JPH0966370A - Electrode for resistance spot welding to aluminum material to be welded and resistance spot welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain continuous spot weldability and appearance quality in a welded part which is equivalent to a steal sheet by permitting to keep a contacting end-diameter of the electrode constant and permitting to keep a current density constant during welding, in the continuous spots at the time of a resistance spot welding to Al alloy. SOLUTION: In the range of a temp. near the end part of the electrode during passing a welding current, a high temp. hardness characteristic fitting into a softening characteristic of Al alloy material to be welded i.e., a soften characteristic within a specified temp. zone is provided to the electrode 1. Specifically, with respect to the electrode 1 used in the resistance spot welding to the Al alloy material to be welded, the electrode is composed of the material having the high temp. hardness characteristic which is softened from >=Hv80 to <=Hv30 in the Vickers hardness at 200 deg.C-400 deg.C so as to be >=971ACS% in the electric conductivity of the electrode, >=Hv80 at <=200 deg.C and <=Hv30 at >=400 deg.C in the Vickers hardness. The resistance spot welding is performed by using this electrode for the resistance spot welding to the Al material to be welded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for resistance spot welding of an aluminum-based material to be welded and a resistance spot welding method, and more particularly, to a continuous spotting property (electrode life) when welding a spot of an aluminum-based material to be welded. It is related to the technology to improve.

[0002]

2. Description of the Related Art The following are conventional resistance spot welding electrodes and resistance spot welding methods for aluminum-based materials to be welded.

Conventional Example 1: As an electrode for resistance spot welding of an aluminum-based material to be welded, RWMA class 2 such as chrome copper (Cu-Cr) which is practically the same as a steel plate is practically used.
Electrodes are used.

Conventional Example 2: A composite structure electrode having a two-layer structure having a core portion and an outer peripheral portion of the electrode is used, and electric conductivity, Vickers hardness, melting point, etc. are different between the core portion and the outer peripheral portion. Such techniques are disclosed in, for example, Japanese Patent Laid-Open Nos. 4-356377 and 5-318140.

Conventional Example 3: As an electrode made of a single material, for example, as in Japanese Patent Laid-Open No. 6-210461, a highly conductive material having an electric conductivity of 92 IACS% or more is used, and the Vickers hardness is specified. The range of technologies has been published.

[0006]

However, the conventional resistance spot welding electrodes and resistance spot welding methods for aluminum-based materials to be welded have the following problems to be solved.

Conventional Example 1: RWM such as chromium copper of Conventional Example 1
The A class 2 electrode is a material that has been used for many years for spot welding of steel sheets, and since it has an additive element added to copper in order to increase the softening temperature of the material, its electrical conductivity is It becomes low, about 75 to 85 IACS%. Therefore, heat is generated between the electrode tip and the material to be welded during energization, and an alloy layer of aluminum and copper is easily generated at the electrode tip. Then, the alloy layer at the electrode tip generated in this way is brought to the material to be welded side by side in the next welding, and by repeating this, a dish-shaped recess is generated at the electrode tip, which causes a deterioration form called pickup deterioration. This is shown (see FIG. 2C). ). In this way, when the tip of the electrode deteriorates and the contact diameter expands, the appearance quality of the welded portion deteriorates, and the current density decreases, leading to the life of the electrode.

For the above reason, the continuous spotting property of a general RWMA class 2 electrode in resistance spot welding of aluminum-based materials to be welded is remarkably lower than that of resistance spot welding of steel sheet, and is 1/10 to 1/10 of that of steel sheet. It will be about / 20. Therefore, it is necessary to perform frequent electrode dressing to constantly shape the electrode tip, and to remove deposits to keep the current density constant, resulting in extremely low productivity of welding aluminum alloy parts. There was a point. Therefore, there is a problem to solve such a problem.

Conventional Example 2: In the composite structure electrode as shown in Conventional Example 2, the material used for the core is generally high in hardness and the electric conductivity is the same as that of the conventional RWMA class 2 electrode. For this reason, as in the case of the chromium copper of Conventional Example 1, it is easy to generate an alloy layer of aluminum and copper due to heat generation at the electrode tip. Therefore, as in Conventional Example 1, pickup deterioration occurs, and continuous dot performance is greatly improved. Although it cannot be expected, there is a problem that the cost of the electrode increases because of the composite structure. Therefore, there is a problem to solve such a problem.

Conventional Example 3: When an electrode material having a relatively high electric conductivity as shown in Conventional Example 3 is used, aluminum and copper as shown in Conventional Example 1 and Conventional Example 2 are used. Since it is difficult to form the alloy layer, the continuous spotting property in resistance spot welding of the aluminum-based material to be welded is slightly improved. However, as a result of confirming the performance by the continuous dot test,
Although a slight effect was observed, the softening temperature at high temperature was raised, that is, the softening temperature was about 400 ° C, so the material characteristics were set so that the contact diameter of the electrode tip should not spread with the number of dots. However, there was a problem in that the current density eventually decreased, and it was not possible to achieve continuous spotting performance comparable to that of steel sheets. Therefore, there is a problem to solve such a problem.

[0011]

SUMMARY OF THE INVENTION The present invention has been conceived in view of the above-mentioned conventional problems, and in an electrode for resistance spot welding of an aluminum-based material to be welded and a resistance spot welding method, the electric conductivity of the electrode material is By optimizing the hardness characteristics for the material to be welded at high temperature and by making the shape of the electrode tip a specific shape, the contact diameter of the electrode tip is kept constant at continuous welding points, that is, the current density during welding is By forming and maintaining the protrusions to keep it constant, it is possible to obtain continuous spotting properties similar to steel plates and good appearance quality of the welded part, and the conventional electrode life is maintained when resistance spot welding aluminum-based materials to be welded. It is intended to solve the problem that the appearance quality of the welded portion is short and also deteriorates.

[0012]

An electrode for resistance spot welding of an aluminum-based material to be welded according to the present invention has a resistance spot welding electrode of an aluminum alloy, which is a material to be welded, to the electrode in a temperature range near the tip of the electrode during welding. It is characterized by having a high temperature hardness characteristic matched to the softening characteristic, that is, having a softening characteristic in a specific temperature range.
More specifically, as described in claim 1, in an electrode used for resistance spot welding of an aluminum-based material to be welded, the electric conductivity of the electrode is 97 IACS% or more,
And, at 200 ° C or lower, Vickers hardness Hv80 or higher,
The Vickers hardness is Hv30 or less at 400 ° C or higher, and the Vickers hardness is H between 200 ° C and 400 ° C.
It is characterized by using a material having a high temperature hardness characteristic that softens from v80 or more to Hv30 or less.

In this case, IACS used in the unit of electrical conductivity is International A
It is an abbreviation for "nnealed Copper Standard", and IACS% is a percentage (%) of electric conductivity with respect to a standard annealed Cu material.

In an embodiment of the electrode for resistance spot welding of an aluminum-based material to be welded according to the present invention, as described in claim 2, the shape of the electrode tip has a curvature of R8 mm to R40 mm at the electrode tip. When it is R-shaped with a radius and the thickness of the thin plate side of the material to be welded is tmm, the R-shaped part is at least 6√ in diameter.
When the thickness of the electrode tip is tmm or more, or when the shape of the electrode tip is the thickness of the thin plate side of the material to be welded is tmm, the diameter of the electrode tip is 4√t.
It has a flat part of mm to 6√tmm, and the outer peripheral part thereof has an R shape with a radius of curvature of R8 mm to R40 mm, or the electrode tip has a shape as described in claim 4. R with a radius of curvature of R8mm to R40mm at the tip
The thickness of the material to be welded on the thin plate side is tmm
And the diameter of the R-shaped tip is 4√tmm
A shape composed of at least two or more compound spherical surfaces or compound curved surfaces having another radius of curvature larger than the radius of curvature of the electrode only in the range of up to 6√tmm; As described in Item 5, the shape of the electrode tip is tm when the thickness of the thin plate of the material to be welded is tm.
When m, the diameter of the electrode tip is 4√tmm to 6√tm
It has a flat part of m, and its outer peripheral part has a substantially taper shape having an angle of 5 ° to 30 ° with respect to an axis orthogonal to the axis of the electrode. like,
When the shape of the electrode tip is tmm, and the thickness of the thin plate side of the material to be welded is tmm, the electrode tip has a spherical portion having an appropriate radius of curvature only in the range of diameter 4√tmm to 6√tmm, and , Its outer periphery is 5 ° to 3 with respect to the axis orthogonal to the axis of the electrode.
For example, it may have a substantially tapered shape with an angle of 0 °.

Also, in the embodiment of the electrode for resistance spot welding of the aluminum-based material to be welded according to the present invention, as described in claim 7, the shape of the electrode tip is the thin plate side of the material to be welded. When the plate thickness is tmm,
Diameter 4√tmm ~ 6√tmm at electrode tip, height 0.1
A protrusion having a size of tmm to 0.3 tmm may be provided, and a flat portion of at least 1 mm or more may be formed on the outer peripheral portion of the protrusion from the outer wall of the protrusion, and in this case, As described in claim 8, a corner portion or an outer wall portion of the protrusion and a flat portion are connected by a curved surface having an appropriate radius of curvature, or as described in claim 9, The tip shape of the projection is flat, or as described in claim 10,
The tip shape of the protrusion may be a spherical surface having an appropriate radius of curvature.

According to the resistance spot welding method for an aluminum-based material to be welded according to the present invention, when the aluminum-based material to be welded is resistance spot-welded, the electrical conductivity of the electrode is reduced. 97IACS%
Above, and the electrode and the welded material such that the hardness difference between the electrode and the material to be welded is Hv20 or more at 200 ° C. or less and Hv15 or less at a temperature range of 250 ° C. to 400 ° C. in Vickers hardness. The feature is that welding is performed using the material.

In an embodiment of the resistance spot welding electrode and the resistance spot welding method for an aluminum-based material to be welded according to the present invention, as described in claim 12, the material of the electrode is tough pitch copper. Alternatively, as described in claim 13, the material of the electrode may be oxygen-free copper.

[0018]

The electrode for resistance spot welding of the aluminum-based material to be welded according to the present invention has the following features. Conductivity is 97IA
Vickers hardness Hv80 or more at CS% or more and 200 ° C. or less, Vickers hardness Hv3 at 400 ° C. or more
Since the Vickers hardness is softened from Hv80 or more to Hv30 or less between 200 ° C. and 400 ° C. so as to be 0 or less, the electrical conductivity of the electrode material, The hardness characteristics for the material to be welded at high temperature will be optimized for resistance spot welding of the aluminum-based material to be welded, that is, for the electrode, the high-temperature hardness characteristics that match the softening characteristics of the aluminum alloy that is the material to be welded, that is, , Since it has softening characteristics in a specific temperature range, by making the shape of the electrode tip a specific shape, the contact diameter of the electrode tip is kept constant at the continuous spot of resistance spot welding of the aluminum-based material to be welded. That is, the current density during welding is kept constant, and the continuous spotting property and the welded area are similar to those of steel sheets. Become that watching quality is obtained,
In the resistance spot welding of the aluminum-based material to be welded, the problem that the electrode life is short and the appearance quality of the welded portion is deteriorated is solved.

In the embodiment of the electrode for resistance spot welding of the aluminum-based material to be welded according to the present invention, as described in claim 2, the shape of the electrode tip has a curvature of R8 mm to R40 mm at the electrode tip. When it is R-shaped with a radius and the thickness of the thin plate side of the material to be welded is tmm, the R-shaped part is at least 6√ in diameter.
By ensuring tmm or more, the protrusions can be easily formed at the electrode tip, and the protrusions can be maintained well even if the number of dots is advanced, so that the number of dots disappeared by the protrusion is significantly increased. It becomes an electrode for resistance spot welding of aluminum-based materials to be welded, which has excellent continuous spot performance.

Further, as described in claim 3, when the shape of the electrode tip is the thickness of the thin plate side of the material to be welded is tmm, the electrode tip has a flat surface with a diameter of 4√tmm to 6√tmm. And the outer periphery has a radius of curvature of R8 mm-
By adopting the R shape of R40 mm, the protrusions can be easily self-formed at the tip of the electrode, and the protrusions can be maintained well even if the spotting progresses. The number of points is greatly increased, and it becomes an electrode for resistance spot welding of aluminum-based materials to be welded, which has excellent continuous spotting performance.

Alternatively, as described in claim 4, the shape of the electrode tip is R8 mm to R40 mm at the electrode tip.
R-shape having a radius of curvature of, and the thickness of the thin plate side of the material to be welded is tmm, the diameter of the tip of the R-shape is only in the range of 4√tmm to 6√tmm, The number of projection vanishing spots is also significantly increased by having a shape composed of at least two or more compound spherical surfaces or compound curved surfaces having a different radius of curvature larger than the radius of curvature of the electrode. It becomes an electrode for resistance spot welding of an aluminum-based material to be welded, which has increased in number and has excellent continuous spot performance.

Alternatively, as described in claim 5, the shape of the electrode tip is the thickness tm of the material to be welded on the thin plate side.
When m, the diameter of the electrode tip is 4√tmm to 6√tm
The protrusion disappears also by having a flat portion of m and an outer peripheral portion having a substantially tapered shape with an angle of 5 ° to 30 ° with respect to an axis orthogonal to the axis of the electrode. The number of spots is greatly increased, and it becomes an electrode for resistance spot welding of aluminum-based materials to be welded, which has excellent continuous spot performance.

Alternatively, as described in claim 6, the shape of the electrode tip is the thickness tm of the thin plate side of the material to be welded.
When m, the diameter of the electrode tip is 4√tmm to 6√tm
Only in the range of m, there is a spherical portion having an appropriate radius of curvature,
And, the outer peripheral portion is 5 ° to the axis orthogonal to the axis of the electrode.
By forming a substantially tapered shape having an angle of 30 °, the number of spots at which protrusions disappear is greatly increased, and the electrode becomes a resistance spot welding electrode of an aluminum-based material to be welded having excellent continuous spot performance. .

Alternatively, as described in claim 7, the shape of the electrode tip is the thickness tm of the thin plate side of the material to be welded.
When m, the diameter of the electrode tip is 4√tmm to 6√tm
Also, by providing a protrusion having a height of 0.1 tmm to 0.3 tmm in m, and forming a flat portion of at least 1 mm or more over the entire circumference from the outer wall of the protrusion on the outer peripheral portion of the protrusion. The number of spots for vanishing projections is greatly increased, and the electrode becomes a resistance spot welding electrode of an aluminum-based material to be welded having excellent continuous spot performance.

Then, as described in claim 8,
By forming a shape in which a corner portion or an outer wall portion of the projection and a flat portion are connected by a curved surface having an appropriate curvature radius, and as described in claim 9, the tip shape of the projection is a flat surface. Or by setting the tip shape of the projection to be a spherical surface having an appropriate radius of curvature as described in claim 10, The protrusion at the tip is maintained and the continuous dot performance is significantly improved.

Further, in the resistance spot welding method for an aluminum-based material to be welded according to the present invention, as described in claim 11, when the resistance spot welding is performed on the aluminum-based material to be welded, the electrical conductivity of the electrode is reduced. 97IACS
% And the Vickers hardness difference between the electrode and the material to be welded is Hv20 or more at 200 ° C. or less and Hv15 or less at a temperature range of 250 ° C. to 400 ° C. Since the welding is performed using the welding material, the electrical conductivity of the electrode material and the hardness characteristics of the welding material at high temperature are optimized for resistance spot welding of the aluminum welding material. It is possible to obtain an average continuous spotting property and a good appearance quality of the welded portion.

In an embodiment of the resistance spot welding electrode and the resistance spot welding method for an aluminum-based material to be welded according to the present invention, as described in claim 12, the material of the electrode is tough pitch copper. In addition, as described in claim 13, the material of the electrode is oxygen-free copper, so that aluminum having excellent continuous dot performance using an easily available electrode material can be used. In addition to being an electrode for resistance spot welding of the material to be welded, a good appearance of the welded portion can be obtained.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

Table 1 shows one embodiment of the present invention and two conventional examples.

As shown in Table 1, the resistance spot welding electrode of one embodiment of the present invention was manufactured by using tough pitch copper (C1100-
F) as a material, and the electrical conductivity exceeds 100 IACS%,
The Vickers hardness at room temperature is Hv104, the Vickers hardness at 200 ° C is Hv82, and the Vickers hardness at 400 ° C is Hv21.

On the other hand, the spot welding electrode of Conventional Example 1 is
Made of chrome copper (Cu-Cr) and has an electric conductivity of 75
~ 85IACS%, Vickers hardness at room temperature is Hv15
Vickers hardness at 9,200 ℃ is Hv138,400
The Vickers hardness at ° C has a characteristic of Hv96.

On the other hand, the resistance spot welding electrode of Conventional Example 3 is made of Ag-containing copper alloy for conduction (Cu-Ag) as a raw material, has an electric conductivity of 95 to 97 IACS% and a Vickers hardness of 117 at room temperature. Is to have.

The material to be welded is Al-4.5% by weight.
It is a JIS 5000 series aluminum-based material to be welded made of Mg and has a Vickers hardness of Hv65,2 at room temperature.
The Vickers hardness at 00 ° C. is Hv58, and the Vickers hardness at 400 ° C. is Hv8.

[0034]

[Table 1]

FIG. 1 shows a resistance spot welding electrode according to an embodiment of the present invention, a resistance spot welding electrode of Conventional Example 1 and a rolled aluminum alloy material (J) to be welded.
The respective temperature-hardness characteristics of (IS5000 series) are shown. As is clear from FIG. 1, the electrode (Chromium copper) of Conventional Example 1 mainly corresponds to welding of steel plates, and therefore exhibits high-temperature hardness characteristics that maintain hardness even at high temperatures.

On the other hand, in the electrode according to the present invention, as an example, tough pitch copper having an electric conductivity of more than 100 IACS% is used here, and 5000 is used as a material to be welded.
The high-temperature hardness characteristics of rolled aluminum alloys with a plate thickness of 1.0 mm are shown.

As is clear from FIG. 1, the electrode of the present invention has the characteristic that the hardness is greatly softened between 200 ° C. and 400 ° C., and particularly, the material to be welded is heated between 250 ° C. and 350 ° C. And the hardness of the electrode according to the invention are very close.

Thus, in the temperature range near the tip of the electrode during welding current application, the electrode should have high-temperature hardness characteristics that match the softening characteristics of the aluminum alloy that is the material to be welded, that is, the softening characteristics in a specific temperature range. Thus, when such an electrode and the material to be welded are combined and continuous spot welding is repeated, the initial shape of the electrode 1 shown in FIG. A protrusion 1a as shown in FIG. 2 (B) is formed at the tip of the electrode 1 corresponding to the depression formed on the surface of the welded portion.

At the same time, a flat portion 1b is similarly formed on the outer peripheral portion of the protrusion 1a together with continuous hit points. Then, as will be described later, in the electrode of the present invention, the expansion of the contact diameter of the electrode is suppressed by these, and it is possible to dramatically improve the continuous spotting property in spot welding of an aluminum alloy to the level of a steel plate.

Next, the operation will be described.

As shown in FIG. 2 (A), the radius of curvature RD of the electrode tip of the electrode according to the present invention and the electrodes shown in Conventional Example 1 and Conventional Example 3 is R as an example here.
A continuous welding point test was performed using the electrode 1 having 20 spherical surfaces and using a 5000 series aluminum alloy as the material to be welded.

The materials and properties of the materials to be welded and the electrodes used in this continuous spot test are as shown in Table 1, and the welding conditions of this test are as shown in Table 2.

[0043]

[Table 2]

Further, the evaluation method of the continuous hitting property is that the strength or the nugget diameter is the Class A minimum value established in JIS Z3140-1989, that is, the tensile shear strength is 172 kg.
f or the nugget diameter of 4 mm, whichever was earlier divided, was defined as the number of consecutive dots. However, the subsequent test was interrupted at a maximum of 9,000 points.

As described above, the electrode according to the present invention has a predetermined high temperature hardness characteristic, that is, a softening characteristic at a high temperature, and therefore corresponds to the depression of the surface of the material to be welded which is caused by spot welding at the initial stage of the welding point. Then, the tip portion of the electrode 1 softened by the welding heat is relatively easily deformed to self-form the protrusion 1a as shown in FIG. 2 (B). Further, since the pressure applied during welding is mainly received by the outer peripheral portion of the protrusion 1a, the flat portion 1b is self-formed on the outer peripheral portion. Then, the protrusion 1 self-formed corresponding to the depression on the surface of the welded portion at the initial stage of hitting
Since a is restrained in the direction in which the outer diameter portion 1c of the projection 1a expands outward due to the depression of the material to be welded even if the hit point advances, the expansion of the outer diameter portion 1c of the projection 1a is prevented.

Therefore, the contact diameter is the outer diameter d _{1 of the} protrusion 1a.
The current density during welding does not decrease because it is maintained at a constant value. Therefore, this makes it possible to achieve continuous hitting properties comparable to those of steel plates.

Here, the contact diameter means the diameter of the portion of the electrode that contacts the surface of the material to be welded, sandwiching the pressure sensitive paper between the electrode and the material to be welded (d _{1 in} FIG. 2B). , Fig. 2
In (C), it is a value obtained by measuring d ₂ ).

FIG. 3 shows changes in the contact diameter of the electrode according to the present invention and the electrodes of Conventional Example 1 and Conventional Example 3 during the continuous spot test with the number of continuous spots.

As is apparent from FIG. 3, in the electrode of the present invention, the protrusion 1a is self-formed at the tip of the electrode and is maintained as described above, so that the contact diameter is substantially constant even if the number of dots is increased. On the other hand, in the electrode of Conventional Example 1, the contact diameter rapidly expanded from the initial point of the hitting point, and the electrode life reached about 1000 hitting points.

Further, in the electrode of Conventional Example 3, the deterioration of the pickup is unlikely to occur, but the softening temperature is set to 400 ° C. to make the material rather suppress the softening of the electrode at a high temperature. The formation of the protrusions 1a was not observed. Therefore, although the contact diameter expanded more slowly than the electrode of Conventional Example 1, the contact diameter did not increase as the number of dots increased, and the electrode diameter reached about 3000 dots. It has reached the end of its life.

On the other hand, the electrode according to the present invention had no pickup deterioration and the appearance quality of the welded portion was good, and the life was still not reached even after 8,000 hit points.

The continuous hitting property can be almost estimated from the transition of the contact diameter of the electrode tip as shown in FIG.
The effect of the present invention on the conventional example is clear from FIG.

FIG. 4 shows the results of a continuous spot test by the electrode and the welding method according to the present invention. Even after 8000 spots, the nugget diameter was still almost constant and sufficient strength was satisfied. It was possible to secure continuous hitting properties similar to steel plates.

Incidentally, FIG. 2C shows the electrode 1 shown in Conventional Example 1.
1 shows a deterioration form of the electrode after the continuous dot test in the case of using No. 1, indentation 11a is generated at the electrode tip and the contact diameter d ₂ is enlarged.

FIG. 5 shows another embodiment.

FIG. 5 shows the experimental results of investigating the optimum range of the radius of curvature of the R-shaped electrode. Here, the R-shaped electrode is a shape in which a spherical surface having a constant radius of curvature RD is provided at the tip of the electrode 1 as shown in FIG.
mm, R20mm, R40mm, R75mm, R150
An experiment was conducted using an electrode having a thickness of mm and a flat electrode having a flat electrode tip with R being infinite. The material to be welded was a 5000 series aluminum alloy with a plate thickness of 1.0 mm. The welding conditions are the same as those shown in Table 2 of the above embodiment.

The vertical axis of FIG. 5 represents the number of points where the protrusion disappears, and the height of the protrusion 1a (h in FIG. 2B) represents the number of points where the required dimension cannot be maintained. The electrode life can be evaluated by the number of dots. In the present experiment, as described above, when measuring the contact diameter with the pressure-sensitive paper, the circular dent 2 as shown in FIG. 6 (A) is usually left on the pressure-sensitive paper, and the diameter of the circular dent 2 is measured. Although the contact diameter is used, as described above, when the height of the protrusion 1a becomes equal to or lower than the predetermined height, a crescent-shaped dent 3 is formed in addition to the circular dent 2 as shown in FIG. 6B. Therefore, the number of dots at which the crescent-shaped dent 3 is firstly generated is set as the number of dots at which the protrusion disappears in this experiment.

As a result of the experiment shown in FIG. 5, in the electrode according to the present invention, when the shape of the electrode tip is R, the radius of curvature RD is in the range of R8 mm to R40 mm, and the electrode tip of the electrode tip exceeds 3000 even if the number of points exceeds 3000. The protrusion did not disappear, but R75
mm and R150 mm, it disappeared at 500 points or less. No protrusion was formed on the flat electrode.

From the above, the shape of the R-shaped electrode in which the projection is easily formed at the tip of the electrode and the projection is maintained even when the number of hit points is advanced is such that the radius of curvature RD is R8 mm to R40 m.
It can be seen that the range of m is desirable.

As described above, the formation of the projection on the tip of the electrode is due to the transfer of the depression formed in the material to be welded. Therefore, the depression having a certain depth is formed on the surface of the welded portion of the material to be welded at the initial stage of the welding point. Therefore, if the radius of curvature RD of the electrode tip is too large, a protrusion having a required height cannot be formed. In addition, in order to maintain the diameter and height of the formed protrusion, the protrusion outer peripheral flat portion (Fig. 2) is mainly used to share the pressure force and suppress the protrusion's crushing and biting.
The flat portion 1b) in (B) is required. For this reason,
If the radius of curvature RD is too small, the protrusions are relatively easily formed, but since the area of the outer peripheral flat portion 1b of the protrusion is small, the protrusion disappears immediately and the height of the protrusion cannot be maintained.

More specifically, the plate thickness of the material to be welded is tm
When m, the ideal projection diameter is 4√tmm to 6√tm
m, the projection height is 0.1 tmm to 0.3 tmm, and at this time, the projection outer peripheral flat portion 1b has at least the diameter "projection outer diameter + 2 mm" as geometrically determined when the electrode shape is R8 mm. The above flat part 1b is required.

Therefore, the radius of curvature RD of the tip of the electrode is in the range of R8 mm to R40 mm, in which the most effective protrusions for improving the continuous spotting property are self-formed, and the diameter and height of the protrusions are easily maintained even if the number of spots increases. Therefore, it can be said that the electrode shape is excellent in continuous dot performance. Also, this radius of curvature RD
Since the portion forms the protrusion 1a and the flat portion 1b on the outer peripheral portion thereof, it is necessary to secure at least a width of 6√tmm or more in diameter.

FIG. 7 shows still another embodiment.

FIG. 7 shows the result of an experiment comparing the number of points of vanishing protrusions in various electrode shapes. In addition, FIG. 8 (A)
9B and 9C and FIGS. 9A and 9B show the electrode shapes used in this experiment.

Of these, FIG. 8A shows that the R-shaped tip is
When the plate thickness of the material to be welded is tmm, the diameter is 4√tmm
RF type electrode 1 (R
FIG. 8 (B) is an RR-shaped electrode in which another R portion (r ₁ ) having a larger radius of curvature is provided only in the range of diameters 4√tmm to 6√tmm of the tip of the R-shaped electrode. 1 (RR)
FIG. 8C shows an electrode having a radius of curvature R (R ₂ ) equal to the radius of the electrode, and the diameter of the tip portion is 4√t.
The DR type electrode 1 (DR) is shown in which another R portion (r ₂ ) having a large radius of curvature is provided only in the range of mm to 6√tmm.

Further, in FIG. 9A, the electrode tip has a diameter of 5.5.
0.2 mm high protrusion 1a having a flat portion 1e of mm
9 shows a protrusion F-shaped electrode 1 (protrusion F) having a protrusion outer peripheral flat portion 1b having a diameter of 12 mm on the outer periphery thereof.
In (B), the tip of the protrusion 1a is a spherical surface (r
₃₎ and other than the shows the projection R-shaped electrodes 1 (projections R) which was the same as FIG. 9 (A).

The electrode materials having the high temperature hardness characteristics shown in the present invention were used to form these electrode shapes, and the continuous dotability of these various electrode shapes was determined by the number of the points where the projections disappeared in the same manner as in the above embodiment. The results of comparative evaluation with the R20 type electrode of the example are shown in FIG. The welding conditions, the evaluation method and the like are the same as those in the above-mentioned embodiment.

As is apparent from FIG. 7, the RF type electrode 1
(RF), RR type electrode 1 (RR), DR type electrode 1 (D
R), projection F-shaped electrode 1 (projection F), and projection R-shaped electrode 1 (projection R) are the same as the R20-shaped electrode.
The protrusions at the electrode tip were maintained until the number of hit points exceeded 000, and the effect of improving the continuous hit property was recognized.

In any of the electrode shapes shown in FIGS. 8A, 8B, and 8C, the diameter of the electrode to be welded, whether it is a flat portion or a spherical surface having a radius of curvature, forms a protrusion at the electrode tip. 4√tmm to 6√tm when the plate thickness of the material is tmm
Since the radius of curvature is R8 mm to R40 mm for the portion of the outer peripheral portion that forms the protrusion outer peripheral flat portion, an ideal protrusion is formed, as in the above-described embodiment, and Since the height and diameter of the protrusions can be maintained even if the number of dots is increased, the continuous dot performance as an electrode is high. Therefore, the tip R (r ₂ ) portion of the electrode shown in FIG.
Similar effects can be obtained even with a DF-shaped electrode having a flat surface only in the range.

The electrode shape shown in FIGS. 9 (A) and 9 (B) is an electrode shape that is self-formed in the case of an R-shaped electrode and has a projection diameter of 4√tmm-6.
√tmm, protrusion height is 0.1tmm to 0.3tmm, and the protrusion outer diameter flatness is at least 2mm or more so that the ideal height and diameter of the protrusion can be maintained even if the number of points increases. The electrode shape has a high continuous dot performance. Note that the outer wall portion of the protrusion 1a and the corner portion of the protrusion outer peripheral flat portion 1b may have a tip shape formed by a curved surface having an appropriate radius of curvature (r ₄ ).

10 and 11 show still another embodiment.

In FIG. 11, the taper angle (θ) of the cone portion 1f of the cone-shaped electrode 1 as shown in FIG. 10 is variously changed, and the same continuous dot test as in the above embodiment is conducted up to 3000 dots. The result of having evaluated the continuous spotting performance of the electrode is shown.

The electrode used here is an electrode material having high temperature hardness characteristics according to the present invention, and the diameter of the electrode tip is 4 mm when the plate thickness of the material to be welded is tmm in FIG.
Provide a flat portion (d ₃ ) of √tmm to 6√tmm, and use a cone-shaped cone-shaped electrode 1 having a tapered shape with a predetermined angle (θ) with respect to the orthogonal to the axis of the electrode in the surrounding area. I was there.

In the present embodiment, as an example, the diameter of the flat portion (d ₃ ) is φ5.5 mm and the taper angle (θ) is 5.
Five kinds of electrodes 1 (CF) of °, 15 °, 30 °, 45 ° and 60 ° were used, and a 5000 series aluminum alloy rolled material having a plate thickness of 1.0 mm was used as a material to be welded.
The welding conditions, the evaluation method and the like are the same as those in the above-mentioned embodiment.

As a result, as shown in FIG. 11, in the three kinds of electrodes having the taper angles (θ) of 5 °, 15 °, and 30 °, the projections of the required shape are formed at the electrode tips, as in the above-mentioned embodiment. This was maintained up to 3000 hit points, but both electrodes with a large taper angle (θ) of 45 ° and 60 ° had protrusions formed at their tips, but as the number of hit points increased, it was relatively early (experimental). However, the required protrusion height could not be maintained at about 500 points, and the protrusion disappeared.

Therefore, in the case of the cone-shaped electrode 1 as shown in FIG. 10, the taper angle (θ) of the cone portion 1f is 5 ° to.
At 30 °, it can be said that the electrode has a shape capable of obtaining high continuous dot performance as in the case of the above embodiment. In the case of such a cone-shaped electrode shape, the diameter of the electrode tip is 4√tmm to 6√tmm when the plate thickness of the material to be welded is tmm. Correspondingly, a protrusion was formed on the tip of the electrode relatively easily. However, if the taper angle (θ) of the cone portion 1f is larger than 30 °, it is formed on the outer periphery of the protrusion and receives the electrode pressure force during welding. The area of the flat portion is reduced. Therefore, the surface pressure due to the applied pressure becomes high, and the vicinity of the electrode tip including the formed protrusion is crushed, and the height of the protrusion at the electrode tip decreases as the number of dots increases. Since the electrode life is reached relatively early, the taper angle (θ) is 30 °.
The following is recommended.

In the case of an electrode having a taper angle (θ) of 30 ° or less, a flat portion having a required area is formed on the outer peripheral portion of the protrusion, so that the same protrusion as that of the above-described embodiment is formed. The continuous dot performance is high because the height and diameter of the protrusions are kept constant even if the number of dots is advanced.

In this embodiment, the tip of the cone-shaped electrode is a flat surface (d ₃ ), but the same performance can be obtained even if the tip is a spherical surface provided with an appropriate radius of curvature. Needless to say, as mentioned above. Further, in the present embodiment, the cone portion of the cone-shaped electrode has a conical shape in which the tapered surface is a straight line in the front view as shown in FIG. 10. However, for example, this straight line portion has a relatively large curvature. The shape may be a convex R having a radius, a concave R, or an arbitrary curved line.

[0079]

As described in claim 1, the electrode for resistance spot welding of the aluminum-based material to be welded according to the present invention is used in the resistance spot welding of the aluminum-based material to be welded. Conductivity is 97IA
Vickers hardness Hv80 or more at CS% or more and 200 ° C. or less, Vickers hardness Hv3 at 400 ° C. or more
Since the Vickers hardness is softened from Hv80 or more to Hv30 or less between 200 ° C. and 400 ° C. so as to be 0 or less, the electrical conductivity of the electrode material, The hardness characteristics for the material to be welded at high temperature will be optimized for resistance spot welding of the aluminum-based material to be welded, that is, for the electrode, the high-temperature hardness characteristics that match the softening characteristics of the aluminum alloy that is the material to be welded, that is, Since it has softening characteristics in a specific temperature range, by making the shape of the electrode tip a specific shape, it is possible to keep the contact diameter of the electrode tip constant at continuous welding points, that is, the current density during welding. Can be maintained at a constant level, and it is possible to obtain continuous spotting properties similar to steel plates and good appearance quality of welded parts. Electrode life and reduced as in the conventional during the resistance spot welding um based welded material also appearance quality of the weld results in significantly better effect becomes to be solved is deteriorated.

In the embodiment of the resistance spot welding electrode of the aluminum-based material to be welded according to the present invention, as described in claim 2, the shape of the electrode tip has a curvature of R8 mm to R40 mm at the electrode tip. When it is R-shaped with a radius and the thickness of the thin plate side of the material to be welded is tmm, the R-shaped part is at least 6√ in diameter.
By ensuring tmm or more, it becomes possible to easily form protrusions at the electrode tips and to maintain the protrusions well even if the number of dots is advanced, and to significantly increase the number of dots to be extinguished. It is possible to increase the number of electrodes, and it is possible to obtain a resistance spot welding electrode of an aluminum-based material to be welded having excellent continuous spot performance, which is a remarkably excellent effect.

Further, as described in claim 3, when the shape of the electrode tip is tmm and the thickness of the thin plate side of the material to be welded is tmm, a flat surface having a diameter of 4√tmm to 6√tmm is formed at the electrode tip. And the outer periphery has a radius of curvature of R8 mm-
By adopting an R shape of R40 mm, it becomes possible to easily self-form the protrusion at the electrode tip,
Moreover, even if the number of hit points progresses, the protrusions can be maintained well, and the number of hit points that disappears the protrusion greatly increases.
A remarkably excellent effect that it can be used as an electrode for resistance spot welding of an aluminum-based material to be welded having excellent continuous spot performance is brought about.

Alternatively, as described in claim 4, the shape of the electrode tip is R8 mm to R40 mm at the electrode tip.
R-shape having a radius of curvature of, and the thickness of the thin plate side of the material to be welded is tmm, the diameter of the tip of the R-shape is only in the range of 4√tmm to 6√tmm, The number of projection vanishing spots is also significantly increased by having a shape composed of at least two or more compound spherical surfaces or compound curved surfaces having a different radius of curvature larger than the radius of curvature of the electrode. It is possible to obtain a remarkably excellent effect that it can be used as a resistance spot welding electrode of an aluminum-based material to be welded, which is excellent in continuous spotting performance.

Alternatively, as described in claim 5, the shape of the electrode tip is the thickness tm of the thin plate side of the material to be welded.
When m, the diameter of the electrode tip is 4√tmm to 6√tm
The protrusion disappears also by having a flat portion of m and an outer peripheral portion having a substantially tapered shape with an angle of 5 ° to 30 ° with respect to an axis orthogonal to the axis of the electrode. The number of spots is remarkably increased, which brings about a remarkably excellent effect that the electrode can be used as a resistance spot welding electrode of an aluminum-based material to be welded having excellent continuous spot performance.

Alternatively, as described in claim 6, the shape of the electrode tip is the thickness tm of the thin plate side of the material to be welded.
When m, the diameter of the electrode tip is 4√tmm to 6√tm
Only in the range of m, there is a spherical portion having an appropriate radius of curvature,
And, the outer peripheral portion is 5 ° to the axis orthogonal to the axis of the electrode.
The resistance spot welding electrode of the aluminum-based material to be welded, which has an excellent number of spots for extinction of protrusions, is also significantly increased by forming a substantially tapered shape having an angle of 30 °. It is possible to obtain a remarkably excellent effect.

Alternatively, as described in claim 7, the shape of the electrode tip is the thickness tm of the thin plate side of the material to be welded.
When m, the diameter of the electrode tip is 4√tmm to 6√tm
Also, by providing a protrusion having a height of 0.1 tmm to 0.3 tmm in m, and forming a flat portion of at least 1 mm or more over the entire circumference from the outer wall of the protrusion on the outer peripheral portion of the protrusion. In addition, the number of spots for extinction of protrusions is significantly increased, and it is possible to obtain a remarkably excellent effect that the electrode can be used as a resistance spot welding electrode of an aluminum-based material to be welded having excellent continuous spot performance.

Then, as described in claim 8,
By forming a shape in which a corner portion or an outer wall portion of the projection and a flat portion are connected by a curved surface having an appropriate curvature radius, and as described in claim 9, the tip shape of the projection is a flat surface. Or by setting the tip shape of the projection to be a spherical surface having an appropriate radius of curvature as described in claim 10, The protrusion at the tip is maintained, and the remarkable effect that the continuous dot performance is remarkably improved is brought about.

Further, according to the resistance spot welding method for an aluminum-based material to be welded according to the present invention, when the aluminum-based material to be welded is resistance spot-welded, the electrical conductivity of the electrode is 97IACS
% And the Vickers hardness difference between the electrode and the material to be welded is Hv20 or more at 200 ° C. or less and Hv15 or less at a temperature range of 250 ° C. to 400 ° C. Since the welding is performed using the welding material, the electrical conductivity of the electrode material and the hardness characteristics of the welding material at high temperature are optimized for resistance spot welding of the aluminum welding material. It is possible to obtain a remarkably excellent continuous spotting property and a good appearance quality of the welded portion.

In an embodiment of the resistance spot welding electrode and the resistance spot welding method for an aluminum-based material to be welded according to the present invention, as described in claim 12, the material of the electrode is tough pitch copper. In addition, as described in claim 13, the material of the electrode is oxygen-free copper, so that aluminum having excellent continuous dot performance using an easily available electrode material can be used. It is possible to obtain an electrode for resistance spot welding of the material to be welded, and it is possible to obtain a good appearance of the welded part, which is a remarkably excellent effect.

[Brief description of drawings]

FIG. 1 is a graph showing temperature-hardness characteristics of a resistance spot welding electrode according to an embodiment of the present invention, a resistance spot welding electrode of Conventional Example 1 and a material to be welded.

FIG. 2 (A) shows an initial shape of an electrode for resistance spot welding according to an embodiment of the present invention, FIG. 2 (B) shows an electrode shape in the middle of continuous welding, and FIG. 2 (C) shows deterioration. It is each a schematic diagram which shows the shape of the modified conventional electrode.

FIG. 3 is a graph showing a transition of a contact diameter of a resistance spot welding electrode according to an example of the present invention and conventional examples 1 and 3 during a continuous spot test.

FIG. 4 is a graph showing a transition of a nugget diameter during a continuous spot test with an electrode according to an example of the present invention.

FIG. 5 is a graph showing continuous dot performance when an electrode shape according to a second embodiment of the present invention is used.

FIG. 6 is an explanatory diagram showing a contact diameter of an electrode according to a second embodiment of the present invention.

FIG. 7 is a graph showing continuous dot performance when an electrode shape according to a third embodiment of the present invention is used.

8 (A), (B) and (C) are schematic diagrams showing electrode shapes according to a third embodiment of the present invention.

9 (A) and 9 (B) are schematic diagrams showing an electrode shape according to a third embodiment of the present invention.

FIG. 10 is a schematic diagram showing an electrode shape according to a fourth embodiment of the present invention.

FIG. 11 is a graph showing continuous dot performance when an electrode shape according to a fourth embodiment of the present invention is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 electrode 1a protrusion of electrode tip 1b flat portion of outer periphery of protrusion 1c outer diameter portion of electrode tip 1d flat portion of electrode tip 1e flat portion of electrode tip 1f cone portion of electrode tip 2 circular dent 3 crescent-shaped dent 3

Claims (13)

[Claims] 1. An electrode used for resistance spot welding of an aluminum-based material to be welded has an electric conductivity of 97.
Vickers hardness Hv80 or more at IACS% or more and 200 ° C or less, Vickers hardness H at 400 ° C or more
A resistance spot of an aluminum-based material to be welded, characterized by using a material having a high-temperature hardness characteristic that the Vickers hardness is softened from Hv80 or more to Hv30 or less between 200 ° C and 400 ° C so as to be v30 or less. Welding electrode. 2. The shape of the electrode tip is R8 mm to the electrode tip.
It is R-shaped with a radius of curvature of R40mm, and when the thickness of the thin plate side of the material to be welded is tmm, the R-shaped portion is at least 6√tmm in diameter. An electrode for resistance spot welding of the aluminum-based material to be welded according to claim 1. 3. When the shape of the electrode tip is tmm and the thickness of the thin plate side of the material to be welded is tmm, the diameter of the electrode tip is 4√tmm.
The electrode for resistance spot welding of an aluminum-based material to be welded according to claim 1, wherein the electrode has a flat surface portion of ˜6√tmm and an outer peripheral portion thereof is an R shape having a radius of curvature of R8 mm to R40 mm. . 4. The shape of the electrode tip is R8 mm to the electrode tip.
R-type with a radius of curvature of R40 mm, and when the thickness of the thin plate side of the material to be welded is tmm, the diameter of the tip of the R-shape is only within the range of 4√tmm to 6√tmm. The aluminum system according to claim 1, wherein the aluminum system has a shape composed of at least two or more compound spherical surfaces or compound curved surfaces each having a different radius of curvature larger than the radius of curvature of the electrode. Electrodes for resistance spot welding of materials to be welded. 5. The diameter of the electrode tip is 4√tmm when the shape of the electrode tip is tmm and the thickness of the thin plate side of the material to be welded is tmm.
2. A flat portion having a size of ˜6√tmm, and an outer peripheral portion thereof having a substantially taper shape having an angle of 5 ° to 30 ° with respect to an axis orthogonal to the axis of the electrode. An electrode for resistance spot welding of the described aluminum-based material to be welded. 6. The diameter of the electrode tip is 4√tmm when the thickness of the electrode tip is tmm when the thin plate side of the material to be welded is tmm.
A spherical portion having an appropriate radius of curvature only in the range of up to 6√tmm, and its outer peripheral portion has a substantially tapered shape having an angle of 5 ° to 30 ° with respect to an axis orthogonal to the axis of the electrode. The resistance spot welding electrode of the aluminum-based material to be welded according to claim 1, wherein 7. The diameter of the electrode tip is 4√tmm when the thickness of the electrode tip is tmm when the thickness of the thin plate of the material to be welded is tmm.
A protrusion having a height of 0.1 tmm to 0.3 tmm and a flat portion of at least 1 mm or more is formed on the outer peripheral portion of the protrusion from the outer wall of the protrusion to the entire circumference. The electrode for resistance spot welding of the aluminum-based material to be welded according to claim 1. 8. The resistance spot of the aluminum-based material to be welded according to claim 7, wherein a corner portion or outer wall portion of the protrusion and a flat portion are connected by a curved surface having an appropriate radius of curvature. Welding electrode. 9. The resistance spot welding electrode for an aluminum-based material to be welded according to claim 7, wherein the projection has a flat tip shape. 10. The electrode for resistance spot welding of an aluminum-based material to be welded according to claim 7, wherein the tip shape of the protrusion is a spherical surface having an appropriate radius of curvature. 11. An electrode having an electric conductivity of 97 IACS when resistance spot welding an aluminum-based material to be welded.
% And the Vickers hardness difference between the electrode and the material to be welded is Hv20 or more at 200 ° C. or less and Hv15 or less at a temperature range of 250 ° C. to 400 ° C. A resistance spot welding method for an aluminum-based material to be welded, which comprises performing welding using the welding material. 12. The resistance spot welding electrode and the resistance spot welding method for an aluminum-based material to be welded according to claim 1 or 11, wherein the material of the electrode is tough pitch copper. 13. The electrode for resistance spot welding of an aluminum-based material to be welded and the resistance spot welding method according to claim 1, wherein the material of the electrode is oxygen-free copper.