JPH06292978A - Resistance welding method for low electric resistant metallic members and (locally modified) low electric resistant metallic members for resistance welding - Google Patents

Abstract

PURPOSE:To prolong the service life of an anode electrode tip in performing spot welding on Al-base rolled sheets by using a DC power source. CONSTITUTION:A locally modified Al-base rolled sheet 5 provided with a high resistance area 4 formed by local melting and alloying processing using a high density energy source on the joining surfaces 3 of a weld zone 2 is used as the Al-base rolled sheet located at the cathode electrode tip 14 side. A modified Al-base rolled sheet 1 is used at the anode electrode tip 15 side. Consequently, since a fused part which is made into a nugget is prevented from being formed with inclination toward the anode electric tip 15 side, the service life of the anode electrode tip 15 can be prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for resistance welding a low electric resistance metal member of the same material type, and more particularly to a resistance welding method using a direct current type power source and a locally modified low electric resistance metal member for resistance welding. .

[0002]

2. Description of the Related Art Since an Al-based rolled plate, which is a metal member having a low electric resistance, has a low electric resistance, a large current is required when spot-welding the Al-based rolled plates. In order to avoid this, conventionally, the A
A method has been proposed in which a high resistance member having a higher electric resistance than that of the l-type rolled sheet is interposed to improve the heat generation efficiency of the welded portion and to reduce the current (for example, JP-A-63-278679). (See the official gazette).

[0003]

However, according to the conventional method, a high resistance member must be interposed between the welded portions of the Al-based rolled sheet immediately before the welding process, and the high resistance member is displaced. Since it is likely to occur, there is a point unfavorable for improving the efficiency of welding work.

Therefore, in order to prioritize the improvement of the efficiency of the welding work without using a high resistance member and at the cost of a little electric cost, a direct current type power source which is relatively small in spot welding and which can easily obtain a large current is used. Can be used.

However, when an excessive welding current is applied between the Al-based rolled plates by using a DC power source, a polar effect (Peltier effect, Thomson effect) such that the heat generation region is biased toward the anode electrode tip side appears remarkably. Moreover, since the heat radiation of the heat generation region is hindered by the oxide film having low thermal conductivity, the melted portion is formed deviated to the side of the anode electrode tip, and the life of the anode electrode tip, for example, the number of continuous dots is extremely reduced. Creates a new problem.

In view of the above, the present invention improves welding work efficiency by using a DC type power source and a low electrical resistance metal member having a specific structure, and in spite of using the DC type power source, the anode electrode An object of the present invention is to provide the resistance welding method capable of extending the life and reducing the current, and the locally modified low electric resistance metal member used in the method.

[0007]

The resistance welding method for a low electric resistance metal member according to the present invention is a method of resistance welding a low electric resistance metal member of the same material type using a direct current type power source. A locally modified low electrical resistance metal member is used as the low electrical resistance metal member arranged on the side, and the locally modified low electrical resistance metal member is provided on the joint surface of the welded portion thereof with a high density energy source. And a high resistance region having a higher electric resistance than the low electric resistance metal member arranged on the non-treated region and the anode electrode side. Characterize.

The locally modified low electrical resistance metal member for resistance welding according to the present invention is arranged on the cathode electrode side when the low electrical resistance metal member of the same material type is resistance welded using a DC power source. A locally modified low electrical resistance metal member, which is formed on a joint surface of a welded portion by a local melt alloying process using a high-density energy source, and is arranged on an untreated region and an anode electrode side. It has a high resistance region having a higher electric resistance than the low electric resistance metal member.

[0009]

In the resistance welding method, the locally modified low electrical resistance metal member is provided with the high resistance region integrally with the non-processed region, so that compared with the case where the high resistance member is interposed between both metal members. Improves welding work efficiency.

Further, since the high resistance region is arranged on one side of the cathode electrode side, when the resistance welding is carried out under the application of an excessive welding current by using the direct current type power source, the remarkable polarity effect appears. Along with this, the heat generation region moves to the anode electrode side, and a fusion zone is formed substantially in the middle of both welded portions. This extends the life of the anode electrode.

Further, since the heat generation efficiency of both welded parts is enhanced by the existence of the high resistance region, a low current can be achieved.

Further, since the high resistance region is formed by the local melt alloying treatment, even if the material to be treated is a thin plate, the material properties of the non-modified region are not damaged by the thermal influence.

According to the locally modified low electric resistance metal member, the welding method is easily carried out.

[0014]

Example As a low electric resistance metal member, an Al-Mg alloy (A5182-O material) having a thickness of 1.2 mm was used.
A system rolling plate was selected. The specific resistance (room temperature) of this Al-based rolled plate is 5.2 μΩcm.

In spot welding as resistance welding,
As the one plate to be welded, an Al-based rolled plate is used as it is. Therefore, this is called an unmodified Al-based rolled plate. As the other plate to be welded, a locally modified Al-based rolled plate (locally modified low electrical resistance metal member) obtained by subjecting the Al-based rolled plate to the following treatment is used.

That is, as shown in FIG. 1, an Al-based rolled plate 1
A locally molten alloying treatment using a high-density energy source is performed on one surface thereof, and a locally modified Al system having a high resistance region 4 on a joint surface 3 of a welded portion 2 as shown in FIG. The rolled plate 5 is obtained.

In the local molten alloying treatment, a carbon dioxide gas laser was used as a high-density energy source, and a powder injection method was applied as an alloy element supply method. In the processing, as shown in FIG. 1, the laser beam 6 is irradiated onto one surface of the Al-based rolled sheet 1 through an optical system 7 including a bender mirror, a condenser lens and a beam oscillator to form a molten pool 8. A metal powder 10 which is an alloying element is formed in the molten pool 8 from the injection nozzle 9.
With carrier gas 11. In this case, the laser beam 6 has a predetermined condensing diameter on one surface of the Al-based rolled plate 1, reciprocates with a predetermined amplitude in the direction orthogonal to the paper surface of FIG. 1, and also has a predetermined oscillation frequency in the direction of the arrow in FIG. Use to move in one direction. Similarly, the injection nozzle 9 also moves in one direction in the arrow direction.

An example of the processing conditions is as follows. For the laser beam 6, the laser output is 5 kW,
The light-collecting diameter on one surface of the Al-based rolled plate 1 is 2.3 mm, the amplitude is 12 mm, the oscillation frequency is 100 Hz, and the powder injection method is metal powder Cr powder (# 200), metal powder supply amount 15 g / min, carrier gas. Ar, carrier gas injection amount 10 liters /
min, and the processing speed is 1500 mm / min.

High resistance region 4 obtained by such a method
Contained about 3 atomic% Cr and had a depth of about 0.2 mm. The specific resistance of the high resistance region 4 is about 23 μΩ.
In cm, the resistivity increased to about 4 times the specific resistance of 5.2 μΩcm in the untreated region. This is due to the scattering of free electrons accompanying the alloying of Cr.

FIG. 3 shows the relationship between the Cr content and the specific resistance in the high resistance region 4, and it can be seen from FIG. 3 that the specific resistance increases as the Cr content increases.

In the spot welding operation, as shown in FIG. 4, the joint surface 3 of the welded portion 2 of the locally modified Al rolled plate 5 and the welded portion 12 of the unmodified Al rolled plate 1 are welded.
The plates 1 and 5 are superposed on each other with the joining surface 13 facing each other facing each other, and the plates 1 and 5 are placed so that the locally-modified Al-based rolled plate 5 is located on the cathode electrode chip (cathode electrode) 14 side. It was arranged between the electrode tip 14 and the anode electrode tip (anode electrode) 15. The positive and negative electrode tips 15 and 14 are JIS R type electrodes made of chrome copper and have a radius R of 80 mm and a diameter of 16 mm.

As shown in FIG. 5, the welded portions 12 and 2 of both plates 1 and 5 are pressed by the positive and negative electrode tips 15 and 14 with a pressing force of 430 kgf, and at the same time, the single-phase rectification type DC power source 7 is applied. 14k between positive and negative electrode tips 15 and 14
The welding current of A was applied under the condition of the energization time of 4 cycles to join between the welded parts 12 and 2. Then, this spot welding operation was repeated many times. This is an example.

For comparison, two sheets of unmodified Al similar to the above are used.
The system rolling plate 1 was repeatedly spot-welded under the conditions of a pressure of 430 kgf, a welding current of 18.5 kA by the single-phase rectification type DC power source 16 and an energization time of 4 cycles. This is a comparative example.

FIG. 6 is a photomicrograph (7 times) showing the metal structure of the welded portions 2 and 12 in the examples and comparative examples. In the figure, (a) corresponds to the example and (b) corresponds to the comparative example.

In FIG. 6, the distances a and b (see FIG. 5) from the bottom of the recess on the positive and negative electrode tip 15 and 14 sides of the weld to the nugget 8 were measured, and the results shown in Table 1 were obtained.

[0026]

[Table 1]

As is apparent from FIG. 6A and Table 1, in the case of the embodiment, the nugget 17 is formed substantially in the middle of the welded portions 2 and 12. This is a locally modified Al-based rolled plate 5
Since the high resistance region 4 is disposed on the side of the cathode electrode tip 14 side by side, when the resistance welding is performed under the application of an excessive welding current by using the single-phase rectification type DC power source 17, the polarity effect of This is due to the fact that the heat generation region moves to the anode electrode tip 15 side with the remarkable appearance, and the fusion zone is formed substantially in the middle of the welded portions 2 and 12. As a result, the life of the anode electrode tip 15 is extended.

In FIG. 6 (b) and Table 1, in the case of the comparative example, the nugget 8 is formed offset to the anode electrode chip 15 side. This is because the polar effect appears remarkably and the heat dissipation in the heat generation region is blocked by the oxide film.

FIG. 7 shows the number of continuous dots until the anode electrode tip 15 picks up in Examples and Comparative Examples. From FIG. 7, it can be seen that the number of continuous dots in the example is improved by about 1.8 times as compared with the comparative example. This is nothing but the prolongation of the life of the anode electrode tip 15 because the molten portion is formed substantially in the middle of the welded portions 2 and 12 as described above.

Generally, the welding strength is defined by the thickness of the plate to be welded, t.
Then, the diameter d of the nugget 17 must be d ≧ 5 × t ^1/2 . Therefore, in the case of the example, since the thickness t of the Al-based rolled plate is t = 1.2 mm, the lower limit of the welding strength guarantee of the diameter d of the nugget 17 is d =
It will be 5.4 mm.

Therefore, in the spot welding work,
Test with different welding current, welding current and nugget 1
When the relationship with the diameter d of 7 was obtained, the results shown in FIG. 8 were obtained. As is apparent from FIG. 8, in the example, the welding current required to form the nugget 17 having the diameter d = 5.4 mm is about 13.4 kA, but in the case of the comparative example, the welding current is about 13.4 kA.
Since it is 8.3 kA, it was found that the example can achieve a lower current of 4.9 kA as compared with the comparative example.
This is because the heat generation efficiency of the welded portions 2 and 12 is enhanced by the existence of the high resistance region 4.

As the alloy element in the high resistance region 4, Si powder, Mn powder or the like can be used in addition to Cr powder. FIG. 9 shows the relationship between the Si content and the specific resistance in the high resistance region 4, and FIG. 10 shows the high resistance region 4.
3 shows the relationship between the Mn content and the specific resistance. From FIGS. 9 and 10, it can be seen that the specific resistance increases as the Si content and the Mn content increase.

In spot welding, in order to improve the number of continuous spots of the positive and negative electrode tips, the oxide film of the Al-based welded plate is removed by pickling or the like. However, in the 1000 series and 6000 series Al-based welded plates, the specific resistance is small and resistance heat generation due to the oxide film cannot be obtained, so that the welding strength is reduced. The present invention can appropriately deal with such a problem.

The present invention is also applicable to resistance welding of Al plates and the like. Resistance welding also includes seam welding and the like.

[0035]

According to the method of resistance welding of a low electrical resistance metal member according to the present invention, by using the means specified above, the welding work efficiency is improved, and the life extension and reduction of the anode electrode are reduced. A current can be achieved.

According to the locally modified low electric resistance metal member according to the present invention, the welding method can be easily carried out.

[Brief description of drawings]

FIG. 1 is an explanatory view of a local melt alloying treatment.

FIG. 2 is a cross-sectional view of a locally modified Al-based rolled plate.

FIG. 3 is a graph showing the relationship between Cr content and specific resistance.

FIG. 4 is an explanatory diagram before starting spot welding.

FIG. 5 is an explanatory diagram at the end of spot welding.

FIG. 6 is a micrograph showing a metal structure of a welded portion in each example.

FIG. 7 is a graph showing the relationship between each example and the number of continuous dots of the anode electrode tip.

FIG. 8 is a graph showing the relationship between welding current and nugget diameter.

FIG. 9 is a graph showing the relationship between the Si content and the specific resistance.

FIG. 10 is a graph showing the relationship between Mn content and specific resistance.

[Explanation of symbols]

1 Al-based rolled plate (low electrical resistance metal member) 2 Welded part 3 Joining surface 4 High resistance region 5 Locally modified Al-based rolled plate (low electrical resistance metal member) 14 Cathode electrode tip (cathode electrode) 15 Anode electrode tip (anode electrode) 16 DC power supply

Claims (2)

[Claims] 1. When performing resistance welding of a low electrical resistance metal member of the same material type using a DC power source, a locally modified low electrical resistance is used as the low electrical resistance metal member disposed on the cathode electrode side. The locally modified low electrical resistance metal member is formed by a local melt alloying treatment using a high-density energy source on the joint surface of the welded portion, and a non-treated region and an anode are used. A resistance welding method for a low electric resistance metal member, comprising: a high resistance region having an electric resistance higher than that of the low electric resistance metal member arranged on the electrode side. 2. A locally modified low electric resistance metal member arranged on the cathode electrode side when resistance welding a low electric resistance metal member of the same material type by using a direct current type power source, which is a welded portion. On the joint surface of the high resistance material, which is formed by local melt alloying treatment using a high-density energy source and has a higher electric resistance than the low electric resistance metal member arranged on the non-treatment area and the anode electrode side. A locally modified low electrical resistance metal member for resistance welding, which is provided with a resistance region.