Method for manufacturing press-formed product

Abstract

To provide a manufacturing method for a press-formed product having a flange part, which can reduce amounts of spring-back, even when it is difficult to form a sufficient excess thickness part in a portion corresponding to the flange part in a work-piece.SOLUTION: A press-formed product has a wall part and a flange part extending from the wall part, which forms a joint surface which is jointed to the other member. A manufacturing method for the press-formed product comprises steps of: forming an excess thickness part in a portion where a ridge line between the wall part and the flange part in a work-piece is formed and applying compressive stress to the portion where the excess thickness part is formed, while breaking down the excessive thickness part.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a press-formed product.

Background Art

[0002] In a press-formed product released from the load of a mold after forming, springback occurs, which is a change in shape due to the elastic recovery phenomenon of internal stress. The mold is designed in anticipation of the amount of springback. It is preferable that the amount of springback is small.

[0003] For example, Patent Document 1 describes a method for manufacturing a press-formed product having a flange portion. In the method described in Patent Document 1, in the first step, a dimpling bead is formed in a portion corresponding to the flange portion in the workpiece, and in the second step, the dimpling bead is crushed. As a result, compressive stress is applied to the portion where the dimpling bead was formed, so that the tensile stress generated in the flange portion by press forming is reduced, and the amount of springback is reduced.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the press-formed product manufactured by the method described in Patent Document 1, bead marks remain in the portion where the dimpling bead was formed in the flange portion. The flange portion forms a joint surface with another member. When bead marks overlap at the planned joint position on the joint surface, it may cause poor joint.

[0006] Therefore, from the perspective of suppressing the occurrence of poor bonding, it is conceivable to form a dimpling bead in a region of the workpiece that avoids the position corresponding to the planned bonding position in the flange portion. However, in such a limited region, it may be difficult to form a sufficient dimpling bead to reduce the amount of springback.

[0007] Note that such problems can occur not only with dimpling beads but also with other surplus portions that are crushed during the manufacturing process of press-molded products.

[0008] One aspect of the present disclosure provides a technique capable of reducing the amount of springback even when it is difficult to form a sufficient surplus portion in a portion of the workpiece corresponding to the flange portion in a manufacturing method of a press-molded product having a flange portion.

Means for Solving the Problems

[0009] One aspect of the present disclosure is a manufacturing method of a press-molded product having a wall portion and a flange portion extending from the wall portion and forming a joint surface for joining with another member. The manufacturing method of the press-molded product includes forming a surplus portion in a portion where a ridge line between the wall portion and the flange portion in the workpiece is formed, and crushing the surplus portion to apply a compressive stress to the portion where the surplus portion was formed.

[0010] According to such a configuration, even when it is difficult to form a sufficient surplus portion in a portion of the workpiece corresponding to the flange portion, the amount of springback in the press-molded product can be reduced.

[0011] In one aspect of the present disclosure, the surplus portion may have a shape in which the surface where the ridge line is formed in the workpiece is recessed. According to such a configuration, the surplus portion can be formed relatively easily.

[0012] In one aspect of the present disclosure, the flange portion may have a shape curved in a direction along the ridge line. The surplus portion may be formed at least at a position corresponding to the central portion of the ridge line in the workpiece. According to such a configuration, the amount of springback in the press-formed product can be further reduced.

[0013] In one aspect of the present disclosure, the surplus portion may be formed so as to be continuous from a position corresponding to one end of the ridge line in the workpiece to a position corresponding to the other end of the ridge line.

[0014] In one aspect of the present disclosure, a plurality of surplus portions may be formed in a portion where the ridge line is formed in the workpiece.

[0015] In one aspect of the present disclosure, the workpiece may be made of high-tensile steel. According to such a configuration, the forming accuracy can be improved for high-tensile steel in which the amount of springback tends to be large.

Brief Description of the Drawings

[0016]

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Mode for Carrying Out the Invention

[0017] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. [1. Configuration of Press-Molded Product] The press-molded product 1 shown in FIGS. 1 to 4 is a roof reinforcement of a vehicle. The roof reinforcement of a vehicle is a skeletal component that constitutes the roof structure of the vehicle. The press-molded product 1 is arranged so as to extend in the vehicle width direction above the passenger compartment. The "up and down" and "left and right" directions shown in FIGS. 1 to 4 are the up and down direction and the left and right direction in a state where the press-molded product 1 is arranged in the vehicle. The press-molded product 1 of the present embodiment is installed between the upper ends of the left and right center pillars in the vehicle. The press-molded product 1 of the present embodiment is a so-called roof center reinforcement.

[0018] In the vehicle, a roof panel is arranged above the press-molded product 1. The roof panel is an outer plate that constitutes the roof of the vehicle. The roof panel is joined to the press-molded product 1. Also, in the vehicle, a roof reinforcement member may be arranged adjacent to the press-molded product 1 inside the roof panel. The roof reinforcement member is a member that reinforces the roof structure of the vehicle. When the roof reinforcement member is arranged, the roof reinforcement member may be joined to the press-molded product 1.

[0019] The press-molded product 1 has an overall long shape. As shown in FIG. 3, the press-molded product 1 has a shape that is curved in an arc shape in the longitudinal direction. As shown in FIG. 1, the press-molded product 1 includes a main body portion 2, two wall portions 3, and two flange portions 4.

[0020] The main body portion 2 is a plate-shaped portion that is rectangular in plan view. The main body portion 2 is formed such that the central strip-shaped portion is higher than the strip-shaped portions on both sides thereof in a stepped manner.

[0021] The two wall portions 3 are plate-shaped portions extending from the end edges in the short side direction of the main body portion 2. The two wall portions 3 stand up from the respective end edges in the main body portion 2. Hereinafter, the angle θ1 formed by the main body portion 2 and the wall portion 3 is referred to as the first angle θ1. The first angle θ1 for each of the two wall portions 3 may be the same or different according to the design. Further, hereinafter, the ridge line L1 between the main body portion 2 and the wall portion 3 is referred to as the first ridge line L1. The first ridge line L1 is located on the lower surface of the press-formed product 1, but in FIG. 1, for the sake of illustration, the first ridge line L1 is shown at the corresponding position on the upper surface of the press-formed product 1. Note that the upper surface and the lower surface of the press-formed product 1 refer to the upper surface and the lower surface of the press-formed product 1 in a state where the press-formed product 1 is arranged on the vehicle.

[0022] The two flange portions 4 are plate-shaped portions extending from the tips of the two wall portions 3 respectively. The two flange portions 4 extend outward from the tips of the two wall portions 3 of the press-formed product 1 respectively. In other words, each flange portion 4 projects to the side opposite to the main body portion 2 with respect to the adjacent wall portion 3. Hereinafter, the angle θ2 formed by the wall portion 3 and the flange portion 4 is referred to as the second angle θ2. The second angle θ2 for each of the two flange portions 4 may be the same or different according to the design. Further, hereinafter, the ridge line L2 between the wall portion 3 and the flange portion 4 is referred to as the second ridge line L2.

[0023] As described above, the press-formed product 1 has a shape that is curved in an arc shape in the longitudinal direction. For this reason, as shown in FIG. 3, the flange portion 4 has a shape that is curved in an arc shape in the direction along the second ridge line L2. The second ridge line L2 is curved in the longitudinal direction of the press-formed product 1.

[0024] As shown in FIG. 1, the flange portion 4 forms a joint surface 41 for joining the press-formed product 1 to other members. In the present embodiment, the upper surface of the flange portion 4 corresponds to the joint surface 41. The press-formed product 1 of the present embodiment is assumed to be joined to a roof panel and a roof reinforcing member.

[0025] Specifically, a plurality of mastic portions 42 are formed on the joint surface 41 of the flange portion 4. The mastic portion 42 is a portion where the joint surface 41 is recessed. The mastic portion 42 of the present embodiment is a groove-shaped portion (so-called bead) extending along the second ridge line L2. In a state where an adhesive such as a mastic sealer is filled in the mastic portion 42, when another member is overlapped on the joint surface 41 so as to cover the mastic portion 42, the other member and the press-formed product 1 are joined. That is, the mastic portion 42 corresponds to the position where joining with another member is planned. In the present embodiment, the roof panel is joined to the press-formed product 1 by the mastic portion 42.

[0026] Also, when another member is overlapped on the joint surface 41 and spot-welded in a region where the mastic portion 42 is not formed on the joint surface 41, the other member and the press-formed product 1 are joined. That is, the position where the spot weld dots are formed on the joint surface 41 also corresponds to the position where joining with another member is planned. In the present embodiment, the roof reinforcing member is joined to the press-formed product 1 by spot welding on the joint surface 41.

[0027] The press-formed product 1 is made of a high-tensile steel material having a high tensile strength. For example, the press-formed product 1 may be made of a high-tensile steel material having a tensile strength of 980 MPa or more, or may be made of a high-tensile steel material having a tensile strength of 1180 MPa or more. The press-formed product 1 of the present embodiment is made of a high-tensile steel material having a tensile strength of 1430 MPa.

[0028] [2. Manufacturing method of press-formed product] Next, a method for manufacturing the press-formed product 1 will be described. The method for manufacturing the press-formed product 1 includes a first bending step shown in FIG. 5 and a second bending step shown in FIG. 6.

[0029] [2-1. First Bending Step] As shown in FIG. 5, in the first bending step, press forming is performed on the workpiece 10 using the upper die 101 and the lower die 102. The workpiece 10 is a plate-shaped member that serves as the material for the press-formed product 1. The workpiece 10 before the first bending step is flat.

[0030] In the first bending step, the following preliminary bending process, main body forming process, mastic part forming process, and surplus part forming process are performed as one step. In other words, these processes are performed simultaneously. FIG. 7 shows the workpiece 10 after the first bending step, that is, after all the processes included in the first bending step have been performed, in a top view.

[0031] <Preliminary Bending Process> In the preliminary bending process, the workpiece 10 is bent at positions corresponding to the first ridge line L1 and the second ridge line L2 in the completed press-formed product 1. At this stage, the workpiece 10 is not bent to the aforementioned first angle θ1 and second angle θ2, but is bent to an angle larger than the first angle θ1 and the second angle θ2.

[0032] <Main Body Forming Process> In the main body forming process, the portion of the workpiece 10 corresponding to the main body 2 of the completed product is formed into the shape designed as the main body 2.

[0033] <Mastic Part Forming Process> In the mastic part forming process, a mastic part 42 is formed in the portion of the workpiece 10 corresponding to the flange part 4 of the completed product.

[0034] <Surplus Part Forming Process> In the surplus material part forming process, a surplus material part 11 shown in FIG. 7 is formed at a portion of the workpiece 10 where the second ridge line L2 is formed. The surplus material part 11 is temporarily formed on the workpiece 10 in order to reduce the tensile stress generated in the flange part 4 of the finished product by press forming, and is a part that is crushed in the process of forming the workpiece 10 into the shape of the press-formed product 1 of the finished product. In the workpiece 10, there are two portions where the second ridge line L2 is formed corresponding to each of the two second ridge lines L2 in the press-formed product 1 of the finished product. In the present embodiment, the surplus material part 11 is formed in any of these two portions where the second ridge line L2 is formed.

[0035] FIG. 8 is a schematic view showing the shape of a portion corresponding to the second ridge line L2 of the finished product in a front view of the workpiece 10 shown in FIG. 7. In FIG. 8, the shape of the workpiece 10 when the surplus material part 11 is not formed is shown by a two-dot chain line.

[0036] As shown in FIGS. 7 and 8, the surplus material part 11 is a portion having a concave shape on the surface of the workpiece 10 where the second ridge line L2 is formed. More specifically, the surplus material part 11 is a groove-shaped part (so-called bead) extending along the direction corresponding to the second ridge line L2. The surplus material part 11 is formed at a position corresponding to the central part of the second ridge line L2 in the workpiece 10.

[0037] FIG. 9 is a schematic view showing the shape of a portion surrounded by a circle IX in the cross section of the workpiece 10 after the first bending step shown in FIG. 6 is performed. In FIG. 9, the cross-sectional shape of the portion where the surplus material part 11 in the press-formed product 1 of the finished product is formed is shown by a two-dot chain line. Actually, in the first bending step, the workpiece 10 is not bent up to the first angle θ1 and the second angle θ2 as described above, so the workpiece 10 after the first bending step and the press-formed product 1 of the finished product do not overlap neatly as shown in FIG. 9.

[0038] As shown in FIG. 9, the length d1 along the surface of the surplus portion 11 in a cross-section perpendicular to the direction corresponding to the second ridge line L2 in the workpiece 10 is longer than the length d2 along the surface of the portion where the surplus portion 11 was formed in a cross-section perpendicular to the second ridge line L2 of the press-formed product 1 of the finished product. Therefore, when the surplus portion 11 is crushed as described later, compressive stress is applied to the portion where the surplus portion 11 was formed.

[0039] [2-2. Second bending process] As shown in FIG. 6, in the second bending process, press forming using the upper die 201 and the lower die 202 is performed on the workpiece 10 after the first bending process. In the second bending process, the following main bending process and crushing forming process are performed as one process. In other words, these processes are performed simultaneously. The second bending process is performed on the workpiece 10 after the first bending process, that is, by performing all the processes included in the second bending process, the press-formed product 1 is obtained from the workpiece 10.

[0040] <Main bending process> In the main bending process, the workpiece 10 is bent further to a deeper angle at the location bent in the preliminary bending process in the first bending process. The workpiece 10 is bent to an angle such that the angles in the press-formed product 1 of the finished product are the designed first angle θ1 and second angle θ2.

[0041] <Crushing forming process> In the crushing forming process, the surplus portion 11 formed on the workpiece 10 is crushed. Crushing the surplus portion 11 means being formed so as to approach the shape of the workpiece 10 when the surplus portion 11 was not formed in the first bending process.

[0042] When the surplus portion 11 of the workpiece 10 is crushed, compressive stress is applied to the portion where the surplus portion 11 was formed. As a result, in the press-formed product 1 of the finished product, the tensile stress generated in the flange portion 4 by press forming is reduced.

[0043] [3. Effect] According to the embodiments described in detail above, the following effects can be obtained.

[0044] (3a) In the method for manufacturing the press-formed product 1, a surplus portion 11 is formed in a portion of the workpiece 10 where the second ridge line L2 is formed, and then it is crushed.

[0045] According to such a configuration, since the surplus portion 11 is crushed, compressive stress is applied to the portion where the surplus portion 11 was formed. Therefore, in the press-formed product 1 of the finished product, the tensile stress generated in the flange portion 4 can be reduced. Accordingly, even when it is difficult to form a sufficient surplus portion in the portion of the workpiece 10 corresponding to the flange portion 4 of the finished product, the amount of springback in the press-formed product 1 of the finished product can be reduced.

[0046] (3b) The surplus portion 11 has a shape in which the surface where the second ridge line L2 is formed in the workpiece 10 is recessed. According to such a configuration, the surplus portion 11 can be formed relatively easily.

[0047] (3c) The surplus portion 11 is formed at a position corresponding to the central portion of the second ridge line L2 in the workpiece 10.

[0048] In the press-formed product 1 of the finished product, the flange portion 4 has a shape that is curved in an arc shape in the direction along the second ridge line L2. For this reason, it is considered that the tensile stress generated by press forming tends to concentrate in the central region in the direction along the second ridge line L2 in the flange portion 4. According to the above configuration, since the surplus portion 11 is formed and crushed at a position adjacent to the region where the tensile stress in the flange portion 4 of the finished product tends to concentrate, the tensile stress generated in the flange portion 4 can be reduced more effectively. That is, in the press-formed product 1 of the finished product, the amount of springback can be further reduced.

[0049] (3d) In the above embodiment, the surplus portion 11 is formed and crushed on both of the two portions of the workpiece 10 where the second ridge line L2 is formed.

[0050] According to such a configuration, for each of the two flange portions 4 in the finished product, the tensile stress generated by press forming can be reduced. Therefore, compared with the case where the surplus portion 11 is formed and crushed only on one of the two portions where the second ridge line L2 in the workpiece 10 is formed, the amount of springback of the entire press-formed product 1 of the finished product can be further reduced.

[0051] (3e) In this embodiment, the workpiece 10 is made of a high-tensile steel material. For this reason, compared with the case where the workpiece is made of a steel material with low tensile strength, the amount of springback tends to be larger in the press-formed product 1 of the finished product.

[0052] Even in such a case, in the manufacturing process of the press-formed product 1, by forming and crushing the surplus portion 11 in the portion where the second ridge line L2 in the workpiece 10 is formed, the forming accuracy of the press-formed product 1 can be improved.

[0053] [4. Other Embodiments] As described above, the embodiments of the present disclosure have been described. Needless to say, the present disclosure is not limited to the above embodiments and can take various forms.

[0054] (4a) In the above embodiment, the surplus portion 11 is a groove-shaped portion extending along the direction corresponding to the second ridge line L2. In such a case, as shown in FIGS. 10 and 11, the lengths of the surplus portions 11a and 11b along the direction corresponding to the second ridge line L2 are not particularly limited. For example, as shown in FIG. 11, the surplus portion 11b may be formed so as to be continuous from the position corresponding to one end of the second ridge line L2 in the workpiece 10 to the position corresponding to the other end of the second ridge line L2. In FIG. 11, for the sake of illustration, the surplus portion 11b does not extend to the positions corresponding to both ends of the second ridge line L2, but the actual surplus portion 11b extends to the positions corresponding to both ends.

[0055] (4b) In the above-described embodiment, the surplus portion 11 is formed at a position corresponding to the central portion of the second ridge line L2 in the workpiece 10. However, the surplus portion does not necessarily have to be formed at a position corresponding to the central portion of the second ridge line L2 in the workpiece 10. For example, as shown in FIGS. 12 and 13, the surplus portions 11c and 11d are not formed at a position corresponding to the central portion of the second ridge line L2 in the workpiece 10, and may be formed at at least one of the positions corresponding to both sides sandwiching the central portion of the second ridge line L2.

[0056] (4c) In the above-described embodiment, one surplus portion 11 is formed in each of the two portions where the second ridge line L2 is formed in the workpiece 10. However, the number of surplus portions formed corresponding to one second ridge line L2 is not particularly limited. For example, as shown in FIGS. 13 and 14, a plurality of surplus portions 11d and 11e may be formed corresponding to one second ridge line L2.

[0057] (4d) Also, for example, when a plurality of second ridge lines L2 are formed in the workpiece 10 as in the above-described embodiment, the surplus portion 11 does not necessarily have to be formed in all of the plurality of portions where the second ridge line L2 is formed in the workpiece 10.

[0058] (4e) In the above-described embodiment, the surplus portion 11 has a shape in which the surface where the second ridge line L2 is formed in the workpiece 10 is recessed. However, the shape of the surplus portion is not particularly limited. For example, the surplus portion may have a shape in which the surface where the second ridge line L2 is formed in the workpiece 10 bulges. Even in such a case, by forming the length along the surface of the surplus portion in a cross-section perpendicular to the direction corresponding to the second ridge line L2 in the workpiece 10 to be longer than the length along the surface of the portion where the surplus portion was formed in a cross-section perpendicular to the second ridge line L2 of the press-formed product 1 of the finished product, it is possible to apply a compressive stress to the portion where the surplus portion was formed by crushing the surplus portion.

[0059] (4f) In the above-described embodiment, a surplus portion 11 is formed at a portion where the second ridge line L2 in the workpiece 10 is formed. In such a case, a surplus portion may be further formed at a portion corresponding to the flange portion 4 of the finished product in the workpiece 10.

[0060] (4g) In the above-described embodiment, the press-formed product 1 has an overall long shape and is curved in an arc shape in the longitudinal direction. However, the shape of the press-formed product is not particularly limited. For other press-formed products having a wall portion and a flange portion extending from the wall portion, in the manufacturing process, a surplus portion is formed at a portion where the ridge line between the wall portion and the flange portion in the workpiece is formed and then crushed, whereby the amount of springback in the finished product can be reduced.

[0061] (4h) In the above-described embodiment, in the first bending step, the preliminary bending process, the main body portion forming process, the mastic portion forming process, and the surplus portion forming process are performed simultaneously, but these processes do not necessarily have to be performed simultaneously. Further, for example, when these processes are performed sequentially instead of simultaneously, the order is not particularly limited.

[0062] Similarly, in the above-described embodiment, in the second bending step, the main bending process and the crushing forming process are performed simultaneously, but these processes do not necessarily have to be performed simultaneously. Further, for example, when these processes are performed sequentially instead of simultaneously, the order is not particularly limited.

[0063] (4i) The functions of one component in the above-described embodiment may be distributed among a plurality of components, or the functions of a plurality of components may be integrated into one component. Also, a part of the configuration of the above-described embodiment may be omitted. Further, at least a part of the configuration of the above-described embodiment may be added to, replaced with, etc. the configuration of other above-described embodiments.

[0064] [Technical idea disclosed in this specification] [Item 1] A method for manufacturing a press-formed product having a wall portion and a flange portion extending from the wall portion and forming a joint surface for joining to another member. Forming a surplus portion at a portion where a ridge line between the wall portion and the flange portion in the workpiece is formed. Crushing the surplus portion to apply a compressive stress to the portion where the surplus portion was formed. A method for manufacturing a press-formed product, comprising:

[0065] [Item 2] The method for manufacturing a press-formed product according to Item 1, wherein the surplus portion has a shape in which the surface on which the ridge line is formed in the workpiece is recessed.

[0066] [Item 3] The method for manufacturing a press-formed product according to Item 1 or Item 2, wherein the flange portion has a shape curved in a direction along the ridge line, and the surplus portion is formed at least at a position corresponding to the central portion of the ridge line in the workpiece.

[0067] [Item 4] The method for manufacturing a press-formed product according to any one of Items 1 to 3, wherein the surplus portion is formed continuously from a position corresponding to one end of the ridge line in the workpiece to a position corresponding to the other end of the ridge line.

[0068] [Item 5] The method for manufacturing a press-formed product according to any one of Items 1 to 3, wherein a plurality of surplus portions are formed at a portion where the ridge line is formed in the workpiece.

[0069] [Item 6] The method for manufacturing a press-formed product according to any one of Items 1 to 5, wherein A method for manufacturing a press-formed product, wherein the workpiece is made of high-tensile steel.

Explanation of reference numerals

[0070] 1... Press-formed product, 10... Workpiece, 11... Remaining material portion, 2... Main body portion, 3... Wall portion, 4... Flange portion, 41... Joint surface, 42... Mastic portion, L1... First ridge line, L2... Second ridge line.

Claims

1. A method for manufacturing a press-formed product, comprising a wall portion and a flange portion extending from the wall portion and forming a joint surface for joining with other members, forming a surplus portion at a portion where a ridge line between the wall portion and the flange portion in the workpiece is formed, crushing the surplus portion and applying a compressive stress to the portion where the surplus portion was formed, The manufacturing method of a press-formed product provided with these.

2. The method for manufacturing a press-formed product according to Claim 1, wherein the surplus portion has a shape in which the surface on which the ridge line is formed in the workpiece is recessed.

3. The method for manufacturing a press-formed product according to Claim 1 or Claim 2, wherein the flange portion has a shape curved in a direction along the ridge line, and the surplus portion is formed at least at a position corresponding to the central portion of the ridge line in the workpiece.

4. The method for manufacturing a press-formed product according to Claim 1 or Claim 2, wherein the surplus portion is formed so as to be continuous from a position corresponding to one end of the ridge line in the workpiece to a position corresponding to the other end of the ridge line.

5. The method for manufacturing a press-formed product according to Claim 1 or Claim 2, wherein a plurality of surplus portions are formed at a portion where the ridge line is formed in the workpiece.

6. The method for manufacturing a press-formed product according to Claim 1 or Claim 2, wherein the workpiece is made of high-tensile steel.

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