Manufacturing method for press-molded products

Abstract

The gist of this disclosure is as follows. (1) A method for manufacturing a press-molded product by press-molding a metal plate, The vertical wall portion of the press-formed product has a curved portion curved in an arc shape in a plate thickness direction or a plate surface direction, One end of the vertical wall portion in the up-down direction is connected to the top plate portion of the press-formed product via a bent portion, The method for manufacturing the press-molded product includes: a step of forming a flange portion at the other end of the vertical wall portion in the up-down direction during molding of the vertical wall portion, and forming a minor angle formed by the top plate portion and the vertical wall portion in at least a part of the longitudinal direction of the vertical wall portion to be smaller than the minor angle formed by the top plate portion and the vertical wall portion in the final shape of the press-molded product, to obtain an intermediate molded product; and a step of re-forming a vertical wall portion of the intermediate product.

Description

[Technical Field]

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

[0002] For example, as disclosed in Patent Documents 1 to 3, there is known a technique for producing press-formed products (automobile parts) by press-forming a metal plate (e.g., a steel plate). Automobile manufacturers have attempted to produce press-formed products using steel plates (so-called high-tensile steel plates) with a tensile strength of 440 MPa or more in order to improve collision performance and reduce CO2 emissions. Because high-tensile steel plates have high tensile strength, using them to produce press-formed products is expected to improve collision performance. Furthermore, because the press-formed products can be made thinner, the weight of the press-formed products can be reduced, which is expected to result in reduced CO2 emissions.

[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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5168429 [Patent Document 2] Patent No. 6696611 [Patent Document 3] Patent No. 6841271 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[0007] The gist of this disclosure is as follows. (1) A method for manufacturing a press-molded product by press-molding a metal plate, The vertical wall portion of the press-formed product has a curved portion curved in an arc shape in a plate thickness direction or a plate surface direction, One end of the vertical wall portion in the up-down direction is connected to the top plate portion of the press-formed product via a bent portion, The method for manufacturing the press-molded product includes: a step of forming a flange portion at the other end of the vertical wall portion in the up-down direction during molding of the vertical wall portion, and forming a minor angle formed by the top plate portion and the vertical wall portion in at least a part of the longitudinal direction of the vertical wall portion to be smaller than the minor angle formed by the top plate portion and the vertical wall portion in the final shape of the press-molded product, to obtain an intermediate molded product; and a step of remolding the vertical wall portion of the intermediate molded product. fruit, In the step of reshaping the vertical wall portion, the horizontal bending width of the lower end portion of the intermediate formed product is shorter than the horizontal bending width of the lower end portion of the intermediate formed product when the minor angle formed between the top plate portion and the vertical wall portion is approximately the same as the minor angle formed between the top plate portion and the vertical wall portion in the final shape of the press-formed product. A method for manufacturing a press-molded product. (2) A method for manufacturing a press-molded product by press-molding a metal plate, The vertical wall portion of the press-formed product has a curved portion curved in an arc shape in a plate thickness direction or a plate surface direction, One end of the vertical wall portion in the up-down direction is connected to the top plate portion of the press-formed product via a bent portion, The method for manufacturing the press-molded product includes: a step of forming a flange portion at the other end of the vertical wall portion in the up-down direction during molding of the vertical wall portion, and forming a minor angle formed by the top plate portion and the vertical wall portion in at least a part of the longitudinal direction of the vertical wall portion to be smaller than the minor angle formed by the top plate portion and the vertical wall portion in the final shape of the press-molded product, to obtain an intermediate molded product; and reshaping the vertical wall portion of the intermediate molded product, A method for manufacturing a press-molded product, characterized in that in the process of re-molding the vertical wall portion, the vertical bending width of the lower end of the intermediate molded product is shorter than the vertical bending width of the lower end of the intermediate molded product when the minor angle formed by the top plate portion and the vertical wall portion is approximately the same as the minor angle formed by the top plate portion and the vertical wall portion in the final shape of the press-molded product. (3) In the step of reshaping the vertical wall portion, A method for manufacturing a press-molded product according to (1) or (2), characterized in that the press-molded product is molded so that the surface including the flange portion and the surface including the vertical wall portion are flush with each other. ( 4 ) The present invention is characterized in that, when 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, the following formulas (1) and (2) are satisfied: Any one of (3) A method for producing a press-molded product according to claim 1. △R <A×R0 / (1+A) (1) A=(-1.2×10 -4 ×TS+0.25) (2) ( 5 ) (1) characterized in that, when the length of the vertical wall portion in a cross section perpendicular to the longitudinal direction of the vertical wall portion of the press-formed product is L0 and the length of the vertical wall portion in a cross section perpendicular to the longitudinal direction of the vertical wall portion of the intermediate formed product is L1, the following formula (3) is satisfied: Any one of (4) A method for producing a press-molded product according to claim 1. L1>L0×0.5 (3) ( 6 ) (1) to (2) are characterized in that the metal plate is a steel plate having a tensile strength of 440 MPa or more. 5 ) A method for producing a press-molded product according to any one of the above items. ( 7 ) (1) to (2), characterized in that the press forming is cold press forming. 6 ) A method for producing a press-molded product according to any one of the above items. [Effects of the Invention]

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

[0009] [Figure 1] 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 AA in (a) and (b). In the following description, unless otherwise specified, the term "cross-sectional view" refers to a cross-sectional view perpendicular to the longitudinal direction of the vertical wall portion. [Figure 2] 1A and 1B are explanatory views showing an example of a press-formed product to which the present embodiment is applied, in which (a) and (b) are perspective views, and (c) is a cross-sectional view taken along the line BB in (a) and (b). [Figure 3] 1A and 1B are plan views showing a conventional method for manufacturing a press-formed product, in which (a) is a plan view showing an intermediate formed product after preforming and flat trimming, and (b) is a plan view showing the press-formed product as a final formed product. [Figure 4] 1A and 1B are cross-sectional views showing a conventional method for manufacturing a press-formed product, in which (a) is a cross-sectional view showing an intermediate formed product after preforming, (b) is a cross-sectional view showing an intermediate formed product after flat trimming, and (c) is a cross-sectional view showing a press-formed product that is a final formed product. [Figure 5] 1A and 1B are plan views showing a method for manufacturing a press-formed product according to the present embodiment, in which (a) is a plan view showing an intermediate product after preforming and flat trimming, and (b) is a plan view showing a press-formed product that is a final product. [Figure 6] 1A and 1B are cross-sectional views showing a method for manufacturing a press-formed product according to the present embodiment, in which (a) is a cross-sectional view showing an intermediate formed product after preforming, (b) is a cross-sectional view showing an intermediate formed product after flat trimming, and (c) is a cross-sectional view showing a press-formed product that is a final formed product. [Figure 7] FIG. 1 is a side view (viewed from a direction perpendicular to a plan view) showing a conventional method for manufacturing a press-molded product. [Figure 8] 1 is a cross-sectional view showing a conventional method for manufacturing a press-formed product. [Figure 9] 1 is a side view showing a method for manufacturing a press-formed product according to an embodiment of the present invention. FIG. [Figure 10] 1A to 1C are cross-sectional views showing a method for manufacturing a press-formed product according to the present embodiment. [Figure 11] FIG. 2 is a partially cutaway perspective view showing a method for manufacturing a press-molded product according to a first application example. [Figure 12] FIG. 10 is a partially cutaway perspective view showing a method for manufacturing a press-formed product according to a second application example. [Figure 13] FIG. 10 is a partially cutaway perspective view showing a method for manufacturing a press-molded product according to a third application example. [Figure 14] FIG. 10 is a partially cutaway perspective view showing a method for manufacturing a press-molded product according to a fourth application example. DETAILED DESCRIPTION OF THE INVENTION

[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. Examples of press-molded products targeted by this embodiment> First, an example of a press-formed product to which the present embodiment is directed will be described with reference to FIGS.

[0012] 1A and 1B are explanatory views showing press-formed products 100 and 200, which are examples of press-formed products to which the present embodiment is directed. (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 line AA 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 vertical 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-molded product 100 is manufactured by press-molding 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] As shown in FIGS. 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 top end portion 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 diagrams showing press-formed products 300 and 400, which are examples of press-formed products to which this embodiment is directed. (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 shows the press-formed products of FIGS. 2A and 2B. 3 00, 4 00 is a cross-sectional view taken along the arrow BB at the center in the longitudinal direction.

[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-molded product 300 is manufactured by press-molding 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] As shown in Figures 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 top 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 arranged on the upper end side of the press-formed product 400.

[0021] When the press-molded product 400 is manufactured by press-molding 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 in the lower end portion 420b of the vertical wall portion 420.

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

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

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

[0025] As shown in FIG. 4(a), in a conventional method for manufacturing a press-formed product 100, an intermediate formed product 100'' is first produced by preforming a metal plate. The intermediate formed product 100'' has a top plate portion 110'', a vertical wall portion 120'', a bending portion 130'', and a flange portion 140''. A curved portion (not shown) is formed in the vertical wall portion 120''. The minor angle Wθ1 formed by the top plate portion 110'' and the vertical wall portion 120'' at the bending portion 130'' is approximately the same as the minor angle Wθ0 formed by the top plate portion 110 and the vertical wall portion 120 in the press-formed product 100. The minor angle Wθ1 formed by the top plate portion 110'' and the vertical wall portion 120'' at the bending portion 130'' is the same as the minor angle Wθ0 formed by the top plate portion 110 and the vertical wall portion 120 in the press-formed product 100, for example, within a range of ±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'', to produce an intermediate molded product 100'. Note 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 vertical wall portion 120 of the press-molded product 100, which is the final molded product. The minor angle Wθ1 formed by the top plate portion 110' and the vertical wall portion 120' at the bent portion 130' is approximately the same as the minor angle Wθ0 formed by the top plate portion 110 and the vertical wall portion 120 in the press-formed product 100. The minor angle Wθ1 formed by the top plate portion 110' and the vertical wall portion 120' at the bent portion 130' is the same as the minor angle Wθ0 formed by the top plate portion 110 and the vertical wall portion 120 in the press-formed product 100, for example, within a range of ±5°. 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 part of the top plate portion into a vertical wall portion, so that the surface including the flange and the surface including the vertical wall 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 Wθ1 formed by the top plate portion 110' and the vertical wall portion 120' at the bent portion 130' is approximately the same as the minor angle Wθ0 formed by the top plate portion 110 and the vertical wall portion 120 in the press-formed product 100, so the bending width L' becomes longer. As a result, the amount of elongation of the lower end portion 120b increases, making it more likely that cracks will occur in the lower end portion 120b. The minor angle Wθ1 formed by the top plate portion 110' and the vertical wall portion 120' at the bent portion 130' is the same as the minor angle Wθ0 formed by the top plate portion 110 and the vertical wall portion 120 in the press-formed product 100, for example, within a range of ±5°.

[0028] 5 and 6 show a method for manufacturing a press-formed product 1 according to this embodiment. FIG. 5 is a plan view showing a method for manufacturing a press-formed product 1 according to this embodiment. (a) is a plan view showing an intermediate product 1' after preforming and flat trimming. (b) is a plan view showing the press-formed product 1, which is the final product. FIG. 6 is a cross-sectional view showing a method for manufacturing a press-formed product 1 according to this embodiment. (a) is a cross-sectional view showing the intermediate product 1'' after preforming. (b) is a cross-sectional view showing the intermediate product 1' after flat trimming. (c) is a cross-sectional view showing the press-formed product 1, which is the final 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 bending portion 13'', and a flange portion 14''. A curved portion (not shown) is formed in the vertical wall portion 12''. The minor angle Wθ1 formed between the top plate portion 11'' and the vertical wall portion 12'' at the bending portion 13'' is smaller than the minor angle Wθ0 formed between the top plate portion 11 and the vertical wall portion 12 in the press-formed product 1 (final shape).

[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' comprises 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 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'. 6(b) and 6(c), the minor angle Wθ1 formed between the top plate portion 11' and the vertical wall portion 12' at the bent portion 13' is smaller than the minor angle Wθ0 formed between the top plate portion 11 and the vertical wall portion 12 in the press-formed product 1, so the bent portion 13' of the intermediate product 1' protrudes outward from the bent portion 13 of the press-formed product 1. Therefore, a portion of the top plate portion 11' of the intermediate 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 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 product 100' is the same as the vertical length of the cross section of the vertical wall portion 12' of the intermediate 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. 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 Wθ1 formed between the top plate portion 11' and the vertical wall portion 12' at the bent portion 13' is smaller than the minor angle Wθ0 formed between the top plate portion 11 and the vertical wall portion 12 in the press-formed product 1, so the flange portion 14' becomes shorter, and as a result, the bending width L becomes shorter. This reduces the amount of elongation of the lower end 12b, making it possible to suppress cracking of the lower end 12b.

[0033] (2-2. Regarding press-molded product 200) 7 and 8 show a conventional method for manufacturing a press-formed product 200. Fig. 7 is a side view showing the conventional method for manufacturing a press-formed product 200. Fig. 8 is a cross-sectional view showing the conventional method for manufacturing a press-formed product 200.

[0034] As shown in FIGS. 7 and 8 , in a conventional method for manufacturing a press-formed product 200, an intermediate product 200′ is first produced 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 bending portion 230′, and a flange portion 240′. A curved portion 220a′ is formed in the vertical wall portion 220′. The minor angle Wθ1 formed between the top plate portion 210′ ​​and the vertical wall portion 220′ at the bending portion 230′ is approximately the same as the minor angle Wθ0 formed between the top plate portion 210 and the vertical wall portion 220 of the press-formed product 200. The minor angle Wθ1 formed by the top plate portion 210′ ​​and the vertical wall portion 220′ at the bent portion 230′ is smaller than the minor angle Wθ0 formed by the top plate portion 210 and the vertical wall portion 220 in the press-formed product 200. and , for example, within a range of ±5°.

[0035] Next, as shown in Figures 7 and 8, the vertical wall portion 220' of the intermediate product 200' is reshaped (flanged down) to produce the press-formed product 200, which is the final 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 flanging down, the lower end portion 220b' of the intermediate 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 Wθ1 formed by the top plate portion 210' and the vertical wall portion 220' at the bent portion 230' is approximately the same as the minor angle Wθ0 formed by the top plate portion 210 and the vertical wall portion 220 in the press-formed product 200, so the bending width L' becomes longer. As a result, 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. The minor angle Wθ1 formed by the top plate portion 210' and the vertical wall portion 220' at the bent portion 230' is the same as the minor angle Wθ0 formed by the top plate portion 210 and the vertical wall portion 220 in the press-formed product 200, for example, within a range of ±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 a method for manufacturing a press-formed product 2 according to this embodiment. Fig. 10 is a cross-sectional view showing a 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, an intermediate product 2' 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 the vertical wall portion 22' and the length of the flange portion 24' of the intermediate product 2' is the same as the vertical wall portion 22 of the press-formed product 2, which is the final product. The flat trim may be omitted. The intermediate 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 Wθ1 formed between the top plate portion 21' and the vertical wall portion 22' at the bent portion 23' is smaller than the minor angle Wθ0 formed between the top plate portion 21 and the vertical wall portion 22 of the press-formed product 2.

[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 has a top plate portion 21, a vertical wall portion 22, and a bent 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 bent 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 bent 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 Wθ1 between the top plate portion 21' and the vertical wall portion 22' at the bent portion 23' is smaller than the minor angle Wθ0 between the top plate portion 21 and the vertical wall portion 22 in the press-formed product 2. Therefore, even if the length of the vertical wall portion 220' of the conventional intermediate product 200' is the same as the length of the vertical wall portion 22', the lower end 22b' of the vertical wall portion 22' is closer to the lower end 22b of the vertical wall portion 22 in the vertical direction. In other words, the bending width L is shorter. This reduces the elongation of the lower end 22b, thereby suppressing cracking of the lower end 22b. The vertical wall portion 22 may or may not have a flange portion.

[0040] Although explanation of the press-formed products 300 and 400 will be omitted, by making the minor angle Wθ1 between the top plate portion and the vertical wall portion at the bend of the intermediate molded product smaller than the minor angle Wθ0 between the top plate portion and the vertical wall portion in the final shape of the press-formed product, 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 a 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 equation (1) indicates the limit of allowable distortion. The radius of curvature R1 is the radius of curvature of 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 carrying out a tensile test in accordance with JIS Z2241:2022.

[0043] (3-2. Second application example) The second application example is an application of the first application 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 application example. As shown in FIG. 12, it is preferable to manufacture an intermediate product 2' so as to satisfy the following conditions. 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 method for manufacturing 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) In the cross-sectional view, the length L0 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 end of the vertical wall portion 12. In addition, 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 a manufacturing method of a press-formed product 2. FIG. 14 is a partially cutaway perspective view showing a manufacturing method of a 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. In the cross-sectional view, the length L0 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 end of the vertical wall portion 22. In addition, 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 sheet> The method for press-forming the metal plate is not particularly limited, but cold press-forming is preferred from the viewpoint of manufacturing costs. The tensile strength of the metal plate used as the material for press-forming is also not particularly limited, but is preferably 440 MPa or more from the viewpoint of improving collision performance and reducing CO2 emissions (weight reduction). Examples of such metal plates include so-called high-tensile steel plates. The upper limit of the tensile strength of the metal plate is preferably 2000 MPa. [Example]

[0048] (1. Comparative Example 1) A 980 MPa material with a thickness of 1.4 mm was prepared as a metal plate. This was cold-pressed once to produce a press-formed product 100. The minor angle Wθ0 between the top plate portion 110 and the vertical wall portion 120 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 cracks were found in the lower end portion 120b. The thickness reduction rate was also a very large value of 18.2%.

[0049] (2. Comparative Example 2) The press-formed product 100 was manufactured by cold press-forming the above metal plate according to the procedure shown in FIGS. 4(a) to 4(c). An intermediate product 100' was manufactured by performing flat trimming (FIG. 4(b)). The minor angle Wθ1 between the top plate portion 110' and the vertical wall portion 120' of the intermediate product 100' was set to match the minor angle Wθ0 between the top plate portion 110 and the vertical wall portion 120 of the press-formed product 100. Next, as shown in FIG. 4(c), the vertical wall portion 120' of the intermediate product 100' was reshaped (flanged down) to manufacture the press-formed product 100, which was the final product. The minor angle Wθ0 between the top plate portion 110 and the vertical wall portion 120, the length L0 of the cross section (cross section perpendicular to the longitudinal direction) of the vertical wall portion 120, and the curvature radius R0 of the curved portion 120a were the same as those in Comparative Example 1. The cross section (cross section perpendicular to the longitudinal direction) of the vertical wall portion 120' of the intermediate formed product 100' had a length of 50.0 mm, a radius of curvature R1 of 155 mm, and a length of the flange portion 140' of 19.0 mm. The lower end portion 120b of the press-formed product 100 was then observed. As a result, there was concern about cracks in the lower end portion 120b. The sheet thickness reduction rate was also a very large value of 9.5%.

[0050] 3. Example 1 The press-formed product 1 was manufactured by cold press-forming the above metal plate according to the procedure shown in Figures 6(a) to (c). An intermediate formed product 1' was manufactured by performing flat trimming (Figure 6(b)). The minor angle Wθ1 between the top plate portion 11' and the vertical wall portion 12' in the intermediate formed product 1' was set to 90°. Next, as shown in Figure 6(c), the vertical wall portion 12' of the intermediate formed product 1' was re-formed (flanged down) to manufacture the press-formed product 1, which is the final formed product. The minor angle Wθ0 between the top plate portion 11 and the vertical wall portion 12, the length L0 of the cross section (cross section perpendicular to the longitudinal direction) of the vertical wall portion 12, and the curvature radius R0 of the curved portion 12a were the same as in Comparative Example 1. The cross section (cross section perpendicular to the longitudinal direction) of the vertical wall portion 12' of the intermediate formed product 1' had a length of 50.0 mm, a radius of curvature R1 of 162 mm, and a length of the flange portion 14' of 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 sheet thickness reduction rate was also a small value of 7.2%.

[0051] (4. Comparative Example 3) The press-formed product 200 was manufactured by cold press-forming the above metal plate according to the procedure shown in Figures 7 and 8. An intermediate molded product 200' was manufactured by performing flat trimming (Figure 7). The minor angle Wθ1 between the top plate portion 210' and the vertical wall portion 220' of the intermediate molded product 200' was made to match the minor angle Wθ0 between the top plate portion 210 and the vertical wall portion 220 of the press-formed product 200. Next, as shown in Figures 7 and 8, the vertical wall portion 220' of the intermediate molded product 200' was re-formed (flanged down) to manufacture the press-formed product 200, which is the final molded product. The minor angle Wθ0 between the top plate portion 210 and the vertical wall portion 220 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. Then, the lower end portion 220b of the press-formed product 200 was observed. As a result, concerns about cracks were found in the lower end portion 220b. The sheet thickness reduction rate was also 12.3%.

[0052] 5. Example 2 The press-formed product 2 was produced by cold press-forming the above metal plate according to the procedure shown in Figures 9 and 10. An intermediate product 2' was produced by performing flat trimming (Figure 9). The minor angle Wθ1 between the top plate portion 21' and the vertical wall portion 22' in the intermediate product 2' was set to 90°. Next, as shown in Figures 9 and 10, the vertical wall portion 22' of the intermediate product 2' was reshaped (flanged down) to produce the press-formed product 2, which is the final product. The minor angle Wθ0 between the top plate portion 21 and the vertical wall portion 22, the length L0 of the cross section (cross section perpendicular to the longitudinal direction) of the vertical wall portion 22, and the curvature radius 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 product 2' was 67.5 mm, the curvature radius 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 sheet thickness reduction rate was 12.1, which was smaller than that of Comparative Example 3.

[0053] 6. Example 3 In Example 1, when manufacturing 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. In the above formula (2), A was 0.132, and the radius of curvature R0 was 174 mm, so 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 produced 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. [Industrial Applicability]

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

[0059] 1, 2 Press-molded products 11, 21 Top plate 12, 22 Vertical wall section 12a, 22a curved section 12b, 22b bottom end

Claims

1. A method for manufacturing a press-molded product by press-molding a metal plate, The vertical wall portion of the press-formed product has a curved portion curved in an arc shape in a plate thickness direction or a plate surface direction, One end of the vertical wall portion in the up-down direction is connected to the top plate portion of the press-formed product via a bent portion, The method for manufacturing the press-molded product includes: a step of forming a flange portion at the other end of the vertical wall portion in the up-down direction during molding of the vertical wall portion, and forming a minor angle formed by the top plate portion and the vertical wall portion in at least a part of the longitudinal direction of the vertical wall portion to be smaller than the minor angle formed by the top plate portion and the vertical wall portion in the final shape of the press-molded product, to obtain an intermediate molded product; and reshaping the vertical wall portion of the intermediate molded product, A method for manufacturing a press-molded product, characterized in that in the process of re-molding the vertical wall portion, the horizontal bending width of the lower end of the intermediate molded product is shorter than the horizontal bending width of the lower end of the intermediate molded product when the minor angle formed by the top plate portion and the vertical wall portion is approximately the same as the minor angle formed by the top plate portion and the vertical wall portion in the final shape of the press-molded product.

2. A method for manufacturing a press-molded product by press-molding a metal plate, The vertical wall portion of the press-formed product has a curved portion curved in an arc shape in a plate thickness direction or a plate surface direction, One end of the vertical wall portion in the up-down direction is connected to the top plate portion of the press-formed product via a bent portion, The method for manufacturing the press-molded product includes: a step of forming a flange portion at the other end of the vertical wall portion in the up-down direction during molding of the vertical wall portion, and forming a minor angle formed by the top plate portion and the vertical wall portion in at least a part of the longitudinal direction of the vertical wall portion to be smaller than the minor angle formed by the top plate portion and the vertical wall portion in the final shape of the press-molded product, to obtain an intermediate molded product; and reshaping the vertical wall portion of the intermediate molded product, A method for manufacturing a press-molded product, characterized in that in the process of re-molding the vertical wall portion, the vertical bending width of the lower end of the intermediate molded product is shorter than the vertical bending width of the lower end of the intermediate molded product when the minor angle formed by the top plate portion and the vertical wall portion is approximately the same as the minor angle formed by the top plate portion and the vertical wall portion in the final shape of the press-molded product.

3. In the step of remolding the vertical wall portion, The method for manufacturing a press-formed product according to claim 1 or 2, wherein the press-formed product is formed so that a surface including the flange portion and a surface including the vertical wall portion are flush with each other.

4. 3. A method for manufacturing a press-formed product according to claim 1 or 2, characterized in that the following equations (1) and (2) are satisfied when 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. △R<A×R0 / (1+A) (1) A=(-1.2×10 －４ ×TS+0.25) (2)

5. 3. The method for manufacturing a press-formed product according to claim 1 or 2, characterized in that, when the length of the vertical wall portion in a cross section perpendicular to the longitudinal direction of the vertical wall portion of the press-formed product is L0 and the length of the vertical wall portion in a cross section perpendicular to the longitudinal direction of the vertical wall portion of the intermediate molded product is L1, the following formula (3) is satisfied: L1>L0×0.5 (3)

6. 3. The method for manufacturing a press-formed product according to claim 1, wherein the metal plate is a steel plate having a tensile strength of 440 MPa or more.

7. The method for manufacturing a press-formed product according to claim 1 or 2, wherein the press forming is cold press forming.

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