Reinforcing member for cold forming and parts manufactured using the same

Abstract

According to one embodiment, a cold-forming reinforcing member includes a blank member and a reinforcing patch member that is provided to cover at least a portion of the blank member and is connected to the blank member by a plurality of welds, and the heat-affected zone formed around the welds in the blank member is located entirely within an area corresponding to the reinforcing patch member, and the heat-affected zone formed around a first weld among the welds may be formed in contact with a center point of a second weld adjacent to the first weld or spaced apart from the center point of the second weld.

Description

[Technical Field]

[0001] The present invention relates to a cold-forming reinforcing member and a component manufactured therefrom. [Background technology]

[0002] Recently, research into weight reduction has been progressing not only to comply with greenhouse gas emission regulations but also to reduce the weight of environmentally friendly vehicles. For example, the use of plastics, aluminum, and multi-materials has been expanding, but the cost of weight reduction is relatively high and recycling is difficult. Therefore, the use of giga-class steel has been considered, but there are issues that need to be resolved, such as formability and processing costs. Summary of the Invention [Problem to be solved by the invention]

[0003] SUMMARY OF THE INVENTION An object of the present invention is to provide a reinforcing member for cold forming that can prevent damage to welded joints even during cold forming performed at room temperature, and a part manufactured using the same. [Means for solving the problem]

[0004] According to one embodiment, a cold-forming reinforcing member includes a blank member and a reinforcing patch member that is provided to cover at least a portion of the blank member and is connected to the blank member by a plurality of welds, and the heat-affected zone formed around the welds in the blank member is located entirely within an area corresponding to the reinforcing patch member, and the heat-affected zone formed around a first weld among the welds may be formed in contact with a center point of a second weld adjacent to the first weld or spaced apart from the center point of the second weld.

[0005] Specifically, the center point of the welded portion of the cold-forming reinforcing member according to one embodiment may be formed at a position spaced apart from the edge of the reinforcing patch member by a distance ranging from 12 mm to 30 mm.

[0006] In addition, the distance between the first welded portion and the second welded portion of the cold-forming reinforcing member according to an embodiment may be formed in a range of 12 mm to 30 mm. Here, the welded portion of the cold-forming reinforcing member according to an embodiment may be formed by spot welding using a welding head.

[0007] The welds of the cold-forming reinforcing member according to an embodiment may be arranged in a plurality along an edge of the reinforcing patch member to form an outer row, and the welds of the cold-forming reinforcing member according to an embodiment may be arranged in a plurality of lines inside the outer row to form an inner row.

[0008] The blank member or the reinforcing patch member of the cold-forming reinforcing member according to an embodiment may be provided as one of a steel plate, an aluminum plate, a magnesium plate, and a titanium plate, and the blank member and the reinforcing patch member of the cold-forming reinforcing member according to an embodiment may be provided as a material having a tensile strength of 500 MPa to 2500 MPa.

[0009] According to an embodiment, the part may be manufactured by forming the cold-forming reinforcing member at room temperature. Also, according to an embodiment, the part may be manufactured by forming at least one bending portion in the cold-forming reinforcing member.

[0010] Here, according to one embodiment, the bent portion of the component may be formed with a radius of curvature that is 2 to 10 times larger than the sum of the thickness of the blank member and the thickness of the reinforcing patch member. [Effects of the Invention]

[0011] The reinforcing member for cold forming and the part manufactured using the same according to the present invention are effective in preventing damage to welded joints even during cold forming performed at room temperature.

[0012] However, the various beneficial advantages and effects of the present invention are not limited to the above, and can be more easily understood in the course of describing specific embodiments of the present invention. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a plan view illustrating a cold-forming reinforcing member according to one embodiment. [Figure 2] FIG. 2 is an enlarged plan view of part "A" in FIG. [Figure 3] 1 is a graph showing the relationship between offset distance and load bearing capacity or the relationship between spacing between welds and load bearing capacity in a cold-forming reinforcing member according to one embodiment. [Figure 4] FIG. 1 is a perspective view of a part manufactured using a cold-forming reinforcing member according to one embodiment. [Figure 5] 1 is a cross-sectional side view of a part manufactured using a cold-forming reinforcing member according to one embodiment, showing a portion of a bending portion. DETAILED DESCRIPTION OF THE INVENTION

[0014] To reduce costs and weight, global mass-production automakers are increasingly using hot-formed steel and cold giga-grade steel. Hot-formed steel has the drawbacks of requiring large heating equipment and high initial capital investment costs. Because hot-formed steel is formed under relatively high-temperature conditions with high ductility, it offers superior formability and shape fixability compared to cold-formed steel, making it the preferred choice for new car platforms. However, research is needed to find ways to replace hot-formed steel with cold-formed steel to reduce costs.

[0015] For example, collision components such as side members or center pillars of automobile bodies employ a tailoring technique that combines different strengths, thicknesses, or both within a single component to maximize collision performance. Among these tailoring techniques, a patch-worked blank (PWB) technique, in which a reinforcing patch member is attached to a portion of a blank component by spot welding and then molded into a single mold, is applied to cold or hot press-formed components. However, in the case of components that require bending deformation, such as automobile collision support components, a large shear force is applied to the spot-welded joint connecting the blank component and the reinforcing patch member due to the difference in deformation between the blank component and the reinforcing patch member, which can result in damage to the welded joint.

[0016] In particular, cold forming, which is performed at room temperature, does not provide high ductility, which increases the risk of weld fracture. Therefore, the present applicant proposes a reinforcing member for cold forming that reduces the risk of weld fracture even during cold forming, and a part manufactured using the same.

[0017] Hereinafter, embodiments will be described with reference to the accompanying drawings. However, the embodiments may be modified in various different forms, and the scope of the embodiments is not limited to the embodiments described below. The shapes and sizes of elements in the drawings may be exaggerated for clarity.

[0018] Furthermore, the singular expression includes the plural expression unless the context clearly indicates otherwise. Throughout the specification, the same reference numbers or reference numbers given in a similar manner refer to the same components or corresponding components.

[0019] Fig. 1 is a plan view showing a cold-forming reinforcing member of an embodiment, and Fig. 2 is an enlarged plan view of part "A" in Fig. 1. Referring to Fig. 1, the cold-forming reinforcing member according to one embodiment can include a blank member 1 and a reinforcing patch member 2. The reinforcing patch member 2 is provided so as to cover at least a portion of the blank member 1, and can be joined to the blank member 1 by a plurality of welds 3.

[0020] The weld 3 is formed when at least one of the blank member 1 and the reinforcing patch member 2 is melted and solidified by the welding head of a welding machine to join the blank member 1 and the reinforcing patch member 2. Heat generated during the formation of the weld 3 forms a heat affected zone 4 (HAZ) around the weld 3. The heat affected zone 4 is a portion where the metal structure and mechanical properties change due to the heat during welding, but is not melted.

[0021] The entire area of ​​the heat-affected zone 4 formed around the welded portion 3 is located within the area corresponding to the reinforcing patch member 2. Furthermore, the heat-affected zone 4 formed around the first welded portion 3a of the welded portion 3 is in contact with the center point Cb of the second welded portion 3b adjacent to the first welded portion 3a, or is formed away from the center point Cb of the second welded portion. Here, the center point C of the welded portion 3 is the center of a circle whose diameter is defined by the two points farthest from the welded portion 3a.

[0022] For this reason, the position of the weld 3 is limited to an offset distance S, which is the distance from the edge E of the reinforcing patch member 2 to the center point C of the weld 3. The minimum value of the offset distance S is limited to the value when the outermost region of the heat-affected zone 4 contacts the edge E of the reinforcing patch member 2. This allows a fused nugget to be formed stably when the weld 3 is formed. In addition, the bonding strength of the weld 3 formed by solidifying the fused nugget can be formed to exceed a required standard value.

[0023] As described above, the reinforcing member for cold forming according to one embodiment and the part manufactured using the same can prevent fracture of the welded portion 3 even when manufactured by cold forming, and can ensure the required load bearing capacity.

[0024] FIG. 3 is a graph showing the relationship between the offset distance S and the load bearing capacity or the relationship between the distance G between the welded portions 3 and the load bearing capacity in the cold-forming reinforcing member of the embodiment.

[0025] 3(a) is a graph showing the relationship between the load bearing capacity and the offset distance S from the end E of the reinforcing patch member 2 to the center point C of the welded portion 3. Referring to the graph, according to one embodiment, the center point C of the welded portion 3 may be formed at a position spaced apart from the end E of the reinforcing patch member 2 by a distance ranging from 12 mm to 30 mm.

[0026] As can be seen from this graph, the required load-bearing capacity can be ensured when the offset distance S from the end E of the reinforcing patch member 2 to the center point C of the weld 3 is in the range of 12 mm to 30 mm. The minimum offset distance S, 12 mm, is determined based on the conditions under which a fused nugget can be formed. For example, when the diameter of the welding head is 8 mm, the diameter WD of the weld 3 formed in this case is 8 mm. The heat-affected zone 4 has a center point C that is the same as the center point C of the weld 3 and forms a donut-shaped region with a diameter ZD of 24 mm. In this relationship, the heat-affected zone 4 can be completely formed only when the center point C is located at least 12 mm away from the end E of the reinforcing patch member 2. Furthermore, a fused nugget can also be completely formed in this case.

[0027] The maximum offset distance S of 30 mm is the maximum value required to satisfy the load-bearing capacity standard. As an example, consider the case where the blank member 1 has a tensile strength of 1200 MPa, a thickness t1 of 1.5 mm, and a reinforcing patch member 2 has a tensile strength of 900 MPa and a thickness t2 of 1.2 mm. The cold-formed reinforcing member formed by joining the blank member 1 and the reinforcing patch member 2 with the weld 3 has a thickness of 2.7 mm and a tensile strength of 1070 MPa ([1200 × 1.5 + 900 × 1.2] / 2.7 = 1070). In other words, in the graph of Figure 3(a), the load-bearing capacity standard "1" corresponds to "1070 MPa" under the above conditions. Therefore, to satisfy a load-bearing capacity of 1070 MPa or more, the offset distance S must be 30 mm or less.

[0028] The cold-forming reinforcing member can also be defined by the interval G between the adjacent welded portions 3. As an example, the position of the first welded portion 3a can also be defined by the interval G between the adjacent second welded portion 3b.

[0029] Specifically, the center point Ca of the first welded portion 3a must be spaced apart from the center point Cb of the second welded portion 3b by a distance G in the range of 12 mm to 30 mm. This is because the center point Ca of the first welded portion 3a is located at a position where it would be in contact with the heat-affected zone 4 of the adjacent second welded portion 3b, or at least at a position farther away from the second welded portion 3b than the position in this case.

[0030] This solves the problem of the solidification of the molten nugget for forming the first weld 3a being delayed by the heat-affected zone 4 of the second weld 3b, thereby solving the problem of reduced bonding strength of the cold-forming reinforcing member, and ensuring that the load-bearing capacity of the cold-forming reinforcing member meets the standard value, as can be seen from the graph shown in Figure 3(b).

[0031] Here, the minimum value of the gap G between the welds 3, 12 mm, is a value that can prevent fracture of the first weld 3a even in a cooling environment affected by the heat-affected zone 4 of the second weld 3b. That is, if the gap G between the welds 3 is smaller than 12 mm, more welds 3 can be formed, which may reduce the probability of fracture. However, in reality, the first weld 3a suffers from a greater problem of reduced bonding strength as the cooling delay caused by the heat-affected zone 4 of the second weld 3b increases. As a result, the cold-forming reinforcing member cannot ensure the load-bearing capacity corresponding to the standard value.

[0032] As an example, if the diameter of the welding head is 8 mm, the diameter WD of the weld 3 formed at this time will be 8 mm. The heat-affected zone 4 will have the same center point C as the center point C of the weld 3 and will form a donut-shaped region with a diameter ZD of 24 mm. In this case, the minimum distance G that satisfies the standard value is 12 mm when the distance G between the center points C of the welds 3.

[0033] Furthermore, the maximum distance G between the welds 3, 30 mm, is the maximum value required to satisfy the load-bearing capacity standard. As an example, consider the case where the blank member 1 has a tensile strength of 1200 MPa, a thickness t1 of 1.5 mm, and a reinforcing patch member 2 has a tensile strength of 900 MPa and a thickness t2 of 1.2 mm. The cold-formed reinforcing member formed by joining the blank member 1 and the reinforcing patch member 2 with the welds 3 has a thickness of 2.7 mm and a tensile strength of 1070 MPa ([1200 × 1.5 + 900 × 1.2] / 2.7 = 1070). In other words, in the graph of Figure 3(b), the load-bearing capacity standard "1" is "1070 MPa" under the above conditions. Therefore, to satisfy a load-bearing capacity of "1070 MPa" or higher, the distance G between the welds 3 must be 30 mm or less.

[0034] These conditions may be satisfied for all of the welds 3 forming the cold-forming reinforcing member, or, depending on the shape of the part to be manufactured, for only some of the welds 3. For example, the conditions may be adjusted so that 60% or more of the total number of welds 3 forming the cold-forming reinforcing member satisfy the above conditions.

[0035] The blank member 1 and the reinforcing patch member 2 have different required tensile strengths, which are standard values ​​required for parts manufactured using the cold-forming reinforcing member, and therefore their materials and tensile strengths can be limited to ensure this. That is, the blank member 1 or the reinforcing patch member 2 may be provided as one of a steel plate, an aluminum plate, a magnesium plate, and a titanium plate. The blank member 1 and the reinforcing patch member 2 may be provided as materials having a tensile strength of 500 MPa to 2500 MPa.

[0036] Here, the welded portion 3 may be formed by spot welding using a welding head. That is, the cold-forming reinforcing member of the embodiment is manufactured by spot welding, which is applied when manufacturing a conventional PWB reinforcing member.

[0037] The welds 3 of the cold-forming reinforcing member according to one embodiment may be arranged in a plurality along the shape of the end E of the reinforcing patch member 2 to form an outer row OL. The reason for limiting the arrangement positions of the welds 3 to the shape of the end E of the reinforcing patch member 2 is to ensure that the welds 3 uniformly share external forces, such as impact forces, applied to the reinforcing patch member 2.

[0038] Furthermore, the welds 3 of the cold-forming reinforcing member according to one embodiment may be arranged linearly in a plurality of rows inside the outer row OL to form an inner row IL. By forming the welds 3 in the inner row IL in this manner, the cold-forming reinforcing member can supplement its load transfer capability in addition to the tensile strength ensured by forming the welds 3 in the outer row OL. There may be a plurality of inner rows IL, which can further enhance the complementary effect of the load transfer capability.

[0039] Fig. 4 is a perspective view showing a part manufactured using the cold-forming reinforcing member of the embodiment. Here, Fig. 4(a) shows an embodiment in which a reinforcing patch member 2 is arranged only on the top surface of the part. Fig. 4(b) shows an embodiment in which the reinforcing patch member 2 is arranged up to the side surface of the part. Fig. 5 is a side cross-sectional view showing a bending portion 5 of a part manufactured using the cold-forming reinforcing member of the embodiment.

[0040] Referring to the drawings, a part according to one embodiment can be manufactured by forming the cold-forming reinforcing member at room temperature. That is, by using the cold-forming reinforcing member, damage to the welded portion 3 can be prevented and the required load-bearing capacity can be ensured even when the part is produced by a cold-forming process at room temperature.

[0041] Here, the cold forming process is different from a hot forming process in which a workpiece is heated and formed, and refers to a process in which a workpiece is formed at room temperature without being heated, such as by cold rolling to make it thinner (cold rolling), bending (cold bending), forging (cold forging, cold heading, cold press), or cold extrusion. Generally, the cold forming process refers to a cold press process in which a workpiece is formed into a product shape by being pressed down at room temperature.

[0042] Furthermore, the part according to one embodiment may be manufactured by forming at least one bending portion 5 in the cold-forming reinforcing member. That is, the part is formed by cold forming, such as bending or pressing, which forms the bending portion 5.

[0043] Conventional PWB reinforcing members have a problem in that when bending portions are processed by cold working, the welded portions are often damaged. In contrast, the part according to one embodiment is formed to include the bent portions 5 and is formed using the above-described cold-forming reinforcing member, so that damage to the welded portions 3 can be prevented.

[0044] According to one embodiment, the bent portion 5 of the part may be formed with a radius of curvature R that is 2 to 10 times larger than the sum of the thickness t1 of the blank member 1 and the thickness t2 of the reinforcing patch member 2. If the radius of curvature R of the bent portion 5 is smaller than the lower limit, damage may occur to the welded portion 3 disposed adjacent to the bent portion 5. If the radius of curvature R of the bent portion 5 is larger than the upper limit, the degree of freedom in part molding may be significantly limited.

[0045] Here, specific examples of parts manufactured using the above-mentioned cold-forming reinforcing member may include collision members such as side members or center pillars of an automobile body, floor flange members in the underbody of the vehicle, floor tunnels, etc.

[0046] The embodiment relates to a reinforcing member for cold forming and a part manufactured using the same, and by improving the Patch Worked Blank (PWB) technology among tailoring technologies, it is possible to form parts by a cold process performed at room temperature while preventing damage to the welded part 3.

[0047] The cold-forming reinforcing member and a part manufactured using the same according to one embodiment can be cold-formed without the need for a large space for heating equipment, high initial capital investment costs, and high operating costs required for a hot forming process, thereby reducing equipment costs and operating costs.

[0048] The reinforcing member for cold forming according to one embodiment and a part manufactured using the same can reduce the constraints imposed by the limited range of the radius of curvature at the bending portion 5 during cold forming and the limited range of the thickness t2 of the blank material and the reinforcing patch member 2, thereby increasing the degree of freedom in part design. As an example, the reinforcing member for cold forming according to the embodiment and a part manufactured using the same can make it possible to manufacture a bending collision member in an automotive structural part using a cold forming process while still satisfying the performance required for the bending collision member.

[0049] That is, automotive structural parts are developed for various purposes, such as high-strength shaped parts, high-rigidity parts, compression collision parts, and bending collision parts. Here, bending collision parts must minimize internal penetration to protect passengers and must not break. In this regard, the cold-forming reinforcing member according to the embodiment and parts manufactured using the same can be formed using a cold process at room temperature, while also meeting the performance requirements of bending collision parts.

[0050] Taking a center pillar as an example, the upper portion of the center pillar must be prevented from deforming to protect the upper body of a passenger. To this end, the upper portion of the center pillar requires relatively higher tensile strength than surrounding parts. In this regard, the cold-forming reinforcing member according to the embodiment ensures such tensile strength while allowing the center pillar to be manufactured in a cold state at room temperature, thereby reducing production costs compared to hot forming processes.

[0051] That is, the hot forming process is applied to the forming of conventional reinforced members because it increases the overall ductility, reduces the load on the welded portion 3, and eliminates the shear deformation during phase transformation, reducing the risk of fracture at the welded portion 3. However, the cold forming process does not have the effects of the hot forming process described above, and therefore could not be applied to the forming of conventional reinforced members. In contrast, the reinforced member for cold forming of the embodiment is able to satisfy the required performance even through the cold forming process.

Claims

1. a blank member; a reinforcing patch member provided to cover at least a portion of the blank member and connected to the blank member by a plurality of welds; In the blank member, a heat-affected zone formed around the welded portion is entirely located within a region corresponding to the reinforcing patch member, A heat-affected zone formed around a first welded portion among the welded portions is formed in contact with a center point of a second welded portion adjacent to the first welded portion or is formed apart from the center point of the second welded portion; The heat-affected zone is a portion where the metal structure and mechanical properties change due to the heat during welding, but the portion is not melted. A cold-forming reinforcing member, wherein the distance between the first welded portion and the second welded portion is formed in the range of 12 mm to 30 mm.

2. 2. The cold-forming reinforcing member according to claim 1, wherein the center point of the weld is formed at a position spaced apart from the edge of the reinforcing patch member by a distance in the range of 12 mm to 30 mm.

3. The cold-forming reinforcing member according to claim 1 , wherein the welded portion is formed by spot welding with a welding head.

4. 2. The cold-forming reinforcing member of claim 1, wherein the welds are arranged in a plurality along the edge of the reinforcement patch member to form an outer row.

5. The reinforcing member for cold forming according to claim 4 , wherein a plurality of the welds are arranged linearly inside the outer row to form an inner row.

6. The cold-forming reinforcing member according to claim 1 , wherein the blank member or the reinforcing patch member is provided as one of a steel plate, an aluminum plate, a magnesium plate, and a titanium plate.

7. The cold-forming reinforcing member according to claim 1, wherein the blank member and the reinforcing patch member are provided as materials having a tensile strength of 500 MPa to 2500 MPa.

8. A part manufactured by forming the cold-forming reinforcing member according to any one of claims 1 to 7 at room temperature.

9. 9. The component of claim 8, wherein the component is made by forming at least one bend in the cold-forming reinforcing member.

10. 10. The component according to claim 9, wherein the bent portion is formed with a radius of curvature that is 2 to 10 times greater than the sum of the thickness of the blank member and the thickness of the reinforcing patch member.

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