JP2001129652A - Connecting method for aluminum and copper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate their assembling process ad provide a stably connected product in the method for connecting aluminum alloy and copper alloy, by using a method in which copper can be cast simultaneously with aluminum product. SOLUTION: A connecting face of a copper or copper or alloy product such as tough pitch copper 3 and the like is plated with nickel in advance so as to form more than 20 μm thick of a plating layer therein. The plated surface of the copper or copper alloy product is exposed inside the molding die 1. This copper or copper alloy product as tough pitch copper and the like is fitted in a recess 2 inside a molding die 1. Thus, molten aluminum AC4C 4 is poured into the molding die 1, and is then cast in the open air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining aluminum or an aluminum alloy to copper or a copper alloy.

[0002]

2. Description of the Related Art Aluminum alloys are lightweight and excellent in castability, and have various properties such as high conductivity next to copper and corrosion resistance due to an oxide film. On the other hand, copper is also excellent in conductivity and workability, and has been widely used in electric wires and the like.
A joining material of copper and aluminum alloy having such characteristics is very highly required as an electric component. For example, it is often used for grounding a cast product of an aluminum alloy via a copper plate. However,
Such joints between copper and aluminum alloys are mainly formed by physical joining by fitting bolts and nuts, friction welding, brazing, and the like.

[0003]

However, in the physical joining of these joints of copper and aluminum alloy by fitting bolts and nuts, through holes or screw holes must be provided in copper or aluminum alloy. From the beginning, these through holes and screw holes must be formed in copper or aluminum alloy. Therefore, these are troublesome and lead to an increase in cost. Further, friction welding is a method in which materials to be joined are pressed against each other and mechanically moved relative to each other at a contact surface, and frictional heat is used as a heat source. However, some materials are not suitable for relative movement. Some of them are also required to be operated. Also,
Brazing involves melting a metal with a lower melting point than the material to be joined, solidifying it in the narrow gap between the joints, and joining the joints.Brazing work also requires time and skill. It costs. Therefore, if copper can be simultaneously cast at the time of casting an aluminum product, it is considered that a joining process is eliminated and a stable joined product can be obtained. However, copper is highly reactive with the molten aluminum alloy, and diffuses into the molten metal to form a eutectic of Al-Si-Cu having a low solidus temperature at the interface. In many cases, it is not easy to join with a cast-in piece.

The present invention provides a method of joining copper and an aluminum alloy in which copper can be simultaneously cast at the time of casting an aluminum product, thereby reducing the number of assembly steps and providing a stable joined body. Is to solve.

[0005]

According to the first aspect of the present invention, a copper or copper alloy bonding surface is previously subjected to nickel plating to form a plating layer having a thickness of about 20 μm or more. A method of joining aluminum and copper, in which the aluminum or aluminum alloy was placed in a mold and melted was injected into the mold and cast in air. The nickel plating mentioned here includes electroless plating, electroplating and the like.

According to a second aspect of the present invention, a bonding surface of copper or a copper alloy is nickel-plated in advance to have a thickness of about 20 μm.
m or more, forming a plating layer, treating the copper or copper alloy once at a high temperature, placing it in a mold, injecting the dissolved aluminum or aluminum alloy into the mold, and casting it in the air. Was adopted.

[0007]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing the outline of the structure of the method of the present invention. A concave portion 2 for fitting a copper plate is provided in a cast iron mold 1, and a tough pitch copper 3 is installed in the concave portion 2. This tough pitch copper 3 has Ni-
P electroless plating is performed, and this plating layer has a thickness of 20 μm or more. Then, this plating layer is fitted in the recess 2 with the plating layer facing upward. Then, in this mold 1,
The molten aluminum alloy AC4C4 is cast in the atmosphere. Mold temperature is 623K (350 ° C), molten metal temperature is 993K
(720 ° C.). Before casting the molten metal, high purity Ar
The mixture was bubbled with gas and degassed. As a result, FIG.
As shown in the figure, the tough pitch copper 3 was joined to the aluminum alloy AC4C4.

When the plating layer was 5 μm, the tough pitch copper 3 and the aluminum alloy AC4C4 were not bonded, but also here, the aluminum alloy was adhered to the entire surface of the copper and the wettability was good. I understood. Further, a reaction layer with the molten aluminum alloy was confirmed at the copper interface, and pores were observed on the surface of the aluminum alloy. When the plating layer was 10 μm, the reaction layer was observed at the interface as in the case of 5 μm, but did not join. Furthermore, when the plating layer is 100 μm, it does not peel off even after being removed from the mold after casting.
In addition, they were joined even when a strong impact was applied. This was the same result when the plating layer was 20 μm. Observation of the structure of this bonded section with an optical microscope revealed that there was a black band-like reaction layer between the nickel plating layer and the aluminum alloy base material. Therefore, the structure of this reaction layer is S
Observed by EM and EPMA.

According to the SEM observation, the reaction layer at the junction interface that appeared black had two layers, a layer at the junction interface side with the aluminum alloy AC4C, an A layer, a layer at the Ni plating layer side, and a B layer. As a result, when EPMA analysis was performed on these layers, it was found that the A layer near the bonding interface generated an intermetallic compound containing Al and Ni as main components. It was found that by forming this intermediate layer on the bonding surface, a good bonding surface was obtained. It was also found that the B layer had only Ni and P components, but had a higher P component concentration than the Ni plating layer at the time of coating.

[0010] Next, in the case of the 100 µm plating layer, a gap is formed at the joint, but this gap is not seen in the case of the 20 µm plating layer. It is considered that the voids were generated by diffusion of hydrogen contained in the Ni plating layer. Therefore, before the casting, the copper sample was pretreated at a high temperature to diffuse hydrogen in the plating layer and then cast.

First, after the copper sample was heat-treated at 773 K (500 ° C.) for 1 hour, and then cooled and cast, the result was that even bonding was not performed. This is because the surface of the unbonded copper was discolored to green and a thick oxide film was formed by the high-temperature treatment. Next, when the plating surface was polished and cast, the bonding was good, and no void was formed at the interface. Furthermore, when casting was carried out after leaving it in the air at 623 K (350 ° C.) for 1 hour, the bonding was good, and no void was observed at the interface. In the case where no high-temperature pretreatment was performed, voids were also observed on the joint surface. From this result, it was found that the voids were caused by hydrogen existing in the plating layer. However, it has been found that this hydrogen can be diffused in advance by the treatment at 623K in the air, and that the treatment at 773K in the air forms a thick oxide film on the surface. I found out what to do. In the above heat treatment, the treatment in an inert gas atmosphere or in a vacuum to suppress the formation of a thick oxide film eliminates the need for mechanical polishing of the plating surface.

In the above embodiment, the joining of tough pitch copper and aluminum alloy AC4C has been described, but the same applies to other copper or copper alloys or aluminum or aluminum alloys. In the above embodiment, nickel is used for electroless plating. However, similar effects can be obtained by other plating processes.

[0013]

According to the first aspect of the present invention, in joining copper or a copper alloy and aluminum or an aluminum alloy, the joint surface of the copper or copper alloy is nickel-plated in advance.
Forming the plating layer is effective from both aspects of controlling the reaction of copper and improving the wettability. Therefore, according to this method, the joining of copper and aluminum is very good, and the copper can be joined at the same time when the aluminum product is cast. Therefore, assembling steps are reduced as compared with the conventional joining, and no labor is required. This is an efficient joining method.

[0014] The invention of claim 2 provides the above-mentioned claim 1.
In addition to the effects of the invention described in the above item, when the plating layer is thick, the pretreatment at a high temperature provides good bonding.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a joining method according to an embodiment of the present invention.

FIG. 2 is a front view showing a state in which copper and an aluminum product according to the embodiment of the present invention are joined.

FIG. 3 is an explanatory sectional view of a bonding interface according to the embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 mold 2 recess 3 tough pitch copper 4 aluminum alloy AC4C

Continued on the front page (72) Inventor Hidehiro Yokoyama 1-1-1-14 Shinjuku, Shinjuku-ku, Tokyo Nasu Electric Machinery Co., Ltd.

Claims (2)

[Claims] 1. A plating layer having a thickness of about 20 μm or more is formed on a joint surface of copper or a copper alloy in advance by nickel plating, and the copper or copper alloy is arranged in a mold, and the molten aluminum or aluminum alloy is formed. Is injected into the mold and cast in the atmosphere. 2. A bonding layer of copper or copper alloy is previously subjected to nickel plating to form a plating layer having a thickness of about 20 μm or more. A method for joining aluminum and copper, characterized by injecting the cast aluminum or aluminum alloy into the mold and casting in the atmosphere.