JPH0811302B2 - Dissimilar metal joining method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for joining two kinds of different metals, for example, two kinds of different metals that form an embrittlement phase during welding due to heat input during welding.

(Prior Art) For example, when different kinds of metals such as steel and Al and steel and Ti are welded to each other, an intermetallic compound may be formed in the joint due to heat input to generate an embrittlement phase. Therefore, satisfactory weld strength cannot be obtained.

Therefore, conventionally, when such materials are used in combination, mechanical fastening with bolts or the like has been used.

On the other hand, in recent years, new proposals have been made regarding the bonding of such dissimilar metals. This proposal is a method of joining dissimilar metals via a clad material made of the same two kinds of metal materials as the dissimilar metals. For example, in the magazine “Light Metal Welding” (vol.27 (1989) No.10, structure joining structure of a hybrid structure of a railway vehicle), when joining a stainless steel plate and an Al plate, FIG. As shown in FIG. 1 (b), a clad material made of stainless steel and Al is used between the stainless steel plate and the Al plate,
The stainless steel plate and the stainless steel surface side of the clad material,
In addition, a method has been proposed in which the Al plate and the Al surface side of the clad plate are sandwiched so as to be in contact with each other and bonded. In addition,
FIG. 1 (a) shows a case where arc welding is performed as a joining means, and FIG. 1 (b) shows a case where spot welding is performed as a joining means.

In this method, if the bonding strength of the clad interface of the clad material used is insufficient, there is a problem in terms of bonding strength. However, the clad interface of the clad material manufactured by a known method such as explosive bonding or rolling causes embrittlement. Since the layer thickness is extremely thin, it is said that there is no problem in the overall bonding strength.

(Problems to be Solved by the Invention) Basically, dissimilar metals as described above can be joined by the above method using a clad material, but problems may occur due to heat input during welding.

For example, if each of the materials that make up the glad material is thick, there is no problem, but if the material is thin, the cladding interface tends to become brittle due to heat input during welding. This is also because the clad interface may be destroyed by low stress.

Therefore, when the arc welding shown in FIG. 1 (a) is performed, the heat input is high, so that the destruction at the clad interface is particularly remarkable, and the lower limit of the thickness of the clad material is 2 m.
It will be about m. If the value is less than this value, embrittlement / breakage occurs at the clad interface.

Further, when the spot welding shown in FIG. 1 (b) is performed, the heat input is low, so that the limit of destruction at the clad interface is slightly improved, but the thickness limit of the clad material is still limited. It is about 1.0 to 2.0 mm, and it is the current situation that it is not possible to join thin materials below that.

As described above, the joining of dissimilar metals is not related to the welding means (arc welding, spot welding) in a straight line, and there is no problem when the thickness of the clad material is large.
There are many home appliances that require a clad material with a thickness of about 1 mm. In this case, the thickness of the clad material is less than 1 mm. There was no

An object of the present invention is to provide a method for joining dissimilar metals, which enables stable joining even when the clad material is thin.

(Means for Solving the Problems) The present inventors have made various studies in order to solve the above problems. As a result, lap resistance welding was used as the joining means,
It was found that the cladding interface was not deteriorated due to the thermal effect when a large current was applied for an extremely short time.

That is, although the conventional energization time is about 5 cycles (60 cycles is 1 second) depending on the plate thickness, the above problems can be solved by energizing for an extremely short time as compared with this. Based on this knowledge, the present invention has been completed.

Here, the gist of the present invention is that a clad material composed of two kinds of the same kind of metals as the kind of the different kinds of metals is sandwiched between different kinds of metals so that the same kind of metals are in contact with each other. In the method of joining dissimilar metals for performing resistance welding, the energization time in the resistance welding is 10 ms or less.

In the present invention, "resistance welding" means spot welding,
It includes projection welding and lap resistance welding such as seam welding.

(Operation) Hereinafter, the present invention will be described in detail together with operation effects.

The present invention is based on, for example, the above-mentioned magazine "Light Metal Welding" (vol.
(1989) No, a structure known as a structure coupling structure of a hybrid structure of a railway vehicle), that is, a clad material made of the same kind of metal as the different kind of metal is provided between different kinds of metals. It is an invention characterized by limiting the energization time at the time of resistance welding to a certain specific range in the technology of resistance welding by arranging so as to face each other.

 First, the reason for limiting the energization time will be described.

The reason for setting the energization time to 10 ms or less is that if the energization time is within this energization time, not the entire area of the joint is heated and joined by heat conduction, but rather, only the necessary joining interface is partially heated and joined. This is because it is difficult to adversely affect the clad interface of the clad material during resistance welding, and even if the clad interface is thermally affected by any chance,
This is because if the energization time is about 10 ms or less, no embrittlement layer is formed at the clad interface.

In addition, when the energization time is shortened, the current value is appropriately increased.

The method according to the present invention has a thickness of each constituent material of 1 m.
Of course, the present invention can be applied to a clad material having a thickness of m or less, and even a clad material such as a foil having a thickness of about 50 μm. In this case, it is desirable to shorten the aforementioned energization time as the thickness of the constituent material becomes smaller, but it goes without saying that even if the maximum value within the range of the present invention is 10 ms, no particular problem occurs. .

The optimum current value differs for each material to be welded, and is determined by the energization time, the shape of the joint, the pressure, etc., and is set so that the required strength can be obtained.

However, if the current value is excessively high, dust will scatter from the joint, a high quality joint will not be obtained, and the joint strength will decrease, so if you select an appropriate current value for each material appropriately for the energization time. good. For example, in the case of joining stainless steel and Al,
When the energization time is 1 ms, the current value is preferably 20 to 60 KA.

Furthermore, it goes without saying that the method according to the present invention can basically be applied to a clad material in which the thickness of each constituent material exceeds 1 mm.

Furthermore, in the above description, Fe and Al have been described as examples of different metals, but the method according to the present invention is applicable to all combinations of different metals that form an embrittlement phase in the weld due to heat input during welding. Can be applied.

Specifically, for example, Fe-based materials and Al-based materials (pure Al and
Including Al alloy. The same shall apply hereinafter), Ti-based materials, Zr-based materials, Ta-based materials, Nb-based materials, or Ni-based materials (pure Ni and
(Including Ni-based alloys), Al-based materials, Ti-based materials, Zr-based materials,
It can also be applied to joining with Ta-based materials and Nb-based materials.

The clad material may be any clad material that is joined with a sufficiently high strength by a known method such as rolling clad or explosive clad, and the method for producing the clad material is not limited at all.

Further, the present invention will be described with reference to Examples,
This is merely an example of the present invention, and the present invention is not limited thereby.

Example Fe (stainless steel) and Al with a total thickness of 0.8 mm
Using the rolled clad material (Fe: 0.4 mm thickness, Al: 0.4 mm thickness) of and by the method according to the present invention, as shown in FIG.
Fe plate (stainless steel) with a thickness of 0.8 mm and 0.8 mm with a thickness of
Spot welding was performed with the Al plate as a dissimilar metal.

Similarly, Fe and Ti, Fe and Zr, Fe and Ta, Ni alloys (Allo
y625) and Al, and various clad materials such as Ni alloy and Ti were prepared, and these metal plates were similarly bonded as dissimilar metals. The thickness of the clad material and each metal plate is
As in the case of joining with, it is 0.8 mm and 0.4 mm.

Then, after joining, perform a cross tension test,
The joint strength was evaluated at the breaking position of each test piece. The cross tension test was carried out with the structure shown in FIG.

The results are summarized in Table 1. The evaluation was carried out by ◯ when the metal plate was broken and by X when the metal plate was broken at the clad interface.

As shown in Table 1, in the sample joined by the method according to the present invention, fracture occurred in the base material portion, which indicates that a joined body having sufficient strength was obtained.

However, when the energization time exceeds 10 ms and becomes excessively large, a brittle phase was generated at the dissimilar material joining interface of the clad material, and thus it was found that a joint having sufficient strength could not be obtained.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to provide a method for joining dissimilar metals which enables stable welding even when the thickness of the clad material is thin.

 The significance of the present invention having such effects is extremely remarkable.

[Brief description of drawings]

1 (a) and 1 (b) are schematic explanatory views showing a method of joining dissimilar metals together, and a schematic explanatory view showing a situation in which arc welding and spot welding are performed as joining means, respectively. FIG. 2 is a schematic explanatory view showing a joining condition in the embodiment of the present invention; and FIG. 3 is a schematic explanatory view showing contents of a cross tension test conducted in the embodiment of the present invention.

Claims (1)

[Claims] 1. A dissimilar metal in which resistance welding is performed by sandwiching between two dissimilar metals a clad material composed of the same two kinds of metals as the dissimilar metals so that the same kinds of metals are in contact with each other. In the joining method, the energization time in the resistance welding is 10 ms or less, the joining method of dissimilar metals.