JP2539456B2 - Spot welding method - Google Patents

Description

The present invention relates to a spot welding method.

[Conventional technology]

Spot welding is a welding method in which a body to be welded is set between electrodes and a predetermined pressure is applied and a large current is instantaneously supplied to locally heat and fuse the bodies to be welded to each other. .

[Problems to be solved by the invention]

However, the welding method utilizing the contact resistance between the objects to be welded and the concentrated resistance causes the welding to be performed between the objects to be welded, and at the same time, the pressure is applied to the electrodes that should not be affected,
Since the electrode and the object to be welded are also heated and pressed, the electrode is naturally consumed and deformed.

If such a worn or deformed electrode is continuously used, the pressing force and the supply of electric current become unstable, and the welding strength decreases and the welding state varies. Therefore, in order to maintain the defined quality, there is no problem if the electrodes are replaced before they are consumed or deformed, but the prediction is extremely difficult.

Therefore, a method has been considered in which the welding current and welding pressure are sequentially increased for a certain period of time or for each certain number of welding points according to the amount of electrode wear, but the amount of electrode wear and deformation are not constant. It is difficult to adjust the current and pressure, and there are many practical problems.

That is, if the welding conditions of the object to be welded are always constant, it can be controlled by the number of welding points or the time, but in reality, the surface condition of the object to be welded, such as the presence of an oxide film, residual oils and fats, or the inclusion of foreign matter. As a result, contact resistance may change, and the electrode life may be reached by welding several points.

However, if the number of welding points and the time are limited to a small number in consideration of maintaining the quality and the electrodes are constantly replaced, there is a problem that the production cost increases.

[Means for solving problems]

The present invention is a spot welding method in which a body to be welded is set between electrodes to give a predetermined pressure and a large current is momentarily supplied to locally join the bodies to be welded, one or both The electrode is shaped like a band, and a Ag or Ag alloy layer is formed on part or all of the surface of this band-shaped electrode, and it is moved intermittently or continuously to weld the object to be welded continuously. This is the spot welding method.

[Action]

The strip-shaped electrode is moved intermittently or continuously, the welding target is set between the strip-shaped electrode and the other electrode, and pressure is applied by both electrodes to flow an electric current to weld the welding target. Next, the pressing force is released to feed the strip electrode for a predetermined length to prepare for the next welding, which does not require a precise manufacturing process of the electrode and can eliminate the frequent replacement work of the electrode.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a side view of the entire apparatus, FIG. 2 is a perspective view of one body to be welded, FIG. 3 is a side view of the other body to be welded, FIG. 4 is a side view of an upper electrode, and FIG. Partial perspective view of electrode, 6th
The figure is a front view showing the set state of the object to be welded, and in the figure, 1 is a strip electrode, for example Cu or 0.3% Cr-Cu alloy, which is partially formed in the longitudinal central portion of this surface. Alternatively, the Ag or Ag alloy layer 1a is formed on the entire surface, and is intermittently or continuously taken out from the delivery spool 2 and taken up by the take-up spool 3, and is used as an electrode at the welded portion therebetween. The feeding of the strip-shaped electrode 1 is performed by the electrode feeding roll 4, the winding spool 3 or the like or other appropriate means.

Reference numeral 5 is a welding head, and in this embodiment, the upper electrode 6 is an electrode similar to the conventional one, which is made of, for example, 0.5% Cr-Cu alloy.

Reference numeral 7 is a clamp for the strip-shaped electrode 1, which fixes the sent strip-shaped electrode 1 at a fixed position.

8 is one example of the welded body, 4.5% Ti-Cu alloy spring material, 9 is an example of the other welded body, Ag and 70
% Cu-Ni alloy clad contact with projection.

The above-described objects to be welded 8 and 9 are arranged between the upper electrode 6 and the strip electrode 1 as shown in FIG. 6, and welding is performed under the conditions of a pressing force of 30 kg and a peak current of about 4000 A. It was moved every 1 point welding.

The welding strength of the thus-welded body is shown in the graph of FIG. 7 in comparison with that of the conventional body.

In the conventional method, a 0.5Cr-Cu alloy electrode was used and welding was performed under the conditions of a pressing force of 30 kg and a peak current of about 5000A.
As a comparison method, 10 pieces were sampled for every 100 points of welding and the welding strength was measured.

As you can see from this graph, according to the conventional method,
The initial average welding strength of 32 kg started to drop after 300 points, and decreased to 28 kg at 400 points and 22 kg at 500 points. Therefore, this conventional method requires replacement of the electrodes at the time of 300 points.

However, according to the present invention, the initial average welding strength is 32 kg.
Has been maintained for over 1500 points, and no electrode replacement is necessary.

The surface of the strip electrode 1 may be flat as shown in FIG. 5, but if a ridge is formed at the center of the surface in the longitudinal direction as shown in FIG. 9, the welding conditions will be stable and a better result will be obtained. can get.

In the above example, the material contacting the upper electrode was a pure Ag contact with a small contact resistance, so only the fixed electrode was used on the upper part. However, when using a material other than pure Ag having a high resistance, As shown, the upper electrode may be a strip electrode.

Although the two strip electrodes are orthogonal to each other in FIG. 8, they may have a structure in which they can be adjusted in the same direction or at an appropriate angle depending on the structure for supplying the welding target.

〔The invention's effect〕

According to the present invention described in detail above, one or both of the electrodes is a strip electrode, and an Ag or Ag alloy layer is formed on a part or the entire surface of this strip electrode, and intermittently or continuously moved to perform welding. By doing so, a new electrode surface can always be obtained and the desired welding strength can be maintained continuously, stable welding can be continuously obtained, and defective products do not occur and inspection It also results in lower costs due to less need.

Further, the strip electrode can be manufactured at a very low cost because it does not require high-precision molding processing unlike the conventional electrode.
Even if it is used continuously, the cost does not become high, and since the electrodes are not replaced, the processing time can be shortened.

Furthermore, by forming the Ag or Ag alloy layer on a part or the whole surface of the strip electrode, the peak current can be set low, and more reliable and stable welding can be continued.

[Brief description of drawings]

FIG. 1 is a side view of the entire apparatus showing a first embodiment of the present invention,
FIG. 2 is a perspective view of one body to be welded, FIG. 3 is a side view of the other body to be welded, FIG. 4 is a side view of an upper electrode, FIG. 5 is a partial perspective view of a strip electrode, and FIG. FIG. 7 is a front view showing a set state of the object to be welded, FIG. 7 is a graph showing welding strength, FIG. 8 is a plan view showing a second embodiment, and FIG. 9 is a view showing another embodiment of the strip electrode. FIG. 1 …… Strip electrode 1a …… Ag or Ag alloy layer 2 …… Sending spool 3 …… Winding spool 5 …… Welding head

Claims (2)

(57) [Claims] 1. A spot welding method in which a body to be welded is set between electrodes and a predetermined pressure is applied, and a large current is instantaneously supplied to locally join the bodies to be welded. Both electrodes are strip-shaped, and Ag or Ag alloy layer is formed on a part or the whole surface of this strip-shaped electrode and intermittently or continuously moved to continuously weld the work piece. Characteristic spot welding method. 2. A spot welding method according to claim 1, wherein a ridge is formed on the surface of the strip electrode.