JPH0592275A - Resistance welding electrode - Google Patents

Abstract

(57) [Summary] [Object] To provide an electrode for resistance welding, which has a long life and is capable of improving continuous spotting property and excellent welding quality. [Structure] In a resistance welding electrode 1, a plurality of protrusions 3 each having a tip smaller than a base portion independently of each other at a tip portion 2 are higher in the central portion of the tip portion 2, that is, the protrusion 3a is the highest. Then, the protrusions 3b and 3c are formed in this order, and the valleys 4 are formed between the protrusions 3. At the center of the tip portion 2, a concave portion 5 is formed by the intersection of the valley portions 4 which are substantially V-shaped grooves between the protrusions 3a and 3a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode used for resistance welding of a metal plate such as an aluminum alloy plate.

[0002]

2. Description of the Related Art Conventionally, an electrode used for resistance welding of an aluminum alloy plate or the like generally has its tip end shaped into a convex spherical surface.

In the resistance welding, a portion of a metal plate (working member) to be welded is superposed and inserted between electrodes provided opposite to each other in a welding device, and the electrode is attached to the portion to be welded. This is a method in which power is supplied in a pressure-welded state, and the resistance of the metal plate causes the above-mentioned portion to generate heat, which causes welding, but when applied to a relatively soft material such as an aluminum alloy, it deforms around the welded part of the metal plate. And cracks may occur. Therefore, the electrode having the above shape is used to avoid the deformation and crack of the metal plate.

However, when the electrode having the above-mentioned shape is used, the electric current tends to be concentrated on a very small part of the surface of the electrode that abuts the metal plate at the time of welding. There is a problem in that the fused material between the electrode and the metal plate adheres, or conversely, the electrode remarkably wears and breaks, which shortens the life of the electrode. Further, when using the electrode of the shape, the fusion product adheres to the dent portion, sticking may occur, the nugget may not be formed in the center of the electrode, the desired welding quality is not obtained, Continuous hitting property is low and improvement is desired.

The cause of the above problems is considered as follows.

One of them is due to a non-uniform oxide film formed on the surface of a metal plate such as an aluminum alloy plate. That is, when trying to supply power by pressing the electrode against a metal plate having a non-uniform oxide film formed on its surface,
Since the metal oxide film generally acts as a resistor during energization, a current flows through the metal plate only through a portion of the oxide film having a weak resistance value, and the current concentrates at a portion of the oxide film having a weak electric resistance. As a result, the temperature is excessively increased in the portion where the current is concentrated, the aluminum alloy diffuses into the pressure surface of the electrode, and the electrode and the aluminum alloy are alloyed,
It is considered that as the number of hit points increases, an insulating material such as MgO or Al ₂ O ₃ adheres to cause sticking between the electrode and the metal plate.

Another idea is to bring the electrode and the metal plate into contact with each other via the microscopic projections present on either surface thereof. That is, when microscopically observing the surface of the electrode or the metal plate, there are minute protrusions.When the electrode is pressed against the metal plate, the electrode and the metal plate are contacted via the minute protrusion in the initial stage of welding. It In this situation,
Since the contact portion between the electrode and the metal plate is minute, a central load is applied to this portion and a large current is concentrated. As a result, it is considered that a fusion product between the electrode and the metal plate is generated and adheres to the electrode or the dent portion. Further, it is considered that since the central load is applied to the minute contact portion, the metal plate starts to be melted in the vicinity of the contact portion, and the energized area gradually expands to form a nugget. Considering in this way, it is explained that the nugget formed as described above is centered on the position of the minute protrusion, and therefore does not necessarily coincide with the center of the electrode.

In order to solve the above problem, an electrode has been proposed in which the surface of the welding electrode that abuts against the metal plate is processed so that the oxide film can be uniformly destroyed at the portion where the electrode abuts. .. According to such an electrode, when the electrode is pressed against a metal plate for welding, the oxide film is destroyed in the entire portion where the electrode contacts, and the portion where the electrode contacts the unoxidized portion of the metal plate increases. To do. As a result, it is possible to prevent the current from being uniformly supplied from a wide range on the electrode and locally concentrated, so that the life of the electrode can be expected to be extended and the welding quality can be improved.

As such an electrode, for example, Japanese Unexamined Patent Publication No.
Japanese Unexamined Patent Publication No. 8-159986 proposes an electrode in which a groove having a triangular or trapezoidal cross-sectional shape is formed in a concentric circle shape or a spiral shape composed of a plurality of annular grooves on a surface of the electrode that contacts the metal plate. In the electrode, the top of the portion sandwiched between the grooves forms an annular or spiral ridge with an acute angle. According to the description of the publication, by using an electrode in which the groove of the shape is formed on the surface contacting the metal plate, when the electrode is pressed against the metal plate for welding,
It is said that since the ridge portion destroys the oxide film on the surface of the metal plate, it is possible to increase a portion where the electrode comes into contact with an unoxidized portion of the metal plate, and welding can be advantageously performed.

However, in the electrode disclosed in the above-mentioned publication, the current load tends to concentrate in the electrode center portion among the grooves formed on the electrode surface shaped into a convex spherical surface during welding, It cannot be said to sufficiently solve the problems of the prior art.

Moreover, when the current concentrates on the center of the electrode shaped into a convex spherical surface, the product produced by the sticking of the electrode and the metal plate during welding adheres to the whole of this part, and the appearance of the work to be welded. There is an inconvenience that the quality deteriorates and the dispersion of the welding strength increases with the instability of the energization path.

Further, Japanese Patent Application Laid-Open No. 62-156085 proposes an electrode in which the surface of the electrode is shot-blasted to form irregularities. According to the description of the above publication, by forming irregularities on the surface of the electrode, the effective life of the electrode is extended, and it is possible to perform welding many times continuously with the same electrode. However, since the electrode disclosed in the above publication forms unevenness on the electrode surface by shot blasting, it is difficult to form protrusions of uniform size, and the unevenness formed is small, so the aluminum alloy plate When it is used for welding a metal plate such as the above, impurities at the time of welding are deposited in the recess within a short period of time, and sticking is likely to occur, and the useful life is not extended as expected.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in order to eliminate such inconvenience, and has a long life, excellent welding quality can be obtained, and durability and continuous spotting property are satisfied. An object is to provide an electrode for resistance welding.

[0014]

In order to achieve the above object, the resistance welding electrode of the present invention has a plurality of projections, which are independent from each other and whose tips are thinner than the base portion. The resistance welding electrode is characterized in that the center of the electrode tip portion is a concave portion, and the protrusion is formed so as to be higher toward a portion closer to the center of the electrode tip portion and lower toward the outer peripheral direction. To do.

[0015]

According to the resistance welding electrode of the present invention, when a portion to be welded of a work member such as an aluminum alloy plate is overlapped and inserted between the electrodes of the welding device, and the resistance welding electrode is pressure-welded to this portion. First, a plurality of protrusions formed near the center of the electrode tip destroys the oxide film and contacts the work member, and an electric current is supplied. The protrusion is
Since it is formed to be higher than the projection formed on the periphery of the electrode tip, it contacts the work member in the initial stage of welding. Further, since the projections are independent of each other and the tips thereof are thinner than the base, the oxide film on the surface of the work member is easily destroyed.

Therefore, according to the resistance welding electrode of the present invention, the electric current is distributed and supplied from a plurality of portions at the tip of the electrode, and it is possible to avoid one point concentration as in the conventional case.

At this time, since the center of the electrode tip is a recess and no protrusion is formed, no nugget is formed, and a plurality of nuggets corresponding to the protrusions formed near the center of the electrode tip are formed. Is formed. Next, when welding progresses, the temperature of the working member rises and softens due to resistance heat around the plurality of nuggets, and the electrode tip portion is further pressed into the inside of the working member to penetrate into the working member. The contact area with is increased. As the contact area between the electrode tip and the work member increases, the current-carrying area also increases, and the plurality of nuggets grow and fuse together at the center. As a result, a single circular nugget whose center coincides with the center of the electrode tip is formed. The single circular nugget continues to grow until the welding further progresses and the lower protrusions formed on the periphery of the electrode tip also come into contact with the work member.

As described above, the resistance welding electrode of the present invention has
According to this, the electrode does not come into contact with the work member at a minute portion.
A uniform contact with a wide pressing area. Therefore, the electrode is
Pressure to contact the material and supply from the electrode to the workpiece
The current distribution is approximately constant, and the depth direction and diameter are large
You can get a nugget of your taste. In addition, MgO, Al₂O ₃
Insulating material such as
The origin is always kept clean.

[0019]

Embodiment 1 Next, the resistance welding electrode of the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is an explanatory sectional view showing the tip of the resistance welding electrode of the present embodiment, FIG. 2 is a plan view showing the tip of the resistance welding electrode of the present embodiment, and FIGS. FIG. 7 is an explanatory sectional view showing a welding process by the resistance welding electrode of the embodiment, and FIG. 7 is an explanatory sectional view showing the shape of the resistance welding electrode of another embodiment.

In the resistance welding electrode 1 of this embodiment, as shown in FIG. 1, a plurality of protrusions 3 (3a, 3b, 3c), which are independent of each other and whose tip is thinner than the base, are provided at the tip. The height is higher (H ₁ ) toward the center of the portion 2, that is, the protrusion 3a is the highest, and then the protrusions 3b, 3c (H ₂ , H ₃ ) are formed so as to become lower in the outer circumferential direction. There are valleys 4 between them. A concave portion 5 is formed at the center of the tip portion 2 by the valley portion 4 between the protrusions 3a and 3a. A hole 6 for cooling water is provided inside the resistance welding electrode 1.

The tip of the projection 3 is formed so as to form a part of a convex spherical surface, and the surface connecting the tip of the projection 3 is a convex spherical surface of 100 to 150R as shown by the phantom line in FIG. Preferably, the convex spherical surface has a radius of 150R in this embodiment. In addition, the surface connecting the bottoms of the valleys 4 is shown in FIG.
Is a plane orthogonal to the central axis of the resistance welding electrode 1, as indicated by a virtual line.

As shown in FIG. 2, the protrusions 3 have a truncated pyramid shape and are divided by a plurality of valleys 4 formed so as to be orthogonal to each other and arranged in a lattice. There is. Then, the valley 4 is a set of the valley 4 in the Y direction.
The valley portions 4b in the a and X directions are formed so as to be orthogonal to each other at the center of the tip portion 2.

By forming the protrusions 3 and the valleys 4 as described above, the orthogonal portions of the valleys 4a and 4b become the recesses 5 at the center of the tip 2 and the protrusions 3a and 3 which are higher toward the center.
b, 3c are obtained. The four highest protrusions 3a are formed so as to surround the recess 5, and the protrusions 3b and 3c are formed around the protrusion 3a.
Is formed.

In this embodiment, the valley portion 4 is formed by rounding the bottom portion. By forming the bottom of the valley 4 in such a shape, when a fusion product of the resistance welding electrode 1 and the metal plate to be welded is generated at the bottom of the valley 4, the fusion product is rounded. Since it adheres to the bottom of the formed valley portion 4, this fused substance can be easily removed. In addition, it effectively works to prevent sticking.

The resistance welding electrode 1 of this embodiment is, for example,
A powdery or granular material of an electrode material is filled in an electrode forming die in which a plurality of concave portions having a substantially V-shaped cross section are regularly arranged, and the filled powdery or granular material is pressure-molded to be independently formed from each other. Forming step for obtaining a preformed body of an electrode in which a plurality of protrusions whose tips are thinner than the base portion are formed, and firing step for firing the preformed body obtained in the above step to obtain a sintered formed body of the electrode Or a method of filling the electrode forming die with the powder particles of the electrode material and press-molding the filled powder particles to form a convex spherical surface with a substantially smooth end. Preforming step for obtaining a preformed body of the electrode, a firing step for firing the preformed body obtained in the above step to obtain a sintered body of the electrode, and a projection having a tip thinner than its base portion. Sintering the electrode obtained in the above step with a shaping tool that applies to at least one surface of the electrode It can be advantageously manufactured by a manufacturing method including a molding step of molding a plurality of protrusions whose tips are thinner than the base independently of each other by pressing on the shaping surface of the electrode sintered body. ..

Next, the operation of the resistance welding electrode 1 of this embodiment in resistance welding will be described by taking resistance welding of an aluminum alloy plate as an example.

When performing resistance welding using the resistance welding electrode 1 of the present embodiment, as shown in FIG. 3, the portions of the aluminum alloy plates 31a and 31b to be welded are overlapped with each other, and the electrodes of the welding apparatus are Insert in between. At this time, the resistance welding electrode 1 is used for the plus side electrode, and the electrode 32 whose tip is shaped into a convex spherical surface is used for the minus side. No protrusion having the shape according to the present invention is formed at the tip of the electrode 32. A hole 37 for cooling water is provided inside the electrode 32. By doing this,
On the aluminum alloy plate 31b, to which the negative electrode 32 is pressed, a smooth welding mark on the surface is obtained.

When the electrodes 1 and 32 are arranged as described above and pressed against the welded portions of the aluminum alloy plates 31a and 31b, first, the highest protrusion 3a of the electrode 1 is an oxide film on the surface of the aluminum alloy plate 31a (see FIG. It pierces through (not shown) and comes into contact with the unoxidized portion of the aluminum alloy plate 31a. By energizing in this state, the nugget 33 is formed at the portion corresponding to the protrusion 3a on the boundary surface between the aluminum alloy plates 31a and 31b. As described above, the protrusion 3a is
Since the nugget 33 is formed at four places so as to surround the center recess 5 of the tip portion 2, the nugget 33 is also formed at four places surrounding the center of the welded part.

As the welding proceeds, the aluminum alloy plates 31a and 31b around the nugget 33 are softened by resistance heat, so that the electrode 1 and the electrode 32, which are in pressure contact with each other, are deeper and easier to reach the unoxidized portion of the aluminum alloy plate 31a. invade. Then, as shown in FIG. 4, the protrusion 3b having a height lower than that of the protrusion 3a comes into contact with the unoxidized portion of the aluminum alloy plate 31a. Nugget 3 at this stage
While a plurality of new nuggets 34 are newly formed at the portions around the circumference 3 corresponding to the protrusions 3b, the nuggets 33 grow and fuse together at the center of the weld.

As the welding further progresses, the contact area between the electrode 1 and the unoxidized portion of the aluminum alloy plate 31a increases, and the current-carrying area also increases accordingly. And FIG.
As shown in (3), the nuggets 33 and 34 grow and the nugget 34 fused to the nugget 33 fused at the center of the welded portion also forms a single integral circular nugget 35.

The nugget 35 is the lowest protrusion 3 of the electrode 1.
The growth is continued until c comes into contact with the unoxidized part of the aluminum alloy plate 31a, and as shown in FIG. 6, a nugget 36 whose center coincides with the center of the tip 2 of the electrode 1 is formed.

There was little damage to the electrode 1 after continuous 600 dots, and an effective nugget 36 having a predetermined depth direction and a predetermined diameter after 800 continuous dots was obtained.

In the present embodiment, the shape of the resistance welding electrode 1 is described as a cylindrical shape, but the shape of the resistance welding electrode 1 can be appropriately selected according to the application.
There are various shapes as shown in FIG. 7.

FIG. 7 (a) shows an example in which the tip portion 2 of the resistance welding electrode 1 in the shape of an oblique cylinder is formed in the shape according to the present invention. FIG. 7B shows an example in which the tip portion 2 of the resistance welding electrode 1 in which the tip of the cylindrical main body 71 is a slightly thin cylinder is formed in the shape according to the present invention. FIG. 7C is an example in which a cylindrical resistance welding electrode 1 having the same diameter is bent and formed at the tip of a cylindrical body 71, and the tip 2 is formed in the shape according to the present invention.

In the present embodiment, the protrusions 3 are formed in the shape of a quadrangular pyramid and are arranged in a grid pattern. However, the protrusions 3 are independent of each other, and the tips of the protrusions 3 are thinner than the base. Alternatively, any shape such as a truncated cone shape may be used.

Further, in the present embodiment, the concave portion 5 is formed as an intersection of the valley portions 4, but it is sufficient that the concave portion 5 is formed so that the center of the tip portion 2 is lower than the other portions. You don't have to.

[0038]

As is apparent from the above description, according to the resistance welding electrode of the present invention, when the resistance welding electrode is pressure-welded to the portion to be welded of the work member such as the aluminum alloy plate, the electrode tip is first contacted. The oxide film is destroyed by the plurality of high protrusions formed near the center of the portion, and as the welding progresses, the plurality of protrusions formed on the tip of the electrode come into contact with the work member in order from the highest protrusion. Therefore, the welding current is surely distributed and supplied from a plurality of portions at the tip of the electrode, and it is possible to avoid one point concentration, so that the life of the electrode can be extended. Moreover, since the insulating material such as MgO and Al ₂ O ₃ is deposited in the groove portion of the electrode tip portion, the protrusion can prevent alloying of the electrode tip portion which is always kept clean.

According to the resistance welding electrode of the present invention,
A plurality of protrusions formed on the tip of the electrode form a nugget at a position corresponding to each protrusion of the work member,
The nuggets grow as the welding progresses and fuse together at the center of the weld to form a single circular nugget. Therefore, it is possible to obtain a nugget whose center coincides with the center of the tip portion of the electrode, and of course it is possible to prevent scattering and scattering.

Further, according to the resistance welding electrode of the present invention, as described above, the electrode uniformly abuts on the work member in a large area without abutting on the work member at a minute portion. Further, the current path supplied from the electrode to the work member becomes stable and becomes constant, so that a nugget having a certain amount of penetration and diameter and no variation can be obtained.

Therefore, according to the resistance welding electrode of the present invention, the local load is small, the life of the electrode is extended, and excellent welding quality can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory sectional view showing an electrode for resistance welding according to an embodiment of the present invention.

FIG. 2 is a plan view showing an electrode for resistance welding according to an embodiment of the present invention.

FIG. 3 is an explanatory sectional view showing a welding process by the resistance welding electrode shown in FIG.

FIG. 4 is an explanatory sectional view showing a welding process by the resistance welding electrode shown in FIG.

5 is an explanatory cross-sectional view showing a welding process by the resistance welding electrode shown in FIG.

6 is an explanatory cross-sectional view showing a welding process using the resistance welding electrode shown in FIG.

FIG. 7 is an explanatory sectional view showing the shape of an electrode for resistance welding of another embodiment according to the present invention.

[Explanation of symbols]

1 ... Electrode for resistance welding, 2 ... Tip part, 3 ... Protrusion, 4
... valleys, 5 ... recesses, 33, 34, 35, 36 ... nuggets.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomohiko Ito 1-10-1 Shin-Sayama, Sayama-shi, Saitama Prefecture Within Honda Engineering Co., Ltd. (72) Inventor Yukihiro Yaguchi 1-10-1 Shin-Sayama, Sayama-shi, Saitama Within Da Engineering Co., Ltd.

Claims (1)

[Claims] 1. A resistance welding electrode in which a plurality of protrusions are formed at the tip of an electrode independently of each other and whose tip is thinner than that of a base, and the center of the tip of the electrode is a recess. The electrode for resistance welding is characterized in that the protrusion is formed so as to be higher in a portion closer to the center of the electrode tip portion and lower in the outer peripheral direction.