Method for producing molded article

Abstract

To provide a technique for suppressing fracture of a tailored blank when forming a press-formed product having a weld zone in a flange part.SOLUTION: The manufacturing method includes bringing the tailored blank into a sandwiched state in which the flange equivalent portion is sandwiched between the first die and the holding portion, and bringing the first die and the second die close to each other in the sandwiched state to press the tailored blank with the first die and the second die to form the top plate part, the vertical wall parts, and the flange parts. The holding part is a member capable of holding the flange equivalent portion in cooperation with the first die. In the sandwiched state, the first die and the holding part sandwich the flange equivalent portion such that the welded part is movable toward the top plate equivalent portion.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a molded article. [Background technology]

[0002] The following patent document describes a method for press-forming a tailored blank. This press-forming method forms a deep press-formed product having a top plate portion, vertical wall portions, and flange portions. Specifically, deep drawing is performed by lowering a punch and a counter punch while sandwiching the portion of the tailored blank where the top plate portion is to be formed. The welded portion of the tailored blank, where different steel plates are welded, is located at a position sandwiched between the punch and counter punch, i.e., at the top plate portion. At this time, press forming is performed with the punch and counter punch sandwiching the top plate portion so as to suppress in-plane displacement of the material in the top plate portion. This prevents the weld from shifting from the desired position. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-142341 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the weld of a tailored blank is located in the flange, and deep drawing is performed while the movement of the weld is excessively restricted, the tailored blank may break. That is, if the in-plane displacement of the material in the flange is excessively restricted, when the top plate is formed by deep drawing, it becomes difficult for material to flow from the flange to the top plate. Therefore, there is a possibility that a tailored blank with excessively restricted material movement may break.

[0005] One aspect of the present disclosure provides a technique for suppressing fracture of a tailored blank when forming a press-formed product having a welded portion in a flange portion. [Means for solving the problem]

[0006] One aspect of the present disclosure is a method for manufacturing a formed product by pressing a tailored blank to obtain a formed product. The tailored blank is a steel plate obtained by welding a first steel plate and a second steel plate having a thickness and / or strength different from that of the first steel plate. The tailored blank has a welded portion formed by welding an end face of the first steel plate to an end face of the second steel plate. The formed product comprises a top plate portion, a vertical wall portion, and a flange portion. The vertical wall portion is a plate-shaped portion erected from an end of the top plate portion so as to surround the top plate portion. The flange portion is a plate-shaped portion extending from the vertical wall portion in a direction intersecting the vertical wall portion, and is disposed so as to surround the top plate portion in a plan view perpendicular to the top plate portion. The tailored blank comprises a portion corresponding to the top plate, a portion corresponding to the vertical wall, and a portion corresponding to the flange. The top plate corresponding portion represents a portion corresponding to the top plate portion. The vertical wall corresponding portion represents a portion corresponding to the vertical wall portion. The flange-equivalent portion represents a portion corresponding to the flange portion. The top plate-equivalent portion is disposed on the first steel plate. The weld portion is disposed on the flange-equivalent portion. The manufacturing method includes placing a tailored blank between a first mold and a second mold that are spaced apart, establishing a clamping state in which the flange-equivalent portion is clamped between the first mold and a holding portion, and, while in the clamping state, bringing the first mold and the second mold closer to each other to press the tailored blank with the first mold and the second mold to form the top plate portion, the vertical wall portion, and the flange portion. The holding portion is a member that is disposed between the first mold and the second mold and is capable of clamping the flange-equivalent portion in cooperation with the first mold. In the clamping state, the first mold and the holding portion clamp the flange-equivalent portion so that the weld portion can move toward the top plate-equivalent portion.

[0007] With this configuration, the welded portion can move toward the top plate portion, making it easier for material to flow from the flange portion toward the top plate portion. This prevents the first steel plate from becoming thinner. The welded portion can also move smoothly. This makes it possible to prevent fracture of the tailored blank when forming a press-formed product having a welded portion in the flange portion.

[0008] In one aspect of the present disclosure, the pressure applied by the holding portion to the tailored blank in the clamped state may be set to satisfy the following formula (Mathematical Expression 1).

[0009]

number

[0010] X: Pressure applied by the retaining portion to the tailored blank. Ts: Tensile strength of the first steel plate. A: Contact area between the retaining portion and the tailored blank before the tailored blank is pressed by the first and second dies.

[0011] With this configuration, the clamped state can be maintained without hindering the welded portion from moving toward the top plate portion, which makes it easier for material to flow from the flange portion toward the top plate portion.

[0012] In one embodiment of the present disclosure, the thickness of the first steel plate may be thinner than the thickness of the second steel plate. An adjustment member may be disposed between the first mold and the second mold for adjusting the distance between the tailored blank and the first mold in the clamped state. The adjustment member may adjust the distance between the tailored blank and the first mold in the clamped state to 5% or more and less than 20% of the thickness of the first steel plate. With this configuration, by creating a gap between the tailored blank and the first mold, the tailored blank does not come into excessive contact with the first mold and the holding portion in the clamped state. Therefore, the clamped state can be maintained without preventing the weld from moving toward the top plate portion. This makes it easier for material to flow from the flange portion toward the top plate portion.

[0013] In one aspect of the present disclosure, the amount of movement of the welded portion toward the top plate portion during forming may be designed in advance. The portion of the first mold and / or the holding portion that may come into contact with the welded portion in the clamped state may have a hardness higher than that of the welded portion. This configuration can prevent the first mold and / or the holding portion from being scraped or chipped, even if the welded portion moves through the movement area while contacting the first mold and / or the holding portion. Therefore, deformation of the first mold and / or the holding portion can be prevented, allowing a stable clamped state to be maintained.

[0014] In one aspect of the present disclosure, the top plate-equivalent portion may include an end portion of the tailored blank on a first direction side in a plan view perpendicular to the thickness direction of the tailored blank. The top plate-equivalent portion may be disposed on a portion of the first direction side. The welded portion may extend from an end portion on a second direction side opposite the end portion on the first direction side toward the first direction side so as to avoid the top plate-equivalent portion. With this configuration, the distance from the top plate-equivalent portion to the welded portion differs between the first direction side, where the deformation amount of the blank is relatively large, and the second direction side, where the deformation amount of the blank is relatively small. In other words, the welded portion is disposed on the blank taking into account the amount of movement of the welded portion during press working. Therefore, when the press-formed product is completed, the welded portion can be provided at a desired position. Specifically, a press-formed product can be obtained in which the welded portion extends approximately parallel to the ridge line between the vertical wall portion and the flange portion. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic perspective view of a part of a press-formed product. [Figure 2] Fig. 2A is a schematic plan view of a press-formed product, and Fig. 2B is a schematic plan view of a tailored blank. [Figure 3] Fig. 3A is a cross-sectional view taken along line IIIA-IIIA in Fig. 2A, and Fig. 3B is a cross-sectional view taken along line IIIB-IIIB in Fig. 2A. [Figure 4]4A and 4B are schematic cross-sectional views of a weld bead having a shape that bulges upward and downward, respectively. [Figure 5] FIG. 5 is a schematic cross-sectional view of a part of a press-forming device. [Figure 6] Fig. 6A is a VIA-VIA cross-sectional view of Fig. 6B. Fig. 6B is a plan view of the press forming apparatus in the clamping process. Fig. 6C is a VIC-VIC cross-sectional view of Fig. 6D. Fig. 6D is a plan view of the press forming apparatus during pressing. Fig. 6E is a VIE-VIE cross-sectional view of Fig. 6F. Fig. 6F is a plan view of the press forming apparatus when pressing is completed. Note that Figs. 6B, 6D, and 6F are shown in a see-through manner, with the die and tailored blank visible. [Figure 7] FIG. 7 is a flowchart illustrating a method for manufacturing a press-formed product. [Figure 8] FIG. 8 is a schematic diagram for explaining the movement area. [Figure 9] FIG. 9 is a schematic cross-sectional view of a press-forming apparatus according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. [1. First embodiment] [1-1. Press-molded products] The press-formed product 1 shown in FIGS. 1 and 2A is formed by press-forming a tailored blank 10 shown in FIG. 2B. Hereinafter, when describing the press-formed product 1 and the tailored blank 10, the plate thickness direction of the press-formed product 1 and the tailored blank 10 will be referred to as the up-down direction. Furthermore, the direction in which a second steel plate 12 (described later) is arranged relative to a first steel plate 11 (described later) will be referred to as the left-right direction. Furthermore, the longitudinal direction of the second steel plate 12 will be referred to as the front-rear direction. Furthermore, the direction from the second steel plate 12 toward the first steel plate 11 will sometimes be referred to as the inward direction, and the direction from the first steel plate 11 toward the second steel plate 12 will sometimes be referred to as the outward direction. Note that these directions are defined for the sake of convenience of description and do not limit the manner in which the press-formed product 1 can be used.

[0017] As an example, the press-formed product 1 is used as a rear floor pan to be mounted on a vehicle. Note that FIG. 1 is a diagram showing the right half of the press-formed product 1, but the left half of the press-formed product 1 (not shown) is configured bilaterally symmetrical to the right half of the press-formed product 1. The press-formed product 1 may be a component other than a rear floor pan of a vehicle, such as a rocker outer panel or other floor pan. The press-formed product 1 may also be a part to be mounted on something other than a vehicle.

[0018] The press-molded product 1 includes a top plate portion 2, a vertical wall portion 3, and a flange portion 4. The top plate portion 2 is a plate-like portion that extends in the same plane. More specifically, the top plate portion 2 has a substantially rectangular shape in a plan view. The top plate portion 2 may have any irregularities. For example, when viewed from below, the top plate portion 2 may have a portion that is recessed upward, or when viewed from above, may have a portion that is recessed downward.

[0019] The vertical wall portion 3 is a plate-shaped portion erected from the end of the top plate portion 2 so as to surround the top plate portion 2. More specifically, the vertical wall portion 3 is a wall extending downward from the front edge of the top plate portion 2, the left edge of the top plate portion 2, and the right edge of the top plate portion 2. In other words, the vertical wall portion 3 is a wall surrounding the top plate portion 2 from three directions. That is, the top plate portion 2 and the vertical wall portion 3 of the press-molded product 1 have a bag-shaped outer shape. Note that a bag shape is a shape that can accommodate objects in the space and has an opening for putting in and taking out objects. In the press-molded product 1, objects can be stored in the space surrounded by the top plate portion 2 and the vertical wall portion 3. In addition, objects can be put in and taken out through an opening formed on the opposite side of the vertical wall portion 3 from the top plate portion 2. In this embodiment, the vertical wall portion 3 extends from the bottom to the top side so as to be slightly inclined toward the top plate portion 2. That is, the cross section of the top panel 2 and the vertical wall 3 perpendicular to the front-rear direction is trapezoidal as shown in Fig. 3A. The cross section of the vertical wall 3 perpendicular to the up-down direction is substantially U-shaped.

[0020] The flange portion 4 is a plate-like portion extending from the vertical wall portion 3 in a direction intersecting with the vertical wall portion 3, and is a portion arranged so as to surround the top plate portion 2 in a plan view perpendicular to the top plate portion 2. More specifically, the flange portion 4 is a plate extending from the edge of the vertical wall portion 3 on the side opposite the top plate portion 2, in a direction away from the top plate portion 2, and approximately parallel to the top plate portion 2. In other words, the flange portion 4 is a plate that surrounds the top plate portion 2 from three directions in a plan view.

[0021] The size of the press-formed product 1 is, for example, approximately 1500 mm in width in the left-right direction, approximately 700 mm in depth in the front-rear direction, and approximately 180 mm in depth in the up-down direction. The size of the bag-shaped portion of the press-formed product 1 is, for example, approximately 600 mm in width in the left-right direction, approximately 200 mm in depth in the front-rear direction, and approximately 180 mm in depth in the up-down direction.

[0022] 2A, the press-formed product 1 includes a first steel plate 11, a second steel plate 12, a third steel plate 13, a first welded portion 14, and a second welded portion 15. Each of these portions will be described in detail later.

[0023] [1-2. Tailored Blank] The tailored blank 10 shown in FIG. 2B is a steel plate formed by welding together a first steel plate 11, two second steel plates 12, and two third steel plates 13. In other words, the tailored blank 10 is a blank formed by joining the first steel plate 11, two second steel plates 12, and two third steel plates 13 together by welding. The two second steel plates 12 are arranged on both the left and right sides of the first steel plate 11 so as to sandwich the first steel plate 11 therebetween. The two third steel plates 13 are arranged so as to sandwich the first steel plate 11 and the second steel plate 12 therebetween. The tailored blank 10 is configured symmetrically.

[0024] The first steel plate 11 is a substantially trapezoidal plate-like member. More specifically, the rear end is longer than the front end, and the width in the left-right direction decreases from the rear side to the front side. As an example, the thickness of the first steel plate 11 is 0.6 mm, and the tensile strength of the first steel plate 11 is 270 MPa.

[0025] The second steel plate 12 is a plate-like member having a length. More specifically, the second steel plate 12 has a substantially rectangular shape and an outer shape that is long in the front-to-rear direction. The second steel plate 12 is a steel plate having a thickness and / or strength different from that of the first steel plate 11. In this embodiment, the second steel plate 12 is a steel plate having a thickness greater than that of the first steel plate 11 and a tensile strength higher than that of the first steel plate 11. The second steel plate 12 is a high-tensile steel material. As an example, the thickness of the second steel plate 12 is 1.0 mm, and the tensile strength of the second steel plate 12 is 780 MPa. The strength ratio between the first steel plate 11 and the second steel plate 12 is 4.8. The strength ratio is calculated by multiplying the tensile strength and thickness of the second steel plate 12 and dividing it by the tensile strength and thickness of the first steel plate 11.

[0026] The third steel plate 13 is a plate-like member having an outer shape that is long in the front-rear direction. The third steel plate 13 has a shape in which the center in the front-rear direction bulges outward slightly. The third steel plate 13 is a steel plate having a thickness and / or strength different from those of the first steel plate 11 and the second steel plate 12. In this embodiment, the third steel plate 13 is a steel plate having a thickness greater than that of the first steel plate 11. The third steel plate 13 is also a steel plate having a thickness smaller than that of the second steel plate 12 and a lower tensile strength. As an example, the thickness of the third steel plate 13 is 0.65 mm, and the tensile strength of the third steel plate 13 is 270 MPa.

[0027] The tailored blank 10 has a first welded portion 14 formed at a location where the end face of the first steel plate 11 and the end face of the second steel plate 12 are welded together. More specifically, the first welded portion 14 is a weld bead formed by welding along the edge of the first steel plate 11 facing the second steel plate 12, and the edge of the second steel plate 12 facing the first steel plate 11. In other words, the tailored blank 10 has a weld line formed along the edge of the first steel plate 11 facing the second steel plate 12, and the edge of the second steel plate 12 facing the first steel plate 11.

[0028] Furthermore, the tailored blank 10 is formed with a second welded portion 15, which is a portion where the end face of the second steel plate 12 and the end face of the third steel plate 13 are welded together. More specifically, the second welded portion 15 is a weld bead formed by welding along the edge of the second steel plate 12 facing the third steel plate 13, and the edge of the third steel plate 13 facing the second steel plate 12. In other words, the tailored blank 10 is formed with a weld line that runs along the edge of the second steel plate 12 facing the third steel plate 13, and the edge of the third steel plate 13 facing the second steel plate 12.

[0029] The first steel plate 11, the second steel plate 12, and the third steel plate 13, each having a different plate thickness, are joined together, but in this embodiment, the first steel plate 11, the second steel plate 12, and the third steel plate 13 are joined together so that the upper surfaces of the first steel plate 11, the second steel plate 12, and the third steel plate 13 are arranged in the same plane. The first steel plate 11, the second steel plate 12, and the third steel plate 13 may also be joined together so that the lower surfaces of the first steel plate 11, the second steel plate 12, and the third steel plate 13 are arranged in the same plane. However, due to the nature of the material, some unevenness exists on the surface of each steel plate. The "flush plane" does not necessarily mean a smooth plane.

[0030] The first welded portion 14 and the second welded portion 15 (i.e., weld beads) may be formed to protrude above the top surface of the tailored blank 10, as shown in FIG. 4A, or may be formed to protrude below the bottom surface of the tailored blank 10. The first welded portion 14 and the second welded portion 15 may be formed to be recessed on the bottom but protrude above, or as shown in FIG. 4B, may be formed to be recessed on the top but protrude below. Note that FIGS. 4A and 4B only illustrate the first welded portion 14. The difference in thickness between the first steel plate 11 and the second steel plate 12 is omitted from the illustration.

[0031] As shown in FIG. 2B, the tailored blank 10 includes a portion corresponding to a top plate 2A, a portion corresponding to a vertical wall 3A, and a portion corresponding to a flange 4A. The top plate corresponding portion 2A represents a portion corresponding to the top plate portion 2 of the press-formed product 1. In other words, the top plate corresponding portion 2A is a region in the tailored blank 10 where the top plate portion 2 is formed when the press-formed product 1 is formed. The top plate corresponding portion 2A is a substantially rectangular region.

[0032] The vertical wall equivalent portion 3A represents a portion corresponding to the vertical wall portion 3 of the press-formed product 1. In other words, the vertical wall equivalent portion 3A is a region in the tailored blank 10 where the vertical wall portion 3 is formed when the press-formed product 1 is formed. The vertical wall equivalent portion 3A is a substantially U-shaped region that surrounds the top plate equivalent portion 2A from three directions.

[0033] The flange equivalent portion 4A represents a portion corresponding to the flange portion 4 of the press-formed product 1. In other words, the flange equivalent portion 4A is the region of the tailored blank 10 where the flange portion 4 is formed when the press-formed product 1 is formed. The flange portion 4 is the region other than the top plate equivalent portion 2A and the vertical wall equivalent portion 3A.

[0034] The top plate equivalent portion 2A and the vertical wall equivalent portion 3A are arranged on the first steel plate 11. Specifically, in a plan view, the top plate equivalent portion 2A is arranged in a part of the rear side, including the rear end portion, of the tailored blank 10. More specifically, the top plate equivalent portion 2A and the vertical wall equivalent portion 3A are arranged in a region that is approximately in the center in the left-right direction and in a rear region in the front-to-rear direction.

[0035] The flange equivalent portions 4A are arranged on a part of the first steel plate 11, the second steel plate 12, and the third steel plate 13. Specifically, in a plan view, the flange equivalent portions 4A are arranged on the entire front side of the tailored blank 10, including the front end, and on the entire left and right sides, including the left and right end portions.

[0036] The first welded portion 14 and the second welded portion 15 are disposed in the flange-equivalent portion 4A. Specifically, the first welded portion 14 extends from the front end of the tailored blank 10 to the rear, avoiding the top plate-equivalent portion 2A. More specifically, the first welded portion 14 extends obliquely from the boundary between the vertical wall-equivalent portion 3A and the flange-equivalent portion 4A, which extends in the front-to-rear direction, to move away from the boundary as it moves from the front to the rear. The first welded portion 14 is disposed near the vertical wall-equivalent portion 3A. Specifically, in the right half of the tailored blank 10, the first welded portion 14 is disposed at a position approximately one-third of the distance from the boundary between the vertical wall-equivalent portion 3A and the flange-equivalent portion 4A, which extends in the front-to-rear direction, to the right edge of the flange-equivalent portion 4A. The second welded portion 15 extends substantially parallel to the first welded portion 14.

[0037] [1-3. Press forming equipment] The press-forming apparatus 100 shown in Fig. 5 is an apparatus for pressing a tailored blank 10 to obtain a press-formed product 1. Fig. 5 and Figs. 6A to 6F are views showing the right half of the press-forming apparatus 100, but the left half of the press-forming apparatus 100 (not shown) is configured symmetrically to the right half of the press-forming apparatus 100.

[0038] The press forming apparatus 100 includes a die 101, a punch 102, and a blank holder 103. The die 101 and the punch 102 are metal molds that are arranged to face each other in the vertical direction. In this embodiment, the die 101 is arranged at the top, and the punch 102 is arranged at the bottom. Furthermore, by moving the die 101 in the vertical direction, press forming is performed by the die 101 and the punch 102. The die 101 and the blank holder 103 are configured to be displaceable in the vertical direction by a drive mechanism (not shown).

[0039] The die 101 is disposed above the tailored blank 10 so as to cover the entire tailored blank 10. The punch 102 is disposed below the tailored blank 10. The die 101 and punch 102 each have a shape that follows the shape of the press-molded product 1. Specifically, the die 101 and punch 102 each have top plate forming portions 2C, 2D and vertical wall forming portions 3C, 3D. Each top plate forming portion 2C, 2D is a portion for forming the top plate portion 2. Each vertical wall forming portion 3C, 3D is a portion for forming the vertical wall portion 3. The die 101 has a shape that is concave upward in the center in the left-right direction. The punch 102 has a shape that protrudes upward.

[0040] The blank holder 103 is a member disposed opposite the die 101 and capable of clamping the flange equivalent portion 4A in cooperation with the die 101. As shown in FIG. 9, the blank holder 103 is disposed between the die 101 and the base of the punch 102. The blank holder 103 has a larger area than the flange equivalent portion 4A so that it can hold the entire lower surface of the flange equivalent portion 4A. A part of the first steel plate 11, the second steel plate 12, and the third steel plate 13 can be placed on the blank holder 103. In other words, the blank holder 103 is a member that extends to the front, right, and left from the boundary between the vertical wall equivalent portion 3A and the flange equivalent portion 4A.

[0041] Portions of the die 101 and the blank holder 103 that may come into contact with the first welded portion 14 and the second welded portion 15 in a clamped state described below are made of a material having a higher hardness than the first welded portion 14 and the second welded portion 15. In other words, portions of the die 101 and the blank holder 103 that face a moving region described below in a clamped state are made of a material having a higher hardness than the first welded portion 14 and the second welded portion 15. For example, portions of the die 101 and the blank holder 103 that face the moving region in a clamped state may be made of a material having a higher carbon content than the first welded portion 14 and the second welded portion 15.

[0042] [1-4. Manufacturing methods for press-molded products] 7, a manufacturing method of the press-formed product 1 will be described, in which a tailored blank 10 is pressed to obtain the press-formed product 1. The manufacturing method of the press-formed product 1 includes a blank manufacturing process S1, a first forming process S2, a trimming process S3, and a second forming process S4. The manufacturing method of the press-formed product 1 is performed in the order of the blank manufacturing process S1, the first forming process S2, the trimming process S3, and the second forming process S4.

[0043] In the blank manufacturing process S1, a tailored blank 10 is manufactured. Specifically, a first steel plate 11, a second steel plate 12, and a third steel plate 13 are welded together to manufacture the tailored blank 10. The shape of the tailored blank 10 is determined based on the amount of deformation of the tailored blank 10 in the press process described below. The amount of deformation of the tailored blank 10 can also be referred to as the amount of movement of the material of the tailored blank 10. For example, the amount of movement of the material of the tailored blank 10 is calculated by a simulator. In other words, the amount of movement of the first welded portion 14 and the second welded portion 15 toward the top plate equivalent portion 2A in the press process is designed in advance. That is, the first welded portion 14 and the second welded portion 15 move toward the top plate equivalent portion 2A through a movement region, which is a pre-designed region in the tailored blank 10. More specifically, in a region where the amount of deformation is relatively large as shown in Fig. 3A, the amount of movement of the first weld 14 and the second weld 15 is predicted to be greater than in a region where the amount of deformation is relatively small as shown in Fig. 3B. Specifically, in a region where a relatively large amount of material of the tailored blank 10 flows into the top plate portion 2 when the top plate portion 2 is formed, the amount of movement of the first weld 14 and the second weld 15 is predicted to be relatively greater. Therefore, in the blank manufacturing process S1, the steel plates are welded at positions of the first weld 14 and the second weld 15 in the tailored blank 10 that are predicted by back-calculating from the positions of the first weld 14 and the second weld 15 in the press-formed product 1, taking into account the amount of deformation of the tailored blank 10. The movement of the first weld 14 and the second weld 15 will be described in detail later.

[0044] The first forming step S2 is a step of obtaining an intermediate formed product by drawing the tailored blank 10 using the press forming apparatus 100. The first forming step S2 includes a positioning step, a clamping step, and a pressing step.

[0045] In the placement step, the tailored blank 10 is placed between the die 101 and punch 102, which are separated from each other. Specifically, the flange-equivalent portion 4A of the tailored blank 10 is placed on the upper surface of the blank holder 103.

[0046] In the clamping step, the die 101 descends, bringing the die 101 and the blank holder 103 relatively closer to each other, and the tailored blank 10 is fixed in a clamped state between the die 101 and the blank holder 103. More specifically, the die 101 transitions to a clamped state in which the flange equivalent portion 4A is clamped between the die 101 and the blank holder 103. In the clamped state, the die 101 and the blank holder 103 clamp the flange equivalent portion 4A so that the first welded portion 14 and the second welded portion 15 can move toward the top plate equivalent portion 2A.

[0047] In this embodiment, the pressure applied by the blank holder 103 to the tailored blank 10 in the clamped state is set to satisfy the following formula (Mathematical Formula 1).

[0048]

number

[0049] In Equation 1, X is the pressure applied by the blank holder 103 to the tailored blank 10. Ts is the tensile strength of the steel plate (the first steel plate 11 in this embodiment) having the lowest value obtained by multiplying the tensile strength by the plate thickness. A represents the contact area between the blank holder 103 and the tailored blank 10 before the tailored blank 10 is pressed by the die 101 and the punch 102. Note that the surface of the tailored blank 10 has some unevenness due to the nature of the material. Therefore, the tailored blank 10 does not necessarily come into close contact with the blank holder 103 over the entire surface. The contact area is not limited to the area where the blank holder 103 and the tailored blank 10 contact each other, but also includes the area where the blank holder 103 and the tailored blank 10 overlap in the vertical direction.

[0050] In the pressing process, the die 101 and punch 102 are brought close to each other while still sandwiched, and the tailored blank 10 is pressed by the die 101 and punch 102 to form the top plate portion 2, vertical wall portion 3, and flange portion 4. More specifically, while still sandwiched, the die 101 and blank holder 103 are lowered. When the die 101 and blank holder 103 reach the bottom dead center, the top plate portion 2 is formed in the portion of the tailored blank 10 sandwiched between the top plate forming portions 2C and 2D, and the vertical wall portion 3 is formed in the portion of the tailored blank 10 sandwiched between the vertical wall forming portions 3C and 3D. In addition, the flange portion 4 is formed in the portion of the tailored blank 10 sandwiched between the die 101 and the blank holder 103.

[0051] The trimming step S3 is a step for performing trimming on the intermediate molded product formed in the first molding step S2. In the trimming step S3, unnecessary portions are removed from the intermediate molded product. The second forming step S4 is a step for subjecting the intermediate formed product processed in the trimming step S3 to any processing, such as bending or forming holes.

[0052] Through the above steps S1 to S4, the press-formed product 1 is formed. [1-5. Movement of the first and second welded parts] From the time of transition to the clamped state until the press processing is completed, the first welded portion 14 and the second welded portion 15 are clamped between the die 101 and the blank holder 103 so as to move through a pre-designed movement area toward the top plate equivalent portion 2A.

[0053] As shown in FIG. 2B , in the tailored blank 10, the first welded portion 14 and the second welded portion 15 are the boundary between the vertical wall portion 3A and the flange portion 4A, and extend at an angle relative to the boundary extending in the front-to-rear direction. Note that "at an angle" means that the angle between the weld line and an imaginary line extending in the front-to-rear direction intersects with the boundary line at approximately 5 degrees or more. Meanwhile, as shown in FIG. 2A , in the press-formed product 1, the first welded portion 14 and the second welded portion 15 extend substantially parallel to the ridge line between the vertical wall portion 3 and the flange portion 4. More specifically, the first welded portion 14 and the second welded portion 15 extend substantially parallel to the ridge line between the vertical wall portion 3 and the flange portion 4, which extends in the front-to-rear direction. Specifically, the first welded portion 14 and the second welded portion 15 extend at an angle relative to the ridge line from the front end to a corner where a wall of the vertical wall portion 3 extending in the up-down and front-to-rear directions intersects with a wall extending in the up-down and left-to-right directions. The first welded portion 14 and the second welded portion 15 extend approximately parallel to the ridge line from the corner to the rear end. In other words, during press working, the material of the tailored blank 10 moves in a rotating manner starting from the corner toward the top plate equivalent portion 2A. In areas with relatively large deformation, i.e., areas rearward of the corner, the material of the tailored blank 10 moves in a rotating manner to a greater extent than in areas with relatively small deformation, i.e., areas forward of the corner.

[0054] The first welded portion 14 and the second welded portion 15 also move in a rotating manner from the corner toward the top plate-equivalent portion 2A. In other words, the angle formed by the first welded portion 14 and the ridge line between the vertical wall portion 3 and the flange portion 4 in the press-formed product 1 is smaller than the angle formed by the first welded portion 14 and the boundary between the vertical wall portion 3A and the flange portion 4A in the tailored blank 10. As a result, the first welded portion 14 and the ridge line become approximately parallel. Specifically, the angle formed by the first welded portion 14 and the ridge line between the vertical wall portion 3 and the flange portion 4 in the press-formed product 1 is less than approximately 5 degrees. As shown in FIG. 8 , the area surrounded by dashed line 14A (i.e., the first welded portion 14 before press working) and dashed line 14B (i.e., the first welded portion 14 after press working) is the movement area of ​​the first welded portion 14. The area surrounded by dashed line 15A (i.e., second welded portion 15 before press working) and dashed line 15B (i.e., second welded portion 15 after press working) is the movement area of ​​second welded portion 15. The movement area has a roughly triangular shape with its vertex at the height of the corner in the front-to-rear direction and its width in the left-to-right direction increasing toward the rear.

[0055] [1-6.Effects] According to the first embodiment described above in detail, the following effects can be obtained. (1a) In the above embodiment, in the clamped state, the die 101 and blank holder 103 clamp the flange-equivalent portion 4A so that the first welded portion 14 and the second welded portion 15 can move toward the top plate-equivalent portion 2A. Here, during press working, the top plate-equivalent portion 2A and the vertical wall-equivalent portion 3A undergo relatively large deformations, so the thickness of the first steel plate 11 becomes thinner than its original thickness. If the die 101 and blank holder 103 clamp the flange-equivalent portion 4A so as to excessively restrict the movement of the first welded portion 14 and the second welded portion 15, it becomes difficult for material to flow from the flange-equivalent portion 4A toward the top plate-equivalent portion 2A. Therefore, the first steel plate 11, which has become thinner, and the vicinity of the first welded portion 14 and the second welded portion 15, which are excessively restricted in movement, become more susceptible to fracture. However, with the above-described configuration, the first welded portion 14 and the second welded portion 15 can move toward the top plate-equivalent portion 2A, which makes it easier for material to flow from the flange-equivalent portion 4A toward the top plate-equivalent portion 2A. This makes it difficult for the thickness of the first steel plate 11 to become thin. Furthermore, the first welded portion 14 and the second welded portion 15 can also move smoothly. This makes it possible to prevent fracture of the tailored blank 10 when forming a press-formed product 1 having the first welded portion 14 and the second welded portion 15 on the flange portion 4.

[0056] If the tailored blank 10 is pressed without being clamped between the die 101 and the blank holder 103, an excessive amount of material will flow from the flange equivalent portion 4A toward the top plate equivalent portion 2A, making it more likely that wrinkles will occur in the press-formed product 1. However, with the above-described configuration, the die 101 and the blank holder 103 clamp the flange equivalent portion 4A, thereby preventing the excessive flow of material from the flange equivalent portion 4A toward the top plate equivalent portion 2A. This makes it possible to prevent wrinkles from occurring in the press-formed product 1.

[0057] (1b) In the above embodiment, the pressure applied by the blank holder 103 to the tailored blank 10 in the clamped state is set to satisfy (Equation 1). With this configuration, the clamped state can be maintained without hindering the first welded portion 14 and the second welded portion 15 from moving toward the top plate equivalent portion 2A. Therefore, material can more easily flow from the flange equivalent portion 4A toward the top plate equivalent portion 2A.

[0058] (1c) In the above embodiment, the portions of the die 101 and the blank holder 103 that may come into contact with the first welded portion 14 and the second welded portion 15 in the clamped state are made of a material with a higher hardness than the first welded portion 14 and the second welded portion 15. With this configuration, even if the raised weld bead moves through the movement area while contacting the die 101 and the blank holder 103, it is possible to prevent the die 101 and the blank holder 103 from being scraped or chipped. Therefore, deformation of the die 101 and the blank holder 103 can be suppressed, and a stable clamped state can be maintained.

[0059] (1d) In the above embodiment, in a plan view, the top plate-equivalent portion 2A is disposed on a portion of the rear side of the tailored blank 10, including the rear end portion. The first welded portion 14 extends from the front end portion of the tailored blank 10 toward the rear side, avoiding the top plate-equivalent portion 2A. With this configuration, the distance of the first welded portion 14 from the top plate-equivalent portion 2A varies between portions of the tailored blank 10 where the amount of deformation is relatively large and portions where the amount of deformation is relatively small. In other words, the first welded portion 14 is disposed on the tailored blank 10, taking into account the amount of movement of the first welded portion 14 during press working. Therefore, when the press-formed product 1 is completed, the first welded portion 14 can be positioned at a desired position. Specifically, a press-formed product 1 can be obtained in which the first welded portion 14 extends substantially parallel to the ridge line between the vertical wall portion 3 and the flange portion 4.

[0060] [1-7. Correspondence] In the above embodiment, the die 101 corresponds to the first die, the punch 102 corresponds to the second die, and the blank holder 103 corresponds to the holding part. Also, the rear side corresponds to the first direction side, and the front side corresponds to the second direction side.

[0061] [2. Second Embodiment] [2-1.Configuration] In the second embodiment, the description of the configuration common to the first embodiment will be omitted, and the description will focus on the differences. Note that the same reference numerals as in the first embodiment indicate the same configuration, and the preceding description will be referred to.

[0062] In the first embodiment, the die 101 and the blank holder 103 clamp the flange equivalent portion 4A so that the first welded portion 14 and the second welded portion 15 can move toward the top plate equivalent portion 2A in the clamped state, and therefore, a configuration is exemplified in which the pressure applied by the blank holder 103 to the tailored blank 10 in the clamped state is set to satisfy (Equation 1).

[0063] In the second embodiment, another configuration is illustrated in which the die 101 and the blank holder 103 clamp the flange equivalent portion 4A so that the first welding portion 14 and the second welding portion 15 can move toward the top plate equivalent portion 2A in the clamped state.

[0064] The press forming apparatus 100 includes an adjustment member. The adjustment member is a member for adjusting the distance between the tailored blank 10 and the die 101 in a clamped state. As shown in Fig. 9, the press forming apparatus 100 includes a first adjustment member 21 and a second adjustment member 22 as the adjustment members.

[0065] The first adjustment member 21 is a cylindrical metal member. As an example, the first adjustment member 21 is a distance block. However, the shape of the first adjustment member 21 is not limited to this. For example, the shape of the first adjustment member 21 may be a polygonal pillar.

[0066] The second adjustment member 22 is a disk-shaped metal. As an example, the second adjustment member 22 is a shim. However, the shape of the second adjustment member 22 is not limited to this. For example, the shape of the second adjustment member 22 may be rectangular. The thickness of the second adjustment member 22 is configured to be thinner than the thickness of the first adjustment member 21.

[0067] The first adjustment member 21 and the second adjustment member 22 are arranged outside the third steel plate 13. The first adjustment member 21 and the second adjustment member 22 are arranged in a stacked state between the blank holder 103 and the die 101. In this embodiment, the second adjustment member 22 is placed on the upper surface of the blank holder 103, and the first adjustment member 21 is placed on the upper surface of the second adjustment member 22. More specifically, a set of multiple overlapping first adjustment members 21 and second adjustment members 22 is arranged outside the outer periphery of the tailored blank 10. The set of multiple first adjustment members 21 and second adjustment members 22 is arranged at predetermined intervals along the outer periphery of the tailored blank 10. In other words, the set of multiple first adjustment members 21 and second adjustment members 22 is arranged around the tailored blank 10 in all directions, front to back, left to right.

[0068] The first adjustment member 21 and the second adjustment member 22 are arranged so that the distance between the tailored blank 10 and the die 101 in the clamped state is adjusted to be 5% or more and less than 20% of the thickness of the thinnest steel plate among the steel plates that make up the tailored blank 10. In this embodiment, the first adjustment member 21 and the second adjustment member 22 are arranged so that the distance between the upper surface of the tailored blank 10 and the lower surface of the die 101 in the clamped state is adjusted to be 5% or more and less than 20% of the thickness of the first steel plate 11.

[0069] [2-2. Effects] According to the second embodiment described above in detail, in addition to the effects (1a), (1c), and (1d) of the first embodiment described above, the following effects can be obtained.

[0070] (2a) The first adjustment member 21 and the second adjustment member 22 adjust the distance between the tailored blank 10 and the die 101 in the clamped state to be 5% or more and less than 20% of the thickness of the first steel plate 11. With this configuration, the clamped state can be maintained without preventing the first welded portion 14 and the second welded portion 15 from moving toward the top plate equivalent portion 2A. This makes it easier for material to flow from the flange equivalent portion 4A toward the top plate equivalent portion 2A. In other words, by creating a gap between the tailored blank 10 and the die 101, the tailored blank 10 does not come into excessive contact with the die 101 and the blank holder 103 in the clamped state. Furthermore, due to the nature of the material, the surface of the tailored blank 10 has some irregularities, so if the gap between the tailored blank 10 and the die 101 is 5% or more and less than 20% of the thickness of the first steel plate 11, the die 101 and blank holder 103 can partially abut and clamp the tailored blank 10.

[0071] (2b) The first adjustment member 21 and the second adjustment member 22 are arranged overlapping each other between the die 101 and the punch 102, and the thickness of the second adjustment member 22 is configured to be thinner than the thickness of the first adjustment member 21. This configuration makes it easier to finely adjust the distance between the tailored blank 10 and the die 101.

[0072] [2-3. Modification of the second embodiment] In the second embodiment described above, the press forming apparatus 100 is exemplified as being provided with two adjustment members, the first adjustment member 21 and the second adjustment member 22. However, the number of adjustment members provided in the press forming apparatus 100 is not limited to this. For example, the press forming apparatus 100 may be provided with one adjustment member, or may use three or more adjustment members stacked together.

[0073] 3. Other Embodiments Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments and can take on various forms.

[0074] (3a) In the above embodiment, the tailored blank 10 is a steel plate formed by welding together a first steel plate 11, a second steel plate 12, and a third steel plate 13. However, the configuration of the tailored blank 10 is not limited to this. For example, the tailored blank 10 may be a steel plate formed by welding together a first steel plate 11 and two second steel plates 12. The number of steel plates to be joined together can be determined appropriately depending on the shape of the desired press-formed product.

[0075] (3b) In the above embodiment, the second steel plate 12 is a steel plate that is thicker and has higher tensile strength than the first steel plate 11. However, the material of the second steel plate 12 is not limited to this. The second steel plate 12 may be a steel plate that is thinner than the first steel plate 11 and / or has lower tensile strength than the first steel plate 11. The strength ratio between the first steel plate 11 and the second steel plate 12 may be 1.0 or less. The manufacturing method of the press-formed product 1 in the above embodiment can be used for various tailored blanks 10 that combine steel plates that have different thicknesses and / or strengths.

[0076] (3c) In the above embodiment, a configuration was illustrated in which the first weld 14 extends from the front end of the tailored blank 10 toward the rear so as to avoid the top plate equivalent portion 2A. However, the position of the first weld 14 in the tailored blank 10 is not limited to this. For example, the first weld 14 may also be positioned in the tailored blank 10 so as to extend approximately parallel to the top plate equivalent portion 2A. The first weld 14 and the second weld 15 in the tailored blank 10 vary depending on the shape of the press-formed product 1, and may be provided at any position predicted by working backward from the positions of the first weld 14 and the second weld 15 in the press-formed product 1.

[0077] (3d) In the manufacturing method of the press-formed product 1, the configuration of the first embodiment and the configuration of the second embodiment may be implemented simultaneously. That is, the press-forming apparatus 100 may be provided with an adjustment member, and may be set so that the pressure applied by the blank holder 103 to the tailored blank 10 in the clamping state satisfies (Equation 1).

[0078] (3e) The function of one component in the above embodiments may be distributed among multiple components, or the functions of multiple components may be integrated into one component. Also, part of the configuration of the above embodiments may be omitted. Furthermore, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0079] [Technical idea disclosed in this specification] [Item 1] A method for manufacturing a molded product by pressing a tailored blank to obtain a molded product, The tailored blank is a steel plate obtained by welding a first steel plate and a second steel plate having a plate thickness and / or strength different from that of the first steel plate, The tailored blank has a welded portion formed at a location where an end surface of the first steel plate and an end surface of the second steel plate are welded together, The molded product includes a top plate portion, a vertical wall portion, and a flange portion, The vertical wall portion is a plate-shaped portion that stands from an end of the top plate portion so as to surround the top plate portion, The flange portion is a plate-shaped portion extending from the vertical wall portion in a direction intersecting with the vertical wall portion, and is a portion arranged to surround the top plate portion in a plan view perpendicular to the top plate portion, The tailored blank includes a top plate equivalent portion representing a portion corresponding to the top plate portion, a vertical wall equivalent portion representing a portion corresponding to the vertical wall portion, and a flange equivalent portion representing a portion corresponding to the flange portion, The top plate equivalent portion is disposed on the first steel plate, The welded portion is disposed on the flange-equivalent portion, The manufacturing method includes: placing the tailored blank between a first mold and a second mold spaced apart; a clamping state in which the flange-corresponding portion is clamped between the first mold and the holding portion; While the first mold and the second mold are held in the clamped state, the first mold and the second mold are brought close to each other, thereby pressing the tailored blank with the first mold and the second mold to form the top plate portion, the vertical wall portion, and the flange portion; Including, the holding portion is a member that is disposed between the first mold and the second mold and is a member that can clamp the flange portion in cooperation with the first mold, In the clamped state, the first mold and the holding portion clamp the flange equivalent portion so that the welded portion can move toward the top plate equivalent portion.

[0080] [Item 2] A method for producing a molded article according to item 1, A method for manufacturing a molded product, wherein the pressure applied by the holding portion to the tailored blank in the clamped state is set to satisfy the following formula (Mathematical Formula 1).

[0081]

number

[0082] [Item 4] A method for producing a molded article according to any one of items 1 to 3, In the forming, the movement amount of the welded portion toward the top plate portion is designed in advance, A method for manufacturing a molded product, wherein the portion of the first mold and / or the holding portion that can come into contact with the welded portion in the clamped state has a hardness higher than that of the welded portion.

[0083] [Item 5] A method for producing a molded article according to any one of items 1 to 4, In a plan view perpendicular to the thickness direction of the tailored blank, the top plate equivalent portion is arranged in a part of the tailored blank on the first direction side, including the end portion on the first direction side, A method for manufacturing a molded product, wherein the welded portion extends from the end on the second direction side, which is opposite the end on the first direction side, toward the first direction side so as to avoid the top plate equivalent portion. [Explanation of symbols]

[0084] 1...press-formed product, 2...top plate portion, 2A...top plate equivalent portion, 2C, 2D...top plate forming portion, 3...vertical wall portion, 3A...vertical wall equivalent portion, 3C, 3D...vertical wall forming portion, 4...flange portion, 4A...flange equivalent portion, 10...tailored blank, 11...first steel plate, 12...second steel plate, 13...third steel plate, 14...first welded portion, 14A, 14B, 15A, 15B...dashed lines, 15...second welded portion, 21...first adjusting member, 22...second adjusting member, 100...press forming apparatus, 101...die, 102...punch, 103...blank holder.

Claims

1. A method for manufacturing a molded product by pressing a tailored blank to obtain a molded product, comprising the steps of: The tailored blank is a steel plate obtained by welding a first steel plate and a second steel plate having a plate thickness and / or strength different from that of the first steel plate, The tailored blank has a welded portion formed at a location where an end surface of the first steel plate and an end surface of the second steel plate are welded together, The molded product includes a top plate portion, a vertical wall portion, and a flange portion, The vertical wall portion is a plate-shaped portion that stands from an end of the top plate portion so as to surround the top plate portion, The flange portion is a plate-shaped portion extending from the vertical wall portion in a direction intersecting the vertical wall portion, and is a portion arranged to surround the top plate portion in a plan view perpendicular to the top plate portion, The tailored blank includes a top plate equivalent portion representing a portion corresponding to the top plate portion, a vertical wall equivalent portion representing a portion corresponding to the vertical wall portion, and a flange equivalent portion representing a portion corresponding to the flange portion, The top plate equivalent portion is disposed on the first steel plate, The welded portion is disposed on the flange-equivalent portion, The manufacturing method includes: placing the tailored blank between a first die and a second die that are spaced apart; a clamping state in which the flange corresponding portion is clamped between the first mold and the holding portion; While the first mold and the second mold are held in the clamped state, the first mold and the second mold are brought close to each other, thereby pressing the tailored blank with the first mold and the second mold to form the top plate portion, the vertical wall portion, and the flange portion; Including, the holding portion is a member that is disposed between the first mold and the second mold and is a member that is capable of clamping the flange corresponding portion in cooperation with the first mold, In the clamped state, the first mold and the holding portion clamp the flange equivalent portion so that the welded portion can move toward the top plate equivalent portion.

2. A method for producing the molded article according to claim 1, A method for manufacturing a molded product, wherein the pressure applied by the holding portion to the tailored blank in the clamped state is set to satisfy the following formula (Mathematical Formula 1). [Equation 1] X: Pressure applied by the holding portion to the tailored blank. Ts: tensile strength of the first steel plate. A: The contact area between the holding portion and the tailored blank before the tailored blank is pressed by the first mold and the second mold.

3. A method for producing the molded article according to claim 1 or claim 2, The plate thickness of the first steel plate is thinner than the plate thickness of the second steel plate, an adjustment member is disposed between the first mold and the second mold for adjusting the distance between the tailored blank and the first mold in the clamped state; A method for manufacturing a molded product, wherein the adjustment member adjusts the distance between the tailored blank and the first mold in the clamped state to be 5% or more and less than 20% of the thickness of the first steel plate.

4. A method for producing the molded article according to claim 1 or claim 2, In the forming, the movement amount of the welded portion toward the top plate equivalent portion is designed in advance, A method for manufacturing a molded product, wherein a portion of the first mold and / or the holding portion that may come into contact with the welded portion in the clamped state has a hardness higher than that of the welded portion.

5. A method for producing the molded article according to claim 1 or claim 2, In a plan view perpendicular to the thickness direction of the tailored blank, the top plate equivalent portion is arranged in a part of the tailored blank on the first direction side, including an end portion on the first direction side, A method for manufacturing a molded product, wherein the welded portion extends from the end on the second direction side, which is opposite the end on the first direction side, toward the first direction side so as to avoid the top plate equivalent portion.

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