JPH0544066A - Joining structure of different kinds of materials - Google Patents

Abstract

PURPOSE:To prevent electrocorrosion by covering a reinforcement with a film and by giving structure where the edge part of the end of the reinforcement slightly rises from the surface of a base stock. CONSTITUTION:A base stock 1 formed by the first metal and a reinforcement 2 formed by the second metal having higher natural potential than the first one are given joining of different kinds of materials. Insulating coating material is applied to the whole surface of the reinforcement 2. The edge part 20 of the reinforcement 2 is made to slightly rise from the surface of the base stock 1. The base stock 1 and the reinforcement 2 are fastened with an adhesive 3. Since the insulating property between the edge part 20 and the base stock 1 is secured, electrocorrosion is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dissimilar material joining structure of, for example, an aluminum-based metal and an iron-based metal.

[0002]

2. Description of the Related Art In the case of forming a structural body such as an automobile body, use of an aluminum-based metal as a structural base material has been studied in recent years for the purpose of weight reduction. However, when a structure is formed from an aluminum-based metal, the rigidity is weaker than that of a normally used steel plate and reinforcement is required. However, if this reinforcement is done with aluminum metal,
The material cost and the processing cost increase significantly, resulting in a very expensive structure. Therefore, a method of performing only this reinforcement with a steel plate can be considered.

However, when joining an aluminum-based metal and a steel sheet, there is a problem that a difference occurs in the natural potential of each material and a corrosive battery is formed at the contact portion, so that electrolytic corrosion occurs on the base material. As a method of preventing this electrolytic corrosion, a method of coating at least one of dissimilar metals to insulate it or, as disclosed in JP-A-60-114582, has a lower spontaneous potential than that of a dissimilar bonding material. A method of interposing a packing made of a material is known.

[0004]

However, in the above-described structure used for automobiles, etc., when a reinforcing material made of iron-based metal is coated and bonded to the surface of a base material made of aluminum-based metal by adhesion or the like. Also, it was revealed that electrolytic corrosion occurs at the corners of the reinforcing material. It has been found that this is because it is difficult to secure the insulation property in the edge portion of the steel sheet because the edge portion of the steel sheet is barely coated with the paint and the coating film is hardly formed. However, the method of interposing packing as disclosed in the above publication is not preferable because the number of parts is large and the number of assembling steps is large.

The present invention has been made in view of such circumstances, and an object thereof is to prevent electrolytic corrosion without interposing packing or the like.

[0006]

In the dissimilar material joining structure of the present invention, a reinforcing material formed of a second metal having a higher natural potential than that of the first metal is joined to the surface of a base material formed of the first metal. The dissimilar material joint structure is characterized in that the reinforcing material is covered with a coating film, and the edge portions at the ends are slightly raised from the surface of the base material.

The base material and the reinforcing material are formed of a first metal and a second metal having different natural potentials. For example, when an aluminum-based metal is used as the base material, an iron-based metal, a zinc-based metal, or the like can be used as the second metal.
The aluminum-based metal means aluminum and aluminum alloys. The reinforcing material is usually formed by press molding in a U-shaped cross section and is covered with a coating film. The coating film has an insulating property, and for example, a usual melamine cross-linking type coating film, a urethane cross-linking type coating film and the like can be used.

The reinforcing material and the base material can be joined to each other by mechanical joining such as rivets, but electrolytic joining can be further prevented by joining them with an adhesive. As this adhesive, for example, one having an insulating property such as an epoxy adhesive or a vinyl chloride adhesive can be used. The greatest feature of the present invention resides in that the edge portion of the end portion of the reinforcing material is slightly raised from the surface of the base material. The distance between the edge of the reinforcing material and the surface of the substrate is 0.1 to 10 mm, preferably 0.5 to 1.5 mm. This ensures the insulation between the edge portion where the coating film is not sufficiently formed and the base material, and it is possible to reliably prevent electrolytic corrosion in that portion. It should be noted that the larger this distance is, the higher the insulating property is, but even if the distance is more than this range, the effect is saturated and a defect in the shape may occur.

It should be noted that the edge portion can be easily raised by forming the end portion into a slightly bent shape at the time of press-molding the reinforcing material.

[0010]

In the structure for joining dissimilar materials of the present invention, the edge portion of the end portion of the reinforcing material is slightly raised from the surface of the base material. Therefore, the insulation between the edge portion and the base material is ensured, and electrolytic corrosion can be prevented. Further, since the reinforcing material can be easily formed by press molding, the number of manufacturing steps does not increase and the increase in cost is prevented.

[0011]

Embodiments will be specifically described below with reference to embodiments. (Embodiment 1) FIGS. 1 and 2 show a dissimilar material joining structure of this embodiment. This joining structure is composed of a base material 1 made of an aluminum alloy (aluminum-magnesium) and a reinforcing material 2 having a U-shaped cross section. The reinforcing material 2 is formed of cold rolled steel specified in JIS SPC-SD, and has a coating film with a thickness of 15 μm, which is coated with an epoxy-based coating on the entire surface. And the end of this reinforcement 2 is
The edge portion 20 of the reinforcing material 2 has a shape in which the edge portion 20 is slightly bent upward from the end portion by 5 to 10 mm, and the edge portion 20 of the reinforcing material 2 is lifted by about 1 mm from the surface of the base material 1. And base material 1
A vinyl chloride (PVC) -based adhesive 3 is interposed between the contact portion and the reinforcing material 2.

The reinforcing member 2 is formed by press-forming a steel plate into a U-shaped cross section, and at the same time, both ends thereof are bent and then painted. (Example 2) The configuration is the same as that of Example 1 except that the base material 1 and the reinforcing material 2 are joined by rivets without using a vinyl chloride adhesive. (Example 3) The configuration is the same as that of Example 1 except that the adhesive 3 is changed to an epoxy adhesive. (Comparative Example 1) The configuration is the same as that of Example 1 except that the reinforcing material 2'has a shape without a bent portion as shown in FIG. In the joint structure of Comparative Example 1, the edge portion 20 ′ at the end of the reinforcing material 2 ′ is in contact with the surface of the base material 1 via the vinyl chloride resin adhesive 3. (Comparative Example 2) The configuration is the same as that of Comparative Example 1 except that the rivets are used instead of the adhesive.

[0013]

[Table 1] (Evaluation) The corrosion resistance was evaluated for each of the joint structures described above. The corrosion resistance is evaluated by soaking in salt water at 50 ° C. for 4 hours, drying at 70 ° C. for 2 hours, room temperature for 2 hours, and humidity at 50 ° C. 95% 1.
The test was carried out for 6 hours as one cycle, and was taken out every 50 cycles to examine the occurrence of electrolytic corrosion. The results are shown in Table 1.

From Table 1, in the joining structure of Example 1, 100
No occurrence of electrolytic corrosion was observed up to the cycle, whereas in the structures in which the end portions of the reinforcing material 2 ′ of Comparative Example 1 and Comparative Example 2 were not lifted, electrolytic corrosion occurred at 50 cycles. .. That is, it is clear that bending the ends prevents electrolytic corrosion. Further, in the case of interposing an adhesive, no occurrence of electrolytic corrosion was observed even after the test of 200 cycles, which shows that it is extremely excellent.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a joint structure according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a perspective view of a joining structure of a comparative example.

[Explanation of symbols]

 1: Base material 2: Reinforcing material 3: Adhesive 20: Edge part

Claims (1)

[Claims] 1. A joint structure in which a reinforcing material formed of a second metal having a higher natural potential than that of the first metal is joined to a surface of a base material formed of the first metal, wherein the reinforcing material is coated. A dissimilar material joint structure, characterized in that it is covered with a film and the edge portions at the ends are slightly raised from the surface of the base material.