JPH0317592B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Prior Art and Objects of the Invention) The present invention relates to an improvement in a method for welding pipes by spot welding.

Conventionally, brazing welding, arc welding, etc. have been used to weld pipes, but in the case of brazing welding, there are many problems such as degreasing before welding and cleaning of wax after welding. There is a problem in that it requires expensive materials such as wax material and flux material, and in the case of arc welding, if the pipe material is thin, it has the disadvantage that holes are easily formed by the arc heat.

In view of this situation, research has been conducted into welding pipes by spot welding using electric heating resistance, but when spot welding is used,
As shown in Figures 1a and 1b, the outer periphery of the pipe is brought into contact with an electrode divided into two parts, and both electrodes are brought into contact with each other, and a power supply terminal is provided on one side of the pipe, and The electrode 12 is also attached to the plate to be welded, and the power supply terminal of the electrode 11 and the power supply terminal of the electrode 12 are connected to the output terminal 21 of one transformer,
22, or as shown in FIGS. 2a and 2b, two divided electrodes can be brought into contact with the outer circumferential surface of the pipe, and both electrodes can be used in a state where they are not in contact with each other, and the electrode 11 can be connected to is provided with a power supply terminal 111, which is connected to the output terminal 21 on the transformer side, and the output terminal 121 of the electrode 12 on the side of the plate or the like to be welded to the pipe 3 is used in combination with the other output terminal 22 of the transformer. .

However, in these spot welding methods,
In the method shown in Figures 1a and 1b, since the electrode does not contact the entire circumference of the pipe 3, the current concentrates in the area near the power supply terminal 111 inside the pipe 3 (for example, if the power supply terminal 111 is , the current is 1st a, b
As shown in FIGS. 2A and 2B, conduction occurs directly to the electrode 12 side through the electrode 11 and a portion of the pipe 3 near the inner electrode 11. Conversely, when the power supply terminal 111 is Continuity is concentrated through the electrode 11 and a portion of the pipe 3 near the internal power supply terminal 111. ), it was not possible to distribute the current uniformly in a ring over the cross section of the pipe.

In addition, in the method shown in FIGS. 2a and 2b, the power supply terminal 1
11 on both sides, the current distribution is somewhat improved compared to the cases shown in Figures 1a and 1b, but the current is still uniformly distributed in a ring shape. are far from each other, and based on the fact that the distances between the two power supply terminals 111 and the output terminals 21 of the transformer are different, the impedances between the output terminals of the transformer and each power supply terminal 111 are different. The values of the current supplied to the pipes were different, which prevented a uniform distribution of the current over the ring-shaped cross section of the pipe 3.

Note that the impedance between the output terminal 21 and each power supply terminal 111 differs due to the difference in distance between the two power supply terminals 111 and the output terminal 21 of the transformer. A large current flows between the power supply terminal 111 and the power supply terminal 111 due to the voltage drop of the transformer, and the difference in the distance between the two terminals causes a difference in electrical resistance, stray inductance, stray capacitance, etc.

The present invention aims to overcome these drawbacks of the prior art in pipe welding using spot welding.

(Structure of the Invention) The present invention includes a plurality of electrodes that abut the entire or almost the entire outer circumference of a pipe, and connect a power supply terminal for the entire electrode to the center point of the cross section of the pipe.
They are arranged at equal angles and are arranged so that the impedance from the output terminal of the transformer to each power supply terminal is equal or almost equal.

Each embodiment shown in the drawings will be explained below.

Figures 3a and 3b show an embodiment in which a plurality of electrodes are used in contact with each other and in contact with the entire outer circumference of the pipe.

Of these, Fig. 3a shows an embodiment in which a power supply terminal is provided at the center position of the cross section of each electrode, and thereby the power supply terminal is arranged at equiangular positions with respect to the center point of the cross section of the pipe. Fig. 3b shows an embodiment in which each power supply terminal is not located at the center position of the cross section of each electrode, but is arranged at equiangular positions with respect to the center point of the pipe as a whole.

Figures 4a and 4b show an embodiment in which a plurality of electrodes are brought into contact with almost the entire outer circumference of the pipe while remaining divided, and of these, Figure 4a shows the electrodes on the outer surface of the electrode. 1 power supply terminal in each horizontal center position
FIG. 4b shows an embodiment in which one power supply terminal is provided at symmetrical positions with respect to the center position.

On the other hand, in the present invention, it is required that the impedance from the output terminal 21 of the transformer to each power supply terminal 111 is arranged to be equal or almost equal. The distance between the terminal 21 and the power supply terminal 111 is designed to be equal, and the same cord is used, or the output terminal 21
Even if the distances between the power supply terminal and the power supply terminal are not equal, and the cords are not the same, the impedance between the two may be measured and then designed to be equal.

In the above embodiment, for each power supply terminal 111,
While arranging the corresponding transformers 2 and connecting the output terminals 21 of the transformers to the power supply terminals 111,
The other output terminal 22 is connected to the power supply terminal 121 on the lower electrode 12 side to be welded to the pipe.

However, the configuration of the present invention does not necessarily require that there be a corresponding transformer 2 for each power supply terminal 111, and as in the embodiment shown in FIG. It is also possible to design and connect the power supply terminals 111 so that the impedances between them are equal.

(Effect of the invention) In the method of the present invention shown in the above embodiments, the electrode 1
Since the electrode 11 is in contact with the entire circumference or almost the entire circumference of the pipe 3, the current is distributed from the electrode 11 over the entire cross section of the pipe. Even if a large amount of current flows in the area near the power supply terminal 111 and only a small amount flows in the part far from the power supply terminal 111, by increasing the number of power supply terminals arranged at equal angles, the current can be reduced. It is possible to approximate the distribution state to a state in which the power supply terminals are almost uniformly distributed in a ring shape across the cross section of the pipe (in addition, "arranging the power supply terminals at equal angles" in the present application refers to the above-mentioned As long as the current is uniformly distributed across the cross section of the pipe, it is not necessarily necessary that the angle be mathematically strictly "equal angle", and even in the case of "almost equal angle". included.).

In addition, as shown in Figures 3a and 4b and Figures 4a and 4b, when arranging three power supply terminals 111 or a multiple thereof, three-phase alternating current is used and the power supply terminals 111 are connected to the plate 4 to be welded to the pipe. It is also possible to perform spot welding by forming a Y connection in which the power supply terminal 121 of the contacting electrode 12 is the center and the power supply terminal 111 is a three-terminal terminal.

Furthermore, in the present invention, since the power supply terminal 111 and the output terminal 21 of the transformer are equidistant, the magnitude of the current may differ depending on the power supply terminal, as in the prior art shown in FIGS. 2a and 2b. do not have.

Furthermore, it is extremely convenient because it avoids the drawbacks of the aforementioned brazing welding and arc welding, and also allows pipes to be welded evenly and uniformly in a short time.

[Brief explanation of the drawing]

Figures 1a and 1b: A cross-sectional view and a vertical cross-sectional view of a pipe welding method using conventional spot welding in which a power supply terminal is provided on the outside of a divided electrode. Second
Figures a and 2b: A cross-sectional view and a vertical cross-sectional view of a pipe welding method using conventional spot welding in which power supply terminals are provided on both sides of a divided electrode (Fig. 1a,
The distributions in FIG. 1b, FIG. 2a, and FIG. 2b show a state in which the current conducts in a state where the current is unevenly distributed in the vicinity of the electrode. ) Figures 3a and 3b: cross sections showing embodiments of the present invention in which a plurality of electrodes are in contact with each other; Figures 4a and 4b: a cross-sectional view of an embodiment of the present invention in which a plurality of electrodes are not brought into contact with each other; 1 shows a cross-sectional view of an embodiment of the invention used in a divided state; FIG. FIG. 5: A cross-sectional view showing an embodiment of the present invention in which two power supply terminals are connected to one transformer. 11, 12... Electrode, 111, 121... Power supply terminal, 2... Transformer, 21, 22... Output terminal of transformer, 3... Pipe, 4... Plate to be welded to the pipe.

Claims (1)

[Scope of Claims] 1. A plurality of electrodes are in contact with the entire outer circumference or almost the entire circumference of the pipe, and the power supply terminals of the electrodes are arranged at equal angles with respect to the center point of the cross section of the pipe, and An improved pipe welding method characterized in that the impedance from the output terminal of the transformer to each power supply terminal is arranged so as to be equal or almost equal. 2. The improved pipe welding method according to claim 1, wherein the electrodes are brought into contact with each other and are brought into contact with the entire outer circumference of the pipe. 3. The electrodes are separated and contact almost the entire outer circumference of the pipe, and the power supply terminals of each electrode are equal in number and arranged at the center position or symmetrically with this in the cross section of each electrode. A method for welding a plate and a pipe according to claim 1. 4 Claim 1 characterized in that one transformer is arranged for each power supply terminal.
Method of welding the improved pipe described. 5. The improved pipe welding method according to claim 1, wherein one transformer is arranged for two power supply terminals.