Method for producing press-molded article

Abstract

This method for manufacturing a press-molded article (1) is a method for manufacturing a press-molded article (1) for reducing an error with respect to a target shape caused by springback after mold release, the press-molded article (1) being curved in plan view and having at least a top plate section (3) and a vertical wall section (5) continuous from the top plate section (3), the method comprising: a molding step for molding the press-molded article (1); a press-molding step in which press-molding is performed using a molding die to which a first pre-estimated angle is imparted, said first pre-estimated angle remaining a torsion (reverse torsion) due to springback in the opposite direction to a torsion (positive torsion) due to springback when press-molding is performed in one step without imparting the pre-estimated angle to the die; and a refurbishment step for press-molding the molded article (17) molded in the molding step using a refurbishment die to which a second estimated angle for reducing the torsion is imparted.

Description

Technical Field

[0001] The present invention relates to a method for producing a press-molded product which is curved in a plan view and has at least a top plate portion and a vertical wall portion continuous from the top plate portion. Background Art

[0002] The stricter collision safety standards for automobiles have increased the collision safety of the vehicle body. In addition, the vehicle body needs to be lightweight in order to improve fuel economy and EVs due to CO2 emission restrictions. In order to achieve both improved collision safety and lightweight, high-strength steel sheets (also called high-strength materials, high-tensile steel sheets) of 590MPa or higher are being developed for vehicle body structural parts.

[0003] Automobile parts include parts of its construction, such as Figure 3 As shown, there is a press-molded product 1 which is curved when viewed from above and has at least a top plate portion 3 and a longitudinal wall portion 5 continuous from the top plate portion 3. When such a press-molded product is press-molded, if the mold is demolded after the mold is moved to the molding bottom dead point, springback occurs and the press-molded product is prone to twist. In particular, in the case of high-strength materials, the stress generated at the molding bottom dead point becomes larger due to the high strength, and the large stress is released after demolding, which easily causes a large twist, which is problematic.

[0004] As a method for reducing such torsion caused by springback, for example, Patent Document 1 discloses a method of providing a press-molded product with a through hole or a groove to reduce the generated stress. In addition, paragraph

[0004] of Patent Document 2 discloses a method of performing press molding using a mold that has a torsion angle in the opposite direction to the springback.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2007-253173

[0008] Patent Document 2: Japanese Patent Application Publication No. 2007-130671 Summary of the invention

[0009] Problems to be solved by the invention

[0010] The press molding method described in Patent Document 1 forms through holes or grooves in the press molded product, resulting in a press molded product having a shape different from the intended one, which causes problems such as reduced rigidity when assembled to a vehicle body and difficulty in joining components.

[0011] In addition, in the press forming method described in Patent Document 2, since the press forming is performed by applying a torsion angle in only one direction opposite to the springback direction to the die, there is a problem that it is difficult to set the torsion angle applied to the die. That is, if the torsion angle is too small, the torsion as the springback cannot be fully eliminated, and if the torsion angle is too large, the torsion in the opposite direction will remain, so it is necessary to give an appropriate torsion angle, but this is difficult to achieve.

[0012] Furthermore, when the same die is used to press-form blanks of different material strengths, or when there are variations in the material, plate thickness, etc. of the blanks to be press-formed, the following problem occurs. That is, even when the same die is used to press-form with a torsion angle applied in only one direction, the degree of springback varies due to differences in material strength, plate thickness, and material, resulting in springback variations of the press-formed product.

[0013] The present invention has been completed in view of the above-mentioned problems, and its purpose is to provide a method for manufacturing a pressed molded product that is curved when viewed from above and has at least a top plate portion and a longitudinal wall portion continuous from the top plate portion, which can reduce the shape error caused by springback after demolding.

[0014] Means for solving problems

[0015] In order to solve the above problems and achieve the purpose, there are the following solutions.

[0016] (1) The method for manufacturing a pressed product of the present invention is a method for manufacturing a pressed product in which an estimated angle is given to a mold in order to reduce the error from a target shape caused by springback after demolding. The pressed product is curved when viewed from above and has at least a top plate portion and a longitudinal wall portion continuous from the top plate portion. The method for manufacturing a pressed product comprises: a molding step, in which press molding is performed using a molding mold given a first estimated angle, wherein the first estimated angle allows a twist (reverse twist) caused by springback to remain in the opposite direction to a twist (positive twist) caused by springback when press molding is performed in one step without giving the estimated angle to the mold; and a trimming step, in which the molded product formed in the molding step is press molded using a trimming mold given a second estimated angle.

[0017] (2) The method for manufacturing a pressed product of the present invention is characterized in that, in the invention of (1) above, the first estimated angle is larger than one process estimated angle, and the one process estimated angle is an estimated angle that makes the torsion caused by springback when the pressed product is pressed in one process become below a specified threshold.

[0018] (3) The method for manufacturing a press-molded product of the present invention is characterized in that, in the invention of (2) above, press-molding analysis and springback analysis of the press-molded product are performed in advance to determine the direction of the torsion caused by the springback and the one process estimated angle.

[0019] (4) The method for manufacturing a press-molded product of the present invention is characterized in that, in the invention of (2) above, actual press molding of the press-molded product is performed in advance, and the direction of the twist caused by springback and the one step estimated angle are calculated.

[0020] (5) The manufacturing method of the pressed molded product of the present invention is characterized in that, in the invention of any one of the above (1) to (4), the first estimated angle or the second estimated angle is the following inclination angle: the inclination angle of the top plate molding surface of the width section at the end of the length direction of the molding mold or the repair mold, with the top plate molding surface of the width section at the center of the length direction of the molding mold or the repair mold as the reference.

[0021] (6) The method for manufacturing a press-molded product of the present invention is characterized in that, in the invention of any one of (1) to (5) above, the absolute value of the second estimated angle in the trimming step is made smaller than the absolute value of the first estimated angle.

[0022] Effects of the Invention

[0023] The method for manufacturing a press-molded product of the present invention can sufficiently reduce the torsion as springback after demolding. The following effects are achieved: it is not necessary to provide through holes or grooves, and the target shape of the press-molded product can be maintained, so that a press-molded product with a better shape than before can be manufactured. In addition, the method for manufacturing a press-molded product of the present invention has the following effects: even if there are differences in material strength, plate thickness, and material deviations in the blank, the same mold can be used to manufacture a press-molded product with sufficiently reduced springback. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is an explanatory diagram of mold estimated angles in a forming step and a restrike step in an example of the invention.

[0025] Figure 2 It is an explanatory diagram of the stress state at the bottom dead point of molding in the molding step and the trimming step in the example of the invention.

[0026] Figure 3 This is an explanatory diagram of an example of a press-molded product that is the subject of the present invention.

[0027] Figure 4 It is an explanatory diagram of the molding process and the finishing process of an embodiment.

[0028] Figure 5 It is an explanatory diagram of the torsion angle of a press-molded product.

[0029] Figure 6 This is a diagram illustrating the estimated angle of the mold.

[0030] Figure 7 It is an explanatory diagram of the torsion angle in the molded product after the molding step and the press-molded product after the repair step in the conventional example.

[0031] Figure 8 It is an explanatory diagram of the stress state at the molding bottom dead point in the molding process and the trimming process in the conventional example.

[0032] Fig. 9 It is an explanatory diagram of the estimated angle of the mold in the molding process and the trimming process in the comparative example.

[0033] Fig.10 It is an explanatory diagram of the stress state at the molding bottom dead point in the molding process and the trimming process in the comparative example.

[0034] Fig.11 This is an explanatory diagram of a press-molded product used as a subject in the examples (part 1).

[0035] Fig.12 This is an explanatory diagram (part 2) of a press-molded product used as a subject in the examples. DETAILED DESCRIPTION

[0036] Hereinafter, an embodiment of the method for producing a press-molded product of the present invention will be described. However, the present invention is not limited to this embodiment.

[0037] The pressed molded article 1 as the object of the present invention is as follows Figure 3 As an example, it is a pressed product having a hat-shaped cross-sectional shape that is curved when viewed from above and has at least a top plate portion 3, a vertical wall portion 5 continuous from the top plate portion 3, and a flange portion 7 at the lower end of the vertical wall portion 5. It should be noted that Figure 3 In the example shown, the flange portion 7 is provided in addition to the top plate portion 3 and the vertical wall portion 5, but the flange portion 7 is not necessarily provided. Figure 3 The effects of the present invention will be described by taking the press-molded product 1 shown as an example.

[0038] like Figure 4 As shown, Figure 3 The pressed product 1 shown in the figure is formed by a forming process ( Figure 4 (a)) and refurbishment process ( Figure 4In the forming process, the blank 9 as a metal plate is pressed by the backing plate 11 and the forming punch 13, and the forming die 15 is relatively moved to form a formed product 17 having a top plate portion 3, a vertical wall portion 5 and a flange portion 7. Then, in the trimming process, the molded product 17 formed in the forming process is trimmed by the trimming punch 19 and the trimming die 21.

[0039] based on Figure 5 The shape of the press-molded product 1 after trimming, particularly the torsion angle, will be described. Figure 5 (a) is a plan view of the press-molded product 1 . Figure 5 (b) is a diagram showing a PP cross section at the center of the longitudinal direction of the press-molded product 1 together with a molding surface at the center of the longitudinal direction of the trimming punch 19 . Figure 5 (c) is a diagram showing a QQ cross section near the end portion in the longitudinal direction of the press-molded product 1 together with a molding surface at the longitudinal center portion of the trimming punch 19 .

[0040] like Figure 5 As shown in the figure, when the cross section of the top plate molding surface at the center of the length direction of the trimming punch 19 is made consistent with the top plate portion 3 of the P-P cross section at the center of the length direction of the press-molded product 1, the Q-Q cross section shape near the end in the length direction is rotated clockwise (right-handed on the paper with the outer side of the bend as the left and the inner side of the bend as the right) relative to the cross section of the top plate molding surface at the center of the length direction of the trimming punch 19. This indicates that the press-molded product 1 is twisted due to springback.

[0041] In the following description, the torsion angle of the molded product 17 and the press molded product 1 is defined as: the cross section of the top plate molding surface of the center portion in the longitudinal direction of the molding punch 13 and the trimming punch 19 is used as a reference (refer to Figure 5 (b)) is the angle formed by the cross section of the top plate portion 3 at the end in the longitudinal direction (in this example, about 10 mm from the end and close to the center) and the cross section of the top plate forming surface at the center in the longitudinal direction of the forming punch 13 and the repair punch 19. And, the angle is set to a + (positive) value when it is offset to the left (counterclockwise) on the paper with the outer side of the bend as the left and the inner side of the bend as the right, and a - (negative) value when it is offset to the right (clockwise) on the paper.

[0042] In addition, the die estimation angle is defined as the cross section (R-R cross section) of the longitudinal center of the top plate forming surface of the forming punch 13 and the repairing punch 19 (refer to Figure 6 (a) and (b)) as the reference, the end in the longitudinal direction (for example, about 10 mm inside from the end) (refer to Figure 6(a) and (c)). The estimated mold angle is set to + (positive) when the paper is rotated to the left (counterclockwise) with the outer side of the bend as the left and the inner side of the bend as the right, and - (negative) when the paper is rotated to the right (clockwise).

[0043] Hereinafter, the process leading to the present invention will be described by describing conventional examples and comparative examples.

[0044] <Previous example>

[0045] In the conventional example, after the molding process, finishing is performed using a mold of the same shape. Figure 7 After the molding process of the conventional example ( Figure 7 (a)) molded product 17A and after the repair process ( Figure 7 (b) QQ cross section near the end portion in the longitudinal direction of the press-molded product 1A (see Figure 5 ). In previous examples, Figure 7 As shown, the torsion angle due to springback after the forming process remains negative, and is not corrected even in the truing process but remains substantially unchanged. Figure 7 The torsion angle due to springback of the molded product 17A after the press molding step shown in (a) is -3.1 degrees. Figure 7 The torsion angle due to springback of the press-molded product 1A after repair shown in (b) is -3.4 degrees.

[0046] Press forming analysis based on the finite element method (FEM) was performed on two steps (forming step and finishing step) in the conventional example. Figure 8 These are contour diagrams of the analysis results. Figure 8 (a) is a diagram showing the stress distribution at the molding bottom dead point of the molded product 17A after the molding step. Figure 8 (b) is a diagram showing the stress distribution at the bottom dead point of the press-molded product 1A after the refurbishment process. Figure 8 As shown, both the molded product 17A and the press-molded product 1A have a large compressive stress caused by shrinkage flange deformation at the outer flange 177A, 7A in the middle of the longitudinal direction, and a large tensile stress caused by stretching flange deformation at the inner flange 177A, 7A. In addition, a large tensile stress is generated on the outer side of the bend of the top plate 173A, 3A, and a large compressive stress is generated on the inner side of the bend of the top plate 173A, 3A. In addition, the above-mentioned compressive stress and tensile stress become smaller near the ends in the longitudinal direction of the molded product 17A and the press-molded product 1A.

[0047] Therefore, when these stresses are released by demolding, in the conventional example, these stresses serve as driving forces to cause torsion at the ends in the longitudinal direction.

[0048] <Comparative Example>

[0049] In the comparative example, in order to eliminate the twist generated in the conventional example, in the forming process, from the longitudinal center toward the longitudinal end, near the longitudinal end (10 mm from the end), a forming die (forming punch 13B) with a one-step estimated angle was used for forming (refer to Fig. 9 (a)), and then in the trimming step, a trimming die (trim punch 19B) of the target shape is used for molding (refer to Fig. 9 (b)). Here, the estimated angle of one process refers to the angle given to the longitudinal end of the molding die in such a way that the torsion caused by the springback when the molded product is molded in one process becomes below a predetermined threshold. In addition, the predetermined threshold refers to the upper limit of the torsion angle that can be allowed as a molded product. The estimated angle of one process in this example is 6.0 degrees in the direction opposite to the torsion caused by the springback relative to the mold of the target shape.

[0050] In the comparative example, since springback is anticipated in the forming process and one process anticipated angle is given, twisting due to springback after the forming process is almost nonexistent, and if forming is performed using the trimming die 19B of the target shape in the trimming process, a shape close to the target shape is obtained.

[0051] Regarding the molding process and the finishing process in the comparative example, press molding analysis based on the finite element method (FEM) was performed. Fig.10 It is a contour plot of the analysis results. Fig.10 (a) is a diagram showing the stress distribution at the molding bottom dead point of the molded product 17B after the molding step.

[0052] Fig.10 (b) is a diagram showing the stress distribution at the bottom dead point of the press-molded product 1B after the refurbishment process. Fig.10 As shown in (a), in the case of the comparative example, at the lower dead point of molding, in the longitudinal center of the molded product 17B, a large compressive stress is generated in the outer flange portion 177B due to the shrinkage flange deformation, and a large tensile stress is generated in the inner flange portion 177B due to the stretching flange deformation. In addition, a large tensile stress is generated on the outer side of the bend of the top plate portion 173B, and a large compressive stress is generated on the inner side of the bend of the top plate portion 173B.

[0053] After demolding in the molding process, springback occurs, but since one process estimation angle produces springback in the opposite direction to the springback in the conventional example, the target shape is roughly achieved after springback. Therefore, at the molding bottom dead point in the trimming process, Fig.10As shown in (b), the generated stress is lower than that of the conventional example, and when the mold is released after the molding bottom dead point in the trimming process, springback hardly occurs and the target shape is achieved.

[0054] However, at the lower dead point of the forming process in the finishing process, some compressive stress remains on the inner side of the bend of the outer flange portion 7B and the top plate portion 3B, and some tensile stress remains on the outer side of the bend of the inner flange portion 7B and the top plate portion 3B, and the stress is not sufficiently reduced. Therefore, when the same mold is used to press-form a blank 9 with different material strengths, when the blank 9 with deviations in material, plate thickness, etc. is press-formed, torsion caused by springback sometimes occurs after the finishing process. That is, as shown in the comparative example, in the method of giving only one process estimation angle through the forming process, the distribution of residual stress of the pressed product 1B is different due to differences in material strength, deviations in material, plate thickness, etc. As a result, even if the same mold is used, springback is sometimes not sufficiently reduced.

[0055] Therefore, in the present invention, the molding step and the finishing step are performed as follows.

[0056] <Molding process>

[0057] The molding process uses a molding die 13C (see Figure 1 (a)) is pressed, and the first estimated angle is such that the torsion caused by springback (reverse torsion) in the opposite direction to the torsion caused by springback (positive torsion) when press forming is performed in one process without providing the estimated angle to the mold remains. As shown in the comparative example, in this example, by setting the estimated angle of one process to 6.0 degrees, the torsion after springback is reduced to the maximum, so in order to retain the negative torsion, the first estimated angle is set to be greater than 6.0 degrees. Specifically, Figure 1 In the molding process (a), relative to Figure 6 For the RR cross section at the center portion in the die length direction, the first estimated angle of the SS cross section in the die length direction is set to 8.0 degrees.

[0058] <Renovation process>

[0059] In the trimming step, the molded product 17C formed in the molding step is press-molded using a trimming die 19C having a second estimated angle for reducing the reverse torsion. After demolding in the molding step, reverse torsion remains due to springback. In order to reduce the reverse torsion, Figure 1 As shown in (b), a second estimated angle (in this example, relative to the springback) is given in the same direction as the springback in order to reduce the reverse torsion. Figure 6The target shape is formed by using a trimming die 19C (for the R-R section in the center of the die length direction, the S-S section near the end of the die length direction has an angle of -6.0 degrees). It should be noted that it is preferred that the absolute value of the second estimated angle in the trimming process is smaller than the absolute value of the first estimated angle.

[0060] FEM analysis was performed on these molding and finishing processes to determine the stress distribution at the bottom dead center of molding. The results are shown in Figure 2 .like Figure 2 As shown in (a), during the molding process, in the longitudinal center of the molded product 17C, a large compressive stress is generated in the outer flange portion 177C due to the shrinkage flange deformation, and a large tensile stress is generated in the inner flange portion 177C due to the stretching flange deformation. In addition, a large tensile stress is generated on the outer side of the bend of the top plate portion 173C, and a large compressive stress is generated on the inner side of the bend of the top plate portion 173C.

[0061] like Figure 2 As shown in (b), in the longitudinal center of the pressed product 1C in the repair process, the compressive stress of the outer flange portion 7C, the tensile stress of the outer side of the bend of the top plate portion 3C, the tensile stress of the inner flange portion 7C, and the compressive stress of the inner side of the bend of the top plate portion 3C are all greatly reduced.

[0062] Compared with the present invention Figure 2 (b) and as a comparative example Fig.10 (b) Figure 2 In the case of the present invention shown in (b), the compressive stress of the outer flange portion 7C and the tensile stress of the inner flange portion 7C are reduced compared to the comparative example. Figure 2 In the case of the present invention shown in (b), the tensile stress on the outer side of the bend of the top plate portion 3C and the compressive stress on the inner side of the bend of the top plate portion 3C are also reduced compared to the comparative example. Figure 2 The stress distribution of the press-molded product 1C after the refurbishment step (b) is different from that of the comparative example. Fig.10 Compared with the stress distribution of the press-molded product 1B after the refurbishment process shown in (b), the stress of the press-molded product as a whole is reduced, and the torsion caused by the springback can be sufficiently reduced. In addition, at the same time, even when the blanks 9 with different material strengths or the blanks 9 with different materials, plate thicknesses, etc. are press-molded using the same mold, the stress generated in the press-molded product 1C can be sufficiently reduced, and as a result, the springback of the press-molded product 1C can be reduced.

[0063] It should be noted that the above description is about a hat-shaped cross-section component, but the present invention is not limited thereto. That is, it can also be applied to a U-shaped cross-section component that is curved when viewed from above and is composed of a top plate and vertical walls on both sides thereof, a Z-shaped cross-section component that is composed of a vertical wall on only one side of the top plate and a flange, and an L-shaped cross-section component that is composed of a top plate and a vertical wall on only one side. In addition, it can also be applied to a case where a part of a press-molded product is curved.

[0064] Example

[0065] In order to confirm the effect of the present invention, a 1470MPa grade steel plate and a 980MPa grade steel plate with a plate thickness of 1.0mm were used as blanks 9, and the difference in torsion angle as springback and the torsion angle caused by the difference in material strength were studied. Fig.11 As shown, the shape of the pressed product 1 is a hat-shaped cross-sectional shape having a top plate portion 3, a vertical wall portion 5 continuous with the top plate portion 3, and a flange portion 7 continuous with the vertical wall portion 5, and the cross-sectional dimensions are as follows: Fig.12 It should be noted that the torsion angle and the estimated mold angle caused by springback are the same as those described above. Taking the cross section of the top plate forming portion in the center of the mold length direction as the reference, the left rotation of the paper with the outer side of the bend as the left and the inner side of the bend as the right is taken as a + (positive) value, and the right rotation of the paper is taken as a - (negative) value.

[0066] First, molding was performed using a mold without a mold estimation angle, and the direction of the torsion (positive torsion) caused by springback was determined. Furthermore, a process estimation angle that can minimize the torsion caused by springback in one process was determined to be 6.0 degrees. Then, the molding process and the finishing process of the above-mentioned prior art example, comparative example, and invention example were implemented. The results are shown in Table 1.

[0067] [Table 1]

[0068]

[0069] As the conventional examples, No. 1-1 (1470 MPa grade material) and No. 1-2 (980 MPa grade material), the die estimated angle was set to 0 degrees in both the molding process and the truing process, and the target shape of the die was used directly. The torsion angles of the pressed molded products 1A after these truing were -3.4 degrees and -2.3 degrees, respectively, and a large torsion was generated due to springback. In addition, the difference in torsion angle caused by material strength after the truing process was as large as -1.1 degrees.

[0070] As the comparative examples No.2-1 (1470MPa grade material) and No.2-2 (980MPa grade material), the estimated angle of one process of the molding process was set to 6.0 degrees, and the estimated angle of the mold in the trimming process was set to 0 degrees. The torsion angle of the press-molded product 1A after these trimmings was 0.6 degrees in the case of No.2-1 (1470MPa grade material), which could reduce the torsion, but it was 2.0 degrees in the case of No.2-2 (980MPa grade material), which caused a large torsion due to springback. As a result, the difference in the torsion angle caused by material strength after the trimming process was -1.4 degrees, which was larger than the difference between No.1-1 and No.1-2 in the conventional example.

[0071] On the other hand, in the inventive examples No. 3-1 (1470 MPa grade material) and No. 3-2 (980 MPa grade material), the first estimated angle of the forming process is set to 7.0 degrees, and the second estimated angle of the trimming process is set to -2.0 degrees. The torsion angle of the pressed molded product 1C after these trimmings is 0.3 degrees in the case of No. 3-1 (1470 MPa grade material) and 0.6 degrees in the case of No. 3-2 (980 MPa grade material), which can reduce the torsion caused by springback. As a result, the difference in torsion angle caused by material strength after the trimming process is -0.3 degrees. Although the material strength of the 1470 MPa grade material and the 980 MPa grade material is greatly different, the difference in torsion angle caused by the difference in material strength when using the same mold is very small. Therefore, it can be seen that even if the same mold is used for press molding of different materials, the springback can be sufficiently reduced.

[0072] As the comparative examples, No. 4-1 (1470 MPa grade material) and No. 4-2 (980 MPa grade material) increased the first estimated angle of the molding process to 8.0 degrees, and set the die estimated angle of the trimming process to 0 degrees. The torsion angle of the press-molded product 1B after these trimmings was 2.2 degrees in the case of No. 4-1 (1470 MPa grade material) and 3.4 degrees in the case of No. 4-2 (980 MPa grade material). In addition, the difference in torsion angle caused by material strength after the trimming process was as large as -1.2 degrees.

[0073] As the inventive examples No.5-1 (1470MPa grade material) and No.5-2 (980MPa grade material), the first estimated angle of the forming process is set to 8.0 degrees, and the second estimated angle of the trimming process is set to -6.0 degrees. The torsion angle of the pressed molded product 1C after these trimmings is 0.1 degrees in the case of No.5-1 (1470MPa grade material) and 0.2 degrees in the case of No.5-2 (980MPa grade material). Both the 1470MPa grade material and the 980MPa grade material can sufficiently reduce the torsion caused by springback. In addition, the difference in torsion angle caused by material strength after the trimming process is -0.1 degrees. Although the material strength of the 1470MPa grade material and the 980MPa grade material is greatly different, even if the same mold is used, the difference in torsion angle caused by the difference in material strength is very small. Therefore, according to the present invention, it can be seen that even if the same mold is used for press molding of different materials, the springback can be sufficiently reduced.

[0074] Industrial Applicability

[0075] The present invention can provide a method for manufacturing a press-molded product that is curved in a plan view and has at least a top plate portion and a vertical wall portion continuous from the top plate portion, which can reduce shape errors caused by springback after demolding.

[0076] Description of Reference Numerals

[0077] 1 Pressed products

[0078] 3 Top plate

[0079] 5 Vertical wall

[0080] 7 Flange

[0081] 9 Billets

[0082] 11 Pads

[0083] 13 Forming punch

[0084] 15 Forming die

[0085] 17 Molded products

[0086] 19 Renovation Punch

[0087] 21 Renovation Die

[0088] 1A Pressed product (conventional example)

[0089] 3A top plate

[0090] 7A flange

[0091] 1B Pressed product (comparative example)

[0092] 3B top plate

[0093] 7B flange

[0094] 1C Pressed product (invention example)

[0095] 3C top plate

[0096] 7C flange

[0097] 13A Forming Punch (Conventional Example)

[0098] 13B Forming Punch (Comparative Example)

[0099] 13C forming punch (invention example)

[0100] 17A molded product (conventional example)

[0101] 173A Top plate

[0102] 177A flange

[0103] 17B molded product (comparative example)

[0104] 173B Top plate

[0105] 177B flange

[0106] 17C molded product (invention example)

[0107] 173C top plate

[0108] 177C flange

[0109] 19A repair punch (conventional example)

[0110] 19B repair punch (comparative example)

[0111] 19C repair punch (invention example)

Claims

1. A method for producing a press-molded product, wherein the press-molded product is curved when viewed from above and has at least a top plate portion and a vertical wall portion continuous from the top plate portion, wherein: The method for manufacturing the press-molded product comprises: A molding step of performing press molding using a molding die having a first estimated angle, wherein the first estimated angle allows a torsion (positive torsion) caused by springback and a torsion (negative torsion) caused by springback in the opposite direction to remain when press molding is performed in one step without providing the estimated angle to the die; and In the trimming step, the molded product formed in the molding step is press-molded using a trimming die having a second estimated angle.

2. The method for producing a press-molded product according to claim 1, wherein: The first estimated angle is larger than a first step estimated angle, which is an estimated angle at which a twist due to springback when the press-molded product is press-molded in one step becomes equal to or smaller than a predetermined threshold value.

3. The method for producing a press-molded product according to claim 2, wherein: The press molding analysis and springback analysis of the press molded product are performed in advance to find the direction of the twist caused by the springback and the one-step estimated angle.

4. The method for producing a press-molded product according to claim 2, wherein: The press-molded product is actually press-molded in advance, and the direction of the twist caused by the springback and the one-step estimated angle are obtained.

5. The method for producing a press-molded product according to any one of claims 1 to 4, characterized in that: The first estimated angle or the second estimated angle is the following inclination angle: the inclination angle of the top plate forming surface of the width section at the end of the length direction of the molding mold or the repair mold, with the top plate molding surface of the width section at the center of the length direction of the molding mold or the repair mold as the reference.

6. The method for producing a press-molded product according to any one of claims 1 to 4, characterized in that: The absolute value of the second estimated angle in the truing step is made smaller than the absolute value of the first estimated angle.

7. The method for producing a press-molded product according to claim 5, wherein: The absolute value of the second estimated angle in the truing step is made smaller than the absolute value of the first estimated angle.

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