Integrated roof ring for vehicle framework

Abstract

The present disclosure relates to a method for manufacturing a one-piece roof ring (100) for a vehicle framework, the method including providing a plurality of blanks (1, 2, 3, 4), joining the blanks together to form a composite blank (5), and deforming the composite blank (5) to form the one-piece roof ring (100). The one-piece roof ring (100) includes two longitudinal rail portions (10, 20), each connected to a front cross member (30) and a rear cross member (40) to form a substantially closed ring shape. The disclosure further relates to the one-piece roof ring obtained by such a method.

Description

[Technical Field]

[0001] This application claims priority to European Patent Application No. 22383193.4, filed December 7, 2022.

[0002] FIELD OF THE DISCLOSURE The present disclosure relates to a one-piece roof ring for a vehicle and a method for manufacturing a one-piece roof ring for a vehicle. [Background technology]

[0003] Vehicles such as automobiles incorporate a structural framework designed to withstand all loads that the vehicle may be subjected to during its lifetime. The structural framework is further designed to withstand and absorb impacts in the event of a collision, for example with another vehicle, an obstacle, or a pedestrian.

[0004] The structural framework of a vehicle, e.g., an automobile, in this sense may include, for example, bumpers, pillars (A-pillar, B-pillar, C-pillar, D-pillar), side impact beams, rockers or sills, hinge pillars and shock absorbers.

[0005] Press hardening, also known as hot forming die quenching (HFDQ), typically uses boron steel to create stamped parts with ultra-high strength steel (UHSS) properties, such as tensile strengths of 1,500 MPa or 2,000 MPa or greater. The increased strength allows for the use of thinner gauge material, resulting in lighter weight than traditional cold-stamped mild steel parts. Throughout this disclosure, UHSS can be considered steels with ultimate tensile strengths of 1,000 MPa or greater, particularly after the press hardening process.

[0006] In the HFDQ process, the blank to be hot-formed can be heated to a predetermined temperature, for example, above the austenitizing temperature (particularly between Ac3 and, for example, the evaporation temperature of the coating on the blank). A furnace system can be used for this purpose. Depending on specific needs, the furnace system can be supplemented with additional heaters, for example, induction heaters or infrared heaters. Heating the blank reduces its strength and increases its deformability, which makes the hot stamping process easier.

[0007] There are several known ultra-high strength steels (UHSS) for hot stamping and hardening. The hot-formed blanks may be made of coated or uncoated boron steels, such as Usibor® (22MnB5), available from ArcelorMittal.

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

[0009] Hot forming of boron steels is becoming increasingly popular in the automotive industry due to their excellent strength and formability. Thus, many structural parts that were traditionally cold formed from mild steel are being replaced with hot-formed equivalents, which offer a significant increase in strength. This allows the thickness (and therefore weight) of the material to be reduced while maintaining the same strength.

[0010] To improve ductility and energy absorption in specific regions of a component, it is known to introduce softer regions within the same component. This results in locally improved ductility while maintaining the required overall high strength. By locally tailoring the microstructure and mechanical properties of specific structural components to include regions with very high strength (very hard regions), i.e., high ultimate tensile strength and high yield strength, and regions with increased ductility (softer regions), i.e., low ultimate tensile strength, low yield strength, and increased elongation before fracture, it may be possible to improve their overall energy absorption, maintain their structural integrity during crash situations, and reduce their overall weight. Such soft zones can also favorably alter the kinematic behavior of the component when it collapses upon impact.

[0011] A known method of creating highly ductile regions ("soft zones" or "soft zones") in a structural component of a vehicle involves providing a tool including 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 preheated, for example by a furnace system, to a predetermined temperature, for example above the austenitizing temperature, in order to reduce its strength, i.e., to facilitate the hot stamping process.

[0012] Die elements may be designed to operate at different temperatures to achieve different cooling rates in different regions of the part being formed during the quenching process, resulting in different material properties in the final product, such as softer regions that generally have lower ultimate tensile strength and yield strength but allow for greater elongation before fracture. For example, one die element may be cooled to quench a corresponding region of the part being fabricated at a high cooling rate, thereby rapidly reducing the part's temperature and achieving a hard martensitic microstructure. Another adjacent die element may be heated to ensure that a corresponding portion of the part being fabricated cools at a slower cooling rate, for example, to achieve a softer microstructure containing bainite, ferrite, and / or pearlite. Such regions of the part may remain at a higher temperature than the rest of the part when it exits the die.

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

[0014] UHSS can exhibit high tensile strengths of 1,500 MPa and even 2,000 MPa or more, especially after press hardening. Upon hardening, UHSS can have a martensitic microstructure. This microstructure allows for increased ultimate tensile strength and yield strength per unit weight.

[0015] In addition to the ultra-high strength steels mentioned above, more ductile steels can also be used for parts of the structural framework that require energy absorption. These steels can be used in hot stamping processes, but do not acquire a martensitic microstructure in the process. Ductibor® 1000 is an example of a suitable more ductile steel.

[0016] The upper frame of a vehicle's structural framework may be formed by connecting multiple structural components. These structural components form a roof ring, which is one of the structures that plays a role in protecting the vehicle during an impact event. A vehicle's roof ring generally comprises four beams: two longitudinal rail sections, commonly known as roof rails, and front and rear cross members, commonly known as front and rear headers. The roof rails are located between the A-pillars and C-pillars of the vehicle. The front headers are located between the A-pillars, and the rear headers are located between the C-pillars. During a collision event, the roof ring plays a key role in ensuring the integrity of the vehicle.

[0017] The four beams comprising the roof ring may have different thicknesses and may be manufactured differently. The roof rails and front header are components with a desired high rigidity, generally achieved by hot stamping ("press hardening"), to limit intrusion in the event of an impact at a relatively low weight. The rear header is typically made of a material suitable for cold stamping. After manufacturing these four beams, they are generally welded together when assembled with the rest of the vehicle framework or "body in white."

[0018] One problem encountered is that some weld spots and seams can lead to weak areas in the event of a crash. Other issues to consider are weight, manufacturability, the time required to build the vehicle, and cost.

[0019] The present disclosure provides examples of systems and methods that offer improvements over prior art roof structures. Summary of the Invention

[0020] In a first aspect, a method for manufacturing a one-piece roof ring for a vehicle structural framework is provided, the method including providing a plurality of blanks, joining the blanks to form a composite blank, and deforming the composite blank to form a one-piece roof ring, the one-piece roof ring including two longitudinal rail portions respectively connected to a front cross member and a rear cross member to form a substantially closed ring shape.

[0021] Joining blanks together to form a composite blank and then deforming the composite blank results in a lightweight, durable roof ring constructed in fewer steps. Joining the blanks together before deformation reduces post-forming welding, allowing for the production of roof rings with no or reduced heat-affected zones. A reduced heat-affected zone reduces the risk of cracking the upper frame of the structural framework in the event of a crash. All of this can increase the strength of the roof ring while reducing the thickness of the blank and reducing weak points in the final ring. Therefore, crash performance can be improved while achieving a mass reduction in the vehicle's upper frame, which can lead to the possibility of reducing the thickness of adjacent components of the roof ring.

[0022] In some examples, the plurality of blanks includes a front cross beam blank, two longitudinal beam blanks, and a rear cross beam blank. In some examples, the plurality of blanks may be made from ultra-high strength steel (UHSS), and one or more of the blanks may be made from boron steel, among others.

[0023] In some instances, blanks of different material thicknesses and / or grades may be used to meet specific strength, anti-intrusion and energy absorption requirements and to optimize weight.

[0024] In some examples, joining the blanks includes forming one or more overlap regions formed by partially overlapping the blanks with one another. In this disclosure, partially overlapping two blanks means that only a portion of the two blanks overlap.

[0025] The overlap area or areas may be arranged to counteract the reduction in material, and therefore strength, that may occur in some parts of the one-piece roof ring when compared to a solution in which the structural components are formed first and then joined to form the superstructure frame.

[0026] Alternatively, or additionally, the overlap may be placed in a location where high loads are expected, for example, by placing a patch blank within the blank.

[0027] Throughout this disclosure, front and rear cross beam blanks may be considered to be the blanks that are subsequently deformed to form the front and rear cross members of the roof ring, and similarly, longitudinal beam blanks may be considered to be the blanks that are subsequently deformed to form the longitudinal rail portions of the roof ring.

[0028] The roof rails and front and rear headers of a vehicle are structural members of the vehicle's superstructure frame. In some examples, the longitudinal rail portions included in the one-piece roof ring may be roof rail outer members of the vehicle framework, and the front and rear cross members included in the one-piece roof ring may be front and rear headers of the vehicle framework.

[0029] The one-piece roof ring may define an upper structural frame for the vehicle.

[0030] In some examples, deforming the composite blank to form the integral roof ring of the vehicle framework includes hot stamping the composite blank. Hot stamping is a process that enables suitable deformation of ultra-high strength steel to form the complex resulting structure of the integral roof ring.

[0031] In some instances, the deforming of the composite blank can be performed in a single operation. Deforming the composite blank in a single operation can improve the efficiency of the manufacturing process for the vehicle framework roof ring.

[0032] In a further aspect, there is provided a one-piece roof ring obtainable by a method according to any of the examples described herein.

[0033] Non-limiting examples of the present disclosure are described below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0034] [Figure 1] 1 shows an example of an integral roof ring for a vehicle framework. [Figure 2] 1 shows an example of a plurality of blanks before being joined to form a composite blank. [Figure 3] FIG. 1 shows an example of a schematic diagram of a composite blank formed by four joined blanks. [Figure 4] 1 shows an example of a composite blank including a patch blank. [Figure 5] 1 shows an example of a composite blank comprising five joined blanks. [Figure 6] 1 shows an example of a one-piece roof ring after deformation of the composite blank. [Figure 7] 1 shows an example of a close-up view of a bonded blank after deformation of a one-piece roof ring of a vehicle framework. [Figure 8] 1 illustrates an example of a front view of an integrated roof ring for a vehicle framework. [Figure 9]1 is a flow chart of a method for manufacturing a one-piece roof ring for a vehicle framework. DETAILED DESCRIPTION OF THE INVENTION

[0035] The drawings refer to illustrative embodiments and may be used solely as an aid in understanding the claimed subject matter and are not intended to be limiting in any way.

[0036] In these figures, the same reference numbers are used to indicate corresponding elements.

[0037] 1 is a schematic representation of a one-piece roof ring 100 of a vehicle framework according to one example of the present disclosure. The one-piece roof ring 100 includes two longitudinal rail sections 10, 20, each connected to a front cross member 30 and a rear cross member 40 to form a substantially closed ring shape.

[0038] In some examples, the one-piece roof ring 100 may be installed in the upper frame of a vehicle framework and may define the vehicle's superstructure frame. The one-piece roof ring may be joined to other portions of the vehicle framework, such as A-pillars, C-pillars, and roof panels.

[0039] The one-piece roof ring 100 may be fabricated from multiple blanks in a single deformation process. As shown schematically in FIG. 2 , the one-piece roof ring 100 may be fabricated from four blanks: a first blank 1, a second blank 2, a third blank 3, and a fourth blank 4. The first and second blanks 1, 2 may be longitudinal beam blanks 1, 2, and the third and fourth blanks 3, 4 may be cross beam blanks 3, 4. The third blank 3 may be a front cross beam blank 3, and the fourth blank 4 may be a rear cross beam blank 4. The blanks may be joined to form a composite blank. The longitudinal beam blanks 1, 2 may be joined to the front cross beam blank 3 and the rear cross beam blank 4. Thus, a composite blank 5 including four blanks 1, 2, 3, and 4 may be formed, as shown in FIG. 3 .

[0040] In the next step, the composite blank 5 can be deformed. In particular, the composite blank can be heated in a furnace or alternative heating system to above the austenitizing temperature, for example, about 900-920°C. The composite blank can then be deformed and hardened in a press. In particular, rapid cooling above the critical cooling rate of the composite blank can achieve a martensitic microstructure and high ultimate tensile strength and high yield strength.

[0041] In some instances, blanks can be joined together by forming one or more overlapping regions 6 formed by partially overlapping the blanks with one another. That is, one blank is placed only partially on top of another blank, and then the blanks are joined together. The overlapping regions thus acquire an increased thickness compared to the rest of the blank. Such increased thickness can be used to tailor mechanical properties as needed, for example, to provide localized reinforcement in areas where increased strength and / or stiffness is required.

[0042] In some examples, the overlap region 6 may be formed at or near the junction or transition between the front cross member 30 and one of the longitudinal rail sections 10, 20. When different components are combined into the one-piece roof ring 100 by deforming a single blank, these junctions require less material than if the components were manufactured separately and then welded together. By providing overlap regions 6 at or near these junctions, extra material can be added, thus maintaining the mechanical behavior and kinematic properties of the roof ring 100. In other examples, the composite blank may be formed by edge-to-edge welding of blanks (such as a tailored welded blank), or the composite blank may be formed by both using overlapping blanks in certain areas and edge-to-edge welding in other areas.

[0043] In some examples, the overlap region 6 may be formed substantially within the front member 30. That is, in these examples, the blanks comprising the longitudinal beams overlap with the blank(s) comprising the front member 30. In the resulting product, the overlap may be located completely or nearly completely within the front member 30 of the resulting one-piece roof ring. In other examples, the overlap region 6 may be formed at each of the junctions or transitions of the front and rear cross members 30, 40 with the two longitudinal rail portions 10, 20. The overlap may be achieved by either laser welding, arc welding, or spot welding.

[0044] In some examples, as shown in FIG. 3 , joining the blanks includes joining a first end of a first longitudinal beam blank 1 to a first end of a front cross beam blank 3 and a second end of the first longitudinal beam blank 1 to a first end of a rear cross beam blank 4, and joining a first end of a second longitudinal beam blank 2 to a second end of the front cross beam blank 3 and a second end of the second longitudinal beam blank 2 to a second end of the rear cross beam blank 4. The blanks may be welded together, for example, by laser welding or spot welding. Region 6 where the blanks are joined can be seen in FIG. 3 .

[0045] In some examples, joining the blanks to form the composite blank 5 includes providing a composite blank 5 having a substantially rectangular (annular) shape.

[0046] In some examples, the longitudinal beam blanks 1, 2 may be joined to the cross beam blanks 3, 4 on the outside / top side of the roof ring. In other examples, the longitudinal beam blanks 1, 2 may be joined to the cross beam blanks 3, 4 on the inside / bottom side of the roof ring.

[0047] In some examples, the overlap region 6 may have a length L1 corresponding to the width of the longitudinal rail portions 10, 20 and may have a width W1 of at least 5 cm. In some examples, the overlap region 6 may be formed at each of the joints of the front and rear cross members 30, 40 with the two longitudinal rail portions 10, 20. The appropriate dimensions of the overlap region 6 may be selected taking into account the requirements for weldability, strength, and rigidity. A larger overlap region 6 means an increase in thickness over a larger area, and therefore an increase in local strength and rigidity in the roof ring 100.

[0048] In other examples, the multiple blanks may be formed by multiple blanks or sub-blanks, for example, of different thicknesses and / or materials. In these examples, the multiple blanks forming the longitudinal beam blank and / or cross beam blank may be tailored welded blanks (TWBs). The TWBs may be formed by joining the sub-blanks by edge-to-edge welding, and the welding may include laser welding. In other examples, the multiple blanks forming the longitudinal beam blanks 1, 2 and / or cross beam blanks 3, 4 may be joined by forming one or more overlap regions 6 formed by partially overlapping the blanks with each other. In these cases, laser welding, arc welding, or spot welding may be used.

[0049] As shown schematically in FIG. 4, in some examples, a patch blank 7 can be joined to at least one of multiple blanks that can form a composite blank 5. A patch blank may be considered herein as a blank that completely overlaps another blank, i.e., the patch blank may be positioned completely within the perimeter of another blank. The patch blank can be joined to the other blank by welding, for example, spot welding or remote laser welding. The resulting combination of a "basic" blank and a patch blank may be referred to as a "patchwork blank."

[0050] The patch blank 7 may be added to a substantially central portion of one of the blanks. The patch blank 7 may be added as a reinforcement to increase the strength of a particular area of ​​the composite blank 5. The patch blank 7 may be added to an area of ​​the roof ring where additional strength may be needed, i.e., where high loads may be expected. In some examples, the patch blank 7 may be positioned within the front and / or rear cross beam blanks 3, 4. The patch blank 7 may be positioned in a substantially central portion of the front and / or rear cross beam blanks 3, 4. The patch blank 7 may also be positioned within the longitudinal beam blanks 1, 2, for example, in an area above the B-pillar of the vehicle. The patch blank 7 may be positioned in a substantially central portion of the longitudinal beam blanks 1, 2.

[0051] The patch blank 7 may be joined to the longitudinal beam blanks 1, 2 and / or cross beam blanks 3, 4 by overlapping one of the blanks with the other and using spot welding. In other examples, alternative welding techniques may be used, for example laser welding or arc welding.

[0052] As shown schematically in FIG. 5, the one-piece roof ring may include one or more additional cross members positioned between the front and rear cross members. In some examples, as in the example of FIG. 5, the one-piece roof ring 100 may be fabricated from a composite blank comprised of five blanks. For example, in addition to the blanks shown in FIGS. 2 and 3, the composite blank 5 may include a central cross beam blank 8 positioned between the front cross beam blank 3 and the rear cross beam blank 4 and extending laterally from longitudinal beam blank 1 to longitudinal beam blank 2. The central cross beam blank 8 may be joined to the longitudinal beam blanks 1 and 2, for example, by partially overlapping the blanks with each other. The central cross member of the one-piece roof ring may provide enhanced crash performance and a lighter vehicle superstructure frame.

[0053] In the example of FIG. 5, the overlap region 6 formed by partially overlapping the front and rear cross beam blanks 3, 4 with the longitudinal beam blanks 1, 2 can have a width W1 that is at least 50% of the width of the front and rear cross beam blanks 3, 4. In this example, a larger portion of the longitudinal beam blanks 1, 2 can overlap with the cross beam blanks 3, 4 compared to the example of FIG. 3. In this case, the overlap region occupies part of the longitudinal beam as well as part of the rear cross member, rather than being completely disposed within the longitudinal beam. The wider area of ​​the one-piece roof ring can increase rigidity, and the larger size of the overlap region 6 allows it to withstand higher loads.

[0054] In this particular example, the patch blank 7 may be located in a substantially central portion of the front cross beam blank 3. In other examples, the patch blank 7 may be added to the longitudinal beam blanks 1, 2 to further reinforce specific areas of those blanks. In some examples, the patch blank 7 may be located in a substantially central portion of the longitudinal beam blanks 1, 2 overlapping a portion of the central cross beam blank 8.

[0055] In some examples, the blanks forming the composite blank 5 may be made from different materials. In some examples, blanks 1, 2, 3, and 4 may be made from ultra-high strength steel (UHSS). Boron steel, such as 22MnB5, or other steel compositions previously mentioned or referenced, may be suitable UHSS. These blanks, such as boron steel blanks, may include an aluminum silicon coating or a zinc coating.

[0056] Usibor® 1500P is an example of a 22MnB5 steel. The composition of Usibor® is summarized below in weight percent (the remainder is iron (Fe) and impurities): Maximum carbon (C) (%): 0.25 Maximum silicon (Si) (%): 0.4 Maximum manganese (Mn) (%): 1.4 Maximum phosphorus (P) (%): 0.03 Maximum sulfur (S) (%): 0.01 Aluminum (Al) (%): 0.01 to 0.1 Maximum Titanium (Ti) (%): 0.05 Maximum Niobium (Nb) (%): 0.01 Maximum copper (Cu)(%):0.20 Maximum boron (B) (%): 0.005 Maximum Chromium (Cr) (%): 0.35

[0057] Usibor® 1500P, for example, may have a yield strength of 1,100 MPa and an ultimate tensile strength of 1,500 MPa.

[0058] Usibor® 2000 is another boron steel with even higher strength. The yield strength of Usibor® 2000 may be 1,400 MPa or greater, and the ultimate tensile strength may be greater than 1,800 MPa. The composition of Usibor® 2000 is summarized below in weight percent (the remainder is iron (Fe) and impurities): Maximum carbon (C) (%): 0.36 Maximum silicon (Si) (%): 0.8 Maximum manganese (Mn) (%): 0.8 Maximum phosphorus (P) (%): 0.03 Maximum sulfur (S) (%): 0.01 Aluminum (Al) (%): 0.01 to 0.06 Maximum Titanium (Ti) (%): 0.07 Maximum Niobium (Nb) (%): 0.07 Maximum copper (Cu)(%):0.20 Maximum boron (B) (%): 0.005 Maximum Chromium (Cr) (%): 0.50 Maximum Molybdenum (Mb) (%): 0.50

[0059] The blanks forming composite blank 5 can include different materials and / or thicknesses. For example, Usibor® (e.g., Usibor® 1500 and / or Usibor® 2000) blanks can be used in the blanks forming composite blank 5. When these types of materials are used in the hot forming and subsequent quenching process, a predominantly martensitic structure is obtained due to Usibor®. One or more of the blanks can also be made from a different material, for example, Ductibor® 1000.

[0060] Ductibor® 1000 is another material used in hot stamping to increase elongation compared to Usibor® 1500 and Usibor® 2000. The yield strength of Ductibor® 1000 may be 800 MPa or greater, and the ultimate tensile strength may be 1000 MPa or greater. The components of Ductibor® 1000 are summarized below in weight percent (the remainder being iron (Fe) and impurities): Maximum carbon (C) (%): 0.10 Maximum silicon (Si) (%): 0.6 Maximum manganese (Mn) (%): 1.8 Maximum phosphorus (P) (%): 0.03 Maximum sulfur (S) (%): 0.01 Aluminum (Al) (%): 0.01 to 0.1 Maximum Titanium (Ti) (%): 0.05 Maximum Niobium (Nb) (%): 0.10 Maximum copper (Cu)(%):0.20 Maximum boron (B) (%): 0.005 Maximum Chromium (Cr) (%): 0.20

[0061] In some examples, the one-piece roof ring 100 can include regions having different ultimate tensile strengths according to any of the examples described herein. In some of these examples, different materials can be used in the composite blank.

[0062] In some of these examples, regions with different ultimate tensile strengths may have different microstructures.

[0063] Different microstructures may be created in the hot-formed roof ring. These different microstructures may be created by heating the composite blank 5 above the austenitizing temperature and then controlling the cooling of the composite blank 5 while forming the composite blank 5 to form the vehicle framework roof ring 100. The cooling of different regions of the composite blank 5 may be controlled by providing heaters in zones of the forming tool. Thus, the integral roof ring 100 includes zones having a predominantly martensitic structure and zones containing ferrite, pearlite, or bainite, or mixtures thereof. Alternatively, different microstructures may be created by partially heating a portion of the press-hardened integral roof ring, for example, using a laser beam, to transform the predominantly martensitic structure into a structure containing ferrite and / or pearlite and / or bainite and / or tempered martensite, and mixtures thereof. The tensile strength of the predominantly martensitic structure may be greater than 1400 MPa, specifically greater than 1500 MPa.

[0064] Thus, the one-piece roof ring 100 can be made from a material that can be effective in absorbing energy during an impact. In some examples, the longitudinal beam blanks 1, 2 may be made from at least ultra-high strength steel.

[0065] The longitudinal rail portions 10, 20 may have a thickness of 0.5 mm to 2.5 mm, specifically 1 mm to 1.8 mm. The longitudinal rail portions 10 may have an ultimate tensile strength of 1000 to 2000 MPa, specifically 1500 to 2000 MPa. The longitudinal rail portions 10, 20 may be outer roof rails of a vehicle superstructure frame.

[0066] In some examples, the cross beam blanks 3, 4 may be made from at least ultra high strength steel.

[0067] The thickness of the cross members 30, 40 may be between 0.5 mm and 2.5 mm, specifically between 1 mm and 1.8 mm. The overlap region may have a thickness between 2 and 5 mm, specifically between 2 and 3.8 mm.

[0068] The front and rear cross members 30, 40 may have an ultimate tensile strength of 1000 to 2000 MPa, specifically 1500 to 2000 MPa. The front and rear cross members 10, 20 may be front and rear headers of a vehicle superstructure frame.

[0069] In some examples, the thickness of the front and rear cross members 30, 40 may be less than the thickness of the longitudinal rails 10, 20. In other examples, the thickness of the front and rear cross members 30, 40 may be equal to the thickness of the longitudinal rails 10, 20.

[0070] In some examples, joining the blanks together includes welding the blanks together. In some examples, the blanks may be welded by spot welding and / or laser welding. In some examples, the composite blank formed by joining the blanks may be a tailored welded blank. Joining the blanks before deformation may facilitate joining because the blanks are substantially flat when joined. Welding the blanks before the deformation process by laser and / or spot welding may be efficient and accurate.

[0071] FIG. 6 shows a schematic diagram of an example of joined blanks after deformation. In this example, longitudinal beam blanks 1, 2 may be joined to cross beam blanks 3, 4 by overlapping one of the blanks with the other and using spot welding prior to deformation. A close-up of the overlap region 6 at the joint between the front cross member 30 and the longitudinal rail section 10 can be seen in FIG. 7. In other examples, joining the blanks to one another may include forming one or more overlap regions 6 formed by partially overlapping the longitudinal beam blanks 1, 2 with the cross beam blanks 3, 4 by laser welding or spot welding.

[0072] Joining the blanks can result in weld seams or spots, which are critical areas that can easily break in the event of a vehicle collision. Post-joining deformation ensures that weld seams or spots do not exist between the blanks, providing a one-piece roof ring 100 that is more resistant to crash events than other superstructure frames in which the structural components are first formed and then joined. The danger posed by these weld seams or spots disappears within the one-piece roof ring 100, thereby reducing the risk of cracking of the one-piece roof ring 100 in a crash event. Furthermore, the one-piece roof ring 100 can reduce the time required to build a vehicle and allow the thickness of adjacent components of the roof ring 100 to be reduced without compromising the thickness of its structural elements.

[0073] In some examples, deforming the composite blank 5 to form the one-piece roof ring 100 may include hot forming or hot stamping the composite blank 5. A schematic front view of the hot-formed one-piece roof ring 100 can be seen in FIG.

[0074] In some examples, hot forming may include heating the composite blank 5 above the austenitizing temperature and then forming the composite blank 5 to create the one-piece roof ring 100. In some examples, forming may include two or more forming steps. These forming steps may include, for example, forming, trimming, or cutting, and may be performed in a single multi-stage press. Examples of multi-stage presses are known, for example, from U.S. Pat. No. 9,492,859 and WO2016142367.

[0075] Deformation may involve hot forming, i.e., heating the composite blank 5 in an oven, possibly above the austenitizing temperature, particularly above Ac3. After heating in the oven, the composite blank 5 may be transferred to a press, where the composite blank 5 is deformed to obtain the final shape of the one-piece roof ring 100. Quenching may occur during and immediately after forming. In particular, quenching may involve cooling above a critical cooling rate to obtain a martensitic microstructure. In some instances, quenching may be avoided in selected portions of the roof ring.

[0076] In some instances, the deformation is performed in a single operation. Deformation of the composite blank 5 can provide a one-piece roof ring 100 including two longitudinal rail sections 10, 20, each connected to a front cross member 30 and a rear cross member 40 to form a substantially closed ring shape.

[0077] In some examples, a substantially ring-shaped roof ring 100 comprising a front cross member 30, a rear cross member 40, a first longitudinal rail portion 10, and a second longitudinal rail portion 20 may be fabricated by deforming a single blank.

[0078] The one-piece roof ring 100 of the present disclosure can have improved crashworthiness and can be manufactured using fewer processes, thereby improving crash performance while reducing the mass and construction complexity of the vehicle's structural frame.

[0079] 9 depicts a flowchart of a method for manufacturing a one-piece roof ring for a vehicle framework 200. The method includes providing a plurality of blanks 201, joining the blanks together to form a composite blank 202, and deforming the composite blank to form a one-piece roof ring 203.

[0080] In some examples, providing the plurality of blanks 201 may include providing two longitudinal beam blanks 1, 2, a front cross beam blank 3, and a rear cross beam blank 4. In some examples, the plurality of blanks forming the composite blank 5 may be made from different materials. In some examples, the longitudinal beam blanks 1, 2 and the front and rear cross beam blanks 3, 4 may be made from ultra-high strength steel.

[0081] In some examples, joining the blanks together to form the composite blank 202 may include forming one or more overlap regions 6 formed by partially overlapping the blanks with one another. The overlap region 6 may be formed at or near the junction or transition between the front cross member 30 and one of the longitudinal rail sections 10, 20. An overlap region 6 may be formed at each of the junctions of the front and rear cross members 30, 40 with the two longitudinal rail sections 10, 20.

[0082] Deforming the composite blank to form the integral roof ring 203 may include hot forming or hot stamping the composite blank 5. Different microstructures may be created in the hot-formed roof ring. These different microstructures may be created by heating the composite blank 5 above the austenitizing temperature. In some examples, quenching may occur during and after forming. Quenching may include cooling above a critical cooling rate to achieve a martensitic microstructure.

[0083] In some examples, the different microstructures may be obtained by heating the composite blank 5 above the austenitizing temperature and then controlling the cooling of the composite blank 5 while forming the composite blank 5 to form the one-piece roof ring 100. In some examples, quenching may be avoided in selected portions of the one-piece roof ring 100.

[0084] In some examples, deforming the composite blank to form the one-piece roof ring 203 can be performed in a single operation. The one-piece roof ring 100 formed by deforming the composite blank 203 includes two longitudinal rail portions that are each connected to a front cross member and a rear cross member to form a substantially closed ring shape.

[0085] For completeness, various aspects of the disclosure are set forth in the following numbered clauses. Clause 1. A method for manufacturing a one-piece roof ring 100 for a vehicle framework, comprising: Providing multiple blanks (1, 2, 3, 4); joining the blanks to form a composite blank (5); and deforming the composite blank (5) to form a one-piece roof ring (100); A method for manufacturing a one-piece roof ring (100), the one-piece roof ring (100) including two longitudinal rail portions (10, 20) each connected to a front cross member (30) and a rear cross member (40) to form a substantially closed ring shape. Clause 2. A method for manufacturing a one-piece roof ring (100) as described in clause 1, wherein joining the blanks includes forming one or more overlap regions (6) formed by partially overlapping the blanks with each other. Clause 3. A method for manufacturing an integral roof ring (100) as described in clause 2, wherein one of the overlap regions (6) is formed at the joint between the front cross member (30) and one of the longitudinal rail portions (10, 20). Clause 4. A method for manufacturing a one-piece roof ring (100) according to clause 3, wherein the overlap region (6) is formed substantially within the front cross member (30). Clause 5. A method for manufacturing an integral roof ring (100) according to clause 4, wherein the overlap region (6) has a length L1 corresponding to the width of the longitudinal rail portions (10, 20) and a width W1 of at least 5 cm. Clause 6. A method for manufacturing a one-piece roof ring (100) according to any one of clauses 3 to 5, wherein an overlap region (6) is formed at each of the joints of the front and rear cross members (30, 40) with the two longitudinal rail portions (10, 20). Clause 7. A method for manufacturing a one-piece roof ring (100) according to any one of clauses 1 to 6, wherein joining the blanks comprises welding the blanks to one another. Clause 8. A method for manufacturing a one-piece roof ring (100) according to clause 7, wherein the welding comprises resistance spot welding and / or laser welding. Clause 9. A method for manufacturing a one-piece roof ring (100) according to any one of clauses 1 to 8, wherein deforming the composite blank (5) to form the one-piece roof ring (100) comprises hot stamping the composite blank (5). Clause 10. A method for manufacturing a one-piece roof ring (100) according to any one of clauses 1 to 9, wherein the deformation is carried out in one operation. Clause 11. A method for manufacturing a one-piece roof ring (100) according to any one of clauses 1 to 10, wherein the two longitudinal rail sections (10, 20) comprise outer roof rails and the front and rear cross members (30, 40) comprise front and rear headers of a vehicle framework. Clause 12. A method for manufacturing a one-piece roof ring (100) according to any one of clauses 1 to 11, wherein the plurality of blanks (1, 2, 3, 4) comprises two longitudinal beam blanks (1, 2) and two cross beam blanks (3, 4). Clause 13. A method for manufacturing a one-piece roof ring (100) according to clause 12, wherein the plurality of blanks (1, 2, 3, 4) further comprises a central beam blank (8). Clause 14. A method for manufacturing a one-piece roof ring (100) according to any one of clauses 1 to 13, wherein the patch blank (7) is joined to at least one of the plurality of blanks (1, 2, 3, 4) to form a composite blank (5). Clause 15. A method for manufacturing a one-piece roof ring (100) according to clause 14, wherein the patch blank (7) is placed within the front and / or rear cross beam blanks (3, 4). Clause 16. A method for manufacturing a one-piece roof ring (100) according to clause 15, wherein the patch blank (7) is positioned in a substantially central portion of the front and / or rear cross beam blank (3, 4). Clause 17. A method for manufacturing a one-piece roof ring (100) according to any one of clauses 1 to 16, wherein the thickness of the cross members (30, 40) is less than the thickness of the longitudinal rail portions (10, 20). Clause 18. A method for manufacturing a one-piece roof ring (100) according to any one of clauses 1 to 17, wherein the thickness of the longitudinal rail portions (10, 20) and / or the thickness of the cross members (30, 40) is between 0.5 mm and 2.5 mm, in particular between 1 mm and 1.8 mm. Clause 19. A method for manufacturing a one-piece roof ring (100) according to any one of clauses 1 to 18, wherein the plurality of blanks (1, 2, 3, 4) are made from ultra-high strength steel. Clause 20. A method for manufacturing a one-piece roof ring (100) according to any one of clauses 1 to 19, wherein the one-piece roof ring (100) has a tensile strength of 1500 to 2000 MPa. Clause 21. A one-piece roof ring (100) obtainable by the method according to any one of clauses 1 to 20. Clause 22. Substantially ring-shaped; A front cross member (30); A rear cross member (40), A first longitudinal rail portion (10) and a second longitudinal rail portion (20), The roof ring (100) is made by deforming a single blank. The roof ring (100) is for a structural framework of a vehicle. Clause 23. The one-piece roof ring (100) of clause 21, wherein the one-piece roof ring (100) is part of the upper frame of the vehicle. Clause 24. A vehicle equipped with an integral roof ring (100) according to clause 21 or 22.

[0086] While only a few examples are disclosed herein, other alternatives, modifications, uses, and / or equivalents are possible. Moreover, all possible combinations of the examples described are also covered. Therefore, the scope of the present disclosure should not be limited by the specific examples, but should be determined solely by a fair reading of the appended claims.

Claims

1. A method for manufacturing a one-piece roof ring (100) for a vehicle framework, comprising: providing a plurality of blanks (1, 2, 3, 4); joining said blanks to form a composite blank (5); and deforming the composite blank (5) to form the one-piece roof ring (100); A method for manufacturing a one-piece roof ring (100), wherein the one-piece roof ring (100) includes two longitudinal rail portions (10, 20) each connected to a front cross member (30) and a rear cross member (40) to form a substantially closed ring shape.

2. 2. The method for manufacturing a one-piece roof ring (100) according to claim 1, wherein joining the blanks includes forming one or more overlap regions (6) formed by partially overlapping the blanks with each other.

3. 3. The method for manufacturing an integrated roof ring (100) according to claim 2, wherein one of the overlapping regions (6) is formed at a joint between the front cross member (30) and one of the longitudinal rail portions (10, 20).

4. 4. The method for manufacturing a one-piece roof ring (100) according to claim 3, wherein the overlap region (6) is formed substantially within the front cross member (30).

5. The overlapping area (6) has a length L corresponding to the width of the longitudinal rail portions (10, 20). １ and having a width W of at least 5 cm １ 5. The method for manufacturing a one-piece roof ring (100) according to claim 4, comprising:

6. 6. A method for manufacturing an integral roof ring (100) according to any one of claims 3 to 5, wherein an overlap region (6) is formed at each of the joints of the front and rear cross members (30, 40) with the two longitudinal rail portions (10, 20).

7. 7. A method for manufacturing a one-piece roof ring (100) according to any one of claims 1 to 6, wherein joining the blanks comprises welding the blanks together, optionally comprising resistance spot welding and / or laser welding.

8. 8. The method for manufacturing a one-piece roof ring (100) according to any one of claims 1 to 7, wherein deforming the composite blank (5) to form the one-piece roof ring (100) comprises hot stamping the composite blank (5).

9. 9. A method for manufacturing a one-piece roof ring (100) according to any one of claims 1 to 8, wherein the plurality of blanks (1, 2, 3, 4) comprises two longitudinal beam blanks (1, 2) and two cross beam blanks (3, 4).

10. 10. A method for manufacturing an integral roof ring (100) according to any one of claims 1 to 9, wherein a patch blank (7) is joined to at least one of the plurality of blanks (1, 2, 3, 4) to form the composite blank (5), and optionally the patch blank (7) is positioned within the front and / or rear cross beam blank (3, 4).

11. 11. A method for manufacturing an integral roof ring (100) according to claim 10, wherein the patch blank (7) is arranged in a substantially central portion of the front and / or rear cross beam blank (3, 4).

12. 12. A method for manufacturing a one-piece roof ring (100) according to any one of claims 1 to 11, wherein the thickness of the cross members (30, 40) is less than the thickness of the longitudinal rail portions (10, 20).

13. The method for manufacturing a one-piece roof ring (100) according to any one of claims 1 to 12, wherein the one-piece roof ring (100) has a tensile strength of 1500 to 2000 MPa.

14. A one-piece roof ring (100) obtainable by the method according to any one of claims 1 to 13.

15. having a substantially ring shape; A front cross member (30); A rear cross member (40); A first longitudinal rail portion (10) and a second longitudinal rail portion (20), A roof ring (100) for a structural framework of a vehicle, said roof ring (100) being made by deforming a single blank.

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