JP5206210B2 - Tailored blank press forming method - Google Patents

Description

  The present invention relates to a press forming method of a tailored blank material for processing a tailored blank material into an automobile part (particularly, an outer panel) by press forming.

  2. Description of the Related Art In recent years, due to increasing demands for ensuring safety and environmental performance of automobiles, the body weight of automobiles has been reduced, but further reduction in body weight has been demanded.

In order to meet such a demand, there is a movement to locally use a material having a large thickness or a material having a high strength only for a portion requiring a high strength among the parts. That is, a technique in which a so-called tailored blank material obtained by joining metal plates having different thicknesses or different materials is used as a material metal plate, and the tailored blank material is processed into a desired shape by press molding is attracting attention. (For example, refer to Patent Document 1).
JP 2006-095596 A

  However, at present, the tailored blank material is mainly applied to the inner plate panel and the skeleton member, and the application to the outer plate panel is small. The reason is that the surface quality (surface accuracy) in the vicinity of the weld line at the time of press forming of the tailored blank material is lowered, which is an obstacle to the application of the tailored blank material to the outer panel.

  An example is shown in FIG. As shown in FIG. 1A, a high-strength, high-thickness metal plate (here, a steel plate having a tensile strength of 440 MPa class and a thickness of 1.0 mm) 11 and a low-strength, low-thickness metal plate ( Here, the surface quality (predetermined) in the vicinity of the weld line 13 when the tailored blank material 10 welded with a steel sheet having a tensile strength of 270 MPa and a plate thickness of 0.7 mm is press-formed (here, frustum overhang forming). The height distribution from the reference position of FIG. 1 (b) is shown in FIG. 1 (b), but the low strength / low plate relative to the high strength / high plate thickness metal plate 11 side with the weld line 13 in between. The thick metal plate 12 side has dropped by 0.12 mm.

  Because of this deterioration in surface quality, the tailored blank material is applied to the outer panel with a quasi-outer surface (a place that cannot be seen without opening the door) and a cover in the vicinity of the weld line. There was a restriction that it had to be limited to the plate part. This was a major factor in the small application of tailored blanks to the outer panel.

  The present invention has been made in view of the circumstances as described above, and when press-molding a tailored blank material, it is possible to obtain good surface quality (surface accuracy). The present invention provides a method for press forming a tailored blank material that can be applied to plate panels and the like.

  In order to solve the above problems, the present inventors first examined the mechanism of surface quality deterioration (occurrence of dent on the outer surface) in the vicinity of the weld line at the time of press forming of the tailored blank material. It was clarified that the mechanism is like this.

  That is, as shown in FIG. 2 (a), a high strength / high plate thickness metal plate 11 and a low strength / low plate thickness metal plate using a press die 20 having a die 21, a blank holder 22 and a punch 23 are used. When the tailored blank material 10 welded 12 is press-molded (here, frustum overhang molding), a relatively large tensile tension acts in a direction orthogonal to the weld line 13, so that the weld line 13 has high strength and high plate thickness. As shown in FIGS. 2B and 2C, a gap 29 is formed between the tailored blank 10 and the punch 23, and welding on the low strength / low thickness metal plate 12 side is performed. It was clarified that the outer surface in the vicinity of the weld line 13 on the low-strength, low-thick metal plate 12 side drops to the punch 23 side by the action of pushing down the vicinity of the wire toward the punch 23 side.

  In view of this, the inventors of the present invention have studied the method for preventing the deterioration of the surface quality in the vicinity of the weld line 13 as described above, and have come up with the following method.

  In other words, a hard rubber is lined on the punch surface that forms the vicinity of the weld line of the tailored blank material and press-molded to exert a force that pushes the vicinity of the weld line to the die side, resulting in low strength and low plate thickness near the weld line. It came to the idea that the phenomenon that the outer surface on the metal plate side falls to the punch side can be avoided.

  Based on the above concept, the present invention has the following features.

[1] When a high-strength, high-thickness metal plate and a low-strength, low-thickness metal plate are welded by a press die having a die and a punch, the vicinity of the weld line of the tailored blank material A press forming method of a tailored blank material, characterized in that a hard rubber is lined on a punch surface for forming a metal and press forming is performed by applying a force to push the vicinity of the weld line to the die side .

  [2] The press molding method of the tailored blank material according to [1], wherein the hardness of the hard rubber is a Shore hardness of 50 HS or more, and the thickness of the hard rubber is 2 mm or more.

  In the present invention, when the tailored blank material is press-molded, it is possible to prevent a drop phenomenon of the outer surface in the vicinity of the weld line and to obtain good surface quality (surface accuracy). As a result, it is possible to significantly expand the application of tailored blank materials to automobile outer panel.

  An embodiment of the present invention will be described with reference to the drawings.

  FIG. 3 is a view showing an embodiment of the present invention. In this embodiment, as shown in FIG. 3A, a press die 20 having a die 21, a blank holder 22, and a punch 23 is used. When the tailored blank material 10 in which the high strength / high plate thickness metal plate 11 and the low strength / low plate thickness metal plate 12 are welded is press-formed (here, kamaboko type overhang), the weld line 13 of the tailored blank material 10 is formed. A hard rubber 24 is lined on the surface of the punch 23 for molding the vicinity, and press molding is performed.

  As a result, a force for pushing the vicinity of the weld line 13 to the die 21 side acts, and as shown in FIGS. 3B and 3C, the vicinity of the weld line 13 on the low strength / low thickness metal plate 12 side. It can be avoided that the outer surface of the lens falls on the punch 23 side.

  In addition, as for the hardness of said hard rubber 24, Shore hardness 50HS or more is preferable, More preferably, it is 70HS or more. In addition, a Shore hardness test shall be measured based on JISZ2246. The lining thickness of the hard rubber 24 is preferably 2 mm or more, more preferably 3 to 5 mm.

  Thus, in this embodiment, when press-molding the tailored blank material 10, the weld line 13 is formed by lining the hard rubber 24 on the surface of the punch 23 that molds the vicinity of the weld line 13 of the tailored blank material 10. It is possible to prevent a drop phenomenon of the outer surface in the vicinity and obtain a good surface quality (surface accuracy). As a result, it is possible to significantly expand the application of tailored blank materials to automobile outer panel.

  In order to confirm the effect of the present invention, as Example 1 of the present invention, as shown in FIG. Hot-dip galvanized steel sheet) 11 and low-strength / low-thickness steel sheet (hot-dip galvanized steel sheet having a tensile strength of 270 MPa and a thickness of 0.7 mm) 12 are press-formed (conical flanking). Went.

  At that time, as Examples 1-3 of the present invention, the hard rubber 24 was lined and press-molded on the surface of the punch 23 for molding the vicinity of the weld line 13 of the tailored blank material 10 under the conditions shown in Table 1. . Further, as Comparative Example 1, press molding was performed using a conventional punch that is not lined with the hard rubber 24.

  And the result of having measured the drop depth of the outer surface of the welding line 13 vicinity in each case is shown in Table 1.

  As shown in Table 1, in Inventive Examples 1 to 3, the sagging depth is reduced as compared with Comparative Example 1, and in Inventive Examples 1 and 2, the effect is remarkable.

  As Example 2 of the present invention, as shown in FIG. 4, a high-strength / high-thickness steel plate (hot-dip galvanized steel plate having a tensile strength of 440 MPa and a thickness of 1.0 mm) 11 and a low-strength / low-thickness steel plate The press-molding (kamaboko-type overhang molding) of the tailored blank material 10 to which 12 (a galvanized steel sheet having a tensile strength of 270 MPa class and a thickness of 0.7 mm) 12 was welded was performed.

  At that time, as Example 4 of the present invention, as shown in FIG. 3, the hard rubber 24 was lined on the surface of the punch 23 for molding the vicinity of the weld line 13 of the tailored blank material 10 and press molding was performed. The hard rubber 24 has a Shore hardness of 70 HS and a lining thickness of 3 mm. Further, as Comparative Example 2, as shown in FIG. 2, press molding was performed using a conventional punch 23 in which the hard rubber 24 was not lined.

  And the result of having measured the drop depth of the outer surface of the welding line 13 vicinity in the comparative example 2 and this invention example 4 is shown to Fig.5 (a) and (b), respectively.

  In Inventive Example 4 shown in FIG. 5B, the sagging depth is significantly reduced as compared with Comparative Example 2 shown in FIG.

It is a figure which shows the drop of the welding line vicinity at the time of press-molding a tailored blank material. It is a figure which shows the drop generation | occurrence | production mechanism of the welding line vicinity in a prior art. It is a figure which shows one Embodiment of this invention. It is a figure which shows the press molding shape in Example 2 of this invention. It is a figure which shows the measurement result of the drop depth of the welding line vicinity in Example 2 of this invention.

Explanation of symbols

10 Tailored Blank Material 11 High Strength / High Thick Metal Plate 12 Low Strength / Low Thick Metal Plate 13 Welding Wire 20 Press Die 21 Die 22 Blank Holder 23 Punch 24 Hard Rubber 29 Gap

Claims (2)

When a high-strength, high-thickness metal plate and a low-strength, low-thickness metal plate are welded with a press die having a die and a punch, the vicinity of the weld line of the tailored blank is formed. A press forming method of a tailored blank material, characterized in that a hard rubber is lined on a punch surface and press forming is performed by applying a force for pushing the vicinity of a weld line to a die side .   The method for press-molding a tailored blank material according to claim 1, wherein the hardness of the hard rubber is a Shore hardness of 50 HS or more, and the thickness of the hard rubber is 2 mm or more.

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