JPH0790431A - Electrode material for resistant welding and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an electrode material improved in the electrode service life, particularly in a resistant spot welding of Al and Al alloy by specifying Cr content in a Cu-Cr alloy and forming a continuous Cu-Cr entectic structure. CONSTITUTION:In the alloy composed of 0.3 to <1.5wt.% Cr, and the balance Cu with inevitable impurities, the structure is made of a continuous Cu-Cr entectic one. By this constitution, the electrode service life is drastically improved, and expecially in Al and Al alloy, the same electrode service life as the conventional galvanized steel sheet is obtd., and further, in the case of plated steel sheet, the electrode material for resistant welding having the same service life as the conventional rolled steel sheet is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention dramatically improves the electrode life even when using a plated steel sheet having a welding electrode life shorter than that of a rolled steel sheet, an aluminum or aluminum alloy sheet and its metal-plated material as the material to be welded. The present invention relates to a resistance spot welding electrode material and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, resistance spot welding is the most widely used method for joining materials in the assembly process of the automobile industry. Conventionally, rolled steel sheets have been widely used as materials for automobile body sheets, but recently, aluminum and aluminum alloys have come to be used due to the demand for lighter automobiles due to energy saving, environmental problems and the like.

These resistance spot welding electrodes have relatively high high-temperature strength, high electric conductivity and high thermal conductivity,
A chromium copper alloy, which is relatively low in cost, is often used. And the amount of chromium contained in this electrode is about 1 wt.
%, But the method for producing the electrode materials of these precipitation hardening copper alloys, the ingots cast from the molten metal of the predetermined components through the hot working step, solution treatment, cold working, The processing such as aging processing is performed. Conventionally, this manufacturing method is most suitable for mass production, and the cost can be the easiest.

When resistance spot welding is continuously performed by using these electrodes, the tip of the electrode reacts with the material to be welded and alloys, which is transferred to the material to be welded and is consumed. As a result, the current density is reduced, the welding nugget is reduced, and a predetermined strength (tensile shear load) cannot be obtained. When continuous spotting is performed by resistance spot welding as described above, the number of spots when the predetermined strength cannot be obtained is called the electrode life.

It is generally said that the electrode life when spot-welding a rolled steel sheet with an electrode made of a conventional chromium copper alloy or chromium-zirconium copper alloy is 10,000 points or more. On the other hand, the electrode life of the plated steel sheet is about 5,000 points. The number of aluminum alloy plates is about 1,000, and the number of aluminum alloy plates plated with metal such as Zn is less than that.

In the automobile industry, it is possible to improve the electrode life of plated steel sheets to 10,000 or more, which is comparable to that of rolled steel sheets, and to improve the electrode life of aluminum alloys and materials plated with it to 5,000 or more, which is comparable to that of current plated steel sheets. This is a problem, and the development of an electrode that can meet the problem has been desired.

[0007]

The present invention has been made as a result of studies on the above problems, and has developed an electrode that dramatically improves the electrode life in resistance spot welding of plated steel sheets, aluminum and aluminum alloys. It was done.

That is, one of the electrode materials of the present invention is an alloy containing Cu of 0.3 wt% or more and less than 1.5 wt% and the balance Cu and unavoidable impurities and having a continuous Cu-Cr eutectic structure. It is a feature.

Another one of the electrode materials of the present invention is 0.3
Includes Cr in an amount of at least wt% and less than 1.5 wt%
Cu, a continuous Cu-Cr alloy containing 1 wt% or less of one or more of transition metal elements other than g, P, Be, Al, rare earth metal elements, and Cr, and the balance Cu and inevitable impurities. It is characterized by having a eutectic structure.

Further, the method for producing the electrode material of the present invention is as follows: the alloy having the above composition is melted and cast, and the casting is performed at 800 to 1050 ° C. for 1 min to 10 hr.
Solution treatment, and then at 300-600 ℃ for 10min-10
The aging treatment for hr allows the Cu—Cr eutectic structure continuously formed during solidification to remain without impairing its continuity.

Further, in the above-mentioned manufacturing method, it is also effective to add cold working before solution treatment or cold working before or after aging treatment.

That is, the present invention refers to aluminum or aluminum alloy, for example, aluminum alloy, Al--Cu
System, Al-Mn system, Al-Si system, Al-Mg system, Al
-Mg-Cu system, Al-Mg-Si system, Al-Zn-M
The present invention relates to an electrode material used in resistance spot welding of an alloy material such as a g-based material or an Al-Zn-Mg-Cu-based material and a method for manufacturing the same, and also relates to Zn, Zn-F.
The present invention relates to an electrode material used for resistance spot welding of a plated steel sheet of e, Zn-Ni, Fe-P, etc., and a manufacturing method thereof.

The welding machine used for the resistance spot welding is a conventionally used single-phase AC welding machine, single-phase rectification welding machine, three-phase low-frequency welding machine, three-phase rectification welding machine, inverter welding machine, Any of a condenser type welding machine and the like may be used.

[0014]

When the content of Cr, which is the main additive element of the Cu alloy of the electrode material of the present invention, is less than 0.3 wt%, Cu-Cr eutectic formation is unlikely to occur, and when it is 1.5 wt% or more, the molten metal flow becomes poor and casting is difficult. Is coming.

Further, transition metal elements other than Si, Mg, P, Be, Al, rare earth metals, and Cr are added to enhance hardness, and if each is added in an amount of 1 wt% or more, the conductivity is lowered, Impair sex.

Further, the Cu--Cr eutectic structure having a continuous metal structure is formed by dispersing the eutectic structure by hot working or the like.
This is because it is presumed that the reaction with the material to be welded is suppressed rather than the homogenization. That is, FIG. 1 shows Cu-
FIG. 3 is a schematic view in which a cast structure of a 1% Cr alloy is enlarged to about 400 times, and a Cu—Cr eutectic crystallizes in a gap between primary α phases. FIG. 2 is a schematic diagram of the structure of the ingot which has been subjected to a normal hot extrusion process. The Cu—Cr eutectic structure as shown in FIG. 1 is completely destroyed and fine Cr particles are dispersed. On the other hand, FIG. 3 is a schematic diagram of the structure of the electrode of the present invention which has been subjected to thermomechanical treatment so that the Cu—Cr eutectic of FIG. 1 is not destroyed or dispersed as much as possible. The Cu-Cr eutectic is finely spheroidized, but the distribution itself does not change significantly (in a macroscopic manner, it is continuous as in FIG. 1). There is no loss.

The manufacturing method of the present invention is characterized by not dividing the eutectic structure as much as possible by not performing the hot working as described above. And the solution treatment temperature after casting is 800
If the temperature is lower than ℃, solution treatment cannot be performed sufficiently, and if it exceeds 1050 ℃, it may melt locally. Further, if the time is less than 1 min, solution treatment cannot be sufficiently performed, and if it exceeds 10 hr, the crystal grains become coarse, strength may be insufficient, and machinability may be deteriorated, which is further disadvantageous in terms of cost. .

Subsequent aging treatment below 300 ° C.
The aging is extremely slow and the aging time is too long to be industrial, and when it exceeds 600 ° C, it is overaged and the strength is insufficient. Also, if the aging time is less than 10 min, the aging will be insufficient,
If it is over 10 hours, it may be over-aged and its strength may be insufficient.
Also, it is disadvantageous in terms of cost.

If cold working is applied before the solution treatment, it is preferable to obtain a uniform and fine recrystallized structure during the solution treatment. Further, if cold working is added before the aging treatment, a large amount of Cr precipitation sites are introduced during aging, so that a fine precipitation state is obtained and the strength is increased, which is desirable. Further, even if cold working is added after the aging treatment, the strength becomes high due to work hardening, which is desirable.

[0020]

EXAMPLES Examples of the electrode life (continuous spotting property) of the resistance spot welding electrode according to the present invention will be specifically described below.

The electrode material of the present invention having the alloy composition shown in Table 1 and the comparative material were subjected to die casting and other processing as shown in Table 2. Then, with respect to each sample electrode, general performance, continuous spotting property, workability, etc. were measured as follows, and the results are shown in Table 3.

The general performance shows conductivity and Vickers hardness.

Regarding workability, the electrode element rod has a diameter of 16 mmφ,
It was processed to a height of 20 mm and was cold set up to a height of 5 mm with a pressure device, and the state of cracking at that time was shown. If cracked in this test, there is a risk of cracking in the cold forging process during electrode processing. In addition, there is a concern that the yield will decrease during electrode processing.
The evaluation of the workability is described as follows. ○: No cracks occurred ×: Cracks occurred

Regarding the electrode shape of each sample electrode, when the material to be welded for the electrode life test was an aluminum alloy, the R type had a diameter of 16 mm and R = 80 mm. And as the aluminum alloy concerned, A5182P with a plate thickness (t) of 1 mm
-O was used. The dimensions of the test piece were 30 mm in width and 200 mm in length, and two of them were stacked and used. The welding conditions are as follows.・ Welding equipment: Single phase rectification type resistance welding machine ・ Pressure force: 300kgf ・ Electrification time: 5 cycles ・ Welding current: Proper welding current value at each electrode (25000 ± 1000)
A) ・ Welding pitch: 30 mm ・ Spotting speed: 1 point / 2 seconds

On the other hand, in the electrode life test when the material to be welded is a Zn-plated steel plate, the electrode shape is DR type φ16 mm, tip φ6.
mm and 40 mmR. The material to be welded has Zn on both sides.
A Zn-plated steel sheet applied with 20 g / m ² was used. The size of the welding test piece was 0.7 mm in plate thickness (t), 30 mm in width, and 200 mm in length, and two pieces were used by stacking them. The welding conditions are as follows.・ Welding equipment: Single-phase AC resistance welding machine ・ Pressure force: 270 kgf ・ Electrification time: 3 cycles ・ Welding current: Proper welding current value at each electrode (8500 ± 500
A) ・ Welding pitch: 30 mm ・ Spotting speed: 1 point / 2 seconds

The electrode life was evaluated by peeling the welded portion with a peel test jig, measuring the major axis and minor axis of the nugget with a caliper at intervals of 10 points, and determining the nugget diameter by the following formula. Nugget diameter = (major axis + minor axis) / 2 (mm) And, until the nugget diameter cannot be secured at 4 x t ^1/2 , or during welding, electrode cracking or electrode welding occurs and subsequent welding The maximum number of welding spots before it was impossible was defined as the electrode life. Table 3 shows the electrode life test results.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

In the examples of the present invention, the electrode life was 5,000 or more for all aluminum alloy plates and 10,000 or more for all Zn-plated steel plates. On the other hand, the electrode life of the comparative example was much shorter than that of the product of the present invention.

[0031]

According to the electrode of the present invention, an electrode life equivalent to that of a conventional galvanized steel sheet was obtained for aluminum and aluminum alloy sheets. Further, even with respect to the plated steel sheet, 10,000 or more electrode life equivalent to that of the conventional rolled steel sheet was obtained. As described above, the electrode of the present invention can remarkably improve the life of the electrode as compared with the conventional electrode. Therefore, it greatly contributes to the improvement of resistance spot welding, which has been the biggest bottleneck of aluminum in mass production of automobiles, and the improvement of the electrode life of plated steel sheets. The electrode of the present invention is spot welding in which a plated steel sheet and a rolled steel sheet (non-plated steel sheet) are stacked, or a plated steel sheet and a rolled steel sheet are mixed (alternate).
It can also be applied to spot welding.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cast structure of a Cu-1% Cr alloy enlarged to about 400 times.

FIG. 2 is a schematic view showing a Cu-1% Cr alloy having the structure shown in FIG. 1 which is magnified about 400 times as large as the structure after ordinary hot extrusion.

FIG. 3 is a schematic view showing a Cu-1% Cr alloy having the structure shown in FIG. 1 magnified about 400 times as large as the structure after the thermo-mechanical treatment of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Tomiharu Okita 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Aluminum Co., Ltd. (72) Inventor Toshiya Okada 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Aluminum Industry Co., Ltd.

Claims (6)

[Claims] 1. An electrode material for resistance welding, comprising an alloy containing 0.3 wt% or more and less than 1.5 wt% Cr, the balance being Cu and unavoidable impurities, and having a continuous Cu—Cr eutectic structure. . 2. At least 1 wt% of Si, Mg, P, Be, Al, rare earth metal elements, and transition metal elements other than Cr, each containing 1 wt% of 0.3 wt% or more and less than 1.5 wt% Cr. An electrode material for resistance welding, characterized in that it is an alloy containing Cu, the balance being Cu and unavoidable impurities, and having a continuous Cu-Cr eutectic structure. 3. At least 1 wt% of each of one or more of Si, Mg, P, Be, Al, a rare earth metal element, and a transition metal element other than Cr, each containing 0.3 wt% or more and less than 1.5 wt% of Cr. % Or less, with the balance Cu and unavoidable impurities melted and cast, and then 1
Perform solution heat treatment for min to 10 hr and then at 300 to 600 ° C.
A method for producing an electrode material for resistance welding, which comprises performing an aging treatment for 10 min to 10 hr. 4. The method for producing an electrode material for resistance welding according to claim 3, wherein cold working is performed before the solution treatment. 5. The cold working is added before the aging treatment.
Alternatively, the method for producing the electrode material for resistance welding according to the item 4. 6. The cold working is added after the aging treatment.
6. A method for producing an electrode material for resistance welding according to any one of 5 to 5.