JPH0813425B2 - Spot welding electrode - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electrode for spot welding,
In particular, it relates to an electrode for spot welding of aluminum and an aluminum alloy (hereinafter referred to as aluminum).

[0002]

2. Description of the Related Art Electrodes for spot welding have high conductivity,
High heat conductivity and excellent high temperature strength are required, and electrodes of extrusion hardening type copper alloys such as chromium copper, zirconium copper and zirconium chromium copper have been widely used. recently,
An electrode made of alumina-dispersion-strengthened copper in which fine particles of alumina are dispersed in a copper matrix has also been put into practical use, and great improvements in heat resistance and welding resistance have been observed.

Alumina dispersion strengthened copper electrodes are also used for spot welding of aluminum and aluminum alloys (hereinafter aluminium), but recently they are highly automated and are applied to continuous and high-speed spot welding operations. In such a case, problems often occur in the wear resistance of the electrode tip and the strength of the spot weld.

In order to solve this problem, an electrode has been proposed in which a metal having a high hardness and a high melting point, for example, a thin film of W or the like is formed on a portion of the electrode which comes into contact with a member to be welded (Japanese Patent Laid-Open No. 63-63). However, since this electrode is expensive and its workability is not sufficient, there is a problem in practical use.

On the surface of the tip of the electrode tip, a Co-based alloy or C
An electrode coated with an r-based alloy (Japanese Patent Laid-Open No. 63-30185),
Alternatively, an electrode coated with Al (Japanese Examined Patent Publication No. 60-48275) has been developed, but Co and Cr have a problem in terms of price, and a problem remains in terms of electrode durability. Further, in the case of an electrode coated with Al, in order to reliably improve the electrode life and obtain a high-strength welded portion, sufficient pretreatment is required to remove the oxide film from the aluminum surface that is the member to be welded. However, sometimes it is necessary to completely remove the oxide film on the surface of aluminum by mechanically treating it with a wire brush, which makes pretreatment troublesome.

[0006]

SUMMARY OF THE INVENTION The present invention has been made as a result of studying various metal coatings suitable for spot welding of aluminum in order to solve the above-mentioned conventional problems, and its object is to: Aluminum as the material to be welded
If it performed to spot welding continuously Te, wear of the electrode tip is small, smaller strength reduction of weld, and provides a relatively hassle spot welding electrode in the pretreatment of aluminum member to be welded Especially.

[0007]

In the spot welding electrode according to the present invention for achieving the above object, an Sn coating layer is provided on a portion of an alumina dispersion strengthened copper electrode for spot welding which comes into contact with a member to be welded. It is characterized by

Alumina dispersion strengthened copper has an aluminum content of 0.
05 wt% or more, preferably 0.05-1.7 wt% aluminum
Alumina particles containing
Alumina accounts for 50% or more, and the balance is copper and inevitable impurities.

In order to produce an electrode tip for spot welding of alumina dispersion strengthened copper, the Cu--Al alloy powder having the above structure is internally oxidized by heating it to a high temperature in an oxidizing atmosphere, and the Al component is changed to alumina (Al ₂ O) is a dispersion-strengthened copper powder in which alumina particles are finely dispersed in a copper matrix.
Then, if necessary, excess copper oxide is heated and reduced in a reducing atmosphere, and then the powder is enclosed in a copper cylindrical container and hot extruded, and cold drawn to form a rod having a predetermined diameter. This rod material is cut, or after forging, cut to obtain an electrode tip shape.

After forming the electrode tip shape, the tip of the tip is coated with Sn. As a coating method, a plating method such as electroplating, electroless plating, contact plating, hot dipping, or a method of soldering Sn is used. In addition, S
n, a small amount of Ag, B, Bi, Co, Cr, Fe,
In, Mo, Ni, P, Sb, Te, Ti, Pb, Z
Even if one or more of r and W are contained, there is no change in performance.

The thickness of the Sn coating layer is preferably 0.03 to 400 μm. If it is less than 0.03 μm, the effect of reducing the wear of the electrode tip portion by Sn coating is small, and if it exceeds 400 μm, the coating layer is deformed during spot welding, and the shape of the electrode tip tip portion tends to be improper.

After the Sn coating, an appropriate heat treatment is applied to diffuse Sn into the electrode, and the intermetallic compound of the Cu--Sn alloy is mixed with ε.
It is possible to obtain a more excellent durability electrode by forming phases (Cu ₃ Sn). Preferred heat treatment conditions are a heating temperature of 200 ° C. or higher and a heating time of 10 minutes or longer.

[0013]

The spot welding electrode according to the present invention has the above-mentioned structure, and the Sn coating layer formed on the tip of the electrode tip makes the electrode of the member to be welded on the tip of the electrode tip during welding.
Since it has a function of preventing the aluminum from being picked up and reducing the wear of the electrode, the life of the electrode becomes long.

[0014]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 30% of Ar gas atomized powder of Cu-0.4 wt% Al alloy was used.
0 ° C x 1h Surface oxidation by heating in air, 800 ° C x 5h
The internal oxidation was carried out under the heating conditions of. Then, the product was heated and reduced in hydrogen gas at 500 ° C. for 1 h, pulverized, and then enclosed in a Cu can.
This was extruded as a billet at 900 ° C to a diameter of 30 mm. After extrusion, cold drawing process is used to make a rod with a diameter of 16 mm. From this rod, an electrode tip with an outer diameter of 16 mm and a tip of R100 mm is formed, and a Sn coating layer of 0.06 μm and 3 μm is provided on the tip of the electrode tip by displacement Sn plating. It was The 380 μm thick Sn coating layer was formed by hot dip plating. Displacement plating method: The material is degreased, washed with water, etched in an acid solution consisting of sulfuric acid and nitric acid, washed with water, and then in a bath of "Substar SN" -P2, L2 manufactured by Okuno Seiyaku Co. at 60 ° C. It was plated. Hot dipping method: After degreasing the material, it was immersed in a hot Sn bath.

Example 2 A Sn coating layer having a thickness of 0.06 μm, 3 μm and 380 μm was provided on the tip of an electrode chip manufactured by the same method as in Example 1 by soldering. The Sn coating by soldering was done by applying Sn to the tip of the electrode tip using flux.
The solder was heated by a torch to be melted, and the solder was built up.

Example 3 As in Example 1, electrode chips with Sn coating layers having a thickness of 0.05 μm, 2 μm and 370 μm formed by displacement plating or hot dipping were heated at 200 ° C. for 5 hours in the atmosphere to remove Sn 1 Parts were diffused into the electrode. After the heat treatment, the tip cross section of the tip was observed with a microscope. As a result, Cu-Sn
It was observed that the intermetallic compound ε phase of the alloy was formed.

Example 4 Thickness formed by the same soldering method as in Example 2
Electrode chips with a Sn coating layer of 05 μm, 2 μm and 370 μm were heated to 200 ° C. for 5 hours in the atmosphere to diffuse a part of Sn into the electrode. When the cross section of the tip of the tip was observed with a microscope after the heat treatment, it was found that an intermetallic compound ε phase of Cu—Sn alloy was formed in a part of the structure.

Comparative Example 1 A tip of an electrode chip manufactured in the same manner as in Example 1 was soldered in the same manner as in Example 2 to a thickness of 0.02 μm.
And a 430 μm Sn coating layer.

As a material to be welded, a 5083 alloy softened material with a plate thickness of 1 mm
(O material), as a pretreatment, it is immersed in a commercially available solvent to degrease it, washed with water, then immersed in an alkaline cleaner (sodium carbonate solution containing sodium silicate as an inhibitor, 80 ° C) for 5 minutes, washed with water and dried. .

Next, a pair of electrodes prepared in Examples 1 to 4 and Comparative Example 1 were placed at symmetrical positions on the front and back sides of the pretreated aluminum plate to be welded, and a three-phase low-frequency spot welding machine was used. And welding current (effective current) 2.2K
A, welding time 0.083 seconds, preload 900kgf, welding pressure 300kgf welding conditions 1000 times continuous spot welding.
The tensile shear load of the spot weld was measured every 10 times.
Furthermore, the tensile shear load of the spot weld is JIS Z 3140.
The number of continuous spot weldings of less than 171 kgf / point of class A was measured, and the tensile shear load of the spot welded portion until reaching the number was measured every 10 times of welding and the average value thereof was obtained. Table 1 shows the results.

[0021]

[Table 1]

From the results shown in Table 1, it is recognized that the electrode according to the present invention shows a small decrease in the strength of the welded portion in the continuous spot welding test and exhibits a good performance capable of withstanding continuous use.

[0023]

INDUSTRIAL APPLICABILITY As described above, the spot welding electrode provided by the present invention solves the problems of short-term wear of the electrode tip and reduced strength of the weld during continuous and high-speed spot welding work. In particular, according to the method of covering Sn by soldering, the worn electrode can be easily repaired even at the spot welding site.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Makoto Yonemitsu, Aichi Prefecture, Nagoya City, 3-1, 12th, 1000, Sumitomo Light Metal Industries, Ltd. Technical Research Institute (72) Inventor Masaki Kumagai, Minato-ku, Nagoya, Aichi Prefecture 3 Sumitomo Light Metal Industry Co., Ltd. Technical Research Institute (56) References JP-A 61-226190 (JP, A) JP-A 3-151170 (JP, A) JP-A 52-96946 (JP, A) )

Claims (5)

[Claims] 1. An aluminum or aluminum alloy material
An electrode for spot welding, wherein a coating layer of Sn is provided on a portion of the alumina-dispersed copper reinforced electrode for spot welding which is used as a member to be welded, in contact with the member to be welded. 2. The electrode for spot welding according to claim 1, wherein the Sn coating layer has a thickness of 0.03 to 400 μm. 3. The spot welding electrode according to claim 1, wherein the Sn coating layer is formed by plating. 4. The electrode for spot welding according to claim 1, wherein the Sn coating layer is formed by soldering. 5. A portion of the Sn coating layer diffuses into the electrode to form C
The electrode for spot welding according to claim 1, wherein an intermetallic compound ε phase of a u-Sn alloy is formed.