JP7144338B2 - Pressing method - Google Patents

Description

The present disclosure relates to a press working method for a press-formed product manufactured by press working.

High-strength steel sheets are required for improving crash safety and weight reduction of automobiles. However, there is a problem that as the tensile strength of the steel sheet increases, the ductility related to press formability decreases. Patent Literature 1 proposes a technique for making wrinkles easier to extend by forming unevenness on the mold press surface to increase the line length of the wall portion of the member in the vertical wall portion having a curved portion where wrinkles are likely to occur. It is

JP 2016-43403 A

The method disclosed in Patent Document 1 provides unevenness on the wall. In this method, when the pressing direction and the wall are parallel, the amount of material flowing into the uneven portion is small, but the amount of material flowing into the top plate portion is large, and the wrinkles generated on the top plate portion side are sufficiently removed. In some cases, it could not be suppressed.

An object of the present disclosure is to propose a technique capable of suppressing the occurrence of wrinkles.

One aspect of the present disclosure is a press-formed product that includes a top plate portion and at least one vertical wall portion that is bent from the top plate portion and extends in a direction intersecting the top plate portion. The press-formed product has a curved portion that is a part of at least one vertical wall portion, and a ridgeline formed between the curved portion and the top plate portion curves toward the inside of the top plate portion. It has one bend. At least one bead is formed on the top plate along a ridge formed between the at least one curved portion and the top plate.

With such a configuration, the increase in the thickness of the top plate due to the material flowing into the top plate when the curved portion is formed is the same as the increase in the thickness of the top plate due to the formation of the bead. Subtracted by reduction. Therefore, the amount of increase in the plate thickness of the top plate portion is reduced as compared with the case where the bead is not formed.

The at least one vertical wall section mentioned above may comprise two vertical wall sections. One vertical wall portion of the two vertical wall portions includes a first curved portion, and the other vertical wall portion different from the one vertical wall portion includes a second curved portion. good too. The first curved portion and the second curved portion may be provided so as to sandwich the top plate portion therebetween. At least two beads may be formed on the top plate portion along the ridgelines of the first curved portion and the second curved portion.

With such a configuration, wrinkles occurring in the top plate portion can be suppressed even when curved portions are provided on both sides of the top plate portion of the press-molded product.
Further, the press-formed product described above may include a portion used for the lower portion of the center pillar of the vehicle. Such a configuration can be used below the center pillar.

Moreover, the press-formed product described above may be composed of a member having a tensile strength of 980 MPa or more. The higher the tensile strength of the steel sheet, the lower the ductility and the more likely wrinkles are to occur. However, in the press-formed product having the above-described structure, the occurrence of wrinkles can be suppressed satisfactorily even in members with high tensile strength.

Another aspect of the present disclosure is press molding comprising a top plate portion, a vertical wall portion that is bent from the top plate portion and extends in a direction intersecting the top plate portion, and a flange portion that is connected to the vertical wall portion. It is a press processing method for products. The press-formed product includes a curved portion that is a part of the vertical wall portion, and a curved portion in which a ridge line formed between the curved portion and the top plate portion curves toward the inside of the top plate portion. . In this processing method, by forming a first bead in a curved shape on the blank material and bending the position where the first bead is formed, the curved portion is bent so that a part of the first bead is included in the curved portion. is formed, and a portion of the first bead that is different from the above portion is a second bead having a height smaller than that of the first bead.

With such a press working method, it is possible to suppress the occurrence of wrinkles and cracks in the press-formed product. This is because the increase in the thickness of the top plate due to the material flowing into the top plate when the curved portion is formed is subtracted by the decrease in the thickness of the top plate due to the formation of the bead. , the amount of increase in the plate thickness of the top plate portion is reduced compared to the case where the bead is not formed, and as a result, wrinkles of the top plate portion are suppressed. In addition, part of the material forming the first bead moves toward the curved portion, thereby suppressing a decrease in plate thickness of the curved portion and the flange portion, thereby suppressing cracking.

Yet another aspect of the present disclosure is a press-formed product that includes a top plate portion and two vertical wall portions that are bent from the top plate portion and spread in a direction intersecting the top plate portion. The press-formed product includes at least one curved portion that is a part of the two vertical wall portions, and a ridge formed between the curved portion and the top plate portion curves toward the inside of the top plate portion. A curved portion is provided. One vertical wall portion of the two vertical wall portions includes a first curved portion, and the other vertical wall portion different from the one vertical wall portion includes a second curved portion. . The top plate portion is formed with a protruding portion that protrudes concavely or convexly from the top plate portion. The first curved portion and the second curved portion are provided so as to sandwich the projecting portion therebetween.

With such a configuration, when the first curved portion and the second curved portion are formed, the increase in the plate thickness of the top plate portion due to the material flowing into the top plate portion causes the projection portion to be formed. It is deducted due to the reduction in the thickness of the top plate due to Therefore, the amount of increase in the plate thickness of the top plate portion is reduced as compared with the case where the protruding portion is not formed.

It is a figure which shows the press-formed product of embodiment. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1; It is a perspective view showing a part of structure of a vehicle body. 4A and 4B are diagrams illustrating the press process for forming the first bead. 5A and 5B are diagrams for explaining the press process for manufacturing a press-formed product. FIG. 6A is a diagram illustrating how wrinkles are generated when beads are not formed, and FIG. 6B is a diagram illustrating how wrinkles are generated when beads are formed.

Embodiments of the present disclosure will be described below with reference to the drawings. Note that the vertical and horizontal directions used in the following description are used for convenience of description, and do not limit the mode of use of the present disclosure.

[1. embodiment]
[1-1. overall structure]
A press-formed product 1 of the embodiment shown in FIG. The press-formed product 1 may also include flange portions 13L and 13R that are connected to the vertical wall portions 12L and 12R, respectively.

The top plate portion 11 includes a main plate portion 11a having a length in the vertical direction, an upper portion 11b extending laterally from the upper end of the main plate portion 11a, and a lower portion 11c extending laterally from the lower end of the main plate portion 11a. The upper end side portion 11d located on the upper side of the main plate portion 11a and connected to the upper side portion 11b has a smaller width in the left-right direction than the portion of the main plate portion 11a below the upper end side portion 11d. The area forming 11a is small.

Vertical wall portions 12L and 12R are bent from top plate portion 11 and spread in a direction intersecting top plate portion 11 . 12 L of vertical wall parts are provided with 14 L of curved parts as the part. The vertical wall portion 12R also includes a curved portion 14R as a part thereof.

The curved portions 14L and 14R are portions that have a curved shape when projected onto a virtual plane parallel to the spreading surface of the top plate portion 11 . The bending directions of the bending portions 14L and 14R are the directions in which the ridgelines 15L and 15R formed between the top plate portion 11 and the bending portions 14L and 14R bend toward the inside of the top plate portion 11, respectively. In other words, when the press-formed product 1 is projected onto the above-described imaginary plane, the curved portions 14L and 14R are the concave top plate portion 11 and the convex flange portion of the vertical wall portions 12L and 12R. It is a portion positioned between the portions 13L and 13R. The curved portions 14L and 14R are formed outside the intersecting region of the main plate portion 11a and the lower portion 11c. The bending direction of the ridgeline 15L is the same as the bending direction of the bending portion 14L, and the bending direction of the ridgeline 15R is the same as the bending direction of the bending portion 14R.

Two beads 16L and 16R are formed on the top plate portion 11 along the above-described curved ridgelines 15L and 15R. The two beads 16L and 16R are L-shaped along the outer edges of the intersection of the main plate portion 11a and the lower portion 11c.

As shown in FIG. 2, the press-formed product 1 has beads 16L and 16R formed at both the left and right ends of the top plate portion 11, and a curved portion toward the rear opposite to the forward direction in which the beads 16L and 16R protrude. 14L and 14R expand. In other words, the beads 16L and 16R protrude from the top plate portion 11 in a direction opposite to the direction in which the vertical wall portions 12L and 12R spread from the top plate portion 11 . Further, the flange portions 13L and 13R are connected at the ends to which the curved portions 14L and 14R extend. The flange portions 13L and 13R extend substantially parallel to the top plate portion 11 .

As shown in FIG. 1, the two curved portions 14L and 14R described above are provided on the left and right so as to sandwich the top plate portion 11 therebetween.
A recessed portion 17 is formed in the upper end side portion 11d. Two curved portions 141L and 141R are formed on the left and right sides of the upper end side portion 11d, and ridgelines 151L and 151R are formed between the curved portions 141L and 141R and the top plate portion 11, respectively. The recessed portion 17 is formed between the two curved portions 141L and 141R on the upper end side portion 11d. The recessed portion 17 corresponds to an example of a projecting portion.
The press-formed product 1 described above may be made of high-tensile steel having a tensile strength of 980 MPa or more (in this embodiment, a tensile strength of 1470 MPa).

[1-2. Arrangement of press-formed products]
As shown in FIG. 3, the press-formed product 1 of this embodiment can be used as a center pillar 33 that constitutes a part of the monocoque structure 31 of the vehicle body. The left-right direction of the press-formed product 1 may be arranged in the front-rear direction of the vehicle.

[1-3. Press processing method]
The press-molded product 1 can be manufactured by the following steps. It should be noted that the following steps are merely examples of the present disclosure, and may be changed to various aspects of the processing method within the scope of including the technical ideas of the present disclosure.

(i) Formation of First Bead As shown in FIG. 4A, in this step, an upper mold 51, a lower mold 52, a die 53 and a die 54 are used. A groove 55 is formed in the upper die 51 and a ridge 56 is formed in the lower die 52 . The grooves 55 and the ridges 56 are curved in a plan view (that is, when viewed from above or below in the pressing direction).

The blank material 41 is placed on the left and right dies 53 and 54 , the upper die 51 is lowered, and the dies 53 and 54 and the upper die 51 sandwich and grip the blank material 41 . For convenience of explanation, the blank material 41 is also referred to as a blank material after being pressed.

Subsequently, as shown in FIG. 4B, when the dies 53 and 54 and the upper die 51 are lowered toward the lower die 52 while holding the blank 41, shallow drawing is performed by the grooves 55 and the ridges 56. , curved first beads 71L and 71R are formed on the blank material 41 in plan view.

(ii) Formation of Vertical Wall and Flange As shown in FIG. 5A, in this step, an upper mold 61, an upper mold 62, a pad 63, and a lower mold 64 are used. The blank material 41 having the first beads 71L and 71R formed thereon is placed on the lower die 64, the pad 63 is lowered, and the blank material 41 is sandwiched and gripped by the pad 63 and the lower die 64.

The corners 81 and 82 of the upper molds 61 and 62 and the corners 83 and 84 of the lower mold 64 for forming the bent portions of the curved portions 14L and 14R and the flange portions 13L and 13R are the bent portions described above. The angle of the portion is configured to be less than 90 degrees. As the angles of the corners 81 to 84 of the curved portions 14L and 14R approach 90 degrees, the material can easily flow into the flange portions 13L and 13R, and cracks at the flange portions 13L and 13R can be suppressed. However, the angle can be adjusted as appropriate in consideration of cracks at the root portion where the flange portions 13L, 13R and the curved portions 14L, 14R continuously intersect. Note that the corners 81 to 84 described above may have rounded or pointed tips.

Subsequently, as shown in FIG. 5B, when the upper molds 61 and 62 are lowered while holding the blank material 41, the press-formed product 1 is formed. In this press working, the positions where the first beads 71L and 71R described above are formed are bent. As a result, the curved portion 14L is formed such that the left portion of the first bead 71L is included in the curved portion 14L. Further, the curved portion 14R is formed such that a portion of the right side of the first bead 71R is included in the curved portion 14R. In other words, the curved portions 14L and 14R are formed such that the material forming the first beads 71L and 71R flows into the curved portion side.

Further, by the press working described above, the portions of the first beads 71L and 71R that differ from the portions described above become the beads 16L and 16R described above. These beads 16L and 16R are beads smaller in height than the first beads 71L and 71R and correspond to second beads.

[1-4. Evaluation test]
Wrinkles that occur when forming the above-described curved portion by press working are used as a material for each of (a) when beads are not formed on the top plate portion and (b) when beads are formed on the top plate portion. Evaluation was performed by changing the tensile strength of the steel plate. In this evaluation test, the occurrence of wrinkles was calculated using CAE.

The above (a) was evaluated using five types of steel plates having tensile strengths of 440 MPa, 590 MPa, 980 MPa, 1180 MPa and 1470 MPa. Regarding the above (b), three types of steel plates with tensile strengths of 980 MPa, 1180 MPa and 1470 MPa were used for evaluation.

FIG. 6A shows the evaluation result in the above case (a). When steel sheets with tensile strengths of 440 MPa and 590 MPa were used, wrinkles did not occur. However, when steel plates with tensile strengths of 980 MPa, 1180 MPa, and 1470 MPa were used, wrinkles were generated extending toward the top plate portion. FIG. 6B shows the evaluation result in the above case (b). When beads were formed, the occurrence of wrinkles was significantly suppressed compared to when beads were not formed.

The above results confirmed the following. When the tensile strength of the steel plate exceeds 980 MPa, wrinkles are likely to occur when the curved portion is formed. can also effectively suppress wrinkles.

[1-5. effect]
According to the embodiment detailed above, the following effects are obtained.
(1a) In the press-formed product 1 of the present embodiment, the increase in plate thickness (excess material) caused by the material leaning toward the ridges when forming the curved portions 14L and 14R causes the beads 16L and 16R to be formed. It is deducted due to the reduction in the plate thickness of the top plate portion 11 due to this. Therefore, the amount of increase in the plate thickness of the top plate portion 11 is reduced compared to the case where the beads 16L and 16R are not formed. It can suppress the occurrence.

(1b) The press-formed product 1 is provided with curved portions 14L and 14R on both sides of the top plate portion 11, and wrinkles generated in the top plate portion 11 are removed from both curved portions 14L and 14R. can be suppressed.

(1c) The press-formed product 1 uses high-strength steel with a tensile strength of 1470 MPa. Such a steel sheet with high tensile strength has low ductility and is easily wrinkled.

(1d) In the press-molded product 1, the concave portion 17 is formed between the curved portions 141L and 141R in the upper end side portion 11d. As a result, the material can be pulled toward the recessed portion 17, suppressing an increase in the plate thickness caused by the material leaning toward the ridge line portion when forming the curved portions 141L and 141R, thereby preventing wrinkles in the top plate portion 11. can suppress the occurrence of Also, the recessed portion 17 can be formed in a portion such as the upper end side portion 11d where the width for forming the bead is not sufficient, and wrinkles are generated in both the left and right curved portions 141L and 141R. can be suppressed. In the above-described embodiment, the concave portion 17 that is recessed backward from the top plate portion 11 is illustrated, but the concave portion 17 may be convex shape that protrudes forward from the top plate portion 11 .

(1e) With the press working method described in the present embodiment, it is possible to manufacture the press-formed product 1 in which the occurrence of wrinkles is suppressed. This is because the increase in the plate thickness of the top plate portion 11 caused by the material leaning toward the ridgeline portions when forming the curved portions 14L and 14R is caused by the formation of the beads 16L and 16R. This is because the amount of increase in the plate thickness of the top plate portion 11 is reduced.

Further, in the press-formed product 1 manufactured by the processing method, a part of the material constituting the first beads 71L, 71R moves toward the curved portions 14L, 14R and the curved portions 14L, 14R and A decrease in plate thickness of the flange portions 13L and 13R is suppressed. As a result, it is possible to suppress the occurrence of cracks that are particularly likely to occur in the flange portions 13L and 13R.

[2. Other embodiments]
Although the embodiments of the present disclosure have been described above, the present disclosure is by no means limited to the above-described embodiments, and needless to say, can take various forms as long as they fall within the technical scope of the present disclosure.

(2A) In the above embodiment, the press-formed product 1 including the top plate portion 11, the vertical wall portions 12L and 12R, and the flange portions 13L and 13R was exemplified. However, the press-formed product may not have the flange portion. In addition, as long as the press-formed product includes the curved portion and bead of the present disclosure, the specific shape of the top plate portion, the flange portion, and the vertical wall portion excluding the curved portion is not particularly limited, and various shapes and structures are possible. can be applied to press-molded products.

(2B) In the above embodiment, the configuration including the two curved portions 14L and 14R was exemplified, but the number of curved portions is not particularly limited. One or more may be provided. In the press-formed product 1, the configuration in which the curved portion 14L is provided at the portion where the main plate portion 11a and the lower portion 11c intersect has been exemplified. may be provided.

(2C) In the above embodiment, the press-formed product 1 is used for the center pillar. Also, the press-molded product of the present disclosure may be used for applications other than center pillars. Of course, you may use it other than the vehicle body.

(2D) A plurality of functions possessed by one component in the above embodiment may be realized by a plurality of components, or a function possessed by one component may be realized by a plurality of components. . Also, a plurality of functions possessed by a plurality of components may be realized by a single component, or a function realized by a plurality of components may be realized by a single component. Also, part of the configuration of the above embodiment may be omitted. Moreover, at least part of the configuration of the above embodiment may be added or replaced with respect to the configuration of the other above embodiment. It should be noted that all aspects included in the technical idea specified only by the wording described in the claims are embodiments of the present disclosure.

REFERENCE SIGNS LIST 1 Press-formed product 11 Top plate portion 11a Main plate portion 11b Upper side portion 11c Lower side portion 11d Upper end side portion 12L, 12R Vertical wall portion 13L, 13R Flange portion 14L , 14R, 141L, 141R... curved portion, 15L, 15R, 151L, 151R... edge line, 16L, 16R... bead, 17... recessed portion, 31... monocoque structure, 33... center pillar, 41... blank material, 51, 61, 62 Upper mold 52, 64 Lower mold 53, 54 Die 55 Groove 56 Projection 63 Pad 71L, 71R First bead 81, 82, 83, 84 Corner

Claims (1)

A press working method for a press-formed product comprising a top plate portion, a vertical wall portion bent from the top plate portion and extending in a direction intersecting the top plate portion, and a flange portion connected to the vertical wall portion There is
The press-formed product is a curved portion that is a part of the vertical wall portion, and a ridgeline formed between the curved portion and the top plate portion is curved toward the inside of the top plate portion. having a department,
forming a curved first bead on the blank;
By bending the position where the first bead is formed, the curved portion is formed so that a portion of the first bead is included in the curved portion, and the portion of the first bead and the portion of the first bead are bent. is a second bead having a height smaller than that of the first bead.

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