JPH11342477A - Spot welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a spot welding method of high quality by preventing the formation of burrs due to intermediate dispersion. SOLUTION: In a spot welding method, plural metal members 1, 2 with different melting points are overlapped, nipped between a pair of electrodes comprising the first electrode 13 and the second electrode 4, pressurized, and energized, so as to be joined. A concave part 14 on a surface of the first electrode 13 contacts with the metal member 1 with low melting point, and the metal members 1, 2 with different melting points are held between a pair of the electrodes 4, 13. Under such a condition, pressure and current are applied to the metal members for joining.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a spot welding method, and more particularly, to the prevention of burrs generated around an interface joint between metal plates when welding a plurality of metal plates having different melting points. .

[0002]

2. Description of the Related Art FIGS. 8 and 9 show a conventional spot welding apparatus.
It will be explained by. FIG. 8 is a sectional view showing the vicinity of a spot welding electrode when an aluminum alloy plate is overlapped on a steel plate and spot-welded. FIG. 9 is a front view and a side view of the upper electrode and the lower electrode shown in FIG. 8 and 9, in the spot welding apparatus, the upper electrode 3 and the lower electrode 4 are made of chromium copper, and the ends of a substantially cylindrical column are formed in a dome shape, and are connected to the negative pole and the positive pole of the DC power supply 6, respectively. Have been. The dimensions of the upper electrode 3 and the lower electrode 4 are, for example, 2 mm in outer diameter.
0 mm, and R of the tip surface is 150 mm.

Here, the reason why the steel plate 2 is used as the positive electrode of the DC power supply 6 is that spot welding using a DC power supply generally
This is because heat generation is large on the positive electrode side and the melting point of the steel plate 2 is higher than that of the aluminum alloy plate 1 so that it is difficult to melt.

Next, the operation of the spot welding apparatus configured as described above will be described with reference to FIGS.
For example, an aluminum alloy plate 1 having a thickness of 1.5 mm and an A5052 material is superimposed on a steel plate 2 having a thickness of 4.0 mm and a SPHC material as a base material, and sandwiched between an upper electrode 3 and a lower electrode 4. When a pressure of 5880 N is applied and a DC current of 20,000 A is applied for 0.83 seconds with the steel plate 2 as the positive pole, the fusion diffusion width is formed at the interface between the aluminum alloy plate 1 and the steel plate 2 as shown in the schematic diagram of the welded section shown in FIG. Is very narrow and the interface bonding portion 5 close to the pressure welding is formed.

[0005]

However, when the interfacial joint 5 is peeled off, as shown in the schematic diagram of the peeled surface of the welded portion of the aluminum alloy plate 1 shown in FIG. That is, the burrs 7 are generated by the scattering and adhere to the periphery of the interface bonding portion 5.

Therefore, for example, when spot-welding a fin 11 made of an aluminum alloy plate having a U-shaped cross section to a base 12 made of a steel sheet as shown in FIG. There is a problem that work to be performed is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a spot welding method of high productivity and high quality by preventing formation of burrs due to scatter. Things.

[0008]

According to a first aspect of the present invention, there is provided a spot welding method wherein a plurality of metal bodies having different melting points are overlapped and sandwiched between a pair of electrodes comprising a first electrode and a second electrode. In a spot welding method of joining by applying a current by applying pressure, a concave portion on the surface of the first electrode is brought into contact with the metal body having a low melting point, and a plurality of metal bodies having different melting points is sandwiched between the pair of electrodes; It is characterized in that bonding is performed by applying an electric current under pressure.

A spot welding method according to a second aspect of the present invention is characterized in that the first electrode is connected to the negative pole of the DC power supply, and the second electrode is connected to the positive pole of the DC power supply.

[0010] A spot welding method according to a third aspect of the present invention is characterized in that the concave portion on the surface of the first electrode has a shape in which a gap is formed in the superposed surface of the metal body.

[0011] The first aspect of the spot welding method according to the fourth invention.
The concave portion on the surface of the electrode described above is characterized in that the surface of the expanded portion of the metal body having a low melting point has a shape substantially along the inner surface of the concave portion.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing the vicinity of an electrode for spot welding when an embodiment of the present invention is spot-welded by stacking an aluminum alloy plate on a steel plate, and FIG. 2 is a front view and a side view of the upper electrode of FIG. It is. In the figure, the same reference numerals as those in the related art indicate the same or corresponding parts,
Description is omitted.

In FIG. 1 and FIG. 2, a spot welding apparatus is provided with an upper electrode 13 as a first electrode made of chromium copper.
Is formed in a central portion of the electrode surface in contact with the aluminum alloy plate 1 as a base material having a low melting point, and a concave portion 14 having a predetermined size is formed.
Is provided so as to be in contact with the base material at the peripheral portion 15 of the concave portion 14. In addition, the lower electrode 4 as a second electrode
Is the same as in the prior art.

Next, the operation of the spot welding apparatus configured as described above will be described with reference to FIGS.
For example, length 100 mm, width 50 mm, plate thickness 1.5 mm
In a state where an aluminum alloy plate 1 of A5052 material and a steel plate 2 of SPHC material having a thickness of 4.0 mm cut to the same dimensions and sandwiched between an upper electrode 13 and a lower electrode 4, a pressing force of 5880 N And a DC current of 20,000 A is applied for 0.83 seconds with the steel plate 2 as the positive electrode, and as shown in the cross-sectional view near the electrode after welding shown in FIG. 3, the fusion diffusion width is formed at the interface between the aluminum alloy plate 1 and the steel plate 2. Is very narrow and is close to pressure welding, and no burrs are generated around the interface joint 5 as shown in the schematic diagram of the peeled surface of the welded portion shown in FIG. Further, as shown in FIG.
The aluminum alloy plate 1 locally expands along the concave portion 14 to form a gap 17 between the metal plates, and at the same time, forms a convex bulge 16 along the concave portion 14.

Here, the reason why the occurrence of scatter is suppressed is supposed as follows. That is, in the aluminum alloy plate 1 having a low melting point, the peripheral portion 15 of the concave portion 14 of the upper electrode 13 is formed.
, The contact area between the upper electrode 13 and the aluminum alloy plate 1 is increased, the welding current density is reduced, and the heat dissipation to the upper electrode 13 is increased, so that the temperature of the aluminum alloy plate 1 having a low melting point is reduced. Suppress the rise.

On the other hand, in the steel plate 2 having a high melting point, since the tip of the lower electrode 4 is dome-shaped, the contact area with the steel plate 2 is reduced, the welding current density is increased, and the heat radiation to the lower electrode 4 is reduced. The temperature of the high steel plate 2 is increased.
Therefore, it is presumed that the aluminum alloy plate 1 is less likely to be melted in a large amount, so that the occurrence of scatter is suppressed.

Furthermore, even if the scatter occurs, the upper electrode 13
Of the aluminum alloy plate 1 along the concave portion 14 of the metal plate 1 and is sealed in the gap 17 between the metal plates caused by the local expansion.

Accordingly, it is possible to prevent burrs from being formed around the interface joint portion 5 and to form burrs. Further, if the shape of the concave portion 14 on the surface of the upper electrode 13 is devised, it can be formed on the surface of the aluminum alloy plate 1. The shape of the bulge 16 can be formed well. As a result, the work of removing burrs after welding can be omitted, the productivity can be improved, and a high-quality weld can be obtained.

Here, using the same welding conditions as above,
As shown in FIG. 1 to NO. 3 and the shear strength is 5057N, 6399N,
5851N was obtained. On the other hand, A50
When the 52 aluminum alloy plates 1 are superimposed on each other and a pressure of 5880 N is applied as a proper welding condition and a DC current of 23000 A is applied for 0.25 seconds, the N of FIG.
O. 4 to NO. As shown in FIG.
107N, 3009N and 3048N. Therefore, with respect to the shear strength, a better result was obtained than when the same type of aluminum alloy plates were joined by welding.

As shown in FIG. 6, the peripheral portion 115 of the concave portion 114 of the upper electrode 113 may have a donut shape.
As shown in FIG. 7, the peripheral portion 2 of the concave portion 214 of the upper electrode 213
15 may be a track type. The lower electrode may have a flat tip or a truncated cone. In the above embodiment, the aluminum alloy plate 1 is used as a metal plate having a low melting point, and the steel plate 2 is used as a metal plate having a higher melting point.
Has been described, but any combination of metal plates may be used as long as the metal plates have different melting points. Further, as the plurality of metals having different melting points, an aluminum alloy material and a steel material are formed in a plate shape, but the present invention is not limited to this shape. Further, although two metal plates having different melting points are used, a plurality of metal plates may be used as long as there are bonding surfaces of metals having different melting points.

[0021]

According to the first aspect of the present invention, a plurality of metal bodies having different melting points are overlapped, sandwiched between a pair of electrodes composed of a first electrode and a second electrode, and joined by applying a pressure. In the spot welding method, the concave portion on the surface of the first electrode is brought into contact with the metal body having a low melting point, and a plurality of metal bodies having different melting points are sandwiched between the pair of electrodes, and are joined by applying pressure and conducting. In addition, there is an effect that formation of burrs due to scatter is prevented, and high productivity and high quality spot welding can be performed.

According to the second aspect, the first electrode is connected to the negative pole of the DC power supply, and the second electrode is connected to the positive pole of the DC power supply. .

According to the third aspect, in addition to the effects of the first or second aspect, the concave portion on the surface of the first electrode has a shape in which a gap is formed on the superimposed surface of the metal. There is an effect that even if scattering occurs, it can be sealed in the recess.

According to the fourth aspect, in addition to the effects of the first or second aspect, the concave portion on the surface of the first electrode is formed such that the surface of the expanded portion of the metal body having a low melting point is substantially the inner surface of the concave portion. Therefore, the shape of the protrusion formed on the surface of the metal body having a low melting point can be formed well.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the vicinity of a spot welding electrode according to an embodiment of the present invention.

FIG. 2 is a front view of an upper electrode of FIG. 1 and a cross-sectional view taken along line AA of FIG.

FIG. 3 is a cross-sectional view of the vicinity of a spot welding electrode after welding of FIG. 1;

FIG. 4 is a schematic view of a peeled surface of a weld after welding according to FIGS. 1 and 2;

FIG. 5 shows a result of the spot welding of FIG. 1 and a result of the spot welding of aluminum.

FIG. 6 is a front view of an upper electrode and a cross-sectional view taken along line AA of another embodiment of the present invention.

FIG. 7 is a front view of an upper electrode and a cross-sectional view taken along a line AA in another embodiment of the present invention.

FIG. 8 is a sectional view showing the vicinity of a conventional spot welding electrode.

9 is a front view and a side view of the upper electrode and the lower electrode shown in FIG.

10 is a cross-sectional view of the vicinity of the spot welding electrode after welding of FIG.

FIG. 11 is a schematic view of a peeled surface of a welded portion in FIG. 8;

FIG. 12 is a perspective view in which fins made of an aluminum alloy are welded and fixed to a base made of a steel plate.

[Explanation of symbols]

1 Aluminum alloy plate, 2 steel plate, 4 lower electrode (second
Electrodes), 6 DC power supply, 13, 113, 213 Upper electrode (first electrode), 14, 114, 214 recess.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kinya Ichikawa, Nastor Corporation 4, Kosai-cho, Kosai-cho, Koga-gun, Shiga Pref. Inventor Yoshiyuki Tokunaga 4 Kosuna-cho, Kosai-cho, Koga-gun, Shiga Prefecture

Claims (4)

[Claims] 1. A spot welding method in which a plurality of metal bodies having different melting points are overlapped, sandwiched between a pair of electrodes composed of a first electrode and a second electrode, and joined by applying an electric current under pressure. A spot welding method comprising: contacting a concave portion on the surface of one electrode with the metal body having a low melting point; sandwiching a plurality of metal bodies having different melting points between the pair of electrodes; . 2. The spot welding method according to claim 1, wherein the first electrode is connected to a negative pole of the DC power supply, and the second electrode is connected to a positive pole of the DC power supply. 3. The spot welding method according to claim 1, wherein the concave portion on the surface of the first electrode has a shape in which a gap is formed in a superimposed surface of the metal body. 4. The concave portion on the surface of the first electrode, wherein the surface of the expanded portion of the metal body having a low melting point has a shape substantially along the inner surface of the concave portion. 3. The spot welding method according to 2.