JP6152911B1 - Press forming method - Google Patents

Abstract

Provided is a press molding method for suppressing wall opening of a press molded part due to a spring back in press molding a press molded part having a hat-shaped cross section. A press forming method according to the present invention is to form a press-formed part 70 having a cross-sectional hat shape having a top plate portion 71, a vertical wall portion 75, and a flange portion 79. 21, vertical wall forming portions 13 and 23, and flange forming portions 15 and 25, the vertical wall forming portions 13 and 23 are mountain-shaped with a cross section protruding outward in the forming direction as compared with the target shape of the press-formed part 70. The first mold 1 that molds the vertical wall portion 65 of the metal mold 50 is used to form a metal base plate 50 into a temporary molded part 60, and the top plate is formed in the same shape as the target shape of the press-formed part 70. Characterized in that it has a second molding step of molding the temporary molded part 60 using the second mold 3 having the parts 31 and 43, the vertical wall molding parts 33 and 43, and the flange molding parts 35 and 45. It is. [Selection] Figure 1

Description

  The present invention relates to a press forming method for a press-formed part having a hat-shaped cross section, and more particularly, to a press forming method having excellent shape freezing property for suppressing spring back.

  In recent years, high-strength steel sheets are being frequently used for automobile parts in order to reduce the weight of automobile bodies due to environmental problems. For the production of automobile parts, press molding with excellent production cost is often used. However, a high-strength steel plate has a greater elastic recovery (springback) after press forming than a low-strength steel plate, making it difficult to obtain a target-shaped part by press forming. Further, increasing the strength of the steel sheet used for the purpose of reducing the weight of the vehicle body is synonymous with reducing the wall thickness, but the fact that the steel sheet with a smaller thickness has a larger springback also spurs the above problem.

  Therefore, there is a strong demand for the development of a press molding method for suppressing springback. In particular, in a press-formed part with a cross-sectional hat shape often found in automobile frame parts to which high-strength steel sheets are applied, the opening width of the vertical wall portion of the press-formed part is larger than the opening width of the target shape by springback. Deformation of the wall opening often occurs, and the suppression of the wall opening by the springback is significant.

  So far, several press forming methods for suppressing wall opening caused by springback of a press-formed part having a hat-shaped cross section have been disclosed.

  In Patent Document 1, provisional molding is formed in which the distance between the lateral wall side ends of the vertical wall part in the molding target shape is shorter than the distance between the lateral wall side end parts of the vertical wall part of the molding target shape of the molding member. A technique is disclosed in which a body is drawn and then the vertical wall portion is expanded in a target shape. And according to this technique, the vertical wall portion of the temporary molded body can be reversely bent and bent back, and the stress that causes the wall warp existing in the vertical wall portion of the temporary molded body is eliminated. It is said that the wall opening can be suppressed by reducing the wall warp after being released from the wall.

  Further, in Patent Document 2, as in Patent Document 1, an intermediate molded product having a punch bottom portion smaller than the molding target shape is formed, and formed into the target shape in the next step, so that the spring back after mold release is achieved. A technique for leaving a deformation that cancels out the wall opening caused by the above is disclosed.

JP 2008-307557 A Japanese Patent No. 4681420

  In order to suppress the wall opening of a press-molded part having a hat-shaped cross section, for example, a stress that reduces or cancels the stress caused by the warp applied to the vertical wall part that is bent and bent back in draw molding. It is important to apply or deformation to an appropriate part.

  In the press molding methods disclosed in Patent Document 1 and Patent Document 2, the intermediate body is molded in the first molding process, and the vertical wall portion is projected in the second molding process. After molding the intermediate molded body to which stress or deformation that offsets the drive stress of the wall opening is applied so that the compressive stress applied to the inside of the vertical wall portion of the intermediate molded body and the tensile stress applied to the outside do not act, In the molding process, the vertical wall part is projected to form a press-molded part with a target-shaped cross-sectional hat shape, but in the second molding process, the inner compressive stress and the outer tensile stress are applied in the projection of the vertical wall part. In addition, since the wall warp cannot be eliminated and the angle change with respect to the target shape of the flange part and the vertical wall part of the formed press-molded part is not considered, it is joined to other parts via the flange part. Problem There was a case that occurs.

  The present invention has been made in order to solve the above-described problems. When a part having a hat-shaped cross section is formed, a flange portion which suppresses wall opening due to a springback and is joined to another part. An object of the present invention is to provide a press molding method capable of suppressing the angle change.

(1) A press molding method according to the present invention molds a press-molded part having a cross-sectional hat shape having a top plate portion, a vertical wall portion continuous from the top plate portion, and a flange portion continuous from the vertical wall portion. A top plate forming portion, a vertical wall forming portion, and a flange forming portion, and the top plate forming portion and the flange forming portion have a top plate portion and a flange having the same shape as a target shape of the press-molded part. The vertical wall molding portion is formed by using a first mold for molding a mountain-shaped vertical wall portion whose cross section in the molding direction is convex outward compared to the target shape of the press-molded part, A first forming step of forming a metal base plate into a temporary formed part; a top plate part having the same shape as a target shape of the press-formed part; a vertical wall part; Forming the temporary molded part with a second mold having a flange forming portion It is characterized in that a second molding step.

(2) In the above-described (1), the press-molded part is formed in a linear shape in the longitudinal direction.

(3) In the above-described (1) or (2), the first molding step is characterized by molding by foam molding.

(4) In the device according to any one of (1) to (3), the length of the ridge line from the punch shoulder portion to the die shoulder portion in the temporary molded part molded in the first molding step is set as described above. It is the same as the length of the ridge line from the punch shoulder portion to the die shoulder portion in the press-formed part formed in the second forming step.

  In the present invention, a cross-hat-shaped press-molded part having a top plate portion, a vertical wall portion continuous from the top plate portion, and a flange portion continuous from the vertical wall portion is formed. A molding part, a vertical wall molding part, and a flange molding part, wherein the top plate molding part and the flange molding part have the same shape as the target shape of the press-molded part, and the vertical wall molding part is a part of the press-molded part. A first molding step of molding a temporary molded part using a first mold that molds a vertical wall portion having a convex outer shape in section compared to the target shape, and the same target shape as the press molded part A second molding step of molding the temporary molded part by using a second mold having a top plate molding part, a vertical wall molding part and a flange molding part in a shape, and thereby reverse bending the vertical wall part. By forming the provisional molded part to the target shape, The deformation of the vertical wall portion after mold release of the less-formed part and the angle change of the punch shoulder portion connecting the top plate portion and the vertical wall portion are offset, and the deformation of the vertical wall portion after the mold release By changing the angle and the radius of curvature of the mountain-shaped bent portion provided to the temporary molded part, the angle change of the die shoulder part connecting the vertical wall part and the flange part cooperates. The wall opening and the angle of the flange part can be adjusted, and the wall opening and the angle change of the flange part due to the spring back are suppressed, and a press-molded part having excellent shape freezing property can be obtained.

It is a figure explaining the press molding method which concerns on embodiment of this invention, (a) is a 1st shaping | molding process, (b) is a figure which shows a 2nd shaping | molding process. It is an external view of a press-molded part to be molded in the embodiment of the present invention. It is a figure explaining the metal mold | die used for the conventional press molding, (a) is a metal mold | die used for draw molding, (b) is a figure which shows the metal mold | die used for foam molding. It is explanatory drawing explaining the springback which arises in the press-molded components shape | molded with the conventional press molding method. It is a figure explaining the temporary molding components shape | molded in the press molding method which concerns on this Embodiment. It is explanatory drawing of the metal mold | die used at the 1st shaping | molding process of the press molding method which concerns on this Embodiment. It is a figure explaining the shape of the press molding component made into a shaping | molding object in a present Example. It is a figure which shows the cross-sectional shape of the press molded component shape | molded by the press molding method which concerns on this invention.

  The press molding method according to the embodiment of the present invention includes a top plate portion 71, a vertical wall portion 75 continuous from the top plate portion 71, and a flange portion 79 continuous from the vertical wall portion 75 as shown in FIG. A press-molded part 70 having a cross-sectional hat shape is formed, and as shown in FIG. 1, a metal base plate 50 is temporarily formed by using a first mold 1 having a die 10 and a punch 20. And a second molding step of molding the temporary molded part 60 into the press-molded part 70 using the second mold 3 having the die 30 and the punch 40.

  Hereinafter, after describing the press-molded part 70 to be molded in the present embodiment, each step of the press molding method according to the present embodiment will be described in detail.

<Press-formed parts>
As shown in FIG. 2, the press-molded component 70 includes a top plate portion 71, a vertical wall portion 75 that continues from the top plate portion 71 through a punch shoulder portion 73, and a vertical wall portion 75 through a die shoulder portion 77. It has a cross-sectional hat shape having a continuous flange portion 79 and is linearly formed in the longitudinal direction.

  Conventionally, a press-molded part 70 as shown in FIG. 2 is a form using a draw mold (drawing) using a mold 80 shown in FIG. 3 (a) or a mold 90 shown in FIG. 3 (b). It was formed by molding (bending molding).

  In the case of draw molding, the die 80 is composed of a die 81, a punch 83, and a blank halter 85. First, the metal base plate (blank) is held between the die 81 and the blank holder 85, and then the punch 83 is attached to the die 81. The film is drawn by moving it relatively.

  On the other hand, in the case of foam molding, the mold 90 is composed of a die 91 and a punch 93, and is bent by sandwiching a metal base plate by relative movement of the die 91 and the punch 93.

  In any molding method, the molded press-molded part 70 is a springback of both the opening of the punch shoulder 73 (increase in the opening angle of the top plate 71 and the vertical wall 75) and the wall warp of the vertical wall 75. As a result of the combination, a wall opening that deforms so that the opening width of the left and right vertical wall portions 75 is larger than the opening width of the target shape occurs.

  In particular, when the metal base plate to be used is a high-strength steel plate or when the plate thickness is thin, the above-described wall opening is remarkable, and the press-formed part 70 deviates greatly from the target shape.

  Further, in order to join the press-formed part 70 having a hat-shaped cross section with other parts by spot welding, it is necessary to match the position and angle of the flange part 79 with respect to the joining surface (flange part) of the other part. In the press-molded part 70 in which the wall opening due to the spring back as shown in FIG. 4 occurs, in addition to the position of the flange portion 79 being changed, the angle with respect to the joining surface is changed. There were cases where it was not possible.

  Therefore, the press-molded component 70 is required to be press-molded in which the change in the angle of the flange portion 79 is suppressed in addition to the wall opening.

<First molding step>
In the first forming step, as shown in FIG. 1A, the metal base plate 50 is pressed by the pad 17, for example, using the first mold 1 having the die 10 and the punch 20, so that the temporary forming part 60 is formed. In the molding step, the die 10 and the punch 20 have top plate forming portions 11 and 21, vertical wall forming portions 13 and 23, and flange forming portions 15 and 25, respectively.

  The top plate forming portions 11 and 21 and the flange forming portions 15 and 25 are for forming the top plate portion 61 and the flange portion 69 having the same shape as the target shape of the press-formed part 70 (FIG. 5).

  On the other hand, the vertical wall forming portions 13 and 23 form a mountain-shaped vertical wall portion 65 having a convex cross section in the forming direction as compared with the press-formed part 70 having a target shape (FIG. 5). reference).

  In the present embodiment, the vertical wall portion 65 includes an upper plane portion 65a that continues from the top plate portion 61 via the punch shoulder portion 63, a bent portion 65b that continues from the upper plane portion 65a, a bent portion 65b, and a die shoulder. As shown in FIG. 6, the first mold 1 includes upper plane molding portions 13a and 23a for molding the upper plane portion 65a, and a bent portion. Bending parts 13b and 23b for forming 65b and lower plane forming parts 13c and 23c for forming lower plane part 65c are provided.

The vertical wall portion 65 formed by the vertical wall forming portions 13 and 23 is provided with a bending in the direction opposite to the wall warp due to the springback, which is seen when forming by the conventional press forming method.
Also, as shown in FIG. 5, the angle α of the punch shoulder 63 is more open than the punch shoulder of the target shape, and the angle β of the die shoulder 67 is closed than the die shoulder of the target shape. .

<Second molding step>
In the second molding step, the temporary molding part 60 is pressed by the pad 37 using the second mold 3 having the die 30 and the punch 40 as shown in FIG. The die 30 and the punch 40 have top plate forming portions 31 and 41, vertical wall forming portions 33 and 43, and flange forming portions 35 and 45, respectively.

  The top plate forming parts 31 and 41, the vertical wall forming parts 33 and 43, and the flange forming parts 35 and 45 are all the same shape as the target shape of the press-formed part 70, and are temporarily formed parts formed in the first forming step. 60 is formed into a press-formed part 70 having a top plate portion 71, a vertical wall portion 75, and a flange portion 79 having the same shape as the target shape.

  The reason why the wall-opening of the press-formed part 70 and the angle change of the flange portion 79 due to the spring back can be suppressed by the press-forming method according to the present embodiment will be described below.

  As described above, when molding is performed using the conventional mold 80 or 90 as shown in FIG. 3, the wall warp and the punch shoulder portion in the vertical wall portion 75 are caused by the spring back after the release as shown in FIG. Wall opening due to both angle changes at 73 occurs.

  This springback is caused by a residual stress difference (inside: compressive stress, outside: tensile stress) generated inside and outside the vertical wall portion 75 in the forming process in either draw forming or foam forming.

  Therefore, with respect to the wall warp in the vertical wall portion 75, in the first forming step, a bending wrinkle (reverse bending) is applied to the vertical wall portion 65 in the opposite direction to the wall warp, and the temporary molded part 60 is formed. In the two molding steps, the direction of the residual stress generated on the inside and outside of the vertical wall 75 of the press-formed part 70 is reversed by forming the vertical wall 65 of the temporary molded part 60 into the vertical wall 75 of the target shape ( (Inside: tensile stress, outside: compressive stress). Thereby, after mold release, the vertical wall part 75 deform | transforms in the direction opposite to the conventional wall curvature, and contributes to reduction of wall opening.

  On the other hand, the punch shoulder 73 is further bent in the direction in which the punch shoulder 63 formed in the first forming step is closed in the second forming step (the angle α of the punch shoulder 63 shown in FIG. 5 decreases). Therefore, when the temporary molded part 60 is molded into the target-shaped press-molded part 70 in the second molding step, the punch shoulder 73 is deformed in the direction of opening (increasing angle) by the springback.

  This increase in the angle of the punch shoulder 73 contributes to an increase in the wall opening of the portion corresponding to the vertical wall portion 65 of the first molding step in the vertical wall portion 75 of the second molding step, but corresponds to the vertical wall portion 65. Since the deformation of the portion that contributes to the reduction of the wall opening, the wall opening of the press-formed part 70 is suppressed by offsetting these, and the difference between the position of the flange portion 79 and the target shape can be reduced.

  Further, the die shoulder portion 67 formed in the first forming step is opened to form the lower plane portion 65c into the vertical wall portion 75 in the second forming step (the angle β of the die shoulder portion 67 shown in FIG. In the second molding step, when the temporary molded component 60 is molded into the press-formed component 70 having the target shape, the die shoulder 77 in the second molding step is closed (the angle is reduced) by the springback. Transforms into

  Although such a decrease in the angle at the die shoulder 77 affects the increase in the angle from the joint surface of the flange portion 79, the molding of the vertical wall portion 75 and the flange portion 79 described above causes the joint surface of the flange portion 79 to be formed. Decrease the angle. Accordingly, the decrease in the angle at the die shoulder 77 and the deformation at the vertical wall 75 cooperate to suppress an increase in the angle of the flange 79 with respect to the joint surface.

  That is, according to the present invention, by applying reverse bending to the vertical wall portion 75 of the press-molded component 70, the spring back in the vertical wall portion 75 after releasing the press-molded component 70 opens the wall (the position of the flange portion 79). ) And an increase in the angle of the flange portion 79 are suppressed.

  Here, the first mold 1 used in the first molding step in the present embodiment is a vertical wall composed of upper planar molded parts 13a and 23a, bent molded parts 13b and 23b, and lower planar molded parts 13c and 23c. Since the molding parts 13 and 23 are provided, as shown in FIG. 5, the temporary molding part 60 has an upper plane part 65a and a lower plane part 65c of the vertical wall part 65 that are connected to each other by a bent part 65b and projecting outward. It has a mountain shape.

  And when the deformation | transformation amount after mold release in the considerable part of the bending part 65b of the press molding component 70 is the same, the position in the shaping | molding height direction from the flange part 69 of the bending part 65b to the top-plate part 61 direction is so high. Since the position change of the lower end of the vertical wall portion 75 (in the vicinity of the flange portion 79 of the vertical wall portion 75) due to the deformation after the mold release in the second molding step becomes large, the bent portion 65b applied in the first molding step is It is considered that the higher the position, the more advantageous for suppressing the wall opening.

  In addition, the larger the radius of curvature R (fillet diameter) of the bent portion 65b is, the wider the range of the vertical wall portion 65 that is subjected to reverse bending in the second forming step is. It is considered high. On the other hand, if the radius of curvature R of the bent portion 65b is too small, a crease remains in the vertical wall portion 75 of the press-formed part 70, which is not preferable.

  Therefore, a press-molded part obtained by molding the temporary molded part 60 in the second molding step by appropriately changing the position H and the radius of curvature R in the molding height direction from the flange 69 to the top plate 61 in the bent part 65b. The wall opening due to the spring back 70 and the angle change of the flange portion 79 can be adjusted.

  The effect of suppressing the wall opening and the angle change of the flange portion 69 by changing the position H and the radius of curvature R of the bent portion 65b will be demonstrated in the embodiments described later.

  The temporary molded part 60 molded in the first molding step of the press molding method according to the present invention must be molded in a shape recessed inward from a temporary line connecting the punch shoulder 63 and the die shoulder 67. For example, there may be no flat part such as the upper flat part 65a and the lower flat part 65c, and the entire vertical wall part 65 may be curved in a convex mountain shape.

  Further, the press-molded part 70 to be molded in the above description is formed linearly in the longitudinal direction, and the longitudinal wall portion 65 of the temporary molded part 60 protrudes outward in the longitudinal direction. However, in the present invention, only a part of the vertical wall portion of the temporary molded part is protruded outward in the first molding step. It does not exclude what is formed into a mountain shape.

  Furthermore, in the press molding method according to the present embodiment, the first molding step is molded by foam molding, but the first molding step may be performed by draw molding.

  The difference when molded by foam molding or draw molding in the first molding step will be described in Examples described later.

  In the above description, the metal base plate 50 is pressed and formed by the pad 17 in the first forming step (FIG. 6), and the temporary formed part 60 is pressed and formed by the pad 37 in the second forming step. The press molding method according to the present invention may perform the first molding process and the second molding process without using the pads 17 and 37.

  Furthermore, in the above description, as shown in FIG. 5, the molding height of the temporary molded part 60 molded in the first molding process is the molding height of the press-molded part 70 having the target shape molded in the second molding process. In this case, the length of the ridge line from the punch shoulder 63 to the die shoulder 67 (see FIG. 5) in the temporary molded part 60 is determined from the punch shoulder 73 in the press-formed part 70. It is longer than the length of the ridge line reaching the die shoulder 77 (see FIG. 7).

  However, the press molding method according to the present invention is not limited to the one in which the molding height of the temporary molded part and the molding height of the press molded part of the target shape are the same, but the temporary molded part molded in the first molding step The length of the ridge line from the punch shoulder to the die shoulder in the temporary shape is equal to the length of the ridge line from the punch shoulder to the die shoulder in the target shape of the press-formed part formed in the second forming step. It may be formed (draw molding or foam molding) by setting the molding height of the molded part lower than the molding height of the press molded part.

  Then, by setting the length of the ridge line from the punch shoulder to the die shoulder in the temporary molded part and the length of the ridge line from the punch shoulder to the die shoulder in the press-molded part, the molding is performed in the first molding step. Since the molding part (part) of the flange part of the temporary molded part and the flange part of the press-molded part molded in the second molding process coincide with each other, molding closer to the target flange part is possible. Good.

  In order to confirm the operational effects of the press molding method according to the present invention, CAE analysis of press molding and spring back was performed, and the results will be described below.

  In the present embodiment, a press-molded part 70 having a hat-shaped cross section shown in FIG. 7 is used as a molding target shape, and the metal base plate 50 is temporarily formed by using the first mold 1 as shown in FIG. The press molding analysis was performed in the first molding step of molding into the first molding step and the second molding step of molding the temporary molded component 60 into the press molded component 70 using the second mold 3 as shown in FIG. .

  And the springback analysis after mold release of the press-molded part 70 shape | molded to the bottom dead center of shaping | molding in the 2nd shaping | molding process was performed.

  As shown in FIG. 7, the dimensions of the target shape of the press-formed part 70 are as follows. The width of the top plate portion 71 is 60 mm, the molding height is D = 60 mm, the vertical wall angle is 70 °, and the curvature radius of the punch shoulder 73 is set. R = 5 mm.

  The metal base plate 50 used for forming the press-formed part 70 was a steel plate having a thickness t = 1.2 mm and a tensile strength of 1180 MPa class.

  In the press molding analysis of the present example, the first molding process was molded by foam molding or draw molding. Further, as shown in FIG. 5, the vertical wall portion 65 of the temporary molded part 60 molded in the first molding step has an outwardly convex mountain shape composed of an upper plane portion 65a, a bent portion 65b, and a lower plane portion 65c. It was. The dimensions of the temporary molded part 60 are such that the angle of the die shoulder portion 67 is β = 90 °, the molding height D = 60 mm, and the height position H and the curvature radius R (fillet diameter) of the bent portion 65b are changed. The analysis was performed (see FIG. 5).

In this embodiment, the angle between the wall opening by the spring back of the press-formed part 70 and the flange portion 79 was obtained.
The wall opening of the press-formed part 70 was evaluated by the amount of change (wall opening amount ΔW) of the distance Wo between the left and right vertical wall portions 75 at a position 55 mm below the top height from the top plate portion 71 (FIG. 4). FIG. 7).
Further, the angle of the flange portion 79 was evaluated by a flange angle θ based on the joint surface of the flange portion 79 having a target shape (see FIG. 4).

  FIG. 8 shows a cross-sectional shape obtained by the springback analysis of the press-formed part 70 formed by press forming analysis using the first forming step as form forming.

FIG. 8 shows a press-formed part 70 when the position in the molding height direction of the bent portion 65b of the temporary molded part 60 formed in the first forming step is H = 30 mm and the radius of curvature of the bent portion 65b is R = 30 mm. This is an analysis result of the cross-sectional shape.
Compared with the target shape of the press-formed part 70, the vertical wall portion 75 has a slightly remaining mountain shape formed in the first forming step, but the position and angle of the flange portion 79 are substantially the same as the target shape. was gotten.

  Table 1 shows that the first molding step is foam molding, press molding analysis is performed by changing the position H in the molding height direction and the radius of curvature R of the bent portion 65b of the temporary molded part 60, and the press molding analysis is performed. The results of the wall opening amount ΔW and the flange angle θ obtained by the springback analysis of the press-formed part 70 are shown.

In Table 1, no countermeasure is the result of using a conventional press molding method (conventional example, see FIG. 3B), and conditions a to h are the results of using the press molding method (invention example) according to the present invention. It is.
Compared with the conventional example, the invention example was clearly excellent in that the wall opening amount ΔW and the flange angle θ (see FIG. 4) were reduced.

  In the invention example, regarding the influence of the difference in the height position H of the bent portion 65b on the wall opening amount ΔW, H = 15 mm at a curvature radius R = 30 mm (relative position H / D = 0.25 relative to the molding height D). Comparing condition d, condition g of H = 30 mm (relative position H / D = 0.50), and condition h of H = 45 mm (relative position H / D = 0.50), position H of the bent portion 65b (relative position H / D ) Increases as the wall opening amount ΔW decreases.

  Further, regarding the difference in the curvature radius R of the bent portion 75b, when the condition a of R = 5 mm, the condition b of R = 10 mm, the condition c of R = 20 mm, and the condition d of R = 30 mm are compared, the curvature radius R becomes large. It can be seen that both the wall opening amount ΔW and the flange angle θ decrease, and approach the target shape. The same applies when the condition e of R = 10 mm, the condition f of R = 20 mm, and the condition g of R = 30 mm are compared.

  From these results, within the range of the position H and the radius of curvature R of the bent portion 65b shown in Table 1, the condition that the position H of the bent portion 65b is 30 mm (relative position H / D = 0.5) and the radius of curvature R is 30 mm. As a result, g was the best match with the target shape for both the wall opening amount ΔW and the flange angle θ.

  Table 2 shows that the first molding process is draw molding, and the press molding analysis is performed by changing the position H in the molding height direction and the radius of curvature R of the bent portion 65b of the temporary molded part 60, and is obtained by the press molding analysis. The results of the wall opening amount ΔW and the flange angle θ obtained by the springback analysis of the press-formed part 70 are shown.

In Table 2, no countermeasure is a result of using a conventional press molding method (conventional example, see FIG. 3A), and conditions i to t are results of using a press molding method (invention example) according to the present invention. It is.
From Table 2, it can be seen that, compared with the conventional example, the wall opening amount ΔW and the flange angle θ are clearly reduced in the inventive example, which is a good result.

  In the example of the invention, regarding the influence of the difference in the height direction position H of the bent portion 65b on the wall opening amount ΔW, the curvature radius R = 30 mm at H = 15 mm (relative position H / D = 0.25 in the molding height direction). Comparing condition l, condition o of H = 30 mm (relative position H / D = 0.50), and condition r of H = 45 mm (relative position H / D = 0.50), the position H of the bent portion 65b (relative position H / D It can be seen that the wall opening amount ΔW decreases with an increase in).

  Further, regarding the difference in the curvature radius R of the bent portion 65b, when the condition i of R = 5 mm, the condition j of R = 10 mm, the condition k of R = 20 mm, and the condition l of R = 30 mm are compared, the curvature radius R becomes larger. It can be seen that both the wall opening amount ΔW and the flange angle θ decrease, and approach the target shape. The same applies to the comparison of the condition m of R = 10 mm, the condition n of R = 20 mm, the condition o of R = 30 mm, the condition p of R = 10 mm, the condition q of R = 20 mm, and the condition r of R = 30 mm. It is.

  From these results, within the range of the position H and the radius of curvature R of the bent portion 65b shown in Table 2, the condition o where the position H of the bent portion 65b is 30 mm and the radius of curvature R is 30 mm is the wall opening amount ΔW and the flange. The angle θ was the best match with the target shape.

  Further, comparing the case where the first molding step is foam molding (Table 1) and the case where draw molding is performed (Table 2), in the condition where the position H of the bent portion 65b and the radius of curvature R are equal, the foam molding is better. Both the flange angle θ and the wall opening amount ΔW were better than in the case of draw molding.

  As described above, in the press molding method according to the present invention, by forming a mountain-shaped temporary molded part that protrudes outward from the target shape, and then molding the target-shaped press molded part, the wall opening by the springback and The angle change of the flange part can be reduced, and the angle of the flange part of the wall opening and the press-formed part can be adjusted by appropriately changing the position and the radius of curvature of the bent part given to the temporary molded part. Indicated. Moreover, it was demonstrated that the spring back can be more effectively suppressed by forming the first forming step by foam forming.

Further, the first molding step is formed as a foam molding, and a temporary molding component 60 (see FIG. 5) is molded. In the second molding step, the length of the ridge line from the punch shoulder 63 to the die shoulder 67 of the temporary molding component 60 is increased. The second mold is changed in the same case where the length of the ridge line from the punch shoulder 73 to the die shoulder 77 of the press-molded part 70 (see FIG. 7) formed in the second molding step is different. And press-molded.
The position of the bent portion 65b of the temporary molded part 60 was H = 30 mm, and the radius of curvature was R = 20 mm.

  As a result, the length of the ridge line from the punch shoulder 63 to the die shoulder 67 in the temporary molded part 60 molded in the first molding process and the punch shoulder 73 in the press molded part 70 molded in the second molding process. When the length of the ridge line reaching the die shoulder 77 has a difference of Δ5 mm, the flange angle of the press-formed part 70 is 3.6 ° and the wall opening ΔW is 1.6 mm, whereas the length of the ridge line is the same. In the case of (difference of Δ0 mm), the flange angle was 3.0 ° and the wall opening was 1.2 mm.

  Therefore, by making the length of the ridge line in the temporary molded part 60 molded in the first molding process the same as the length of the ridge line in the press molded part 70 molded in the second molding process, both the wall opening and the flange angle are set. It was proved that the springback can be more effectively suppressed with good results.

DESCRIPTION OF SYMBOLS 1 1st metal mold | die 3 2nd metal mold | die 10 Die 11 Top plate shaping | molding part 13 Vertical wall shaping | molding part 13a Upper plane shaping | molding part 13b Bending shaping | molding part 13c Lower side shaping | molding part 15 Flange shaping | molding part 17 Pad 20 Punch 21 Top plate Molding part 23 Vertical wall molding part 23a Upper plane molding part 23b Bending molding part 23c Lower plane molding part 25 Flange molding part 30 Die 31 Top plate molding part 33 Vertical wall molding part 35 Flange molding part 37 Pad 40 Punch 41 Top panel molding Part 43 Vertical wall forming part 45 Flange forming part 50 Metal base plate 60 Temporary molding part 61 Top plate part 63 Punch shoulder part 65 Vertical wall part 65a Upper plane part 65b Bending part 65c Lower side plane part 67 Die shoulder part 69 Flange part 70 Press molded parts 71 Top plate part 73 Punch shoulder part 75 Vertical wall part 77 Die shoulder part 79 Flange part 80 Mold (conventional technology)
81 Die 83 Punch 85 Blank holder 90 Mold (Conventional technology)
91 Die 93 Punch

Claims (4)

A press molding method for molding a press-molded part having a cross-sectional hat shape having a top plate portion, a vertical wall portion continuous from the top plate portion, and a flange portion continuous from the vertical wall portion,
It has a top plate forming portion, a vertical wall forming portion, and a flange forming portion, and the top plate forming portion and the flange forming portion form a top plate portion and a flange portion having the same shape as the target shape of the press-molded part, The vertical wall forming section is a temporary metal mold using a first mold for forming a mountain-shaped vertical wall having a cross section in the forming direction that is convex outward compared to the target shape of the press-formed part. A first molding step of molding into a molded part;
Using the second mold having the top plate forming portion, the vertical wall forming portion and the flange forming portion for forming the top plate portion, the vertical wall portion and the flange portion having the same shape as the target shape of the press-formed part, the temporary mold is used. A press molding method comprising: a second molding step of foam molding a molded part.   The press-molding method according to claim 1, wherein the press-molded part is molded in a straight line in the longitudinal direction.   The press molding method according to claim 1 or 2, wherein the first molding step is performed by foam molding.   The length of the ridge line from the punch shoulder part to the die shoulder part in the temporary molding part molded in the first molding process is changed from the punch shoulder part to the die shoulder part in the press molded part molded in the second molding process. The press molding method according to any one of claims 1 to 3, wherein the length is the same as the length of the ridge line to reach.