JPH0246309B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method of resistance welding a pair of members to be welded, at least one of which has a non-conductive coating.

(Prior Art) A composite wire is a composite wire made of an alloy wire of iron and nickel coated with copper, whose surface is oxidized and coated with borax, and has an oxide film on its surface. When welding this composite wire to a base for a high-output fluorescent lamp, for example, a so-called resistance welding method is used, in which the composite wire and the side wall of the base are overlapped, and this overlapping part is pressed between a pair of electrodes while applying electricity. It has been adopted.

(Problem to be Solved by the Invention) Since the oxide film on the surface of the composite wire is non-conductive, the electrical resistance between the electrode and the composite wire and between the composite wire and the side wall of the base is several tens of kilohms. At normal welding voltages, no current flows or is extremely small, resulting in frequent welding defects and unstable quality.

On the other hand, as seen in JP-A No. 50-104742, for example, a pair of welded members, both of which have non-conductive coatings, are superposed between a pair of electrodes, and a high frequency voltage is applied between the two electrodes. A technology that applies a pretreatment voltage that is superimposed with a low-frequency voltage to destroy the non-conductive coating, and then passes the welding current between both electrodes to keep the welding current almost constant and stabilize quality. It has been known.

However, in this case, the voltage of the pretreatment current is very high, and the area where the pretreatment current flows in the overlapping part of both members, in other words, the destruction area of the non-conductive film, changes, and as a result, the area sandwiched between the two electrodes changes. There is a drawback that the pressure area and the welding area do not match, and the welding area and welding strength vary widely.

In addition, as seen in Japanese Utility Model Publication No. 57-42622, for example, a pair of welded members, one of which has a non-conductive coating, is polymerized between a pair of electrodes to form a welded member with a non-conductive coating. A third electrode is provided, and a high pretreatment voltage is applied between the third electrode and the electrode on the side of the workpiece that does not have a non-conductive coating to destroy the non-conductive coating before welding. Techniques are being considered to eliminate variations in welding by passing an electric current through the welding process.

However, in this case, since the coating on the electrode side of the member having a non-conductive coating is not destroyed, the resistance of this undestructed coating portion is large, and therefore the welding resistance, in other words, the welding current, varies greatly, and the welding strength decreases. It has the disadvantage of large variations.

Furthermore, in the technology described in this Publication No. 57-42622, regardless of which member has a non-conductive coating, the point is that as long as the pretreatment current is passed through the overlapping surfaces of both members, the surface to be welded is Although it is stated that the non-conductive coating is always destroyed, in any case the non-conductive coating in contact with the electrode is not destroyed, so variations in welding current, in other words, variations in welding strength are not eliminated.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a welding method that can successfully resistance weld a member to be welded, at least one of which has a non-conductive coating on its surface, to produce a product with stable quality.

[Structure of the invention]

(Means for Solving the Problems) In resistance welding, the present invention provides a third electrode on a member to be welded having a non-conductive coating, and applies a high voltage between the third electrode and each of a pair of electrodes. Alternatively, a high frequency voltage is applied to destroy the non-conductive coating, and a welding current is passed through the destroyed portion of the non-conductive coating to perform stable welding.

(Function) The non-conductive coating of the welded member is usually formed on both the front and back surfaces or on the entire circumferential surface of the wire, and one side is brought into contact with the other welded part, and the other side is brought into contact with the electrode. Therefore, if a third electrode is provided on the welding member having a non-conductive coating and a high voltage or high frequency voltage is applied between the third electrode and each of the pair of welding electrodes, the back of the welding member may be Each non-conductive coating was destroyed to reduce the resistance of the coating when welding current was passed through these parts, making welding resistance and welding current almost constant, resulting in stable quality.

(Example) The details of the present invention will be explained by referring to the illustrated example.

The details of this embodiment are shown in FIG. 1 by a method of welding the side surface of a dimmed wire and a metal plate simulating a cap for a high-output fluorescent lamp. In the figure, 1 is a composite wire, 2 is a metal plate to be welded to the composite wire 1, 3 and 4 are a pair of first and second electrodes that press the composite wire 1 and the metal plate 2 from above and below, 5 6 is a pre-treatment power source that applies a pre-treatment voltage of high voltage and small current between the composite wire 1 and the first electrode 3; 6 is a switch inserted between the power source 5 and the first electrode 3; and 7 is a composite wire. A pretreatment power source for applying a pretreatment voltage of high voltage and small current between the wire 1 and the second electrode 4; 8 a switch inserted between the power source 7 and the metal plate 2; A third electrode (simulated at two points in the figure) is provided to apply the current of the pretreatment power supplies 5 and 7 to the composite wire 1, and 9 is a low voltage large current between the electrodes 3 and 4. 10 is a switch inserted between this power source 9 and the first electrode 3. As shown in FIG. 2, the composite wire 1 has a non-conductive coating 1b made of copper oxide formed on the surface of the composite wire 1a. Further, the metal plate 2 does not have a non-conductive coating.

Next, the welding process will be explained. First, as shown in FIGS. 1 and 2, a composite wire 1 and a metal plate 2 are superposed and then pressed between electrodes 3 and 4. Then, switch 6 for both pre-processing power supplies 5 and 7,
Insert 8. The pretreatment voltage is then supplied from the respective power supplies 5, 7 to the composite wire 1 via the third electrode 15, and is conducted to the respective power supplies 5, 7 via the first and second electrodes 3, 4. Then,
As shown in the third diagram, the first electrode 3 and the composite wire 1
between the composite wire 1a and the composite wire 1a and the metal plate 2
A high voltage is applied between them, and the non-conductive film 1b is locally destroyed by this voltage, and holes 1c are formed on both the first electrode 3 side and the metal plate 2 side. However, since the current for this pretreatment is small, the composite wire 1a is hardly melted. Therefore, switches 6 and 8 are turned off, and switch 10 of welding power source 9 is turned on. Then, since the insulation of the non-conductive coating 1b of the composite wire 1 has already been destroyed, the welding current flows from the first power source 3 → composite wire 1a → metal plate 2 → second electrode 4, The contact portion between the composite wire 1a and the metal plate 2 is melted by the heat, and when the current is cut off, it is cooled and solidified to form a welded portion 1d as shown in the fourth figure.

As described above, according to the present welding method, prior to welding, a pretreatment voltage of high voltage and small current is applied to destroy the non-conductive coating 1b on both the first electrode 3 side and the metal plate 2 side. Since the welding current is passed through, the voltage resistance of the contact part during welding is small and its value is almost constant, so the welding current actually passed is also almost constant, so there is no need to worry about excess or deficiency of welding current. Welding defects caused by this have almost completely disappeared. Moreover,
In the pretreatment, since the current is small, it simply destroys the non-conductive coating 1b, and no welding occurs, so there is no defect in the shape of the welded part, and there is no excess or deficiency in welding due to the insulating properties of the non-conductive coating 1b. will not occur.

In addition, in the present invention, the member to be welded is not limited to a wire body, but may also be a plate body, etc., and it is applicable to all of these members when at least one of these members has a non-conductive coating in the part through which welding current flows. .

Further, in the present invention, the pretreatment voltage may be a high frequency voltage. Furthermore, even if the welding power source is turned on at the same time as the pretreatment voltage is applied, and the welding current is allowed to flow after the non-conductive film is destroyed, the same effect as in the above embodiment can be obtained. be.

〔Effect of the invention〕

In the resistance welding method of the present invention, in the step of resistance welding a pair of welded members, at least one of which has a non-conductive coating, a third electrode is provided on the welded member having a non-conductive coating, and the third electrode is Electrode and above 1
A high voltage or high frequency voltage is applied between each pair of electrodes to destroy the non-conductive coating, and welding is carried out by passing a welding current through the current-carrying part, so the electrical resistance of the current-carrying part during welding is small. Therefore, the variation in welding current is small, and therefore welding defects caused by excess or deficiency of welding current are eliminated, making it possible to stably manufacture high-quality products.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the resistance welding method of the present invention, and FIGS. 2 to 4 are enlarged explanatory diagrams of essential parts similarly explaining the manufacturing method step by step. 1, 2... Member to be welded, 1b... Non-conductive coating, 1c... Hole, 3... First electrode, 4... Second
electrodes, 5, 7... pretreatment power source, 9... welding power source, 15... third power source.

Claims (1)

[Claims] 1. In the process of superimposing a pair of welded members, at least one of which has a non-conductive coating, between a pair of electrodes and applying current to resistance welding, a third electrode is applied to the welded member having the non-conductive coating. and applying a high voltage or high frequency voltage between the third electrode and each of the pair of electrodes to destroy the non-conductive film, and passing a welding current between the current-carrying parts to perform welding. A resistance welding method characterized by: