JPS5944949B2 - Automatic welding method for laminated steel plates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for automatically welding laminated iron plates such as silicon steel plates used in small electric motors, transformers, ballasts for discharge lamps, and the like.

Iron cores used in small electromagnetic induction devices such as small electric motors and transformers are manufactured by laminating a required number of silicon steel plates and melt-welding the ends in the lamination direction.

For this welding, a general arc welding method using a consumable electrode is also used, but in the case of a small core, a TIG welding method using a non-consumable electrode is generally used. FIG. 1 shows the situation at this time. In the figure, 1 is a laminated iron plate to be welded, which is held between copper blocks 2 and 2' arranged above and below. 3 is a welding torch, 4 is a welding bead that has already been welded, and 5 is a welding power source.
In the case of IG welding, a welding power source with direct current drooping characteristics is usually used.

An insulating layer is provided on both sides of the laminated iron plate 1, so that the welding current flows from the copper block 2 through the welding bead 4 to the welding torch 3. Since the current path is bent at right angles in this way, the arc 6 is pushed upward as shown in the figure by the magnetic flux generated by the current flowing through the welding torch 3 and the welding bead 4. When there is only one welding torch, this force is constant and stable, so by selecting welding conditions that take this pushing-up force into consideration, sufficiently stable welding can be performed. However, there are usually several welds on one workpiece, and welding them one by one results in low productivity and high costs. A method is used in which a torch is installed and welding is performed at the same time. However, as mentioned above, the laminated iron plates used in electromagnetic induction equipment have insulating films on both sides, so when arc welding is performed simultaneously using multiple welding torches, the current path changes complicatedly, causing the arcs to interact with each other. They interfere with each other and become unstable, resulting in welding defects such as uneven beads and poor penetration. Figure 2 explains the situation at this time, and in the figure 3a is the first
The welding torch 3b is a second welding torch. These torches are shown by selecting adjacent welding torches from a plurality of welding torches, and other torches are omitted. Each welding torch first generates an arc between it and the copper block 2,
This arc is transferred to the laminated iron plate 1 and advances upward in the figure at the same speed. 4a and 4b are weld beads welded by welding torches 3a and 3b, respectively, and 5a
and 5b are welding power sources for supplying power to the welding torches 3a and 3b, respectively.

Let us now consider a case where a welding arc is generated between the iron plate 1a and the welding peas 4a and 4b have also reached the iron plate 1a.

In such a state, the welding current is applied to each weld bead 4a.
and 4b, the currents from the welding torches 3a and 3b are balanced, and the current flowing through the iron plate 1 is apparently close to zero and does not fluctuate, so the arc is stable. Molten pools are formed at A and B of the laminated iron plate 1 by the arc of the welding torches 3a and 3b,
This gradually grows and when it comes into contact with the next upper iron plate, the arc also moves to the upper iron plate and welding continues.
In this case, even if the welding conditions of the welding torches 3a and 3b are set to be exactly the same, the molten pool formed by the welding torches 3a and 3b will almost never reach the next upper steel plate at the same time. There will be some time difference. As an example, consider a case where the molten pool produced by the welding torch 3b comes into contact with the upper plate earlier, reaches point C of the iron plate 1b (7), and the arc also moves. At this time, the molten pool short-circuits the end B of the iron plate 1a and the end C of the iron plate 1b. As a result, the arc of the welding torch 3a can also be discharged to the portion D, even though the molten pool has not yet reached the end D of the iron plate 1b. At this time, part of the current flowing from the welding power source 5a passes through the copper block 2 and the welding pin 4, and flows from the iron plate 1af) A end to the torch 3a, and the rest flows from the A point into the iron plate 1a, which has an insulating layer on the empty surface. , passes through point B, the molten pool formed by the welding torch 3b, point C, and the iron plate 1b, passes through point D, and is branched off to the welding torch 3b. As a result, the welding current of this welding torch 3b and the above-mentioned branched portion of the welding current of the welding torch 3a flow into the molten pool on the side of the welding torch 3b, and the arc of the welding torch 3b is caused by the welding current of this torch itself. The electric current generated by the received electromagnetic force and the shunt from the welding torch 3a. It will be affected by the magnetic force at the same time, and will be pushed up greatly. Moreover, since the current branched from the welding torch 3a becomes approximately zero at the moment the molten pool of the welding torch 3a reaches point D, the arc of the welding torch 3b undergoes rapid changes and becomes extremely unstable. In exactly the same way, the above-mentioned phenomenon may occur in the welding torch 3a, and each is adversely affected by the other's arc.Such a phenomenon occurs at each boundary of the laminated steel plate, and at each boundary, Every time a sudden change in the current path occurs due to the transition of the trailing arc, the electromagnetic force acting on the preceding arc will suddenly change, making welding extremely unstable and affecting the welding result. This phenomenon occurs when the welding current is increased by closely matching the position and tip shape of the welding electrode.
This can be reduced to some extent by enlarging the molten pool, but since the objects to be welded are punched thin plates, stacking a large number of them may result in uneven plate thickness, burrs during punching, and plate distortion. Therefore, it is unavoidable that the stacking heights differ partially, and no matter how strictly each torch is set, it is impossible to always move the arc generation point to the same plate at the same time during the entire welding process. The instability phenomenon described above cannot be avoided. The present invention prevents the arcs of other torches from being subjected to sudden changes in electromagnetic force when the arc of one welding torch shifts by separating the welding torches by a certain amount or more in the lamination direction of the laminated iron plates. This paper proposes an automatic welding method for laminated steel plates that stabilizes the arc.

FIG. 3 explains the welding method of the present invention. In the present invention, the welding torch 3b is installed so as to face the end E of the laminated iron plate a certain amount above the welding torch, and this state is maintained. Arc welding is performed while moving the welding torches 3a and 3b upward at approximately the same speed.

In this state, the molten pool by the welding torch 3a is now at point A of the iron plate 1af), and the arc of the welding torch 3a has moved from point A to point D (at point D, the iron plate 1a and 1b are short-circuited by the bead 4b). The arc can shift because there is)
Consider the case. In this case, the welding current of the welding torch 3a is changed from point A of the iron plate 1af) to the iron plate 1a, . Point B, bead 4b. The welding torch 3 passes through point C and the path of the iron plate 1b, and the bead 4bf) between B and C.
In addition to the welding current b, the welding current of torch 3a also flows, and the generated magnetic field increases rapidly.
Since point b is sufficiently far from point E where the welding arc is generated, the electromagnetic force acting on the arc column of torch 3b hardly changes. Therefore, the torch 3b is hardly affected by the shift of the arc generation point of the torch 3a and is stable. On the other hand, the welding torch 3a has a bead 4 at one end of the opposing iron plate.
The arc of torch 3b is already short-circuited by point D, and even if the arc of torch 3b moves to the iron plate above, it is open above point D and the path of the welding current of torch 3b does not change. The electromagnetic force acting on the arc column does not change, and this arc is also stable. It is desirable that the distance between the welding torches 3a and 3b in the welding line direction be as large as possible compared to variations in the thickness of the steel plates 1 in the stacking direction, the size of the molten pool, or the size of the arc spot. Since the welding time becomes longer by the amount corresponding to , it is appropriate for general TIG welding to be several times to about 10 mm. Furthermore, as is clear from the above-mentioned cause of arc instability and the purpose of the present invention to solve this problem, instability of these arcs is caused by short circuits where no arc occurs nearby (in the case of Fig. 3, C- When welding using three or more welding torches at the same time, only one of the torches should be used in advance, and each of the remaining welding torches should be welded by at least one of the adjacent welding torches. It can be seen that it is only necessary to arrange them at positions delayed in the stacking direction by a distance that does not interfere with each other.

Figure 4 shows the case of welding the stator of an electric motor using eight torches. Figure A is a plan view, and Figure B is a developed view showing the positional relationship of each welding torch in the stacking direction. be. In the same figure, the torch is ahead of the other seven torches, the torch is placed behind the torch by a distance l, and the torch song is placed as ha, two, and ho, and the torch is placed in a position that is a distance l ahead of the torch. be. Therefore, as shown in Figure 4B, the torches RO and 1, C and BO and 2 are at the same position, but there is a short circuit near each torch due to the bead welded by the adjacent torch. Since there is a curved portion, the relationship shown in FIG. 3 holds for any two adjacent torch combinations, and the arcs do not interfere with each other. Moreover, by arranging the torch as shown in FIG. 4B, the distance at which the torch is arranged can be shortened, and the total welding time can be shortened compared to the case where the torch is uniformly delayed by a fixed distance. If the distance d between the circumferential welding torches is sufficient, the specific resistance of the iron plate is large, and the current flowing inside is small, each torch may be moved back and forth alternately as shown in FIG. 4C.

As described above, according to the present invention, since the welding torches are spaced a certain distance apart in the stacking direction, the welding arc can be stabilized and the bead shape and penetration can be improved, and a large number of electrodes can be connected simultaneously. Since it can be used for welding, it has the advantage of improving welding work efficiency and obtaining good welding results.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the case where laminated steel plates are welded with a single welding torch, Fig. 2 is an explanatory diagram showing the case where multiple welding torches are used, and Fig. 3 is an explanatory diagram showing the automatic welding method of the present invention. The explanatory drawings and FIGS. 4A and 4B are a plan view and a developed view showing an example of arrangement of welding torches, respectively, and FIG. 4C is a developed view showing another example of arrangement of welding torches. 1, 1a, 1b... laminated iron plate, 3, 3a, 3b...
Welding torch, 4, 4a, 4b... welding bead, 5, 5
a, 5b... Welding power source, 6... Arc.

Claims (1)

[Claims] 1. A method of fixing the ends of laminated iron plates by arc welding using a plurality of welding torches, in which each welding torch is fixed a certain distance from another adjacent welding torch in the lamination direction of the laminated iron plates. An automatic welding method for laminated steel plates, which is characterized by performing welding while being placed at a remote location. 2. One welding torch among the plurality of welding torches is placed at the most leading position, and each of the other welding torches is delayed by a certain distance in the stacking direction from at least one of the adjacent welding torches. 2. The automatic welding method for laminated iron plates according to claim 1, wherein the automatic welding method comprises: