JPH0424149B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a two-electrode rotating arc fillet welding method.

[Prior art and its problems]

When fillet welding a vertical plate and a horizontal plate, it is desirable to have a fillet welding method that can make the weld bead of equal length and accurately perform groove tracing welding.
There was no method that could meet such demands.

[Purpose of the invention]

An object of the present invention is to provide a two-electrode rotating arc fillet welding method that allows for equal leg length of the weld bead and accurate groove tracing control when fillet welding a vertical plate and a horizontal plate. be.

[Summary of the invention]

This invention aims a leading nozzle at a groove formed by a vertical plate and a horizontal plate, supplies a leading electrode along with a shielding gas toward the groove, and rotates the leading nozzle at a predetermined radius while A leading arc is generated between the leading electrode and the groove to form a lower layer bead, and a trailing nozzle is provided upstream of the leading nozzle in the direction of welding progress with a space between the leading nozzle and the trailing nozzle. A nozzle is directed toward the lower bead, a trailing electrode is supplied along with a shielding gas toward the lower bead, and while the trailing nozzle is rotated at a predetermined radius, a trailing arc is created between the trailing electrode and the lower bead. is generated to form an upper layer bead on the lower layer bead, and at this time, the vertical plate and the horizontal plate are fillet welded based on the following conditions, and the rotational speed of the preceding arc (N _L ): N ₀ ~120Hz, rotation diameter of the preceding arc (D _L ): 1 to 6 mm, rotation speed of the trailing arc (N _T ): N ₀ , rotation diameter of the trailing arc (D _T ): (W _L ~8 mm ) and 1mm
The rotational direction of the trailing arc is within the range (W _L + 6 mm) from whichever is larger, and when the vertical plate is placed on the right side facing the direction of welding progress, the direction of rotation of the trailing arc is clockwise when viewed from above the trailing nozzle. , when the vertical plate is arranged on the left side facing the direction of welding progress, the trailing nozzle rotates to the left when viewed from above; the distance between the leading electrode and the trailing electrode: the leading crater caused by the leading arc and the The distance between the trailing arc and the trailing crater, provided that N ₀ is the rotation of the arc where the ratio of vertical leg length (l ₁ ) to horizontal leg length (l ₂ ) (l ₁ /l ₂ ) is maximum. Velocity, W _L : A predetermined range that includes the width of the lower bead and any one of the voltage and current of the preceding arc and includes the most downstream position (C _f ) of the preceding electrode in the welding direction. detecting the position of the preceding electrode corresponding to the point of change in the variation value within, moving the preceding electrode in the width direction of the groove based on a signal corresponding to the position of the preceding electrode; Integrate the value over the predetermined range, calculate the difference between the thus obtained integrated value (S _cf ) and the reference voltage (E ₀ ),
moving the preceding nozzle in the direction of its central axis so that the difference (S _cf −E ₀ ) becomes zero;
A fluctuation value of any one of the voltage and current of the trailing arc is detected, and the detected fluctuation value is determined at the most downstream position (C _f ′), the rightmost position (R), and The front integral value (S _cf ′), the right integral value (S _R ), and the left integral value (S L ) are calculated by integrating over the respective predetermined ranges centering on the leftmost position ( _L ), and calculating the right integral value. The difference between the value (S _R ) and the left side integral value (S _L ) is calculated, and the trailing nozzle is moved to the groove so that the calculated value of the difference (S _R −S _L ) matches the reference value. The front integral value (S _cf ′) and the preset reference voltage (E ₀ ′)
The method is characterized in that the following nozzle is moved in its axial direction so that the calculated value of the difference (S _cf ′−E ₀ ′) becomes zero. .

[Structure of the invention]

The method of this invention will be explained with reference to the drawings.

FIG. 1 is a perspective view showing a vertical plate and a horizontal plate being fillet welded by the method of the present invention.

As shown in FIG. 1, the leading nozzle 1A rotating around the rotation axis consists of a vertical plate '2' and a horizontal plate '3'.
It is aimed at the groove formed by. The leading electrode 4A is offset from the rotation axis of the leading nozzle 1A and is supplied together with the shielding gas toward the groove. The lower bead 5A is formed by a leading arc generated between the leading electrode 4A and the groove.

Trailing nozzle 1B that rotates around the rotation axis
is provided on the upstream side of the preceding nozzle 1A in the direction of welding progress and is spaced apart from the preceding nozzle 1A.
It is directed towards A. The trailing electrode 4B is deviated from the rotation axis of the trailing nozzle 1B, and the trailing electrode 4B is connected to the lower layer bead 5A.
is supplied together with shielding gas. The upper layer bead 5B is formed by a trailing arc generated between the trailing electrode 4B and the lower layer bead 5A.

When the vertical plate is placed on the right side facing the welding direction, the trailing arc rotates to the right when viewed from above the trailing nozzle.On the other hand, when the vertical plate is placed on the left side facing the welding direction, the trailing arc rotates clockwise. Rotate to the left when looking from above the row nozzle.

The reason why the direction of rotation of the trailing arc is limited as described above will be explained.

When the arc is rotated as described above, the effect of scooping up the molten metal that hangs down due to the influence of gravity is produced, and the length of the bead can be made equal.
The scooping effect is related to the rotational speed of the arc, and when the welding current and welding speed are fixed, the scooping effect is maximized when the arc is rotated at an appropriate rotational speed (N ₀ ).

To determine the appropriate rotational speed (N ₀ ), rotate the arc in the above-mentioned direction, perform fillet welding at a predetermined welding current and welding speed, and calculate the vertical leg length (l ₁ ) and horizontal leg length ( What is necessary is to find the rotational speed of the arc at which the ratio _{(l 1 /} l ₂ ) with respect to l 2 ) is maximum. Figure 2 shows the arc rotation speed (N) and leg length ratio (l ₁ /
l ₂ ). As is clear from FIG. 2, the appropriate rotation speed (N ₀ ) of the arc under the above-mentioned welding conditions is 7 Hz (420 revolutions/min). That is, when the arc is rotated at this rotation speed, the leg length ratio (l ₁ /l ₂ ) is maximized. This shows that the effect of scooping up the molten metal due to the rotation of the arc is maximized, and the sagging of the molten metal can be prevented.

Therefore, in this invention, the direction of rotation of the trailing arc is limited as described above.

When the rotational speed of the arc is at the above-mentioned appropriate rotational speed (N ₀ ), it is possible to prevent the molten metal from drooping, but in this case, as shown in FIG.
Because the surface of the bead protrudes like a chevron, extra weld metal is required to obtain a predetermined leg length.
When the leading bead 5A protrudes in a chevron shape, the trailing electrode 4
Bead formation by B is not performed well.

Therefore, in this invention, the lower bead 5A ignores the isopod length to some extent, and the lower bead 5A
We are trying to smooth the surface.

The reason why the rotational speed (N _L ) of the preceding arc was limited to the range of N ₀ to 120 Hz in order to smooth the surface of the lower bead 5A will be explained.

FIG. 4 shows the relationship between the arc rotation speed (N) and the ratio of the maximum bead protrusion height (Δl) to the average value of the vertical leg length (l ₁ ) and horizontal leg length (l ₂ ).
As is clear from FIG. 4, it can be seen that when the rotational speed (N) of the arc exceeds _N0 , the surface of the bead 5A becomes smooth. The rotational speed of the arc (N) is
If N is less than ₀ , sufficient penetration of the horizontal and vertical plates cannot be ensured, which is not preferable.

Further, FIG. 5 shows the relationship between the rotational speed (N) of the arc and the amount of spatter. As is clear from FIG. 5, it can be seen that the amount of spatter increases rapidly when the rotational speed (N) of the arc exceeds 120 Hz.

Therefore, in this invention, the rotation speed (N _L ) of the leading arc is limited to the range of N ₀ to 120 Hz.

Next, in this invention, the reason why the rotational diameter (D _L ) of the leading arc is limited to a range of 1 to 6 mm will be explained.

If the rotating diameter (D _L ) of the leading arc is less than 1 mm, the function of rotating arc welding cannot be fully demonstrated, and since the rotating diameter is small, groove tracing control, which will be described later, cannot be performed with high precision. On the other hand, when the rotational diameter (D _L ) of the leading arc exceeds 6 mm, the leading arc approaches the vertical plate 2 and the horizontal plate 3 too much, and undercuts are particularly likely to occur on the vertical plate 1 side.

Therefore, in this invention, the rotational diameter (D _L ) of the leading arc is limited to a range of 1 to 6 mm.

In this invention, the reason why the rotational speed (N) of the trailing arc is set to (N ₀ ), that is, the above-mentioned appropriate rotational speed, is to achieve equal leg length of the trailing bead as described above.

Next, in this invention, the reason why the rotational diameter (D _T ) of the trailing arc is limited to the range of (W _L +6 mm) from the larger of (W _L −8 mm) and 1 mm will be explained. Here, (W _L ) represents the width of the lower layer bead 5A, as shown in FIG. 6, which is a cross-sectional view of the weld bead obtained by the method of the present invention.

If the rotational diameter (D _T ) of the trailing arc is less than the lower limit value, sufficient penetration of the vertical plate 2 and horizontal plate 3 cannot be ensured, and groove tracing control by the trailing electrode described later cannot be performed with high accuracy. That's because there isn't. On the other hand, if the rotational diameter (D _T ) of the trailing arc exceeds the upper limit value, the trailing arc will come too close to the vertical plate 2 and the horizontal plate 3, and undercuts are likely to occur particularly on the vertical plate 2 side. Because it will be.

In this invention, the leading electrode 4A and the trailing electrode 4
A gap is provided between B and B so that the leading crater caused by the leading arc and the trailing crater caused by the trailing arc do not overlap, but this is done in order to prevent magnetic blowing and not to disturb the bead shape. This is to do so.

Next, a method of controlling the groove tracing of the leading electrode 4A in this invention will be explained.

Figure 7 is a block diagram of the groove tracing control method for the leading electrode 4A, and Figure 8A shows fillet welding when the rotation axis of the leading nozzle is at an appropriate position relative to the center (root) in the width direction of the groove. FIG.

In FIGS. 7 and 8A, the leading arc voltage detector 6 includes a leading electrode 4A rotating at a predetermined speed.
Detects the voltage between the current and current voltage, that is, the preceding arc voltage (E). The switching device 7 converts the preceding arc voltage (E) detected by the preceding arc voltage detector 6 into a peak value (described later) in a predetermined arc rotation range in accordance with a command signal from a controller to be described later. Sends to voltage position detector and integrator. Controller 8
operates the switch 7 based on the position signal of the leading electrode 4A detected by the leading electrode position detector 9. The peak voltage position detector 10 receives the leading arc voltage (E) detected by the leading arc voltage detector 6, the position signal of the leading electrode 4A detected by the leading electrode position detector 9, and the switching device 7. According to the switching signal, the voltage (E〓) corresponding to the position of the preceding electrode where the preceding arc voltage is maximum, that is, the change point, is detected within the predetermined arc rotation range. The voltage (E〓) corresponds to the phase difference of the preceding electrode from the reference position. The memory 11 stores the voltage (E〓). The X-axis driver 12 is
The X-axis motor 13 for moving the preceding nozzle 1A in the groove width direction is driven so that the voltage (E〓) stored in the memory 11 becomes zero.

The integrator 14 integrates the preceding arc voltage from the switching device 7 over the predetermined arc rotation range. The memory 15 stores the integrated value (S _cf )
remember. The differential amplifier 16 calculates the difference between the reference voltage (E ₀ ) corresponding to the preceding nozzle height preset by the reference voltage setter 17 and the integrated value (S _cf ). The Y-axis driver 18 drives the Y-axis motor 19 for moving the preceding nozzle 3 in its axial direction so that the calculated value of the difference (S _cf −E ₀ ) becomes zero.

The φ setting device 20 sets the predetermined arc rotation range in the controller 8 in advance. The n setting device 21 detects the peak voltage position and integrates the preceding arc voltage.
The number of rotations of the preceding nozzle 1A is set in advance in the controller 8. For example, when the number of times of peak voltage position detection and arc voltage integration is set to a plurality of times by the n setter 21, the memory 1
1 calculates the average value of the plurality of voltages (E ₀ ), and the memory 15 calculates the average value of the plurality of integral values (S _cf ).

Here, the arc rotation range is set to (φ ₀ ) by the φ setter 20, and the n setter 2
1, the groove tracing control of the preceding nozzle 1A will be described when the number of times of peak voltage position detection and preceding arc voltage integration is set to one.

As shown in FIG. 8A, when the center axis of the leading nozzle 1A is oriented toward the center in the width direction of the groove, the leading arc voltage (E) detected by the leading arc voltage detector 6 As shown in FIG. 9A, is the minimum when the leading electrode 4A is closest to the vertical plate 2 and the horizontal plate 3, and is the maximum when the leading electrode 4A is located at the center in the width direction of the groove. becomes. In FIG. 9A, (C _r ) means the preceding nozzle 1
As shown in FIG. 10, which shows the rotational position of the leading electrode 4A viewed from the upper end of A, the most upstream position in the welding direction of the leading electrode 4A is shown, and (R) is the leading electrode 4A.
Indicates the position when A is closest to the vertical plate 2,
(C _f ) indicates the most downstream position of the leading electrode 4A in the welding progress direction, and (L) indicates the position when the leading electrode 4A approaches the horizontal plate 3 most.

The arc rotation range (〓 ₀ ) is the rotation range of the preceding arc centered on the forwardmost point (C _f ) in the welding direction.

Next, as shown in FIG. 8B, the preceding nozzle 4A
If the axis of rotation of is shifted toward the horizontal plate 3 along the groove width direction (X-axis direction), the preceding arc voltage (E) detected by the preceding arc voltage detector 6
As shown by the solid line in FIG. 9B, the preceding electrode 4A
The leading arc voltage (E) decreases as it approaches the vertical plate 2 and horizontal plate 3, but the leading arc voltage (E) when the leading electrode 4A is closest to the horizontal board 3 is the same as that when the leading electrode 4A is closest to the vertical plate 2. The leading electrode position is smaller than the arc voltage and where the leading arc voltage (E) is maximum in the arc rotation range (φ ₀ ).
As shown in FIG. 9A, there is a delay of (θ) compared to the case where the rotation axis of the preceding nozzle 1A faces the center in the width direction of the groove. The position of the preceding electrode 4A where the preceding arc voltage (E) is maximum is detected as a voltage (Eφ) by the peak voltage position detector 10.
The X-axis motor 13 moves the preceding nozzle 1A in the groove width direction so that the voltage (Eφ) becomes zero.

Next, as shown in FIG. 9C, the preceding nozzle 1A
When the axis of rotation of is shifted toward the vertical plate 2 along the groove width direction, the leading arc voltage (E) detected by the leading arc voltage detector 6 is as shown by the solid line C in FIG. As shown in , the leading electrode 4A decreases as it approaches the vertical plate 2 and the horizontal plate 3, but the leading arc voltage (E) when the leading electrode 4A approaches the vertical plate 2 is the same as when the leading electrode 4A is horizontal. The arc voltage is smaller than the arc voltage when closest to the plate 3, and
Leading arc voltage in the arc rotation range (φ ₀ )
As shown in FIG. 9A, the position of the leading electrode where (E) is maximum is advanced by (θ) compared to the case where the center axis of the leading nozzle 1A faces the center in the width direction of the groove. The position of the preceding electrode 4A where the preceding arc voltage is maximum is detected as a voltage (-E〓) by the peak voltage position detector 10. The X-axis motor 13 is
Lead nozzle 1 so that the voltage (-E〓) becomes zero.
Move A in the groove width direction.

Next, the height direction (Y-axis direction) of the preceding nozzle 1A
When the position of changes, the integral value (S _cf ) of the preceding arc voltage in the arc rotation range (φ ₀ ) calculated by the integrator 14 by the differential amplifier 16
and the reference voltage (E ₀ ), and the Y-axis motor 19 moves the preceding nozzle 1A in the height direction so that the value of the difference (S _cf −E ₀ ) becomes zero. let

In this way, the groove tracing control by the leading electrode 4A is performed with high precision.

Next, a method of controlling the groove tracing of the trailing electrode 4B in the present invention will be explained.

FIG. 11 is a block diagram of a method for controlling the groove tracing of the trailing electrode 4B.

In FIG. 11 and FIG. 8A, the trailing arc voltage detector 22 is. The voltage between the lower bead 5A and the trailing electrode 4B rotating at a predetermined speed, that is,
Detect trailing arc voltage (E′). Switcher 23
The trailing arc voltage (E') detected by the arc voltage detector 22 is switched to the left, right, and front sides, respectively, in response to a command signal from a controller to be described later. The controller 24 includes a trailing electrode position detector 25
The switch 23 is actuated based on the position signal of the trailing electrode 4B detected by. The right, left, and front integrators 26A, 26B, and 26C integrate the trailing arc voltage switched by the switch 23 to obtain right, left, and front integral values (S _R ),
(S _L ), (S _cf ′) are obtained. The integral range setter 27 is
The range of integration of the trailing arc voltage by the integrators 26A to 26C is set in the controller 24 in advance. The integration number setter 28 presets in the controller 24 the number of rotations of the trailing nozzle 1B at which the integrators 26A to 26C perform the integration.

Right side, left side, front memory device 29A, 29B, 29
C stores the integral values (S _R ), (S _L ), and (S _cf '), respectively. The differential amplifier 30 is connected to the right memory 29
The right side integral value (S _R ) stored by A and the left side integral value (S _L ) stored by left side storage 29B.
Calculate the difference between The X-axis driver 31 moves the trailing nozzle 1B in the width direction of the lower bead 5A so that the calculated value of the difference (S _R - S _L ) matches the reference value.
That is, the X-axis motor 3 for moving in the X-axis direction
Drive 2.

The differential amplifier 33 uses the front integral value (S _cf ') stored in the front memory 29C and the reference voltage (E ₀ ') preset by the reference voltage setter 34.
Calculate the difference between The Y-axis driver 35 includes a Y-axis motor 36 for moving the trailing nozzle 1B in its axial direction, that is, in the Y-axis direction so that the calculated value of the difference (S _cf ′−E ₀ ′) becomes zero. to drive.

Here, a description will be given of the groove tracing control of the trailing nozzle 1B when the integration range is set to 90 degrees and the number of integrations is set to 1.

As shown in FIG. 8A, when the trailing nozzle 1B faces the center in the width direction of the lower bead 5A, the trailing arc voltage (E ') is minimum when the trailing electrode 4B is closest to the vertical plate 2 and the horizontal plate 3, as shown in FIG. 12A, and becomes constant at other times.

The positions (R), (C _r ), (L) and (C _f ') of the trailing electrode 4B in FIGS. 12A to 12C are the same as those of the leading electrode 4A shown in FIG. 9.

For this reason, the above right integral value (S _R )
is the integral value of the trailing arc voltage in the range of ±45° centered on point (R), and the above left side integral value (S _L ) is the trailing arc voltage in the range of ±45° centered on point (L) The above integral value (S _cf ') is the integral value of the trailing arc voltage within a range of ±45° centered on the point (C _f ').

Next, as shown in FIG. 8B, the trailing nozzle 1B
When the trailing arc voltage (E') is shifted toward the horizontal plate 2 along the groove width direction, the trailing arc voltage (E') detected by the trailing arc voltage detector 22 is as shown in FIG. 12B. , the trailing electrode 4B is connected to the vertical plate 2 and the horizontal plate 3.
However, the trailing arc voltage when the trailing electrode 4B is closest to the horizontal plate 3 is smaller than the trailing arc voltage when the trailing electrode 4B is closest to the vertical plate 2. As a result, the right side integral value (S _R ) is larger than the left side integral value (S _L ). The difference between these integral values (S _R ) and (S _L ) is calculated by the differential amplifier 30, and the X-axis driver 31 is operated so that the calculated value of the difference (S _R - S _L ) becomes zero.
The X-axis motor 32 is driven by. As a result, the trailing nozzle 1B moves toward the center in the width direction of the groove.

Next, as shown in FIG. 8C, the trailing nozzle 1B
When the trailing arc voltage (E') is shifted toward the vertical plate 2 along the groove width direction, the trailing arc voltage (E') detected by the trailing arc voltage detector 22 is as shown in FIG. 12C. , the right side integral value (S _R ) is smaller than the left side integral value (S _L ). The difference between these integral values (S _R ) and (S _L ) is calculated by the differential amplifier 30, and the X-axis driver is operated so that the calculated difference value (S _R - S _L ) becomes zero. 31 by X-axis motor 32
is driven. As a result, the leading nozzle 1B moves toward the center in the width direction of the groove.

When the position of the trailing nozzle 1B in the Y-axis direction changes, the differential amplifier 33 calculates the difference between the front integral value (S _cf ′) and the reference voltage (E ₀ ′), and The Y-axis motor 36 is controlled by the Y-axis driver 35 so that the calculated value (S _cf ′−E ₀ ′) becomes zero.
is driven. Thereby, the height of the trailing nozzle 1B is controlled.

In this way, groove tracing control in the X-axis and Y-axis directions of the trailing nozzle 1B, that is, in the groove width and height directions, is performed accurately every rotation of the trailing nozzle 1B.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to make the fillet weld bead of equal leg length, and moreover, it is possible to accurately control the groove tracing by the leading and trailing electrodes, and other extremely useful effects are brought about.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing fillet welding performed by the method of the present invention, FIG. 2 is a graph showing the relationship between leg length ratio and arc rotation speed, and FIG. A cross-sectional view of a weld bead with a protruding surface. FIG. 4 is a graph showing the relationship between the protrusion ratio of the weld bead surface and the rotational speed of the arc. FIG. 5 is a graph showing the relationship between the amount of spatter and the rotational speed of the arc. graph,
FIG. 6 is a cross-sectional view of a weld bead obtained by the method of the present invention, FIG. 7 is a block diagram of the method for controlling the groove tracing of a leading electrode in the present invention, and FIG. A front view showing a state in which the center axis is facing the center in the width direction of the groove, and Figure B is a front view showing a state in which the welding electrode is biased towards the horizontal plate side.
Figure C is a front view showing a state in which the welding electrode is biased toward the vertical plate side, and Figure 9A is a front view of the leading arc voltage when the rotation axis of the leading electrode is facing the center in the width direction of the groove. Figure B is a graph showing the change in leading arc voltage when the leading electrode is biased toward the horizontal plate. Figure C is a front view showing the state in which the leading electrode is biased toward the vertical plate. Figure, 10th
The figure is a plan view showing the rotational position of the welding electrode.
The figure is a block diagram of the trailing electrode groove tracing control method according to the present invention, and FIG. 12A shows the change in trailing arc voltage when the rotation center of the trailing electrode faces the center in the width direction of the groove. Figure B is a graph showing the change in trailing arc voltage when the trailing electrode is biased toward the horizontal plate, and Figure C is a graph showing the change in trailing arc voltage when the trailing electrode is biased toward the vertical plate. It is a graph showing a change in trailing arc voltage. In the drawings, 1A... Leading nozzle, 1B... Trailing nozzle, 2... Vertical plate, 3... Horizontal plate, 4A... Leading electrode, 4B... Trailing electrode, 5A... Lower layer bead, 5B...
Upper layer bead, 6... Leading arc voltage detector, 7... Switching device, 8... Controller, 9... Leading electrode position detector,
10... Peak voltage position detector, 11... Memory device, 1
2...X-axis driver, 13...X-axis motor, 14...
Integrator, 15...Memory, 16...Differential amplifier, 17
...Reference voltage setter, 18...Y-axis driver, 19
...Y-axis motor, 20...φ setting device, 21...n setting device.

Claims (1)

[Scope of Claims] 1 A leading nozzle is directed toward a groove formed by a vertical plate and a horizontal plate, a leading electrode is supplied along with a shielding gas toward the groove, and the leading nozzle is rotated at a predetermined radius. while generating a preceding arc between the preceding electrode and the groove to form a lower bead, on the upstream side of the preceding nozzle in the welding direction,
A trailing nozzle is provided at a distance from the leading nozzle, the trailing nozzle is directed toward the lower bead, a trailing electrode is supplied along with a shielding gas toward the lower bead, and the trailing nozzle is rotated at a predetermined radius. A trailing arc is generated between the trailing electrode and the lower layer bead while causing the trailing electrode and the lower layer bead to form an upper layer bead on the lower layer bead. Flesh welding, rotation speed of the preceding arc (N _L ): N ₀ ~ 120
Hz, Rotation diameter of the preceding arc (D _L ): 1 to 6 mm, Rotation speed of the trailing arc (N _T ): N ₀ , Rotation diameter of the trailing arc (D _T ): (W _L to 8
mm) and 1 mm, whichever is larger (W _L + 6 mm), the rotational direction of the trailing arc: when facing the welding progress direction and placing a vertical plate on the right side, from above the trailing nozzle Rotation to the right when viewed from above, and rotation to the left when viewed from above the trailing nozzle when the vertical plate is placed on the left side facing the direction of welding progress. Distance between the leading electrode and the trailing electrode: Depends on the leading arc. A period in which the leading crater and the trailing crater caused by the trailing arc do not overlap. However, N ₀ : The ratio of the vertical leg length (l ₁ ) to the horizontal leg length (l ₂ ) (l ₁ /l ₂ ) is the maximum. The rotating speed of the arc, W _L :width of the lower layer bead; Furthermore, the fluctuation value of any one of the voltage and current of the preceding arc is detected, and the most downstream position (C _f ) of the preceding electrode in the welding direction is detected. Detecting the position of the preceding electrode corresponding to the change point of the variation value within a predetermined range including, and moving the preceding electrode in the width direction of the groove based on a signal corresponding to the position of the preceding electrode, Furthermore, the fluctuation value is integrated over the predetermined range, the difference between the thus obtained integrated value (S _cf ) and the reference voltage (E ₀ ) is calculated, and the difference (S _cf −E ₀ ) is calculated. The leading nozzle is moved in the direction of its center axis so that Integrate over a predetermined range centering on the most downstream position (C _f ′), the rightmost position (R), and the leftmost position (L) in the welding direction of the electrode, and calculate the front integral value (S _cf ′) and the right integral value. value (S _R ) and left integral value (S _L )
and calculate the difference between the right side integral value (S _R ) and the left side integral value (S _L ) so that the calculated difference value (S _R −S _L ) matches the reference value. Move the trailing nozzle in the width direction of the groove, calculate the difference between the front integral value (S _cf ′) and a preset reference voltage (E ₀ ′), and calculate the difference between the front integral value (S cf ′) and a preset reference voltage (E 0 ′). A two-electrode rotating arc fillet welding method, characterized in that the trailing nozzle is moved in its axial direction so that the calculated value (S _cf '−E ₀ ') becomes zero.