JPH0810963A - Resistance spot welding method of aluminum material - Google Patents

Abstract

PURPOSE:To make applicable to various use of aluminum material for automobile, vehicle, aircraft, etc., by welding aluminum material with the input current equivalent to that of mild steel while precisely adjusting electrode force, welding time and welding current. CONSTITUTION:When an aluminum material or aluminum alloy material having a sheet thickness of (t)mm is spot welded, an electrode and sheet are tightly stuck, giving the minimum deformation required to aluminum material, it is required to destroy the oxide film, which is an insulating film of aluminum material surface, by material deformation. To this end, an electrode force is once increased more than 2t (kN). Subsequently, the electrode force is lowered to lower than 1t (kN) so as to lower a degree of tight adhesion between electrode and sheet as well as increase contact resistance and then spot welding is executed. In order to prevent a weld zone from burn through by rapid heat generation due to increased contact resistance, the energizing time is >=0.004sec to <=0.019sec and the required welding current is >=6.1kA to <=13.3kA.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance spot welding method in which a current is instantaneously applied and spot welding is performed while applying a pressing force to an object to be welded through an electrode, and more particularly to an aluminum or aluminum alloy material , Collectively referred to as "aluminum material").

[0002]

2. Description of the Related Art In recent years, in the body parts of automobiles, the use of aluminum materials has been increasing year by year for the purpose of improving fuel efficiency by reducing the weight and improving the efficiency of material recycling. Generally, automobile bodies are assembled by spot welding, but the welding current required for welding is high in welding aluminum materials due to its high electrical conductivity and high thermal conductivity compared to welding steel sheets, and can be used. Welding machines also have the problem that they are limited to those with a large capacity. For this reason,
The equipment conventionally used for welding steel sheets cannot be applied as is, and new equipment for welding aluminum materials must be introduced.

Conventionally, in the case of resistance spot welding of aluminum materials, the welding conditions recommended by WES (Japan Welding Association standard) have been used, and a schematic diagram thereof is shown in FIG. In FIG. 2, the horizontal axis represents time (sec), and the vertical axis represents electrode pressure and welding current, showing the pressurization and current application patterns. The specified values are shown in Table 1. .

[0004]

[Table 1]

As shown in FIG. 2 and Table 1, when the plate thickness is t, the pressing force is in the range of 7.8t to 11t (kN) during forging and 3t to 5t (kN) during energization. The energization time is defined as a value of 0.02 (sec) or more, which is the sum of welding and post heat, depending on the plate thickness, and the welding current is in the range of 18.2t to 47.5t (kA).

[0006]

The welding conditions of WES are as follows:
Despite considering the characteristics of aluminum material,
The current used for resistance spot welding is twice to four times that of steel sheets, and it is difficult to reduce this under any conditions.

An object of the present invention is to provide a resistance spot welding method capable of welding an aluminum material with an electric current equivalent to that of a mild steel plate.

[0008]

[Summary of the Invention] The gist of the present invention is that in the method of spot welding aluminum or aluminum alloy material, when the plate thickness is t (mm), the electrode pressing force is once increased to 2 t (kN) or more. After that, lower the electrode for 1 t (kN) or less and the plate in close contact, and then 0.004 (sec) or more and 0.019 (se
c) This is a resistance spot welding method for aluminum materials in which spot welding is performed by energizing for 6.1t (kA) or more and 13.3t (kA) or less within the following time.

[0009]

In the present invention, the electrode pressure before energization is set to 2 t (k
N) The reason for limiting the above is to give the aluminum material the minimum necessary deformation to bring the electrode and the plate into close contact, and further, the material deformation destroys the oxide film that is the insulating film on the surface of the aluminum material. This is because it also has a function.

Next, the purpose of reducing the electrode pressure to 1 t (kN) or less is to reduce the degree of contact between the electrode and the plate and increase the contact resistance. This value of 1 t (kN) Is considerably lower than the welding condition of 3 to 5 t (kN) of WES. Normally, when the electrode pressure during energization is reduced below the value of the welding conditions of WES, a sudden heat generation occurs due to the increased contact resistance, the welded portion melts down, and an arc is generated in the gap to explode. . The solution to this problem is 0.01
Extremely short energization time of 9 (sec) or less.

Here, the energization time is set to 0.004 (sec) or more in the relation between the plate thickness of the mild steel plate and the current shown in Table 2
Welding current required to obtain a nugget diameter of √t (mm) or more
It is the minimum energization time required for welding with 6.1t to 13.3t (kA). If it is less than this value, the welding current must be increased.

[0012]

[Table 2]

For comparison with the WES welding conditions shown in FIG. 2, FIG. 1 shows a schematic view of the welding conditions of the present invention. In addition,
In the present invention, the setting of the forging pressure and the post heat specified by WES is arbitrary.

[0014]

EXAMPLES Examples of the present invention will be described below.
Resistance spot welding was performed on an aluminum material having a plate thickness of 0.3 to 3.1 mm under the welding conditions shown in Table 3. The welding conditions at this time are also shown in Table 3.

[0015]

[Table 3]

In Nos. 1, 2, 3, 4, 10, and 11 of the method of the present invention, a nugget diameter of 4√t (mm) or more was obtained at a welding current comparable to that of mild steel plates, and good welded joints were obtained. .

On the other hand, in No. 5 of the comparative example, the electrode pressure before energization is low, and the aluminum plate is not deformed enough for the electrode and the aluminum plate to adhere to each other. And the contact resistance increased, resulting in rapid heat generation, melting and welding of the weld, and arcing in the gap to explode.

In Comparative Examples Nos. 6 and 7, since the electrode pressing force during energization was high, the contact resistance was low and required a welding current higher than that of mild steel plate. In No. 8, the electrode and the aluminum plate were not in close contact with each other, so electricity could not be supplied and welding could not be performed.

Since No. 9 of the comparative example has a short energization time,
In order to obtain a nugget diameter of √t (mm) or more, a welding current higher than that of mild steel was required. Also, No.12,
Since 13 had a long energization time, all were blown up.

[0020]

As is apparent from the above description,
Since the resistance spot welding method of the present invention can weld an aluminum material with a make-up current equivalent to that of a mild steel plate, it can be widely used for various applications using an aluminum material such as automobiles, vehicles and aircraft.

[Brief description of drawings]

FIG. 1 is a schematic diagram of welding conditions of the present invention.

FIG. 2 is a schematic diagram of resistance spot welding conditions for aluminum materials recommended by WES.

Claims (1)

[Claims] 1. In the method of spot welding aluminum or aluminum alloy material, when the plate thickness is t (mm), after the electrode pressure is once increased to 2 t (kN) or more,
In the state where the plate is in close contact with the electrode of 1 t (kN) or less,
6.1t (kA) within the time from 0.004 (sec) to 0.019 (sec)
As described above, the resistance spot welding method for an aluminum material is characterized in that spot welding is performed by applying an electric current of 13.3 t (kA) or less.