JPH04322886A - Method and device for resistance welding of metallic plate - Google Patents

Abstract

PURPOSE:To provide the method and the device for extending an electrode service life in resistance welding of a metallic stock whose electrode service life is short at the time of resistance welding such as aluminum and aluminum alloy plates, and a metallic plating steel plate, and also, executing functionally welding. CONSTITUTION:This resistance welding method for a metallic plate supplies continuously conductive tapes 9, 10 between electrodes 1, 2 and stocks 11, 12 to be welded, and welds them through the conductive tapes, and also, this resistance welding device for a metallic plate is provided with feeding rolls 16, 18, supporting rolls 14, 15, coiling rolls 17, 19, and the electrodes 1, 2, supports the conductive tapes 9, 10 fed out of the feeding rolls by the supporting rolls, and supplies them continuously between the electrodes and the stocks 11, 12 to be welded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to aluminum and aluminum alloy plates, metal plated steel plates (for example, Zn, Zn
The present invention relates to a method and apparatus for efficiently welding metal materials such as alloys, Sn, Sn alloys, etc., which have a shorter electrode life than rolled steel sheets, while extending the electrode life in resistance welding.

0002

[Prior art and its problems] Conventionally, when resistance spot welding metals such as rolled steel plates, aluminum and its alloys, and Zn-plated steel plates, JIS
Z 3234-1977 Using the first or second type of "conducting electrode material for resistance welding", the electrode shape is JI
Using what is specified in S C 9304-1986 "Shape and dimensions of spot welding electrodes", as shown in Figure 5,
Two or more objects to be welded 11 and 12 are overlapped, sandwiched between upper and lower electrodes 1 and 2, and welded by applying pressure and electricity to form a nugget 13. As the welding machine, a resistance welding machine such as a single-phase alternating current type, a single-phase rectification type, a three-phase rectification type, a three-phase low frequency type, a capacitor type, an inverter type, etc. is used. Resistance spot welding is often used as a joining method in the assembly process of automobiles and other mass production using conventional rolled steel sheets.The reason for this is that it is a very efficient welding method that can weld at one point in a few seconds. In addition, once the welding conditions are set, even amateurs and robots can easily weld, and stable weld nuggets and joint strength can be obtained, making it suitable for mass production. In addition, when resistance spot welding rolled steel sheets conventionally used in automobiles, even chrome copper electrodes have an electrode life of 1
There were over 0,000 points, and the time required for dressing was also trivial. Note that dressing refers to preparing the tip of the electrode by cutting it into a predetermined shape or polishing it to a predetermined surface roughness before welding.
This refers to the number of welds that can continuously obtain a welded part with the required performance in one dressing. Examples of criteria for determining electrode life include the following. ■The number of consecutive points until the nugget diameter or tensile shear strength falls below the specified value, ■An alloy layer of the electrode and the material to be welded is formed at the tip of the electrode, and this is transferred to the welded part, changing the appearance. The phenomenon of damage is called pick-up, and includes the number of consecutive points before this occurs, and (2) the number of consecutive points before the electrode becomes welded to the covering welding material and cannot be removed. Generally, the method (2) is often used, so the method (2) is used for the electrode life in this specification. As mentioned above, the electrode life of resistance spot welding on an automobile assembly line using conventional rolled steel plates is said to be 10,000 points or more, but the electrode life of resistance spot welding of aluminum or aluminum alloy is 200 to 50 points.
It is said that the electrode life span is 0 points, and in the case of Zn-plated steel sheets, 1000 to 2000 points is said to be the electrode life. Thus, aluminum or aluminum alloy,
Various welding methods have been proposed for welding materials with short electrode life, such as Zn-plated steel sheets. A representative example thereof is Japanese Patent Application Laid-open No. 159288/1983. This is an electric resistance welding method for aluminum or aluminum alloys, which is characterized by interposing an insert material with higher electrical conductivity than the electrode between the electrode and the workpiece when welding aluminum or aluminum alloys together. It is. As shown in FIG. 6, the electrodes 1 and 2, the material to be welded 11,
A highly electrically conductive insert material 29 is interposed between the electrodes 12 to suppress the temperature rise of the contact portion 30, shallowly penetrate the material to be welded in the plate thickness direction, prevent welding surface cracks, and extend the life of the electrode. This is a way to extend the

By the way, in the automobile industry, since rolled steel sheets have poor corrosion resistance, recently plated steel sheets, in which steel sheets are plated with Zn, Zn alloy, etc. to improve corrosion resistance and paintability, have been used. When this material is resistance spot welded, the heat generated between the electrode-plated steel sheets may cause the Zn or Zn alloy to melt and weld to the electrode due to its low melting point, or the copper or copper alloy of the electrode may easily alloy with these metals. An alloy of copper and the material to be welded is generated at the tip of the electrode, and this may adhere to the surface of the material during welding or be stamped, resulting in pick-up that makes the dents at the welding area extremely dirty. Furthermore, the electrode is worn out because this alloy layer is successively transferred to the welding surface of the material to be welded. In particular, the wear at the center of the electrode is large, so the electrode tip becomes concave, and as a result, the nugget diameter and tensile shear strength of the welded part decrease, and the electrode life span is reduced to 1000.
The score drops to ~2000 points. By cutting or polishing the electrode and reshaping (dressing) the tip to its regular shape, welding becomes possible again, and the nugget diameter and tensile shear strength are restored to their original values. For this reason, when spot welding Zn-plated steel plates or the like, dressing must be performed more frequently than when rolling steel plates, resulting in a significant drop in welding efficiency. Also, due to the time and expense required for this, Z
The cost of welding n-plated steel sheets was higher than that of welding rolled steel sheets, which was a problem.

[0004] In order to prevent global warming, energy saving of automobiles is progressing, and it is said that reducing the weight of the automobile by 10% can save about 10% of energy. For this reason, the amount of aluminum alloy used as a material for automobiles is increasing. The melting point of aluminum and aluminum alloys is about 1/2 or less than that of rolled steel sheets, but their thermal and electrical conductivity are about 3 times higher, so they can be welded at higher currents and in a shorter time than when welding rolled steel sheets. There must be. Furthermore, since an oxide film that is insulating and has a high melting point is formed on the surface of aluminum and aluminum alloys, it has a great effect on resistance spot welding. For example, in resistance spot welding, when an electrode is in contact with a material and a current flows, there is an insulating film between the electrode and the material, which generates a lot of heat, causing the electrode itself to heat up or become alloyed with the material. However, the electrodes are worn out for the same reason as spot welding of plated steel sheets mentioned above. For this reason, the electrode life of aluminum and aluminum alloys is said to be 200 to 500 points. With such a short electrode life, electrode dressing becomes very frequent, which becomes a bottleneck and a problem in mass production of automobiles and the like. The method disclosed in JP-A No. 61-159288 is a good method for extending the life of the electrode, but the method of attaching a thick insert of about 0.2 mm, which is about twice the thickness of the electrode, does not require welding. It was difficult to achieve the same level of efficiency as conventional rolled steel plates.

[0005]

[Problems to be Solved by the Invention] The object of the present invention is to provide aluminum, aluminum alloys, metal-plated steel sheets (for example, Zn, Zn alloy plating, Sn, Sn alloy plating, etc.)
The purpose of the present invention is to provide a welding method and apparatus that extend the life of electrodes in resistance welding of metals such as metals, and dramatically improve welding efficiency.

[0006]

[Means for Solving the Problems] The present invention provides resistance welding of metal plates, characterized in that a conductive tape is continuously supplied between an electrode and a material to be welded, and welding is performed via the conductive tape. Claim 1 provides a method, comprising a feed roll, a support roll, a take-up roll, and an electrode, wherein the conductive tape fed out from the feed roll is supported by the support roll, and the conductive tape is continuously connected between the electrode and the material to be welded. Claim 2 provides a resistance welding apparatus for metal plates, characterized in that the feed roll and take-up roll are of a cassette type. Claim 3, characterized in that the feed roll and take-up roll are replaced by a support roll and a drive roll, and the conductive tape is an endless tape.
A fourth aspect of the present invention provides the apparatus for resistance welding metal plates. The above-mentioned conductive tape can be made of pure copper, copper alloys, iron, nickel, titanium, chromium, silver, gold, and alloys thereof, as well as stainless steel, single materials, composite materials, and composite materials, as well as conductive metals and alloys. is applicable. In addition, a tape wound into a roll, a cassette type, or a tape connected endlessly can be used, and the device automatically selects the tape at regular intervals. An automatic feeding device with a feed roll, a cassette system, etc. is provided, and in the case of endless tape, a drive roll is provided. Note that the present invention can also be applied to cases where the electrode has two heads or a large number of electrodes. Further, the present invention can be provided in a robot welding gun and used in conjunction with a robot.

[0007]

[Operation] According to the method and apparatus described above, welding current flows from the electrode through the conductive tape to the materials to be welded, and due to the resistance between the materials to be welded, heat is generated and melts, forming a nugget. However, since the conductive tape has good heat dissipation properties, there is little heat generation between the electrode and the conductive tape, and there is no bonding, and there is almost no wear on the electrode. Furthermore, there is little heat generation between the conductive tape and the material to be welded, and the welding does not occur. Continuous welding is possible by winding conductive tape around a take-up roll and supplying and moving it between the electrode and the material to be welded each time one or more points are welded to perform welding one after another. Become. In addition, a conductive tape is wound around a cassette roll, and is automatically supplied between the electrode and the material to be welded each time one or more points are welded. After welding, the tape is moved and the next weld is performed. By doing this, you will be able to score consecutive points. By repeating this process, welds with all nuggets and indentation surfaces in good condition can be continuously obtained, electrode wear is extremely low, electrode life is extended, and welding efficiency is dramatically improved. Furthermore, by using an endless tape as the conductive tape, the device can be made smaller and the same effect can be achieved. The above-mentioned conductive tapes are made of pure copper, copper alloy, iron, titanium, nickel, chromium, silver, gold, stainless steel, etc., as well as laminated materials and composite materials.
Conductive metals and alloys can be applied.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Example 1 FIG. 1 is a schematic diagram showing an aspect of Example 1 of the present invention. Upper electrode 1 and lower electrode 2 comply with JIS Z 3232
16 mmφ of chromium copper (1% Cr-Cu alloy) corresponding to the two types of
It was set to 0 mm. The electrode has a 9mmφ cooling hole 3 for cooling.
4 is open and water at 15°C passes through conduits 5 and 6 7 and 8.
Water was flowed at a rate of 18 liters/min to cool the electrode. Materials to be welded 11 and 12 are Al-Mg alloy 5182-
A plate having a thickness of 1 mm, a width of 30 mm, and a length of 200 mm was used. Welding is performed by stacking two sheets of the materials to be welded 11 and 12, and using conductive tapes 9 and 10 wound around feed rolls 16 and 18 and take-up rolls 17 and 19, respectively, to the upper electrode 1 and the materials to be welded 11 and the lower electrode. It is set between the electrode 2 and the material to be welded 12. The conductive tape is made of pure copper, which has higher conductivity than the chromium copper of the electrode.
It has a thickness of 50 μm and a width of 16 μm, and is wound around feed rolls 16 and 18, and is welded to the welding point by winding devices 20 and 21 in synchronization with the welding machine, and when welding of one point is completed, the electrode 1, 2 separates from the materials to be welded 11 and 12, 15
The conductive tape is moved through support rolls 14 and 15 in units of mm and supplied to the welding location, and the used conductive tape is sequentially wound onto take-up rolls 17 and 19. Welding was carried out using a single-phase rectifier resistance welder, with a welding current of 220
Welding was carried out at intervals of 5 seconds per point under the welding conditions of 00A, electrode pressure of 1960N, and energization time of 5 cycles. Before welding, the tip of the electrode was dressed with #1000 emery paper, and then 12,000 points were continuously welded, and the welded specimen was covered with a peeling jig (referred to as a peel test jig) 28 as shown in Figure 4. One end of the welding material 11 was pinched and peeled off while rounding to obtain a nugget 13. Its major axis and minor axis were measured with calipers, and the nugget diameter was calculated using the following formula. Nugget diameter = (long diameter + single diameter) ÷ 2 (mm) The nugget diameter for the electrode life was set to 4 mm, which is the minimum nugget diameter for class A according to JIS Z 3140. For comparison, welding was performed using the same welding machine, the same welding conditions, and the same welding speed as in the previous case using the conventional method in which the electrodes 1 and 2 directly contact the materials 11 and 12 to be welded without using a conductive tape. Ta. Also, JP-A-61-1
In order to reproduce the method of No. 59288, the same conductive tape was cut into 30 mm pieces and manually attached to each welding location, and welded using the same welding machine, the same welding conditions, and the same welding interval. The results are shown in Table 1.

[0009]

[Table 1]

As is clear from Table 1, according to the method of the present invention, all 12,000 welds have a nugget diameter of 4 mm.
That was it. In other words, the electrode life was 12,000 points (or more). Changes in the shape of the electrode tip at this time were investigated at every 50 points by inserting pressure-sensitive paper between electrodes 1 and 2 and the materials to be welded 11 and 12, and applying only pressure without applying electricity (approx.
Even after 12,000 points welding, electrode 1
, 2 had no change in tip shape. Further, the time required for welding was 62,400 seconds (17.3 hours). On the other hand, welding using the conventional method that does not use conductive tape resulted in 212 nugget points with a nugget diameter of 4 mm or less. In other words, the electrode life was 211 points. In addition, as a result of examining the change in the shape of the electrode tip at that time using pressure-sensitive paper, it was found that at the 50th point, the centers of both the upper and lower electrodes had already deformed into a concave shape, and as the number of points increased, the electrodes were worn out and the contact became larger. It had become. When manually welding a conductive tape with a length of 30 mm, 12,000 points were welded, and all nuggets had a diameter of 4 mm or more, but the time required was 1.
It took 22,400 seconds (34.0 hours), which is twice as long as the method of the present invention. Example 2 FIG. 2 is a schematic diagram showing an aspect of Example 2 of the present invention. The upper electrode 1 and the lower electrode 2 are made of chromium-zirconium-copper alloy (0.5
%Cr-0.2%Zr-Cu alloy) with a diameter of 16 mm was used, and the electrode tip shape was R-shaped, and R = 150 mm. Electrodes 1 and 2 had holes of 9 mm diameter for cooling, and water at 15° C. was flowed through a conduit at a rate of 18 liters/min to cool the electrodes (not shown). Materials to be welded 11, 12
5182-O, which is an Al-Mg alloy, was used with a plate thickness of 1 mm, a width of 30 mm, and a length of 200 mm. For welding, an automatic feeder was used that moved 30 mm every time two sheets of the materials to be welded 11 and 12 were stacked and automatically welded at one point. Cassette 22
, 23 feed rolls 16, 18, take-up rolls 17, 19
The conductive tapes 9 and 10 wrapped around the upper electrode 1
and the material to be welded 11, and are set between the lower electrode 2 and the material to be welded 12. The conductive tape is made of pure copper with higher conductivity than electrodes 1 and 2, and has a thickness of 70 μm and a width of 16 mm.
6 and 18, and this is wound by winding devices 20 and 21.
When the electrodes 1 and 2 are separated from the materials to be welded 11 and 12 at every second welding point by synchronizing the welding machine with the welding point,
The ribbon is moved by 15 mm through support rolls 14 and 15 to be supplied to the welding location, and the used ribbon is sequentially wound onto take-up rolls 17 and 19. The welding machine and welding conditions were the same as in Example 1, and 12,000 points were welded at 2 second intervals, and all of them were subjected to a peel test to determine the nugget diameter. The results are shown in Table 2.

[0011]

[Table 2]

As can be seen from Table 2, all 12,000 nuggets produced by the method of the present invention had a nugget diameter of 4 mm or more. In other words, the electrode life was 12,000 points (or more). After 12,000 points of welding, pressure-sensitive paper was sandwiched between electrodes 1 and 2 and the materials to be welded 11 and 12, and only pressure was applied without applying electricity. As a result, the tip shapes of electrodes 1 and 2 had changed. There wasn't. Also, the time required for welding was 2400
0 seconds (6 or 7 hours), making the method of the present invention very efficient compared to conventional welding methods. Example 3 FIG. 3 is a schematic diagram showing an aspect of Example 3 of the present invention. Upper electrode 1 and lower electrode 2 comply with JIS Z 3232
1 of chromium copper (1% Cr-Cu alloy) corresponding to two types of
6mmφ is used, and the electrode tip shape is R-shaped, R = 150.
mm. The electrodes have holes 3 and 4 with a diameter of 9 mm for cooling, and water at 15°C passes through the conduits 5 and 6.
The electrode was cooled by flowing water at a rate of liter/min. The materials to be welded 11 and 12 have a plate thickness of 0.8 mm, a width of 30 mm, and a length of 2.
00 mm double-sided Zn-plated steel plate, Zn layers 24, 2
5, 26, and 27 are attached at 20g/m2. Welding is
Two sheets of materials to be welded 11 and 12 are stacked, and support rolls 16 and 18 are used instead of the feed rolls, and drive rolls 17 and 19 are used instead of the winding rolls. An endless conductive tape 9,
10, the upper electrode 1, the material to be welded 11, and the lower electrode 2, respectively.
and the material to be welded 12. The conductive tape is
Made of pure copper with higher conductivity than the chromium copper of the electrode, 30μm thick.
It has a width of 16 mm and is supported by support rolls 16 and 18. Instead of a winding device, the drive devices 20 and 21 synchronize with the welding machine at the welding location, and when welding at one point is completed, the electrode 1 , 2 are separated from the materials to be welded 11 and 12,
It moves through support rolls 14 and 15 in increments of 15 mm and is endlessly supplied to the welding location. Welding was carried out using a single-phase AC resistance welding machine, with a welding current of 90
Welding was carried out at intervals of 5 seconds per point under the welding conditions of 00A, electrode pressure of 1960N, and current application time of 8 cycles. Before welding, the tip of the electrode was dressed with #1000 emery paper, and then 12,000 points of welding were performed continuously. After welding, all were subjected to a peel test to determine the nugget diameter. The nugget diameter for the electrode life was set to 3.8 mm, which is the minimum nugget diameter for class A according to JIS Z 3140. For comparison, welding was performed using the same welding machine, the same welding conditions, and the same welding speed as in the previous case, using the conventional method in which the electrodes 1 and 2 directly contact the materials 11 and 12 to be welded without using a conductive tape. went. Further, the same conductive tape was cut into 30 mm pieces and manually attached to each welding location, and welding was performed using the same welding machine, the same welding conditions, and the same welding interval. The results are shown in Table 3.

[0013]

[Table 3]

As can be seen from Table 3, all of the 12,000 welds made by the method of the present invention had a nugget diameter of 3.8 mm.
That was it. In other words, the electrode life span was 12,000 points or more. At this time, the state of the electrode tip was examined at every 50 points by inserting pressure-sensitive paper between electrodes 1 and 2 and the materials to be welded 11 and 12, and applying only pressure without applying electricity (about 10 seconds per point). ), the tip shapes of electrodes 1 and 2 did not change even after 12,000 point welding. Further, the time required for welding was 62,400 seconds (17.3 hours). On the other hand, the nugget diameter of 1251 points was 3.8 mm or less when welded by the conventional method without using conductive tape. In other words, the electrode life was 1250 points. In addition, as a result of examining the change in the shape of the electrode tip at that time using pressure-sensitive paper, it was found that at the 50th point, the centers of both the upper and lower electrodes had already deformed into a concave shape, and as the number of points increased, the electrodes were worn out and the contact became larger. It had become. When manually welding a conductive tape with a length of 30 mm, 12,000 points were welded and all nugget diameters were 3.8 mm or more, but the time required was 1.
It took 22,400 seconds (34.0 hours), which is twice as long as the method of the present invention.

[0015]

Effects of the Invention The present invention enables continuous welding by supplying one or more conductive tapes to the welding location for each welding process when welding materials are layered and resistance welded as described above. In addition, electrode wear is extremely low, and electrode life and welding efficiency equivalent to that of rolled steel plates are now possible on aluminum, aluminum alloys, and various plated steel plates.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an embodiment of the present invention.

FIG. 3 is a schematic diagram showing an embodiment of the present invention.

FIG. 4 is a perspective view showing the peel test situation.

FIG. 5 is a schematic diagram showing a conventional resistance spot welding method.

FIG. 6 is a schematic diagram showing a conventional resistance spot welding method.

[Explanation of symbols]

1 Upper electrode 2 Lower electrode 3 Upper electrode cooling hole 4 Lower electrode cooling hole 5 Upper electrode conduit 6 Lower electrode conduit 7, 8 Cooling water 9, 10 Conductive tape 11, 12 Material to be welded 13 Nugget 14, 15 Support rolls 16, 18 Feed rolls 17, 19 Winding rolls 20, 21 Winding devices 22, 23 Cassettes 24, 25, 26, 27 Zn layer 28
Peel test jig 29 insert

Claims (4)

[Claims] 1. A method for resistance welding metal plates, characterized in that a conductive tape is continuously supplied between an electrode and a material to be welded, and welding is performed via the conductive tape. 2. A conductive tape comprising a feed roll, a support roll, a take-up roll, and an electrode, the conductive tape sent out from the feed roll is supported by the support roll, and is continuously supplied between the electrode and the material to be welded. A resistance welding device for metal plates, which is characterized by: 3. The metal plate resistance welding apparatus according to claim 2, wherein the feed roll and take-up roll are of a cassette type. 4. The resistance welding of metal plates according to claim 2, further comprising a support roll and a drive roll in place of the feed roll and take-up roll, and an endless tape as the conductive tape. Device.