Hat-shaped molded part manufacturing method and mold

Abstract

To suppress generation of cracking in a blank material (hat-shaped formed component) during press forming using drawing.SOLUTION: A method for manufacturing a hat-shaped formed component 1 includes: a blank step of obtaining a blank material 2 by cutting a material; a draw step of obtaining an intermediate product 3B by forming the blank material 2 using an upper die 12 and a lower die 11; and a trim step of removing unnecessary parts of the intermediate product 3B. The blank step forms an excessive material part 9 at a portion that is located in the vicinity of an extension part 8 in the blank material 2 and that is to be positioned outside of the product. The draw step forms the blank material 2, holding the excessive material part 9 between a preceding pad 16 of the upper die 12 and a punch 13 of the lower die 11.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a hat-shaped molded part and a mold. [Background technology]

[0002] Automobile bodies require high strength, and high-tensile steel plates (high-tensile materials) are used as materials. In recent years, even higher strength has been required, so ultra-high-tensile materials are also used as materials. These high-tensile and ultra-high-tensile materials have excellent deformation strength and fracture strength, but are known to be prone to cracking during press forming due to their low ductility.

[0003] For example, the front pillar lower section has a substantially uniform hat-shaped cross section in the longitudinal direction, and the lower end section has an L-shape when viewed from the side of the vehicle body. The lower end section of such a front pillar lower section has an open end face, and the open end face has an extension section that curves and extends from the longitudinal direction of the front pillar lower section to the lateral direction.

[0004] Patent Document 1 discloses a method for manufacturing a pressed product, which includes a bead forming step for forming a linear bead extending along one of the short edges in a plate-shaped ultra-high tensile steel having a tensile strength of 980 MPa or more, the plate having a pair of longitudinal edges facing each other and extending in the longitudinal direction, and a pair of short edges facing each other and extending in the short direction, and a step forming step for forming a step in the ultra-high tensile steel in which the bead has been formed, the step being separated by wall portions protruding in the same direction along a pair of lines, at least some of which are arranged facing each other. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-203214 Summary of the Invention [Problem to be solved by the invention]

[0006] In the method for manufacturing a pressed product disclosed in Patent Document 1, pressing is performed by bending, so the vertical wall portion of the hat-shaped formed part cannot be continuously formed, and for example, the vertical wall portion may be missing from the curved portion of the hat-shaped formed part. Therefore, if pressing is performed by drawing, it becomes possible to continuously form the vertical wall portion in the curved portion of the hat-shaped formed part.

[0007] When the flange portion of a hat-shaped formed part is restrained by a blank holder and die and drawing is performed using a punch shaped like the product, the hat-shaped cross section (see the cross section along line AA in Figure 1D) has a balanced shape, allowing for balanced forming. However, in the cross section passing through the open end face (see the cross section along line BB in Figure 1D), the longitudinal end portion including the open end face is free and unconstrained, so the material is strongly pulled toward the blank holder (the flange portion side of the hat-shaped formed part) during drawing. As a result, a tensile force acts on the longitudinal end portion including the open end face of the hat-shaped formed part, which can cause cracks to form in the open end face.

[0008] Therefore, an object of the present invention is to suppress the occurrence of cracks in a blank material (a hat-shaped formed part) during press forming by drawing. [Means for solving the problem]

[0009] A method for manufacturing a hat-shaped formed part according to one aspect of the present invention is a method for manufacturing a hat-shaped formed part including a central top plate portion, a pair of vertical wall portions connected to the central top plate portion, and flange portions connected to each of the pair of vertical wall portions. The manufacturing method includes a blanking process in which a material is cut to obtain a blank, a drawing process in which the blank is formed into an intermediate product using an upper mold having a die and a leading pad and a lower mold having a punch and a blank holder, and a trimming process in which an unnecessary portion of the intermediate product is removed. At least one of a pair of longitudinal end portions of the hat-shaped formed part has an open end face, and the longitudinal end portion having the open end face has an extension portion that curves and extends from the longitudinal direction to the lateral direction of the hat-shaped formed part. In the blanking process, an excess material portion is formed in the blank near the extension portion but outside the product, and in the drawing process, the excess material portion is clamped between the leading pad and the punch to form the blank.

[0010] A mold according to one aspect of the present invention is a mold for press-forming a blank to produce a hat-shaped formed part including a central top plate portion, a pair of vertical wall portions connected to the central top plate portion, and flange portions connected to each of the pair of vertical wall portions. The mold includes an upper mold having a die and a leading pad, and a lower mold having a punch and a blank holder. At least one of a pair of longitudinal end portions of the hat-shaped formed part has an open end face, and the longitudinal end portion having the open end face has an extension portion that curves and extends from the longitudinal direction to the lateral direction of the hat-shaped formed part. The leading pad and punch are configured to clamp an excess material portion formed in a portion of the blank near the extension portion and outside the product, thereby forming the blank. [Effects of the Invention]

[0011] According to the method and mold for manufacturing a hat-shaped formed part according to one embodiment of the present invention, it is possible to suppress the occurrence of cracks in a blank material (hat-shaped formed part) during press forming by drawing. [Brief explanation of the drawings]

[0012] [Figure 1A] FIG. 10 is an explanatory diagram of a blanking step in the method for manufacturing a hat-shaped molded part according to one embodiment. [Figure 1B] FIG. 4 is an explanatory view of a first drawing step in the method for manufacturing a hat-shaped molded part according to one embodiment. [Figure 1C] FIG. 10 is an explanatory view of a second drawing step in the method for manufacturing a hat-shaped molded part according to one embodiment. [Figure 1D] 10A and 10B are explanatory diagrams of a trimming step in a method for manufacturing a hat-shaped molded part according to one embodiment. [Figure 2A] FIG. 2 is a schematic plan view of a lower mold of a mold according to one embodiment, viewed from above. [Figure 2B] FIG. 2 is a schematic bottom view of an upper mold of a mold according to one embodiment, viewed from below. [Figure 3] FIG. 2B is a cross-sectional view taken along line CC in FIG. 2A. [Figure 4] 1D is an enlarged view of a main part showing the positional relationship between the material and the mold in FIG. 1C. FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line DD in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0014] A method for producing a hat-shaped molded part 1 (see FIG. 1D) having a hat-shaped cross section and a mold 10 (see FIG. 3) used for press-molding the hat-shaped molded part 1 will be described below as an example.

[0015] [Applicable products] The hat-shaped molded part 1 shown in FIG. 1D is called a front pillar lower, which is a part that constitutes part of the front pillar of an automobile, and is generally made of high-tensile steel plate or the like.

[0016] The hat-shaped molded part 1 has a hat-shaped cross section and extends essentially in one direction (the vertical direction in FIG. 1D). This hat-shaped molded part 1 is configured to include a central top plate portion 4, a pair of vertical wall portions 5, 5 connected to the central top plate portion 4, and flange portions 6 connected to each of the pair of vertical wall portions 5, 5. The central top plate portion 4 and the flange portions 6 are connected by the vertical wall portions 5, and are formed so as to be generally parallel to each other. The vertical wall portions 5 and the flange portions 6 are not formed at the lower end of the hat-shaped molded part 1, and an open end surface 7 (so-called open end) is formed.

[0017] The lower end of the hat-shaped molded part 1 is formed with an extension portion 8 that curves and extends from the longitudinal direction (up-down direction) of the hat-shaped molded part 1 to the lateral direction (left-right direction). In this embodiment, the extension portion 8 is formed on one of the left and right ends of the hat-shaped molded part 1 for joining with a mating part, and the lower end of the hat-shaped molded part 1 is formed in a substantially L-shape. Therefore, the flange portion 6 on one of the left and right ends of the hat-shaped molded part 1 is gently curved in an R-shape until it is approximately perpendicular to the longitudinal direction of the hat-shaped molded part 1. Similar to the flange portion 6, the vertical wall portion 5 and the central top plate portion 4 are also gently curved in an R-shape until they are approximately perpendicular to the longitudinal direction of the hat-shaped molded part 1.

[0018] In the hat-shaped cross section (see the cross section along line AA in FIG. 1D ) of the hat-shaped molded part 1 according to this embodiment, the vertical wall portion 5 and the flange portion 6 are arranged on both sides of the central top plate portion 4, resulting in a balanced shape. However, in the cross section (see the cross section along line BB in FIG. 1D ) passing through the open end face 7, the vertical wall portion 5 and the flange portion 6 are arranged only on one side of the central top plate portion 4 that constitutes the extension portion 8.

[0019] In this embodiment, the extension portion 8 is formed at one of the left and right ends of the hat-shaped molded part 1, and as described above, the lower end of the hat-shaped molded part 1 is formed in a substantially L-shape. However, this is not limited to this, and the extension portion 8 may be formed at both the left and right ends of the hat-shaped molded part 1, and the longitudinal end of the hat-shaped molded part 1 may be formed in a substantially T-shape (for example, the lower part of a center pillar).

[0020] [Processing process] The processing steps for the hat-shaped molded part 1 in this embodiment are composed of (i) a blanking step, (ii) a first drawing step (first drawing process), (iii) a second drawing step (second drawing process), and (iv) a trimming step.

[0021] (i) The blanking process is a process in which material is adjusted to an appropriate size and shape to obtain a blank piece 2 (see FIG. 1A) for the subsequent first and second drawing processes. Generally, the portion of the blank piece 2 that will not be the product is determined to be as small as possible, taking into account the yield of the material. However, in this embodiment, an excess material portion 9 is provided in the portion of the blank piece 2 that will not be the product, so that it bulges out significantly, and this excess material portion 9 can be clamped in the second drawing process.

[0022] (ii) The first draw step is a step for forming a portion of the vertical wall portion 5 to obtain an intermediate product 3A (see FIG. 1B) because if there is a large difference in the height of the vertical wall portion 5 in the longitudinal direction in the hat-shaped formed part 1 of the final product shape, it may be difficult to perform the drawing in the next step. This first draw step is the first of two steps in which drawing is performed, and is not an essential step.

[0023] (iii) The second draw process is a process in which the overall shape of the hat-shaped formed part 1 (the central top plate portion 4, the pair of vertical wall portions 5, 5, the pair of flange portions 6, 6, and the extension portion 8) is formed by drawing to obtain an intermediate product 3B (see FIG. 1C). This second draw process is the most distinctive process in the processing of the hat-shaped formed part 1 according to this embodiment, and its details will be described later.

[0024] (iv) The trimming process is a process in which unnecessary portions of the drawn product (intermediate product 3B) are cut and removed to obtain the hat-shaped formed part 1 (see Figure 1D). Depending on the final product shape of the hat-shaped formed part 1, hole processing may also be performed at the same time. In this trimming process, excess material 9 that was provided in the part of the blank piece 2 outside the product in the blanking process is cut and removed. Furthermore, if the trimming process cannot be performed in one step, it may be performed in multiple steps, and in practice it is performed in two steps.

[0025] [Details of the second drawing process] The most distinctive step in the processing steps for the hat-shaped formed part 1 according to this embodiment is the second draw step, and the details of this second draw step will be described below. In this second draw step, drawing is performed using a die 10 as a drawing die shown in Figures 2A, 2B, and 3. In Figures 2A and 2B, the front side of the die 10 is indicated by arrow F, and the back side of the die 10 is indicated by arrow R.

[0026] [Mold details] The die 10 includes a lower die 11 and an upper die 12. The lower die 11 includes a punch 13 for forming the overall shape of the hat-shaped formed part 1 and a blank holder 14 for constraining the material. The blank holder 14 is connected to the lower die 11 by a die cushion mechanism (not shown) and moves up and down in conjunction with the movement of the die 15 of the upper die 12. Meanwhile, the upper die 12 includes a die 15 that primarily faces the blank holder 14 and a leading pad 16 that also forms the central top plate portion 4 of the hat-shaped formed part 1. The leading pad 16 is connected to the upper die 12 by a spring mechanism 17 or the like and moves up and down in conjunction with the movement of the upper die 12 body (die 15). Furthermore, the leading pad 16 is not positioned in a location corresponding to the entire central top plate portion 4 of the hat-shaped formed part 1, but only in a location corresponding to the approximately L-shaped extension portion 8 at the lower end (see FIGS. 2B and 4).

[0027] The leading pad 16 and punch 13 are configured to clamp the aforementioned excess material portion 9 and perform drawing forming, and these leading pad 16 and punch 13 are each provided with step portions 16a, 13a extending approximately parallel to the short side direction (left-right direction) of the hat-shaped formed part 1.

[0028] [Details of drawing] (i) The material (intermediate product 3A) is clamped between the die 15 and the blank holder 14, and the punch 13 is protruded into the material to form the material into the desired shape. In this embodiment, while the material is clamped between the die 15 and the blank holder 14, the central top plate portion 4 corresponding to the approximately L-shaped extension portion 8 is clamped between the punch 13 and the preceding pad 16, and further, the excess material portion 9 on the outside of the central top plate portion 4 is similarly clamped between the punch 13 and the preceding pad 16.

[0029] (ii) When the material is constrained by the die 15 and blank holder 14, the die 15 of the upper mold 12 descends, causing the punch 13 to protrude relatively into the material. As a result, a hat-shaped formed part 1 (intermediate product 3B) having a hat cross section is formed. During this drawing, the portion of the material sandwiched between the punch 13 and the leading pad 16 (such as the excess material portion 9) is strongly constrained by the constraining force of the spring mechanism 17 above the leading pad 16, restricting the movement of the constrained portion of the material (such as the excess material portion 9) (see Figure 5). Therefore, the material constituting the vertical wall portion 5 is supplied from portion E (see Figure 4). In particular, because the material is constrained over a wide area by the excess material portion 9 outside the product, which was created during the blanking process, a strong constraining force is generated, and as the punch 13 protrudes, material is supplied from the portion E side (the flange portion 6 side), forming the vertical wall portion 5.

[0030] (iii) Furthermore, the leading pad 16 and the punch 13 are provided with step portions 16a, 13a, respectively, that extend substantially parallel to the short side (left-right direction) of the hat-shaped formed part 1. Therefore, these step portions 16a, 13a also generate a strong restraining force, and it is possible to prevent the material from being pulled toward portion E (the flange portion 6 side) when the punch 13 protrudes. As shown in Fig. 1C, a step portion 9a is formed by the step portions 16a, 13a in the excess material portion 9 of the material (intermediate product 3B) after drawing, but the excess material portion 9 including this step portion 9a is removed in the trimming process described above.

[0031] [Actions and effects] The effects of this embodiment will be described below.

[0032] (1) The manufacturing method for the hat-shaped formed part 1 according to this embodiment is a method for manufacturing a hat-shaped formed part 1 including a central top plate portion 4, a pair of vertical wall portions 5, 5 connected to the central top plate portion 4, and flange portions 6 connected to each of the pair of vertical wall portions 5, 5. The manufacturing method includes a blanking step of cutting a material to obtain a blank piece 2, a drawing step of forming the blank piece 2 using an upper mold 12 having a die 15 and a leading pad 16 and a lower mold 11 having a punch 13 and a blank holder 14 to obtain an intermediate product 3B, and a trimming step of removing unnecessary portions of the intermediate product 3B. At least one of a pair of longitudinal end portions of the hat-shaped formed part 1 has an open end surface 7, and the longitudinal end portion having the open end surface 7 has an extension portion 8 that curves and extends from the longitudinal direction of the hat-shaped formed part 1 to the lateral direction. In the blanking process, a surplus material portion 9 is formed in the blank material 2 near the extension portion 8 but outside the product, and in the drawing process, the surplus material portion 9 is clamped between the leading pad 16 and the punch 13 to form the blank material 2.

[0033] An excess material portion 9 is provided on the outside of the product end of the material (blank material 2 after the blanking process has been completed), and during drawing, the central top plate portion 4 and excess material portion 9 at the product end are restrained by the preceding pad 16 and die 15. This makes it possible to prevent the material of the central top plate portion 4 from moving toward the flange portion 6, and to prevent cracks from occurring at the product end during the drawing process.

[0034] Since the excess material portion 9 is provided on the outside of the product end of the material (blank piece 2 after the blanking process has been completed), the tensile stress generated at the product end can be dispersed, and the occurrence of cracks can be suppressed.

[0035] (2) The leading pad 16 and punch 13 that clamp the excess material portion 9 in the drawing process are provided with stepped portions 16a, 13a that extend substantially parallel to the short side direction (left-right direction) of the hat-shaped formed part 1, respectively.

[0036] The excess material portion 9 is sandwiched between the leading pad 16 and the punch 13, and steps 16a, 13a are provided on the sandwiching leading pad 16 and punch 13. Therefore, these steps 16a, 13a also generate a restraining force, which can prevent the material of the central top plate portion 4 at the end of the product from moving toward the flange portion 6, and can prevent cracks from occurring at the end of the product during the drawing process.

[0037] (3) In the drawing process, the central top plate portion 4 forming part of the extension portion 8 is sandwiched together with the excess material portion 9 between the leading pad 16 and the punch 13 to form the blank material 2.

[0038] An excess material portion 9 is provided on the outside of the product end of the material (blank material 2 after the blanking process has been completed), and during drawing, the central top plate portion 4 and excess material portion 9 at the product end are restrained by the preceding pad 16 and die 15. This makes it possible to prevent the material of the central top plate portion 4 from moving toward the flange portion 6, and to prevent cracks from occurring at the product end during the drawing process.

[0039] (4) The unnecessary parts removed from the intermediate product 3B in the trimming process include the excess material part 9.

[0040] In the trimming process, unnecessary portions (portions outside the product) of the intermediate product 3B are cut and removed, thereby making it possible to improve the product quality of the hat-shaped molded part 1.

[0041] (5) The mold 10 according to this embodiment is used to press-form a blank 2 to produce a hat-shaped formed part 1 including a central top plate portion 4, a pair of vertical wall portions 5, 5 connected to the central top plate portion 4, and flange portions 6 connected to each of the pair of vertical wall portions 5, 5. The mold 10 includes an upper mold 12 having a die 15 and a leading pad 16, and a lower mold 11 having a punch 13 and a blank holder 14. At least one of a pair of longitudinal end portions of the hat-shaped formed part 1 has an open end face 7, and the longitudinal end portion having the open end face 7 has an extension portion 8 that curves and extends from the longitudinal direction to the lateral direction of the hat-shaped formed part 1. The leading pad 16 and punch 13 are configured to form the blank 2 by clamping an excess material portion 9 formed in a portion of the blank 2 near the extension portion 8 but outside the product.

[0042] An excess material portion 9 is provided on the outside of the product end of the material (blank material 2 after the blanking process has been completed), and during drawing, the central top plate portion 4 and excess material portion 9 at the product end are restrained by the preceding pad 16 and die 15. This makes it possible to prevent the material of the central top plate portion 4 from moving toward the flange portion 6, and to prevent cracks from occurring at the product end during the drawing process.

[0043] Since the excess material portion 9 is provided on the outside of the product end of the material (blank piece 2 after the blanking process has been completed), the tensile stress generated at the product end can be dispersed, and the occurrence of cracks can be suppressed.

[0044] (6) The leading pad 16 and punch 13 that hold the excess material portion 9 are provided with stepped portions 16a, 13a that extend substantially parallel to the short side direction (left-right direction) of the hat-shaped formed part 1, respectively.

[0045] The excess material portion 9 is sandwiched between the leading pad 16 and the punch 13, and steps 16a, 13a are provided on the sandwiching leading pad 16 and punch 13. Therefore, these steps 16a, 13a also generate a restraining force, which can prevent the material of the central top plate portion 4 at the end of the product from moving toward the flange portion 6, and can prevent cracks from occurring at the end of the product during the drawing process.

[0046] Furthermore, according to the mold 10 of this embodiment, press forming can be performed using a general mold structure, such as a die 15, a leading pad 16, a punch 13, and a blank holder 14, and high-quality hat-shaped molded parts 1 can be produced without reducing productivity.

[0047] Furthermore, in this embodiment, the process is described using two steps, the first draw step and the second draw step, but as mentioned above, the same effect can be obtained even if the blank material 2 is processed using a single draw step.

[0048] The manufacturing method and mold for the hat-shaped molded part of the present invention have been described using the above-mentioned embodiment as an example, but they are not limited to this embodiment and various other embodiments can be adopted within the scope of the gist of the present invention. [Explanation of symbols]

[0049] 1 Hat-shaped molding part (front pillar lower) 2 Blank material (material) 3B Intermediate product 4 Central top plate section 5 Vertical wall section 6 Flange 7 End face 8 Extension 9 Surplus material section 10. Mold 11 Lower mold 12 Upper mold 13 Punch 13a Step 14 Blank holder 15 Die 16 Leading Pad 16a Step

Claims

1. A method for manufacturing a hat-shaped molded part including a central top plate portion, a pair of vertical wall portions connected to the central top plate portion, and flange portions connected to each of the pair of vertical wall portions, a blanking step of cutting the material to obtain a blank; a drawing step of forming the blank material into an intermediate product using an upper mold having a die and a leading pad and a lower mold having a punch and a blank holder; a trimming step of removing unnecessary portions of the intermediate product, At least one of the pair of longitudinal end portions of the hat-shaped molded part has an open end surface, and the longitudinal end portion having the open end surface has an extension portion that curves and extends from the longitudinal direction of the hat-shaped molded part to the lateral direction, In the blanking step, an excess material portion is formed in the blank piece near the extension portion and outside the product, In the drawing step, the excess material portion is sandwiched between the preceding pad and the punch, and the flange portion is sandwiched between the die and the blank holder to form the blank material. Manufacturing method for hat-shaped molded parts.

2. the leading pad and the punch that sandwich the excess material portion in the drawing step are each provided with a stepped portion extending substantially parallel to the short-side direction; The method for manufacturing the hat-shaped molded part according to claim 1 .

3. In the drawing step, the central top plate portion forming a part of the extension portion is sandwiched together with the excess material portion between the leading pad and the punch to form the blank material. The method for manufacturing the hat-shaped molded part according to claim 1 or 2.

4. The unnecessary portion removed from the intermediate product in the trimming step includes the excess material portion. The method for manufacturing the hat-shaped molded part according to any one of claims 1 to 3.

5. A mold for producing a hat-shaped molded part by press-molding a blank material, the mold comprising: a central top plate portion; a pair of vertical wall portions connected to the central top plate portion; and flange portions connected to each of the pair of vertical wall portions, an upper mold having a die and a leading pad; a lower die having a punch and a blank holder; At least one of the pair of longitudinal end portions of the hat-shaped molded part has an open end surface, and the longitudinal end portion having the open end surface has an extension portion that curves and extends from the longitudinal direction of the hat-shaped molded part to the lateral direction, The preceding pad and the punch are configured to sandwich an excess material portion formed in a portion of the blank material that is near the extension portion and outside the product, and the die and the blank holder are configured to sandwich the flange portion to form the blank material. Mold.

6. the preceding pad and the punch that sandwich the excess material portion are each provided with a stepped portion extending substantially parallel to the short-side direction; The mold according to claim 5.

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