JP2020093285A - Method of joining dissimilar metals - Google Patents

Abstract

PROBLEM TO BE SOLVED: To bond dissimilar metals while suppressing generation of intermetallic compounds.
A lower metal material (21) and an upper metal material (22) having a higher absorption rate of laser light than the lower metal material (21) and a melting point higher than that of the lower metal material (21) are overlapped with each other to form an upper metal material. 22 is a method of joining dissimilar metals in which upper metal material 22 is irradiated with laser light from above 22 and the upper metal material 22 is melted to weld both metal materials. Has an uneven area 22a having an uneven shape, and the uneven area 22a is irradiated with a laser beam having energy for melting the upper metal material 22.
[Selection diagram] Figure 1

Description

The present invention relates to a method for joining dissimilar metals using a laser.

In manufacturing a secondary battery, a connection terminal is formed by welding an aluminum material and a copper material. Conventionally, as a technique in such a field, there is JP 2012-61474 A. In the method of joining dissimilar metals described in this publication, it is described that only one of the dissimilar metals adjacent to each other is melted and joined by changing the reflectance of each metal in a state of being in close contact with each other.

JP 2012-61474 A

However, according to the above-described conventional joining method, if the laser irradiation area is small and there is a gap in the processed portion of the dissimilar metal, normal joining cannot be performed. Therefore, the dissimilar metals must be in close contact with each other, but the precision of the end faces of the dissimilar metals is important, and special processing is required, resulting in high cost.

Further, since the dissimilar metals are in close contact with each other, heat conduction is large, and heat conduction that cannot be controlled is likely to occur. Here, when the melting points of the two kinds of metals are close to each other, due to this heat conduction, the metal member which is not the object of melting may melt more than expected and a large amount of intermetallic compound may be generated. For example, when the intermetallic compound is an intermetallic compound of aluminum and copper, the intermetallic compound has a property of being hard and brittle, so that a large amount of intermetallic compound is generated and mechanical strength is weakened. Become.
The present invention provides a method for joining dissimilar metals, which suppresses the formation of intermetallic compounds.

The method for joining dissimilar metals according to the present invention comprises a lower metal material, and an upper metal material having a higher absorption rate of laser light than the lower metal material and having a higher melting point than the lower metal material. A method of joining dissimilar metals in which the upper metal material is overlapped and the upper metal material is irradiated with laser light from above the upper metal material to melt the upper metal material and the two metal materials are welded together. An uneven region having an uneven shape is formed in a region hit by the contact point, and the uneven region is irradiated with laser light having energy for melting the upper metal material.
Thereby, it is possible to suppress the melting of the lower metal material and to bond the upper metal material by melting.

This makes it possible to provide a method for joining dissimilar metals in which the formation of intermetallic compounds is suppressed.

It is a figure which shows the outline of a joining apparatus. It is a figure which shows an example of the surface of an upper side metal material. It is a figure of an example of the surface of a lower metal material. It is the figure which showed the flow of the welding by the joining apparatus. It is a figure showing the state where the upper metallic material and the lower metallic material were welded appropriately.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the bonding apparatus 1 includes a laser irradiation unit 11 and a mounting unit 12 for mounting the work 2 to be laser-irradiated.

Two different kinds of metals are used for the work 2. As the work 2, a lower metal material 21 made of aluminum and placed on the placing portion 12 and a copper material placed on the upper side of the lower metal material 21 placed on the placing portion 12 And the upper metal member 22 to be disposed.

The laser irradiation unit 11 irradiates the work 2 with a laser. Specifically, the laser irradiation unit 11 includes a laser oscillator, a laser head, a control unit that controls the energy intensity of the laser light, the position at which the laser light strikes the work 2, and the like. For example, the laser head of the laser irradiation unit 11 is arranged above the work 2, and irradiates the upper surface of the upper metal material 22 with the laser light emitted from the laser head.

The lower metal material 21 is a plate of aluminum material. The lower metal material 21 has a good surface roughness in order to reduce the laser absorption rate when the laser light from the laser irradiation unit 11 is irradiated.

FIG. 2 is a diagram showing a state where the surface roughness is improved in order to reduce the laser absorptance of the surface of the lower metal material 21.

The upper metal member 22 is a copper plate. The upper metal material 22 is arranged on the lower metal material 21, and the upper metal material 22 may or may not be in close contact with the lower metal material 21. That is, it is sufficient that the upper metal material 22 can contact the lower metal material 21 while maintaining the molten state when the laser light is irradiated from the laser irradiation unit 11. The upper metal material 22 and the lower metal material 21 are overlapped or fillet welded.

The upper metal material 22 has a lower melting point than the lower metal material 21, and is more easily melted than the lower metal material 21.

Further, the upper metal material 22 is formed to have a poor surface roughness in order to increase the laser absorption rate when the laser beam is irradiated from the laser irradiation section 11. For example, an uneven region 22a having an uneven shape is formed on the upper surface of the upper metal material, and the uneven region 22a is irradiated with laser light. The unevenness area 22a has a high laser absorption rate.

FIG. 3 is a view showing a state in which the surface of the upper metal material 22 is roughened by a laser marker to increase the absorptance, thereby forming the concavo-convex region 22a.

Here, the operation of welding the lower metal material 21 and the upper metal material 22 by irradiating the laser light will be described with reference to FIG.

As shown in FIG. 4A, first, the lower metal material 21 and the upper metal material 22 are mounted on the mounting portion 12. The laser irradiation unit 11 is a top surface of the upper metal material 22, and particularly irradiates a portion (see FIGS. 1 and 2) where the uneven region 22a is formed with laser light.

As shown in FIG. 4B, the upper metal material 22 starts melting by absorbing the laser light emitted from the laser irradiation unit 11.

Here, even when the lower metal material 21 is in a state of being irradiated with the laser light emitted from the laser irradiation unit 11, the lower metal material 21 has a low laser absorption rate, Since the material has a higher melting point than the metal material 22, melting is suppressed.

As shown in FIG. 4C, the molten upper metal material 22 contacts the lower metal material 21. At this time, since the upper metal material 22 is in a sufficiently heated state, the lower metal material 21 is slightly melted and joined by heat conduction. At this time, the intermetallic compound is hardly produced.

After that, in the laser irradiation unit 11, when the upper metal material 22 and the lower metal material 21 are sufficiently welded, the irradiation of the laser light is stopped.

By performing welding in this manner, as shown in FIG. 5, welding is performed in the state where a slight amount of intermetallic compound exists at the joint interface, and the strength can be stabilized.

Therefore, it is possible to easily melt the upper metal material 22 by forming a concavo-convex shape in the portion irradiated with the laser light and increasing the absorption rate of the laser light. Further, the upper metal material is easily melted, and the lower metal material is hard to be melted. The two metal materials are joined while the lower metal material is slightly melted by heat conduction of the melted upper metal material. As a result, it is possible to suppress the mixing amount of the two melted metals, and it is possible to suppress the formation of intermetallic compounds.

The present invention is not limited to the above-mentioned embodiments, but can be modified as appropriate without departing from the spirit of the present invention. For example, although the lower metal material 21 is an aluminum material and the upper metal material 22 is a copper material, the material is not limited to these. That is, another metal material having a high melting point can be used as the lower metal material 21, and another metal material having a low melting point can be used as the upper metal material 22.

DESCRIPTION OF SYMBOLS 1 Joining apparatus 2 Work 11 Laser irradiation part 12 Mounting part 21 Lower metal material 22 Upper metal material 22a Uneven area

Claims (1)

A lower metal material and an upper metal material having a higher absorptance of laser light than the lower metal material and having a higher melting point than the lower metal material are stacked, and laser light is applied from above the upper metal material. Is a method for joining dissimilar metals, in which both metal materials are welded by irradiating the upper metal material and melting the upper metal material,
An uneven region having an uneven shape is formed in a region of the upper metal material exposed to the laser beam,
A method for joining dissimilar metals, wherein the uneven region is irradiated with laser light having energy for melting the upper metal material.