JPH07214337A - Resistance welding method of low electric resistant metal member - Google Patents

Abstract

PURPOSE:To provide the spot welding method of Al alloy rolled sheet to attain low electric current. CONSTITUTION:In spot welding Al alloy rolled sheets 21, 22, oxidizing treatment is applied on the contact face with parts to be welded 31, 32 of electrodes 41, 42. Oxidized films 11, 12 having electric resistance higher than the parts to be welded 31, 32 are formed. By this method, the heat generating quantity between the electrodes 41, 42 and parts to be welded 31, 31 is increased, rapid temp. rise is generated between both parts to be welded 31, 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance welding method for a low electric resistance metal member, and more particularly to an improvement in a method for resistance welding a low electric resistance metal member of the same material type.

[0002]

2. Description of the Related Art Al-based rolled plates, which are low electric resistance metal members, have not only low electrical resistance but also high thermal conductivity. Therefore, when spot welding between these Al-based rolled plates,
A large current is required to raise the temperature of the welded part.

Therefore, conventionally, in order to reduce the current, a steel plate having a high electric resistance is interposed between the electrode and the welded portion of the Al-based rolled sheet (Japanese Patent Laid-Open No. 57-56175).
(See the official gazette).

[0004]

However, since the conventional method is an external heating method in which the metal plate is first heated in the welding process and the heat generated is used to heat the welded portion, the nugget is the surface of the welded portion. There is a problem that it is exposed to the surface and easily welds to the metal plate.

In view of the above, it is an object of the present invention to provide the resistance welding method capable of avoiding the exposure of the nugget on the surface of the welded portion and achieving a low current.

[0006]

According to the present invention, in resistance welding a low electrical resistance metal member of the same material type, an oxidation treatment is applied to a contact surface of an electrode with a welded portion, and the welded portion is subjected. It is characterized by forming an oxide film having a higher electric resistance than that.

[0007]

In the case of resistance welding a low electric resistance metal member, the electric resistance between the electrode and the welded portion is higher than that between the welded portions. Therefore, heat is mainly generated between the electrode and the welded part, and the generated heat is dissipated from one electrode side to the other electrode side, so that the temperature between both welded parts becomes the highest and melting starts. , A nugget is formed. In this case, the temperature rise between the electrode and the welded part is suppressed by the radiation and heat radiation to the electrode.

Therefore, if a means such as forming an oxide film having a higher electric resistance than the welded portion on the contact surface of the electrode with the welded portion is adopted, the amount of heat generated between the electrode and the welded portion is increased. As a result, it is possible to rapidly raise the temperature between the welded parts, which makes it possible to reduce the current and prevent the nugget from being exposed on the surface of the welded parts.

[0009]

EXAMPLES Examples in which the present invention is applied to spot welding as resistance welding will be described.

As a low electrical resistance metal member of the same material type, A
A plurality of rolled plates made of 1-Mg-based alloy (A5182 material,
The thickness was 1.2 mm, the specific resistance (room temperature) was 5.2 μΩcm, and the thickness of the oxide film was 10 nm).

Outer diameter 16 mm, tip radius (R) 10
Oxidation treatment was performed on the contact surface of the 0 mm plurality of Cu electrodes with the welded portion, that is, the tip surface to form oxide films having different thicknesses t. This oxidation treatment is performed by an extremely simple method in which the tip end surface of the Cu electrode after dressing is heated to 200 ° C. in the atmosphere and kept under the heating, and the thickness t of the oxide film is the heating and holding time. Regulated by The specific resistance of this oxide film is 10 ¹⁴ Ωcm or more, which is about 10 ²⁰ times the specific resistance of the rolled plate.

[0012] As shown in FIG. 1, selects the oxide film ₁ 1, 1 ₂ of the thickness t is equal to two Cu electrodes 4 _1, 4 _2, two between them Cu electrodes 4 _1, 4 ₂ The welded parts 3 ₁ and 3 ₂ of the rolled plates 2 ₁ and 2 ₂ are arranged in close contact with each other, and then the welded parts 3 ₁ and 3 ₂ are pressurized with a pressing force of 400 kgf, and at the same time, a single-phase rectifying power source is used. Both Cu under the condition of energization time 8 cycles
Spot welding was performed by energizing between the electrodes 4 ₁ and 4 ₂ , and as shown in FIG. 2, both welded parts 3 ₁ and 3 ₂ were joined via a nugget 5.

The thickness t of the oxide films 1 ₁ and 1 ₂ and JI
The relationship between the current value and the distance d from the surface of the welded portion to the nugget 5 at which the required nugget diameter D = 5.5 mm specified in the SA class was obtained and the results shown in Table 1 were obtained. In the column of the thickness t of the oxide film in the table, the parentheses show the heating and holding time.

[0014]

[Table 1] As is clear from Table 1, the current value decreases as the thickness t of the oxide films 1 ₁ and 1 ₂ increases. In particular, oxide films 1 ₁ , 1
By setting the thickness t of ₂ to 10 nm ≦ t ≦ 100 nm, it is possible to achieve a low current. However, oxide film ₁ 1, 1 ₂ of the thickness t of t <Cu electrode 4 _1, 10 nm,
4 ₂ and the welded parts 3 ₁ , 3 ₂ generate less heat,
Therefore, the degree of lowering the current is low. On the other hand, t> 100nm
Then, since the heat generation amount becomes excessive, the nugget 5 is exposed on the surfaces of the welded parts 3 ₁ , 3 ₂ and the Cu electrodes 4 ₁ , 4 ₂ and the nugget 5 are easily welded.

The electrodes 4 ₁ and 4 ₂ may be made of a Cu alloy, and in this case as well, the oxide films 1 ₁ and 1 ₂ are formed by the same simple method as described above. The present invention is also applied to seam welding and the like.

[0016]

According to the present invention, an oxide film having a high electric resistance is formed on the contact surface of the electrode with the portion to be welded in resistance welding of the low electric resistance metal member of the same material type. By adopting the means, it is possible to achieve a low current without lowering the welding strength and to prevent the nugget from being exposed on the surface of the welded portion.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the start of spot welding.

FIG. 2 is an explanatory diagram showing the end of spot welding.

[Explanation of symbols]

1 ₁ , 1 ₂ Oxide film 2 ₁ , 2 ₂ Al alloy rolled plate (metal member) 3 ₁ , 3 ₂ Welded part 4 ₁ , 4 ₂ Cu electrode 5 Nugget

Claims (4)

[Claims] 1. A low electrical resistance metal member (2 ₁ ,
Hit the resistance welding 2 _2), is subjected to oxidation treatment on the contact surface between the electrode (4 _1, 4 ₂₎ of the weld (3 _1, 3 _2),
A resistance welding method for a low electric resistance metal member, which comprises forming an oxide film (1 ₁ , 1 ₂ ) having a higher electric resistance than the welded parts (3 ₁ , 3 ₂ ). 2. The electrodes (4 ₁ , 4 ₂ ) are made of Cu or C.
The resistance welding method for a low electrical resistance metal member according to claim 1, wherein the resistance welding method is constituted by one of u alloys. 3. The oxide film (1 ₁ , 1 ₂ ) has a thickness t of 1
The resistance welding method for a low electric resistance metal member according to claim 1, wherein 0 nm ≦ t ≦ 100 nm. 4. The resistance welding method for a low electric resistance metal member according to claim ₁ , wherein the metal member (2 ₁ , 2 ₂ ) is made of an Al alloy.