JP2006272378A - Press formed article of metallic sheet, and press working method and press die for metallic sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a press formed article with which an increase in press working force can be suppressed and spring back is reduced and, a press working method and a press die for obtaining the same. <P>SOLUTION: There are provided the press formed article of a metallic sheet characterized in that the portions subjected to bending and unbending deformation by die shoulders are formed to a waveform shape lined up with a plurality of rectilinearly extending irregularities, the press working method and the press die for forming the same. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a press-formed product of a metal plate having a small spring back, a metal plate pressing method for obtaining the same, and a press die.

  In recent years, high-strength steel plates, aluminum alloy plates with a low specific gravity, and the like have been used to reduce the weight of parts such as automobile bodies. These metal plates are formed into various shapes mainly by pressing and processed into various parts. In press working, when a high-tensile steel plate, an aluminum alloy plate, or the like is used, the material strength is higher or the Young's modulus is smaller than that of a normal steel plate, which causes a problem that the spring back of the press-formed product is large.

An example of obtaining a molded product having a hat-shaped cross section will be described with reference to FIG.
In FIG. 8, the shape indicated by the solid line indicates the shape of the molded product before the spring back, and the shape indicated by the broken line indicates the shape of the molded product after the spring back. The shape shown by the solid line at the end of the press forming is formed, but when the molded product is taken out of the mold, it changes to the shape shown by the broken line by the spring back, and the opening width widens from W0 to W.

  When the springback becomes large, it deviates from the planned part shape, so that even if it is intended to assemble the molded product to another member, it cannot be joined well with the other member, resulting in an assembly trouble. Thus, in press working, there is a strong demand for reducing the springback. The cause of the springback is that when a metal plate is drawn and bent with a die equipped with a punch and a die, the moment at the part subjected to bending deformation or bending back bending deformation releases the constraint by the mold. This is because the molded product is deformed so as to become zero.

  In particular, the side wall of the hat-shaped molded product is bent and unbent at the shoulder of the die during press processing, so the amount of deformation is large, and a large bending moment remains when the molded product is constrained by the press mold. . As a result, when the molded product is taken out from the press mold, the side wall is warped, which greatly affects the spring back. Accordingly, various press working methods for suppressing spring back by reducing the bending folds of the die shoulder at the side wall have been proposed. For example, a press working method that imparts a high tensile force when a metal plate material S is subjected to drawing bending using a die having a punch 1, a die 2, and a wrinkle presser 3 as shown in FIG. 9 is known. ing. In FIG. 9, 1a indicates a punch shoulder and 2a indicates a die shoulder.

The method of applying a high tensile force to the side wall portion is to bend and bend back by the die shoulder 2a while increasing the wrinkle holding force 4 and applying a high tensile force to the side wall portion. Although the influence can be reduced, there is a drawback that breakage tends to occur. The wrinkle pressing force 4 is applied by sandwiching the metal plate material S between the die 2 and the wrinkle presser 3.
Further, there has been proposed a molded member that has a good shape and can be molded by a normal press device and a molding method thereof (Patent Document 1). The molding method described in Patent Document 1 uses a press mold in which linear protrusions are provided on the first molding surface and / or the second molding surface, and is bent by a die shoulder and subjected to a lot of bending deformation. This is a method of pressure-molding a linear recess.
JP 2001-87816 A

  However, in the press molding method described in Patent Document 1, it is necessary to form a large number of linear recesses by biting the linear protrusions provided on the mold into a portion that has been bent and unbent by the die shoulder. is there. For this reason, according to the press working method described in Patent Document 1, the press working force increases as the material strength increases and as the member becomes larger. Therefore, when a metal plate having a high material strength such as a high-tensile steel plate is used to form a large press part with a small spring back, the press device that is possessed cannot cope.

An object of the present invention is to eliminate the above-mentioned problems of the prior art, and to provide a press-molded product that can suppress an increase in press working force and that has a small spring back.
In addition, the object of the present invention is to suppress an increase in the press working force by a press working method in which a metal plate such as a high-tensile steel plate having a high material strength or an aluminum alloy plate having a low Young's modulus is subjected to drawing bending. An object of the present invention is to provide a press working method of a metal plate together with a press die capable of obtaining a small molded product.

The present inventors have intensively studied, and by additionally bending the portion that has undergone bending and bending back deformation by the die shoulder, an increase in pressing force can be suppressed, and a molded product with a small spring back can be obtained. As a result, the present invention has been made.
The present invention is as follows.
1. A press-formed product of a metal plate, wherein a portion subjected to bending and bending back deformation by a die shoulder is formed into a corrugated shape in which a plurality of irregularities extending linearly are arranged.
2. A press-formed product of a metal plate, wherein a portion subjected to bending and bending back deformation by a die shoulder is formed into a wave shape in which a plurality of irregularities extending linearly are arranged along a material inflow direction.
3. In the press working method of a metal plate that performs drawing bending on the metal plate, a punch and a die having a working surface formed in a wave shape are used, and the die is bent by the die shoulder in the vicinity of the bottom dead center of the press stroke at which the drawing bending forming ends. A method of pressing a metal plate, characterized in that a bending process is performed on a portion subjected to a bending return deformation by a working surface of the punch and the die.
4). After using a die having no irregularities on the working surface in the first step and roughly forming it into a cross-sectional hat shape, using a punch and a die having a working surface formed in a wave shape in the second step, A metal plate pressing method characterized by bending a portion subjected to bending and bending back deformation by a die shoulder in the vicinity of the bottom dead center of the press stroke in the second step, on the working surface of the punch and the die. .
5. A press die that obtains a molded product by drawing and bending a metal plate, near the bottom dead center of the press stroke, and the surface of the punch that acts on the part of the molded product that has undergone bending and bending back deformation by the die shoulder; A die for pressing, wherein the surface of the die is formed into a wave shape in which a plurality of irregularities extending linearly are arranged.
6). A press die that obtains a molded product by drawing and bending a metal plate, near the bottom dead center of the press stroke, and the surface of the punch that acts on the part of the molded product that has undergone bending and bending back deformation by the die shoulder; A die for pressing, wherein the surface of the die is formed into a wave shape in which a plurality of unevenness extending linearly are arranged along the material inflow direction.
7). Above 6. Or 7. In the press die described in the above, the clearance between the punch surface and the die surface acting on the part subjected to the bending and bending back deformation by the die shoulder at the bottom dead center of the press stroke is greater than the thickness of the metal plate material. The pressing mold is set to 1.3 times or less of the plate thickness.

Hereinafter, as an embodiment of the present invention, a case where a molded product having a hat-shaped cross section is obtained by press working will be described with reference to the drawings.
Fig.1 (a) is an external view of the molded article which concerns on embodiment of this invention, FIG.1 (b) is a partial front view which shows the principal part. A molded product having a hat-shaped cross section can be formed by pressing as shown in FIG.

  As shown in FIG. 1A, the molded product according to the embodiment of the present invention includes a side wall portion 7 that is inclined with respect to the height direction on both sides in the width direction of the top portion 6 that extends in the longitudinal direction, and the side wall portion 7. It is a press-formed product of a metal plate having a flange portion 8 continuing in a different direction with respect to the inclination direction. The side wall portion 7 is inclined with respect to the height direction so that the opening width W is wider than the width of the top portion 6. As shown in FIG. 1B, the side wall portion 7 is formed in a wave shape in which a plurality of waves having a pitch P are periodically arranged as viewed from the front of the molded product.

  As shown in FIGS. 1A and 1B, the corrugated shape of the side wall portion 7 is formed by unevenness extending linearly in the longitudinal direction. In FIG. 1B, d indicates the depth of the concave portion formed on the outer surface of the side wall portion 7. The concave portion formed on the outer surface of the side wall portion 7 corresponds to the convex portion on the inner surface. In the case of the molded product of this embodiment, the side wall portion 7 is formed in a wave shape in which a plurality of irregularities extending linearly are arranged along the material inflow direction, that is, the inclination direction of the side wall portion 7.

In the case of a hat-shaped molded product, for example, the corrugated pitch P is 5 to 20 mm (or 5 to 20 times the thickness of the metal plate material), and the corrugated recess depth d formed on the side wall portion 7 is 2 to 10 mm (or 2 to 10 times the thickness of the metal plate material).
As will be described later, the corrugated shape of the side wall portion 7 is formed by additionally bending the press stroke near the bottom dead center of the press stroke.

Next, a metal plate pressing method for forming a cross-sectional hat-shaped molded product will be described with reference to FIG. Fig.2 (a) is a front view explaining the press work method concerning embodiment of this invention, The same figure (b) is sectional drawing which shows the shaping | molding state at the time of press molding completion (bottom dead center). FIG. 4C is an external view showing the direction in which the convex portion 9 of the punch 1 extends.
As shown in FIG. 2 (a), the cross-section hat-shaped molded article uses a die having a punch 1 and a die 2, and sandwiches both sides in the width direction of the metal plate material S between the die 2 and the wrinkle retainer 3. The die 2 is lowered, the punch 1 is inserted therein, and the metal plate S is subjected to drawing bending forming. At that time, the side wall portion 7 is formed by bending and bending back the metal plate material S by the die shoulder 2a in the process of inserting the punch 1 into the die groove 2b.

  Here, the side wall 7 that has undergone bending and bending-back deformation by the die shoulder 2a is formed in the vicinity of the bottom dead center of the press stroke, as shown in FIG. The convex part 10 provided in the surface of this is contact | abutted, and the bending process is given additionally. Thereafter, the molded product is taken out from the mold, and one step is completed. In FIG. 2, a indicates the material width, and b indicates the width of the molded product at the end of the draw bending process. c represents the die groove depth, and θ represents the inclination angle of the die side wall.

  Here, the working surface of the punch 1 of the press mold and the working surface of the die 2 are formed in a wave shape in which a plurality of unevenness extending linearly are arranged along the material inflow direction 5. In the press mold, the corrugations provided on the punch 1 surface and the die 2 surface are set so as to be shifted from each other by a half pitch (P / 2) near the bottom dead center of the press stroke. In addition, the convex part height D is made high enough to bend the side wall part 7 additionally until it reaches the bottom dead center from the vicinity of the bottom dead center of the press stroke.

  As described above, in the press working method according to the embodiment of the present invention, in the vicinity of the bottom dead center of the press stroke, the side wall portion 7 that has undergone bending and bending back deformation by the die shoulder 2a has a working surface formed in a wave shape. In this method, bending is additionally performed. Therefore, according to the press working method according to the embodiment of the present invention, as compared with the case of pressure forming a large number of linear recesses in the thickness direction of the molded product as in the press working method of Patent Document 1, An increase in pressing force can be suppressed, and a molded product with a small spring back can be obtained.

The reason why a press-molded product with a small spring back can be obtained is that the bending wrinkles of the side wall portion 7 that has undergone bending-bending return deformation by the die shoulder 2a can be corrected by bending deformation.
However, the wave shape provided in the mold is not limited to the shape in which the tips of the protrusions 9 and 10 are pointed as shown in FIG. ) And (b). FIG. 3A shows a sinusoidal wave having a convex tip smoothly formed, and FIG. 3B shows a substantially rectangular wave shape with the corners of the rectangular convex portion chamfered.

The press die used in the press working method according to the embodiment of the present invention is such that the clearance between the punch surface acting on the side wall portion 7 and the die surface is the thickness of the metal plate material at the bottom dead center of the press stroke. As described above, it is preferably set to 1.3 times or less of the plate thickness.
The reason for this is that if the clearance between the punch surface and the die surface is set to be less than the plate thickness of the metal plate material, the clearance will be too small, and the bending will bend and bend back by the die shoulder at the bottom dead center of the press stroke. The side wall 7 that has received the pressure may be pressed by the convex portions 9 and 10, and the clearance between the punch surface and the die surface exceeds 1.3 times the thickness of the metal plate material This is because the clearance becomes excessive and the side wall 7 that has undergone bending and bending back deformation by the die shoulder 2a cannot be sufficiently bent at the bottom dead center of the press stroke.

  By the way, in the wave shape formed on the side wall portion 7 shown in FIG. 1A, the direction in which the unevenness extends linearly is perpendicular to the inclination direction of the side wall portion 7, that is, the material inflow direction 5. The molded product in which the direction in which the unevenness extends linearly and the material inflow direction 5 is orthogonal is a mold in which the unevenness extends linearly in the direction as shown in FIGS. Compared to a molded product having a wave shape, it is preferable that the spring back is small because it has been confirmed by experiments.

FIG. 4A shows a punch 11 in which the direction in which the convex portion 9 extends is formed in parallel with the material inflow direction 5, and FIG. 4B shows the direction in which the convex portion 9 extends in the material inflow direction. A punch 11 formed obliquely with respect to 5 is shown.
The press working method according to the embodiment of the present invention described above is a method of forming a molded product with a small spring back in one step, but a molded product with a small spring back can be formed in two steps. That is, using a die having no irregularities on the working surface in the first step and roughly forming into a hat shape in cross section, then using a punch and a die having the corrugated surface formed in the second step, a rough molded product is obtained. On the other hand, it is also possible to adopt a pressing method in which a portion subjected to bending and bending back deformation by the die shoulder is bent by the working surface of the punch and the die near the bottom dead center of the press stroke in the second step.

  According to such a method of pressing a metal plate in two steps, the first step can be performed under the same processing conditions as the conventional method of pressing a metal plate having a cross-sectional hat shape. In the vicinity of the bottom dead center of the stroke, the side wall portion 7 that has undergone bending and bending back deformation by the die shoulder 2a is subjected to bending deformation, so that an increase in pressing force can be suppressed and a molded product with a small spring back can be formed. . According to the method of pressing a metal plate that finishes a molded product in two steps, there is an advantage that a molded product with high dimensional accuracy can be obtained with less warping of the side wall than in the case of one step.

The experimental results of examining the spring back of the molded product having a hat-shaped cross section by pressing the metal plate material S using a die having a punch and a die are shown below.
As the metal plate material, mild steel having a tensile strength of 270 MPa and high-tensile steel plates having tensile strengths of 590, 780, and 1180 MPa were used. The metal plate material had a plate thickness of 1.2 mm, a material width a of 300 mm, and a length of 100 mm. Using a die having a punch and a die with a pitch P = 5 mm and a convex part height D = 3 mm, with a wrinkle holding force of 98 KN, a pressing force when bending the side wall part 7 = 6 × 98 KN FIG. 5 shows the result of the case.
The parameter to be evaluated for springback was evaluated using the curvature (1 / ρ). The curvature was obtained by measuring a radius of curvature ρ between AC of the side wall portions 7 shown in FIG. 7 with a measuring instrument. A smaller curvature (1 / ρ) indicates a smaller spring back.

  Experimental Example 1 uses a punch 11 provided with unevenness in which the unevenness extending direction is parallel to the material inflow direction 5 and a die provided with the corresponding unevenness as shown in FIG. In Example 2, the punch 1 in which the direction in which the unevenness extends is perpendicular to the material inflow direction 5 and the corresponding unevenness as shown in FIGS. This is a case where a wave shape is formed on the side wall portion using the provided die 2.

The die shoulder radius was 5 mm, the punch shoulder radius was 5 mm, the die sidewall inclination angle θ was 5 °, and the die groove depth was 80 mm. The conventional example is a case in which punches and dies that are not provided with unevenness are used, and other conditions are the same as those in Experimental Examples 1 and 2.
From the results shown in FIG. 5, it can be seen that in the case of Experimental Examples 1 and 2 in which the mold according to the present invention is used for the punch and the die, the spring back is small as compared with the conventional example in which the unevenness is not provided.

  In particular, in the case of Experimental Example 2 using a mold provided with unevenness in which the unevenness extending direction is perpendicular to the material inflow direction 5 as shown in FIGS. Springback is smaller than the molded product.

Further, using a die having a punch and a die having a pitch P = 12 mm and a convex part height D = 5 mm, a wrinkle pressing force is set to 98 kN, and the pressing load when bending deformation is applied to the side wall part 7 = 3 The result in the case of × 98 kN is shown in FIG. The other conditions were the same as in Example 1. From the results shown in FIG. 6, it can be seen that the same results as in Example 1 are obtained.
In addition, after using a die having no irregularities on the punch and die surfaces in the first step and roughly forming a cross-sectional hat shape, in the second step, the same as in Experimental Examples 1 to 4 is performed on the roughly formed product. Using a die with irregularities in advance, bend with a punch and die working surface in the vicinity of the bottom dead center of the press stroke of the second step on the rough molded product, in the part that has undergone bending back bending deformation by the die shoulder Similar results were obtained when processing was applied.

(A) is an external view of the molded product which concerns on embodiment of this invention, (b) is a partial front view which shows the principal part. (A) is a front view explaining the press work method which concerns on embodiment of this invention, (b) is sectional drawing which shows the shaping | molding state at the time of press molding completion (bottom dead center). (C) is an external view showing the direction in which the convex portion 9 of the punch 1 extends. It is sectional drawing which shows the suitable wave shape formed in the press metal mold | die which concerns on implementation of this invention. It is the schematic which shows the direction of the waveform peak or valley formed in the press metal mold | die which concerns on implementation of this invention. It is a characteristic view which shows the effect of this invention compared with a prior art example. It is another characteristic view which shows the effect of this invention compared with a prior art example. It is explanatory drawing of the method of calculating | requiring the curvature which is a parameter | index of a springback. It is explanatory drawing of the method of calculating | requiring the curvature which is a parameter | index of a springback. It is explanatory drawing of the conventional press work method.

Explanation of symbols

S Metal plate material 1 Punch 1a Punch shoulder 2 Die 2a Die shoulder 2b Die groove 3 Wrinkle presser 4 Wrinkle presser force 5 Material inflow direction 6 Bottom wall part 7 Side wall part 8 Flange part 9, 10 Convex part 11, 12 Punch D Convex part Height d Valley depth P Pitch a Material width b Width of molded product W at the end of molding c Die groove depth θ Die sidewall inclination angle 7a, 7b, 7c Points on sidewalls W0, W Opening width

Claims (7)

The part that was bent and bent back by the die shoulder
A metal plate press-molded product, wherein the metal plate is formed into a corrugated shape in which a plurality of irregularities extending linearly are arranged. The part that was bent and bent back by the die shoulder
A metal plate press-molded product, wherein the metal plate is formed into a corrugated shape in which a plurality of irregularities extending linearly are arranged along the material inflow direction. In the metal plate press working method for drawing and bending metal plates,
Using punches and dies that have a wave-shaped working surface,
In the vicinity of the bottom dead center of the press stroke at which the draw bending is completed,
On the part that has been bent and bent back by the die shoulder,
A method of pressing a metal plate, wherein bending is performed on the working surface of the punch and the die. After using a die that does not have irregularities on the working surface in the first step, and roughly forming into a hat shape in cross section, using a punch and a die in which the working surface is formed into a wave shape in the second step,
In the vicinity of the bottom dead center of the press stroke of the second step for the rough molded product,
On the part that has been bent and bent back by the die shoulder,
A method of pressing a metal plate, wherein bending is performed on the working surface of the punch and the die. A press die that obtains a molded product by drawing and bending a metal plate,
Near the bottom dead center of the press stroke, the surface of the punch that acts on the part of the molded product that has undergone bending and bending back deformation by the die shoulder and the surface of the die are formed into a wave shape with a plurality of unevenness extending linearly. A press die characterized by the fact that A press die that obtains a molded product by drawing and bending a metal plate,
In the vicinity of the bottom dead center of the press stroke, the surface of the punch that acts on the part of the molded product that has undergone bending and bending back deformation by the die shoulder and the surface of the die are arranged in a line along the material inflow direction. A press die characterized by being formed into a wave shape. In the press die according to claim 5 or 6,
At the bottom dead center of the press stroke, the clearance between the punch surface and the die surface acting on the part subjected to bending and bending back deformation by the die shoulder is not less than 1.3 times the thickness of the metal plate material. A press mold characterized by being set to.

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