JP2009274119A - Method of joining metal sheet by caulking - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of caulking-joining metal sheets by which joining strength is improvable by increasing the thickness of a side wall part. <P>SOLUTION: A plurality of metal plates are superposed and arranged on movable blades which are dividedly arranged on the outer periphery of a fixed anvil having a recessed conical surface toward the metal plate in the tip part and, by deforming the upside metal sheet plastically by locally thrusting a columnar punch having a projecting conical surface in the tip part in the metal sheet from the upper part into the metal sheet and also deforming an underside metal sheet plastically by releasing the movable blades respectively individually in the outer peripheral direction, the upper and lower metal sheets are mechanically joined. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for caulking and joining metal plates, which can obtain high joining strength easily and at low cost.

  A spot welding method is widely used as a method for joining a plurality of stacked metal plates. The spot welding method is a joining method in which high joint strength can be stably obtained and productivity is excellent. However, it is difficult to join materials having different thicknesses or different materials. In addition, with plating materials, the plating layer is damaged due to the heat effect on the material, so post-treatment is required, and the copper electrode causes an alloying reaction with the plating layer, so the electrode tip is consumed and the electrode life is less than 5,000 shots. And short. Furthermore, during the joining operation, the molten metal is scattered around and fume is generated, and the working environment is deteriorated.

In addition, a mechanical joining method using a fastener such as a bolt or a rivet is generally performed. In such a joining method, since a fastener is used, cost increases. Furthermore, it is necessary to make a pilot hole in the laminated metal plate in advance, so that the working efficiency is lowered, and part of the fastener protrudes from the upper and lower surfaces of the joined metal plate, which may impair the aesthetic appearance.
Therefore, a caulking joining method may be employed.

  The caulking joining method typified by spot clinching joining is a technique of pressing a stacked metal plate with a punch from one side and plastically deforming and joining the metal plate, and can reduce costs because a fastener is not required. . Furthermore, compared to spot welding, there are few material restrictions such as the ability to join different thicknesses and dissimilar materials, and there is no thermal effect, so there is no need for post-repair in the plating material, and the die life is 100,000. Metal plates can be joined stably over shots. Furthermore, since caulking and joining can be performed by press molding, the synchronism with the press equipment is good and the working environment is also good because there is no fume. Therefore, it is widely used in the fields of automobiles, home appliances, and building materials.

In the conventional caulking and joining method, a punch is pushed into the laminated metal plate from above to form a concave mold, and the metal plate material on the lower surface is plastically flowed outward to obtain a stable joining strength. Therefore, the mold life was short.
Therefore, in Patent Document 1, a lubricity-containing resin film is formed on at least one side of a flat punch tip or a pedestal portion of a die, and caulking is performed. Further, in Patent Document 2, a conical surface having a concave shape is provided at the tip end portion of the punch, and the die tip portion is caulked and bonded using a die having a conical surface having a convex shape.
JP 2005-8953 A Japanese Patent Laid-Open No. 10-305335

The techniques proposed in Patent Documents 1 and 2 are effective as means for extending the mold life. However, it is not sufficient for the problem of obtaining high bonding strength.
The inventors of the present invention first examined the fracture behavior due to the cross tension load in the caulking joint of a Zn—Al—Mg based hot-dip steel sheet. As a result, they found the following. As shown in FIG. 1, from the cross section of the conventional metal plate by caulking, the bonding strength is increased by increasing the side wall thickness S1 and the interlock amount C1 of the upper metal plate in the concave portion formed for bonding. I understood it. Moreover, the fracture | rupture form of the joined metal plate was divided roughly into two types, the omission of an interlock part and the fracture | rupture of the side wall part of an upper board.
Of these two types of fracture modes, the side wall portion has a higher fracture strength than the interlock portion is missing. Therefore, if a sufficient amount of interlock is ensured, it is possible to obtain a high bonding strength by increasing the side wall thickness S1. However, in Patent Documents 1 and 2, the side wall thickness S1 cannot be increased.

As described above, since high-strength bonding cannot be performed by caulking bonding, when high bonding strength is required, it is necessary to increase the number of bonding portions, resulting in an increase in cost.
The present invention has been devised to solve such a problem, and an object of the present invention is to provide a caulking joining method capable of improving the joining strength by increasing the side wall thickness S1.

  In order to achieve the object, the metal plate caulking and joining method of the present invention has a plurality of metal plates on a movable blade divided and arranged on the outer periphery of a fixed anvil having a conical surface concave toward the metal plate at the tip. Are stacked, and a cylindrical punch having a convex conical surface at the tip is locally pushed into the metal plate to plastically deform the upper metal plate, and the movable blades are individually moved in the outer circumferential direction. The upper and lower metal plates are mechanically joined by plastically deforming the lower metal plates by letting them escape.

  According to the present invention, in the concave mold portion formed by caulking, the thickness of the side wall is increased and the interlock portion is formed, so that it is possible to perform caulking bonding having high bonding strength. Since it becomes possible to perform caulking bonding with high bonding strength, it is possible to reduce the number of striking points for caulking bonding, leading to a reduction in cost.

As described above, the conventional caulking joining method is not sufficient for obtaining a high joining strength as compared with the spot welding method. This is because when caulking is performed, the thickness of the side wall and the amount of interlock in the concave portion formed for bonding are difficult to increase.
The inventors of the present invention have made extensive studies on means for increasing the thickness of the side wall part that particularly affects the bonding strength. As a result, it has been found that by devising the upper surface shape of the fixed anvil used for caulking and the lower end surface shape of the cylindrical punch, it is possible to increase the thickness of the side wall of the concave portion formed by caulking. It was.
Details will be described below.

  Normally, in caulking, as shown in FIG. 2A, two metal plates 1 and 2 are placed on a movable blade 6 and then the metal plates 1 and 2 are attached to the blade 6 by a stripper 4. And fix and set. After that, as shown in FIG. 2B, the metal plates 1 and 2 on which the cylindrical punch 3 is set are pressed toward the metal plate to be plastically deformed to join the metal plates 1 and 2 together. At this time, the material is projected along the upper surface of the fixed anvil 5. Thereafter, the blade 6 is moved outward in the radial direction together with the blade 6 movably attached in the radial direction. And an interlock is formed and the metal plates 1 and 2 are joined.

In order to increase the side wall thickness S1 shown in FIG. 1 during the caulking and bonding as described above, the metal plates 1 and 2 are further bulged along the upper surface of the anvil 5 outwardly in the radial direction. It is considered effective to make it easier.
Therefore, in this invention, the shape of the punch 3 and the anvil 5 to be used was devised. That is, as shown in FIG. 3, the tip of the cylindrical punch 3 has a convex conical surface toward the metal plate, and the upper end surface of the cylindrical anvil 5 has a concave conical surface toward the metal plate. .

By making the shapes of the punch 3 and the anvil 5 used as described above, as shown in FIG. 3B, the metal plates 1 and 2 can be easily projected and flown outward in the radial direction. The metal plate can be brought into contact with the anvil 5 while the side wall portion thickness S1 of the metal plate 1 is kept large to form an interlock portion.
Although not shown, conversely, if the tip of the cylindrical punch 3 is a concave conical surface toward the metal plate, the metal plate 1 will be greatly stretched downward when the punch is pressed. The side wall thickness of the plate 1 is reduced. Furthermore, when the upper end surface of the cylindrical anvil 5 is a convex conical surface toward the metal plate, when pressing with a cylindrical punch having a concave conical surface, the material of the metal plates 1 and 2 is moved outward in the radial direction. Since the overhang and flow are performed in the downward direction, the side wall of the metal plate 1 is greatly stretched, and the thickness of the side wall of the metal plate 1 is further reduced.
Therefore, as in the present invention, the tip of the cylindrical punch 3 has a convex conical surface toward the metal plate, and the upper end surface of the cylindrical anvil 5 has a concave conical surface toward the metal plate. The thickness of the side wall portion of the metal plate 1 can be effectively increased.

In addition, it is preferable that the center angles θ1 and θ2 of the cones in the punch 3 and the anvil 5 are equal and about 140 to 160 degrees are used.
When the center angles θ1 and θ2 of the cones in the punch 3 and the anvil 5 are less than 140 degrees, the upper plate of the metal plate does not move below the lower plate of the metal plate when the punch 3 is pressed, so an interlock portion is formed. Cannot join the metal plates. On the other hand, when the angle is increased to exceed 160 degrees, the deformation is almost the same as that of a caulking joint having a normal cylindrical bottom, and the effect of increasing the thickness of the side wall is not generated. Although depending on the thickness of the plate to be joined and the depth of the recessed portion to be formed, the range of θ1 and θ2 is preferably 140 to 160 degrees from the viewpoint of efficient thickening.

An embodiment of the present invention is shown in FIG. As the metal plate 1 and the metal plate 2, a Zn-Al-Mg-based hot-dip steel sheet having a thickness of 1.6 mm having chemical components and mechanical properties shown in Table 1 was used. As a caulking tool, a cylindrical punch 3 having a diameter of 4.5 mm and a fixed anvil 5 having a diameter of 5 mm were used. The tip of the cylindrical punch 3 has a convex conical surface with θ1 of 160 degrees, and the anvil 5 has a concave conical surface with an angle θ2 of the tip of 160 degrees.
In joining the two plates, the metal plate was positioned and set in a state of being superimposed on the blade 6 as shown in FIG. Next, the metal plate was sandwiched between the blade 6 in the stripper 4 and fixed. As shown in FIG. 3B, the cylindrical punch 3 was pressed by 3.5 mm to plastically deform the metal plates 1 and 2 to join the metal plates together. At this time, since the material protrudes along the shape of the concave anvil 5, the blade 6 moves in the radial direction. Thus, as shown in FIG. 4, the metal plate 1 and 2 were pressed against the concave anvil by the cylindrical punch 3, thereby forming the interlock portion while ensuring the side wall thickness.

As a comparative example, crimping and joining were performed using a conventional cylindrical punch and anvil having a flat tip surface as shown in FIG.
The interlock thickness C1 and the side wall thickness S1 of the cross section of the joint were measured for those that were caulked and joined by the method of the present invention and the conventional method. In addition, a cross tension test was performed according to JIS Z3137. The results are shown in Table 2.
The side wall thickness S1 of the present invention is thicker than that of the conventional method as a comparative example, and the cross tension load is increased by 50% as compared with the conventional method. It can be seen that the present invention using a convex conical punch and a concave conical anvil is effective.

The figure explaining side wall part thickness S1 and interlock amount C1 after crimping joining Diagram for explaining the normal crimping method The figure explaining the crimping joining method of this invention Caulking joint sectional view by the caulking joining method of the present invention

Explanation of symbols

1: Metal plate (composite material) 2: Metal plate (composite material) 3: Cylindrical punch
4: Stripper 5: Fixed anvil 6: Movable blade
C1: Interlock amount S1: Side wall thickness

Claims (1)

  A plurality of metal plates are placed on top of a movable blade divided and arranged on the outer periphery of a fixed anvil having a conical surface concave toward the metal plate at the tip, and a convex conical surface is formed at the tip from above. A cylindrical punch is locally pushed into the metal plate to plastically deform the upper metal plate, and the movable blades are individually released in the outer peripheral direction to cause plastic deformation of the lower metal plate to form upper and lower metal plates. A method of caulking and joining metal plates, characterized by mechanical joining.

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