JPH0966371A - Electrode for welding aluminum alloy material and welding method - Google Patents

Abstract

(57) [Summary] [Purpose] An aluminum alloy that forms a good nugget and has excellent bonding strength, and that can greatly improve the number of continuous points compared to when using conventional chrome copper and has excellent welding efficiency. An electrode for welding a material and a welding method using the same are obtained. When two laminated aluminum alloy materials are joined to each other by resistance spot welding, a pair of electrodes formed of pure copper containing 99.9 wt% or more of copper is used to face each other. Two aluminum alloy materials are sandwiched in a pressurized state, and an electric current is applied between the two electrodes, whereby the two aluminum alloy materials are melted by resistance heating and bonded to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode used for resistance spot welding of various aluminum alloy materials such as aluminum alloy plates and shapes, and a method for welding aluminum alloy materials using the electrode. is there.

[0002]

2. Description of the Related Art As is well known, when joining thin iron-based plates such as mild steel and galvanized steel plates used for outer plates of various automobiles, as shown in FIG.
A pair of welding electrodes 2 arranged to face each other with a pair of steel plates 1 and 1;
The two steel plates 1, 1 are sandwiched between the two steel plates 1, 1 by applying a large electric current between the electrodes 2, 2 while water-cooling the electrodes 2, 2 in the cooling unit 3.
Resistance spot welding is used to melt and heat the relevant parts by resistance heating. At this time, the steel plate 1
Generally has a high Vickers hardness (Hv) of about 150 to 250. Therefore, in order to prevent the electrode 2 side from being deformed at the time of pressurization, chromium (Cr) is set to 0.4.
A material using chromium copper having a hardness increased by adding about wt% (Hv = 167) is adopted.

On the other hand, in the various automobiles mentioned above, due to the recent demand for energy saving such as improvement in fuel consumption and material recyclability, a lightweight aluminum alloy is used as a vehicle body constituent member such as an outer plate in place of the above-mentioned iron-based member. The proportion of molded components used is increasing. By the way, when such aluminum alloy materials are joined by resistance spot welding, the aluminum alloy has a specific resistance as low as about 1/3 as compared with mild steel and has a good thermal conductivity, so that it is locally applied. In order to form a good nugget by resistance heating and melting to form a good nugget, it is necessary to flow a large current that is about twice as large as that of mild steel in a short time. In addition, aluminum alloy has a high-resistance oxide film on its surface, and blowholes and cracks are likely to occur during solidification of the nugget. It needs to be doubled. Therefore, conventionally, when resistance spot welding the above aluminum alloy material, an electrode of chromium copper having excellent hardness similar to that of the iron-based material is used exclusively from the request for strength, and pure copper is generally used. In that case, it was thought that the tip was easily deformed and was not practical (for example, "Various joining methods of aluminum and recent progress", Japan Light Metal Welding Structure Association,
Published November 27, 1991, p. 103).

[0004]

However, in the case of resistance spot welding the above aluminum alloy material with an electrode using chromium copper, the condition is that a current of about twice the value required in the case of the iron system is applied. Also, the heat generated at the interface between the electrode and the aluminum alloy material becomes large, and aluminum and copper tend to be alloyed easily. Electrode contamination (pickup) occurs due to the alloying, the apparent electrode tip diameter increases, the contact between the electrode and the aluminum alloy material is uneven, and the planar shape of the nugget largely deviates from a perfect circle, resulting in an irregular shape. Therefore, the tensile shear strength and the nugget diameter become smaller than the standard when the continuous hitting points reach about 300 points. Therefore, there is a problem that the work efficiency is extremely poor because the electrode needs to be dressed or replaced each time.

Therefore, the inventors of the present invention are made of various materials including pure copper containing 99.9 wt% or more of copper, which has been considered not practical so far, in addition to the electrode made of chromium copper. As a result of earnestly carrying out an experiment of spot welding an aluminum alloy material at a continuous spot using an electrode, the electrode using the pure copper can sufficiently withstand a pressure force about twice that of an iron-based electrode. In addition to being able to do, it is suitable for forming a good nugget by uniformly flowing a large current in a short time because it has a higher conductivity than that of a chromium copper electrode, etc., so that a high bonding strength can be obtained. There was found. Moreover, in the case of an electrode made of pure copper, since the electric resistance is small, the heat generation in the electrode portion is small, and the thermal conductivity increases corresponding to the conductivity, so that the cooling efficiency of the electrode is improved and the electrode is improved. It is possible to quickly guide the harmful heat generated at the interface between the aluminum alloy material and the aluminum alloy material to the cooling part side of the electrode and smoothly release it. As a result, the local temperature rise at the interface is reduced and the occurrence of pickup is suppressed. Is
On the contrary, it has a much longer service life than electrodes made of other materials and is softer than electrodes made of chromium copper, etc. It has been found that the sharpness of the shape is reduced and the appearance is excellent. On this occasion,
Particularly in connection with the latter shape, the electrode softens near the contact circle around the electrode-aluminum material where current is likely to concentrate,
It was also a noteworthy finding that the entire electrode can naturally maintain the convex shape in combination with the vicinity of the center of the contact circle where the softening is delayed.

The present invention has been made on the basis of such findings. It forms a good nugget and is excellent in bonding strength, and the number of continuous dots is greatly improved as compared with the case of using conventional chromium copper. It is an object of the present invention to provide an electrode for welding an aluminum alloy material which is capable of achieving excellent welding efficiency, and a welding method using the electrode.

[0007]

The electrode for welding an aluminum alloy material according to the present invention according to claim 1 is an electrode used for resistance spot welding between aluminum alloy materials, and copper is 99 as an electrode material. This is characterized by using pure copper containing at least 9 wt%.

In the method for welding aluminum alloy materials according to the present invention as defined in claim 2, when the laminated aluminum alloy materials are joined to each other by resistance spot welding, a pair of 99.9 wt% or more arranged opposite to each other is used. By sandwiching the aluminum alloy material in a pressurized state by electrodes formed of pure copper including copper, and applying a current between both electrodes, the laminated aluminum alloy materials are fused by resistance heating and bonded to each other. It is characterized by.

According to a third aspect of the present invention, the hardness of the electrode according to the second aspect is greater than the hardness of the aluminum alloy material, and the difference in Vickers hardness between the electrode and the aluminum alloy material. Is less than or equal to 50, and
The electrical conductivity of the electrode is 95% IACS or more, and the difference from the electrical conductivity of the aluminum alloy material is 45% IACS or more. Claim 4
The invention according to claim 2, wherein the hardness of the electrode according to claim 2 is
The hardness is higher than the hardness of the aluminum alloy material, the difference in Vickers hardness between the electrode and the aluminum alloy material is 30 or less, and the conductivity of the electrode is 95%.
It is characterized in that it is IACS or more and the difference from the conductivity of the aluminum alloy material is 60% IACS or more.

According to a fifth aspect of the invention, in the invention according to the third aspect, the aluminum alloy material is 0.4 to 1.5 wt% of magnesium and 0.
The invention according to claim 6 is the aluminum alloy material according to claim 4, wherein the aluminum alloy material contains 2 to 6 wt% of magnesium. It is characterized by comprising an aluminum alloy containing.

[0011]

In the invention of claim 1 and the invention of claim 2 using the same, copper is used as the electrode material.
Since pure copper containing 9.9 wt% or more is used, the conductivity is higher than that of the conventionally used chromium copper electrode, so that a large current can be uniformly flowed in a short time to form a good nugget. Can be achieved, resulting in high bond strength. Moreover, according to the welding electrode of the present invention, since the thermal conductivity also increases corresponding to the above-mentioned electrical conductivity,
The cooling efficiency of the electrode is improved, and the harmful heat generated at the interface between the electrode and the aluminum alloy material can be quickly guided to the cooling part side of the electrode and smoothly released, so that the local temperature rise at the interface can be prevented. Since it is reduced and the occurrence of pickup can be suppressed, the service life is greatly extended as compared with the case of using the conventional chromium copper electrode, and it is a softer electrode compared to the chromium copper electrode. for,
By applying pressure to the electrodes, the traces formed on the aluminum alloy material are reduced and the appearance is excellent.

At this time, as in the invention according to claim 3 or 4, as the electrode made of the pure copper, the hardness of the electrode is larger than the hardness of the aluminum alloy material, and the electrode and the aluminum alloy material are If the difference in Vickers hardness between and is 50 or less, preferably 30 or less is used, it is possible to further suppress the trace of the electrode on the aluminum alloy material side due to the large pressure force during welding, and A good appearance is obtained, and the conductivity of the electrode is 95% IACS or more, and the difference from the conductivity of the aluminum alloy material is 45% IACS or more, preferably 6
If 0% IACS or more is used, the harmful heat generated at the interface between the electrode and the plate material can be quickly and reliably guided to the cooling part side of the electrode without being transmitted to the aluminum alloy material side. preferable.

Therefore, in particular, the invention described in claim 3 is the same as the invention described in claim 5, in which magnesium is added to
4-1.5 wt% and silicon 0.2-1.5 wt%
It is suitable for use in welding an aluminum alloy material consisting of an aluminum alloy containing 100% of aluminum, and in particular, the invention according to claim 4 has increased use as an outer panel for automobiles like the invention according to claim 6. 2 to 6 magnesium
It is suitable when used for welding an aluminum alloy material containing wt%.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the drawings. First, as an example of the aluminum alloy welding electrode of the present invention, a pure copper electrode using tough pitch copper having the components shown in FIG. 1 was prepared. Further, as comparative examples, an electrode made of chromium copper having the same components as shown in FIG. 1 and conventionally used (hereinafter abbreviated as chromium copper electrode), and an electrode made of copper added with silver to increase conductivity (the same). , A silver-added copper electrode) and an electrode made of alumina-dispersed copper for preventing the diffusion of the picked-up aluminum and copper (the same as the alumina-copper electrode). By the way, these four types of electrodes are all R type (tip 1
00R), and the respective conductivity and Vickers hardness are as shown in FIG. Then, using these four types of electrodes, a resistance spot welding test was conducted by continuously striking an aluminum alloy plate. Here, the aluminum alloy plate used in the above welding test contains 4.5% magnesium.
JIS equivalent 5182 alloy containing, and AA6009 containing 0.6% magnesium and 0.8% silicon
It is an alloy having considerable so-called bake hardness, and its mechanical properties and various properties are as shown in the upper and lower rows of FIG. These aluminum alloy plates had a plate thickness of 1 mm and were not surface-treated. The above J
The difference in Vickers hardness between the alloy plate corresponding to IS 5182 and the pure copper electrode according to the present invention is 15.4, and the difference in conductivity is 64.8. Further, the difference in Vickers hardness between the alloy plate corresponding to AA6009 and the pure copper electrode according to the present invention is 2
7.3 and the difference in conductivity is 57.3.

Prior to the welding test by continuous welding point, the aluminum alloy plate is first welded by gradually increasing the electric current, and the nugget diameter and the joint strength at each electric current are measured (so-called weld rob test) to determine the strength defined by JISZ3140. After obtaining a current value satisfying the above condition, this was multiplied by a predetermined coefficient to determine the optimum current value used for the test. The welding conditions used in the welding test with the continuous welding point are as follows. Welding equipment: Stationary single-phase AC resistance spot welding machine Pressure: 300 kgf Energizing time: 11 cy / 50 Hz (internal upslope 3c
y) Welding current: 30 kA (4 cy) Post-heat current: 4 cy / 50 Hz Hold: 30 cy / 50 Hz Squeeze and RBI speed: 1 point / 2 seconds

Next, a welding test using the above-mentioned continuous welding points was conducted, and at that time, the mechanical strength (JI
The tensile shear strength specified in SZ3136) is measured,
A cross-section observation photograph of the welded portion (nugget) was taken, the tip diameter was measured to confirm the worn state of each electrode, and the tip shape was observed. And finally 10
The tip of each electrode after the 00 spot welding was taken in close-up and observed. First, FIGS. 4 to 7 show the mechanical strength of the welded portion at each welding point in the welding test using the above-mentioned JIS 5182 alloy plate, and FIG. 4 shows the silver-added copper electrode and FIG. Is a table showing the results of a welding test on an alumina copper electrode, FIG. 6 is a table showing the results of a welding test on the pure copper electrode according to the present invention. In addition, FIG.
And FIG. 10 shows the mechanical strength of the welded portion at each welding point in a welding test using an alloy plate equivalent to AA6009 containing 0.6% of magnesium and 0.8% of silicon. Chromium copper electrode, FIG. 10 is a table showing the results of the welding test on the pure copper electrode according to the present invention.

From these tables, according to the electrode using pure copper according to the present invention, in the welding test using the alloy plate corresponding to JIS 5182, the tensile shear strength is lowered even at the time of welding at 1000 spots. Or, there was no occurrence of variation, and the fracture mode was also good due to the plug fracture. As a result, it was confirmed that at least at the above-mentioned 1000 spots, the continuous spotability was improved about 5 times that of the alumina copper electrode and about 3 times that of the conventional chromium copper electrode. By the way, although it has been shown up to 1000 dots in FIG. 7, it has been confirmed that the above-mentioned pure copper electrode can have 1500 continuous dots as compared with FIG. 7, which is about 1. This means that it has a continuous dot performance of 5 times or more. Also, in a welding test using an alloy plate corresponding to AA6009, it was confirmed that when the pure copper electrode according to the present invention was used, the continuous spotting property was improved about three times that of the chromium copper electrode.

Next, FIG. 8 shows the measurement results of the tip diameter of each of the above-mentioned electrodes. From the figure, it can be seen that the pure copper electrode is much less worn than the other electrodes. understood. Here, as shown in FIG. 4, the silver-added copper electrode has a relatively large number of continuous dots,
The reason why the electrode tip diameter is increased is considered to be that the diffusion of the aluminum alloy plate and the electrode is promoted by the influence of silver added to improve the strength without impairing the conductivity. Next, according to the observation result of the tip shape of each electrode, as shown in FIG. 11, at the initial stage of welding, the tip portion 10 of each of the electrodes had an R shape. In the chromium copper electrode and the alumina copper electrode, which are poor in weldability, as shown in FIG.
1 gradually wears from the center of the electrode tip, while on the other hand, in the silver-added copper electrode and the pure copper electrode according to the present invention, as shown in FIG. It was worn from the ground and eventually became flat as a whole.

Therefore, when the wear pattern of the electrode is compared with a cross-section observation photograph of the corresponding nugget, in the silver-added copper electrode and the pure copper electrode, as shown in FIG. Also, while the nugget diameter was constant, in the chromium copper electrode and the alumina copper electrode, as shown in FIG. 12, the nugget 14 was separated into two as the number of hit points increased, and There were variations. It can be seen that such changes over time in the wear pattern and the nugget shape of the electrode tip portion are consistent with the results of the change in tensile shear strength in the welding test by continuous welding points shown in FIGS. 4 to 7. In addition, at the end, each electrode tip portion after 1000-dot welding was observed in close-up, but the pure copper electrode according to the present invention had very few pickups, whereas the alumina copper electrode had the largest amount of aluminum deposition, Next, the chromium copper electrode and the silver-added copper electrode were in this order.

Therefore, as shown in FIGS. 4 to 7 and FIGS. 9 and 10, the reason why the pure copper electrode according to the present invention is much superior to the other electrodes in continuous dot forming property is the above pure copper. Since the conductivity of the electrode is higher than that of other electrodes, the amount of heat generated by the electrode itself is small, and the hardness of the pure copper electrode is higher than that of the aluminum alloy, and the difference between them is small. It can be understood that the deformation to the regular shape was small as a result, and therefore the wear pattern of the electrode tip was better than that of the other electrodes, and the pickup amount was extremely small. Therefore, according to the pure copper electrode,
Aluminum alloy plate equivalent to A6009 or JIS5182
It is possible to obtain excellent continuous spotting property in the welding of a considerable aluminum alloy plate.

In the above embodiments, only the example of using tough pitch copper as the pure copper electrode according to the present invention has been described, but the present invention is not limited to this, and 99.9% of copper is used.
As long as the pure copper contains the above, the same function and effect can be obtained by using other pure copper such as oxygen-free copper or phosphorus deoxidized copper.

[0022]

As described above, in the invention described in claim 1 and the invention described in claim 2 using the same, pure copper containing 99.9 wt% or more of copper is used as the electrode material. Therefore, since the conductivity is higher than that of the conventionally used chromium copper electrode, it is possible to uniformly flow a large current in a short time to form a good nugget,
As a result, a high bonding strength is obtained, and since the thermal conductivity also increases corresponding to the above-mentioned electrical conductivity, the cooling efficiency of the electrode is improved and harmful heat generated at the interface between the electrode and the aluminum alloy material is eliminated. The conventional chrome copper electrode was used because it can be quickly guided to the cooling part side of the electrode and released smoothly, thus suppressing the local temperature rise at the interface and suppressing the occurrence of pickup. It has a significantly longer service life than before, and because it is a softer electrode than a chrome-copper electrode, the traces formed on the aluminum alloy material by pressing the electrode become smaller, resulting in excellent welding. You can get the appearance.

Further, according to the invention of claim 3 or 4, as the electrode made of the pure copper, the hardness of the electrode is higher than that of the aluminum alloy material, and the electrode and the aluminum alloy material are If a Vickers hardness difference of 50 or less, preferably 30 or less is used, it is possible to further prevent the trace of the electrode from being left on the aluminum alloy material side due to a large pressure applied during welding. A visual appearance is obtained, and in addition, the conductivity of the electrode is 95% IACS or more, and the difference from the conductivity of the aluminum alloy material is 45% IACS or more, preferably 60.
If it is more than% IACS, the harmful heat generated at the interface between the electrode and the aluminum alloy material can be surely and quickly guided to the cooling part side of the electrode without being transmitted to the aluminum alloy material side. , And more preferable.

Therefore, in particular, like the invention according to claim 5 or 6, the invention according to claim 3 contains 0.4 to 1.5 wt% of magnesium and 0.2 to 1.5 wt% of silicon. It is suitable when used for welding an aluminum alloy material made of an aluminum alloy, and also,
The invention described in (1) has a particularly excellent effect when it is used for welding a plate material of an aluminum alloy containing 2 to 6 wt% of magnesium, which is increasingly used as an outer plate for automobiles.

[Brief description of drawings]

FIG. 1 is a table showing components of a pure copper electrode according to the present invention and an electrode of a comparative example.

2 is a table showing the conductivity and hardness of each electrode of FIG.

FIG. 3 is a table showing various characteristics of the aluminum alloy material used in the welding test with each electrode of FIG.

FIG. 4 is a graph showing a change in joint strength during a continuous spot welding test of a JIS5182 equivalent alloy plate using the silver-added copper electrode of FIG. 1.

5 is a graph showing a change in joint strength during a continuous spot welding test of a JIS5182 equivalent alloy plate using the alumina copper electrode of FIG.

FIG. 6 is a graph showing a change in joint strength during continuous spot welding test of a JIS5182 equivalent alloy plate using the chromium copper electrode of FIG. 1.

FIG. 7: JIS51 with pure copper electrode according to the present invention in FIG.
It is a graph which shows the change of the joining part strength at the time of the continuous spot welding test of the 82 equivalent alloy plate.

FIG. 8 is a graph showing the measurement results of the electrode tip diameter with the increase in the number of spots when the JIS 5182 equivalent alloy plate was subjected to the continuous spot welding test with each electrode of FIG.

9 is a graph showing changes in the strength of the joint portion during the continuous spot welding test of the AA6009 equivalent alloy plate using the chromium copper electrode of FIG.

10 is an AA60 with a pure copper electrode according to the present invention in FIG.
It is a graph which shows the change of the joint strength at the time of the continuous spot welding test of the 09 equivalent alloy plate.

FIG. 11 is a side view showing the tip shape and nugget shape of each electrode at the initial stage of the continuous spot welding test.

FIG. 12 is a side view showing the wear shape and nugget shape of the tips of the chromium copper electrode and the alumina copper electrode as the number of hit points increases.

FIG. 13 is a side view showing the wear shape and nugget shape of the tip portions of the pure copper electrode and the silver-added copper electrode as the number of hit points increases.

FIG. 14 is a vertical cross-sectional view showing a state of general resistance spot welding.

[Explanation of symbols]

 10, 11, 12 Tip of electrode 13, 14 Welded part (nugget)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasunori Hyogo 2-3-3 Shiba, Minato-ku, Tokyo Mitsubishi Aluminum Co., Ltd. (72) Inventor Makoto Kabazawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Tube Co., Ltd. (72) Inventor Yoshimasa Funakawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Tube Co., Ltd.

Claims (6)

[Claims] 1. An electrode used for resistance spot welding between aluminum alloy materials, wherein copper is used as an electrode material.
An electrode for welding an aluminum alloy material, which uses pure copper containing 9.9 wt% or more. 2. A welding method for joining laminated aluminum alloy materials to each other by resistance spot welding, comprising:
The aluminum alloy material is sandwiched in a pressurized state by a pair of electrodes formed of pure copper containing 99.9 wt% or more of copper, which are arranged opposite to each other. A method for welding an aluminum alloy material, which comprises melting the alloy materials by resistance heating and joining them together. 3. The hardness of the electrode is greater than the hardness of the aluminum alloy material, the difference in Vickers hardness between the electrode and the aluminum alloy material is 50 or less, and the conductivity of the electrode is 95%. IACS or more, and the difference from the conductivity of the aluminum alloy material is 45% IA
It is CS or more, The welding method of the aluminum alloy material of Claim 2 characterized by the above-mentioned. 4. The hardness of the electrode is greater than the hardness of the aluminum alloy material, the difference in Vickers hardness between the electrode and the aluminum alloy material is 30 or less, and the conductivity of the electrode is 95%. IA above IACS, and the difference from the conductivity of the aluminum alloy material is 60% IA
It is CS or more, The welding method of the aluminum alloy material of Claim 2 characterized by the above-mentioned. 5. The aluminum alloy according to claim 3, wherein the aluminum alloy material is an aluminum alloy containing 0.4 to 1.5 wt% magnesium and 0.2 to 1.5 wt% silicon. Welding method of material. 6. The method for welding an aluminum alloy material according to claim 4, wherein the aluminum alloy material is made of an aluminum alloy containing 2 to 6 wt% of magnesium.