JP5664704B2 - Press forming method - Google Patents

Description

    The present invention relates to a press molding method for molding a part having an L-shaped part or a T-shaped part in plan view, which is a press-molded part used as, for example, a vehicle body frame part of an automobile.

When products with L-shaped parts or T-shaped parts such as front pillar reinforcements and center pillar reinforcements, which are car body skeleton parts, are manufactured from metal plates by press molding, usually the drawing method is adopted. The
Drawing is usually performed using a die consisting of a punch, die, and blank holder (claw presser), and the distance between the punch and die is reduced with the die and blank holder all around the metal plate. This is a method of drawing a metal plate.

  In such drawing, wrinkles are likely to occur in the L-shaped part or T-shaped part top plate that is bent sharply, and the die and blank holder are used to suppress the wrinkles. As the force is increased, cracking of the parts tends to occur at the shoulders of the mold and the vertical wall of the parts. In particular, in recent years, the strength of the metal plate used as a molding material has been increasing in order to improve the safety and weight of automobile bodies, and such a high-strength metal plate is as soft as a conventionally used soft steel plate. Therefore, countermeasures against cracks and flaws during press forming are important.

In order to deal with such a problem, the techniques proposed so far have undergone multiple press molding processes in which a die is exchanged and then bending is performed after drawing to form an L-shaped part. A method of forming a final product shape has been proposed (see, for example, Patent Document 1).
In addition, a press molding method of a skeleton member having an L-shaped portion using a die unit including a die die, a pad, and a bending die has been proposed (for example, see Patent Document 2).

WO2012 / 070623 WO2011 / 145679

However, the method as disclosed in Patent Document 1 has a problem that the cost increases because the number of molding steps increases.
Further, in the method of Patent Document 2, there is no problem when the flanges of the parts are substantially on the same plane, but the flange shape is three-dimensionally bent in accordance with the curved surface shape of the vehicle body such as a center pillar reinforcement. In such a case, the occurrence of wrinkles becomes more prominent in the part flange than in the conventional drawing at a place other than the L-shaped part (a place corresponding to the straight part in FIG. 1 or FIG. 2 of Patent Document 2). There was a problem.

  The present invention has been made in order to solve the above-described problems, and in a part having an L-shaped part or a T-shaped part even if an ultra-high strength high tensile material with low ductility is used, a molding process An object of the present invention is to provide a press molding method capable of suppressing wrinkles and avoiding cracks without increasing the number.

(1) A press molding method according to the present invention cooperates with a punch having a molding surface, a die having a molding surface corresponding to the punch, a blank holder for sandwiching a metal plate between the die, and the punch. The metal plate using a press mold having a pad for sandwiching a part of the metal plate, the top plate portion, a vertical wall portion formed around the top plate portion, and the vertical wall A press forming method comprising press forming a part having an L-shaped part in a plan view.
A metal plate disposing step of disposing the metal plate so as not to cover the blank holder at a portion corresponding to an end of the L-shaped short side of the metal plate;
A metal plate sandwiching step of sandwiching the metal plate placed on the blank holder by the metal plate placement step between the die and the blank holder;
A molding step of pressing the punch against the metal plate held between the die and the blank holder to mold the metal plate by drawing,
After the metal plate clamping step, there is a pad pressing step for pressing a position including at least an L-shaped bent portion of a portion corresponding to the top plate portion of the metal plate by the punch and the pad during the forming step. And
The pad pressing process starts at a position of 0% to 50% with respect to the forming depth from the position at which the punch in the forming process starts to contact the metal plate to the bottom dead center position,
The average pressure for holding the metal plate with the die and the blank holder in the metal plate clamping step is 0.7 MPa or more,
An average pressure for pressing the metal plate with the punch and the pad in the pad pressing step is 3 MPa or more.

(2) A press molding method according to the present invention includes a punch having a molding surface, a die having a molding surface corresponding to the punch, a blank holder for sandwiching a metal plate between the die, and a punch. The metal plate using a press mold having a pad that sandwiches a part of the metal plate in cooperation, the top plate portion, a vertical wall portion formed around the top plate portion, A press-molding method comprising press-molding a part having a T-shaped part in plan view, comprising a flange part formed continuously on a vertical wall part,
A metal plate disposing step of disposing the metal plate so as not to cover the blank holder at a portion corresponding to the end of the T-shaped lateral side of the metal plate;
A metal plate sandwiching step of sandwiching the metal plate placed on the blank holder by the metal plate placement step between the die and the blank holder;
A molding step of pressing the punch against the metal plate held between the die and the blank holder to mold the metal plate by drawing,
After the metal plate clamping step, a position including at least a T-shaped horizontal side and vertical side connection portion of a portion corresponding to the top plate portion of the metal plate is pressed by the punch and the pad during the molding step. A pad presser process,
The pad pressing process starts at a position of 0% to 50% with respect to the forming depth from the position at which the punch in the forming process starts to contact the metal plate to the bottom dead center position,
The average pressure for holding the metal plate with the die and the blank holder in the metal plate clamping step is 0.7 MPa or more,
An average pressure for pressing the metal plate with the punch and the pad in the pad pressing step is 3 MPa or more.

In the present invention, in the metal plate arranging step, the portion corresponding to the end portion of the L-shaped short side of the metal plate is arranged so as not to cover the blank holder, and in the metal plate holding step, the metal plate is held between the die and the blank holder. In the molding process, the punch is pressed against the metal plate to form the metal plate by drawing. After the metal plate clamping process in the pad pressing process, the punch and pad correspond to the top plate portion of the metal plate during the molding process. The position including the L-shaped bent portion of the part to be pressed is pressed, and the pad pressing process starts from 0% with respect to the forming depth from the position where the punch in the forming process starts to contact the metal plate to the bottom dead center position. Starting at the 50% position, the blank holder pressure in the metal plate clamping process is 0.7 MPa or more, and the pad pressure in the pad pressing process is 3 MPa. It was above.
As described above, in press molding of a part having an L-shaped part, even if an ultra-high strength high-tensile material with low ductility is used as a metal plate, suppression of cracks and cracking are avoided without increasing the number of molding processes. Can do.

It is explanatory drawing explaining the press molding method which concerns on one embodiment of this invention. It is a top view of the L-shaped component which is a molding object of the press molding method which concerns on one embodiment of this invention. It is an enlarged view of the AA arrow cross section of the L-shaped component shown in FIG. It is explanatory drawing explaining the press molding die used with the press molding method which concerns on one embodiment of this invention. It is explanatory drawing explaining the press molding die used with the press molding method which concerns on one embodiment of this invention, Comprising: The state where the press molding die was attached to the press molding apparatus is shown. It is explanatory drawing explaining an example of the pad range in the pad pressing process of the press molding method which concerns on one embodiment of this invention (the 1). It is explanatory drawing explaining an example of the pad range in the pad pressing process of the press molding method which concerns on one embodiment of this invention (the 2). It is explanatory drawing explaining an example of arrangement | positioning of the metal plate in the metal plate arrangement | positioning process of the press molding method which concerns on one embodiment of this invention. It is a top view of the center pillar shown as an example of the component which has the T-shaped part which is the other shaping | molding object of the press molding method which concerns on other embodiment of this invention. FIG. 10 is an enlarged view of a cross section taken along the line B-B of the center pillar shown in FIG. 9. It is explanatory drawing explaining an example of arrangement | positioning of the metal plate in the metal plate arrangement | positioning process in the case of press-molding the center pillar shown in FIG. It is a top view of the front pillar which is a molding object of the press molding method concerning Example 1 of the present invention. It is an enlarged view of the CC arrow cross section of the front pillar shown in FIG. It is explanatory drawing explaining the lower metal mold | die of the press molding die used with the press molding method which concerns on Example 1 of this invention. It is explanatory drawing explaining the upper metal mold | die of the press molding die used with the press molding method which concerns on Example 1 of this invention. It is explanatory drawing of the molding conditions of the press molding method which concerns on Example 1 of this invention, Comprising: It is explanatory drawing explaining the starting position of a pad pressing process. It is explanatory drawing of the molding conditions of the press molding method which concerns on Example 1 of this invention, Comprising: It is explanatory drawing explaining arrangement | positioning of the metal plate in a metal plate arrangement | positioning process. It is explanatory drawing of the molding conditions of the press molding method which concerns on Example 1 of this invention, Comprising: It is explanatory drawing explaining the pad range in a pad pressing process. It is explanatory drawing of the molding conditions of the press molding method which concerns on Example 2 of this invention, Comprising: It is explanatory drawing explaining arrangement | positioning of the metal plate in a metal plate arrangement | positioning process.

[Embodiment 1]
A press molding method according to an embodiment of the present invention (see FIG. 1) is performed by press-molding an L-shaped part 1 shown in FIGS. 2 and 3 using a press-molding die 5 shown in FIGS. Therefore, before describing the press molding method, the L-shaped part 1 and the press mold 5 will be described.
The L-shaped part 1 will be outlined below.

As shown in FIG. 2, the L-shaped component 1 includes an L-shaped top plate portion 2 having a long side and a short side in a plan view, and a vertical wall portion 3 formed around the top plate portion 2. It has the flange part 4 formed continuously by the vertical wall part 3, and the cross section is a hat shape as shown in FIG.
The vertical wall portion 3 and the flange portion 4 are not formed at both ends of the long side of the top plate portion 2 and the end portion of the short side (short side end portion 2a).

Next, the press molding die 5 used in the press molding method according to the present embodiment will be described with reference to FIGS.
As shown in FIG. 4, the press mold 5 includes a punch 6 having a molding surface 6 a, a die 7 having a molding surface 7 a corresponding to the punch 6, and a metal plate 17 between the die 7 (see FIG. 5). ) And a pad 11 (see FIG. 5) that holds a part of the metal plate 17 in cooperation with the punch 6.
As shown in FIG. 5, the punch 6 and the blank holder 9 are attached to the bolster 13, and the die 7 and the pad 11 are attached to the slider 15.
Hereinafter, each configuration will be described in detail.

<Punch>
As shown in FIG. 4, the punch 6 has an L-shaped molding surface 6 a in plan view, and is disposed in an opening 9 a provided in the blank holder 9.

<Die>
In the center of the die 7, a recess is formed in an L shape as shown in FIG. 4, and the inner surface of the recess is a molding surface 7 a corresponding to the punch 6.
An opening 7b is provided at a position including an L-shaped bent portion on the molding surface 7a, and a pad 11 is disposed in the opening 7b (see FIGS. 5 and 6).
The lower surface of the die 7 is a clamping surface 7 c that clamps the metal plate 17 with the blank holder 9.

<Blank holder>
An opening 9a is provided at the center of the blank holder 9, and the punch 6 is disposed in the opening 9a. As shown in FIG. 5, the blank holder 9 is supported by a cushion pin 19 so as to be movable up and down. The blank holder 9 is always supported so as to be positioned above the upper surface of the punch 6 and can be pushed down by the die 7 during press molding. When the blank holder 9 is pushed down, the punch 6 protrudes relatively from the blank holder 9, and the upper part of the punch 6 is inserted into the die 7 (see FIG. 1C).

<Pad>
As shown in FIG. 5, the pad 11 is provided so as to be pressed toward the punch 6 by a gas cylinder 21 or the like, and in cooperation with the punch 6, one of the top plates 2 (see FIG. 2) in the metal plate 17. Hold the part.
As shown in FIG. 6, the shape of the pad 11 can press a portion corresponding to the bent portion 2 b (see FIG. 2) in the metal plate 17. By carrying out like this, generation | occurrence | production of the wrinkle in the bending part 2b can be suppressed. As shown in FIG. 7, wrinkles are most likely to occur in the arc D formed inside the bent portion 2b and the portion surrounded by the tangent L1 and the tangent L2 at both ends of the arc D, and the area S of the portion S It is preferable to press 80% or more.

Next, a press molding method according to the present embodiment using the above press mold will be described. In the press molding method according to the present embodiment, the metal plate 17 is disposed so that the portion corresponding to the end portion of the L-shaped short side of the metal plate 17 does not cover the blank holder 9 (FIG. 1). (See (a)), a metal plate clamping step (see FIG. 1B) for clamping the metal plate 17 placed on the blank holder 9 by the metal plate placement step between the die 7 and the blank holder 9, and the die 7 The punch 6 is pressed against the metal plate 17 held by the blank holder 9 to form the metal plate 17 by drawing. After the metal plate holding step, the punch 6 and the pad 11 are used during the forming process. A pad pressing step (see FIG. 1C) for pressing the position of the metal plate 17 including the bent portion 2b.
Each of the above steps will be described in detail below.

<Metal plate placement process>
As shown in FIG. 8, the metal plate arranging step is a step of arranging the metal plate 17 so that the portion 17 a corresponding to the short side end 2 a of the metal plate 17 does not cover the blank holder 9. When press forming so that the portion 17a corresponding to the short side end portion 2a is applied to the blank holder 9, the load on the metal plate 17 at the portion is large, and the portion corresponding to the shoulder portion of the punch 6 in the metal plate 17 is formed. Cracks occur or wrinkles occur in the flange 4 near the component corner. Therefore, the metal plate 17 is arranged as described above to avoid the occurrence of cracks and wrinkles.

<Metal plate clamping process>
The metal plate clamping step is a step of clamping the metal plate 17 arranged on the blank holder 9 by the metal plate arranging step between the die 7 and the blank holder 9.
The reason why the metal plate 17 is sandwiched between the die 7 and the blank holder 9 is to suppress the generation of wrinkles at the flange. In the case where the die 7 and the blank holder 9 are not sandwiched, when the punch 6 is pushed in, a freely movable portion of the metal plate 17 flows around the part shape changing portion, and wrinkles are likely to occur. . Particularly, in the vicinity of the end portion of the metal plate 17 that becomes the flange portion 4 (see FIG. 2) of the component, the metal plate 17 can be easily deformed, so that large wrinkles are generated. For this reason, it is necessary to hold down the metal plate 17 with the die 7 and the blank holder 9 from the initial stage of press molding.
In addition, as for the average pressure (blank holder pressure) which presses the metal plate 17 with the die | dye 7 and the blank holder 9, it is desirable to set it as 0.7 Mpa or more.

<Molding process>
The forming step is a step of pressing the punch 6 against the metal plate 17 sandwiched between the die 7 and the blank holder 9 to form the metal plate 17 by drawing.

<Pad presser process>
The pad pressing process is a process of pressing a position including a portion corresponding to the bent portion 2b in the metal plate 17 by the punch 6 and the pad 11 in the middle of the forming process after the metal plate clamping process.
In this way, pressing the metal plate 17 with the punch 6 and the pad 11 is effective in suppressing the generation of wrinkles in the bent portion 2b (see FIG. 7).
If the range (pad range) in which the metal plate 17 is pressed by the punch 6 and the pad 11 is at least the bent portion 2b (see FIG. 2), it is possible to suppress the occurrence of wrinkles. Further, the top plate 2 may be pressed in a wider range.

The pad pressing step is 0 with respect to the forming depth from the position (see FIG. 1B) where the punch 6 in the forming step starts to contact the metal plate 17 to the bottom dead center position (see FIG. 1C). Start at the% to 50% position.
The timing of starting pressing the metal plate 17 with the punch 6 and the pad 11 after the 0% position of the forming depth, that is, after the punch 6 contacts the metal plate 17, is the initial contact between the punch 6 and the metal plate 17. This is because the swelling of the metal plate 17 at the top plate portion 2 starting from can be suppressed, and the generation of wrinkles can be effectively suppressed.

Pressing the metal plate 17 with the punch 6 and the pad 11 at a position prior to 0% of the forming depth (for example, the position shown in FIG. 1A) before pressing the metal plate 17 with the die 7 and the blank holder 9. Since the metal plate 17 is pushed in the direction of the punch 6 by the pad 11, an excessive material surplus is generated with respect to the final shape of the component, which is not preferable.
Moreover, even if the metal plate 17 is started to be pressed by the punch 6 and the pad 11 after exceeding the 50% position of the forming depth, the swell that has already been waved at the top plate portion 2 cannot greatly suppress wrinkles. The timing at which the metal plate 17 is started to be pressed by the pad 11 is set to 50% of the forming depth. The position where the punch 6 first contacts the metal plate 17 may not be within the range where the punch 6 and the pad 11 hold the metal plate 17.

  The average pressure (pad pressure) for pressing the metal plate 17 with the punch 6 and the pad 11 is preferably 3 MPa or more. By carrying out like this, generation | occurrence | production of the wrinkles in the top-plate part 2 grade | etc., Can be suppressed.

  As described above, according to the present embodiment, when the L-shaped part 1 is press-formed, even if an ultra-high strength high-tensile material with low ductility is used as the metal plate 17, the number of forming steps is not increased. Can suppress wrinkles and avoid cracks.

  In the above description, the L-shaped part 1 that is L-shaped as a whole has been described as an example. However, any part having an L-shaped part in the entire shape may be used. Are substantially U-shaped parts, substantially Z-shaped parts, and the like.

[Embodiment 2]
The present invention can be similarly applied to a component having a T-shaped portion in addition to a component having an L-shaped portion. FIG. 9 shows a center pillar reinforcement (hereinafter simply referred to as “center pillar 23”) of an automobile body as an example of a component having a T-shaped portion.
As shown in FIG. 9, the center pillar 23 includes a top plate portion 25 having two T-shaped portions, a vertical wall portion 27 formed around the top plate portion 25, and a vertical wall portion 27 in plan view. And a flange portion 29 formed continuously, and has a substantially hat-shaped cross section as shown in FIG. The overall shape of the center pillar 23 is a shape in which two T-shaped vertical sides are connected to each other.
The vertical wall portion 27 and the flange portion 29 are not formed at both ends of the T-shaped lateral sides (the lateral side end portion 25a, the lateral side end portion 25b, the lateral side end portion 25c, and the lateral side end portion 25d). .

As the press mold, one corresponding to the above-described press mold 5 (punch 32, blank holder 33, die not shown, pad) shown in FIG. 11 is used.
Also in the press molding method, the above-described metal plate arranging step, metal plate clamping step, molding step, and pad pressing step are performed.
In the metal plate placement step, as shown in FIG. 11, portions 35a, 35b, 35c corresponding to the side edge 25a, the side edge 25b, the side edge 25c, and the side edge 25d of the metal plate 35, 35d is arranged so as not to cover the blank holder 33. The width of the portion corresponding to the T-shaped horizontal side of the metal plate 35 is made narrower than the width of the horizontal side. By doing so, it is possible to avoid cracking at the shoulder of the punch 32 and generation of wrinkles at the flange 29 near the component corner.

In the pad pressing process, the range in which the metal plate 35 is pressed by the punch 32 and the pad is, for example, a connecting portion 25e of a T-shaped horizontal side and a vertical side as shown by a portion surrounded by a thick line in FIG. As a result, the occurrence of wrinkles can be suppressed. Further, the top plate portion 25 may be pressed in a wider range. Further, in the pad pressing process, the timing for starting to press the metal plate 35 with the punch 32 and the pad may be the same as in the case of the L-shaped component 1 described above.
The center pillar 23 has a final part shape by trimming unnecessary portions after press molding.

In order to confirm the effects of the press molding method of the present invention, a specific experiment was conducted.
In the experiment, under various press molding conditions, a front pillar reinforcement (hereinafter simply referred to as “front pillar 40”) of an automobile body is press molded as a part having the L-shaped portion shown in FIG. 12 and FIG. Each press-formed product was evaluated for wrinkles and cracks.

The front pillar 40 is formed continuously with the L-shaped top plate portion 41 having a long side and a short side in a plan view, a vertical wall portion 42 formed around the top plate portion 41, and the vertical wall portion 42. The cross section is substantially hat-shaped as shown in FIG.
The vertical wall portion 42 and the flange portion 43 are not formed at both ends of the long side of the front pillar 40 and the end portion of the short side (short side end portion 41a).

In this example, the press mold shown in FIGS. 14 and 15 was used.
FIG. 14 shows a lower mold in which a blank holder 45 is supported by cushion pins 44. An opening 45a is provided in the center of the blank holder 45, and a punch 47 is disposed in the opening 45a.
FIG. 15 shows an upper mold, in which a die 51 having a recess 51a into which a punch 47 is inserted into a slider (not shown) is installed. A pad 53 is disposed in an opening 51 b provided on the bottom surface of the recessed portion 51 a of the die 51.

The pad 53 is connected to a gas cylinder (not shown) to generate a load, and the protruding position of the pad 53 was adjusted by inserting a metal block (not shown) between the slider and the gas cylinder.
As the metal plate 55 (see FIG. 16), two types of cold-rolled steel sheets having a tensile strength of 980 MPa class and 1180 MPa class were used as ultra-high strength high-tensile materials having low ductility. The thickness of the metal plate 55 was 1.4 mm.
The press molding was performed for a plurality of conditions by combining various combinations of blank holder pressure (MPa), pad range, pad pressure (MPa), pad protrusion position (%), and metal plate arrangement. These conditions are shown in Table 1.

The conditions shown in Invention Example 1 to Invention Example 11 in Table 1 are all within the scope of the present invention for the above-mentioned blank holder pressure, pad range, pad pressure, pad protrusion position, and metal plate arrangement. The conditions shown in Comparative Examples 1 to 5 include outside the scope of the present invention.
The blank holder pressure, pad range, pad pressure, pad protrusion position, and metal plate arrangement will be described in detail below.

The blank holder pressure is an average pressure in the region of the metal plate 55 sandwiched between the die 51 and the blank holder 45, and 0.7 MPa or more is within the scope of the present invention.
The pad pressure is an average pressure for pressing the metal plate 55 with the punch 47 and the pad 53 in the pad pressing step, and 3 MPa or more is within the scope of the present invention.

  As shown in FIG. 16, the pad protrusion position is such that the metal plate 55 is sandwiched between the die 51 and the blank holder 45 with the pad 53 removed, and the pad 53 contacts the metal plate 55 when the pad 53 is installed in this state. The forming position was the 0% position of the pad 53, the upper direction from the origin was positive, and the lower direction was the negative direction, and the molding depth was the 100% position. The pad protruding position is within the range of 0% to 50% within the scope of the present invention.

  There are two types of metal plates 55 as shown in FIG. FIG. 17A shows a case where the metal plate 55 is arranged so that the portion 55a corresponding to the short side end portion 41a of the metal plate 55 does not cover the blank holder 45, and FIG. This is the case. The arrangement shown in FIG. 17 (a) is within the scope of the present invention.

The pad range was changed using three types of pads 53 shown in FIG. 18 (a) shows a part of the metal plate 55 corresponding to the bent part 41b, FIG. 18 (b) shows a part corresponding to the bent part 41b, and FIG. 18 (c). Is to suppress the entire portion corresponding to the top plate portion 41. The pad range shown in FIGS. 18B and 18C is the range of the present invention.
In FIG. 18B and FIG. 18C, the arc shape of the pad 53 matches the arc shape of the bent portion 41 b of the top plate portion 41. A portion surrounded by a dotted line in FIG. 18A and a portion surrounded by a dotted line and an arc in FIGS. 18B and 18C are surrounded by an arc D, a tangent L1, and a tangent L2 in FIG. It corresponds to the part.
Table 2 shows the results of press molding based on the conditions in Table 1.

  Evaluation items are cracks and wrinkles of the flange portion 43, wrinkles of the top plate portion 41, and cracks of the shoulder R portion of the punch 47. The evaluation of wrinkles was made visually. In Table 2, the case where no wrinkle is seen is denoted by ◎, the case where minute wrinkle is seen is denoted by ○, and the case where significant wrinkle is seen is denoted by ×. The evaluation of cracks was also made visually. In Table 2, the case where a crack is not seen is marked as “◯”, and the case where a crack is seen is marked as “X”. And comprehensive evaluation of wrinkles and cracks was performed. In Table 2, a case where the evaluation is good is indicated as OK, and a case where the evaluation is bad is indicated as NG.

As shown in Table 2, in Inventive Example 1 to Inventive Example 11, there were no cracks in the flange portion 43 and no cracks in the shoulder R portion, and there were no wrinkles or slight, and good overall evaluation was obtained.
On the other hand, in Comparative Examples 1 to 5, the overall evaluation was poor. In Comparative Example 1, wrinkles occurred in the flange portion 43 because the blank holder pressure was as low as 0.3 MPa. In Comparative Example 2, since the pad pressure was as low as 1.0 MPa, wrinkles of the top plate portion 41 were generated. In Comparative Example 3, the pad protrusion position was 75%, and the timing at which the metal plate 55 was started to be pressed by the pad 53 was late, so that wrinkles of the top plate portion 41 could not be sufficiently suppressed. In Comparative Example 4, as shown in FIG. 17 (b), the portion 55a corresponding to the short side end portion 41a of the metal plate 55 is hung on the blank holder 45, so that a crack occurs at the shoulder R portion. did. In Comparative Example 5, since there is no pad, wrinkles are generated in the top plate portion 41, and the portion 55a corresponding to the short side end portion 41a of the metal plate 55 is applied to the blank holder 45, so the shoulder R portion Cracking occurred.

  As described above, in this embodiment, when the front pillar 40 is press-molded, even if an ultra-high strength high-tensile material with low ductility is used, suppression of wrinkles and avoidance of cracks can be achieved without increasing the number of molding processes. I was able to.

Example 1 was an example of the front pillar 40 (part having an L-shaped part). Next, in the present embodiment, the center pillar 23 (see FIGS. 9 and 10), which is a component having a T-shaped portion, was also tested because it was the same experiment as in the first embodiment.
In this embodiment, the pad is connected to the gas cylinder in the same manner as in the first embodiment to generate a load, and the adjustment of the protruding position of the pad is the same as in the first embodiment. Further, the metal plate 35 used in the experiment is the same as that in Example 1 (tensile strength of 980 MPa class and 1180 MPa class cold-rolled steel sheets having a thickness of 1.4 mm).

The press molding was performed for a plurality of conditions by combining various combinations of blank holder pressure (MPa), pad pressure (MPa), pad protrusion position (%), and metal plate arrangement. Table 3 shows the press molding conditions.
Since the blank holder pressure, the pad pressure, and the pad protrusion position are the same as those in the first embodiment, the description thereof is omitted.
There are two types of metal plates 35 as shown in FIG. FIG. 19A shows the metal plate 35 with portions 35a, 35b, 35c, and 35d corresponding to the side edge 25a, side edge 25b, side edge 25c, and side edge 25d of the metal plate 35. FIG. 19B shows a case where the blank holder 33 is arranged so as not to cover the blank holder 33. FIG. The arrangement shown in FIG. 19 (a) is within the scope of the present invention.
In all of Invention Example 12 to Invention Example 20 and Comparative Example 6 to Comparative Example 9 in Table 3, the pad range is set to hold the connecting portion 25e surrounded by the middle thick line shown in FIG.

As shown in Table 3, the conditions shown in Invention Example 12 to Invention Example 20 are conditions in which the above-mentioned blank holder pressure, pad pressure, pad protrusion position, and metal plate arrangement are all within the scope of the present invention. Comparative Examples 6 to 9 are conditions including those outside the scope of the present invention.
Table 4 shows the results of press molding based on the conditions in Table 3.

Since the way of viewing Table 4 is the same as that of Table 2, the description thereof is omitted. As shown in Table 4, in Invention Example 12 to Invention Example 20, there were no cracks and wrinkles in the flange portion 29, wrinkles in the top plate portion 25 and cracks in the shoulder R portion, and good comprehensive evaluation was obtained.
On the other hand, in Comparative Examples 6 to 9, the overall evaluation was poor. In Comparative Example 6, wrinkles occurred in the flange portion 29 because the blank holder pressure was as low as 0.4 MPa. In Comparative Example 7, since the pad pressure was as low as 1.0 MPa, wrinkles of the top plate portion 25 were generated. In Comparative Example 8, the pad protrusion position was 70%, and the timing at which the metal plate 35 was started to be pressed by the pad was late, so that wrinkles on the top plate portion 25 could not be suppressed. In Comparative Example 9, as shown in FIG. 19B, the metal plate 35 is a portion 35a corresponding to the lateral edge portion 25a, the lateral edge portion 25b, the lateral edge portion 25c, and the lateral edge portion 25d of the metallic plate 35. , 35b, 35c, and 35d are applied to the blank holder 33, so that a crack occurs at the shoulder R portion.

  As described above, in the present embodiment, when the center pillar 23 (part having a T-shaped portion) is press-formed, even if an ultra-high strength high-tensile material having low ductility is used, the number of forming steps is not increased. It was possible to suppress wrinkles and avoid cracks.

D Arcs L1, L2 Tangent S Area 1 L-shaped part 2 Top plate part 2a Short side edge part 2b Bent part 3 Vertical wall part 4 Flange part 5 Press molding die 6 Punch 6a Molding surface 7 Die 7a Recessed part 7b Opening part 7c Holding surface 9 Blank holder 9a Opening 11 Pad 13 Bolster 15 Slider 17 Metal plate 17a Part 19 Cushion pin 21 Gas cylinder 23 Center pillar 25 Top plate 25a, 25b, 25c, 25d Horizontal side end 25e Connecting part 27 Vertical wall Part 29 Flange part 32 Punch 33 Blank holder 35 Metal plate 35a, 35b, 35c, 35d Part 40 Front pillar 41 Top plate part 41a Short side edge part 41b Bending part 42 Vertical wall part 43 Flange part 44 Cushion pin 45 Blank holder 45a Opening Part 47 Punch 51 Die 5 a recess 51b opening 53 pad 55 metal plate 55a sites

Claims (2)

A punch having a molding surface, a die having a molding surface corresponding to the punch, a blank holder for clamping a metal plate between the die, and a pad for clamping a part of the metal plate in cooperation with the punch The metal plate using a press mold having a top plate portion, a vertical wall portion formed around the top plate portion, and a flange portion continuously formed on the vertical wall portion. A press molding method comprising press molding a part having an L-shaped part in plan view,
A metal plate disposing step of disposing the metal plate so as not to cover the blank holder at a portion corresponding to an end of the L-shaped short side of the metal plate;
A metal plate sandwiching step of sandwiching the metal plate placed on the blank holder by the metal plate placement step between the die and the blank holder;
A molding step of pressing the punch against the metal plate held between the die and the blank holder to mold the metal plate by drawing,
After the metal plate clamping step, there is a pad pressing step for pressing a position including at least an L-shaped bent portion of a portion corresponding to the top plate portion of the metal plate by the punch and the pad during the forming step. And
The pad pressing process starts at a position of 0% to 50% with respect to the forming depth from the position at which the punch in the forming process starts to contact the metal plate to the bottom dead center position,
The average pressure for holding the metal plate with the die and the blank holder in the metal plate clamping step is 0.7 MPa or more,
The press forming method, wherein an average pressure for pressing the metal plate with the punch and the pad in the pad pressing step is 3 MPa or more. A punch having a molding surface, a die having a molding surface corresponding to the punch, a blank holder for clamping a metal plate between the die, and a pad for clamping a part of the metal plate in cooperation with the punch The metal plate using a press mold having a top plate portion, a vertical wall portion formed around the top plate portion, and a flange portion continuously formed on the vertical wall portion. A press molding method comprising press molding a part having a T-shaped part in plan view,
A metal plate disposing step of disposing the metal plate so as not to cover the blank holder at a portion corresponding to the end of the T-shaped lateral side of the metal plate;
A metal plate sandwiching step of sandwiching the metal plate placed on the blank holder by the metal plate placement step between the die and the blank holder;
A molding step of pressing the punch against the metal plate held between the die and the blank holder to mold the metal plate by drawing,
After the metal plate clamping step, a position including at least a T-shaped horizontal side and vertical side connection portion of a portion corresponding to the top plate portion of the metal plate is pressed by the punch and the pad during the molding step. A pad presser process,
The pad pressing process starts at a position of 0% to 50% with respect to the forming depth from the position at which the punch in the forming process starts to contact the metal plate to the bottom dead center position,
The average pressure for holding the metal plate with the die and the blank holder in the metal plate clamping step is 0.7 MPa or more,
The press forming method, wherein an average pressure for pressing the metal plate with the punch and the pad in the pad pressing step is 3 MPa or more.