JPH05185245A - Method for resistant-welding low electric resistant metal member - Google Patents

Abstract

PURPOSE:To improve the welding strength by reducing the welding current at the time of spot-welding two pieces of Al alloy-made rolled plates. CONSTITUTION:An exothermic member composed of amorphous Al ally-made ribbon 51 is inserted in between the parts 3, 4 to be welded of two Al alloy- made rolled plates 1, 2 and successively, by using one pair of electrode tips 6, 7, the spot-welding is executed to both plates 1, 2. As the ribbon 51 has very high electric resistance in comparison with the rolled plates 1, 2, this ribbon quickly generates heat even in low current and by this generated heat, the temp. of both parts 3, 4 to be welded are quickly raised, hence the electric resistance of these parts can be raised.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance welding method for a low electric resistance metal member, and more particularly to an improvement in a method for resistance welding a low electric resistance metal member of the same material type.

[0002]

2. Description of the Related Art Rolled aluminum alloy plates, which are low electrical resistance metal members, have high electric conductivity as well as low electric resistance.
A large current is required to raise the temperature of the welded part, and the electrode tip and the rolled plate are easily welded, which causes a problem.

Therefore, conventionally, a metal heating member having a higher electric resistance than the rolled plate is interposed between the welded portions of the rolled plate. In this case, as the heat generating member, one made of a metal material of the same material type or different material type as the rolled plate is used.

[0004]

However, the heat-generating member of the same material type does not serve as a fundamental solution to the above-mentioned problem because its electric resistance is as low as about twice that of the rolled plate. On the other hand, according to the heat generating member of a different material type, although the above problems can be substantially solved, it is not possible to obtain sufficient welding strength because the composition of the nugget and that of the rolled plate are significantly different, and reliability is extremely high. There is a problem that it is low.

In view of the above, it is an object of the present invention to provide the above resistance welding method capable of solving various problems by specifying the material of the heat generating member.

[0006]

According to the present invention, in resistance welding a low electrical resistance metal member of the same material type, the metal member is made of an amorphous metal material of the same material type, and the metal member is the same. A heat generating member having a higher electric resistance is interposed between the welded portions of the metal member.

[0007]

【Example】

[Example 1] As a low electrical resistance metal member of the same material type, A
Two rolled plates made of l-Mg alloy (A5182 material)
Was selected. This rolled plate has a thickness of 2.0 mm, a specific resistance (room temperature) of 5.2 μΩcm, and is smooth on both sides.

[0008] This rolled plate has a characteristic that when it reaches a temperature of about 300 ° C under electric heating, the rolled plate rapidly rises in temperature with the increase in electrical resistance and melts. The solidus of the rolled plate is at 570 ° C.

A heat-generating member made of an amorphous metal material of the same material type as the rolled plate and having a higher electric resistance than the rolled plate has a composition such as Al ₈₅ Ni ₅ Y ₈ Co ₂ (numerical value is atomic%). A ribbon made of an amorphous Al alloy was selected. This ribbon has a thickness of about 20 μm, a width of 27 mm, a specific resistance (room temperature) of 104.1 μΩcm, and is smooth on both sides.

This ribbon is manufactured by the single roll method, and the manufacturing conditions are that the diameter of the Cu roll is 250 m.
m, rotation speed of Cu roll 4000 rpm, size of ejection port of quartz tube nozzle 0.3 mm length, 30 mm width (slit type),
Gap between quartz tube nozzle and Cu roll 0.3m
m, atmosphere gas Ar, atmospheric pressure -40 cmHg.

The amorphous Al alloy has a vitrification temperature Tg of 273 ° C. and a crystallization temperature Tx of 295 ° C. (Tx> T).
g). Therefore, the crystallization temperature Tx of this amorphous Al alloy
Is the temperature below the solidus of the rolled plate.

FIG. 1 shows a temperature characteristic of electric resistance in the amorphous Al alloy.

As is apparent from FIG. 1, this amorphous Al
When the temperature exceeds the vitrification temperature Tg, the resistivity of the alloy rapidly increases by 20 to 30% with the occurrence of a glass transition phenomenon, and when it exceeds the crystallization temperature Tx, it rapidly increases as the crystallization progresses. It has the property of decreasing.
In addition, the vitrification phenomenon causes the amorphous Al alloy to be in a supercooled liquid state so that it is easily deformed.

In welding work, as shown in FIG.
A ribbon 5 ₁ is interposed between the welded parts 3 and 4 of the two rolled plates 1 and 2 to superpose both plates 1 and 2. Then the outer diameter is 19 mm,
A pair of electrode tips 6 and 7 with a radius (R) of the tip surface of 150 mm
The welded parts 3 and 4 are pressed with a pressing force of 800 kgf, and at the same time, spot welding (resistance welding) is performed by energizing between the electrode tips 6 and 7, and as shown in FIG. Join the spaces.

During this spot welding, a DC voltage of 20
When the relationship between the diameter d of the nugget 8 and the welding current was determined by setting to -30 V, the result shown by the line a in FIG. 4 was obtained.

In FIG. 4, a line b indicates a comparative example 1 in which a heat generating member is not interposed between the welded portions 3 and 4 of both rolling plates 1 and 2.
The line c corresponds to the welded parts 3 and 4 of both rolling plates 1 and 2.
This corresponds to Comparative Example 2 in which a crystalline Al alloy ribbon is interposed as a heat generating member. This crystalline Al alloy is Al-
It has a composition such as 6 wt% Cr-2 wt% Zr-3 wt% Fe and has a specific resistance (room temperature) of 10.2 μΩcm. Since the specific resistance (room temperature) of pure Al is 2.74 μΩcm, it can be said that this crystalline Al alloy has a relatively high electric resistance.

Further, FIG. 4, line e shows the welding strength guarantee limit. The welding strength is generally considered to be no problem if the diameter d of the nugget 8 is d ≧ 4 × t ^1/2 , where t is the thickness of the plate to be welded. In this embodiment, the tensile shear test is performed. From the results, the diameter d = 5.5 mm of the nugget 8 was set as the lower limit of the welding strength guarantee.

As is clear from FIG. 4, in the case of the present invention shown by the line a, the minimum welding current for exceeding the welding strength guarantee limit (line e) is about 19.4 kA, but the comparison shown by the line b. It is about 37 kA for Example 1 and about 33 kA for Comparative Example 2 shown by line c.

In the present invention, the reason why sufficient welding strength can be obtained even when the minimum welding current is low as described above is as follows.

That is, since the ribbon 5 ₁ has a high electric resistance, it heats sufficiently and rapidly even with a small current, and when the temperature exceeds the vitrification temperature Tg, the electric resistance rapidly increases as shown in FIG. Since it becomes even higher, the amount of heat generated also increases accordingly.

During this time, the heat generated from the ribbon 5 ₁ is successively propagated to both welded parts 3 and 4, and after the ribbon 5 ₁ becomes a supercooled liquid state by vitrification phenomenon, the welded parts 3 and 4 are welded.
By the pressing force acting on the welded parts, they are easily deformed and come into close contact with the welded parts 3 and 4, so that the propagation efficiency of the generated heat is enhanced.

As a result, the temperatures of the welded parts 3 and 4 rapidly rise, and when the ribbon 5 ₁ reaches the crystallization temperature Tx, the temperatures of the welded parts 3 and 4 also rise to about 300 ° C. After that, the electric resistance of the ribbon 5 ₁ sharply decreases, but the welded portions 3 and 4 rapidly reach the melting temperature due to the increase in the electric resistance accompanying the temperature rise.

As described above, when the electric resistance of the ribbon 5 ₁ suddenly decreases, a large current flows between the welded parts 3 and 4. As a result, the oxide film on both welded portions 3 and 4 can be removed, so that the welding strength can be increased and the pressure applied to both electrode tips 6 and 7 can be reduced.

The ribbon 5 ₁ melts in the welding process to form a part of the nugget 8. In this case, since the ribbon 51 and the two rolled plates ₁ and 2 are of the same material type, there is no great difference in composition between them, and therefore the welding strength is not impaired.

Rather, most of the intermetallic compounds produced by crystallization of the ribbon 5 ₁ have a grain size of 1 μm or less, and even the maximum grain size of 10 μm or less, so that they function as a reinforcing material for the nugget 8. Further, since these intermetallic compounds have a low diffusion rate in the nugget 8, they do not coarsen during the heating process such as heat treatment after welding.

When the welding current is further reduced, it is possible to avoid the pickup and prolong the life of the electrode tips 6 and 7, and to simplify the control device and reduce the equipment cost. [Example 2] As the metal member, the same rolled plate as that described above is used.

As the heat generating member, an aggregate of amorphous Al alloy powders having the same composition as that described above, that is, Al ₈₅ Ni ₅ Y ₈ Co ₂ (numerical value is atomic%) is used.

This powder was manufactured by the atomizing method under the condition of He gas pressure of 80 kgf / cm ² , and its temperature characteristic of electric resistance was the same as that of the ribbon 5 ₁ (see FIG. 1).

When forming the heat generating member,
-Hexane is blended to prepare a slurry, and the slurry is
As shown in FIG. 5, it is applied to the surface of the welded portion 3 of one of the rolled plates 2 to obtain an aggregate 10 of powder 9.

In welding work, as shown in FIG.
An assembly 10 is interposed between the welded parts 3 and 4 of the rolled plates 1 and 2 to superpose both plates 1 and 2, and then spot welding is performed under the same conditions as described above.

At that time, a DC voltage of 20 to 30 is applied in the same manner as described above.
When set to V and the relationship between the diameter d of the nugget 8 and the welding current was obtained, the results shown in FIG. 7 and line f were obtained.

As is clear from FIG. 7 and line f, according to the above-mentioned welding method, the minimum welding current for exceeding the welding strength guarantee limit (line e) is about 16.5 kA, which is the above-mentioned value. , FIG. 4, line a is even lower.

This is because the aggregate 10 is formed of the powder 9, so that the contact resistance inside the aggregate 9 becomes high and the aggregate 9 and the two welded parts 3 and 4 partially contact each other. By this, the contact resistance between them becomes high, so that the local melting of both welded parts 3, 4 is accelerated as compared with the case of the above-mentioned embodiment. After the powders 9 are in the supercooled liquid state, the powders 9 are easily deformed and integrated by the pressing force of the electrode tips 6 and 7 and are closely adhered to the welded parts 3 and 4. To do.

FIG. 8 shows another example for obtaining the partial contact. In this example, a number of ridges 11 are formed on one surface of the ribbon 5 _2. The ribbon 5 ₂ of the above with the same composition _{(Al 85 Ni 5 Y 8 Co} 2, numerical atomic%) made of amorphous Al alloy having.

Such a ribbon 5₂Is the single roll method
Gap between quartz tube nozzle and Cu roll at
To 1.0 mm and atmospheric pressure to 760 mmHg (1 atm).
Change each and set other conditions to the same as above
Therefore, it is manufactured. Ribbon 5 ₂The ridges 11 are Cu low
Formed on the contact surface with

FIG. 7, line g shows a ribbon 5 having ridges 11.
₂ shows the relationship between the diameter d of the nugget 8 and the welding current when spot welding is performed under the same conditions as described above.

As is clear from FIG. 7 and line g, in this case as well, the minimum welding current for exceeding the welding strength guarantee limit (line e) can be lowered to about 17.7 kA.

As the amorphous metal material for the heat generating member, in addition to the above examples, the composition Al ₉₀ Fe ₅ Ce ₅ (numerical value is atomic%),
Amorphous Al alloy such as specific resistance 91.2 μΩcm, crystallization temperature Tx 287 ° C., composition Al ₉₀ Nd ₁₀ (numerical value is atomic%), specific resistance 83.0 μΩcm, crystallization temperature Tx 230
Amorphous Al alloy such as C. can be used.
The present invention is also applied to seam welding and the like.

[0039]

According to the present invention, when resistance-welding a low electrical resistance metal member of the same material type, by using the heat generating member specified as described above, the welding current is lowered and the welding strength is reduced. In addition, the life of the electrode tip can be extended and the equipment cost can be reduced with the reduction of the welding current.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the heating temperature and the specific resistance of an amorphous Al alloy.

FIG. 2 is an explanatory diagram at the start of spot welding work.

FIG. 3 is an explanatory diagram at the end of spot welding work.

FIG. 4 is a graph showing the relationship between welding current and nugget diameter.

FIG. 5 is a cross-sectional view showing a state where a heat generating member is formed on a rolled plate.

FIG. 6 is a cross-sectional view showing a state in which a heat generating member is interposed between two rolled plates.

FIG. 7 is a graph showing the relationship between welding current and nugget diameter.

FIG. 8 is an enlarged sectional view of an essential part showing a state in which a heat generating member is interposed between two rolled plates.

[Explanation of symbols]

1, 2 Al-Mg-based alloy rolled plate (metal member) 3, 4 Welded portion 5 ₁ , 5 ₂ Amorphous Al alloy ribbon (heat generating member) 9 Amorphous Al alloy powder 10 Aggregate (heat generating member )

Claims (3)

[Claims] 1. A low electrical resistance metal member (1,
In resistance welding of 2), a heat generating member (5) made of an amorphous metal material of the same kind as the metal members (1, 2) and having a higher electric resistance than the metal members (1, 2). ₁ ,
5 _2, 10) said metal member (1, 2) resistance welding method of low electrical resistance metal member characterized by interposing between the welded portion (3, 4) each other. Wherein said at least one said heat generating member (5 _2, 10) and is allowed to partially contact, the method of resistance welding low electrical resistance metal member according to claim 1, wherein the welded portion (3,4) . 3. The heat generating member (5 ₁ , 5 ₂ , 10) comprises:
The resistance welding method for a low electric resistance metal member according to claim 1 or 2, which has a characteristic that the electric resistance sharply decreases at a temperature equal to or lower than a solidus line of the metal member (1, 2).