JP2011218388A - Press forming method excellent in shape freezing property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a press forming method by which the wall warp in vertical wall parts of a press-formed part is prevented.SOLUTION: In a method for press-forming a metallic member product 7 having a hat-shaped cross-sectional shape which has a ceiling part 11, the vertical wall parts 12 and a flange part 13 on both sides or one side, when expressing the flange length of the product by L [mm] and the flange length of a punch by L1 [mm], press forming is performed by using a metal mold 9 which comprises the punch 3 which is 0≤L1/L<1.0, a die 4 and a pad 5. Furthermore, after that, it is preferable to perform re-strike by using the metal mold which comprises a punch provided with a flange part which is 1.0≤L2/L when the flange length of the punch is expressed by L2 [mm] and the die.

Description

  The present invention relates to a press forming method of a metal plate, and more particularly to a press forming method for preventing a spring back that occurs in the case of a high-strength steel plate or an aluminum alloy plate and ensuring good shape freezing property. is there.

  In recent years, high-strength steel plates and aluminum alloy plates have been frequently used for automobile parts, but shape freezing defects that occur when molding them into automobile parts have become a problem. That is, when a metal member product having a hat-shaped cross-sectional shape is formed using a bending die, a shape freezing failure called a spring back occurs, and dimensional accuracy cannot be obtained. This shape freezing defect not only significantly deteriorates the appearance quality of the final product, but also causes welding defects in assembly operations performed after molding. Therefore, prevention of shape freezing defects is particularly important for structural members such as members and frames. ing.

  Springback, which is known as a shape defect frequently observed in bending, is a phenomenon that occurs because the residual stress generated in a metal part product during bending is elastically restored and deformed during unloading. This is because the residual stress is unevenly distributed in the thickness direction. In general, when bending is performed by press working, if the metal mold is released from the mold, the product vertical wall portion is warped due to the spring back of the product.

  In order to solve this problem, Patent Document 1 discloses a spring back solution method for press molding using a punch, a die, and a wrinkle presser. In this method, after press forming to the bottom dead center, the product vertical wall is pressed between the punch and the die as the punch rises to reduce the residual stress. However, in the case of press molding mainly of bending molding such as high-strength parts, the wrinkle presser is often not used, and the invention disclosed in Patent Document 1 prevents wall warpage of the vertical wall portion. Can not.

  Patent Document 2 discloses a springback solution method for press molding having a punch, a die, a pad, and a bending plastic strain imparting mechanism. According to this forming method, it is possible to control the amount of strain of the vertical wall portion by the bending plastic strain imparting mechanism, but the press mold becomes complicated and the equipment cost becomes a problem. In addition, since the amount of bending strain increases by using the bending plastic strain imparting mechanism, it is expected that the residual stress that becomes the starting point of the springback increases and the springback increases.

JP 2004-154859 A JP 2004-154786 A

  An object of the present invention is to provide a press molding method for preventing wall warpage of a product vertical wall portion in press molding mainly consisting of bending.

In order to solve the problem, the gist of the present invention is as follows.
(1) A method of press-molding a metal member product having a hat-shaped cross section having a ceiling portion, a vertical wall portion, and flange portions on both sides or one side, wherein the flange length of the product is L [mm], When the flange length is L1 [mm], it has excellent shape freezing characteristics, characterized by press molding using a punch that satisfies 0 ≦ L1 / L <1.0, and a die composed of a die and a pad. Press molding method.
(2) A method of press-molding a metal member product having a hat-shaped cross-sectional shape having a ceiling portion, a vertical wall portion, and a flange portion on both sides or one side in two steps, and the flange length of the product in the first step Is L [mm], and the punch flange length is L1 [mm], and the intermediate product is press-molded using a punch that satisfies 0 ≦ L1 / L <1.0, and a die consisting of a die and a pad. After that, in the second step, when the flange length of the product is L [mm] and the flange length of the punch is L2 [mm], a punch having a flange portion that satisfies 1.0 ≦ L2 / L, and A press molding method excellent in shape freezing property, characterized in that re-striking is performed using a die made of a die.
(3) The press forming method with excellent shape freezing property according to (1) or (2), wherein the metal member product has a different width in the ceiling in the longitudinal direction.

  According to the present invention, it is possible to obtain a good hat-shaped molded part excellent in dimensional accuracy that prevents the occurrence of wall warpage.

The schematic diagram explaining a wall sled is shown. FIG. 3 shows a schematic diagram of a conventional bending molding process (a) before molding, (b) during molding, and (c) molding bottom dead center. The molding process for explaining the present invention (a) Before molding, (b) During molding, (c) Schematic diagram of molding bottom dead center is shown. The cross-sectional shape of the product and metal mold | die explaining this invention is shown. It is an example of the shape of the metal member products concerning this invention, (a) Overall view, (b) Side view, (c) Plan view is shown. The example of the cross-sectional shape of the metal member products concerning this invention is shown.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  The inventors of the present invention have studied a press molding method for preventing wall warpage of a metal member product having a hat-shaped cross-sectional shape having a ceiling portion, a vertical wall portion, and a flange portion on both sides or one side, and those problems are described below. It was found that it can be solved by the method described in 1.

  In general, when designing a press die mainly for bending, the shape of punch and die is made based on the product shape. When the product shape is a shell model, a new surface considering the plate thickness is created in the shell model of the product. The product surface at this time is a die shape, and the surface considering the plate thickness is a punch shape. The present inventors have found that the spring back (wall warpage) of a metal member product can be greatly reduced by making the flange length of the punch made in this way smaller or less than the flange length of the product. I found out. It was also found that the spring back can be further reduced by designing the flange length of the punch in the first step smaller than the flange length of the product and the flange length of the punch in the second step larger than the flange length of the product.

  The invention of (1) is a method of press-molding a metal member product having a hat-shaped cross section having a ceiling portion, a vertical wall portion, and flange portions on both sides or one side, and the flange length of the product is L [ mm], and when the flange length of the punch is L1 [mm], press forming is performed using a punch that satisfies 0 ≦ L1 / L <1.0, and a die including a die and a pad.

  As shown in FIG. 1, in the press molding mainly consisting of bending, when the product 1 including the ceiling portion 11, the vertical wall portion 12, and the flange portion 13 is formed, the product is compared with the ideal shape 2 indicated by a broken line. Wall warpage tends to occur in one vertical wall portion 12. The generation mechanism is such that the metal plate 6 once bent by the shoulder portion 14 of the die 4 is formed into a vertical wall portion as shown in FIG. 2 showing a conventional molding method using a die 9 comprising a punch 3, a die 4 and a pad 5. 12 is subjected to bending back deformation, and residual stress is generated in the plate thickness direction. On the other hand, in the press molding of the present invention, the amount of bending back deformation at the shoulder portion 14 of the die 4 can be reduced as shown in FIG. 3, so that the spring back can be greatly reduced.

  In order to relieve the residual stress of the vertical wall portion 12 that causes wall warping, it is important to optimally design the flange length of the punch 3. FIG. 4 is a cross-sectional view illustrating a product 7 pressed by a punch 9 according to the present invention and a die 9 including a punch 3, a die 4, and a pad 5. As shown in FIG. When the flange length of the product 7 is L [mm] and the flange length of the punch 3 is L1 [mm], the flange length L1 of the punch 3 is zero when L1 / L = 0 (L1 = 0). Therefore, the amount of bending back deformation at the time of press deformation can be minimized. As a result, springback can be greatly reduced. On the other hand, when L1 / L ≧ 1.0, the bending back deformation amount due to the shoulder portion 14 of the die 4 becomes large. Therefore, the flange length L1 of the punch 3 is such that 0 ≦ L1 / L <1.0. It is preferable that As shown in FIG. 4, the punch flange length L1 is the length of the portion parallel to the flange portion 13 of the pressed product 7, and does not include the curved portion 15 on the flange proximal end side of the punch 3. . The curved surface portion 15 is formed to form a fold from the vertical wall portion 12 to the flange portion 13 of the product 7, and the radius of the cross section is set to the shoulder radius Dr of the die 4 and the plate of the product 7 as shown in FIG. 4. Dr + t plus thickness t. The flange length L of the product is a length protruding from the vertical wall portion 12.

  The invention of (2) is a method of press-molding a metal member product having a hat-shaped cross-sectional shape having a ceiling portion, a vertical wall portion, and a flange portion on both sides or one side in two steps. When a product flange length is L [mm] and a punch flange length is L1 [mm], a punch that satisfies 0 ≦ L1 / L <1.0 and a die and a die are used. After the product is press-molded, in the second step, when the flange length of the product is L [mm] and the flange length of the punch is L2 [mm], a flange portion satisfying 1.0 ≦ L2 / L is formed. It is characterized in that the re-striking is performed using a die including a punch and a die provided.

  In the case of press molding in one step, the spring back reduction effect can be obtained by the invention of (1) above, but for the purpose of correcting the shape freezing failure due to the opening of the punch shoulder or die shoulder, the second step is listed. It is more desirable to perform like-like press molding. In addition, when a part shape such as a part mounting portion exists on the flange surface of the product 7, the part shape may not be transferred to the product flange surface by the one-step press molding of the invention of the above (1). In the second step, it is desirable to perform press-molding by wrist-like using a punch provided with a flange portion.

  In the invention of (3), the metal member product is characterized in that the width of the ceiling is different in the longitudinal direction. In order to obtain the effect of the present invention, it is assumed that one or both of the products have the flange portion 13, but the width of the cross-sectional shape of the product is not constant, for example, as shown in FIG. The effect of the present invention can be similarly obtained in different products.

  As an example of the present invention, press forming was performed using a steel plate having a plate thickness of 1.2 mm and a tensile strength of 780 MPa. In order to examine the effect of the present invention, when the flange length L1 of the punch 3 is smaller than the flange length L of the product (two types of L1 / L = 0.25, 0.50) and zero (L1 / L1 / L0). A press test of L = 0) was performed. In addition, after pressing the first step with a punch with L1 / L = 0.25, the product has the same flange length as that of the punch (L2 / L = 1) and a re-striking using a die. A test was also conducted. As a comparative example, a one-step press test was performed using a normal mold (when the punch flange length L1 is equal to the product flange length L; L1 / L = 1.0).

  As shown in FIG. 5, the product shape is 1000 mm in length, the product width is different in the longitudinal direction, the cross-sectional shape is S1 in FIG. 6, and the opposing vertical wall portions 12 of the hat-shaped cross section are parallel to each other. It was. For evaluation after pressing, the displacement amount W before and after the spring back at the product die shoulder R stop of the cross section at a position 30 mm away from the end portion on the narrow side of the product was measured. The results are shown in Table 1.

  As Example 2, the same steel type as in Example 1 was used, and as shown in FIG. 5, one-step press molding was performed to form a product shape having a different product width in the longitudinal direction. In order to examine the effect of the present invention, the influence of the cross-sectional shape of the part on the wall sled was examined. As a comparative example, a press test using a normal mold (when the flange length L1 of the punch is equal to the flange length L of the product; L1 / L = 1.0) was performed.

  The cross-sectional shape of the product is S2 to S6 in FIG. 6, S2 is the height of the vertical wall portion 12 of S1 is different on the left and right, S3 is a cross-sectional shape of the opposite vertical wall portion 12 of S1, and S4 , A part of the ceiling part 11 of S1 is formed in a C shape, S5 is a thing in which the height of the vertical wall part 12 of S3 is different on the left and right, and S6 has only one side of the flange part 13 of S1. did. In either case, the product was designed so that the right side of the cross section in FIG. 6 is the curved side of the product vertical wall portion 12 in FIG. The ratio (L1 / L) between the flange length L1 of the punch and the flange length L of the product in the example of the present invention was 0.25. Evaluation after pressing was the same as in Example 1. The results are shown in Table 2.

  As a result of the above Examples 1 and 2, the present invention was able to obtain a hat-shaped molded part with improved dimensional accuracy over the comparative example and excellent dimensional accuracy.

  The present invention can be applied to a press forming method of a metal plate such as a high strength steel plate or an aluminum alloy plate.

1 Product 2 (where wall warp occurred) Ideal shape 3 Punch 4 Die 5 Pad 6 Metal plate 7 (Pressed) Product 9 Mold 11 Ceiling 12 Vertical wall 13 Flange L1 Punch flange length L Flange length Dr Die shoulder radius t Product thickness

Claims (3)

A method of press-molding a metal member product having a hat-shaped cross-sectional shape having a flange on one side or a ceiling part, a vertical wall part, and one side,
When the flange length of the product is L [mm] and the flange length of the punch is L1 [mm], press using a punch that satisfies 0 ≦ L1 / L <1.0, and a die consisting of a die and a pad A press molding method having excellent shape freezing property, characterized by molding. A method of press-molding a metal member product with a hat-shaped cross-sectional shape having a flange on one or both sides of a ceiling part, a vertical wall part, and one side,
In the first process, when the flange length of the product is L [mm] and the flange length of the punch is L1 [mm], a punch that satisfies 0 ≦ L1 / L <1.0, a gold consisting of a die and a pad Press the intermediate product using a mold,
After that, in the second step, when the flange length of the product is L [mm] and the flange length of the punch is L2 [mm], the punch and die having a flange portion satisfying 1.0 ≦ L2 / L A press molding method with excellent shape freezing property, characterized in that re-striking is performed using a mold made of   The press forming method with excellent shape freezing property according to claim 1, wherein the metal member product has a width of a ceiling portion different in a longitudinal direction.

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