JP5765818B2 - Method for caulking and joining metal plates - Google Patents

Description

  The present invention relates to a method for caulking and bonding metal plates, and more particularly, to a method for caulking and bonding metal plates having high bonding strength and no in-plane strength anisotropy.

As a method for fixing and joining a plurality of stacked metal plates, a method using a fastener represented by a bolt or a rivet is generally used. However, the method using the fastener is not only costly, but the head of the fastener protrudes from the surface of the metal plate, which may impair aesthetics in handling or appearance. For this reason, welding methods such as spot welding and caulking joining may be employed.
In the spot welding method, there are cases where it is difficult to join materials with different plate thicknesses or different types of materials, and there is a case where post-repair is required for the plated material because of the thermal effect on the material. In addition, the spot welding method involves scattering and fume at the time of joining, and thus there is a risk of deteriorating the working environment.

Since caulking can be joined during press working, the equipment synchronism and working environment are good. For this reason, caulking is frequently used in fields such as automobiles, home appliances, and houses.
However, the caulking joining method has a problem that the joining strength is lower than a method using a fastener or a spot welding method. For example, when joining using a caulking device equipped with a round punch or die, there is a disadvantage that it is weak against the force in the rotational direction along the planar portion of the member to be joined.

In addition, when a crimping device equipped with a square punch or die is used for joining, a sheared surface is generated in the crimped part, so that the direction of the shear strength at the joined part is generated. Although it is high, the shear strength in the parallel direction is not so high, and the joint portion is sheared, so that there is a problem that the cut end of the material exists and the air tightness and water tightness are lowered.
Therefore, the present inventors have proposed a caulking joining method using a three-pronged punch in Patent Document 1.

JP 2010-172922 A

In the method proposed in Patent Document 1, a plurality of metal plates are placed on a movable blade arranged in three on the outer periphery of a three-pronged fixed anvil, and a three-pronged columnar punch is placed on the metal plate from above. The metal plate on the upper surface is plastically deformed, and the movable blades divided and arranged on the outer periphery of the fixed anvil are individually released in the outer peripheral direction to cause the metal plate on the lower surface to be plastically deformed. It is intended to mechanically join metal plates.
However, when a material with low elongation is caulked and joined by the caulking joining method proposed by Patent Document 1 with a trident punch, a crack occurs in the side wall portion where the substantially Y-shaped crossing of the upper plate, and the joining strength is reduced. Was scattered.

  The present invention has been devised in order to solve such problems. Even in the caulking joining method using a three-pronged punch, cracks that are likely to occur at the side wall portions intersecting substantially Y-shaped are provided. An object of the present invention is to propose a caulking joining method for a metal plate that suppresses generation and has high joining strength.

In order to achieve the object of the caulking and joining method of the metal plate of the present invention, a plurality of metal plates are stacked and placed on the movable blade arranged in three parts on the outer periphery of the three-pronged fixed anvil, from above. A metal plate on the lower surface is formed by locally pushing a three-pronged columnar punch into the metal plate, plastically deforming the upper metal plate, and individually disengaging the movable blades arranged separately on the outer periphery of the fixed anvil in the outer peripheral direction. In the method of mechanically joining the upper and lower metal plates by using plastic deformation, a movable blade having a corner R of 0.78 t or more and a radius of the inscribed circle of the punch head plane portion is used as the movable blade. It is characterized by.
However, t is a thickness obtained by adding all the thicknesses of the plurality of metal plates.

According to the method of the present invention, in the caulking joining method using a three-pronged columnar punch and a movable blade moving in three directions, the corner of the movable blade to be used is set to be equal to or greater than 0.78 t so that the vicinity of the substantially Y-shaped side wall portion It is possible to suppress an increase in the line length in the circumferential direction after caulking, to reduce the distortion of the crack risk part, and to set the corner R of the movable blade used to be equal to or less than the radius of the inscribed circle of the punch head plane part. Thus, it is possible to prevent a decrease in shear joint strength due to a decrease in the interlock portion accompanying the expansion of the corner R.
Therefore, according to the present invention, it is possible to suppress the generation of cracks that are likely to occur at the side walls intersecting substantially Y-shaped, and perform caulking bonding having high and stable bonding strength.

Conceptual diagram explaining the caulking and joining method The figure explaining the shape of the punch used for the caulking joining method by a three-pronged punch, an anvil, and a movable blade. The figure explaining the corner R of a movable blade. The figure explaining the inscribed circle radius of the punch head plane part of a three-pronged columnar punch.

FIG. 1 shows a general caulking joining method. After the two metal plates 1 and 2 are stacked on the blade 6, the metal plates 1 and 2 are sandwiched between the blade 6 by the stripper 4, fixed and set, and then the metal plate 1 set by the cylindrical punch 3. , 2 are plastically deformed so as to project the material radially outward from the anvil 5, and the metal plates 1 and 2 are joined.
In general, comparing the joint strength when caulking is performed so that the dimensions of the joint are the same, and when spot welding is performed, the joint strength of caulking is about 20-30% of spot welding. It has become. In addition, there is a problem that it is weak against the force in the rotational direction along the planar portion of the members to be joined.

As described above, the caulking joining method is a simple method, but also has a relatively low joining strength, and thus is one factor that the usage frequency does not increase. Even in a method in which the caulking joint is formed in a substantially cross shape using a four-fork punch and a movable blade that moves in four directions, the in-plane anisotropy of the joint strength cannot be sufficiently eliminated.
As described above, it is proposed in Patent Document 1 that the caulking joint portion is formed in a substantially Y shape by using a tridental punch and a movable blade that moves in three directions. As a result, cracks are likely to occur, and the bonding strength may decrease.

In the caulking joining method using a three-pronged punch excellent in in-plane anisotropy of the joining strength and a movable blade moving in three directions, the generation of cracks at the side wall portion where substantially Y-shaped crosses is suppressed. Thus, intensive studies were conducted to increase the bonding strength.
Considering that the occurrence of cracks is likely to occur on the side wall of the substantially Y-shaped intersection on the upper plate side, particularly when using a metal plate that is difficult to stretch as compared with the case of using a metal plate that is easy to stretch, the material to the part It can be assumed that it is difficult for the inflow to occur.
In the tridental type caulking, when the tridental punch is started to be pushed in, the lower plate is adapted to the R shape of the movable blade, and the thickness of the side wall portion of the upper plate is reduced as the punch is further pushed in. Therefore, the material does not fill the corner R of the approximately Y-shaped intersection of the three-pronged punch. Therefore, it is considered effective to change the corner R of the movable blade in order to easily cause the material inflow of the side wall portions where the substantially Y-shaped crosses occur.
Therefore, the corner R of the movable blade is increased in order to facilitate the inflow of the material into the substantially Y-shaped intersection side wall.

Details of the present invention will be described below.
First, in the caulking joining apparatus including a tridental columnar punch, a tridental fixed anvil, and a movable blade arranged in three parts on the outer periphery thereof as shown in FIG. 2, the corner R of the movable blade is made larger than the conventional one. Is.
The details of the preferred size of the movable blade corner R shown in FIG. 3 will be given later in the examples. However, when the thickness of the metal plate to be joined is t, the occurrence of cracks can be suppressed at 0.78 t or more. did it. However, if the corner R of the movable blade is made too large, the interlock portion is reduced and the shear joint strength is lowered. Therefore, it is necessary to make the radius less than the inscribed circle of the punch head plane portion shown in FIG. is there.

As the two metal plates to be joined, a 1.6 mm thick Zn-Al-Mg plated steel plate having the mechanical properties shown in Table 1 was used.
The three-pronged punch used had a radius of 4 mm, a width of 3 mm, a taper angle of 120 degrees, and a radius of 2 mm where substantially Y-shaped crossing occurred. The three-pronged anvil has a center radius of 8mm, a width of 3.3mm, a height of 4mm, and a radius of 2mm that intersects the approximate Y shape. A pentagonal prismatic movable blade is 10mm long, 8mm wide, and high 4.9 mm was used, and the corner R was variously changed between 2 and 6 mm.

  On the three movable blades arranged on the outer periphery of the anvil having such a shape, positioning was performed in a state where two bonded plated steel plates were stacked. Subsequently, the two plated steel sheets were sandwiched between the blades by a stripper and fixed. The two punched steel sheets were caulked and joined by pressing the punch of the shape with a load of 100 kN from above into the two plated steel sheets set.

  By changing the corner R of the blade to 2, 2.5, 3, 4, 5, 6 mm, a three-pronged punch was pushed in and joined. The number of n is five. The stroke was adjusted so that the remaining thickness of the caulking portion was 1.1 mm, which was high in the shear joint strength in the preliminary experiment. The state of cracks on the side wall portion of the joined body was visually confirmed. Moreover, the tension test was done about the joined body. In the tensile test, the shear tensile strength was measured according to JIS Z 3136, and the average value was arranged. The results are shown in Table 2.

From the results shown in Table 2, it was necessary to set the corner R of the blade to 2.5 mm (0.78 t) or more in order to suppress cracks on the side wall. The shear tensile strength was relatively high and stable with the corner R of the blade having a radius of 4 mm or less of the inscribed circle of the punch head plane portion being 2 to 4 mm.
Therefore, it can be seen that it is necessary to use a blade having a corner R of 2.5 to 4 mm in order to obtain a bonded body having a high shear bonding strength without cracks in the side wall.

Claims (1)

A plurality of metal plates are placed on a movable blade arranged in three parts on the outer periphery of a three-pronged fixed anvil, and a three-pronged columnar punch is locally pushed into the metal plate from above, and the upper metal plate In the method in which the upper and lower metal plates are mechanically joined by plastically deforming the lower metal plates by individually escaping the movable blades separately arranged on the outer circumference of the fixed anvil in the outer circumferential direction. A method for caulking and joining metal plates, characterized in that a movable blade having a corner R of 0.78 t or more and a radius of an inscribed circle of the punch head plane is used as the movable blade.
However, t is a thickness obtained by adding all the thicknesses of the plurality of metal plates.

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