JP2023102761A - Method of manufacturing press-formed article - Google Patents

Abstract

To provide a method of manufacturing a press-formed article that can obtain a press-formed article of a target shape without causing breakage of a junction of blanks that are stacked after press-forming.SOLUTION: A method of manufacturing a press-formed article 1 is for manufacturing a press-formed article 1 of a target shape having a U-shaped cross-sectional shape or a hat-shaped cross-sectional shape by stacking a plurality of blanks made of metal plates followed by press-forming, includes: a first forming step of forming a pre-formed blank 15 provided with a convex shape 13 extending in a ridge direction of bending, on a blank arranged outside of bending in a bent part in the press-forming; a joint blank preparing step of joining a blank arranged inside of bending in the bent part in the press-forming to a surface opposite a surface on which the convex shape 13 in the pre-formed blank 15 has been formed, and preparing a joint blank 25; and a second forming step of press-forming the joint blank 25 into the target shape by arranging the joint blank 25 in a metal mold 11 such that the convex shape 13 of the joint blank 25 lies outside of the bending.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a method for producing a press-formed product having a U-shaped cross-section or a hat-shaped cross-section, and more particularly to a method for producing a press-formed product by stacking and press-forming a plurality of blanks.

As for automobile bodies, further strengthening of the body frame parts is progressing due to stricter collision safety standards. For example, pillars of automobiles are important parts for protecting passengers in the cabin in the event of a collision, and are required to be strong enough to withstand the impact load. Therefore, high-strength materials such as high-strength steel sheets are being applied to these parts.

If the body frame parts such as pillars that make up the cabin are made thicker in order to improve strength, the weight of the body will increase, reducing the fuel efficiency of the vehicle and increasing the amount of carbon dioxide emissions.

Therefore, it is conceivable to reinforce the necessary parts rather than the entire part.
Since the load at the time of collision is mainly transmitted through the ridgeline of the bend of the part, the body frame parts are often partially reinforced by adding reinforcing parts to a part of the vicinity of the ridgeline of the bend.
In order to manufacture such a partially reinforced part, for example, the main body part and the reinforcing part are press-molded, and then joined in a subsequent process.
However, in this method, it is necessary to separately prepare a mold for the main body part and a mold for the reinforcing part, and perform press molding separately.

On the other hand, as described in Patent Document 1 and Patent Document 2, for example, there is a press molding method called patchwork in which a main body part blank and a reinforcing part blank are joined in an overlapping state in advance, and the joined blanks overlapped and joined are press-molded with one mold. According to this patchwork, the main body part and the reinforcing part can be integrally press-molded, so that the mold manufacturing cost and the number of press-molding man-hours can be reduced.
In addition, compared to a press-formed product in which a main body part and a reinforcing part are separately press-formed and then joined together, a press-formed product produced by patchwork press-forming has the main body part and the reinforcing part in close contact with each other.

Patent document 1 is a manufacturing method in which blanks are superimposed by hot pressing, in which blanks are heated, press-molded, and at the same time, quenched by quenching with a mold.
In addition, in Patent Document 1, the blanks are provided with protrusions, but these protrusions are for forming a space for escaping Zn vapor generated from the blank (plated plate) in order to prevent surface cracks that occur when the blanks are overlapped and heated.

In addition, Patent Document 2 discloses that in order to reduce misalignment between the overlapped blanks during press molding, the overlapped blanks are bent in the same direction as the bending direction of the press-formed product, then joined and press-formed.

Japanese Patent Application Laid-Open No. 2013-184221 JP 2020-121336 A

The hot press disclosed in Patent Literature 1 has low production efficiency due to the high blank heating cost and the need for rapid cooling time.
Therefore, in recent years, cold press forming has been performed using ultra-high tensile steel sheets for cold press, such as 1470 MPa grade, which can reduce heating costs and improve production efficiency.
However, in cold press forming by patchwork, since the cross-sectional line length differs between the inner side of the bend and the outer side of the bend at a bent portion such as the punch shoulder R, a shift occurs between the blanks that are overlapped during press forming, and the joints that are previously joined by overlapping the blanks may break during press forming.

In this regard, as disclosed in Patent Document 2, by bending the superimposed blanks in the same direction as the bending direction of the press-formed product, and then joining and press-forming the blanks, it is possible to reduce misalignment during press-forming between the superimposed blanks.
However, in the method of Patent Document 2, since the two blanks are bent using a plurality of jigs, it is not possible to apply deformation corresponding to a large bending angle between the top plate portion and the vertical wall portion during press molding.
As a result, it is conceivable that the gap between the stacked blanks during press molding cannot be sufficiently eliminated, and the joint may break.

The present invention has been made in order to solve such problems, and it is an object of the present invention to provide a method of manufacturing a press-formed product that can obtain a press-formed product of a target shape without sufficiently eliminating the deviation during press-forming between stacked blanks using a steel plate for cold press forming, and without causing breakage at the joint after press-forming.

Prior to describing specific means, deviations that occur between blanks that are overlapped by patchwork during press molding will be described with reference to FIGS. 11 and 12. FIG.

FIG. 11 shows an example of a press-formed product 1 manufactured by patchwork and composed of a main body part 3 having a hat-shaped cross section and a reinforcing part 5 having a U-shaped cross section disposed inside the main body part 3. FIG. 11(a) is a perspective view, and FIG. The reinforcing part 5 forms a ridgeline part 27 so as to cover both punch shoulder R parts 1c (see FIG. 12(b)) of the main body part 3, is arranged over both vertical wall parts 1b, and is joined to the main body part 3 by the spot welding part 6. In FIG. 11, the drawing of the R shape of the punch shoulder R portion 1c is omitted for the sake of simplification of the drawing.
FIG. 12 is an enlarged view of the portion corresponding to the punch shoulder R portion in the blank before press forming (FIG. 12(a)), and an enlarged view of the punch shoulder R portion 1c extending from the top plate portion 1a to the vertical wall portion 1b after press forming (FIG. 12(b)). Let t ₁ be the thickness of the body blank 7 that will be the main body part 3 , and t ₂ be the thickness of the reinforcement blank 9 that will be the reinforcement part 5 .
In this specification, when the punch shoulder R portion 1c is simply indicated, it basically refers to the part of the press-formed product 1 formed by the punch shoulder R portion 11c of the die 11, and when referring to the punch shoulder R portion of the die, it is referred to as "the punch shoulder R portion 11c of the die 11".

If two flat blanks are pressed together without being joined together, the cross-sectional line length of the main body blank 7 located on the outer side of the punch shoulder R portion 1c (between AB) becomes longer, and if the positions of the two blanks are the same on the top plate portion 1a, the portions S1 and S2 corresponding to the vertical walls of the overlapped blanks are shifted by ΔL (see FIG. 12(b)). This ΔL is the cross-sectional line length difference between the main body blank 7 and the reinforcing blank 9 after press molding.

This .DELTA.L changes due to deformation due to expansion and contraction of the blank, but if such deformation is not considered, it can be geometrically calculated from the thickness of the blank and the shape of the mold.
Let θ (radian) be the angle formed between the top plate portion 11a and the vertical wall portion 11b at the punch shoulder R portion 11c of the die 11 _, R (mm) be the radius of the punch shoulder R portion 11c of the die 11, and _R1 (mm) and _R2 (mm) be the radii of the punch shoulder R portion 1c at the plate thickness center of the body blank 7 and the reinforcing blank 9 respectively. ), and the cross-sectional line length L ₂ (mm) at the thickness center of the reinforcing blank 9 is
L ₁ =R ₁ θ, L ₂ =R ₂ θ (1)
can be expressed as

Also, _R1 =R+ _t1 /2+ _t2 , _R2 =R+ _t2 /2 (2)
becomes.
Hereinafter, the cross-sectional line length indicates the cross-sectional line length at the center of the plate thickness.
Assuming that there is no expansion or contraction in the cross-sectional line lengths of the main body blank 7 and the reinforcing blank 9, the geometrical cross-sectional line length difference ΔL ^* between the main body blank 7 and the reinforcing blank 9 can be expressed as follows.
ΔL ^* = _L1 - _L2 =( _R1 - _R2 )θ=( _t1 + _t2 )θ/2 (3)
As can be seen from the formula (3), the greater the plate thickness of the main body blank 7 and the reinforcing blank 9, and the greater the angle formed between the top plate portion 1a and the vertical wall portion 1b, the greater the cross-sectional line length difference ΔL ^* .

In this way, press forming causes a difference in cross-sectional line length between the main body blank 7 and the reinforcing blank 9, and this difference in cross-sectional line length causes a deviation between the thickness centers of the blanks. Therefore, it is necessary to minimize the cross-sectional line length difference between the main body blank 7 and the reinforcing blank 9 after press forming.
In this regard, if the body blank 7 and the reinforcement blank 9 can be joined while ensuring the cross-sectional line length in the target shape of the body blank 7 and the reinforcement blank 9, the joint portion of the body blank 7 and the reinforcement blank 9 will not be misaligned during press molding.
Therefore, as a result of intensive studies, the inventors have found that the main body blank 7, which is located outside the bending of the punch shoulder R portion 1c and has a long cross-sectional line length, is preformed so that the cross-sectional line length becomes long before joining the main body blank 7 and the reinforcing blank 9, thereby eliminating the difference in cross-sectional line length when forming into a target shape. The present invention is based on such findings, and specifically has the following configuration.

(1) A method for producing a press-formed product according to the present invention is a method for producing a press-formed product having a target shape having a U-shaped cross-sectional shape or a hat-shaped cross-sectional shape by stacking and press-molding a plurality of blanks made of metal plates,
A first forming step of forming a preformed blank in which a convex shape extending in the direction of the ridge line of the bend is imparted to the blank arranged on the outside of the bend in the bent portion in the press forming;
A bonded blank creating step of creating a bonded blank by bonding a blank disposed inside the bend in the bent portion in the press molding to the surface of the preformed blank opposite to the surface on which the convex shape is formed;
and a second forming step of arranging the convex shape of the joint blank on the outside of the bend in a mold and press-molding it into a target shape.

(2) Further, in the method described in (1) above, the convex shape in the preformed blank is formed at a portion that becomes a bending ridge in the press-formed product of the target shape.

(3) In addition, in the above (1) or (2), the convex shape in the preformed blank is formed so as to be parallel to the bending ridge line in the press-formed product of the target shape.

(4) In the above (1) to (3), the convex shape of the preformed blank is shorter than the bent ridge line of the press-formed product of the target shape.

(5) In addition, in the above (1) to (4), the bending angle between the top plate portion and the vertical wall portion at the bending ridge in the target shape is θ, the thickness of the preformed blank is t ₁ , the thickness of the blank to be joined to the preformed blank is t ₂ , and the length of the thickness center of the convex shape in the cross section of the preformed blank connecting the starting point and the end point of the convex with a straight line and the length of the thickness center connecting with a curve along the convex. It is characterized by satisfying the formula:
0.3( _t1 + _t2 )θ≦ΔL≦0.7( _t1 + _t2 )θ

ADVANTAGE OF THE INVENTION According to this invention, the fracture|rupture of the joint part which is a problem by patchwork of a cold press can be suppressed, and a press-formed product can be manufactured stably and efficiently.

It is explanatory drawing of each process of the manufacturing method of the press-formed product which concerns on embodiment. It is explanatory drawing of the preforming blank shape|molded by the 1st shaping|molding process of embodiment. It is explanatory drawing explaining convex-shaped arrangement|positioning in a preforming blank (part 1). It is explanatory drawing explaining convex-shaped arrangement|positioning in a preforming blank (the 2). It is explanatory drawing explaining convex-shaped arrangement|positioning in a preforming blank (the 3). It is explanatory drawing of the cross-sectional line length difference before and behind shaping|molding of the convex shape formed in a preforming blank. FIG. 4 is an explanatory diagram of parameters for shape modification of a convex shape formed in a preformed blank; It is explanatory drawing of the joint blank produced by the joint blank production process of embodiment. FIG. 4 is an explanatory view of another aspect of the press-formed product manufactured by the present invention; It is explanatory drawing of the press-formed article manufactured in the Example. It is explanatory drawing explaining the subject of this invention (part 1). It is explanatory drawing explaining the subject of this invention (part 2). It is explanatory drawing of other forms of the joint blank produced by the joint blank production process of embodiment (the 2). It is explanatory drawing of the other form of the joint blank produced by the joint blank production process of embodiment (the 3). It is a figure which applied the reinforcement component to the center pillar. It is a figure which applied the reinforcement component to the front pillar.

The method of producing a press molded product according to the embodiment is a method of manufacturing a press molding product that manufactures a target shape of a target shape or hat -shaped surface shape (see FIG. 1 (D)) with a multiple blanks consisting of a metal plate, and the method of manufacturing a press molding product 1 (D)). A) Refer), a joint blank creation process (see FIG. 1 (B)), and a second molding step (see FIG. 1 (C)).
The press-formed product 1 of the present embodiment, similar to that shown in FIG. 11, is obtained by joining a reinforcing component 5 having a U-shaped cross section to the inside of a main body component 3 having a hat cross-sectional shape (see FIG. 1(d)).
In FIG. 1, the same parts as those in FIGS. 11 and 12 are denoted by the same reference numerals.
Each step will be described in detail below.

<First molding step>
The first forming step is a step of forming a preformed blank 15 in which a convex shape 13 extending in the direction of the ridge line 27 of the bend is imparted to the body blank 7 arranged on the outer side of the bend in the bent portion in the press forming.
The mold 11 used in the first molding step is composed of a convex mold 19 having a convex streak portion 17 and a concave mold 23 having a concave streak portion 21, as shown in FIG. 1(a). The main body blank 7 is set between the convex mold 19 and the concave mold 23, and the convex mold 19 or the concave mold 23 is relatively moved to sandwich the main body blank 7 for molding.
The vertical arrangement of the convex mold 19 and the concave mold 23 does not matter, and either of them may be arranged above or below.
FIG. 2 shows an example of the preformed blank 15 produced in this process.

The portion where the convex shape 13 is imparted to the main body blank 7 in the first forming step is preferably a portion corresponding to the punch shoulder R portion 1 c in the target shape of the press-formed product 1 .
The reason is as follows.
Since the material is greatly deformed at the punch shoulder R portion 1c during press molding, the convex shape 13 provided at the portion corresponding to the punch shoulder R portion 1c is crushed, and the cross-sectional line length can be lengthened along the punch shoulder R portion 1c, easily eliminating the cross-sectional line length difference between the main body blank 7 and the reinforcement blank 9, and preventing the occurrence of cracks due to misalignment of the joint portion.

On the other hand, if the convex shape 13 is given to the part of the main body blank 7 corresponding to the flat portion such as the top plate portion 1a and the vertical wall portion 1b of the press-formed product 1 shown in FIG.
Therefore, as shown in FIG. 3, by setting the convex shape 13 within the range of the punch shoulder R portion 1c of the target shape, the convex shape 13 can be flattened and the bending tendency can be reduced. That is, the punch shoulder R portion 1c of the target shape may be set within the range indicated by the arrow, as shown in FIG.
Further, even if a part of the convex shape 13 overlaps the punch shoulder R portion 1c as shown in FIG. 4 or 5, the convex shape 13 can be flattened and the bending tendency can be reduced. 4(a) or 5(a) of the convex shape 13 of the preformed blank 15 before forming, and as shown in FIG. 4(b) or FIG.

Next, the cross-sectional line length of the convex shape 13 imparted to the main body blank 7 in this step will be described.
FIG. 6 shows cross-sectional shapes of the main body blank 7 before the projecting shape 13 is provided and the preformed blank 15 provided with the projecting shape 13 in this step. L ₀ is the cross-sectional line length between A1 and B1 (the length of the broken line connecting ● and ●) of the main body blank 7 before the convex shape 13 is given, and L is the cross-sectional line length between A2 and B2 (the length of the broken line connecting ● and ●) of the preformed blank 15 to which the convex shape 13 is given.
By providing the convex shape 13, the cross-sectional line length of the preformed blank 15 becomes longer than that of the main body blank 7 before forming (L>L ₀ ), and the cross-sectional line length difference ΔL (=L−L ₀ ) before and after the convex shape 13 is provided may be absorbed by press forming by bending the punch shoulder R portion 1c in the second forming step.

In order to prevent misalignment at the joint between the main body blank 7 and the reinforcing blank 9 during press molding, the difference in cross-sectional line length ΔL between before and after the convex shape 13 is imparted should be the same as ΔL ^* (ΔL=ΔL ^* ) shown in the above-described formula (3) shown below.
ΔL ^* = _L1 - _L2 =( _R1 - _R2 )θ=( _t1 + _t2 )θ/2 (3)

However, ΔL ^* shown in Equation (3) does not take into account deformation due to expansion and contraction of the blank. Since the blank deforms in the in-plane direction when an external force is applied, the cross-sectional line length difference ΔL has an optimum range in which cracks do not occur in the joint during press molding.
As a result of examining the preferable range of the cross-sectional line length difference ΔL, the inventors found that ΔL should be ±40% of the value of ΔL ^* shown in formula (3), that is, within the range of 0.6 to 1.4 times.
Therefore, the cross-sectional line length difference ΔL falls within the range shown by the following formula (4).
0.3 (t ₁ +t ₂ ) θ≦ΔL≦0.7 (t ₁ +t ₂ ) θ (4)

Therefore, it is preferable to design and manufacture a preforming mold that gives the convex shape 13 having the cross-sectional line length difference ΔL in this preferred range, and perform the first forming step.
The cross-sectional line length of the convex shape 13 can be adjusted by changing the height h and the width w between the plate thickness centers of the convex shape 13 shown in FIG.

It is desirable that the direction in which the convex shape 13 extends is parallel to the bending ridgeline. Even if a tensile load is generated in the direction orthogonal to the bending ridge line when bending is performed, the convex shape 13 is bent and stretched, thereby preventing displacement of the joint.
As an example of the length of the ridgeline direction of the convex shape 13, it may be the entire length of the bent ridgeline portion 27, that is, the entire length of the preformed blank 15 as shown in FIG. Also, as shown in FIG. 14, both the preformed blank 15 and the reinforcing blank 9 may not extend over the entire length.

Here, an example of application of the present invention to a vehicle body frame component will be shown.
FIG. 15 shows an arrangement example of the main body part 3 and the reinforcing part 5 when the main body part 3 is a center pillar, and FIG. 16 is a front pillar. In general, from the viewpoint of weight reduction, the reinforcing parts 5 arranged in a patchwork often have short dimensions such that they form part of the main body part 3 in the longitudinal direction. The convex shape 13 given to the main body blank 7 only needs to be in the vicinity of the joint with the reinforcing part 5 in order to prevent the joint from slipping, and the convex shape 13 is not necessarily required at the ridge line part 27 where the reinforcing part 5 does not exist. From the above, it is preferable that the convex shape 13 provided to the main body blank 7 is shorter than the bending ridgeline portion 27 of the main body component 3 as shown in FIGS. 13 and 14 .

<Joining blank creation process>
As shown in FIGS. 1(b) and 8, the joining blank creation step is a step of creating a joining blank 25 by joining a reinforcing blank 9 arranged on the surface of the preformed blank 15 opposite to the surface on which the convex shape 13 is formed, inside the bend in the bending portion in press molding.
Any method for joining metal plate blanks, such as resistance spot welding, arc welding, laser welding, seam welding, and mechanical joining, can be applied here.

<Second molding step>
In the second forming step, as shown in FIG. 1(c), the convex shape 13 of the joint blank 25 is placed on the die 11 so as to be outside the bend, and press-molded into the target shape.
In this step, as shown in FIGS. 3 to 5, the convex shape 13 is crushed and absorbed during the forming process of the punch shoulder R portion 1c, and the portion of the preformed blank 15 where the convex shape 13 was formed contacts the reinforcing blank 9.
Therefore, there is no difference in the cross-sectional line length of the portion corresponding to the punch shoulder R portion 1c in the preformed blank 15 before and after forming, and no deviation occurs between the preformed blank 15 and the reinforcing blank 9 of the joined vertical wall portion.
The molding method of the second molding step may be foam molding or draw molding.
Also, in the second forming step, a plurality of press formings may be performed in order to form the target shape.

As described above, according to the present invention, it is possible to stably and efficiently manufacture the press-formed product 1 by suppressing breakage of the joints, which is a problem in cold-press patchwork.

The present invention can be suitably applied to press molding of collision-resistant parts made of ultra-high-strength materials such as front pillars, center pillars and floor cloths.
Further, the press-formed product 1 to which the present invention can be applied may have a structure in which the reinforcing part 5 is arranged inside the main body part 3 as shown in FIGS.
The blanks to be formed into the press-formed product 1 include not only steel plates but also metal plates such as aluminum alloy plates, magnesium alloy plates, and titanium alloy plates. Also, there is no restriction on the strength of the blank.

The effects of the method of the present invention were investigated by carrying out specific press molding experiments, and one example will be described below.
As shown in FIG. 10, the shape of the press-formed product 1, which is the target shape, is composed of a main body part 3 having a hat-shaped cross section and a reinforcing part 5 having a U-shaped cross section. In addition, the U-shaped cross-sectional reinforcement component 5 is arranged over both vertical wall portions 1b so as to cover both punch shoulder R portions 1c of the main body component 3 .

The body blank 7 formed into the main body part 3 is a 590 MPa class steel plate having a thickness of 1.0 mm, and the reinforcing blank 9 formed into the reinforcing part 5 is a 1470 MPa class steel plate having a thickness of 1.4 mm. The angle θ formed between the top plate portion 1a and the vertical wall portion 1b at the punch shoulder R portion 1c of the press-formed product 1 is 80° (approximately 1.39 radians), and the bending radius R of the punch shoulder R portion 1c is 7 mm.
The main body part 3 and the reinforcing part 5 were joined at each vertical wall portion 1b by spot welds 6 that were multi-point welded in the longitudinal direction of the parts with a pitch of 40 mm between the centers of the welding points (see FIG. 10(c)).

The manufacturing process of the press-formed product 1 of the present invention is as shown in FIG. 1 described in the above embodiment. That is, in the first forming step, the main body blank 7 is given a convex shape 13, and then in the joint blank creation step, the preformed blank 15 provided with the convex shape 13 and arranged on the outside (opposite side of the surface where the blanks are superimposed) and the flat reinforcing blank 9 are joined by the multi-point spot welds 6 to create a joint blank 25 (see FIG. 8), and in the second forming step, formed into a target shape by foam molding.

Regarding the convex shape 13 formed in the first forming step, the geometric optimum value ΔL ^* of the cross-sectional line length difference ΔL that can avoid the cracking of the joint when forming the press-formed product 1 of the target shape is ΔL ^* =1.67 mm from the formula (3) using the thickness of the main body blank 7, the thickness of the reinforcing blank 9, and the bending angle of the top plate portion 1a and the vertical wall portion 1b at the punch shoulder R portion 1c of the press-formed product 1.

In the example of the present invention, six levels of preformed blanks 15 with different cross-sectional line lengths were produced by changing the height and width of the plate thickness center of the convex shape 13 imparted to the main body blank 7 in the first forming step. Then, the joint blank preparation process and the second forming process were carried out, and the presence or absence of cracks in the spot welded portion 6 under each condition was evaluated.
Further, as a conventional example, the first forming step was omitted, and in the joint blank forming step, flat blanks were overlapped and joined to form a joint blank, and press molding was performed in the second forming step.

Table 1 shows the height h and width w of the thickness center of the convex shape 13 imparted to the main body blank 7 under each condition of the conventional example and the example of the present invention (Fig. 7), the cross-sectional line length difference ΔL between the thickness center of the main body blank 7 before and after the convex shape 13 is imparted, and the geometric cross-sectional line length difference ΔL ^* that does not cause a deviation between the thickness center of the main body blank 7 and the thickness center of the reinforcing blank 9 in the vertical wall portion joined in the second forming process ((ΔL-ΔL ^* )/ΔL). ^* ), and the results of the presence or absence of cracks in the joints of the press-formed product 1 are shown.

In the conventional example, since the body blank 7 was not preformed, a gap (approximately 1.67 mm) occurred between the body blank 7 and the reinforcing blank 9 in the second forming process, and cracks occurred in all joints joined at multiple points.
In Example 1 of the present invention, preforming was performed on the main body blank 7, but the cross-sectional line length difference ΔL after press forming was 0.7 mm, which is 58% shorter than the optimum value ΔL ^* with no deviation. Therefore, the cross-sectional line length difference during press forming could not be absorbed sufficiently, and cracks occurred in a part (20%) of the joints joined at multiple points.
On the other hand, in Examples 2 to 5 of the present invention, the error with ΔL ^* was within 40%, and cracks did not occur in the joint portion of the press-formed product 1 .
In addition, in Inventive Example 6, the cross-sectional line length difference ΔL after press molding was 2.5 mm, which was 50% longer than the optimal value ΔL ^* with no deviation. Therefore, in the second forming process, the cross-sectional line length of the main body blank 7 was excessive, and deviation occurred in the opposite direction to the conventional example and invention example 1, and as a result, cracks occurred in a portion (10%) of the joint portion.

From the above, it was found that the present invention can suppress breakage of joints, which is a problem in cold press patchwork, and can stably and efficiently produce the press-formed product 1 .

1 press-formed product 1a top plate portion 1b vertical wall portion 1c punch shoulder R portion 3 main body component 5 reinforcement component 6 spot welded portion 7 main body blank 9 reinforcement blank 11 mold 11a top plate portion 11b vertical wall portion 11c punch shoulder R portion 13 convex shape 15 preformed blank 17 convex portion 19 convex mold 21 concave portion 23 Concave mold 25 Joining blank 27 Ridge line

Claims (9)

A press-formed product manufacturing method for producing a press-formed product having a target shape having a U-shaped cross-sectional shape or a hat-shaped cross-sectional shape by stacking and press-molding a plurality of blanks made of metal plates,
A first forming step of forming a preformed blank in which a convex shape extending in the direction of the ridge line of the bend is imparted to the blank arranged on the outside of the bend in the bent portion in the press forming;
A bonded blank creating step of creating a bonded blank by bonding a blank disposed inside the bend in the bent portion in the press molding to the surface of the preformed blank opposite to the surface on which the convex shape is formed;
A method of manufacturing a press-formed product, comprising: a second forming step of placing the convex shape of the joint blank in a mold so as to be on the outside of the bend, and press-forming into a target shape. 2. The method of manufacturing a press-formed product according to claim 1, wherein the convex shape in the preformed blank is formed at a portion that will be a bending ridge in the press-formed product of the target shape. 3. The method of manufacturing a press-formed product according to claim 1, wherein the convex shape of the preformed blank is formed so as to be parallel to the bending ridgeline of the target-shaped press-formed product. 3. The method of manufacturing a press-formed product according to claim 1, wherein the convex shape of the preformed blank is shorter than the bending ridgeline of the target-shaped press-formed product. 4. The method of manufacturing a press-formed product according to claim 3, wherein the convex shape of the preformed blank is shorter than the bending ridgeline portion of the target-shaped press-formed product. 3. The press-formed product according to claim 1 or 2, wherein the bending angle between the top plate portion and the vertical wall portion at the bending ridge in the target shape is θ, the plate thickness of the preformed blank is _t1 , the plate thickness of the blank joined to the preformed blank is _t2 , and the cross-sectional line length difference ΔL between the length of the plate thickness center connecting the start point and the end point of the projection in the section of the preformed blank and the length of the plate thickness center connecting the projection with a curve along the projection satisfies the following formula. manufacturing method.
0.3( _t1 + _t2 )θ≦ΔL≦0.7( _t1 + _t2 )θ 4. Manufacture of the press-formed product according to claim 3, wherein the bending angle between the top plate portion and the vertical wall portion at the bending ridge portion in the target shape is θ, the plate thickness of the preformed blank is t ₁ , the plate thickness of the blank joined to the preformed blank is t ₂ , and the cross-sectional line length difference ΔL between the length of the plate thickness center connecting the starting point and the end point of the protrusion in the section of the preforming blank and the length of the plate thickness center connecting with a curve along the protrusion satisfies the following formula. How.
0.3( _t1 + _t2 )θ≦ΔL≦0.7( _t1 + _t2 )θ 5. Manufacture of the press-formed product according to claim 4, wherein the bending angle between the top plate portion and the vertical wall portion at the bending ridge in the target shape is θ, the plate thickness of the preformed blank is t ₁ , the plate thickness of the blank to be joined to the preformed blank is t ₂ , and the cross-sectional line length difference ΔL between the length of the plate thickness center that connects the start point and the end point of the protrusion with a straight line in the section of the preformed blank and the length of the plate thickness center that connects with a curve along the protrusion satisfies the following formula. How.
0.3( _t1 + _t2 )θ≦ΔL≦0.7( _t1 + _t2 )θ The bending angle between the top plate portion and the vertical wall portion at the bending ridge in the target shape is θ, the plate thickness of the preformed blank is t ₁ , the plate thickness of the blank to be joined to the preformed blank is t ₂ , and in the cross section of the convex shape in the preformed blank, the length of the thickness center that connects the start point and the end point of the protrusion with a straight line and the thickness center length of the thickness center that connects the protrusion with a curve along the protrusion satisfies the following formula. How.
0.3( _t1 + _t2 )θ≦ΔL≦0.7( _t1 + _t2 )θ

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