JP7377733B2 - Electroslag welding method and magnetic field application device for electroslag welding - Google Patents

Description

The present invention relates to an electroslag welding method and a magnetic field application device for electroslag welding.

A magnetic stir welding method is known in which a magnetic field is applied to the molten pool in arc welding, and the molten metal is welded while being stirred by the magnetic force in the rotational direction caused by the magnetic field and the welding current (for example, Patent Document 1, (see 2). In Patent Documents 1 and 2, a magnetic coil is arranged to surround a welding torch.

Japanese Unexamined Patent Publication No. 4-190976 Japanese Patent Application Publication No. 8-318370

By the way, electroslag welding differs from arc welding in that a welding wire carrying a current of several hundred amperes is supplied to molten slag, which is a molten electrolyte, and the Joule heat generated within the molten slag causes the welding wire to bond to the base metal. This is a method of welding while melting. The welding direction is vertical, and welding progresses from bottom to top. Additionally, the groove in the base material is covered with a water-cooled copper plate to prevent molten slag and molten metal from spilling. In electroslag welding, the front, rear, left and right sides of the molten pool are covered with base metal and water-cooled copper plates, and the top and bottom of the molten pool are covered with already welded parts and molten slag. Therefore, even if a coil is placed in the torch part that supplies the welding wire as in arc welding, not only is it impossible to apply an effective magnetic field to the molten pool due to the presence of molten slag, but the space in the groove is narrow in the first place. , it is also not possible to place a coil.

An object of the present invention is to apply a magnetic field to a molten pool in electroslag welding.

In view of this objective, the present invention provides an electroslag welding method characterized in that electroslag welding of a base material is performed while applying a magnetic field to a molten pool within a groove of the base material.

The magnetic field may be a static magnetic field or a rotating magnetic field with a frequency of 1 Hz or less.

The electroslag welding method may apply a magnetic field from the front and back sides of the groove. In that case, the directions of the magnetic fields applied from the front side and the back side may be the same or opposite.

In the electroslag welding method, the welding torch is moved back and forth between the front side and the back side of the groove. Applying a magnetic field from the front side of the groove When approaching the iron core of the front side magnetic field applying coil, the current value of the front side magnetic field applying coil decreases, and the current value of the back side magnetic field applying coil applying a magnetic field from the back side of the groove. During the reciprocation of the welding torch, when the welding torch approaches the iron core of the magnetic field application coil on the back side, the current value of the magnetic field application coil on the back side is decreased, and the current value of the magnetic field application coil on the front side is increased. It may be something that increases the current value. In that case, when the welding torch comes closest to the iron core of the front side magnetic field application coil, the current value of the front side magnetic field application coil is the minimum, the current value of the back side magnetic field application coil is the maximum, and the welding torch is The current value of the magnetic field applying coil on the back side may be minimized and the current value of the magnetic field applying coil on the front side may be maximum when the magnetic field applying coil is closest to the iron core of the magnetic field applying coil. Further, the direction of the current flowing through the magnetic field applying coil on the front side and the magnetic field applying coil on the back side may be reversed every cycle of the reciprocating motion of the welding torch. Furthermore, when the welding torch is closest to the iron core of the front side magnetic field application coil or the back side magnetic field application coil and is stationary, the current of the front side magnetic field application coil and the current of the back side magnetic field application coil are determined as values. may be the same but in opposite directions.

The front and back sides of the groove may be opposite to the base material of the cooling copper plate disposed on the front and back sides of the groove.

In the electroslag welding method, at least one of the front side cooling copper plate placed on the surface of the groove and the back side cooling copper plate placed on the back side is fixed to the base material, and the front side cooling copper plate is fixed to the base material. The height of the central axis of the front electromagnet placed on the front side electromagnet from the reference plane matches the height from the reference plane of the central axis of the back side electromagnet placed on the back side cooling copper plate. The electromagnet may be used for welding while moving. In that case, one of the front side cooling copper plate and the back side cooling copper plate may be movable in the direction in which the groove portion extends.

In the electroslag welding method, both the front cooling copper plate placed on the surface of the groove and the back cooling copper plate placed on the back side are movable in the direction in which the groove extends, and the front cooling copper plate The front cooling copper plate and the back side should be placed so that the height from the reference plane of the central axis of the front electromagnet placed on the front side cooling copper plate matches the height from the reference plane of the central axis of the back side electromagnet placed on the back side cooling copper plate. It may be possible to weld the cooling copper plate while moving it.

Further, the present invention provides that electromagnets for applying a magnetic field to the molten pool in the groove are arranged on the side opposite to the base material of the cooling copper plate placed on the front and back surfaces of the groove of the base metal. The present invention also provides a magnetic field application device for electroslag welding characterized by the following.

The cooling copper plate may be provided with holes or grooves, and the iron core of the electromagnet may fit into the holes or grooves.

The magnetic field application device for electroslag welding further includes a welding torch that performs welding while reciprocating between the front side position and the back side position in the groove. When approaching the iron core of the front electromagnet that applies a magnetic field from the front side of the groove, the current value of the front electromagnet decreases, and the current value of the back electromagnet that applies a magnetic field from the back side of the groove decreases. During the reciprocation of the welding torch, when the welding torch approaches the iron core of the electromagnet on the back side, the current value of the electromagnet on the back side decreases and the current value of the electromagnet on the front side increases. It may be.

In the magnetic field application device for electroslag welding, at least one of the front side cooling copper plate placed on the surface of the groove and the back side cooling copper plate placed on the back side is fixed to the base material, and the front side cooling copper plate is fixed to the base material. The height of the central axis of the front electromagnet placed on the cooling copper plate from the reference plane matches the height of the central axis of the back electromagnet placed on the back cooling copper plate from the reference plane. The electromagnet and the electromagnet on the back side may be configured to be movable.

The magnetic field application device for electroslag welding has a structure in which both a front side cooling copper plate placed on the surface of the groove and a back side cooling copper plate placed on the back side are movable in the direction in which the groove extends, The height of the central axis of the front electromagnet placed on the front cooling copper plate from the reference plane matches the height of the central axis of the back electromagnet placed on the back cooling copper plate from the reference plane. The cooling copper plate and the back side cooling copper plate may be configured to be movable.

According to the present invention, it is possible to apply a magnetic field to the molten pool during electroslag welding.

(a) and (b) are perspective views of the magnetic field application device according to the first embodiment of the present invention, viewed from the front side. (a) and (b) are perspective views of the magnetic field application device according to the first embodiment of the present invention, viewed from the rear side. It is a figure showing the position of a front side coil and a back side coil in a magnetic field application device of a 1st embodiment of the present invention. FIG. 3 is a diagram showing the distribution of magnetic fields at a welding location. It is a graph comparing the magnetic field distribution when a coil is fitted to a water-cooled copper plate and the magnetic field distribution when a coil is not fitted to a water-cooled copper plate. FIG. 3 is a diagram showing the distribution of welding current density in a molten pool. (a) and (b) are diagrams showing the flow velocity vector distribution of molten metal on the upper surface of the molten pool. (a) and (b) are diagrams showing the flow velocity distribution of molten metal inside a molten pool. (a) to (e) are cross-sectional photographs of welded parts. It is a figure showing the position of a front side coil and a back side coil in a magnetic field application device of a 2nd embodiment of the present invention. (a) and (b) are graphs showing the distribution of welding current density in the height direction when the welding torch is at the frontmost and rearmost positions. 3 is a graph showing the distribution of magnetic flux density in the height direction in the configuration shown in Table 2. 3 is a graph showing the distribution of Lorentz force in the height direction in the configuration shown in Table 2. (a) and (b) are bar graphs comparing the average values of Lorentz force between the molten pool and the molten slag in the configuration shown in Table 2. (a) and (b) are graphs showing the distribution of welding current density with respect to the position of the welding torch for molten slag and molten pool. (a) and (b) are graphs showing the distribution of the Lorentz force on the front side and the rear side in the height direction when the welding torch is located on the front side and the rear side. (a) and (b) are bar graphs comparing the average values of the Lorentz force on the front side and the rear side when the welding torch is located on the front side and the rear side for the molten pool and the molten slag. (a) and (b) are diagrams illustrating problems that occur when the directions of the magnetic poles of the front coil and the rear coil are not changed. (a) to (d) are time charts for explaining a method of reversing the applied magnetic field for electromagnetic stirring. FIG. 7 is a side view of the configuration of a magnetic field application device in a first example of a third embodiment of the present invention. (a) and (b) are diagrams showing how the front coil and the rear coil move up and down. (a) and (b) are diagrams showing how the front coil and the rear coil move up and down. It is a figure showing the structure of the magnetic field application device in the 2nd example of the 3rd embodiment of the present invention. FIG. 7 is a side view of the configuration of a magnetic field application device in a second example of the third embodiment of the present invention. (a) and (b) are diagrams showing how the front water-cooled copper plate and the rear water-cooled copper plate move up and down. (a) and (b) are diagrams showing how the front water-cooled copper plate and the rear water-cooled copper plate move up and down.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[First embodiment]
First, the configuration of the magnetic field application device 1 in the first embodiment will be described. 1(a) and (b) are perspective views of the magnetic field application device 1 according to the first embodiment when viewed from the front side (also referred to as the front side), and FIGS. 2(a) and (b) are FIG. 2 is a perspective view of the magnetic field application device 1 according to the first embodiment when viewed from the rear side (also referred to as the back side).

As shown in FIGS. 1(a), (b) and 2(a), (b), the magnetic field application device 1 in the first embodiment includes a welding wire 5, a front water-cooled copper plate 10, and a rear water-cooled copper plate 10. It includes a water-cooled copper plate 20, a front coil 30, and a rear coil 40.

Welding wire 5 is inserted into groove 4 formed at the butt portion of base materials 2 and 3. Then, the molten slag 6 (see FIG. 3) in the groove 4 is supplied while being energized by a welding power source (not shown), and is melted by Joule heat generation in the molten slag 6, and the molten metal is transferred to a molten pool 7. (See Figure 3) to weld sequentially from the bottom to the top.

The front water-cooled copper plate 10 is a copper plate for water cooling that covers the front side of the groove portion 4 of the base materials 2 and 3. The front water-cooled copper plate 10 is provided with an inlet (not shown) through which cooling water for water cooling flows in, and an outlet (not shown) through which cooling water for water cooling flows out. Further, the rear water-cooled copper plate 20 is a copper plate for water cooling that covers the rear side of the groove portion 4 of the base materials 2 and 3. The rear water-cooled copper plate 20 is also provided with an inlet (not shown) through which cooling water for water cooling flows in, and an outlet (not shown) through which cooling water for water cooling flows out.

The front coil 30 is a magnetic coil arranged on the front water-cooled copper plate 10. The front coil 30 is energized by a coil power source (not shown) to generate a magnetic field and apply the magnetic field to the molten pool 7 (see FIG. 3). Further, the rear coil 40 is a magnetic coil arranged on the rear water-cooled copper plate 20. The rear coil 40 is also energized by a coil power source (not shown) to generate a magnetic field and apply the magnetic field to the molten pool 7 (see FIG. 3).

Here, FIG. 1(a) is a perspective view of the magnetic field application device 1 before the front coil 30 is fitted, and FIG. 1(b) is a perspective view of the magnetic field application device 1 after the front coil 30 is fitted. be. When the front water-cooled copper plate 10 moves upward as welding progresses, the front coil 30 also needs to move upward, so as shown in the figure, a hole 11 is provided in the front water-cooled copper plate 10, and the hole 11 into which the iron core 31 of the front coil 30 is fitted.

2(a) is a perspective view of the magnetic field application device 1 before the rear coil 40 is fitted, and FIG. 2(b) is a perspective view of the magnetic field application device 1 after the rear coil 40 is fitted. It is. Since the rear water-cooled copper plate 20 is fixed to the base materials 2 and 3, a groove 21 is provided in the rear water-cooled copper plate 20 in the vertical direction as shown in the figure, and the iron core 41 of the rear coil 40 is inserted into the groove. 21 and moves upward as welding progresses.

In this embodiment, as shown in FIGS. 1(a) and 2(b) and 2(a) and 2(b), the front coil 30 is arranged on the front side of the groove part 4, and the front coil 30 is arranged on the front side of the groove part 4. A coil 40 is arranged on the back side of the groove 4. Further, the front water-cooled copper plate 10 is arranged on the front surface of the groove 4, that is, the front surface, and the rear water-cooled copper plate 20 is arranged on the back surface of the groove 4, that is, the back surface. . In this state, the front coil 30 is arranged on the opposite side of the base materials 2 and 3 of the front water-cooled copper plate 10, and the rear coil 40 is arranged on the opposite side of the base materials 2 and 3 of the rear water-cooled copper plate 20. can be said to be on the opposite side.

In addition, in this embodiment, as shown in FIGS. 1(a), (b) and 2(a), (b), a plane passing through the center of the base materials 2, 3 and parallel to the base materials 2, 3. The positive direction of the X-axis is defined as the direction perpendicular to the direction of progress of welding and toward the right side when viewed from the front side of the base materials 2 and 3. Further, a direction passing through the center of the base materials 2, 3 and perpendicular to a plane parallel to the base materials 2, 3 and toward the rear side of the base materials 2, 3 is defined as a positive direction of the Y-axis. Further, the welding direction on a plane passing through the centers of the base materials 2 and 3 and parallel to the base materials 2 and 3 is defined as the positive direction of the Z-axis.

Next, specifications of the front coil 30 and the rear coil 40 in the magnetic field application device 1 of the first embodiment will be explained. The table below shows the specifications of the front coil 30 and the rear coil 40.

As shown in the table, the ampere turns of the front coil 30 are 6000 AT, and the ampere turns of the rear coil 40 are 9000 AT. Further, the sizes of the iron core 31 of the front coil 30 and the iron core 41 of the rear coil 40 are both 20 mm in diameter and 60 mm in length.

Next, the arrangement of the front coil 30 and the rear coil 40 in the magnetic field application device 1 of the first embodiment will be explained. FIG. 3 is a diagram showing the positions of the front coil 30 and the rear coil 40 in the magnetic field application device 1. In this embodiment, as shown in the figure, the axes of the iron core 31 of the front coil 30 and the iron core 41 of the rear coil 40 are located 20 mm to 25 mm below the tip of the welding wire 5. It is arranged like this. Since the distance from the tip of the welding wire 5 to the molten pool 7 is 10 mm to 15 mm, by arranging it in this way, the upper ends of the iron core 31 and the iron core 41 can be compared to the interface 8 between the molten slag 6 and the molten pool 7. Therefore, the height will be approximately the same or it will be lower.

Next, the distribution of the magnetic field applied to the welding location by the magnetic field applying device 1 of this embodiment will be explained. FIG. 4 is a diagram showing the distribution of the magnetic field at the welding location. Specifically, it is a simulation result of the magnetic field distribution at the welding location. The arrangement of the front coil 30 and rear coil 40 shown in FIG. 3 makes it possible to apply a magnetic field to the molten pool 7 while keeping the strength of the magnetic field low, which is applied to the molten slag 6 through which welding current is also flowing. I understand.

Next, in the magnetic field applying device 1 of this embodiment, a case where a coil is fitted into the water-cooled copper plate and a case where a coil is not fitted will be compared and explained. FIG. 5 is a graph comparing the magnetic field distribution when a coil is fitted to a water-cooled copper plate and the magnetic field distribution when a coil is not fitted to a water-cooled copper plate. Specifically, the former magnetic field distribution is obtained when the iron core 31 of the front coil 30 is fitted into the hole 11 of the front water-cooled copper plate 10 and the iron core 41 of the rear coil 40 is fitted into the groove 21 of the rear water-cooled copper plate 20. These are the simulation results of the magnetic field distribution in the molten pool 7. On the other hand, the latter magnetic field distribution is a state in which the iron core 31 of the front coil 30 is not fitted into the hole 11 of the front water-cooled copper plate 10 and the iron core 41 of the rear coil 40 is not fitted into the groove 21 of the rear water-cooled copper plate 20. These are simulation results of the magnetic field distribution in the molten pool 7 in a state where the tip of the iron core 41 is away from the molten pool 7. In the graph, the positive direction of the longitudinal position indicates the front direction of the magnetic field application device 1. From the graph, it can be seen that the strength of the magnetic field increases when the coil is fitted to the water-cooled copper plate, compared to when the coil is not fitted to the water-cooled copper plate. The increase in the strength of the magnetic field is particularly significant at the interface 8 before and after the molten pool 7 and can be increased by a factor of about two.

Next, the distribution of welding current density in the molten pool 7 in the magnetic field application device 1 of this embodiment will be explained. FIG. 6 is a diagram showing the distribution of welding current density in the molten pool 7. Specifically, these are simulation results of the distribution of welding current density observed from the rear side while applying a DC voltage of 30 V to the welding wire 5 while applying a magnetic field to the molten pool 7. From FIG. 5, the welding current density in the molten pool 7 is about 1.0×10 ⁵ [A/m ² ] to 3.2×10 ⁵ [A/m ² ], and the welding current density in the molten pool 7 is You can see that it is flowing. Therefore, by applying a static magnetic field to the welding current of this molten pool 7, electromagnetic stirring can be caused.

Next, the flow velocity distribution of the molten metal on the upper surface of the molten pool 7 generated by the magnetic field application device 1 of this embodiment will be explained. FIGS. 7A and 7B are diagrams showing the flow velocity vector distribution of the molten metal on the upper surface of the molten pool 7. FIG. Specifically, these are simulation results of the flow of molten metal generated inside the molten pool 7 by electromagnetic stirring. 7(a) shows a case where the direction of the magnetic field generated by the front coil 30 and the direction of the magnetic field generated by the rear coil 40 are the same, and FIG. 7(b) shows the direction of the magnetic field generated by the front coil 30. This shows a case where the direction of the magnetic field generated by the rear coil 40 is opposite. Since the largest Lorentz force acts on the parts of the molten pool 7 closest to the iron cores 31 and 41, the flow velocity is fastest at the front and rear sides of the molten pool 7, about 0.2 m/s. In FIG. 7(a), the direction of the magnetic field generated by the front coil 30 and the direction of the magnetic field generated by the rear coil 40 are the same, so the flow direction is the same on the front and rear sides of the molten pool 7, and the molten An S-shaped flow occurs in the horizontal plane of the pond 7. Moreover, as can be seen from FIGS. 7(a) and 7(b), the flow velocity distribution is asymmetrical. Therefore, reversing the direction of the applied magnetic field at a low frequency of 1.0 Hz or less is effective for averaging the stirring effect. However, if the frequency is set to 1.0 Hz or higher, the Lorentz force will reverse before the flow grows and the stirring effect will become smaller, so a frequency of 1.0 Hz or lower is appropriate.

Next, the flow velocity distribution of molten metal inside the molten pool 7 generated by the magnetic field application device 1 of this embodiment will be explained. FIGS. 8(a) and 8(b) are diagrams showing the flow velocity distribution of molten metal inside the molten pool 7. FIG. FIG. 8(a) shows the flow velocity distribution when a static magnetic field is applied. Here, the magnetomotive forces of the front coil 30 and the rear coil 40 are both 6000 AT, and the direction of the magnetic field generated by the front coil 30 and the direction of the magnetic field generated by the rear coil 40 are assumed to be the same. Further, FIG. 8(b) shows the flow velocity distribution when a 10 Hz rotating magnetic field rotating within the horizontal plane of the molten pool 7 is applied. Here, one front coil 30 and two rear coils 40 are used, and the magnetomotive force of each coil is 6000 AT. In each of FIGS. 8(a) and 8(b), the upper flow velocity distribution diagram shows the flow velocity distribution diagram on the upper surface of the molten pool 7, and the middle flow velocity distribution diagram shows the flow velocity distribution diagram on the center surface of the molten pool 7. , and the lower flow velocity distribution diagram shows the flow velocity distribution diagram on the lower surface of the molten pool 7. Comparing FIG. 8(a) and FIG. 8(b), it is clear that the flow velocity when a rotating magnetic field of 10 Hz is applied is one order of magnitude lower, and no stirring effect can be expected.

Next, the cross-sectional observation results of the welded portion 9 (see FIG. 3) will be explained. 9(a) to (e) are cross-sectional photographs of the welded portion 9. Specifically, Figures 9(a), (b), (c), (d), and (e) show the results when a static magnetic field is applied, and when a rectangular wave magnetic field with a frequency of 0.25 Hz is applied, respectively. (first time), when a square wave magnetic field with a frequency of 0.25 Hz was applied (second time), when a square wave magnetic field with a frequency of 1.0 Hz was applied, and when no magnetic field was applied. be. When these cross-sectional photographs are arranged in descending order of grain boundaries, (a) < (b), (c) < (d) < (e) as shown by arrows in the photographs. Compared to the case (e) when no magnetic field is applied, the grain boundaries are smaller when the static magnetic field (a) is applied, and the effect of grain boundary refinement due to electromagnetic stirring is obtained. I am able to do that. Furthermore, applying a rectangular wave magnetic field at a low frequency (less than 1.0 Hz) in (b) and (c) can also produce similar effects, although it is inferior to applying a static magnetic field in (a). is completed.

In this embodiment, the front coil 30 is arranged on the outside of the front water-cooled copper plate 10 arranged on the front side of the groove 4, and the rear coil 30 is arranged on the outside of the rear water-cooled copper plate 20 arranged on the rear side of the groove 4. 40 were placed. Specifically, a hole 11 is dug in the front water-cooled copper plate 10, and the iron core 31 of the front coil 30 is fitted into the hole 11, and a groove 21 is dug in the rear water-cooled copper plate 20, and the rear coil 40 is inserted into the groove 21. The iron core 41 was fitted. As a result, the strength of the magnetic field that can be applied to the molten pool 7 was improved, and the magnetic stirring effect of the molten pool 7 was also improved.

[Second embodiment]
The configuration of the magnetic field application device 1' in the second embodiment is the same as that shown in FIGS. 1(a), (b) and FIGS. 2(a), (b), so the description thereof will be omitted.

Next, the arrangement of the front coil 30 and the rear coil 40 in the magnetic field application device 1' of the second embodiment will be explained. FIG. 10 is a diagram showing the positions of the front coil 30 and the rear coil 40 in the magnetic field application device 1'. In this embodiment, the specifications of the front coil 30 and the rear coil 40 are set as shown in Table 2 below.

That is, as shown in FIG. 10, the iron core 31 of the front coil 30 and the iron core 41 of the rear coil 40 are positioned so that their axial centers are 20 mm below the interface 8 between the molten slag 6 and the molten pool 7. It is arranged so that This is because it is desired to reduce the magnetic field applied to the molten slag 6. Further, as shown in Table 2, the sizes of the iron core 31 of the front coil 30 and the iron core 41 of the rear coil 40 are both 20 mm in diameter and 60 mm in length. In this state, as shown in Table 2, the Lorentz force acting on the molten pool 7 and the molten slag 6 was estimated when a magnetomotive force of 3000 AT (ampere turns) was applied to the front coil 30 and the rear coil 40.

Furthermore, in electrus slag welding, the welding torch 90 is slid in the front-rear direction in order to uniformly weld the base materials 2 and 3 in the thickness direction. Although FIG. 3 does not show the sliding movement of this welding torch 90, FIG. 10 shows that the welding torch 90 slides in a width of 16 mm in the thickness direction. Specifically, it is assumed that the sliding movement is 9 mm toward the front and 7 mm toward the rear from the center in the thickness direction.

FIGS. 11A and 11B are graphs showing the distribution of welding current density in the height direction when the welding torch 90 is located at the frontmost side and when the welding torch 90 is located at the rearmost side, respectively. In these graphs, the welding current density on the front side of the molten pool 7 and molten slag 6 is shown as a solid line, and the welding current density on the back side of the molten pool 7 and molten slag 6 is shown as a broken line. From FIG. 11(a), when the welding torch 90 comes to the front side, comparing the welding current density on the front side of the molten pool 7 and the welding current density on the front side of the molten slag 6, it is found that the molten slag 6 is more concentrated than the molten pool 7. It can be seen that the welding current density is higher in the However, the absolute value of the welding current density on the rear side is smaller in the molten slag 6 than in the molten pool 7 because the welding torch 90 is moved away. On the other hand, it can be seen from FIG. 11(b) that the situation is opposite when the welding torch 90 is on the rear side.

FIG. 12 is a graph showing the distribution of magnetic flux density in the height direction in the configuration shown in Table 2. In this graph, the magnetic flux density on the front side of the molten pool 7 and molten slag 6 is shown by a solid line, and the magnetic flux density on the rear side of the molten pool 7 and molten slag 6 is shown as a broken line. From FIG. 12, it can be seen that as an effect of lowering the positions of the iron core 31 and the iron core 41, the magnetic field strength is lower in the molten slag 6 than in the molten pool 7.

FIG. 13 is a graph showing the distribution of Lorentz force in the height direction in the configuration shown in Table 2. In this graph, the Lorentz force on the front side of the molten pool 7 and molten slag 6 when the welding torch 90 is located on the front side is shown as a solid line, and the Lorentz force on the front side of the molten pool 7 and molten slag 6 when the welding torch 90 is located on the rear side is shown as a solid line. The Lorentz force on the rear side is shown by the dashed line.

FIGS. 14(a) and 14(b) are bar graphs comparing the average values of the Lorentz force between the molten pool 7 and the molten slag 6 in the configuration shown in Table 2. Specifically, FIG. 14(a) shows the average value of the Lorentz force acting on the front side of the molten pool 7 and molten slag 6 when the welding torch 90 is located on the front side, as shown by the solid line in FIG. 13. Moreover, FIG.14(b) shows the average value of the Lorentz force which acts on the rear side of the molten pool 7 and molten slag 6 when the welding torch 90 is located on the rear side, which is shown by the broken line in FIG. It can be seen from FIGS. 14(a) and 14(b) that a larger Lorentz force acts on the molten pool 7 than on the molten slag 6.

Next, a method for further suppressing the electromagnetic stirring effect occurring in the molten slag 6 will be described.

FIGS. 15A and 15B are graphs showing the distribution of welding current density with respect to the position of the welding torch 90 for the molten slag 6 and the molten pool 7, respectively. In each graph, the welding current density on the front side of the molten slag 6 or the molten pool 7 is shown as a solid line, and the welding current density on the rear side of the molten slag 6 or the molten pool 7 is shown as a broken line. Comparing the welding current density distribution in the middle of molten slag 6 in FIG. 15(a) and the welding current density distribution in the middle of molten pool 7 in FIG. The latter has a shape close to a linear function with respect to the position of the welding torch 90, whereas the latter has a shape close to a linear function with respect to the position of the welding torch 90. That is, the welding current density of the molten pool 7 has less dependence on the position of the welding torch 90 than the molten slag 6. Therefore, when the welding torch 90 comes closest to the iron core 31 of the front coil 30, it is preferable to minimize the current value of the front coil 30 and maximize the current value of the rear coil 40. Thereby, it becomes possible to apply a significant electromagnetic force to the molten pool 7 while effectively suppressing the electromagnetic force acting on the molten slag 6. Conversely, when the welding torch 90 comes closest to the iron core 41 of the rear coil 40, the current value of the rear coil 40 may be minimized and the current value of the front coil 30 may be maximized.

By such a method of energizing the front coil 30 and the rear coil 40, significant electromagnetic stirring can be applied to the molten pool 7, and electromagnetic stirring of the molten slag 6 can be suppressed, so that the molten slag 6 is rolled into the molten pool 7. Things will go away. As a result, the mechanical strength of the welded portion 9 is improved.

Therefore, a method was adopted in which the current values of the front coil 30 and the rear coil 40 were changed in synchronization with the position of the welding torch 90 as described above, and the distribution of the Lorentz force was estimated. The specifications of the front coil 30 and the rear coil 40 at that time are shown in Table 3 below.

In FIGS. 11(a) and 11(b), when the welding torch 90 is located at the front or rear side, the welding current density on the opposite side drops to less than half the maximum value of the welding current density at the position of the welding torch 90. was. In order to compensate for this decrease in welding current density, it is necessary to increase the applied magnetic field. Therefore, as shown in Table 3, the positions of the iron core 31 of the front coil 30 and the iron core 41 of the rear coil 40 are raised by 10 mm, and the current value is tripled for the front coil 30 and doubled for the rear coil 40. I made it bigger.

16(a) and (b) show the distribution in the height direction of the Lorentz force on the front side of the molten pool 7 and molten slag 6 when the welding torch 90 is located on the front side and the rear side, respectively, and the welding torch 90 is on the front side. It is a graph showing the distribution of the Lorentz force on the rear side of the molten pool 7 and the molten slag 6 in the height direction when the molten pool 7 and the molten slag 6 are located on the rear side. Among them, FIG. 16(a) shows the distribution of the Lorentz force on the front side of the molten pool 7 and molten slag 6 when the welding torch 90 is located on the rear side in the configuration shown in Table 3 with a thick line. In Fig. 16(a), the distribution of Lorentz force in the configuration of Table 2 is also shown by a thin line, but in the case of the configuration of Table 3, which is shown by a thick line, the Lorentz force can be suppressed more with molten slag 6. looks like. The same applies to the Lorentz force on the rear side when the welding torch 90 is located on the front side and the rear side, as shown in FIG. 16(b).

In order to make this quantitatively easier to understand, a graph is shown in which the average value was evaluated. 17(a) and (b) show the average values of the Lorentz forces on the front side of the molten pool 7 and molten slag 6 when the welding torch 90 is located on the front side and the rear side, respectively, and the welding torch 90 is on the front side and the rear side. It is a bar graph comparing the average value of the Lorentz force on the rear side of the molten pool 7 and the molten slag 6 when the molten pool 7 and the molten slag 6 are located at . Among them, FIG. 17(a) shows the average value of the Lorentz force on the front side of the molten pool 7 and molten slag 6 when the welding torch 90 is located on the front side and the rear side. From FIG. 17(a), it can be seen that in the configuration of Table 3, the Lorentz force of the molten slag 6 can be suppressed more than in the configuration of Table 2. The same applies to the Lorentz force on the rear side when the welding torch 90 is located on the front side and the rear side, as shown in FIG. 17(b).

As described above, by estimating the Lorentz force distribution in the configuration shown in Table 3 and changing the position of the welding torch 90 and the current values of the front coil 30 and rear coil 40 synchronously, the electromagnetic stirring effect of the molten slag 6 can be improved. Although it has been found that this can be suppressed, a problem arises if the current direction of the front coil 30 and rear coil 40, in other words, the direction of the magnetic poles is not changed.

FIGS. 18(a) and 18(b) are diagrams illustrating such a problem. As shown in FIG. 18(a), even when no magnetic field for electromagnetic stirring is applied to the molten slag 6, a pinch force is exerted on the molten slag 6 by the welding current, and a strong flow S flows from top to bottom along the welding wire 5. It is occurring. This flow S is bent in the left-right direction according to the direction of the Lorentz force by the action of the applied magnetic field for electromagnetic stirring. In FIG. 18(b), since the magnetic field M in the depth direction of the plane of the paper is applied, the Lorentz force F acts in the right direction, and as a result, the flow S curves in the right direction. As a result, temperature unevenness occurs in the molten slag 6 in the left-right direction, resulting in a difference in the amount of penetration between the base materials 2 and 3.

Therefore, in this embodiment, by periodically reversing the direction of the applied magnetic field for electromagnetic stirring, the amounts of penetration of the base materials 2 and 3 are made equal on the left and right sides.

FIGS. 19(a) to 19(d) are time charts for explaining a method of reversing the applied magnetic field for electromagnetic stirring. In these time charts, as shown in FIG. 19(a), the time during which the welding torch 90 is stationary on the rear side is defined as time t0 to time t1, and the time during which the welding torch 90 is moving from the rear side to the front side is defined as time t0 to time t1. is defined as time t1 to time t2, time during which welding torch 90 is stationary on the front side is defined as time t2 to time t3, and time during which welding torch 90 is moving from the front side to the rear side is defined as time t3 to time t0.

Among them, FIG. 19(c) shows an energization pattern when the direction of the magnetic pole is reversed every cycle of movement of the welding torch 90. Further, FIG. 19(d) shows an energization pattern when the direction of the magnetic poles is changed when the welding torch 90 is on the front side or the rear side. Furthermore, for comparison, FIG. 19B also shows an energization pattern in the case where the directions of the magnetic poles of the front coil 30 and the rear coil 40 are not changed in accordance with the sliding movement of the welding torch 90. In the energization pattern of FIG. 19(b), the maximum value and minimum value of the current value of the front coil 30 are respectively referred to as "front coil maximum" and "front coil minimum", and the maximum value of the current value of the rear coil 40, Assuming that the minimum values are "maximum rear coil" and "minimum rear coil", respectively, and even in the energization patterns of Figs. 19(c) and (d), if the direction of the magnetic pole is not reversed, these values are shown as is, and the magnetic pole When the direction of is reversed, these values are indicated with a minus sign.

In this embodiment, when the welding torch 90 approaches the iron core 31 of the front coil 30, the current value of the front coil 30 is minimized and the current value of the rear coil 40 is maximized, and the welding torch 90 Although the current value of the rear coil 40 is minimized and the current value of the front coil 30 is maximized when the rear coil 40 is closest to the iron core 41 of the rear coil 40, the present invention is not limited to this. When the welding torch 90 approaches the iron core 31 of the front coil 30, the current value of the front coil 30 is decreased and the current value of the rear coil 40 is increased, and the welding torch 90 approaches the iron core 41 of the rear coil 40. When approaching, the current value of the rear coil 40 may be decreased and the current value of the front coil 30 may be increased.

[Third embodiment]
The third embodiment relates to a mechanism for moving the front coil 30 and the rear coil 40 relative to the base materials 2 and 3.

In the first example of the third embodiment, the magnetic field application device 1 in the first embodiment is used. That is, the structure of the first example of the third embodiment is as shown in FIGS. 1(a), (b), FIGS. 2(a), (b), and FIG. 3. In this magnetic field application device 1, as described above, the rear water-cooled copper plate 20 is fixed to the base metals 2 and 3 and does not move, and the front water-cooled copper plate 10, the front coil 30, and the rear coil 40 are connected to the base metal 2, Move against 3.

FIG. 20 is a side view of the configuration of the magnetic field application device 1 in the first embodiment. As shown in the figure, the front water-cooled copper plate 10, the front coil 30, and the rear coil 40 are each fixed to a front up/down mechanism 50 and a rear up/down mechanism 60, which are independent from each other. Specifically, the front vertical lifting mechanism 50 holds the front water-cooled copper plate 10 and the front coil 30 against the base materials 2 and 3 by the front frame 51, and the rear vertical lifting mechanism 60 holds the front water-cooled copper plate 10 and the front coil 30 against the base materials 2 and 3 by the rear frame 61. The side coil 40 is pressed against the rear water-cooled copper plate 20. As a result, the front vertical lifting mechanism 50 vertically lifts the front water-cooled copper plate 10 and the front coil 30 along the base materials 2 and 3 to be welded, and the rear vertical lifting mechanism 60 moves the rear coil 40 to the rear side. The water-cooled copper plate 20 is moved up and down along a groove 21 cut therein. Note that, as shown in the figure, the front vertical lifting mechanism 50 is also provided with a welding torch 90 that feeds the welding wire 5.

21(a), (b) and FIG. 22(a), (b) are diagrams showing how the front coil 30 and the rear coil 40 move up and down. Specifically, FIGS. 21(a) and 21(b) show a state in which the front coil 30 and the rear coil 40 are in the initial position, and FIG. 21(a) is a view from the front. 21(b) is a view of it from the rear side. Moreover, FIGS. 22(a) and 22(b) show a state in which the front coil 30 and the rear coil 40 are being moved for welding, and FIG. 22(a) is a view of the front coil 30 and the rear coil 40 as seen from the front side, FIG. 22(b) is a view of it from the rear side.

As shown in FIGS. 21(a) and 22(a), a pedestal 70 is fixed to the base material 3, and the front vertical elevating mechanism 50 is moved up and down along the pedestal 70 by moving gears 52 and 53. Go up and down. Further, the front up/down mechanism 50 has a height sensor 54 that detects the height of the front coil 30. As the height sensor 54, a non-contact distance meter using infrared rays or the like can be used. It is preferable that a reflecting plate 55 is provided on the reference plane L1, and the height sensor 54 measures the distance to the reflecting plate 55. Note that the reference plane L1 may be provided at any height, but in the figure, it is provided at the height of the upper end of the rear water-cooled copper plate 20. Further, the front up/down mechanism 50 is also provided with a front controller 56 that controls transmitting height information detected by the height sensor 54 to the rear up/down mechanism 60.

As shown in FIGS. 21(b) and 22(b), a pedestal 80 is also fixed to the base material 3, and the rear vertical elevating mechanism 60 is moved up and down by moving gears 62 and 63 along the pedestal 80. go up and down. Further, the rear vertical lifting mechanism 60 has a height sensor 64 that detects the height of the rear coil 40. As the height sensor 64, a non-contact distance meter using infrared rays or the like can be used. It is preferable that a reflector 65 is provided on the same reference plane L1 as shown in FIGS. 21(a) and 22(a), and the height sensor 64 measures the distance to the reflector 65. Furthermore, when height information is transmitted from the front vertical lifting mechanism 50 to the rear vertical lifting mechanism 60, the rear coil is adjusted so that the transmitted height matches the height detected by the height sensor 64. A rear controller 66 is also provided for controlling the vertical movement of 40.

First, before starting welding, as shown in FIGS. 21(a) and 21(b), the heights (reference heights) of the front vertical lifting mechanism 50 and the rear vertical lifting mechanism 60 are set with respect to the reference plane L1. Adjust the positions of the front up/down mechanism 50 and the rear up/down mechanism 60 so that they match. As a result, the height of the front coil 30 and the height of the rear coil 40 match. This state is set as the initial state.

Next, when welding is started, the front vertical lifting mechanism 50 moves upward as the welding progresses, and the height A1 based on the reference plane L1 becomes shorter, as shown in FIG. 22(a). The front controller 56 sequentially transmits information about the height A1 of the front up/down mechanism 50 from the initial state to the rear controller 66. As a result, in the rear up/down mechanism 60, the height sensor 64 measures the height B1 of the rear up/down mechanism 60 from the reference plane L1, as shown in FIG. 22(b). Then, the rear controller 66 controls the position of the rear vertical lifting mechanism 60 so that the height A1 transmitted from the front controller 56 matches the height B1 measured by the height sensor 64. do.

In the first embodiment, the front controller 56 transmits information on the height A1 to the rear controller 66, and the rear controller 66 adjusts the height A1 to the rear controller 66 so that the height A1 matches the height B1. Although the position of the vertical elevating mechanism 60 is controlled, the present invention is not limited to this. For example, a common controller is provided on the front side and the rear side, the front side controller 56 and the rear side controller 66 respectively transmit information on height A1 and height B1 to this common controller, and this common controller A signal to control the position of the front vertical lifting mechanism 50 is sent to the front controller 56, and a signal to control the position of the rear vertical lifting mechanism 60 is sent to the rear controller 56 so that height A1 and height B1 match. It may also be sent to the controller 66.

In this manner, in the first example of the third embodiment, the positions of the front coil 30 and the rear coil 40 are made to match with respect to the height direction of the molten slag 6 and the molten pool 7. This makes it possible to suppress the molten slag 6 from moving wildly due to excitation, thereby making it possible to stabilize the bead shape and prevent inclusions and the like from entering.

Further, in the first example of the third embodiment, the rear water-cooled copper plate 20 is fixed to the base materials 2 and 3. This makes it possible to suppress leakage of molten slag 6 from the rear side, making it possible to stabilize the bead shape.

In addition, although the structure in which the front water-cooled copper plate 10 moves along the base materials 2 and 3 and the rear water-cooled copper plate 20 is fixed to the base materials 2 and 3 has been adopted in the above example, the present invention is not limited to this. The front water-cooled copper plate 10 is fixed to the base metals 2 and 3, and the rear water-cooled copper plate 20 moves along the base metals 2 and 3. A configuration fixed to 3 may also be adopted. In other words, a configuration may be adopted in which at least one of the front water-cooled copper plate 10 and the rear water-cooled copper plate 20 is fixed to the base materials 2 and 3.

In a second example of the third embodiment, a magnetic field application device 1' is provided in which the rear water-cooled copper plate 20 of the magnetic field application device 1 in the first embodiment is replaced with the same type as the front water-cooled copper plate 10. use FIG. 23 is a diagram showing the structure of the magnetic field application device 1'. In this magnetic field application device 1', the component corresponding to the front water-cooled copper plate 10 of the magnetic field application device 1 is the front water-cooled copper plate 10a, and the component corresponding to the rear water-cooled copper plate 20 of the magnetic field application device 1 is the rear water-cooled copper plate 10b. shall be. In this magnetic field application device 1', not only the iron core 31 of the front coil 30 fits into the hole 11a of the front water-cooled copper plate 10a and moves together, but also the iron core 41 of the rear coil 40 also fits into the hole 11a of the front water-cooled copper plate 10b. It is a mechanism that fits into the hole 11b and moves together.

FIG. 24 is a side view of the configuration of the magnetic field application device 1' in the second embodiment. As shown in the figure, the front water-cooled copper plate 10a and the rear water-cooled copper plate 10b are each fixed to a mutually independent front vertical lifting mechanism 50a and rear vertical lifting mechanism 50b. Specifically, the front up/down mechanism 50a presses the front water-cooled copper plate 10a against the base materials 2, 3 with the front frame 51a, and the rear up/down mechanism 50b holds the back water-cooled copper plate 10b with the back frame 51b. It is pressed against base materials 2 and 3. As a result, the front up/down mechanism 50a and the rear up/down mechanism 50b move the front water-cooled copper plate 10a and the rear water-cooled copper plate 10b up and down along the base materials 2 and 3 to be welded. Note that, as shown in the figure, a welding torch 90 for feeding the welding wire 5 is also provided in the front vertical lifting mechanism 50a.

25(a), (b) and FIG. 26(a), (b) are diagrams showing how the front water-cooled copper plate 10a and the rear water-cooled copper plate 10b move up and down. Specifically, FIGS. 25(a) and 25(b) show a state in which the front water-cooled copper plate 10a and the rear water-cooled copper plate 10b are in the initial position, and FIG. 25(a) is a view of this from the front side. , FIG. 25(b) is a view of it from the rear side. Moreover, FIGS. 26(a) and 26(b) show a state in which the front water-cooled copper plate 10a and the rear water-cooled copper plate 10b are being moved for welding, and FIG. 26(a) is a view of this from the front side. 26(b) is a view of it from the rear side.

As shown in FIGS. 25(a) and 26(a), a pedestal 70 is fixed to the base material 3, and the front vertical lifting mechanism 50a is moved up and down along the pedestal 70 by moving gears 52a and 53a. Go up and down. Further, the front up/down mechanism 50a has a height sensor 54a that detects the height of the front water-cooled copper plate 10a and the front coil 30. As the height sensor 54a, a non-contact distance meter using infrared rays or the like can be used. It is preferable that a reflecting plate 55a is provided on the reference plane L2, and the height sensor 54a measures the distance to the reflecting plate 55a. Note that the reference plane L2 may be provided at any height, but in the figure, it is provided at the height of the welding start position. Furthermore, the front up/down mechanism 50a is also provided with a front controller 56a that controls transmitting height information detected by the height sensor 54a to the rear up/down mechanism 50b.

As shown in FIGS. 25(b) and 26(b), a pedestal 80 is also fixed to the base material 3, and the rear vertical lifting mechanism 50b is moved up and down along the pedestal 80 by moving gears 52b and 53b. go up and down. Further, the rear vertical lifting mechanism 50b has a height sensor 54b that detects the height of the rear water-cooled copper plate 10b and the rear coil 40. As the height sensor 54b, a non-contact distance meter using infrared rays or the like can be used. It is preferable that a reflecting plate 55b is provided on the same reference plane L2 as shown in FIGS. 25(a) and 26(a), and the height sensor 54b measures the distance to the reflecting plate 55b. Further, when height information is transmitted from the front vertical lifting mechanism 50a to the rear vertical lifting mechanism 50b, the rear water cooling mechanism is set so that the transmitted height matches the height detected by the height sensor 54b. A rear controller 56b is also provided for controlling the vertical movement of the copper plate 10b.

First, before starting welding, as shown in FIGS. 25(a) and 25(b), the height of the front water-cooled copper plate 10a and the front coil 30 with respect to the reference plane L2, and the height of the rear side with respect to the reference plane L2. The heights of the water-cooled copper plate 10b and the rear coil 40 are made to match. This state is set as the initial state.

Next, when welding is started, the front vertical lifting mechanism 50a moves upward as the welding progresses, and the height A2 relative to the reference plane L2 becomes longer, as shown in FIG. 26(a). The front controller 56a sequentially transmits information about the height A2 of the front water-cooled copper plate 10a from the initial state to the rear controller 56b. As a result, in the rear up-down mechanism 50b, the height sensor 54b measures the height B2 of the rear water-cooled copper plate 10b from the reference plane L2, as shown in FIG. 26(b). Then, the rear controller 56b controls the position of the rear water-cooled copper plate 10b so that the height A2 transmitted from the front controller 56a matches the height B2 measured by the height sensor 54b. .

In the second embodiment, the front controller 56a transmits information on the height A2 to the rear controller 56b, and the rear controller 56b adjusts the height A2 to the rear controller 56b so that the height A2 and the height B2 match. Although the position of the water-cooled copper plate 10b is controlled, the present invention is not limited to this. For example, a common controller is provided on the front side and the rear side, the front side controller 56a and the rear side controller 56b respectively transmit information on height A2 and height B2 to this common controller, and this common controller A signal to control the position of the front water-cooled copper plate 10a is sent to the front controller 56a, and a signal to control the position of the rear water-cooled copper plate 10b is sent to the rear controller 56a so that height A2 and height B2 match. 56b.

In this way, in the second example of the third embodiment, the positions of the front coil 30 and the rear coil 40 are made to match with respect to the height direction of the molten slag 6 and the molten pool 7. This makes it possible to suppress the molten slag 6 from moving wildly due to excitation, thereby making it possible to stabilize the bead shape and prevent the inclusion of inclusions and the like.

DESCRIPTION OF SYMBOLS 1, 1'... Magnetic field application device, 2, 3... Base metal, 4... Groove part, 5... Welding wire, 6... Molten slag, 7... Molten pool, 8... Interface, 9... Welding part, 10, 10a... Front water-cooled copper plate, 11... hole, 20, 10b... rear water-cooled copper plate, 21... groove, 30... front coil, 31, 41... iron core, 40... rear coil, 50, 50a... front vertical lifting mechanism, 60, 50b... Rear vertical lifting mechanism, 54, 64, 54a, 54b... Height sensor, 55, 65, 55a, 55b... Reflector, 56, 56a... Front controller, 66, 56b... Rear controller, 90... welding torch

Claims (8)

Electroslag welding of the base metal is performed while applying a magnetic field to the molten pool in the groove of the base metal from the front and back sides of the groove,
An electroslag welding method characterized in that the directions of the magnetic fields applied from the front side and the back side are opposite. Electroslag welding of the base metal is performed while applying a magnetic field to the molten pool in the groove of the base metal from the front and back sides of the groove,
Welding while reciprocating a welding torch between a front side position and a back side position in the groove,
During the reciprocation of the welding torch, when the welding torch approaches the iron core of the front magnetic field application coil that applies the magnetic field from the front side of the groove, the current value of the front magnetic field application coil and increase the current value of a magnetic field applying coil on the back side that applies the magnetic field from the back side of the groove,
During the reciprocating motion of the welding torch, when the welding torch approaches the iron core of the magnetic field application coil on the back side, the current value of the magnetic field application coil on the back side is decreased, and the current value of the magnetic field application coil on the front side is decreased. An electroslag welding method characterized by increasing the current value. When the welding torch approaches the iron core of the magnetic field application coil on the front side, the current value of the magnetic field application coil on the front side is set to the minimum, and the current value of the magnetic field application coil on the back side is set to the maximum,
When the welding torch approaches the iron core of the magnetic field application coil on the back side, the current value of the magnetic field application coil on the back side is minimized, and the current value of the magnetic field application coil on the front side is maximized. The electroslag welding method according to claim 2 . 3. The electroslag welding method according to claim 2, wherein the direction of the current flowing through the magnetic field applying coil on the front side and the magnetic field applying coil on the back side is reversed every cycle of reciprocating motion of the welding torch. Electroslag welding of the base metal is performed while applying a magnetic field to the molten pool in the groove of the base metal from the front and back sides of the groove,
The front side and the back side are sides opposite to the base material of the cooling copper plate arranged on the front and back sides of the groove,
At least one of the front side cooling copper plate arranged on the surface of the groove portion and the back side cooling copper plate arranged on the back side is fixed to the base material,
The height of the central axis of the front electromagnet arranged on the front cooling copper plate from the reference plane is made to match the height of the central axis of the back electromagnet arranged on the back cooling copper plate from the reference plane. An electroslag welding method characterized in that the electromagnet on the front side and the electromagnet on the back side are welded while moving. 6. The electroslag welding method according to claim 5 , wherein one of the front side cooling copper plate and the back side cooling copper plate is movable in a direction in which the groove portion extends. Electromagnets for applying a magnetic field to the molten pool in the groove are placed on the side opposite to the base material of the cooling copper plate placed on the front and back sides of the groove of the base metal,
further arranging a welding torch that performs welding while reciprocating between a front side position and a back side position in the groove,
During the reciprocation of the welding torch, when the welding torch approaches the iron core of the front electromagnet that applies the magnetic field from the front side of the groove, the current value of the front electromagnet is decreased; Increasing the current value of the electromagnet on the back side that applies the magnetic field from the back side of the groove,
During the reciprocation of the welding torch, when the welding torch approaches the iron core of the electromagnet on the back side, the current value of the electromagnet on the back side is decreased and the current value of the electromagnet on the front side is increased. A magnetic field application device for electroslag welding characterized by : Electromagnets for applying a magnetic field to the molten pool in the groove are placed on the side opposite to the base material of the cooling copper plate placed on the front and back sides of the groove of the base metal,
At least one of the front side cooling copper plate arranged on the surface of the groove portion and the back side cooling copper plate arranged on the back side is fixed to the base material,
The height of the central axis of the front electromagnet arranged on the front cooling copper plate from the reference plane is made to match the height of the central axis of the back electromagnet arranged on the back cooling copper plate from the reference plane. A magnetic field application device for electroslag welding , characterized in that the electromagnet on the front side and the electromagnet on the back side are configured to be movable.