JP2021049551A - Press molding method and press molded product - Google Patents

Abstract

To avoid deterioration of strength by preventing deformation of a junction of metal plates, when a patchwork material is press-molded to form a bent part.SOLUTION: In a press molding method in which a patchwork material W formed by overlapping a first metal plate W1 and a second metal plate W2 and by joining them at a plurality of junctions (nuggets N) is press-molded, and in an overlapping part of both metal plates W1, W2, a bent part R is formed in an area between a plurality of nuggets N, while bending the patchwork material W, the second metal plate W2 arranged on the curvature center side of the bent part R is curved to the separation side from the first metal plate W1 arranged on the opposite side of the center of curvature.SELECTED DRAWING: Figure 4

Description

The present invention relates to a press molding method and a press molded product.

Conventionally, there is known a method of press molding using a patchwork material partially reinforced by superimposing another metal plate on a metal plate and welding it (see, for example, Patent Document 1 below).

JP-A-2017-177115

For example, FIG. 8A shows a patchwork material 100 in which the first metal plate 101 and the second metal plate 102 are overlapped and joined at a plurality of joining points 103 and 104. When the patchwork material 100 is press-molded to form the bent portions 105 and 106 as shown in FIG. 8 (B), the patchwork material 100 before molding has the joint points 103 of both metal plates 101 and 102. The actual length L between 104 is the same, but after molding, the actual length L1 between the joint points 103 and 104 of the second metal plates 102 arranged on the curvature center side of the bent portions 105 and 106 is the first metal plate 101. It is shorter than the actual length L2 between the joint points 103 and 104. Due to the actual length difference ΔL (= L2-L1) between the two metal plates 101 and 102, shear stress is applied to the joint points 103 and 104, which may deform the joint points 103 and 104 and cause a decrease in strength. is there.

Therefore, the present invention is to prevent deformation of the joint points between metal plates and avoid a decrease in strength when the patchwork material is press-formed to form a bent portion.

In order to solve the above problems, in the present invention, a patchwork material obtained by superimposing a first metal plate and a second metal plate and joining them at a plurality of joint points is press-molded to form an overlapping portion of both metal plates. Of these, a press forming method for forming a bent portion in a region between the plurality of joint points, wherein the second metal plate is arranged on the curvature center side of the bent portion while bending the patchwork material. Is provided in a press molding method in which the metal plate is curved to a side away from the first metal plate arranged on the side opposite to the center of curvature.

By bending the second metal plate to the side away from the first metal plate while bending the patchwork material in this way, the actual length of the second metal plate can be lengthened. It can be offset by the difference in actual length between the two metal plates due to the formation of. As a result, the shear stress applied to the joint point can be relaxed, and a decrease in the strength of the joint point can be avoided.

Specifically, for example, the first metal plate is provided with a through hole, and the second metal plate is pressed through the through hole by a pressing means while bending the patchwork material. The metal plate 2 can be curved to the side away from the first metal plate.

By the above press molding method, a patchwork material obtained by superimposing a first metal plate and a second metal plate and joining them at a plurality of joint points is press-molded, and among the overlapping portions of both metal plates, the plurality of A press-molded product in which a bent portion is formed in a region between the joint points of the above, and is arranged on the second metal plate arranged on the curvature center side of the bent portion on the side opposite to the curvature center of the bent portion. A press-molded product having a curved portion curved on the side away from the first metal plate is obtained.

As described above, according to the present invention, when the patchwork material is press-formed to form a bent portion, the shear stress applied to the joint points between the metal plates is relaxed, so that the deformation of the joint points is prevented. It is possible to avoid a decrease in strength.

(A) is a side view of the patchwork material, and (B) is the same plan view. It is sectional drawing which shows the procedure of the press molding method which concerns on one Embodiment of this invention, and shows the state before the start of molding. It is sectional drawing which shows the procedure of the said press forming method, and shows the state immediately after contacting a patchwork material with a punch. It is sectional drawing which shows the procedure of the said press forming method, and shows the state which pressed the 2nd metal plate with a movable punch and curved. It is sectional drawing which shows the procedure of the said press molding method, and shows the state at the time of completion of molding. It is a perspective view of the press-molded article formed by the said press-molding method. (A) is a cross-sectional view of the patchwork material according to another example, and (B) is a press forming method according to another embodiment of the present invention, in which the patchwork material shown in FIG. It is sectional drawing of the press-molded article. (A) is a cross-sectional view of a patchwork material, and (B) is a cross-sectional view of a press-molded product obtained by bending the patchwork material of FIG. (A) by a conventional method.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the press forming method according to the embodiment of the present invention, first, a first metal plate W1 made of a steel plate and a second metal plate W2 are superposed, and spot welding (for example, direct) is performed at a plurality of portions of these overlapping portions. By performing spot welding), the patchwork material W as shown in FIGS. 1 (A) and 1 (B) is formed. Both metal plates W1 and W2 are fixed via a nugget N as a joint point. In the illustrated example, a plurality of nuggets N separated in the longitudinal direction (vertical direction in FIG. 1B) are provided near both ends in the width direction (horizontal direction in FIGS. 1A and 1B) of the second metal plate W2. It is formed. The joining point is not limited to a nugget formed by melting and solidifying the contact points between the metal plates W1 and W2, but also a welding point where the metal plates W1 and W2 are joined in a solid state, and both metal plates W1. It may be a joining point where W2 is joined by a mechanical method.

A plurality of through holes P separated in the longitudinal direction are formed in the first metal plate W1. The plurality of through holes P are provided in the region between the width directions of the nugget N separated in the width direction in the first metal plate W1. In the illustrated example, the through holes P provided in the central portion in the width direction of the first metal plate W1 and the pair of through holes P separated in the width direction are alternately provided in the longitudinal direction. Further, in the illustrated example, the nugget N and the through hole P are provided at the same longitudinal position. The position and number of the through holes P are not limited to the above, and may be provided in a manner suitable for forming the curved portion C on the second metal plate W2 in the subsequent press molding.

The above patchwork material W is molded using the press molding die shown in FIG. This press-molding die has an upper die 1, a punch 2, and a blank holder 3. The upper mold 1 includes an upper mold main body 4 and a pressing means for pressing the second metal plate W2 of the patchwork material W from above. As the pressing means, for example, a plurality of movable punches 5 provided so as to be vertically movable with respect to the upper die main body 4 and an advancing / retreating means 6 for advancing / retreating the movable punch 5 with respect to the upper die main body 4 are provided. As the advancing / retreating means 6, for example, a driving mechanism such as an electric cylinder or an air cylinder, or a buffering mechanism such as a spring or a damper can be provided. The plurality of movable punches 5 are provided at positions where the flat plate-shaped patchwork material W is placed on the blank holder 3 and overlaps with the plurality of through holes P provided in the first metal plate W1 in the pressing direction. Be done. A recess 2a is provided on the upper surface of the punch 2. The recess 2a extends along the longitudinal direction (direction orthogonal to the paper surface of FIG. 2), and in the present embodiment, the recess 2a is provided over the entire length of the upper surface of the punch 2 in the longitudinal direction.

When the upper mold 1 is lowered after the patchwork material W is placed on the blank holder 3, the end portion of the patchwork material W is sandwiched between the upper mold 1 and the blank holder 3 as shown in FIG. To. When the upper die 1 is further lowered, the upper die 1, the blank holder 3, and the patchwork material W are integrally lowered, and the central region in the width direction of the patchwork material W is pressed against the punch 2 from above, and the patchwork material W is pressed. W begins to bend so that it is convex upward.

When the upper mold 1 is further lowered, the region between the width directions of the nugget N in the overlapping portion of the two metal plates W1 and W2 of the patchwork material W is pressed against the curved surface of the corner of the punch 2 and is pressed in the width direction. Bent portions R begin to be formed at two separated locations (see FIG. 4). Further, in the present embodiment, immediately after the patchwork material W abuts on the punch 2 and begins to bend (or at the same time when the patchwork material W begins to bend), the movable punch 5 provided on the upper die 1 is a first metal plate. The second metal plate W2 is pressed downward through the through hole P of W1. As a result, the second metal plate W2 is curved toward the side away from the first metal plate W1 (in the illustrated example, it is convex downward). The curved portion C formed in this way is housed in the recess 2a on the upper surface of the punch 2.

After that, when the upper mold 1 is further lowered, the bent portion R of the overlapping portion of both metal plates W1 and W2 is further bent along the curved surface of the corner of the punch 2 while the both metal plates W1 and W2 are stretched. .. At this time, as the molding of the bent portion R progresses (the radius of curvature becomes smaller), the difference in actual length between the two metal plates W1 and W2 in the bent portion R increases, but the curvature of the second metal plate W2 increases accordingly. Part C bulges downward and the actual length becomes longer. Then, when the upper die 1 reaches the lower end position (bottom dead center), the bent portion R is completely formed along the curved surface of the corner of the punch 2, and the curved portion C that bulges downward is the recess of the punch 2. It is pressed against the inner surface of 2a and molded (see FIG. 5). The curved portion C is formed in a region between the width directions of the nuggets N of both metal plates W1 and W2, excluding the bent portion R. When the molding shown in FIG. 5 is completed, the curved portion C may be separated from the inner surface of the recess 2a of the punch 2. As described above, the press-molded product W'made of the patchwork material W is formed.

As described above, by forming the curved portion C on the second metal plate W2 while forming the bent portion R on the patchwork material W, the actual length difference between the two metal plates W1 and W2 in the bent portion R can be reduced. Since the difference in actual lengths of the two metal plates W1 and W2 due to the curved portion C can be offset, the difference in actual lengths of the two metal plates W1 and W2 in the region between the width directions of the nugget N can be suppressed. As a result, the shear stress applied to the nugget N due to the difference in actual length between the two metal plates W1 and W2 is relaxed, so that the deformation of the nugget N is prevented and the fixing strength of the two metal plates W1 and W2 is prevented from decreasing. can do.

By the way, in the above press molding, after pressing the second metal plate W2 with the movable punch 5 to form the downwardly convex curved portion C as shown in FIG. 4, the second metal plate is formed with the movable punch 5. Even if W2 is not continuously pressed, the downward bulge amount of the curved portion C is large due to the increase in the actual length difference between the two metal plates W1 and W2 due to the molding of the bent portion R (reduction of the radius of curvature). Become. Therefore, after forming the curved portion C with the movable punch 5, the movable punch 5 is retracted to the side (upward) away from the second metal plate W2, and only the difference in actual lengths of the two metal plates W1 and W2 at the bent portion R is obtained. Can be used as a driving force to increase the amount of swelling of the curved portion C. In this case, the amount of swelling of the curved portion C increases as the difference in actual lengths of the two metal plates W1 and W2 due to the bent portion R increases, so that the nugget N can be obtained at any time during the molding of the bent portion R. The actual length difference between the two metal plates W1 and W2 in the region between the width directions can be made almost zero, and the shear stress applied to the nugget N can be further reduced. Further, in this case, since the pressing force of the movable punch 5 that presses the second metal plate W2 is relatively small, the pressing marks (recesses) of the movable punch 5 are less likely to occur on the second metal plate W2.

On the other hand, even after the curved portion C is formed by the movable punch 5, the movable punch 5 may continue to press the second metal plate W2 downward. In this case, the curved portion C is pressed against the recess 2a of the punch 2 to facilitate molding.

As shown in FIG. 6, the press-molded product W'molded by the above method includes a first metal plate W1 having a hat-shaped cross section and a second metal plate W2 for reinforcing the first metal plate W1. The first metal plate W1 includes a top surface portion W11, a pair of vertical wall portions W12 extending downward from both ends in the width direction of the top surface portion W11, and a pair of flange portions W13 extending outward in the width direction from the lower end of the vertical wall portion W12. Has. The second metal plate W2 includes a top surface portion W21 arranged below the top surface portion W11 of the first metal plate W1 and a pair of vertical wall portions W22 extending downward from both ends in the width direction of the top surface portion W21. Have. The vertical wall portions W21 and W22 of both metal plates W1 and W2 are fixed to each other via a nugget N. The top surface portion W11 of the first metal plate W1 has a flat plate shape, and the continuous portion W21 of the second metal plate W2 has a curved portion C having a downward convex shape. A plurality of through holes P are provided in a region of the first metal plate W1 that overlaps the curved portion C in the vertical direction. Of the top surface portion W21 of the second metal plate W2, a pressing mark (not shown) pressed by the movable punch 5 is provided directly below the through hole P.

In this press-molded product W', the difference between the actual lengths of the two metal plates W1 and W2 at the bent portion R and the difference between the actual lengths of the two metal plates W1 and W2 due to the curved portion C cancel each other out so that the two metal plates W1 and W1 The actual length difference between the two metal plates W1 and W2 in the overlapping portion of W2 (specifically, the region between nuggets N) is almost zero. As a result, the shear stress applied to the nugget N is relaxed, and it is possible to prevent a decrease in the fixing strength of both metal plates W1 and W2 via the nugget N.

In the subsequent coating process, the press-molded product W'is coated with a rust preventive paint on the entire surface, for example, by soaking in a dove. At this time, if both metal plates W1 and W2 are in close contact with each other, it is difficult for the rust preventive paint to enter between them, so that a portion to which the rust preventive paint is not applied may occur and the rust preventive effect may be deteriorated. On the other hand, in the above-mentioned press-molded product W', the curved portion C is provided on the top surface portion W21 of the second metal plate W2, so that a gap is provided between the top surface portions W11 and W21 of both metal plates W1 and W2. It is formed. As a result, in the subsequent coating process, the rust preventive paint easily enters the gap between the top surfaces W11 and W21 of both metal plates W1 and W2, so that the rust preventive effect is enhanced.

The present invention is not limited to the above embodiments. For example, in the above embodiment, the case where the press-molded product W'with a hat-shaped cross section is formed by the press-molding method according to the present invention is shown, but the present invention is not limited to this. For example, in the press molding method according to the present invention, the patchwork material W as shown in FIG. 7 (A) is bent, and the press molded product W having an L-shaped cross section as shown in FIG. 7 (B) is used. In this case as well, by forming the curved portion C on the second metal plate W2 while forming the bent portion R, the fruits of both metal plates W1 and W2 in the region between the nuggets N are formed. It is possible to suppress the length difference and relax the shearing force applied to the nugget N. Since the same is true to the above embodiment except for the shape of the press-molded product, duplicate description will be omitted.

1 Upper mold 2 Punch 3 Blank holder 4 Upper mold body 5 Movable punch 6 Advance / retreat means W Patchwork material W1 First metal plate W2 Second metal plate W', W "Press molded product C Curved part N Nugget (joint point) )
P through hole R bent part

Claims (4)

A patchwork material obtained by superimposing a first metal plate and a second metal plate and joining them at a plurality of joint points is press-molded, and a region between the plurality of joint points in the overlapped portion of both metal plates. It is a press molding method that forms a bent part in the metal.
While bending the patchwork material, the second metal plate arranged on the curvature center side of the bent portion is curved to a side away from the first metal plate arranged on the side opposite to the curvature center. Press molding method. A through hole is provided in the first metal plate, and a through hole is provided.
A claim for bending the second metal plate to a side away from the first metal plate by pressing the second metal plate through the through hole while bending the patchwork material. Item 1. The press molding method according to Item 1. A patchwork material obtained by superimposing a first metal plate and a second metal plate and joining them at a plurality of joint points is press-molded, and a region between the plurality of joint points in the overlapped portion of both metal plates. It is a press-molded product with a bent part formed on the surface.
The second metal plate arranged on the curvature center side of the bent portion is provided with a curved portion curved on the side away from the first metal plate arranged on the side opposite to the curvature center of the bent portion. Press molded product. The press-molded product according to claim 3, wherein a through hole is provided in a region of the first metal plate that overlaps with the curved portion of the second metal plate.

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