Manufacturing method of press-molded products

Abstract

Prevents cracks from occurring in corners during press molding. [Solution] The manufacturing method of the press-formed product of the present invention comprises a pre-forming process in which a blank material is press-formed into a pre-formed product 40, and a main forming process in which the pre-formed product 40 is formed into a press-formed product, which is a target product. Of the two straight line portions 11', 12 in the pre-formed product 40, of both ends in the extension direction D3 of the straight line portion 11' where the outer vertical wall portion 43 is provided, the end portion closest to the other straight line portion 12 is defined as the proximal end P2, and the end portion opposite the proximal end P2 is defined as the distal end P1, and when the angle between the outer vertical wall portion in the press-formed product and the outer vertical wall portion 43 in the pre-formed product 40 is defined as the opening angle, in the pre-forming process, press-forming is performed so that the opening angle of the proximal end P2 is larger than the opening angle at the distal end P1 and is a positive opening angle.

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a press-molded product. [Background technology]

[0002] In recent years, press-formed products using high-strength metal sheets are used for automobile parts in order to improve the collision safety of automobiles while reducing the weight of the vehicle body. In press forming using high-strength metal sheets, for example, cracks due to a decrease in ductility of the metal sheet and wrinkles due to an increase in yield strength are problems. In particular, in press-formed products having a concavely curved curved portion, not only cracks occur in the flange portion of the curved portion, but also wrinkles occur in the top plate portion and punch shoulder portion of the curved portion.

[0003] Cracks in the flange of the curved portion occur due to stress that pulls the flange in the circumferential direction during press forming. Wrinkles that occur in the top plate and punch shoulder are caused by the reaction force of the stress. As a method for preventing such cracks and wrinkles, for example, it has been proposed to increase the bending radius of the punch shoulder provided in the curved portion from the center toward both ends of the curved portion (see Patent Document 1). In addition to this, it has also been proposed to provide a bead on the top plate of one of the two straight portions in a press-formed product having a substantially L-shape, for example, two straight portions whose extension directions intersect and a curved portion is provided between the straight portions (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-166997 [Patent Document 2] International Publication No. 2012 / 070623 Summary of the Invention [Problem to be solved by the invention]

[0005] Hereinafter, in a press-formed product having a substantially L-shape, the vertical wall on the side where the curved portion is provided may be referred to as an inner vertical wall, and the vertical wall on the back side of the curved portion may be referred to as an outer vertical wall. Also, in the press-formed product, the portion on the opposite side to the curved portion may be referred to as a corner portion.

[0006] Incidentally, among the press-formed products having a substantially L-shape, there are some in which one of the straight portions does not have an outer vertical wall portion, and the outer vertical wall portions provided in the two straight portions are provided independently and not continuous near the corner portions. In such press-formed products, not only cracks and wrinkles occur in the curved portions, but also cracks occur in the corner portions. The cracks in the corner portions are caused by the portion of the straight portion corresponding to the top plate portion being pulled toward the inner vertical wall portion during press forming, and it is difficult to prevent cracks in the corner portions with the manufacturing methods disclosed in Patent Document 1 and Patent Document 2. Therefore, a new measure to prevent cracks in the corner portions is required.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a new molding technology that can suppress the occurrence of cracks in corner portions when manufacturing, for example, a roughly L-shaped press-molded product having two straight portions whose extension directions intersect and a curved portion between these straight portions. [Means for solving the problem]

[0008] A manufacturing method of a press-molded product according to one aspect is a method for manufacturing a press-molded product having a top plate portion having two straight portions extending in different directions and a curved portion provided between the two straight portions, thereby forming an L-shape when viewed from above, an inner vertical wall portion that is continuous with the top plate portion at one end portion where the curved portion is provided, of both end portions in the width direction of the top plate portion, and an outer vertical wall portion that is provided in at least one of the two straight portions and is continuous with the top plate portion at the other end portion opposite the one end portion where the curved portion is provided, of both end portions in the width direction of the top plate portion, The method includes a first forming step of press-molding the intermediate product into a target product and a second forming step of molding the intermediate product into a target product, and is characterized in that, when the end of the two straight line parts in the intermediate product in the extending direction of the straight line part where the outer vertical wall part is provided is the end close to the other straight line part as the proximal end and the end opposite to the proximal end is the distal end, and the angle between the outer vertical wall part in the target product and the outer vertical wall part in the intermediate product is defined as the opening angle, in the first forming step, the opening angle at the proximal end is larger than the opening angle at the distal end and has a positive value. Here, the width direction of the top plate part refers to the direction perpendicular to the extending direction of the straight line parts.

[0009] The intermediate shape of the outer vertical wall portion is preferably such that the opening angle gradually increases from the distal end to the proximal end, and the opening angle at the proximal end is preferably 2 to 20°.

[0010] In addition, in the second forming step, it is preferable that the intermediate shape of the outer vertical wall portion is pressed from the outside using a cam member, thereby forming the intermediate shape of the outer vertical wall portion into the outer vertical wall portion of the target formed product. Effect of the Invention

[0011] According to the present disclosure, it is possible to suppress the occurrence of cracks in corner regions. It is possible. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic perspective view showing an example of a press-formed product according to the present embodiment. [Diagram 2] FIG. 2 is a schematic flow chart showing an example of a manufacturing process for a press-molded product. [Diagram 3] FIG. 3 is a schematic perspective view showing an example of a preform. [Figure 4] FIG. 4(a) is an end view showing the configuration of the preformed product at a distal end P1, and FIG. 4(b) is an end view showing the configuration of the preformed product at a proximal end P2 in the extension direction D3. [Diagram 5] FIG. 5 is an end view showing an example of a mold used in the preforming step. [Figure 6] FIG. 6 is an end view showing an example of a mold used in the main molding step. [Figure 7] Figure 7(a) is an end view showing an example of a force acting at the proximal end P2 when the pre-forming process is performed, and Figure 7(b) is an end view showing an example of a force acting at the distal end P1 when the pre-forming process is performed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the press-formed product shown in this embodiment will be described with reference to the drawings. As shown in Fig. 1, the press-formed product 10 is a generally L-shaped part having two straight line portions 11, 12 that extend in different directions and whose ends intersect. The press-formed product 10 is manufactured by carrying out a preforming step S100 and a main forming step S200 shown in Fig. 2. Here, the press-formed product 10 corresponds to a target product as recited in the claims. The preforming step corresponds to a first forming step as recited in the claims, and the main forming step corresponds to a second forming step as recited in the claims.

[0014] The press-formed product 10 has a curved portion 13 that is concavely curved between the straight portions 11, 12. Hereinafter, at the portion where the straight portions 11, 12 intersect, a portion on the opposite side of the curved portion 13 (a portion indicated by reference symbol 14 in FIG. 1) may be referred to as a corner portion. In addition, in the press-formed product 10, a direction perpendicular to the extending direction of the straight portions 11, 12 is defined as the width direction of the top plate portion 21. In addition, in the width direction of the top plate portion 21, the side where the curved portion 13 is provided is defined as the inner side, and the side where the corner portion 14 is provided is defined as the outer side.

[0015] On the inside of the press-molded product 10, there are provided an inner vertical wall portion 23 continuing from the top plate portion 21 via an upper bent portion 22, and an inner flange portion 25 continuing from the inner vertical wall portion 23 via a lower bent portion 24. Hereinafter, the upper bent portion 22, the inner vertical wall portion 23, the lower bent portion 24, and the inner flange portion 25 may be collectively referred to as the inner component E1.

[0016] On the outside of the straight portion 11 of the press-molded product 10, there are provided an outer vertical wall portion 28 continuing from the top plate portion 21 via an upper bent portion 27, and an outer flange portion 30 continuing from the outer vertical wall portion 28 via a lower bent portion 29. Hereinafter, the upper bent portion 27, the outer vertical wall portion 28, the lower bent portion 29, and the outer flange portion 30 may be collectively referred to as the outer component E2.

[0017] Further, on the outside of the straight portion 12 of the press-formed product 10, an extension portion 33 is provided that is connected to the top plate portion 21 and extends outward. The extension portion 33 is located on substantially the same plane as the top plate portion 21, and the extension portion 33 is provided independently and not continuous with the outer vertical wall portion 28 that is connected to the straight portion 11. The extension portion 33 is provided with a bead 34 along the extension direction D2 of the straight portion 12. The bead 34 is provided to prevent material from being drawn toward the curved portion 13 during press forming, which will be described later.

[0018] In this embodiment, a press-molded product 10 including an inner component E1 having an inner flange portion 25, an outer component E2 having an outer flange portion 30, and an extension portion 33 is exemplified. However, the inner flange portion 25, the outer flange portion 30, and the extension portion 33 are not necessarily required components of the press-molded product 10. Therefore, any of these components may be omitted.

[0019] In the press-molded product 10 of the present embodiment, an example is shown in which the straight portion 12 is provided with an extension portion 33 continuing to the top plate portion 21. However, the press-molded product may be provided in which the straight portion 12 is provided with an outer vertical wall portion continuing to the top plate portion 21 independently of the outer vertical wall portion 28.

[0020] As shown in Fig. 2, the above-mentioned press-formed product 10 is manufactured by a manufacturing process including, for example, a preforming step S100 and a main forming step S200. Although details will be described later, the preforming step S100 is a step of performing press forming on a metal plate (hereinafter referred to as a blank material B) processed into a predetermined shape to manufacture a preformed product 40. Moreover, the main forming step S200 is a step of performing press forming or cam bending forming on the preformed product 40 to manufacture the press-formed product 10 shown in Fig. 1. Here, the preformed product 40 corresponds to an intermediate product recited in the claims.

[0021] First, the configuration of the preformed product 40 will be described with reference to Fig. 3. As shown in Fig. 3, the preformed product 40 has an intermediate shape between the inner constituent element E1 of the press-formed product 10 and the outer constituent element E2 of the press-formed product 10. Hereinafter, the intermediate shape of the outer constituent element E2 of the press-formed product 10 may be referred to as the outer constituent element E2'.

[0022] The outer component E2' of the preform 40 is configured to include an outer vertical wall portion 43 that is continuous with the top plate portion 41 via an upper bent portion 42, and an outer flange portion 45 that is continuous with the outer vertical wall portion 43 via a lower bent portion 44.

[0023] Hereinafter, the extension direction of the straight portion 11' of the preformed product 40 is referred to as D3. Of both ends of the straight portion 11' in the extension direction D3, the end that does not intersect with the straight portion 12 is referred to as the distal end P1. Also, of both ends of the straight portion 11' in the extension direction D3, the end opposite the distal end P1, i.e., the end where the straight portion 11' intersects with the straight portion 12, is referred to as the proximal end P2.

[0024] In the example of the preformed product 40 shown in Fig. 3, the outer vertical wall portion 43 of the straight portion 11' at the distal end P1 is formed at the same angle as the outer vertical wall portion 28 of the straight portion 11 (see Fig. 4(a)). On the other hand, the outer vertical wall portion 43 of the straight portion 11' at the proximal end P2 is open outward from the outer vertical wall portion 28 of the straight portion 11 at a predetermined angle θ (see Fig. 4(b)).

[0025] Hereinafter, the angle θ of the outer vertical wall portion 43 of the preformed product 40 relative to the outer vertical wall portion 28 of the press-formed product 10 will be referred to as the opening angle θ. Note that the counterclockwise direction in FIG. 4 is the positive direction of the opening angle θ. The opening angle at the distal end P1 will be referred to as θ1, and the opening angle at the proximal end P2 will be referred to as θ2. In the preformed product 40, the opening angle θ1 at the distal end P1 and the opening angle θ2 at the proximal end P2 are set as follows.

[0026] The opening angle θ1 at the distal end P1 is set to, for example, 0°. However, it is preferable that the opening angle θ1 at the distal end P1 is appropriately set in consideration of springback in press forming, and forming loads in the preforming process and main forming process. Therefore, the opening angle θ1 may be a positive value or a negative value.

[0027] In addition, the opening angle θ2 at the proximal end P2 is preferably set so that θ2>θ1 with respect to the opening angle θ1 at the distal end P1. However, when the opening angle θ2 at the proximal end P2 is set, for example, to θ2<2°, there is a risk that the effect of suppressing the occurrence of cracks during press molding is too small. In addition, if the opening angle θ2 at the proximal end P2 is set too large, the amount of deformation in the main molding process increases, and it is necessary to pay attention to the dimensional and shape accuracy of the press-molded product. The effect of suppressing the occurrence of cracks during press molding is sufficiently obtained when the opening angle θ2 is set to θ2=20°. Therefore, it is preferable that the opening angle θ2 at the proximal end P2 is set, for example, to θ2=2 to 20°, and further, it is preferable that the angle θ2 is θ2=5° to 15°.

[0028] In this embodiment, the opening angle θ of the outer vertical wall portion 43 of the preformed product 40 gradually increases from the distal end P1 toward the proximal end P2, and the opening angle θ2 at the proximal end P2 is maximum. However, if the opening angle θ2 at the proximal end P2 is a positive value (e.g., θ2=2° to 20°), the opening angle θ does not need to be maximum at the proximal end P2, and may be maximum between the distal end P1 and the proximal end P2, for example.

[0029] The outer flange portion 45 is continuous with the outer vertical wall portion 43 via the lower bent portion 44. The outer flange portion 45 and the lower bent portion 44 form a certain angle. The outer flange portion 45 is parallel to the horizontal plane at the distal end P1. The outer flange portion 45 is inclined with respect to the horizontal plane by, for example, an opening angle θ2 at the proximal end P2.

[0030] Next, a mold used in the preforming step S100 will be described. As shown in Fig. 5(a) and Fig. 5(b), the mold 50 used in the preforming step S100 is composed of, for example, a lower mold 51 and an upper mold 52. The lower mold 51 has, for example, a punch 53.

[0031] As shown in Figures 5(a) and 5(b), at the distal end P1 in the extension direction D3 (direction perpendicular to the paper surface in Figure 5), the angle θ3 of the inclined surface 53c relative to the upper surface 53a of the punch 53 is set to the same angle as the inclination angle of the outer vertical wall portion 28 relative to the top plate portion 21 of the press-molded product 10.

[0032] At the proximal end P2 in the extension direction D3, the angle θ4 of the inclined surface 53c with respect to the upper surface 53a of the punch 53 opens outward by the above-mentioned opening angle θ2 with respect to the inclination angle of the outer vertical wall portion 28 of the press-formed product 10. That is, the inclined surface 53c of the punch 53 is inclined such that the opening angle θ gradually increases from the distal end P1 toward the proximal end P2.

[0033] The bottom surface 53e of the punch 53 maintains a constant angle with respect to the inclined surface 53c. That is, as the opening angle θ of the inclined surface 53c increases, the inclination angle of the bottom surface 53e with respect to the horizontal plane also increases. The inclination angle of the bottom surface 53e with respect to the horizontal plane is the same angle as the opening angle θ.

[0034] The upper die 52 includes a die 54 and a pad 55. The die 54 has an inclined surface 54c that continues through a die shoulder 54b that continues to the lower surface 54a. For example, at the distal end P1 in the extension direction D3, the inclination angle θ5 of the inclined surface 54c relative to the lower surface 54a of the die 54 is set to the same angle as the angle θ3 of the inclined surface 53c relative to the upper surface 53a of the punch 53. In addition, the inclined surface 54c at the proximal end P2 in the extension direction D3 is inclined at an angle θ6 relative to the inclined surface 54c at the distal end P1 in the extension direction D3. The angle θ6 is the same angle as the opening angle θ2. That is, the inclined surface 54c is inclined so that the opening angle θ gradually increases from the distal end P1 to the proximal end P2.

[0035] The lower surface 54a of the die 54 maintains a certain angle with respect to the inclined surface 54c. As described above, the inclined surface 54c is inclined such that the opening angle θ gradually increases from the distal end P1 toward the proximal end P2, so that the lower surface 54a is inclined from the distal end P1 toward the proximal end P2.

[0036] The pad 55 is biased toward the lower die 51 by a biasing means (not shown). When the upper die 52 moves toward the lower die 51, the pad 55 comes into contact with the blank material B before the die 54 of the upper die 52 comes into contact with the blank material B, and the pad 55 clamps the blank material B between the lower die 51 and the die 54.

[0037] Next, the mold used in the main molding step will be described. As shown in Fig. 6, the mold 60 used in the main molding step is composed of, for example, a lower mold 61 and an upper mold 62. The lower mold 61 has, for example, a punch 63 and a cam slider 64 arranged at a processing interval from the punch 63. An insertion space 65 is provided between the punch 63 and the cam slider 64, into which a cam 68, described later, is inserted.

[0038] The punch 63 has an upper surface 63a, a punch shoulder 63b connected to the upper surface 63a, an inclined surface 63c connected to the upper surface 63a via the punch shoulder 63b, a curved surface 63d connected to the lower end of the inclined surface 63c, and a bottom surface 63e connected to the curved surface 63d.

[0039] Although not shown, the inclination angle θ7 of the inclined surface 63c with respect to the upper surface 63a of the punch 63 is the same as the inclination angle of the outer vertical wall portion 28 with respect to the top plate portion 21 of the press-formed product 10.

[0040] The cam slider 64 has a guide surface 64a that is inclined downward toward the punch 63. A cam 68 is in sliding contact with the guide surface 64a of the cam slider 64, and moves the cam 68 toward the punch 63.

[0041] When the lower die 61 moves relatively toward the upper die 62, the pad 67 comes into contact with the preformed product 40 positioned by the punch 63 of the lower die 61, and clamps the preformed product 40 between the punch 63.

[0042] When the lower die 61 moves relatively toward the upper die 62, the cam 68 moves along the guide surface 64a of the cam slider 64, clamping the outer component E2' of the preformed product 40 between the punch 63 and the cam 68, thereby generating the outer component E2 in the press-formed product 10.

[0043] The cam 68 has an inclined surface 68a, a curved portion 68b, and a lower surface 68c. Although not shown, an inclination angle θ8 of the inclined surface 68a with respect to the lower surface 68c of the cam 68 is the same angle as an inclination angle θ7 of the inclined surface 63c with respect to the upper surface 63a of the punch 63.

[0044] Finally, a manufacturing method of the press-formed product 10 will be described. In a preforming step S100, the blank B is press-formed using, for example, a die 50 shown in Fig. 5. This produces a preformed product 40 (see Fig. 3) in which the inner constituent element E1 of the press-formed product 10 and the outer constituent element E2' of the press-formed product 10 are formed.

[0045] As described above, the opening angle θ of the inclined surface 53c of the punch 53 of the mold 50 and the inclined surface 54c of the die 54 increases from the distal end P1 to the proximal end P2 in the extension direction D3. As a result, as shown in FIG. 7(a), in the outer vertical wall portion 43, the height H2 at the proximal end P2 is lower than the height H1 at the distal end P1. That is, when forming the outer vertical wall portion 43, the distance over which the material is pulled from the upper bent portion 42 to the lower bent portion 44 is shortened. That is, the force F1 pulling the corner portion 14' on the upper bent portion 42 is reduced, and cracking of the corner portion 14' is suppressed.

[0046] In addition, when the inner vertical wall portion 23 is formed, the portion 41a on the distal end P1 side of the top plate portion 41 is pulled into the inner vertical wall portion 23. As a result, in the portion 41a on the distal end P1 side, material movement in the M1 direction in FIG. 3 occurs. In association with this material movement, in the portion 41b on the proximal end P2 side, material movement in the M2 direction in FIG. 3 occurs. As the material movement in the M1 direction in FIG. 3 increases, the material movement in the M2 direction in FIG. 3 also increases. This causes the corner portion 14' to crack. As shown in FIG. 7(b), by reducing the opening angle θ1 at the distal end P1 and increasing the force F2 pulling the material from the upper bent portion 42 to the lower bent portion 44, a force can be applied in a direction that prevents the material movement in the M1 direction in FIG. 7(b). As a result, the material movement in the M2 direction in FIG. 3 is reduced, and cracking of the corner portion 14' is suppressed.

[0047] After the preforming step S100, the main forming step S200 is performed. In the main forming step S200, press forming or cam bending is performed on the preformed product 40 manufactured in the preforming step S100. For example, the cam bending is performed using a die 60 shown in FIG. 6. The cam bending is a process in which the upper curved portion 2 formed in the preforming step S100 is opened and bent by an angle θ. In the main forming step S200, the force pulling the upper curved portion 42 toward the lower curved portion 44 is smaller than in the preforming step S100. As a result, the occurrence of cracks in the corner region 14 can be suppressed. Although the cam bending is used in the main forming step, the same effect can be obtained by using press forming.

[0048] In manufacturing the above-mentioned press-molded product 10, it is preferable to use a metal plate having a thickness of 0.6 to 4.0 mm and a tensile strength of 270 to 1800 MPa as the blank material B. The reasons for this include that metal plates having a tensile strength of less than 270 MPa and a thickness of less than 0.6 mm are rarely used in parts of general automobiles and home appliances, that metal plates exceeding 1800 MPa generally have poor ductility and are prone to cracking, and that press molding of metal plates having a thickness of more than 4.0 mm tends to increase the press load and easily damage the die.

[0049] Finally, the thickness reduction rate was measured in the preforming process and the main forming process when a press-formed product was manufactured using a 1180 MPa-class steel plate. An example of the measurement results of the thickness reduction rate is shown in Table 1 below. In measuring the thickness reduction rate, a steel material with a thickness of 1.2 mm, a yield stress of 820 MPa, a tensile strength of 1230 MPa, and an elongation rate of 10% was used as blank material B.

[0050] [Table 1]

[0051] First, a case where the opening angle θ between the distal end P1 and the proximal end P2 in the preforming process was set to θ=0 and press forming was performed in the main forming process was set as Comparative Example 1. A case where the opening angle θ between the distal end P1 and the proximal end P2 in the preforming process was set to θ=15° and press forming was performed in the main forming process was set as Comparative Example 2. Furthermore, a case where the opening angle θ between the distal end P1 and the proximal end P2 in the preforming process was set to θ=0 and cam bending forming was performed in the main forming process was set as Comparative Example 3.

[0052] In addition, cases where the opening angle θ of the proximal end in the preforming process was set to θ = 2, 5, 15, and 20° and press forming was performed in the main forming process are set as Example 1 to Example 4. Furthermore, cases where the opening angle θ of the proximal end in the preforming process was set to θ = 2, 5, 10, 15, and 20° and cam bending forming was performed in the main forming process are set as Example 5 to Example 9.

[0053] In this case, in Comparative Example 1, the sheet thickness reduction rate was 11.2% at the curved portion 13 and 10.7% at the corner portion. In Comparative Example 2, the sheet thickness reduction rate at the corner portion when the preforming step was performed was 11.6%, and the sheet thickness reduction rate at the corner portion when the main forming step was performed was 12.2%. Furthermore, in Comparative Example 3, the sheet thickness reduction rate at the corner portion when the main forming step was performed was 11.2%. However, when the sheet thickness reduction rate is 10% or more, cracks are likely to occur. That is, the results obtained showed that cracks are likely to occur in each of the examples of Comparative Example 1 to Comparative Example 3.

[0054] On the other hand, in Examples 1 to 9, even when the preforming step and the main forming step were performed, the sheet thickness reduction rate was 10% or less. Therefore, it is found that Examples 1 to 9 can suppress the occurrence of cracks compared to Comparative Examples 1 to 3.

[0055] In this embodiment, the preforming step is performed to form the inner component of the preformed product into the same shape as the inner component of the press-formed product. However, in the preforming step, press forming may be performed multiple times to form the inner component of the preformed product 40 into the same shape as the inner component E1 of the press-formed product 10.

[0056] Furthermore, although no specific description has been given of the radius of the upper bend 22 of the curved region 13 in each of the preformed product 40 and the press-formed product 10, the radius may be the same diameter at the center in the curved direction Cd of the curved region 13 and at both ends in the curved direction Cd, or may increase from the center to both ends in the curved direction Cd of the curved region 13.

[0057] For example, if the radius of the upper bent portion 22 is increased from the center to both ends of the curved direction Cd of the curved portion 13, during press molding, the material moves in the ridge direction from both ends of the upper bent portion 22 toward the center of the curved portion 13, and in the inner flange portion 25, the material is drawn toward the midpoint (center) of the curved portion 13.

[0058] Furthermore, as described above, by forming the curved region 13 from material moved from both ends of the upper bent portion 22, the material located adjacent to the top plate portion 21 at the center of the upper bent portion 22 in the curved region 13 does not need to be moved from the upper bent portion 22 when the curved region 13 is formed. Therefore, when the radius of the upper bent portion 22 is increased from the center to both ends in the curvature direction Cd of the curved region 13, there is an effect of suppressing cracks occurring in the inner flange portion 25 of the curved region 13 and wrinkles occurring in the top plate portion 21 and upper bent portion 22 of the curved region 13.

[0059] <Summary of effects> The method for manufacturing a press-formed product of the present invention is a method for manufacturing a press-formed product 10 having a top plate portion 21 having two straight portions 11, 12 with different extending directions and a curved portion 13 provided between the two straight portions 11, 12, which form an L-shape when viewed from above, an inner vertical wall portion 23 that is continuous with the top plate portion 21 at one end portion where the curved portion 13 is provided, among both end portions in the width direction of the top plate portion 21, and an outer vertical wall portion 28 that is provided in at least one straight portion of the two straight portions 11, 12 and that is continuous with the top plate portion 21 at the other end portion opposite to the one end portion where the curved portion 13 is provided, among both end portions in the width direction of the top plate portion 21, the method including a pre-forming step of performing press forming on a blank material B to generate a pre-formed product 40, and a press forming step of forming the pre-formed product 40 into a target product. and a main molding process for molding the preformed product into a molded product. Of the two straight portions 11', 12 in the preformed product 40, the end portion closest to the other straight portion in the extension direction of the straight portion 11' where the outer vertical wall portion 43 is provided is defined as the proximal end P2, and the end portion opposite the proximal end P2 is defined as the distal end P1. When the angle between the outer vertical wall portion 28 in the press-formed product 10, which is the target product, and the outer vertical wall portion 43 in the preformed product 40 is defined as the opening angle, the preformed product 40 generates an outer vertical wall portion 43 in the preformed product 40 that is an intermediate shape of the outer vertical wall portion 28, which is inclined outward with respect to the outer vertical wall portion 28 of the press-formed product 10, which is the target product, and where the opening angle θ with respect to the outer vertical wall portion 28 of the press-formed product 10, which is the target product, becomes larger from the distal end P1 to the proximal end P2.

[0060] In the preforming step S100, the force F1 pulling the corner region 14' and the material movement M2 are reduced, so that stress concentration in the corner region 14' is suppressed, and the occurrence of cracks in the corner region 14' is suppressed.

[0061] In addition, this forming process involves using a cam 68 to press the outer vertical wall portion 43 of the preformed product 40 from the outside, thereby forming the outer vertical wall portion 43 of the preformed product 40 into the outer vertical wall portion 28 of the press-formed product 10, which is the target product.

[0062] Since the main forming process S200 is a process of bending the upper bent portion 42 formed in the pre-forming process S100 by an opening angle θ, it does not promote stress concentration in the corner region 14, and therefore the occurrence of cracks in the corner region 14 is also suppressed in the main forming process. [Explanation of symbols]

[0063] 10 Press-molded products 11,11',12 Straight part 13 Curved area 21 Top plate 23 Inner vertical wall 28 Outer vertical wall section 40 Preformed products 43 Outer vertical wall section 68 Cam P1 Distal end P2 proximal end θ Opening angle θ1 Distal end opening angle θ2 Proximal end opening angle B Blank material

Claims

1. A top plate portion having an L-shape in a top view by having two straight line portions extending in different directions and a curved portion provided between the two straight line portions; an inner vertical wall portion that is continuous with the top plate portion at one end portion where the curved portion is provided, among both ends in the width direction of the top plate portion; an outer vertical wall portion provided in at least one of the two straight line portions and continuing to the top plate portion at the other end portion opposite the one end portion where the curved portion is provided, among both ends in the width direction of the top plate portion; A method for producing a press-molded product having the following features: A first forming step of press-forming a blank material into an intermediate product; a second molding step of molding the intermediate product into a target product; Equipped with Of the two straight line portions in the intermediate molded product, of both ends in the extension direction of the straight line portion in which the outer vertical wall portion is provided, the end portion close to the other straight line portion is defined as a proximal end, and the end portion opposite to the proximal end is defined as a distal end, When the angle between the outer vertical wall portion of the target molded product and the outer vertical wall portion of the intermediate molded product is defined as an opening angle, A method for manufacturing a press-molded product, characterized in that in the first molding step, press molding is performed so that the opening angle at the proximal end is larger than the opening angle at the distal end and is an opening angle of a positive value.

2. 2. The method for manufacturing a press-formed product according to claim 1, wherein the intermediate shape of the outer vertical wall portion is a shape in which the opening angle gradually increases from the distal end to the proximal end.

3. The method for manufacturing a press-molded product according to claim 1 or 2, characterized in that the opening angle is 2 to 20 degrees at the proximal end.

4. The method for manufacturing a press-molded product according to claim 1 or claim 2, characterized in that the second molding process molds the intermediate shape of the outer vertical wall portion into the outer vertical wall portion of the target product by pressing the intermediate shape of the outer vertical wall portion from the outside using a cam material.

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