Press-formed article manufacturing method

Abstract

The gist of the present disclosure is as follows. (1) A press-formed article manufacturing method for manufacturing a press-formed article by press-forming a metal plate, wherein a vertical wall portion of the press-molded article has a curved portion that is curved in an arc shape in a plate thickness direction or a plate surface direction, and one end of the vertical wall portion in the vertical direction is connected to a top plate portion of the press-molded article via a bent portion, the press-formed article manufacturing method being characterized by including: a step in which, during forming of the vertical wall portion, a flange portion is formed at the other end, in the vertical direction, of the vertical wall portion, and an intermediate formed article is formed by forming a minor angle between the top plate portion and the vertical wall portion to be smaller than the minor angle between the top plate portion and the vertical wall portion in the final shape of the press-formed article, in at least a portion of the vertical wall portion in the longitudinal direction thereof; and a step in which the vertical wall portion of the intermediate formed article is re-formed.

Description

Manufacturing method for press-molded products

[0001] This disclosure relates to a method for manufacturing a press-molded product. This application claims priority to Japanese Patent Application No. 2024-011324, filed on January 29, 2024, the contents of which are incorporated herein by reference.

[0002] For example, as disclosed in Patent Documents 1 to 3, there is known a technique for manufacturing press-formed products (automobile parts) by press-forming a metal plate (for example, a steel plate). ２ In order to reduce CO2 emissions, attempts have been made to manufacture press-formed products using steel plates with a tensile strength of 440 MPa or more (so-called high-tensile steel plates). Since high-tensile steel plates have high tensile strength, using them to manufacture press-formed products is expected to improve collision performance. Furthermore, since the press-formed products can be made thinner, the weight of the press-formed products is reduced, and thus CO2 emissions are also reduced. ２ A reduction in emissions can be expected.

[0003] In order to further increase the strength and reduce the weight of press-formed products, attempts have been made to integrally manufacture press-formed products of complex shapes using high-tensile steel sheets. For example, attempts have been made to integrally manufacture press-formed products having vertical wall portions with arc-shaped curved portions and a top plate portion connected to the vertical wall portions via bent portions.

[0004] Patent No. 5168429 Patent No. 6696611 Patent No. 6841271

[0005] From the viewpoint of reducing manufacturing costs, it is preferable to manufacture press-formed products of complex shapes by cold press forming. However, in this case, there is a problem that the press-formed products are prone to cracks and wrinkles.

[0006] Therefore, the present disclosure has been made in consideration of the above problems, and an object of the present disclosure is to provide a method for manufacturing press-molded products that is capable of producing high-quality press-molded products having complex shapes.

[0007] The gist of the present disclosure is as follows: (1) A method for manufacturing a press-formed product by press-forming a metal plate, wherein a vertical wall portion of the press-formed product has a curved portion that is curved in an arc shape in a plate thickness direction or a plate surface direction, and one end portion in a vertical direction of the vertical wall portion is connected to a top plate portion of the press-formed product via a bent portion, the method comprising: forming a flange portion at the other end portion in the vertical direction of the vertical wall portion when forming the vertical wall portion, and forming the vertical wall portion so that, in at least a part of the longitudinal direction, a minor angle formed between the top plate portion and the vertical wall portion is smaller than the minor angle formed between the top plate portion and the vertical wall portion in a final shape of the press-formed product, to obtain an intermediate formed product; and reforming the vertical wall portion of the intermediate formed product. (2) The method for manufacturing a press-formed product according to (1), characterized in that the following formulas (1) and (2) are satisfied, where R0 is the radius of curvature of the other end of the curved portion of the press-formed product, R1 is the radius of curvature of the other end of the curved portion of the intermediate product, ΔR is the difference between R0 and R1, and TS is the tensile strength of the press-formed product. ΔR<A×R0 / (1+A) (1) A=(-1.2×10 －４ (2) (3) The method for manufacturing a press-formed product according to (1) or (2), characterized in that, when the length of the vertical wall portion of the press-formed product in a cross section perpendicular to the longitudinal direction thereof is L0 and the length of the vertical wall portion of the intermediate formed product in a cross section perpendicular to the longitudinal direction thereof is L1, the following formula (3) is satisfied: L1>L0×0.5 (3) (4) The method for manufacturing a press-formed product according to any one of (1) to (3), characterized in that the metal plate is a steel plate having a tensile strength of 440 MPa or more. (5) The method for manufacturing a press-formed product according to any one of (1) to (4), characterized in that the press forming is cold press forming.

[0008] According to the present disclosure, high-quality press-formed products having complex shapes can be manufactured.

[0009] 1A and 1B are explanatory views showing an example of a press-formed product to which the present embodiment is directed. (a) and (b) are perspective views, and (c) is a cross-sectional view taken along the line A-A in (a) and (b). In the following description, unless otherwise specified, "cross-sectional view" means "a cross-sectional view perpendicular to the longitudinal direction of the vertical wall portion." 1B and 1B are explanatory views showing an example of a press-formed product to which the present embodiment is directed. (a) and (b) are perspective views, and (c) is a cross-sectional view taken along the line B-B in (a) and (b). 1C are plan views showing a conventional method for manufacturing a press-formed product. (a) is a plan view showing an intermediate product after preforming and flat trimming. (b) is a plan view showing a press-formed product that is a final product. 1D are cross-sectional views showing a conventional method for manufacturing a press-formed product. (a) is a cross-sectional view showing an intermediate product after preforming. (b) is a cross-sectional view showing an intermediate product after flat trimming. (c) is a cross-sectional view showing a press-formed product that is a final product. 1D are plan views showing a method for manufacturing a press-formed product according to the present embodiment. (a) is a plan view showing an intermediate product after preforming and flat trimming. 1(b) is a plan view showing a press-formed product that is a final product. FIG. 1(a) is a cross-sectional view showing an intermediate product after pre-forming. FIG. 1(b) is a cross-sectional view showing an intermediate product after flat trimming. FIG. 1(c) is a cross-sectional ... side view (viewed from a direction perpendicular to the plan view) showing a conventional method for manufacturing a press-formed product. FIG. 1(b) is a cross-sectional view showing a conventional method for manufacturing a press-formed product. FIG. 1(c) is a side view showing a method for manufacturing a press-formed product according to the present embodiment. FIG. 1(c) is a cross-sectional view showing a method for manufacturing a press-formed product according to the present embodiment. FIG. 1(a) is a partially cutaway perspective view showing a method for manufacturing a press-formed product according to a first application example. FIG. 1(b) is a partially cutaway perspective view showing a method for manufacturing a press-formed product according to a second application example. FIG. 1(c) is a partially cutaway perspective view showing a method for manufacturing a press-formed product according to a third application example. FIG. 1(c) is a partially cutaway perspective view showing a method for manufacturing a press-formed product according to a fourth application example.

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0011] 1. Example of Press-Formed Product Targeted by the Present Embodiment First, an example of a press-formed product targeted by the present embodiment will be described with reference to FIGS. 1 and 2 .

[0012] 1A and 1B are explanatory views showing press-formed products 100 and 200, which are examples of press-formed products targeted by this embodiment. (a) is a perspective view of the press-formed product 100, (b) is a perspective view of the press-formed product 200, and (c) is a cross-sectional view of the press-formed products 100 and 200. Fig. 1C is a cross-sectional view taken along the arrow A-A at the center in the longitudinal direction of the press-formed products 100 and 200 of Figs. 1A and 1B.

[0013] As shown in Figures 1(a) and (c), the press-formed product 100 has a top plate portion 110, a vertical wall portion 120, and a bent portion 130. The vertical wall portion 120 has a curved portion 120a that is curved in an arc shape in the plate thickness direction. The curved portion 120a is curved so as to be convex toward the inside of the top plate portion 110 in a plan view (top view) or an oblique view (as indicated by the double-headed arrow in Figures 1(a) and 1(b)). The upper end portion in the up-down direction of the vertical wall portion 120 is connected to the top plate portion 110 via the bent portion 130. The top plate portion 110 is a portion that is arranged on the upper end side of the press-formed product 100.

[0014] When the press-formed product 100 is manufactured by press-forming a metal plate, the vertical wall portion 120 is formed by stretching the portion of the metal plate corresponding to the vertical wall portion 120. At this time, cracks may occur in the lower end portion 120b of the vertical wall portion 120.

[0015] 1(b) and 1(c), the press-formed product 200 has a top plate portion 210, a vertical wall portion 220, and a bent portion 230. The vertical wall portion 220 has a curved portion 220a that is curved in an arc shape in the plate surface direction. The curved portion 220a is curved so as to be convex downward in a side view (when viewed horizontally) or an oblique view. The upper end portion in the vertical direction of the vertical wall portion 220 is connected to the top plate portion 210 via the bent portion 230. The top plate portion 210 is a portion that is arranged on the upper end side of the press-formed product 200.

[0016] When the press-formed product 200 is manufactured by press-forming a metal plate, the vertical wall portion 220 is formed by stretching the portion of the metal plate corresponding to the vertical wall portion 220. At this time, cracks may occur in the lower end portion 220b of the vertical wall portion 220.

[0017] 2A and 2B are explanatory views showing press-formed products 300 and 400, which are examples of press-formed products targeted by this embodiment. (a) is a perspective view of the press-formed product 300, (b) is a perspective view of the press-formed product 400, and (c) is a cross-sectional view of the press-formed products 300 and 400. Fig. 2C is a cross-sectional view taken along the arrows B-B at the longitudinal center of the press-formed products 100 and 200 in Figs. 2A and 2B.

[0018] As shown in Figures 2(a) and (c), the press-formed product 300 has a top plate portion 310, a vertical wall portion 320, and a bent portion 330. The vertical wall portion 320 has a curved portion 320a that is curved in an arc shape in the plate thickness direction. The curved portion 320a is curved so as to be convex outward from the top plate portion 310 in a plan view (top view) or an oblique view (as indicated by the double-headed arrow in Figures 2(a) and 2(b)). The upper end portion in the up-down direction of the vertical wall portion 320 is connected to the top plate portion 310 via the bent portion 330. The top plate portion 310 is a portion that is disposed on the upper end side of the press-formed product 300.

[0019] When the press-formed product 300 is manufactured by press-forming a metal plate, the vertical wall portion 320 is formed by shrinking the portion of the metal plate corresponding to the vertical wall portion 320. At this time, wrinkles may occur at the lower end portion 320b of the vertical wall portion 320.

[0020] 2(b) and (c), the press-formed product 400 has a top plate portion 410, a vertical wall portion 420, and a bent portion 430. The vertical wall portion 420 has a curved portion 420a that is curved in an arc shape in the plate surface direction. The curved portion 420a is curved so as to be convex upward in a side view (when viewed horizontally) or an oblique view. The upper end portion of the vertical wall portion 420 is connected to the top plate portion 410 via the bent portion 430. The top plate portion 410 is a portion that is disposed on the upper end side of the press-formed product 400.

[0021] When the press-formed product 400 is manufactured by press-forming a metal plate, the vertical wall portion 420 is formed by shrinking the portion of the metal plate corresponding to the vertical wall portion 420. At this time, wrinkles may occur at the lower end portion 420b of the vertical wall portion 420.

[0022] In this embodiment, the press-forming method is devised to make it difficult for cracks and wrinkles to occur in the press-formed products 100 to 400. The press-forming method (method for manufacturing a press-formed product) according to this embodiment will be described below.

[0023] 2. Comparison between conventional manufacturing method of press-formed product and manufacturing method of press-formed product according to this embodiment Next, a comparison between the conventional manufacturing method of press-formed product and the manufacturing method of press-formed product according to this embodiment will be described.

[0024] (2-1. Regarding the press-formed product 100) Figures 3 and 4 show a conventional method for manufacturing a press-formed product 100. Figure 3 is a plan view showing a conventional method for manufacturing a press-formed product 100. (a) is a plan view showing an intermediate formed product 100' after preforming and flat trimming. (b) is a plan view showing the press-formed product 100, which is the final formed product. Figure 4 is a cross-sectional view showing a conventional method for manufacturing a press-formed product 100. (a) is a cross-sectional view showing the intermediate formed product 100'' after preforming. (b) is a cross-sectional view showing the intermediate formed product 100' after flat trimming. (c) is a cross-sectional view showing the press-formed product 100, which is the final formed product.

[0025] As shown in FIG. 4( a), in a conventional method for manufacturing a press-formed product 100, first, an intermediate formed product 100″ is manufactured by preforming a metal plate. The intermediate formed product 100″ has a top plate portion 110″, a vertical wall portion 120″, a bent portion 130″, and a flange portion 140″. A curved portion (not shown) is formed in the vertical wall portion 120″. The minor angle Wθ formed between the top plate portion 110″ and the vertical wall portion 120″ at the bent portion 130″ is １ is the minor angle Wθ formed by the top plate portion 110 and the vertical wall portion 120 of the press-formed product 100. ０ The minor angle Wθ formed between the top plate portion 110″ and the vertical wall portion 120″ at the bent portion 130″ is approximately the same as １is the minor angle Wθ formed by the top plate portion 110 and the vertical wall portion 120 of the press-formed product 100. ０ and are the same within a range of, for example, ±5°.

[0026] Next, as shown in Figures 3(a) and 4(b), the flange portion 140'' is trimmed (flat trimmed) along a trim line 150 set on the flange portion 140'', thereby manufacturing an intermediate molded product 100'. It should be noted that the flat trimming may be omitted. The intermediate molded product 100' comprises a top plate portion 110', a vertical wall portion 120', a bent portion 130', and a flange portion 140'. A curved portion 120a' is formed in the vertical wall portion 120'. The trim line 150 is set so that the sum of the length of the vertical wall portion 120' and the length of the flange portion 140' of the intermediate molded product 100' is the same as the length of the vertical wall portion 120 of the press-molded product 100, which is the final molded product. The minor angle Wθ formed by the top plate portion 110' and the vertical wall portion 120' at the bent portion 130' is １ is the minor angle Wθ formed by the top plate portion 110 and the vertical wall portion 120 of the press-formed product 100. ０ The minor angle Wθ formed between the top plate portion 110′ and the vertical wall portion 120′ at the bent portion 130′ is approximately the same as １ is the minor angle Wθ formed by the top plate portion 110 and the vertical wall portion 120 of the press-formed product 100. ０ The length of the vertical wall portion 120′ in the cross-sectional view is the distance from the intersection of the vertical wall portion 120′ and the top plate portion 110′ to the end of the vertical wall portion 120′.

[0027] Next, as shown in FIGS. 3( b) and 4(c), the vertical wall portion 120' of the intermediate product 100' is reshaped (flanged down) to produce the press-formed product 100, which is the final product. The press-formed product 100 includes a top plate portion 110, a vertical wall portion 120, and a bent portion 130. The vertical wall portion 120 has a curved portion 120a. Flange down refers to bending down the flange. For example, it also includes a case where the bent portion of the intermediate product is crushed to form a portion of the top plate portion into a vertical wall portion, so that the surface including the flange portion and the surface including the vertical wall portion are flush with each other. Note that by flange down, the lower end portion 120b' of the intermediate product 100' becomes the lower end portion 120b of the press-formed product 100. In other words, the lower end portion 120b' moves to the lower end portion 120b. The arrow in FIG. 3(b) indicates the direction in which the lower end portion 120b' moves to the lower end portion 120b. The horizontal movement distance (bending width) at this time is indicated by L'. The minor angle Wθ between the top plate portion 110' and the vertical wall portion 120' at the bending portion 130' is １ is the minor angle Wθ formed by the top plate portion 110 and the vertical wall portion 120 of the press-formed product 100 ０ The bending width L' is longer because the bending width L' is approximately the same as the bending width L'. Therefore, the amount of elongation of the lower end portion 120b increases, and cracks are more likely to occur in the lower end portion 120b. The minor angle Wθ between the top plate portion 110' and the vertical wall portion 120' at the bending portion 130' is １ is the minor angle Wθ formed by the top plate portion 110 and the vertical wall portion 120 of the press-formed product 100. ０ and are the same within a range of, for example, ±5°.

[0028] 5 and 6 show a manufacturing method of a press-formed product 1 according to this embodiment. FIG. 5 is a plan view showing a manufacturing method of a press-formed product 1 according to this embodiment. (a) is a plan view showing an intermediate formed product 1' after preforming and flat trimming. (b) is a plan view showing the press-formed product 1, which is the final formed product. FIG. 6 is a cross-sectional view showing a manufacturing method of a press-formed product 1 according to this embodiment. (a) is a cross-sectional view showing the intermediate formed product 1'' after preforming. (b) is a cross-sectional view showing the intermediate formed product 1' after flat trimming. (c) is a cross-sectional view showing the press-formed product 1, which is the final formed product.

[0029] As shown in FIG. 6( a), in the manufacturing method of the press-formed product 1 according to this embodiment, first, an intermediate formed product 1″ is manufactured by preforming a metal plate. The intermediate formed product 1″ has a top plate portion 11″, a vertical wall portion 12″, a bent portion 13″, and a flange portion 14″. A curved portion (not shown) is formed in the vertical wall portion 12″. The minor angle Wθ formed between the top plate portion 11″ and the vertical wall portion 12″ at the bent portion 13″ is １ is the minor angle Wθ between the top plate portion 11 and the vertical wall portion 12 in the press-formed product 1 (final shape). ０ is smaller than.

[0030] Next, as shown in Figures 5(a) and 6(b), the flange portion 14'' is trimmed (flat trimmed) along a trim line 15 set on the flange portion 14'' to produce an intermediate molded product 1'. Note that the flat trimming may be omitted. The intermediate molded product 1' includes a top plate portion 11', a vertical wall portion 12', a bent portion 13', and a flange portion 14'. A curved portion 12a' is formed in the vertical wall portion 12'. The trim line 15 is set so that the sum of the length of a portion of the top plate portion 11', the length of the vertical wall portion 12', and the length of the flange portion 14' of the intermediate molded product 1' is the same as the length of the vertical wall portion 12 of the press-molded product 1, which is the final molded product. The length of the vertical wall portion 12' is the distance from the intersection of the extended vertical wall portion 12' and the top plate portion 11' to the end of the vertical wall portion 12'. As shown in FIGS. 6B and 6C, the minor angle Wθ between the top plate portion 11′ and the vertical wall portion 12′ at the bent portion 13′ １ is the minor angle Wθ between the top plate portion 11 and the vertical wall portion 12 of the press-formed product 1. ０ , the bent portion 13' of the intermediate molded product 1' protrudes outward more than the bent portion 13 of the press-formed product 1. As a result, a portion of the top plate portion 11' of the intermediate molded product 1' becomes the vertical wall portion 12 of the press-formed product 1. The bent portion 13' and a portion of the top plate portion 11' of the intermediate molded product 1' become the vertical wall portion 12 of the press-formed product 1. Furthermore, when the vertical length of the cross section of the vertical wall portion 120' of the intermediate molded product 100' is the same as the vertical length of the cross section of the vertical wall portion 12' of the intermediate molded product 1', the length of the flange portion 14' is shorter than the above-mentioned flange portion 140'.

[0031] Next, as shown in Figures 5(b) and 6(c), the vertical wall portion 12' of the intermediate product 1' is reshaped (flanged down) to produce the press-formed product 1, which is the final product. The press-formed product 1 has a top plate portion 11, a vertical wall portion 12, and a bent portion 13. A curved portion 12a is formed in the vertical wall portion 12. The top plate portion 11, the vertical wall portion 12, the curved portion 12a, and the bent portion 13 of the press-formed product 1 correspond to the top plate portion 110, the vertical wall portion 120, the curved portion 120a, and the bent portion 130 of the press-formed product 100, respectively. The vertical wall portion 12 may or may not have a flange portion. Note that the arrow shown in Figure 5(b) indicates the direction in which the lower end portion 12b' moves to the lower end portion 12b.

[0032] By flange-down, the lower end 12b' of the intermediate product 1' becomes the lower end 12b of the press-formed product 1. In other words, the lower end 12b' moves to the lower end 12b. The horizontal movement distance (bending width) at this time is indicated by L. The minor angle Wθ between the top plate portion 11' and the vertical wall portion 12' at the bent portion 13' is １ is the minor angle Wθ between the top plate portion 11 and the vertical wall portion 12 of the press-formed product 1. ０ , the flange portion 14′ is shorter, resulting in a shorter bending width L. This reduces the amount of elongation of the lower end portion 12b, making it possible to suppress cracking of the lower end portion 12b.

[0033] 7 and 8 show a conventional method for manufacturing a press-formed product 200. Fig. 7 is a side view showing a conventional method for manufacturing a press-formed product 200. Fig. 8 is a cross-sectional view showing a conventional method for manufacturing a press-formed product 200.

[0034] As shown in Figures 7 and 8, in a conventional method for manufacturing a press-formed product 200, an intermediate product 200' is first manufactured by preforming and flat trimming a metal plate. The trim line of the flat trim is set so that the sum of the length of a vertical wall portion 220' and the length of a flange portion 240' of the intermediate product 200' is the same as the length of the vertical wall portion 220 of the press-formed product 200, which is the final product. The flat trim may be omitted. The intermediate product 200' has a top plate portion 210', a vertical wall portion 220', a bent portion 230', and a flange portion 240'. A curved portion 220a' is formed in the vertical wall portion 220'. The minor angle Wθ formed by the top plate portion 210' and the vertical wall portion 220' at the bent portion 230' is １ is the minor angle Wθ formed by the top plate portion 210 and the vertical wall portion 220 in the press-formed product 200. ０ The minor angle Wθ formed between the top plate portion 210′ ​​and the vertical wall portion 220′ at the bent portion 230′ is approximately the same as １ is the minor angle Wθ formed by the top plate portion 210 and the vertical wall portion 220 in the press-formed product 200. ０ is the same within a range of, for example, ±5°.

[0035] Next, as shown in Figures 7 and 8, the vertical wall portion 220' of the intermediate formed product 200' is reshaped (flanged down) to produce the press-formed product 200, which is the final formed product. The press-formed product 200 includes a top plate portion 210, a vertical wall portion 220, and a bent portion 230. A curved portion 220a is formed in the vertical wall portion 220. Note that, by flange-down, the lower end portion 220b' of the intermediate formed product 200' becomes the lower end portion 220b of the press-formed product 200. In other words, the lower end portion 220b' moves to the lower end portion 220b. The vertical movement distance (bending width) at this time is indicated by L'. The minor angle Wθ formed by the top plate portion 210' and the vertical wall portion 220' at the bent portion 230' is １ is the minor angle Wθ formed by the top plate portion 210 and the vertical wall portion 220 of the press-formed product 200 ０ Since the bending width L' is approximately the same as the bending width L', the amount of elongation of the lower end portion 220b increases, making it more likely that cracks will occur in the lower end portion 220b. １is the minor angle Wθ formed by the top plate portion 210 and the vertical wall portion 220 in the press-formed product 200. ０ and are the same within a range of, for example, ±5°.

[0036] 9 and 10 show a method for manufacturing a press-formed product 2 according to this embodiment. Fig. 9 is a side view showing the method for manufacturing a press-formed product 2 according to this embodiment. Fig. 10 is a cross-sectional view showing the method for manufacturing a press-formed product 2 according to this embodiment.

[0037] As shown in Figures 9 and 10, in the manufacturing method of the press-formed product 2 according to this embodiment, first, an intermediate formed product 2' is manufactured by preforming and flat trimming a metal plate. The trim line of the flat trim is set so that the sum of the length of the vertical wall portion 22' and the length of the flange portion 24' of the intermediate formed product 2' is the same as the length of the vertical wall portion 22 of the press-formed product 2, which is the final formed product. The flat trim may be omitted. The intermediate formed product 2' has a top plate portion 21', a vertical wall portion 22', a bent portion 23', and a flange portion 24'. A curved portion 22a' is formed in the vertical wall portion 22'. The minor angle Wθ formed by the top plate portion 21' and the vertical wall portion 22' at the bent portion 23' is １ is the minor angle Wθ formed by the top plate portion 21 and the vertical wall portion 22 of the press-formed product 2 ０ is smaller than.

[0038] 9 and 10 , the vertical wall portion 22′ of the intermediate product 2′ is reshaped (flanged down) to produce a press-formed product 2, which is a final product. The press-formed product 2 includes a top plate portion 21, a vertical wall portion 22, and a bending portion 23. A curved portion 22a is formed in the vertical wall portion 22. The top plate portion 21, the vertical wall portion 22, the curved portion 22a, and the bending portion 23 of the press-formed product 2 correspond to the top plate portion 210, the vertical wall portion 220, the curved portion 220a, and the bending portion 230 of the press-formed product 200, respectively.

[0039] By flange-down, the lower end 22b' of the intermediate product 2' becomes the lower end 22b of the press-formed product 2. In other words, the lower end 22b' moves to the lower end 22b. The vertical movement distance (bending width) at this time is indicated by L. The minor angle Wθ between the top plate portion 21' and the vertical wall portion 22' at the bent portion 23' is １is the minor angle Wθ formed by the top plate portion 21 and the vertical wall portion 22 of the press-formed product 2 ０ Therefore, even if the length of the vertical wall portion 220' of the conventional intermediate molded product 200' is the same as the length of the vertical wall portion 22', the lower end portion 22b' of the vertical wall portion 22' will be closer to the lower end portion 22b of the vertical wall portion 22 in the vertical direction. In other words, the bending width L will be shorter. As a result, the amount of elongation of the lower end portion 22b will be smaller, and cracking of the lower end portion 22b can be suppressed. The vertical wall portion 22 may or may not have a flange portion.

[0040] Although the description of the press-formed products 300 and 400 is omitted, the minor angle Wθ between the top plate portion and the vertical wall portion at the bent portion of the intermediate formed product is １ The angle Wθ between the top plate and the vertical wall in the final shape of the press-formed product ０ By making the width smaller than 1 / 2, it is possible to suppress the occurrence of wrinkles at the lower end of the vertical wall portion.

[0041] Furthermore, the above-described method for manufacturing a press-formed product according to this embodiment is preferably applied to the entire longitudinal area of ​​the vertical wall portion, but may also be applied to a part of the longitudinal area of ​​the vertical wall portion.

[0042] <3. Application Examples> (3-1. First Application Example) Next, various application examples will be described. FIG. 11 is a partially cutaway perspective view showing a method for manufacturing a press-formed product according to the first application example. As shown in FIG. 11, it is preferable to manufacture an intermediate product 1' so as to satisfy the following conditions. That is, when the radius of curvature of the lower end 12b of the curved portion 12a of the press-formed product 1 is R0 (mm), the radius of curvature of the lower end 12b' of the curved portion 12a' of the intermediate product 1' is R1 (mm), the difference between R0 and R1 (R0 - R1) is ΔR, and the tensile strength of the press-formed product 1 is TS (MPa), the following formulas (1) and (2) are satisfied. In this case, the occurrence of cracks can be more reliably suppressed. ΔR<A×R0 / (1+A) (1) A=(-1.2×10 －４×TS+0.25) (2) Note that formula (1) indicates the limit of allowable distortion. The radius of curvature R1 is the radius of curvature for the shape at the time when the final step of the previous step is completed (at the time when the intermediate molded product 1' is completed). The tensile strength can be measured, for example, by conducting a tensile test in accordance with JIS Z2241:2022.

[0043] (3-2. Second Applied Example) The second applied example is an application of the first applied example to a manufacturing method of a press-formed product 2. FIG. 12 is a partially cutaway perspective view showing a manufacturing method of a press-formed product according to the second applied example. As shown in FIG. 12, it is preferable to manufacture an intermediate product 2' so as to satisfy the following condition. That is, when the radius of curvature of the lower end 22b of the curved portion 22a of the press-formed product 2 is R0, the radius of curvature of the lower end 22b' of the curved portion 22a' of the intermediate product 2' is R1, the difference between R0 and R1 (R0 - R1) is ΔR, and the tensile strength of the press-formed product 2 is TS, the following formulas (1) and (2) are satisfied. In this case, the occurrence of cracks can be more reliably suppressed. ΔR<A×R0 / (1+A) (1) A=(-1.2×10 －４ ×TS+0.25) (2)

[0044] In the first and second application examples, the radius of curvature can be measured by 3D measurement of the press-formed product.

[0045] (3-3. Third Application Example) FIG. 13 is a partially cutaway perspective view showing a manufacturing method of a press-formed product according to a third application example. As shown in FIG. 13, it is preferable to manufacture an intermediate product 1' so as to satisfy the following condition. That is, when the length of the vertical wall portion 12 (curved portion 12a) of the press-formed product 1 in the cross-sectional view is L0 and the length of the vertical wall portion 12' (curved portion 12a') of the intermediate product 1' is L1, the following formula (3) is satisfied. In this case, the occurrence of cracks can be more reliably suppressed. L1 > L0 × 0.5 (3) Note that the length L0 of the vertical wall portion 12 in the cross-sectional view is the distance from the intersection of the vertical wall portion 12 and the top plate portion 11 to the end of the vertical wall portion 12. Furthermore, the length L1 of the vertical wall portion 12' is the distance from the intersection of the vertical wall portion 12' and the top plate portion 11' to the intersection of the vertical wall portion 12' and the flange portion 14'.

[0046] (3-4. Fourth Application Example) The fourth application example is an application of the third application example to the manufacturing method of the press-formed product 2. FIG. 14 is a partially cutaway perspective view showing the manufacturing method of the press-formed product according to the fourth application example. As shown in FIG. 14, it is preferable to manufacture an intermediate product 2′ so as to satisfy the following condition. That is, when the length of the vertical wall portion 22 (curved portion 22a) of the press-formed product 2 in the cross-sectional view is L0 and the length of the vertical wall portion 22′ (curved portion 22a′) of the intermediate product 2′ is L1, the following formula (3) is satisfied. In this case, the occurrence of cracks can be more reliably suppressed. Note that the length L0 of the vertical wall portion 22 in the cross-sectional view is the distance from the intersection of the vertical wall portion 22 and the top plate portion 21 to the end of the vertical wall portion 22. Furthermore, the length L1 of the vertical wall portion 22′ is the distance from the intersection of the vertical wall portion 22′ and the top plate portion 21′ to the intersection of the vertical wall portion 22′ and the flange portion 24′. L1>L0×0.5 (3)

[0047] <4. Press-forming method, tensile strength of metal plate> The press-forming method of the metal plate is not particularly limited, but cold press-forming is preferable from the viewpoint of manufacturing costs. In addition, the tensile strength of the metal plate used as the material for press-forming is not particularly limited, but it is preferable to use cold press-forming in order to improve the collision performance and CO ２From the viewpoint of reducing emissions (weight reduction), the tensile strength is preferably 440 MPa or more. An example of such a metal plate is a so-called high-tensile steel plate. The upper limit of the tensile strength of the metal plate is preferably 2000 MPa.

[0048] (1. Comparative Example 1) A 980 MPa material having a thickness of 1.4 mm was prepared as a metal plate. This was subjected to a single cold press forming to produce a press-formed product 100. The minor angle Wθ formed between the top plate portion 110 and the vertical wall portion 120 was ０ The angle was 110°, the length L0 of the cross section (cross section perpendicular to the longitudinal direction) of the vertical wall portion 120 was 79.0 mm, and the radius of curvature R0 of the curved portion 120a was 174 mm. The lower end portion 120b of the press-formed product 100 was then observed. As a result, concerns about cracking were found in the lower end portion 120b. The sheet thickness reduction rate was also a very large value of 18.2%.

[0049] (2. Comparative Example 2) The above metal plate was cold-press-formed in the procedure shown in Figs. 4(a) to (c) to produce a press-formed product 100. An intermediate formed product 100' was produced by performing flat trimming (Fig. 4(b)). The minor angle Wθ between the top plate portion 110' and the vertical wall portion 120' of the intermediate formed product 100' was １ is the minor angle Wθ formed by the top plate portion 110 and the vertical wall portion 120 of the press-formed product 100 ０ Next, as shown in FIG. 4(c), the vertical wall portion 120' of the intermediate molded product 100' was remolded (flanged down) to produce the press-molded product 100, which was the final molded product. The minor angle Wθ between the top plate portion 110 and the vertical wall portion 120 ０ The length L0 of the vertical wall portion 120 in the cross section (cross section perpendicular to the longitudinal direction) and the radius of curvature R0 of the curved portion 120a were the same as those in Comparative Example 1. The length of the vertical wall portion 120' in the cross section (cross section perpendicular to the longitudinal direction) of the intermediate molded product 100' was 50.0 mm, the radius of curvature R1 was 155 mm, and the length of the flange portion 140' was 19.0 mm. The lower end portion 120b of the press-molded product 100 was then observed. As a result, concerns about cracking were found in the lower end portion 120b. The plate thickness reduction rate was also a very large value of 9.5%.

[0050] (3. Example 1) The above metal plate was cold-pressed in the procedure shown in Figures 6(a) to 6(c) to produce a press-formed product 1. An intermediate formed product 1' was produced by performing flat trimming (Figure 6(b)). The minor angle Wθ between the top plate portion 11' and the vertical wall portion 12' in the intermediate formed product 1' was １ The angle Wθ between the top plate 11 and the vertical wall 12 was 90°. Next, as shown in FIG. 6(c), the vertical wall 12′ of the intermediate product 1′ was remolded (flanged down) to produce the press-molded product 1, which was the final product. ０ The length L0 of the vertical wall portion 12 in the cross section (cross section perpendicular to the longitudinal direction) and the radius of curvature R0 of the curved portion 12a were the same as those in Comparative Example 1. The length of the vertical wall portion 12' in the cross section (cross section perpendicular to the longitudinal direction) of the intermediate formed product 1' was 50.0 mm, the radius of curvature R1 was 162 mm, and the length of the flange portion 14' was 8.5 mm. The lower end portion 12b of the press-formed product 1 was then observed. As a result, no cracks were found in the lower end portion 12b. The plate thickness reduction rate was also a small value of 7.2%.

[0051] (4. Comparative Example 3) The above metal plate was cold-press-formed in the procedure shown in Figs. 7 and 8 to produce a press-formed product 200. An intermediate product 200' was produced by performing flat trimming (Fig. 7). The minor angle Wθ between the top plate portion 210' and the vertical wall portion 220' of the intermediate product 200' was １ is the minor angle Wθ formed by the top plate portion 210 and the vertical wall portion 220 of the press-formed product 200 ０ 7 and 8, the vertical wall portion 220' of the intermediate molded product 200' was remolded (flanged down) to produce the press-molded product 200, which was the final molded product. ０ The angle was 100°, the length L0 of the cross section (cross section perpendicular to the longitudinal direction) of the vertical wall portion 220 was 79.0 mm, the radius of curvature R0 of the curved portion 220a was 327 mm, the length of the cross section (cross section perpendicular to the longitudinal direction) of the vertical wall portion 220' was 66.6 mm, the radius of curvature R1 was 317 mm, and the length of the flange portion 240' was 8.7 mm. The lower end portion 220b of the press-formed product 200 was then observed. As a result, concerns about cracking were observed at the lower end portion 220b. The plate thickness reduction rate was also 12.3%.

[0052] (5. Example 2) The above metal plate was cold-press-formed in the procedure shown in Figs. 9 and 10 to produce a press-formed product 2. An intermediate product 2' was produced by performing flat trimming (Fig. 9). The minor angle Wθ between the top plate portion 21' and the vertical wall portion 22' in the intermediate product 2' was １ 9 and 10, the vertical wall portion 22' of the intermediate molded product 2' was remolded (flanged down) to produce the press-molded product 2, which was the final molded product. ０ The length L0 of the cross section (cross section perpendicular to the longitudinal direction) of the vertical wall portion 22 and the radius of curvature R0 of the curved portion 22a were the same as those in Comparative Example 3. The length of the cross section (cross section perpendicular to the longitudinal direction) of the vertical wall portion 22' of the intermediate formed product 2' was 67.5 mm, the radius of curvature R1 was 318 mm, and the length of the flange portion 24' was 10.2 mm. The lower end portion 22b of the press-formed product 2 was then observed. As a result, no cracks were found in the lower end portion 22b. The plate thickness reduction rate was also 12.1, which was smaller than that of Comparative Example 3.

[0053] (6. Example 3) In Example 1, when producing the intermediate molded product 1', the radius of curvature R1 was set to 162 mm. As a result, ΔR in the above formula (1) was 12 mm. Since A in the above formula (2) was 0.132 and the radius of curvature R0 was 174 mm, the above formula (1) was satisfied. As a result, no cracks were observed in the lower end portion 12b, and the thickness reduction rate was a very small value of 7.2%.

[0054] (7. Example 4) In Example 1, when manufacturing the intermediate molded product 1', the length L1 of the cross section (cross section perpendicular to the longitudinal direction) of the vertical wall portion 12' was set to 50.0 mm. As a result, the above formula (3) was satisfied. As a result, no cracks were observed in the lower end portion 12b, and the thickness reduction rate was a very small value of 7.2%.

[0055] When press-molded products corresponding to the press-molded products 300 and 400 were manufactured in the same manner as in Example 1, no wrinkles were observed at the lower end portions.

[0056] As described above, according to this embodiment, it is possible to provide a method for manufacturing a press-formed product that is capable of manufacturing a high-quality press-formed product having a complex shape.

[0057] Although the preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art to which the present disclosure pertains can conceive of various modifications or alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0058] According to the present disclosure, high-quality press-formed products having complex shapes can be manufactured.

[0059] 1, 2 Press-molded product 11, 21 Top plate portion 12, 22 Vertical wall portion 12a, 22a Curved portion 12b, 22b Lower end portion

Claims

1. A method for manufacturing a press-formed product by press-forming a metal plate, wherein a vertical wall portion of the press-formed product has a curved portion that is curved in an arc shape in the plate thickness direction or the plate surface direction, and one end portion in the vertical direction of the vertical wall portion is connected to a top plate portion of the press-formed product via a bent portion, the method comprising: a step of forming a flange portion at the other end portion in the vertical direction of the vertical wall portion when forming the vertical wall portion, and forming the vertical wall portion so that the minor angle formed between the top plate portion and the vertical wall portion in at least a part of the longitudinal direction is smaller than the minor angle formed between the top plate portion and the vertical wall portion in the final shape of the press-formed product, to obtain an intermediate formed product; and a step of re-forming the vertical wall portion of the intermediate formed product.

2. The method for manufacturing a press-formed product according to claim 1, wherein the radius of curvature of the other end of the curved portion of the press-formed product is R0, the radius of curvature of the other end of the curved portion of the intermediate product is R1, the difference between R0 and R1 is ΔR, and the tensile strength of the press-formed product is TS, satisfies the following formulas (1) and (2): ΔR<A×R0 / (1+A) (1) A=(-1.2×10 －４ ×TS+0.25) (2) 3. The method for manufacturing a press-formed product according to claim 1 or 2, wherein the length of the vertical wall portion of the press-formed product in a cross section perpendicular to the longitudinal direction of the vertical wall portion is L0, and the length of the vertical wall portion of the intermediate formed product in a cross section perpendicular to the longitudinal direction of the vertical wall portion is L1, satisfies the following formula (3): L1>L0×0.5 (3) 4. The method for manufacturing a press-formed product according to claim 1 or 2, wherein the metal plate is a steel plate having a tensile strength of 440 MPa or more.

5. A method for manufacturing a press-formed product according to claim 1 or 2, characterized in that the press forming is cold press forming.

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