JP5419858B2 - Magnetic field strength adjustment method for arc welding - Google Patents

Description

  The present invention relates to a magnetic field strength adjustment method for arc welding. In detail, it is related with the magnetic field intensity adjustment method of plasma arc welding.

  Conventionally, arc welding is known. In arc welding, when the feed speed of the arc torch increases, a phenomenon occurs in which the arc flows behind the arc torch in the traveling direction and heat does not enter the workpiece. In this case, welding is performed without sufficiently preheating the workpiece, which causes a welding failure.

  In order to avoid the above phenomenon, for example, as shown in FIGS. 14 and 15, a magnetic field (B in FIG. 15) in a direction perpendicular to the joining direction with respect to an arc A extending from the tip of the nozzle of the arc torch 100 to the workpiece W. A technique for causing the arc A to swing forward in the direction of travel of the arc torch 100 using a Lorentz force F (shown by F in FIG. 15) generated by applying the action of the arc torch 100 has been proposed (see Patent Document 1).

Japanese Patent Application Laid-Open No. 61-206566

  By the way, the amount of the arc A swung forward in the traveling direction changes in accordance with the feed speed of the arc torch 100. For this reason, in order to sufficiently preheat the workpiece W, it is necessary to adjust the magnetic field strength of the weld according to the feed speed of the arc torch 100. For example, when the feed speed of the arc torch 100 is increased, the amount of the arc A shaken forward in the traveling direction is reduced, so that it is necessary to increase the magnetic field strength of the weld.

  When workpieces with different plate thicknesses are butt welded, the magnetic flux leaking to the surface of the butt portion of the workpiece W changes depending on the plate thickness difference, and the amount of arc A swung forward in the traveling direction changes. To do. For this reason, it is necessary to adjust the magnetic field intensity of a welded part according to a plate | board thickness difference. For example, when the plate thickness difference is reduced, the magnetic flux leaking to the surface of the butt portion is reduced, so that it is necessary to increase the magnetic field strength of the welded portion.

  Further, the welding current required for melting differs depending on the thickness of the workpiece W, and the amount of arc A swung forward in the traveling direction varies depending on the magnitude of the welding current. For this reason, it is necessary to adjust the magnetic field strength of the welded portion in accordance with the thickness of the workpiece W. For example, when the thickness of the workpiece W is increased, it is necessary to increase the magnetic field strength of the welded portion in order to increase the welding current.

  As a method of adjusting the magnetic field strength, a method of adjusting an exciting current by providing an electromagnet, a power source, a controller, and the like is common. However, this method has a problem that the cost increases and the apparatus becomes large. In particular, when these are attached to the arc torch, there is a problem in that the processing portion becomes large and the small turn becomes difficult.

  The present invention has been made in view of the above, and an object of the present invention is to provide a technique capable of adjusting the magnetic field strength of a welding portion while avoiding an increase in cost and an increase in size of an apparatus in arc welding using a magnetic field. It is to provide.

  In order to achieve the above object, in the present invention, arc welding (for example, plasma arc welding apparatus 1 to be described later) for welding a butted workpiece (for example, workpiece W to be described later) with an arc torch (for example, plasma torch 10 or 40 to be described later). , 2), a magnetic field in a direction orthogonal to the joining direction in which the arc torch travels (for example, a magnetic field B described later) is generated inside the workpiece, and the arc torch and the workpiece are The tip side of an arc (for example, arc A described later) is placed on the tip side of the arc torch by a Lorentz force (for example, Lorentz force F described later) caused by a current flowing between them (for example, current I described later) and the magnetic field. Provided is a method for adjusting the magnetic field strength of a welded part when arc welding by bending forward in the traveling direction. The magnetic field strength adjusting method for arc welding according to the present invention is characterized in that the magnetic field strength of the welded portion is adjusted by changing a relative position between the arc torch and the butted portion of the workpiece.

In the present invention, in arc welding using a magnetic field, the magnetic field strength of the welded portion is adjusted by changing the relative position between the arc torch and the butt portion of the workpiece. That is, since the original magnetic flux is not adjusted, there is no need to provide an electromagnet, a power source and a controller, and a small and inexpensive permanent magnet can be used instead. Therefore, according to the present invention, it is possible to easily adjust the magnetic field strength of the arc welded portion only by changing the relative position between the arc torch and the abutting portion of the workpiece while avoiding an increase in cost and an increase in the size of the apparatus.
In addition, since only the relative position between the arc torch and the abutting part of the work is changed, the magnetic field strength of the welded part can be easily adjusted according to the work thickness, plate assembly, welding speed, etc. Is possible.
The magnetic field strength adjusting method according to the present invention is particularly preferably applied to plasma arc welding with a wide bead width and a tolerance at the target position of the arc torch in the plate width direction.

  ADVANTAGE OF THE INVENTION According to this invention, in the arc welding using a magnetic field, the technique which can adjust the magnetic field intensity of a welding part can be provided, avoiding the increase in cost and the enlargement of an apparatus.

It is a perspective view of the plasma arc welding apparatus concerning a 1st embodiment. 1 is a front view schematically showing a plasma arc welding apparatus according to a first embodiment. It is a right view of the plasma arc welding apparatus shown in FIG. It is a figure which shows the magnetic flux density of the board width direction and joining direction of the workpiece | work which faced the thick board and the thin board. It is a figure which shows the magnetic flux density of the board width direction in the joining direction center part of the workpiece | work which faced | matched the thick board and the thin board. It is a figure which shows the aim position of the plasma torch in a board width direction. It is a perspective view of the plasma arc welding apparatus which concerns on 2nd Embodiment. It is sectional drawing of the plasma torch in the plasma arc welding apparatus which concerns on 2nd Embodiment. It is a perspective view of the 1st nozzle of the plasma torch in the plasma arc welding apparatus concerning a 2nd embodiment. It is a perspective view for demonstrating operation | movement of the plasma torch in the plasma arc welding apparatus which concerns on 2nd Embodiment. It is a top view for demonstrating operation | movement of the plasma torch in the plasma arc welding apparatus which concerns on 2nd Embodiment. It is a front view which shows roughly the plasma arc welding apparatus which concerns on 2nd Embodiment. It is a right view of the plasma arc welding apparatus shown in FIG. It is a front view which shows the conventional plasma arc welding apparatus roughly. It is a right view of the plasma arc welding apparatus shown in FIG.

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

<First Embodiment>
FIG. 1 is a perspective view of a plasma arc welding apparatus 1 according to a first embodiment to which a magnetic field strength adjusting method of the present invention is applied.
The plasma arc welding apparatus 1 forms a tailored blank material by butt welding the workpieces W. FIG. 1 shows butt welding of a workpiece W (1) having a relatively thin plate thickness and a workpiece W (2) having a plate thickness larger than that of the workpiece W (1).

  As shown in FIG. 1, the plasma arc welding apparatus 1 includes a plasma torch 10 as an arc torch, permanent magnets 20 </ b> S and 20 </ b> N that generate a magnetic field, and a support frame 30.

FIG. 2 is a front view schematically showing the plasma arc welding apparatus 1.
As shown in FIG. 2, the plasma torch 10 is provided with a rod-shaped electrode 11, a cylindrical first nozzle 12 that surrounds the electrode 11 and ejects plasma gas, and surrounds the first nozzle 12. And a cylindrical second nozzle 14 for jetting shield gas.

A circular first ejection port 13 is formed at the tip of the first nozzle 12, and plasma gas is ejected through the first ejection port 13.
An annular second jet port 15 is formed at the tip of the second nozzle 14, and the shield gas is jetted through the second jet port 15.
The second ejection port 15 of the second nozzle 14 is located closer to the distal end side in the axial direction of the electrode 11 than the first ejection port 13 of the first nozzle 12.

Returning to FIG. 1, the permanent magnets 20 </ b> S and 20 </ b> N generate a magnetic field B that bends the tip side of the arc A forward in the direction of travel of the plasma torch 10.
The magnetic field B generated inside the workpiece W by the permanent magnets 20S and 20N is a magnetic field in a direction orthogonal to the traveling direction (bonding direction) of the plasma torch 10. As shown in FIG. 3, which is a right side view of the plasma arc welding apparatus 1, the tip side of the arc A is caused by the Lorentz force F caused by the magnetic field B and the current I flowing between the plasma torch 10 and the workpiece W. The plasma torch 10 is bent forward in the direction of travel.

Returning to FIG. 1, the permanent magnets 20 </ b> S and 20 </ b> N are arranged on the front and rear and the left and right in a plan view so as to surround the plasma torch 10 around the plasma torch 10 positioned above the welded portion.
That is, two N-pole permanent magnets 20N are arranged on the front side and the rear side in the joining direction on one side (for example, the left side) of the abutting portion toward the front of the plasma torch 10 in the traveling direction (joining direction).
On the other side (for example, the right side) of the butted portion toward the traveling direction (bonding direction) of the plasma torch 10, two S-pole permanent magnets 20 </ b> S are arranged before and after the bonding direction.

The permanent magnet 20N and the permanent magnet 20S ahead in the joining direction are arranged to face each other in a plane orthogonal to the direction (joining line) in which the butted portion extends. Therefore, the direction of the magnetic field B from the permanent magnet 20N ahead of the joining direction toward the permanent magnet 20S is orthogonal to the extending direction (joining line) of the butted portion.
Similarly, the permanent magnet 20N and the permanent magnet 20S on the rear side in the joining direction are arranged to face each other in a plane orthogonal to the extending direction (joining line) of the butted portion. Therefore, the direction of the magnetic field B from the permanent magnet 20N behind the joining direction toward the permanent magnet 20S is orthogonal to the extending direction (joining line) of the butted portion.

The support frame 30 includes a pair of clamps 31 that hold the upper surface of the workpiece W. Each of the pair of clamps 31 includes a through groove 33 extending along the joining direction on the abutting portion side. The through groove 33 is formed with a width larger than the diameter of the cylindrical permanent magnets 20S and 20N.
The support frame 30 supports the permanent magnets 20S and 20N and the plasma torch 10 located at the center thereof.

The plasma torch 10 is supported by the support frame 30 so that the arc A extending from the lower end of the plasma torch 10 is positioned at a predetermined height at which the butted portion of the workpiece W can be welded.
Each of the permanent magnets 20S and 20N passes through the through groove 33 and is supported by the support frame 30 so that a minute gap is formed between the lower end surface thereof and the upper surface of the workpiece W.

  The distance between the permanent magnets 20S, 20N and the plasma torch 10 and the distance between the permanent magnets 20S, 20N and the workpiece W are such that the magnetic field B acts on the proximal end side of the arc A and the arc A is forward in the traveling direction from the proximal end. Are set so that the workpiece W is sufficiently magnetized and a large leakage magnetic field is generated on the surface of the butt portion, while avoiding the bending of the workpiece.

The support frame 30 includes a first lifting mechanism (not shown) that raises or lowers the plasma torch 10 and a first movement mechanism (not shown) that horizontally moves the plasma torch 10.
The support frame 30 includes a second lifting mechanism (not shown) that raises or lowers the permanent magnets 20S and 20N, and a second movement mechanism (not shown) that horizontally moves the permanent magnets 20S and 20N.

  Here, a method for adjusting the magnetic field strength of the welded part in plasma arc welding by the plasma arc welding apparatus 1 will be described with reference to FIGS. In the present specification, the magnetic field strength of the welded portion means the magnetic field strength of the portion facing the arc A directly under the plasma torch 10.

FIG. 4 shows a case where a magnetic field B in a direction perpendicular to the joining direction is generated inside the work W in the work W obtained by abutting the thin work W (1) and the thick work W (2). It is a figure which shows the magnetic flux density (magnetic flux density in the height position of 2 mm from the upper surface of a workpiece | work) in the board width direction orthogonal to a joining direction and a joining direction.
In FIG. 4, the butt portion is a reference point (0) in the plate width direction, the distance from the reference point on the thick plate side is represented by plus, and the distance from the reference point on the thin plate side is represented by minus. Further, the center part in the joining direction is defined as a reference point (0) in the joining direction, the distance from the reference point on the start side is represented by plus, and the distance from the reference point on the end side is represented by minus.

As shown in FIG. 4, in the plate width direction, the butt portion has the highest magnetic flux density, and the magnetic flux density decreases as the distance from the butt portion increases. This is because a large leakage magnetic field is generated from the abutting surface on the thick plate side due to the plate thickness difference. On the other hand, the magnetic flux density is substantially constant in the joining direction.
FIG. 5 is a diagram showing the magnetic flux density in the plate width direction at the center in the joining direction. As is apparent from FIG. 5, the butt portion has the highest magnetic flux density, and the magnetic flux density decreases as the distance from the butt portion increases.

In this way, in the workpiece W in which the thin workpiece W (1) and the thick workpiece W (2) are abutted, a magnetic field B in a direction orthogonal to the joining direction is generated inside the workpiece W. There is a characteristic that a difference in magnetic flux density occurs in the plate width direction. This characteristic is also confirmed in the case of a butt workpiece having no difference in thickness, but is more remarkable in a butt workpiece having a thickness difference.
Therefore, the magnetic field intensity adjustment method of the present embodiment uses this characteristic to adjust the target position of the plasma torch 10 in the plate width direction according to the required magnetic flux density. That is, the magnetic field strength of the welded portion is adjusted by changing the relative position between the plasma torch 10 and the butted portion of the workpiece W.

The magnetic field strength adjustment method of this embodiment will be described in detail with a specific example.
For example, the amount of arc A swayed forward in the traveling direction changes according to the feed speed (welding speed) of the plasma torch 10. For this reason, in order to sufficiently preheat the workpiece W, it is necessary to adjust the magnetic field strength of the weld according to the feed rate of the plasma torch 10.

  Therefore, in the magnetic field intensity adjustment method of the present embodiment, when the feed speed of the plasma torch 10 is increased, the target position of the plasma torch 10 in the plate width direction is changed to a position nearer to the butting portion and having a high magnetic flux density. For example, as shown in FIG. 6, the target position of the plasma torch 10 in the plate width direction is usually a position 0.5 mm away from the butted portion toward the thick plate (P2 in FIG. 6), and the feed rate is 20%. When the speed is increased, the butt portion (P1 in FIG. 6) having the highest magnetic flux density is changed. Thereby, since the magnetic field strength of the welded portion is increased, it is possible to suppress a decrease in the amount of arc A that is swung forward in the traveling direction by increasing the feed speed of the plasma torch 10.

  On the other hand, when the feeding speed of the plasma torch 10 is slowed, the target position of the plasma torch 10 in the plate width direction is changed to a position where the magnetic flux density is further away from the abutting portion. For example, as shown in FIG. 6, when the feed rate is slowed by 10%, the position is changed to a position (P3 in FIG. 6) that is 0.5 mm away from the normal position (P2 in FIG. 6) on the thick plate side. Thereby, since the magnetic field strength of a welding part falls, it can suppress that the quantity of the arc A swung ahead of the advancing direction by making the feed rate of the plasma torch 10 slow is suppressed.

  For example, when the workpieces having different plate thicknesses are butt-welded, the magnetic flux leaking to the surface of the workpiece W changes according to the plate thickness difference, and the amount of the arc A shaken forward in the traveling direction changes. For this reason, it is necessary to adjust the magnetic field intensity of a welded part according to a plate | board thickness difference.

  Therefore, in the magnetic field strength adjustment method of the present embodiment, when the plate thickness difference is reduced, the target position of the plasma torch 10 in the plate width direction is changed to a position nearer to the butted portion and having a higher magnetic flux density. Thereby, since the magnetic field strength of the welded portion is increased, it is possible to suppress a decrease in the amount of the arc A that is swung forward in the traveling direction by reducing the plate thickness difference.

  On the other hand, when the plate thickness difference is increased, the target position of the plasma torch 10 in the plate width direction is changed to a position where the magnetic flux density is further away from the butted portion. Thereby, since the magnetic field strength of a welding part falls, it can suppress that the quantity of the arc A swung ahead of the advancing direction by enlarging plate | board thickness difference becomes excess.

  Further, for example, the welding current required for melting differs depending on the plate thickness of the workpiece W, and the amount of arc A shaken forward in the traveling direction varies depending on the magnitude of the welding current. For this reason, it is necessary to adjust the magnetic field strength of the welded portion in accordance with the thickness of the workpiece W.

  Therefore, in the magnetic field strength adjustment method of the present embodiment, when the thickness of the workpiece W is increased, the target position of the plasma torch 10 in the width direction of the workpiece is changed to a position closer to the butted portion and having a high magnetic flux density. Thereby, since the magnetic field strength of the welded portion is increased, it is possible to suppress a decrease in the amount of the arc A that is swung forward in the traveling direction due to an increase in the welding current by increasing the plate thickness.

  On the other hand, when the plate thickness of the workpiece W is reduced, the target position of the plasma torch 10 in the plate width direction is changed to a position where the magnetic flux density is further away from the butted portion. Thereby, since the magnetic field strength of a welding part falls, it can suppress that the amount of arc A swung ahead in the advancing direction because welding current becomes small and plate | board thickness is thin can be suppressed.

  Operation | movement of the plasma arc welding apparatus 1 to which the magnetic field intensity adjustment method of this embodiment is applied is demonstrated, referring FIGS.

  First, according to the magnetic field strength adjustment method of the present embodiment, the target position of the plasma torch 10 in the plate width direction of the workpiece W is determined according to the plate thickness, plate thickness difference, welding speed, and the like of the workpiece W. After the determination, the workpiece W is clamped by the pair of clamps 31 so that the determined target position is arranged directly below the plasma torch 10 supported by the support frame 30.

  Next, the permanent magnets 20S and 20N are arranged at positions corresponding to the welding start ends by the second moving mechanism and the second elevating mechanism. At this time, the permanent magnets 20 </ b> S and 20 </ b> N pass through the through-groove 33 and are arranged so that a minute gap is formed between the lower end surface thereof and the upper surface of the workpiece W. Thus, a magnetic field B from the N-pole permanent magnet 20N to the S-pole permanent magnet 20S through the workpiece W is formed, and the magnetic field strength of the weld is set to a desired strength.

  Next, the plasma torch 10 is disposed at a predetermined height position on the welding start end by the first moving mechanism and the first lifting mechanism.

  Subsequently, an arc A is generated by applying a voltage between the electrode 11 and the workpiece W while ejecting plasma gas from the first ejection port 13 of the first nozzle 12. Further, a shielding gas is ejected from the second ejection port 15 of the second nozzle 14 so as to surround the arc A.

  Then, the tip side of the arc A is bent forward in the direction of travel of the plasma torch 10 by the Lorentz force F caused by the direction of the current I flowing through the arc A (see FIG. 1) and the magnetic field B leaking from the butt portion of the workpiece W. .

  In this state, the plasma torch 10 is horizontally moved in the joining direction by the first moving mechanism. Further, the permanent magnets 20 </ b> S and 20 </ b> N are horizontally moved in the joining direction along the through groove 33 by the second moving mechanism. Thereby, the molten pool P with which sufficient penetration depth was ensured is formed, and favorable welding is performed.

According to this embodiment, the following effects are produced.
(1) By generating the magnetic field B inside the work W, the place where the magnetic field B is the strongest is inside the work W, and the magnetic field B becomes weaker as the distance from the work W increases. Accordingly, the Lorentz force F that bends the arc A is stronger as it is closer to the workpiece W, and is weaker as it is closer to the plasma torch 10. For this reason, only the front end side of the arc A can be bent forward in the traveling direction of the plasma torch 10.

  (2) Since only the front end side of the arc A can be bent forward in the traveling direction of the plasma torch 10, for example, the arc A does not bend from the base end and floats from the workpiece W, and a deep heat input region is obtained. . For this reason, sufficient penetration depth can be secured.

  (3) Since only the front end side of the arc A can be bent forward in the traveling direction of the plasma torch 10 and a sufficient penetration depth can be ensured, a sufficient amount of heat input can be ensured forward in the traveling direction. For this reason, the welding speed can be improved.

  (4) Since only the front end side of the arc A can be bent forward in the traveling direction of the plasma torch 10, for example, the arc A is bent from the base end, and the bent arc A does not burn the nozzle itself, and the nozzle Does not damage. For this reason, consumption of the nozzle tip can be reduced.

  (5) By changing the relative position between the plasma torch 10 and the butted portion of the workpiece W, the magnetic field strength of the welded portion can be adjusted. That is, since the original magnetic flux is not adjusted, it is not necessary to provide an electromagnet, a power source, and a controller, and small and inexpensive permanent magnets 20S and 20N can be used. Therefore, it is possible to easily adjust the magnetic field strength of the welded portion only by changing the relative position between the plasma torch 10 and the butt portion of the workpiece W while avoiding an increase in cost and an increase in the size of the apparatus.

  (6) In addition, since only the relative position between the plasma torch 10 and the butted portion of the workpiece W is changed, the magnetic field strength of the welded portion can be easily changed according to the plate thickness, plate assembly, welding speed, etc. of the workpiece W. It can be adjusted and good welding is possible.

  (7) In the plasma arc welding by the plasma arc welding apparatus 1, the bead width is wide and the target position of the plasma torch 10 in the plate width direction of the workpiece W has a margin, so the magnetic field strength adjusting method according to this embodiment Is particularly preferably applied.

Second Embodiment
FIG. 7 is a perspective view of the plasma arc welding apparatus 2 according to the second embodiment to which the magnetic field strength adjusting method of the present invention is applied. In the following description, the same parts as those in the first embodiment are denoted by the same reference numerals, and redundant descriptions are omitted.

  As shown in FIG. 7, the plasma arc welding apparatus 2 has the same configuration except that the configuration of the plasma torch 40 is different from the plasma torch 10 of the first embodiment.

FIG. 8 is a cross-sectional view of the plasma torch 40.
As shown in FIG. 8, the plasma torch 40 is provided with a rod-shaped electrode 41, a cylindrical first nozzle 42 that surrounds the electrode 41 and ejects plasma gas, and surrounds the first nozzle 42. And a cylindrical second nozzle 47 that ejects a shielding gas.

A circular first ejection port 43 is formed at the tip of the first nozzle 42, and plasma gas is ejected through the first ejection port 43.
The first nozzle 42 includes a cylindrical inner cylinder portion 44 and an outer cylinder portion 45 provided so as to surround the inner cylinder portion 44.

FIG. 9 is a perspective view of the outer cylinder portion 45 of the first nozzle 42.
The distal end portion of the outer cylindrical portion 45 has a substantially conical shape that becomes thinner toward the distal end, and a plurality of groove portions 46 that are inclined with respect to the axial direction of the electrode 41 are formed on the outer peripheral surface of the distal end portion of the outer cylindrical portion 45. Is formed. The groove portion 46 extends to the tip of the outer cylinder portion 45.

Returning to FIG. 8, an annular second ejection port 48 is formed at the tip of the second nozzle 47, and the shield gas is ejected through the second ejection port 48.
The second ejection port 48 of the second nozzle 47 faces in a direction away from the electrode 41. Further, the second ejection port 48 of the second nozzle 47 is located closer to the proximal end side in the axial direction of the electrode 41 than the first ejection port 43 of the first nozzle 42.
Further, the groove 46 of the first nozzle 42 described above extends to the second ejection port 48 of the second nozzle 47.

  In the plasma arc welding by the plasma arc welding apparatus 2, the magnetic field strength adjusting method described above is applied as in the first embodiment.

  The operation of the plasma arc welding apparatus 1 to which the magnetic field strength adjusting method described above is applied will be described with reference to FIGS.

  First, according to the magnetic field strength adjusting method described above, the target position of the plasma torch 40 in the plate width direction of the workpiece W is determined according to the plate thickness, plate thickness difference, welding speed, and the like of the workpiece W. After the determination, the workpiece W is clamped by the pair of clamps 31 so that the determined target position is arranged directly below the plasma torch 40 supported by the support frame 30.

  Next, the permanent magnets 20S and 20N are arranged at positions corresponding to the welding start ends by the second moving mechanism and the second elevating mechanism. At this time, the permanent magnets 20 </ b> S and 20 </ b> N pass through the through-groove 33 and are arranged so that a minute gap is formed between the lower end surface thereof and the upper surface of the workpiece W. As a result, a magnetic field B is formed from the N-pole permanent magnet 20N through the workpiece W to the S-pole permanent magnet 20S (see FIG. 12), and the magnetic field strength of the welded portion is set to a desired strength. .

  Next, the plasma torch 40 is disposed at a predetermined height position on the welding start end by the first moving mechanism and the first lifting mechanism.

  Next, a voltage is applied between the electrode 41 and the workpiece W while the plasma gas is ejected from the first ejection port 43 of the first nozzle 42 to generate the arc A. Further, shield gas is ejected from the second ejection port 48 of the second nozzle 47 so as to surround the arc A.

Then, the shield gas flows in the direction of the white arrow in FIG. 10 along the plurality of groove portions 46 and is ejected from the second ejection port 48. The jetted shield gas flows in a spiral manner along the surface of the arc A while spreading in a direction away from the arc A, and rotates in the direction of the arc A with respect to the surface of the molten pool P, that is, FIG. Sprayed in the direction of the middle black arrow.
Specifically, as shown in FIG. 11, shield gas is sprayed on 8 locations of the workpiece W (1) and the workpiece W (2), and the flow direction of the shield gas at each location is indicated by a black arrow in FIG. 11. As shown.

  Further, the tip side of the arc A is bent forward in the traveling direction of the plasma torch 10 by the Lorentz force F caused by the direction of the current I flowing through the arc A (see FIG. 7) and the magnetic field B leaking from the butt portion of the workpiece W. .

  In this state, the plasma torch 40 is horizontally moved in the joining direction by the first moving mechanism. Further, the permanent magnets 20 </ b> S and 20 </ b> N are horizontally moved in the joining direction along the through groove 33 by the second moving mechanism. Then, the molten pool P in which sufficient penetration depth is ensured is formed so as to extend toward the front and rear of the arc A in a plan view as shown in FIG.

  Further, the molten metal in the region surrounded by the broken line in FIG. 11 on the rear side in the traveling direction of the arc A is pushed from the thick plate workpiece W (2) toward the thin plate workpiece W (1) by the sprayed shielding gas. Move. Thereby, favorable welding is performed while the recessed part of the base material of the thin workpiece | work W (1) is filled with this moved molten metal.

According to this embodiment, in addition to the effect of 1st Embodiment, the following effects are show | played.
(8) When welding the workpiece W (1) and the workpiece W (2) having a difference in plate thickness, a shield gas flowing spirally is sprayed on the surface of the molten pool P to melt the rear side of the arc A in the traveling direction. The metal can be moved toward the thin workpiece W (1). Thereby, the recessed part of the base material of the thin-plate workpiece | work W (1) can be filled with this moved molten metal. As a result, it is possible to suppress the thickness of the thin workpiece W (1) from being reduced by undercut, and to secure the strength of the workpiece W after welding.

  (9) Since the second ejection port 48 of the second nozzle 47 is directed away from the electrode 41, when the shield gas is ejected from the second nozzle 47, the injected shield gas is separated from the arc A. It will expand. Therefore, since the shielding gas does not directly hit the arc A, the arc A can be prevented from being disturbed, and the welding is stabilized.

  (10) Since the groove part 46 is extended to the 2nd jet nozzle 48 of the 2nd nozzle 47, even if it reduces the flow volume of shield gas, molten metal can be moved reliably, stabilizing plasma gas.

  (11) Since the second ejection port 48 of the second nozzle 47 is positioned closer to the proximal end side in the axial direction of the electrode 41 than the first ejection port 43 of the first nozzle 42, the shield gas directly hits the arc A. Can prevent arc A from being disturbed.

  (12) According to the present embodiment, the bead width is further widened by the shield gas that flows from the second ejection port 48 of the second nozzle 47 and flows spirally, and the plasma torch 40 is positioned at the target position in the plate width direction. Further, since there is a margin, the above-described magnetic field strength adjustment method is more preferably applied.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.
For example, in the above embodiment, the magnetic field strength of the weld is adjusted by shifting the clamp position of the workpiece W, but the present invention is not limited to this. The magnetic field strength of the welded portion may be adjusted by shifting the positions of the plasma torches 10 and 40 in the plate width direction with respect to the clamped workpiece W by the first moving mechanism.
Moreover, in the said embodiment, although the magnetic field strength adjustment method of this invention was applied to plasma arc welding, it is not limited to this. For example, it may be applied to TIG arc welding.

1, 2 ... Plasma arc welding equipment 10, 40 ... Plasma torch (arc torch)
20S, 20N ... Permanent magnet A ... Arc B ... Magnetic field I ... Current F ... Lorentz force W ... Workpiece

Claims (1)

In arc welding in which the butted workpieces are welded by an arc torch, a magnetic field in a direction perpendicular to the joining direction in which the arc torch proceeds is generated inside the workpiece,
Magnetic field strength of the weld when bending the front end side of the arc forward in the direction of travel of the arc torch by the Lorentz force caused by the current flowing between the arc torch and the workpiece and the magnetic field. A magnetic field strength adjustment method of arc welding for adjusting
A magnetic field strength adjustment method for arc welding, wherein the magnetic field strength of the welded portion is adjusted by changing a relative position between the arc torch and the butted portion of the workpiece.

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