Press forming blank, press-formed component, and method of producing press-formed component

Abstract

The present invention pertains to: a press forming blank (integrated blank) which is obtained by partially overlapping and integrating a plurality of partial blanks, and which is for a component in which two members having at least an upright wall part and a top plate part are connected so as to intersect; a press-formed component obtained by press-forming the integrated blank; and a method of producing the press-formed component.　As an example of an embodiment, provided is an integrated blank (press forming blank) in which: a first partial blank corresponding to a first member and a second partial blank corresponding to a second member are partially overlapped; at an overlapping part, a protrusion that is a portion of the first partial blank corresponding to a top plate part of the second member and a portion of the second partial blank corresponding to the top plate part are bonded; and a notch part is provided to a portion of the first partial blank corresponding to the upright wall part of the second member. Also provided are: a press-formed component obtained by press-forming the integrated blank; and a method of producing a press-formed component using the integrated blank.

Description

Press-molding blank, press-molded part, and method for manufacturing press-molded part

[0001] The present invention relates to a blank for press molding using a tailored blank, a press-molded part, and a method for manufacturing a press-molded part.

[0002] There is a demand for reducing life cycle GHG (total greenhouse gas emissions over the entire life cycle), particularly in automobiles. With the aim of improving the efficiency of production lines by reducing the number of parts and omitting processes, integration technologies that press-form multiple connected parts or modules into a single part (integrated part) in one go have been attracting attention. Therefore, with the introduction of optimized design, there is an increasing demand for parts to be manufactured by press-forming so-called tailored welded blanks (TWBs), which are press-forming blanks formed by combining and integrating different types of steel sheets within a part. Various TWB press-forming technologies have been proposed in the past (for example, see Patent Document 1).

[0003] A press-molding blank (integrated blank) integrated by TWB is usually manufactured by butt-welding (line-welding) individual blanks (partial blanks) made of steel sheets of different thicknesses and types. As integrated blanks become larger, methods have been proposed for manufacturing an integrated blank by partially overlapping two partial blanks and spot welding the overlapping portions (Patent Documents 2 and 3). With the increasing size of parts and modules and the accompanying trend toward more efficient and cost-effective part manufacturing, part manufacturing by batch press-molding of integrated blanks is attracting increasing attention.

[0004] International Publication No. 2020 / 059804 International Publication No. 2020 / 002335 International Publication No. 2022 / 097058

[0005] When an integrated blank obtained by overlapping and joining two partial blanks (for example, by spot welding or lap welding) is press-formed, fractures such as cracks may be observed in the overlapping portion of the partial blanks. If a fracture such as a crack occurs in a part, the part is discarded due to quality issues and cannot be distributed. In other words, fractures in press-formed products lead to reduced productivity.

[0006] In particular, when a part formed by press-forming a TWB, in which a first member extending in a first direction is connected to a second member extending in a second direction intersecting the first direction, cracks may occur in corners where the blank is bent at the connection between the first and second members. In particular, in parts where both the first and second members have hat-, U-, or L-shaped cross sections and have a top plate portion, a standing wall portion, and a flange portion, cracks or wrinkles (hereinafter, cracks and wrinkles are collectively referred to as cracks) may occur in the bent portion of the blank at the connection between the first and second members (hereinafter, corners). For example, corners include the bent portion extending from the standing wall portion of the first member to the standing wall portion of the second member, particularly near the intersection between the top plate portion and the standing wall portion of the second member and the standing wall portion of the first member, and near the intersection between the standing wall portion and the flange portion of the first member and the standing wall portion and the flange portion of the second member.

[0007] In view of the above problems, the present invention provides a blank for press molding of a part in which two members having at least a vertical wall portion and a top plate portion are connected so as to intersect, and aims to suppress cracks, particularly at the corners of the connection between the members, when press molding an integrated blank formed by partially overlapping a plurality of partial blanks.

[0008] The present inventors have made extensive development efforts to achieve the above object and have obtained the following findings.

[0009] (a) When manufacturing a part in which a first member extending in a first direction is connected to a second member extending in a second direction intersecting the first direction, and both the first member and the second member have at least a top plate portion and a vertical wall portion, an investigation was conducted into the condition of cracks occurring at the connection between the two members when an integrated blank formed by overlapping and joining a partial blank for the first member and a partial blank for the second member is press-formed.

[0010] As a result, it was confirmed that cracks had occurred in the corners of the connection between the two components, in the areas corresponding to the vertical wall and flange portions of both components. When the partial blanks of the two components were lap-welded, spot welding was performed across the entire overlapping area, which is thought to have restricted the material flow in the vertical wall and flange portions of both components, causing large tensile strain in the material and resulting in the cracks. In other words, one possible cause is that the vertical wall and flange portions of the first and second components are bent and stretched in different directions during press forming, resulting in complex material flow behavior.

[0011] On the other hand, it was also confirmed that no cracks had occurred in the spot welds in the area corresponding to the top plate. This is thought to be because the top plate has little material flow during press forming, making it less susceptible to distortion.

[0012] (b) Based on the results of this investigation, we realized that if we joined the two partial blanks only in the area corresponding to the top plate, where there is little material flow, and did not join the two partial blanks in the areas corresponding to the vertical wall and flange, the two partial blanks would be able to deform freely and cracks would be avoided, and we proceeded with development.

[0013] (c) Furthermore, we have found that in the portion corresponding to the vertical wall or flange of the joint between the first and second members, which exhibits complex material flow behavior, cracks due to this complex material flow behavior can be suppressed by cutting out the portion of one of the partial blanks where the complex material flow occurs and forming a notch in advance. In particular, in the case of a part where the second member is butt-jointed to the first member, we have found that it is effective to form a notch in the portion corresponding to the vertical wall of the first member, because the vertical wall on the first member side undergoes complex deformation.

[0014] The present invention was made based on the above findings, and its gist is as follows.

[0015] [1] A press-forming blank for a part having a first member extending in a first direction and a second member extending in a second direction intersecting the first direction, each having a top plate portion and at least one standing wall portion connected to the top plate portion, and a portion where the second member is connected to the first member so as to abut against it, wherein the connected portion of the first member and the second member of the part is formed by partially overlapping a first partial blank corresponding to the first member and a second partial blank corresponding to the second member, and at the overlap portion where the partially overlapped portion is formed, a protruding portion of the first partial blank corresponding to the top plate portion of the second member is joined to at least a portion of a portion of the second partial blank corresponding to the top plate portion of the second member, and a notch portion where the first partial blank is not provided is provided between the protruding portion and the portion of the standing wall portion of the second member in the first partial blank. The part is typically the press-forming blank described in [1], in which the second member is connected to the standing wall portion of the first member so as to abut against it. [2] The blank for press molding according to [1], wherein the first partial blank has a protruding tongue portion in at least one of the following at the overlapping portion: (a) the protruding portion; (b) a portion corresponding to the standing wall portion of the first member. [3] The blank for press molding according to [1], wherein the first member and the second member further have flange portions connected to the standing wall portions. [4] The blank for press molding according to [3], wherein the first partial blank has a protruding tongue portion in at least one of the following at the overlapping portion: (a) the protruding portion; (b) a portion corresponding to the standing wall portion of the first member; (c) a portion corresponding to the flange portion of the first member. [5] The blank for press molding according to any one of [1] to [4], wherein the cutout portion includes a portion corresponding to a ridge line that is a boundary between a top plate portion and a standing wall portion of the second member. That is, the first partial blank is a press-molding blank according to any one of [1] to [4] above, which does not include a portion corresponding to the ridge line of the second member.Preferably, the tip of the notch (the portion where the end of the protruding portion in the first partial blank intersects with the end of the portion corresponding to the standing wall portion of the second member) is not located in the portion corresponding to the ridge line of the second member. [6] The press-molding blank according to any one of [1] to [5] above, wherein in the first partial blank, the boundary line between the protruding portion and the portion corresponding to the standing wall of the first member is separated from the ridge line that defines the boundary between the top plate portion and the standing wall portion of the first member. That is, the ridge line that defines the boundary between the top plate portion and the standing wall portion of the first member exists consistently without being interrupted. [7] The press-molding blank according to any one of [1] to [6] above, wherein the part is an automobile part. [8] A part (press-molded part) including a first member extending in a first direction and a second member extending in a second direction intersecting the first direction, each having a top plate portion and at least one standing wall portion connected to the top plate portion, the second member connected to the first member so as to abut against the first member, wherein the connected portion of the part where the first member and the second member are connected is formed by an integrated blank formed by partially overlapping a first partial blank corresponding to the first member and a second partial blank corresponding to the second member, and at the overlap portion where the first and second members are connected, at least a protruding portion of the first partial blank corresponding to the top plate portion of the second member is joined to a portion of the second partial blank corresponding to the top plate portion of the second member, and further comprising a notch where the first partial blank is not provided between the protruding portion of the first partial blank and a portion corresponding to the standing wall portion of the second member. The part is typically a part (press-molded part) in which the second member is connected to the standing wall portion of the first member so as to abut against the standing wall portion of the first member. [9] The part (press-molded part) according to [8], wherein the first partial blank has a protruding tongue portion in at least one of the following parts at the overlapping portion: (a) the protrusion, (b) a portion corresponding to the standing wall portion of the first member.

[10] The part (press-molded part) according to [8], wherein the first member and the second member further have flange portions connected to the standing wall portions.

[11] The part (press-molded part) according to

[10] , wherein the first partial blank has a protruding tongue portion in at least one of the following parts at the overlapping portion: (a) the protrusion, (b) a portion corresponding to the vertical wall portion of the first member, or (c) a portion corresponding to the flange portion of the first member.

[12] The part (press-molded part) according to any one of [8] to

[11] , wherein the cutout portion includes a portion corresponding to a ridge line that forms a boundary between the top plate portion and the vertical wall portion of the second member. That is, the part (press-molded part) according to any one of [8] to

[11] , wherein the first partial blank does not include a portion corresponding to the ridge line of the second member. Preferably, the tip portion of the cutout portion (the portion where the end of the protrusion in the first partial blank intersects with the end of the portion corresponding to the vertical wall portion of the second member) is not located in the portion corresponding to the ridge line of the second member.

[13] The part (press-molded part) according to any one of [8] to

[12] , wherein in the first partial blank, a boundary line between the protrusion and a portion corresponding to the standing wall of the first member is separated from a ridge line defining a boundary between the top plate portion and the standing wall portion of the first member. That is, the ridge line defining the boundary between the top plate portion and the standing wall portion of the first member is present consistently without being interrupted.

[14] The part (press-molded part) according to any one of [8] to

[13] , wherein the part is an automotive part.

[15] A method for manufacturing a part in which a first member extending in a first direction and a second member extending in a second direction intersecting the first direction each have a top plate portion and at least one standing wall portion connected to the top plate portion, and the second member is connected to the first member so as to abut against the first member, comprising: preparing a first partial blank corresponding to the first member and a second partial blank corresponding to the second member; forming a protruding portion in the first partial blank that is a portion of the first partial blank that corresponds to the top plate portion of the second member; providing a cutout portion that is not present in the first partial blank between the protruding portion of the first partial blank and a portion of the standing wall portion of the second member; partially overlapping the first blank and the second blank; forming an integrated blank by joining at least the protruding portion of the first partial blank to at least a part of the portion of the second partial blank that corresponds to the top plate portion of the second member at an overlapping portion that is the partially overlapping portion; press-forming the integrated blank, and then further joining the overlapping portion to obtain the part (press-molded part). The part is typically a part (press-molded part) in which the second member is connected to the upright wall portion of the first member so as to abut against it.

[16] The method for manufacturing the part (press-molded part) described in

[15] , in which the first partial blank has a protruding tongue portion in at least one of (a) the protrusion, and (b) a portion corresponding to the upright wall portion of the first member, at the overlapping portion, and the tongue portion of the first partial blank and the upright wall portion of the second member are joined after the press molding.

[17] The method for manufacturing the part (press-molded part) described in

[15] , in which the first member and the second member further have flange portions connected to the upright wall portions.

[18] A method for manufacturing a part (press-molded part) according to

[17] , wherein the first partial blank has a protruding tongue portion in at least one of the overlapping portions: (a) the protrusion; (b) a portion corresponding to the standing wall portion of the first member; and (c) a portion corresponding to the flange portion of the first member; and after the press molding, the tongue portion of the first partial blank and the standing wall portion of the second member are joined.

[19] The method for manufacturing a part (press-molded part) according to any one of

[15] to

[18] , wherein the cutout portion includes a portion corresponding to a ridgeline that defines a boundary between the top plate portion and the standing wall portion of the second member. That is, the method for manufacturing a part (press-molded part) according to any one of

[15] to

[18] , wherein the first partial blank does not include a portion corresponding to the ridgeline of the second member. Preferably, the tip of the cutout portion (the portion where the end of the protrusion in the first partial blank intersects with the end of the portion corresponding to the standing wall portion of the second member) is not located on the portion corresponding to the ridgeline of the second member.

[20] The method for manufacturing a part (press-molded part) according to any one of

[15] to

[19] , wherein, in the first partial blank, the boundary line between the protrusion and the portion corresponding to the standing wall of the first member is separated from the ridgeline that defines a boundary between the top plate portion and the standing wall portion of the first member. That is, the ridgeline that defines the boundary between the top plate portion and the standing wall portion of the first member is continuous and not interrupted.

[21] The method for manufacturing a part (press-molded part) according to any one of

[15] to

[20] , wherein the part is an automotive part.

[0016] According to the present invention, when an integrated blank formed by partially overlapping a plurality of partial blanks is press-formed into a blank for press-forming a part in which two members having at least a vertical wall portion and a top plate portion are connected to intersect, cracks, particularly cracks at the corners of the connecting portion between the two members, can be suppressed. This makes it possible to efficiently and productively manufacture even large parts with complex shapes.

[0017] Since Figures 5 and 6 span multiple pages, Figure 5 is divided into Figures 5-1 and 5-2, collectively referred to as Figure 5, and Figure 6 is divided into Figures 6-1 and 6-2, collectively referred to as Figure 6. Figure 1 is a schematic diagram showing an example of an L-shaped part with an L-shaped cross section according to the present invention. Figure 1(a) is a schematic diagram showing the case where there is no step between the first and second members, and Figure 1(b) is a schematic diagram showing the case where there is a step. Figure 2 is a schematic diagram showing an example of an L-shaped part with a flanged L-shaped cross section according to the present invention. Figure 2(a) is a schematic diagram showing the case where there is no step between the first and second members, and Figure 2(b) is a schematic diagram showing the case where there is a step. Figure 3 is a schematic diagram showing an example of a T-shaped part with a C-shaped cross section according to the present invention. Figure 3(a) is a schematic diagram showing the case where there is no step between the first and second members, and Figure 3(b) is a schematic diagram showing the case where there is a step. Figure 4 is a schematic diagram showing an example of a T-shaped part with a hat-shaped cross section according to the present invention. FIG. 4(a) is a schematic diagram showing a case where there is no step between the first and second members, and FIG. 4(b) is a schematic diagram showing a case where there is a step. FIGS. 5(a) and 5(b) are schematic diagrams of integrated blanks according to the present invention corresponding to the L-shaped parts with L-shaped cross sections shown in FIGS. 1(a) and 1(b), respectively. FIGS. 6(a) and 6(b) are schematic diagrams of integrated blanks according to the present invention corresponding to the flanged L-shaped parts with L-shaped cross sections shown in FIGS. 2(a) and 2(b), respectively. FIG. 7 is a schematic diagram for explaining an integrated blank with a tongue portion, showing the overlapping portion of the integrated blank when the tongue portion is arranged on the flanged L-shaped part with L-shaped cross section shown in FIG. 6(b). FIG. 8 is a diagram showing an example where the intersection angle of the L-shaped parts with L-shaped cross sections is acute, with FIG. 8(a) being a schematic diagram of the external appearance and FIG. 8(b) being a schematic diagram of the integrated blank. FIG. 9 is a schematic diagram showing an example of a T-shaped part with a tubular cross section, which is formed by combining T-shaped parts with C-shaped cross sections as shown in FIG. 3(a). FIG. 10 is a schematic diagram showing an example of a T-shaped part with a tubular cross section, which is formed by combining T-shaped parts with hat-shaped cross sections as shown in FIG. 4(a). FIG. 11(a) is a schematic diagram of an automotive part that served as the basis for the T-shaped part used in the examples, and FIG. 11(b) is a schematic diagram of that T-shaped part. FIG. 11(c) is a schematic diagram of a press-molded part according to the present invention manufactured in the examples. FIG. 12 is a schematic diagram of an integrated blank corresponding to the press-molded part in FIG. 11(c). Note that when (a), (b), etc. are included in a drawing, as in FIGS. 1(a) and (b), these will be collectively referred to as FIG. 1, etc.

[0018] An embodiment of the present invention (hereinafter simply referred to as the present invention) will be described with reference to the drawings.

[0019] 1(a) and 1(b) (hereinafter, FIGS. 1(a) and 1(b) will be collectively referred to as FIG. 1. Similarly, in FIGS. 2, 3, and 4, (a) and (b) will be collectively referred to as FIGS. 2, 3, and 4.) are schematic diagrams of an L-shaped component (hereinafter, simply referred to as an L-shaped component based on the shape of the component when viewed from above) in which two L-shaped cross-section members each having a top plate portion and a vertical wall portion connected thereto are intersectingly connected. FIG. 1(a) shows a case where there is no step between the top plate portions of the first and second components, while FIG. 1(b) shows a case where there is a step between the top plate portions of the first and second components. As can be seen from FIG. 1, the top plate portions and the vertical wall portions are connected in a direction perpendicular to the longitudinal direction (axial direction) of the components. The L-shaped component 5 shown in FIG. 1 is an integrated component composed of a first component 1 and a second component 2. The first member 1 extends in a first direction 3, and the second member 2 extends in a second direction 4 intersecting the first direction 3. The second member 2 is connected to the first member 1 so as to abut against it. Typically, the second member 2 is connected to the first member 1 so as to abut against a vertical wall portion 12. Both the first member 1 and the second member 2 have an L-shaped cross section, and each has a top plate portion 11, 21 and a vertical wall portion 12, 22 connected to the top plate portion. The L-shaped part 6 shown in FIG. 2 is the L-shaped part 5 of FIG. 1, except that the first member 1 and the second member 2 further have flange portions 13, 23 connected to the vertical wall portions 12, 22 on the opposite side from the top plate portions 11, 21. FIG. 2(a) schematically shows a case where there is no step between the top plate portions of the first member and the second member, and FIG. 2(b) shows a case where there is a step between the top plate portions of the first member and the second member. 1(a) and 1(b) are schematic diagrams of parts press-formed from integrated blanks such as those shown in FIGS. 5(a) and 5(b), respectively, and FIGS. 2(a) and 2(b) are schematic diagrams of parts press-formed from integrated blanks such as those shown in FIGS. 6(a) and 6(b), respectively.

[0020] The L-shaped components 5 and 6 shown in Figures 1 and 2 can be used as a base to create a variety of component shapes. For example, as shown in Figure 3, connecting two L-shaped components 5 back to back creates a T-shaped component 7. Figure 3 also shows a schematic diagram of a case where there is no step between the top plates of the first and second components (Figure 3(a)), and a case where there is a step between the top plates of the first and second components (Figure 3(b)). The first component 1 of the T-shaped component 7 shown in Figure 3 also has a vertical wall on the side opposite the second component 2. However, this vertical wall can be formed by simple bending press during press forming, so conventional press forming methods can be applied and there are no particular technical issues. Therefore, the T-shaped component 7 shown in Figure 3 can be combined with the L-shaped component 5 shown in Figure 1 to create a T-shaped component 7 with a C-shaped cross section. Similarly, connecting two L-shaped components 6 with bottom flanges shown in Figure 2 back to back creates a T-shaped component 8 with a hat-shaped cross section as shown in Figure 4. 4(a) also shows a case where there is no step between the top plate portions of the first and second members, and FIG. 4(b) shows a case where there is a step between the top plate portions of the first and second members. Note that FIG. 4(b) also shows a schematic diagram of a part press-formed from an integrated blank such as that shown in FIG.

[0021] Although not shown, a cross-shaped part with a C-shaped cross section can be formed by connecting four L-shaped parts of Fig. 1 back to back at both the first and second members. Similarly, although not shown, a cross-shaped part with a hat-shaped cross section can be formed by connecting four L-shaped parts of Fig. 2 back to back.

[0022] When these integrated parts are manufactured by press-forming an integrated blank, the material flow behavior becomes complex at the corners of the connection between the first and second parts, particularly at the vertical walls and flanges of both parts, resulting in large tensile strain and cracking. Therefore, because the problem of cracking at corners is the same for cross-shaped, T-shaped, and L-shaped parts, the countermeasures discussed for the L-shaped part shown in Figures 1 and 2 can be applied to parts of various shapes. For these reasons, the present invention will be explained below using the L-shaped part shown in Figures 1 and 2 (hereinafter referred to as the "part").

[0023] An integrated blank was prepared for press-forming the part. The integrated blank was a tailored blank (TWB) constructed by partially overlapping a first partial blank corresponding to the first component and a second partial blank corresponding to the second component. The first partial blank is the blank whose main portion will become the first component after press-forming. Therefore, it is referred to as the first partial blank corresponding to the first component. Similarly, the second partial blank is the blank whose main portion will become the second component after press-forming, so it is referred to as the second partial blank corresponding to the second component. During overlapping, the second partial blank was placed over the first partial blank so that the mating components, i.e., the second component, butted against the connection portion of the first component. For example, Figures 5 and 6 correspond to Figures 1 and 2, respectively. Figure 5 shows an example of an L-shaped cross section, and Figure 6 shows a schematic diagram of an integrated blank for an L-shaped cross section with a flange. These integrated blanks consist of a first partial blank 110 and a second partial blank 120. The first and second partial blanks 110 and 120 are arranged so that the top plate portion 121 of the second partial blank 120, which corresponds to the top plate portion of the second member, overlaps with the portion of the first partial blank that corresponds to the top plate portion of the second member. The two-dot chain lines in Figures 5 to 7 indicate the lines that correspond to the ridges of the part after press forming. For example, this is the boundary line (ridge line 116) between the portion 111 that corresponds to the top plate portion of the first member and the portion 112 that corresponds to the standing wall portion in the first partial blank, and similarly, the boundary line (ridge line 126) between the portion 121 that corresponds to the top plate portion and the portion 122 that corresponds to the standing wall portion in the second partial blank. This is the same in the figures showing other blanks.

[0024] Here, the portion of the second partial blank corresponding to the top plate portion of the second member refers to the portion of the second partial blank that corresponds to the top plate portion of the second member after press forming. Similarly, the portion of the first partial blank corresponding to the top plate portion of the second member refers to the portion of the first partial blank that corresponds to the top plate portion of the second member after press forming. Similarly, the portion of the first partial blank that corresponds to the vertical wall portion of the second member after press forming is referred to as the "portion of the first partial blank corresponding to the vertical wall portion of the second member." Note that the first partial blank and the second partial blank themselves may each be blanks made from a single steel plate, or may be tailored blanks (TWBs) in which the end faces of multiple steel plates are butt-joined.

[0025] To integrate the two partial blanks, the overlapping portion (the overlapping portion 130) of the two blanks is joined. However, if the two partial blanks 110, 120 are joined over the entire overlapping portion 130, material flow becomes complex at the vertical wall, flange, and corner portions of the part during press forming, causing large tensile strain in the material and making it more susceptible to cracking. In particular, material flow becomes complex at the intersection of the portion of the first partial blank corresponding to the top plate portion of the second component, the portion corresponding to the vertical wall portion of the second component, and the portion corresponding to the vertical wall portion of the first component, making it more susceptible to cracking. On the other hand, in the first partial blank 110, material flow is less at the portion corresponding to the top plate portion of the second component, making it less susceptible to cracking. Therefore, it is preferable to join only the portion of the overlapping portion 130 corresponding to the top plate portion of the second component to form an integrated blank.

[0026] By joining at least a portion of the overlapping portion 130 that corresponds to the top plate portion of the second member in this manner, both partial blanks can exhibit deformation behavior as if they were separate blanks during press forming. In other words, both partial blanks can be freely deformed, thereby preventing cracks.

[0027] The method for joining the two blanks is not particularly limited. For example, joining by welding such as spot welding, lap welding, and lap fillet welding is preferred. In particular, spot welding is preferred from the viewpoint of workability. The type of welding is not particularly limited. Resistance welding, laser welding, and the like may be selected as appropriate. For example, spot welding (resistance welding, laser spot welding) is preferred from the viewpoints of applicability to complex shapes, workability, efficiency, and cost.

[0028] <Protrusion> Furthermore, it has been found that it is effective to form the protrusion 133 by cutting only the portion of the overlapping portion 130 of the first partial blank 110 that corresponds to the top plate portion of the second member from the other portions. This reduces or eliminates material flow from the top plate portion of the first partial blank to other portions (e.g., portions that correspond to adjacent vertical wall portions). In other words, the protrusion 133 of the first partial blank 110 and at least a portion of the top plate portion 121 of the second partial blank 120 are joined to form an integrated blank. As a result, after press forming, the protrusion 133 overlaps and becomes integrated with the top plate portion of the second member.

[0029] The protrusion 133 of the first partial blank corresponds to the top plate portion of the second member after press forming. Therefore, the position of the protrusion 133 may be determined depending on how the second member 2 is butted against the first member 1. For example, the distance between the boundary line (the base end of the protrusion) between the protrusion 133 of the first partial blank and the portion corresponding to the vertical wall portion of the first member and the ridge line 116 of the first member (the ridge line that forms the boundary between the top plate portion and the vertical wall portion of the first member) is preferably 0 mm or more. Preferably, the boundary line (the base end of the protrusion) between the protrusion 133 of the first partial blank and the portion corresponding to the vertical wall portion of the first member and the ridge line 116 of the first member (the ridge line that forms the boundary between the top plate portion and the vertical wall portion of the first member) is preferably spaced apart. In other words, a step may be formed between the top plate portion of the first member and the top plate portion of the second member. The separation distance may be one or more times, two or more times, three or more times, or five or more times the thickness of the second partial blank 120. By separating the base end of the protrusion from the ridge line 116 of the first member, the ridge line 116 of the first member is present throughout, and therefore the resistance (anti-buckling force) of the first member to an external force acting in the first direction is strengthened.

[0030] The length of the protrusion (length in the second direction) is not particularly limited. From the viewpoint of joining the first and second partial blanks at the overlapping portion, it is desirable to secure a joining area. For example, when joining by spot welding, it is preferable to secure an area at least twice the diameter of the spot weld. From this viewpoint, the length of the protrusion may be, for example, 20 mm or more, preferably 30 mm or more, or 40 mm or more. On the other hand, if the protrusion is too long, the first partial blank will have an irregular shape to secure the protrusion, which will reduce material yield when cutting it from the raw material (steel plate). Therefore, it is preferable that the length of the protrusion be a length that corresponds to the edge line of the original plate (steel plate) of the first partial blank. For example, it is preferable that the length of the protrusion be equal to or less than the width of the standing wall portion 112 of the first member of the first partial blank 110 (the length of the standing wall portion in the second direction) or the combined width of the standing wall portion and the flange portion (the sum of the lengths of the standing wall portion and the flange portion in the second direction).

[0031] The portion of the overlapping portion 130 other than the protruding portion 133 becomes the portion of the first partial blank that overlaps with the portion 122 corresponding to the vertical wall portion of the second partial blank 120, or the portion of the first partial blank that overlaps with the portions 122, 123 corresponding to the vertical wall portion and flange portion of the second partial blank 120 (hereinafter, both cases will be referred to as the vertical wall overlapping portion 135). The method of separating the protruding portion 133 and the vertical wall overlapping portion 135 is not particularly limited. For example, a slit-shaped notch may be formed between the protruding portion 133 and the vertical wall overlapping portion 135. Alternatively, a portion of the portion of the first partial blank that corresponds to the vertical wall of the second member may be removed from the end of the protruding portion to form the notch. The notch will be described in detail below.

[0032] <Notch> Complex material flow occurs in the vertical wall and flange portions of the connection (especially corner portions) between the first and second components during press forming. Even if the overlapping portion of the first and second partial blanks is partially joined, this complex material flow generates large tensile strain, making cracks more likely to occur. Therefore, we have discovered that by pre-removing the portion where such complex material flow is likely to occur and forming a notch, it is possible to suppress cracks caused by this complex material flow. As schematically shown in Figures 5 and 6 , a portion of the overlapping portion 130 of the first partial blank that overlaps with the portion 122 corresponding to the vertical wall portion of the second partial blank 120 may be removed to form a notch 134. In other words, the notch 134 is a portion where the first partial blank is not present. This notch 134 separates the protrusion 133 of the first partial blank 110 from the portion corresponding to the vertical wall portion of the second component. (In Figures 5 and 6, the cutout portion 134 is the area surrounded by the thin dotted line.) Preferably, the cutout portion is formed by cutting out the entire portion of the first partial blank that corresponds to the vertical wall portion of the second member.

[0033] During press forming, material flow occurs in the bent portion. The more intersecting the bent portion, the more complex the material flow becomes. Therefore, it is preferable that the cutout portion 134 of the first partial blank be formed so as to include a portion corresponding to the ridgeline 126 of the second member (the ridgeline that forms the boundary between the top plate portion and the vertical wall portion). In other words, it is preferable that the first partial blank 110 not include a portion corresponding to the ridgeline 126 of the second member. This makes it possible to suppress material flow in the first partial blank 110 associated with bending the second member during press forming. More preferably, the tip portion of the cutout portion 134 (the portion where the end of the protruding portion 133 in the first partial blank intersects with the end of the vertical wall overlapping portion 135, or the portion that forms the end of the first partial blank that connects the end of the protruding portion and the end of the vertical wall overlapping portion 135) is not positioned in the portion corresponding to the ridgeline 126 of the second member. The tip portion of the notch 134 is the portion where the most complex material flow occurs in the first partial blank, so by ensuring that this does not overlap the ridge line 126, the complexity of the material flow can be alleviated.

[0034] In particular, if the area of ​​the vertical wall overlapping portion 135 of the first partial blank is large, defects such as cracks and wrinkles are more likely to occur. That is, if the area of ​​the vertical wall overlapping portion 135 of the first partial blank is large, even if the two partial blanks are free to deform, it approaches the phenomenon of forming with a single blank, and complex material flow is more likely to occur. Therefore, it is desirable not to make the vertical wall overlapping portion 135 of the first partial blank wider than necessary.

[0035] The area of ​​the vertical wall overlap portion 135 of the first partial blank is preferably 90% or less of the area of ​​the overlapping portion (i.e., the area of ​​the overlapping portion excluding the protruding portion) between the first partial blank (original first partial blank) before the cutout portion is removed, the portion of the second partial blank corresponding to the vertical wall portion of the second component (hereinafter referred to as the vertical wall portion of the second partial blank), and the portion of the second partial blank corresponding to the flange portion of the second component (hereinafter referred to as the flange portion of the second partial blank). Preferably, the area is 80% or less, 70% or less, 60% or less, 50% or less, or 40% or less. If the area of ​​the overlapping portion of the first partial blank is too narrow, it will be impossible to join the first partial blanks after press working, so it is preferable to leave a sufficient area to allow joining after press working. From this perspective, the area of ​​the vertical wall overlap portion 135 of the first partial blank should be 5% or more, 10% or more, or 20% or more of the area of ​​the overlapping portion between the vertical wall portion and flange portion of the original first partial blank and the second partial blank.

[0036] There are no particular limitations on the shape of the cutout portion 134. For example, it is conceivable to grasp the material flow behavior by a simulation such as FEM (Finite Element Method), identify a portion where the strength exceeds a reference value (for example, the shear fracture strength of the steel plate that is the material), and make that portion the cutout portion.

[0037] As an example, Fig. 5 shows an L-shaped cross section without a flange, and Fig. 6 shows an L-shaped cross section with a flange. In both Figs. 5 and 6, the cutout is made along the protrusion, and the edge of the cutout is arcuate in the upright wall overlapping portion 135 of the first partial blank that corresponds to the upright wall portion 122 of the second partial blank. In Fig. 6, the edge of the cutout is linear in the portion that corresponds to the flange portion 113 of the first partial blank. The shape of the cutout 134 may be changed depending on the upright wall portion 112 and flange portion 113 of the first partial blank.

[0038] <Tongue Portion> One or more tongue-shaped protrusions (tongue portions) protruding from the first partial blank may be provided in the area of ​​the notch portion 134 in the overlapping portion 130 of the first partial blank. That is, one or more protruding tongue portions may be provided on the first partial blank. Because the area of ​​the notch portion originally corresponds to the vertical wall portion of the second component, the tongue portions are formed to conform to the inner surface of the vertical wall portion of the second component after press forming. Therefore, by joining the tongue portions of the first partial blank and the vertical wall portion of the second partial blank after press forming, the rigidity and impact resistance of the integrated component can be improved. Additionally, although a secondary benefit, providing the tongue portions allows for effective use of the material removed at the notch portion. Furthermore, the tongue portions are bent during press forming, preventing misalignment of the second partial blank during forming.

[0039] The location of the tongue portion is not particularly limited as long as it is within the area of ​​the cutout portion 134 of the first partial blank. As an example, Figure 7 shows the overlapping portion of the first partial blank and the second partial blank when the tongue portion is arranged on the integrated blank of the flanged L-shaped cross-section part shown in Figure 6 (b). In the example of Figure 7, the first partial blank 110 has protruding tongue portions at three locations in the overlapping portion 130: (a) a tongue portion 136 provided on the protruding portion 133 of the first partial blank, (b) a tongue portion 137 provided on a portion corresponding to the standing wall portion 112 of the first partial blank, and (c) a tongue portion 138 provided on a portion corresponding to the flange portion 113 of the first partial blank. However, it is preferable to have a protruding tongue portion at at least one of these locations. In the case of a first member having an L-shaped cross section without a flange, although not shown, it is preferable that at least one of (a) the protruding portion of the first partial blank and (b) the portion corresponding to the vertical wall of the first partial blank at the overlapping portion of the first partial blank has a protruding tongue portion. Because these tongue portions are separated from each other, they are simply bent independently during press forming, so defects such as cracks do not occur.

[0040] The number of tongue portions is not particularly limited. In the example of Figure 7, tongue portions are provided in three locations, but it is not necessary to provide all of these tongue portions; at least one of them may be provided as needed. Of course, multiple tongue portions may be provided in each of (a) to (c). When multiple tongue portions are provided, it is desirable to arrange them so that they do not interfere with each other after press forming. This is because mutual interference can cause defects such as wrinkles during press forming.

[0041] The size of the tongue portion is not particularly limited. As described above, after press forming, the tongue portion of the first partial blank is formed to fit the inner surface of the vertical wall portion of the second component. Joining the vertical wall portion of the second partial blank and the tongue portion of the first partial blank after press forming increases the rigidity of the integrated part. Therefore, it is desirable for the tongue portion to have an area large enough to allow for joining. For example, when joining by spot welding, it is desirable for the length and width to be at least twice the spot weld diameter (the length of the tongue portion is the maximum length of the tongue portion in the direction protruding from the first partial blank (the length direction of the tongue portion), and the width of the tongue portion is the maximum length of the tongue portion in the direction perpendicular to the length direction of the tongue portion). The length and width of the tongue portion may be, for example, 10 mm or more, preferably 20 mm or more, or 30 mm or more. The upper limits of the length and width of the tongue portion are preferably determined appropriately based on the shape of the first partial blank before the notch is removed. This is because making the first partial blank into an irregular shape in order to secure the tongue portion not only reduces the material yield but also may lead to an increase in blank processing costs.

[0042] <Intersection Angle Between First and Second Members> The intersection angle between the first and second members, i.e., the intersection angle between the first and second directions, is not particularly limited. FIG. 8 shows a schematic diagram of an L-shaped part in which the intersection angle between the first and second members 1 and 2, i.e., the intersection angle between the first and second directions 3 and 4, is θ. FIG. 8(a) is an external view of the L-shaped part 5, and FIG. 8(b) is a schematic diagram of an integrated blank thereof. While FIG. 8 shows an acute angle (90° or less) for the intersection angle θ, it may also be an obtuse angle. The lower limit of the intersection angle θ is not particularly limited as long as it is greater than 0°, but it may be set appropriately depending on the processing accuracy of the press molding. Similarly, the upper limit of the intersection angle θ is not particularly limited as long as it is less than 180°. For example, when corresponding L-shaped parts are integrated back-to-back as shown in FIGS. 3 and 4, if the intersection angle on one side is an acute angle, the intersection angle of the member on the opposite side will also be an acute angle, and this is set appropriately depending on the processing accuracy of the press molding. Figure 8(a) corresponds to Figure 1(a), and Figure 8(b) corresponds to Figure 5(a) and shows an L-shaped part with an L-shaped cross section without a flange. For example, in the case of an L-shaped cross section with a flange, Figure 8(a) can be modified to correspond to Figure 2(a), and Figure 8(b) can be modified to correspond to Figure 6(a).

[0043] The above has described a press-forming blank for a part having a first member extending in a first direction and a second member extending in a second direction intersecting the first direction, each having a top plate portion and at least one standing wall portion connected to the top plate portion, and a portion where the second member is connected to the first member so as to abut against the first member. That is, the press-forming blank according to the present invention is a blank including a blank in which the first partial blank and the second partial blank for the connected portion are integrated. There may be one or more integrated blanks for the connected portion within the press-forming blank for the entire part, and their arrangement (position within the press-forming blank for the entire part) is not limited.

[0044] Furthermore, in the blank for press molding of the entire part, the joining method of the blanks other than the portion where the first member and the second member are connected is not particularly limited. A tailored blank (TWB) in which the end faces of partial blanks are joined together may be used.

[0045] <Press-Molded Part> A part (press-molded part) obtained by integrally press-molding an integrated blank composed of the first partial blank and the second partial blank described above is an integrated part. As described above, the L-shaped part with an L-shaped cross section shown in FIGS. 1 and 2 is the basic shape, and by combining these parts, the T-shaped part shown in FIGS. 3 and 4 is obtained. By further combining these parts, a cross-shaped part (not shown) can also be obtained. Similarly, a part with a shape combining an L, a T, and a cross, such as a lattice-like part, can be obtained by combining the L-shaped parts shown in FIGS. 1 and 2 to obtain an integrated blank, which can then be press-molded into an integrated part.

[0046] Furthermore, by stacking these integrated parts one on top of the other with one part turned upside down, a part with a tubular cross section can be obtained. For example, by combining and joining T-shaped parts 7 shown in Figure 3(a) one on top of the other, a T-shaped part with a hexagonal cross section as shown in Figure 9 can be obtained. Similarly, by combining and joining T-shaped parts 8 shown in Figure 4(a) one on top of the other, a T-shaped part with a hexagonal cross section and flanges as shown in Figure 10 can be obtained.

[0047] These parts can also be manufactured using the shaped blank according to the invention. That is, a component in which a first member extending in a first direction and a second member extending in a second direction intersecting the first direction each have a top plate portion and at least one standing wall portion connected to the top plate portion, and the second member is connected to the first member so as to abut against it, wherein the portion of the component where the first member and the second member are connected is constituted by an integrated blank formed by partially overlapping a first partial blank corresponding to the first member and a second partial blank corresponding to the second member, and at the overlapping portion which is the partially overlapped portion, at least a protruding portion which is a portion of the first partial blank which corresponds to the top plate portion of the second member and a portion of the second partial blank which corresponds to the top plate portion of the second member are joined, and further, a notch portion where the first partial blank is not provided is provided between the protruding portion of the first partial blank and the portion which corresponds to the standing wall portion of the second member, and as necessary, the first partial blank has, at the overlapping portion, (a) the protruding portion, (b) a portion which corresponds to the standing wall portion of the first member, and (c) a portion which corresponds to the flange portion of the first member. The part (press-molded part) has a protruding tongue portion on at least one of the above.

[0048] The part is typically a part (press-molded part) in which the second member is connected to the upright wall portion of the first member so as to abut against the second member.

[0049] The cutout portion is a part (press-molded part) that includes a portion corresponding to a ridge line that is a boundary between the top plate portion and the standing wall portion of the second member. That is, the first partial blank is a part (press-molded part) that does not include a portion corresponding to the ridge line of the second member. Preferably, the tip portion of the cutout portion (the portion where the end of the protrusion in the first partial blank intersects with the end of the portion corresponding to the standing wall portion of the second member) is not located in the portion corresponding to the ridge line of the second member.

[0050] Furthermore, in the first partial blank, the boundary line between the protrusion and the portion corresponding to the standing wall of the first member is separated from the ridge line defining the boundary between the top plate portion and the standing wall portion of the first member (press-molded part). That is, the ridge line defining the boundary between the top plate portion and the standing wall portion of the first member exists consistently without being interrupted.

[0051] In the conventional method, the first and second members are press-formed separately and then joined together to obtain the product, but it has been confirmed that extremely high efficiency in workability can be realized. In particular, in the case of a part that combines multiple L-shaped parts, what would have been done by press-forming individual members and welding them together can be obtained as an integrated part by integrated press-forming, so the effect is extremely significant.

[0052] Furthermore, the part (press-molded part) according to the present invention can reduce the radius of curvature of the corners between the first and second members. This is because the complex material flow behavior in the first partial blank is suppressed, making it less likely for cracks to occur even when the radius of curvature of the corners is reduced. In conventional press molding using tailored blanks (TWBs), the radius of curvature of the corners between the first and second members was approximately 120 mm, but when the present invention was applied, no cracks occurred even when the radius of curvature was 15 mm. For example, in the case of a frame part for an automobile, a smaller radius of curvature of the corners increases the mounting capacity of parts, etc.

[0053] The use of the parts according to the present invention is not particularly limited. For example, they can be applied to automobile parts. Examples of automobile parts include components of a front module (e.g., a front side member and a cross member), a side sill (rocker) and a floor cross member, a floor tunnel and a floor cross member, and components of a rear under module (e.g., a rear side member and a cross member). When applied to automobile parts, improvements in ease of getting in and out can also be expected. Note that the parts referred to here include parts to which the above-mentioned integrated blank is applied.

[0054] <Method for Manufacturing Component> In the method for manufacturing a component according to the present invention, other than manufacturing the integrated blank described above, known methods can be applied, such as press forming methods and joining methods (for example, welding methods such as spot welding, lap welding, and lap fillet welding). To reiterate, the method for manufacturing a component according to the present invention is as follows.

[0055] - preparing a first partial blank corresponding to the first member and a second partial blank corresponding to the second member; - forming a protruding portion in the first partial blank that is a portion of the first partial blank that corresponds to the top plate portion of the second member; - providing a cutout portion in the first partial blank between the protruding portion of the first partial blank and the portion of the first partial blank that corresponds to the standing wall portion of the second member (at this time, it is preferable to cut out the portion of the first partial blank that corresponds to the cutout portion.If necessary, it is also preferable to cut out so as to form a tongue portion); - partially overlapping the first blank and the second blank; - at the overlapping portion, which is the partially overlapping portion, joining at least the protruding portion of the first partial blank and at least a part of the portion of the second partial blank that corresponds to the top plate portion of the second member to form an integrated blank; - press-forming the formed integrated blank, and then further joining the portions that are not joined at the overlapping portion to obtain a part (press-formed part). -Furthermore, if a protruding tongue portion is provided on the first partial blank as necessary, the first member (the tongue portion of the first partial blank) and the second member (the second partial blank) can be joined at the portion corresponding to the tongue portion after press molding.

[0056] As mentioned above, in the overlapping portion, it is preferable to provide a protruding tongue portion on at least one of the following parts of the first partial blank: (a) the protruding portion; (b) the portion corresponding to the vertical wall portion of the first member; and (c) the portion corresponding to the flange portion of the first member.

[0057] The part is typically a part (press-molded part) in which the second member is connected to the upright wall portion of the first member so as to abut against the second member.

[0058] Furthermore, the method for manufacturing a part (press-molded part) includes a portion corresponding to a ridge line that is a boundary between a top plate portion and a standing wall portion of the second member. That is, the method for manufacturing a part (press-molded part) includes a portion in which the first partial blank does not include a portion corresponding to the ridge line of the second member. Preferably, a tip portion of the cutout (a portion where an end of the protrusion in the first partial blank intersects with an end of a portion corresponding to the standing wall portion of the second member) is not located in the portion corresponding to the ridge line of the second member.

[0059] Furthermore, in the method for manufacturing a part (press-molded part), in the first partial blank, the boundary line between the protrusion and the portion corresponding to the vertical wall of the first member is separated from the ridge line defining the boundary between the top plate portion and the vertical wall portion of the first member. That is, the ridge line defining the boundary between the top plate portion and the vertical wall portion of the first member is continuous and uninterrupted. Note that the part referred to here is also included in the part (press-molded part) according to the present invention described above. Therefore, the use of the part according to the present invention is not particularly limited. For example, it can be applied to automotive parts.

[0060] The press forming method is not particularly limited. Existing press forming methods can be applied. For example, either cold forming or hot forming is acceptable. In hot forming, so-called hot stamp forming (hot stamping) may be applied. Here, hot stamping is a method in which a material is heated in a heating furnace or the like and press-formed at a high heated temperature. Because the temperature is high, the material softens compared to room temperature, and the forming load decreases. Furthermore, when the material is a steel plate, a high-strength formed product can be obtained by heating it to the austenite region and then hardening the die at the bottom dead center of the press. Conventional hot stamping methods can be applied to the hot stamping method.

[0061] The joining method for the portion of the first and second partial blanks that is not joined at the overlapping portion after press forming (including the joining of the tongue portion of the first partial blank and the mating second partial blank) is not particularly limited. For example, joining by welding such as spot welding, lap welding, and lap fillet welding is preferred. In particular, spot welding is preferred from the viewpoint of workability. The type of welding is not particularly limited. Resistance welding, laser welding, and the like may be selected and determined as appropriate. For example, spot welding (resistance welding, laser spot welding) is preferred from the viewpoints of applicability to complex shapes, workability, efficiency, and cost.

[0062] By joining the unjoined portions at the overlapping portion of the first and second partial blanks after press molding (including the joint between the tongue portion of the first partial blank and the second partial blank), the joint strength between the first and second parts is increased, further improving rigidity and collision characteristics.

[0063] Example 1 A part was press-formed to resemble a T-shaped part with a hat-shaped cross section that is part of a rear undermodule part of an automobile shown in Fig. 11(a) (Fig. 11(b): a part in which a cross member is connected to the vertical wall of a side member so as to butt against each other). The part specifications were as follows:

[0064] (1) Side member (first member): Hat-shaped cross section Top plate width: 86 mm Vertical wall length: 86 mm Flange width: 40 mm Plate thickness: 2.0 mm Tensile strength: 1180 MPa

[0065] (2) Cross member (second member): Hat-shaped cross section Top plate width: 86 mm Vertical wall length: 67 mm Flange width: 40 mm Plate thickness: 1.0 mm Tensile strength: 1180 MPa

[0066] (3) Part specifications: Intersection angle between side member and cross member: 90° (4) Press forming (cold working): Hydraulic press forming machine

[0067] The following blanks were prepared for press molding. Four blanks were prepared for each sample. [Sample 1] Comparative example: Blank with no overlapping portion (a conventional tailored blank (TWB) in which the end faces of partial blanks are butted together and integrated).

[0068] [Sample 2] Comparative Example: An integrated blank in which the first partial blank and the second partial blank are partially overlapped, the first blank has no notch (i.e., no protrusion), and the overlapping portion is spot-welded over the entire surface.

[0069] [Sample 3] Example of the present invention: An integrated blank in which a first partial blank and a second partial blank are partially overlapped, and at the overlapping portion, a protrusion corresponding to the top plate portion of the second member of the first partial blank is spot-welded to a portion corresponding to the top plate portion of the second partial blank, a notch is provided in a portion of the first partial blank corresponding to the standing wall portion of the second member, and a tongue portion is provided in the protrusion and a portion corresponding to the flange portion of the first member. (The part after press forming corresponds to the part in Figure 11(c). Figure 12 shows a schematic diagram of the integrated blank corresponding to the press-formed part in Figure 11(c). In Figures 11 and 12, the white circles on the top plate portion of the second member schematically indicate the spot-welded locations of the integrated blank.)

[0070] [Sample 4] Example of the present invention: an integrated blank without a tongue portion in Sample 3. That is, in Figure 12, the tongue portions 136, 138 of the first partial blank 110 are absent, a notch is provided in the portion of the first partial blank corresponding to the standing wall portion of the second member, and the protruding portion of the first partial blank and the portion corresponding to the top plate portion of the second partial blank are spot-welded to form an integrated blank.

[0071] Three blanks each of Samples 1 to 4 were press-formed under the same press conditions, and the occurrence of cracks was visually inspected, focusing on the area near the connection between the first and second components, where cracks are likely to occur. The results are shown below. No cracks were found in the second partial blank for any of the samples. [Sample 1] Cracks were found in the flange portion of the first partial blank (4 out of 4 samples). [Sample 2] Cracks were found in the flange portion of the first partial blank (4 out of 4 samples), with cracks extending to the vertical wall portion in three of the samples. [Sample 3] No cracks were found in either the flange or vertical wall portion of the first partial blank. A schematic diagram of the press-formed part for Sample 3 is shown in Figure 11(c). [Sample 4] No cracks were found in either the flange or vertical wall portion of the first partial blank. The schematic diagram of the press-formed part for Sample 4 is the press-formed part in Figure 11(c) without the tongue portions 136 and 138.

[0072] [Example 2] Next, a test was performed by hot stamping. The part shape was the same as in Example 1. The tensile strength of each part after die hardening (after hot stamping) and the press forming method were as follows.

[0073] (1) Side member (first member) Tensile strength after die hardening: 1500 MPa (2) Cross member (second member) Tensile strength after die hardening: 1500 MPa (4) Press forming (hot stamp forming) Hydraulic press forming machine After heating in a heating furnace at 900°C for 5 minutes, the material was transferred to a die in the press over a transfer time of 15 seconds and hot stamp formed. The material was held at the bottom dead center for 30 seconds to harden the die, and then removed.

[0074] As in Example 1, four blanks for each of Samples 1 to 4 were prepared for press forming. Each of Samples 1 to 4 was press-formed under the same press conditions, and the occurrence of cracks was visually inspected as in Example 1. The results are shown below. [Sample 1] Cracks were observed in the flange portion of the first partial blank (four out of four). [Sample 2] Cracks were observed in the flange portion of the first partial blank (four out of four), and in two of the samples, the cracks had also progressed to the vertical wall portion. [Sample 3] No cracks occurred in either the flange or vertical wall portion of the first partial blank. The press-formed part of Sample 3 had the same shape as that of Example 1, and its schematic diagram is shown in Figure 11(c). [Sample 4] No cracks were observed in either the flange or vertical wall portion of the first partial blank. The press-formed part of Sample 4 also had the same shape as that of Example 1. The schematic diagram shows the press-formed part of Figure 11(c) without the tongue portions 136 and 138.

[0075] [Example 3] Next, we simulated the production of the same parts using the same samples (Samples 1 to 4) as in Example 2 by hot stamping to verify the thickness reduction rate. CAE (Autoform® 10) was used for the simulation. The maximum thickness reduction rate and its location are shown below. Note that the maximum thickness reduction rate occurred near the connection between the first and second components, where cracking is likely to occur. Furthermore, the locations of the maximum thickness reduction rates for Samples 1 and 2 matched the cracking locations in Example 2. [Sample 1] 38% (flange portion of the first partial blank) [Sample 2] 27% (flange portion of the first partial blank) [Sample 3] 19% (standing wall portion of the first partial blank) [Sample 4] 19% (standing wall portion of the first partial blank) Since the likelihood of cracking increases when the thickness reduction rate exceeds 25%, it can be seen that the thickness reduction rate was suppressed and cracking was avoided in Samples 3 and 4 according to the present invention.

[0076] From the above, it was confirmed that cracks can be suppressed during integral press forming by using the press-forming blank according to the present invention.

[0077] The present invention can be widely used in a wide range of industrial fields, such as the transportation machinery industry (e.g., automobiles), the general machinery industry, and electrical equipment.

[0078] 1 First member 2 Second member 3 First direction 4 Second direction 5 L-shaped part (L-shaped cross section) 6 L-shaped part (L-shaped cross section with flange) 7 T-shaped part (C-shaped cross section) 8 T-shaped part (Hat-shaped cross section) 11 Portion of first member corresponding to top plate (top plate portion of first member) 12 Portion of first member corresponding to standing wall (standing wall portion of first member) 13 Portion of first member corresponding to flange (flange portion of first member) 21 Portion of second member corresponding to top plate (top plate portion of second member) 22 Portion of second member corresponding to standing wall (standing wall portion of second member) 23 Portion of second member corresponding to flange (flange portion of second member) 110 First partial blank 111 Portion of first partial blank corresponding to top plate (top plate portion of first partial blank) 112 Portion of first partial blank corresponding to standing wall (standing wall portion of first partial blank) 113 Portion of first partial blank corresponding to flange (flange portion of first partial blank) 116 Ridge line of first partial blank (boundary between top plate portion and standing wall portion) 117 Ridge line of first partial blank (boundary between standing wall portion and flange portion) 120 Second partial blank 121 Portion of second partial blank corresponding to top plate (top plate portion of second partial blank) 122 Portion of second partial blank corresponding to standing wall (standing wall portion of second partial blank) 123 Portion of second partial blank corresponding to flange (flange portion of second partial blank) 126 Ridge line of second partial blank (boundary between top plate portion and standing wall portion) 127 Ridge line of second partial blank (boundary between standing wall portion and flange portion) 130 Overlap portion 133 Protruding portion 134 Notch portion 135 Standing wall overlap portion 136 Tongue portion 137 Tongue portion 138 Tongue portion

Claims

1. A press-molding blank for a part in which a first member extending in a first direction and a second member extending in a second direction intersecting the first direction each have a top plate portion and at least one standing wall portion connected to the top plate portion, and the second member has a portion where it is connected to the first member so as to abut against it, wherein the connected portion of the first and second members of the part is formed by partially overlapping a first partial blank corresponding to the first member and a second partial blank corresponding to the second member, and at the overlap portion where the partially overlapped portion is formed, a protruding portion of the first partial blank that is a portion of the first partial blank that corresponds to the top plate portion of the second member is joined to at least a portion of the portion of the second partial blank that corresponds to the top plate portion of the second member, and a notch portion where no first partial blank is provided is provided in the first partial blank between the protruding portion and the portion of the standing wall portion of the second member.

2. A press-molding blank as described in claim 1, wherein the first partial blank has a protruding tongue portion in at least one of the following parts at the overlapping portion: (a) the protruding portion; (b) the portion corresponding to the vertical wall portion of the first member.

3. A press-molding blank according to claim 1, wherein the first member and the second member further have flange portions connected to the vertical wall portions.

4. A press-molding blank as described in claim 3, wherein the first partial blank has a protruding tongue portion in at least one of the following parts at the overlapping portion: (a) the protruding portion; (b) a portion corresponding to the vertical wall portion of the first member; (c) a portion corresponding to the flange portion of the first member.

5. A press-molding blank according to any one of claims 1 to 4, wherein the cutout portion includes a portion corresponding to the ridge line that forms the boundary between the top plate portion and the vertical wall portion of the second member.

6. A press-molding blank according to any one of claims 1 to 5, wherein in the first partial blank, the boundary line between the protrusion and the portion corresponding to the vertical wall of the first member is separated from the ridge line that forms the boundary between the top plate portion and the vertical wall portion of the first member.

7. A press-molding blank according to any one of claims 1 to 6, wherein the part is an automobile part.

8. A press-molded part comprising a first member extending in a first direction and a second member extending in a second direction intersecting the first direction, each having a top plate portion and at least one standing wall portion connected to the top plate portion, and the second member connected to the first member so as to abut against it, wherein the portion of the part where the first and second members are connected is made up of an integrated blank formed by partially overlapping a first partial blank corresponding to the first member and a second partial blank corresponding to the second member, and at the overlapping portion which is the partially overlapped portion, at least a protruding portion which is a portion of the first partial blank which corresponds to the top plate portion of the second member and a portion of the second partial blank which corresponds to the top plate portion of the second member are joined, and further a notch portion where no first partial blank is provided is provided between the protruding portion of the first partial blank and the portion which corresponds to the standing wall portion of the second member.

9. A press-molded part as described in claim 8, wherein the first partial blank has a protruding tongue portion in at least one of the overlapping portions: (a) the protruding portion; (b) the portion corresponding to the vertical wall portion of the first member.

10. The press-formed part according to claim 8, wherein the first member and the second member further have flange portions connected to the upright wall portions.

11. A press-molded part according to claim 10, wherein the first partial blank has a protruding tongue portion in at least one of the following areas at the overlapping portion: (a) the protruding portion; (b) a portion corresponding to the vertical wall portion of the first member; (c) a portion corresponding to the flange portion of the first member.

12. A press-molded part according to any one of claims 8 to 11, wherein the cutout portion includes a portion corresponding to a ridgeline that forms the boundary between the top plate portion and the vertical wall portion of the second member.

13. A press-molded part according to any one of claims 8 to 12, wherein in the first partial blank, the boundary line between the protrusion and the portion corresponding to the vertical wall of the first member is separated from the ridge line that forms the boundary between the top plate portion and the vertical wall portion of the first member.

14. The press-molded part according to any one of claims 8 to 13, wherein the part is an automotive part.

15. A method for manufacturing a part in which a first member extending in a first direction and a second member extending in a second direction intersecting the first direction each have a top plate portion and at least one standing wall portion connected to the top plate portion, and the second member is connected to the first member so as to abut against it, comprising: preparing a first partial blank corresponding to the first member and a second partial blank corresponding to the second member; forming a protruding portion in the first partial blank that is a portion of the first partial blank that corresponds to the top plate portion of the second member; providing a cutout portion that is not present in the first partial blank between the protruding portion of the first partial blank and the portion of the second partial blank that corresponds to the standing wall portion of the second member; partially overlapping the first blank and the second blank; forming an integrated blank by joining at least the protruding portion of the first partial blank to at least a portion of the portion of the second partial blank that corresponds to the top plate portion of the second member at the overlapping portion that is the partially overlapping portion; press-forming the integrated blank, and then further joining the overlapping portion to obtain a part (press-molded part).

16. A method for manufacturing a press-molded part as described in claim 15, wherein the first partial blank has a protruding tongue portion in at least one of the overlapping portions: (a) the protruding portion; (b) the portion corresponding to the vertical wall portion of the first member; and after the press molding, the tongue portion of the first partial blank and the vertical wall portion of the second member are joined.

17. The method for manufacturing a press-molded part according to claim 15, wherein the first member and the second member further have flange portions connected to the upright wall portions.

18. A method for manufacturing a press-molded part as described in claim 17, wherein the first partial blank has a protruding tongue portion in at least one of the following parts at the overlapping portion: (a) the protrusion, (b) a portion corresponding to the vertical wall portion of the first member, and (c) a portion corresponding to the flange portion of the first member, and the tongue portion of the first partial blank and the vertical wall portion of the second member are joined after the press molding.

19. A method for manufacturing a press-molded part according to any one of claims 15 to 18, wherein the cutout portion includes a portion corresponding to the ridgeline that forms the boundary between the top plate portion and the vertical wall portion of the second member.

20. A method for manufacturing a press-molded part according to any one of claims 15 to 19, wherein in the first partial blank, the boundary line between the protrusion and the part corresponding to the vertical wall of the first member is separated from the ridge line that forms the boundary between the top plate part and the vertical wall part of the first member.

21. The method for manufacturing a press-molded part according to any one of claims 15 to 20, wherein the part is an automobile part.

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