can include heating a first region 1110 of the combined blank 1000 differently compared to a second region 1120 of the combined blank 1000. For example, the combined blank 1000 can be heated substantially uniformly above the austenitizing temperature, and subsequently the second region 1120 of the combined blank 1000 can be cooled below the austenitizing temperature.

[0179] In various examples, the combined blank 1000 can be heated above Ac3, and portions 1120, 1220 of the combined blank 1000 can be cooled below Ac3, even below Ac1, before deforming the combined blank 1000. Other portions can be maintained above Ac3 until the combined blank 1000 is deformed, or can be temporarily cooled and then reheated above Ac3 again.

[0180] Thereby, different temperatures can result in different microstructures or strength properties being set in corresponding portions of the integral rear longitudinal beam structure 100, particularly during subsequent rapid cooling ("quenching"), for example in the die of a stamping tool.

[0181] In various examples, the combined blank is formed during the press hardening step 203 to form the integral rear longitudinal beam structure while being quenched below 400 °C, or specifically below 300 °C.

[0182] Furthermore, the method 200 can be adapted to form an integral rear longitudinal beam structure 100 having any combination of the previously discussed technical features.

[0183] Although only some examples are disclosed herein, other alternatives, modifications, uses, and / or equivalents of these examples are also possible. Also, all possible combinations of the described examples are covered. Thus, the scope of the present disclosure should not be limited by the specific examples, but should be determined only by a reasonable reading of the subsequent claims.

Claims

1. An integral rear longitudinal beam structure for a vehicle, the integral rear longitudinal beam structure comprising a first rear longitudinal beam portion, a second rear longitudinal beam portion, and one or more cross beam portions connecting the first rear longitudinal beam portion to the second rear longitudinal beam portion, wherein, the integral rear longitudinal beam structure is formed by deforming a single combined blank, and wherein, the single combined blank at least comprises a first blank, the first blank being joined to a second blank such that the first blank partially overlaps the second blank to form one or more overlapping regions, and wherein, the overlapping regions generally correspond to the transition between the first longitudinal beam portion and one of the cross beam portions and the transition between the second longitudinal beam portion and one of the cross beam portions.

2. The integral rear longitudinal beam structure according to claim 1, wherein, The integral rear longitudinal beam structure is made by hot stamping.

3. The integral rear longitudinal beam structure according to claim 1 or 2, wherein, The overlapping region extends into the longitudinal beam portion by at least 20 mm.

4. The integral rear longitudinal beam structure according to claim 3, wherein, The overlapping region extends into the longitudinal beam portion by 20 mm to 60 mm.

5. The integral rear longitudinal beam structure according to any one of claims 1 to 4, wherein, The overlapping region extends across the entire width of the cross beam portion.

6. The integral rear longitudinal beam structure according to any one of claims 1 to 5, wherein, The overlapping region extends across the entire width of the rear longitudinal beam portion at least in the transition from the longitudinal beam portion to the cross beam.

7. The integral rear longitudinal beam structure according to any one of claims 1 to 6, wherein, The area of one of the overlapping regions in the overlapping region is 20 cm 2 to 600 cm 2 Specifically, it is 30 cm 2 to 500 cm 2 More specifically, it is between 50 cm 2 and 450 cm 2 in between.

8. The integral rear longitudinal beam structure according to any one of claims 1 to 7, wherein, The first rear longitudinal beam and the second rear longitudinal beam comprise a first region configured to attach the integral rear longitudinal beam structure to a chassis, wherein the first region has an ultimate tensile strength of 1500 MPa or more.

9. The integral rear longitudinal beam structure according to any one of claims 1 to 8, wherein, The first rear longitudinal beam and the second rear longitudinal beam comprise a second region having an ultimate tensile strength between 700 MPa and 1200 MPa and a yield strength between 500 MPa and 900 MPa after hot stamping.

10. The integral rear longitudinal beam structure according to any one of claims 8 or 9, wherein, The first region and the second region have different microstructures.

11. The integral rear longitudinal beam structure according to any one of claims 1 to 10, wherein, At least one of the first rear longitudinal beam portion, the second rear longitudinal beam portion, and the cross beam portion has a generally U-shaped cross section, wherein, the U-shape has a bottom wall, a first side wall, a second side wall, a first lateral flange protruding outwardly at one end of the first side wall, and a second lateral flange protruding outwardly at one end of the second side wall.

12. The integral rear longitudinal beam structure according to claim 11, further comprising a cover plate attached to the first rear longitudinal beam portion and the second rear longitudinal beam portion and generally enclosing the U-shaped cross section.

13. The integral rear longitudinal beam structure according to any one of claims 1 to 12, wherein, The single combined blank comprises different thicknesses and / or materials.

14. The integral rear longitudinal beam structure according to any one of claims 1 to 13, further comprising at least a part of a floor panel.

15. A method for manufacturing an integral rear longitudinal beam structure for a vehicle frame according to any one of claims 1 to 14, the method comprising: providing a first blank and a second blank, arranging the first blank and the second blank such that the first blank partially overlaps the second blank in an overlapping region; joining the first blank to the second blank at the overlapping region to form a combined blank; heating the combined blank at least partially above the austenitizing temperature; and Press-hardening the heated combined blank to form the integral rear longitudinal beam structure, wherein, The formed integral rear longitudinal beam structure includes a first rear longitudinal beam portion, a second rear longitudinal beam portion, and one or more cross beam portions.

16. The method according to claim 15, wherein, The joining of the first blank and the second blank is performed by spot welding.

17. The method according to claim 15 or 16, wherein A first region of the integral rear longitudinal beam structure has an ultimate tensile strength of 1500 MPa or more after press-hardening, and a second region of the integral rear longitudinal beam structure has an ultimate tensile strength between 700 MPa and 1200 MPa after press-hardening.

18. The method according to claim 17, wherein, The first region of the combined blank is subjected to different heat treatment compared to the second region of the combined blank.

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