JPH0461753B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a groove profile control method for high-speed rotating arc fillet welding using two electrodes.

[Conventional technology]

According to a welding method in which the arc is rotated by concentrically rotating the electrode nozzle at high speed, the physical effects of the arc are dispersed in the surrounding area, resulting in peripheral dispersion of penetration, formation of a flat bead (curved bead), or rotation. Benefits such as improved wire melting speed due to centrifugal force are obtained, and it is particularly effective when used in narrow gap welding of thick plates.

A welding method in which this high-speed rotating arc welding method is applied to downward horizontal fillet welding has been proposed by the applicant of the present application as a high-speed rotating arc fillet welding method (Japanese Patent Application No. 88732/1988).

FIG. 13 is a perspective view showing an overview of the above-mentioned high-speed rotating arc fillet welding method, in which 1 is an electrode nozzle, 2 is a rotary motor that rotates the electrode nozzle 1,
3 is a wire passing through the eccentric hole of the current-carrying chip provided at the tip of the electrode nozzle 1, 4 is an arc, 5 is a molten pool, 6 is a weld bead, 7 is a lower plate, and 8 is a standing plate installed on the lower plate 7. , 9 is the root of the groove.

In this high-speed rotating arc fillet welding method,
The electrode nozzle 1 is rotated by the rotary motor 2 at a rotation speed appropriate to the welding current and welding speed, thereby rotating the tip of the wire 3 and rotating the arc 4 to move the lower plate 7 and the vertical plate along the groove route 9. 8 is performed to form a weld bead 6 of equal length.

[Problem that the invention seeks to solve]

In the above high speed rotating arc fillet welding method,
Since the rotating diameter of the wire 3 is set in the range of 1 mm to 6 mm in order to obtain an appropriate penetration depth, it is difficult to form a bead with a large leg length by single electrode welding. Therefore, in order to form a long-legged bead at high speed, it is necessary to rotate at high speed the leading electrode and the trailing electrode, which are provided at equal intervals across the groove line.

In this case, if the positions of the leading electrode and the trailing electrode with respect to the groove line are even slightly shifted, welding defects will occur over a wide range. In order to prevent this welding defect from occurring, automatic alignment of the leading and trailing electrodes is essential.

This invention was made in response to such a need, and it is possible to perform profile control with high precision and in real time by utilizing the characteristics of the rotating arc itself without the need for any detector.
The purpose of this paper is to propose a groove profile control method for electrode fillet welding.

[Means for solving problems]

The groove tracing control method for two-electrode fillet welding according to the present invention involves arranging leading electrodes and trailing electrodes, whose torch positions are controlled by the same tracing mechanism, one behind the other, and at regular intervals across the weld line. , for each electrode nozzle of the leading electrode and trailing electrode, the rotation speed range is the lower limit of No (Hz) and the upper limit of 120 (Hz), assuming that the natural frequency of the molten pool due to the rotation of the arc is No (Hz). The rotating diameter of the wire tip of each electrode nozzle is 1 mm.
In fillet welding, which is performed by rotating the arc at high speed within a range of 6 mm from Divide the voltage waveform or current waveform of the leading electrode into a constant angle φ ₁ of 180° or less toward the lower plate based on the forward point Cf in the welding direction, and (c) Weld the voltage waveform or current waveform of the trailing electrode. Divide into a constant angle φ ₁ of 180° or less from the forward point Cf in the direction of travel to the standing plate side, and (d) Create the voltage waveform or current waveform of the preceding electrode divided to the lower plate side and the above constant angle φ ₁ . Calculate the area S _L and the area S _R created by the voltage waveform or current waveform of the trailing electrode divided into the standing plate side and the above constant angle φ ₁ , (e) Calculate the difference between the above areas S _L - _{S R} , Correct the positions of the leading electrode and trailing electrode in a direction perpendicular to the welding line so that this difference is equal to a predetermined reference value, and (f) adjust the voltage waveform or current waveform of the leading electrode and trailing electrode. Divide into fixed angles φ ₂ of 180° or less with the forward point Cf in the welding direction as the center, (g) Area S _l created by each voltage waveform or current waveform of the leading electrode and trailing electrode and the above fixed angle φ ₂ . , S _t , and (h) calculate the sum of the above areas S _l +S _t , and correct the heights of the leading and trailing electrodes so that this sum is equal to a predetermined reference value. This is a characteristic feature.

Here, the rotational speed range is defined as the natural frequency of the molten pool.
The reason for setting No (Hz) to 120Hz is as follows.

That is, in the high-speed rotating arc welding method, there is a phenomenon in which the weld bead is deflected to one side at a certain rotation speed. For example, welding current I
In narrow gap welding at = 300 A and welding speed v = 25 cm/min, this deflection phenomenon is most noticeable when the rotation speed is 7 (Hz). The direction of deflection of the bead is determined by the welding direction and the rotational direction of the arc, and if the rotational direction of the arc is clockwise, the bead will be deflected to the right of the welding direction.

This bead deflection phenomenon indicates that rotational vibration is also applied to the molten pool due to the rotation of the arc. This rotational vibration of the molten pool has also been confirmed by observation using a high-speed camera. The depression of the molten pool pushed down by the arc is at the front end of the crater when the arc is at the right end (R), and a large amount of molten steel is seen rising up in front of the arc in the rotation direction, while the arc is at the left end. When it is at (L), the depression extends gently behind the crater, and there is little molten steel rising up in front of the arc.
This is because the arc rotates near the tip of the molten pool. Therefore, the molten steel layer directly under the arc is thick at the R end and thinner at the L end, and this asymmetrical phenomenon of the molten pool causes the rotational speed of the arc to match the natural frequency No (Hz) of the molten pool. It is considered to be the most obvious at times.

This principle is the same for the horizontal fillet welding method, and in this case, in order to lift the molten steel to the vertical plate side against the gravity head of the molten steel, the drooping phenomenon of the bead is suppressed, and a good welding condition without welding defects is achieved. This results in long-legged beads. Since the rotational speed No. at which the bead is most deflected toward the vertical plate side increases as the welding speed increases, the upper limit was set at 120 (Hz) based on the welding speed.

Next, the reason why the rotating diameter of the arc is set to 1 to 6 mm is that if it is less than 1 mm, the signal necessary for groove contouring cannot be obtained, and if it exceeds 6 mm, the welding arc will spread wider than the width of the weld bead. This is because it becomes large and an undercut occurs.

In order to obtain a bead with long legs in fillet welding, this invention rotates each of the leading and trailing arcs at high speed at the above rotational speed and arc rotation diameter, and
With the configurations (a) to (h), highly responsive and highly accurate groove tracing control can be performed using the arc itself as a sensor.

[Effect]

In this invention, groove tracing control is performed based on fluctuations in the voltage waveform or welding current waveform of the rotating arc of the leading electrode and the trailing electrode, so highly responsive and highly accurate groove tracing is performed.

〔Example〕

FIG. 1 is a schematic configuration diagram showing a welding apparatus according to an embodiment of the present invention. In the figure, 10L is a leading electrode, 10T is a leading electrode 10L, and is spaced apart from the leading electrode 10L at a constant interval across the axis of the rotation transmission mechanism 11. , and is a trailing electrode provided behind the leading electrode 10L,
The leading electrode 10L and the trailing electrode 10T are both rotated by the rotary motor 2 in the direction of arrow A.

12 is an X-axis tracing mechanism that simultaneously corrects the leading electrode 10L and the trailing electrode 10T in the X-axis direction that is perpendicular to the root 9 of the groove, and 13 is the Y-axis direction that is the height direction of the leading electrode 10L and trailing electrode 10T. A Y-axis tracing mechanism that simultaneously corrects both electrodes 10L and 10T in the axial direction; 14 is a control device; 15 is a wire feeder that feeds wires to the leading electrode 10L and the trailing electrode 10T; and 16 is a cart. Note that FIG. 1 shows a case in which the profiling shaft is provided in the axial direction of the rotation transmission mechanism 11 and in the orthogonal axial direction.

FIGS. 2a and 2b show the state of bead formation when fillet welding is performed using the welding device configured as described above, in which the leading electrode 10L is biased toward the lower plate 7 side to form a bead 17, and the trailing electrode 10L The electrode 10T forms a bead 18 on the side of the standing plate 8 above the bead 17, behind the bead 17.

FIG. 3 is a side view showing the tip of the leading electrode 10L in which the rotational axis 19 is deviated from the route 9 by a distance of X ₁ in the X-axis direction, and the welding direction is perpendicular to the page, from the back of the page to the front. . In FIG. 3, la is the arc length, le is the wire protrusion length, and Ex is the distance between the leading electrode 10L and the lower plate 7. Cf,R,
L indicates the position of the wire 3 when the leading electrode 10L is rotating, and Cf indicates the position of the wire 3 in the forward direction in the welding direction.
, R indicates the position of the wire 3 on the right side by 90 degrees toward the welding direction, and L indicates the position of the wire 3 on the left side. FIG. 4 is a view of the leading electrode 10L shown in FIG. 3 viewed from the direction of the rotation axis 19, and Cr indicates the position of the wire 3 at the rear with respect to the welding direction 20.

As shown in FIGS. 3 and 4, the wire 3 is provided eccentrically with respect to the rotational axis 19 of the leading electrode 10L, and the leading electrode 10 is placed at a constant wire feeding speed.
When L is rotated around the rotation axis 19, the arc length la changes depending on the position of the wire 3 during rotation.
The distance Ex between the leading electrode 10L and the lower plate 7 changes.
When the distance Ex changes, the load characteristics change and the welding current I and arc voltage E change. This welding current I and arc voltage E differ depending on the characteristics of the welding power source. In FIG. 4, C indicates the rotation direction, θ indicates the rotation angle, and 20 indicates the welding direction.

Figures 5a and 5b show welding current I on the horizontal axis and arc voltage E on the vertical axis, and show the change characteristics of welding current I and arc voltage E according to changes in distance Ex.
b is the case where the characteristics of the welding power source are constant voltage characteristics, and b is the case where the characteristics are constant current characteristics. In Figures 5a and 5b, 31 is the output characteristic curve of the welding power source, and 32 is the load characteristic curve, which changes almost in parallel according to the values of distance Ex Ex ₀ , Ex ₁ , Ex ₂ as shown in the figure. . Note that the load characteristic curve 32 shows a case where Ex ₂ >Ex ₀ >Ex ₁ .

The operating point of the arc is the intersection of the output characteristic curve 31 and each load characteristic curve 32, and the welding current I and arc voltage E at that point are determined. That is, when the distance Ex decreases from Ex ₂ to Ex ₀ to Ex ₁ , the welding current I and arc voltage E become I ₂ , E ₂ , I ₀ , respectively.
It changes as E ₀ , I ₁ , and E ₁ . Note that in the case of the constant current power supply shown in Figure b, I ₀ = I ₁ = I ₂ .

A change in the welding current I or arc voltage E due to a change in the distance Ex changes in a linear relationship with the distance Ex unless the change in the distance Ex is large. As shown in FIG. 3, when the leading electrode 10L is inclined with respect to the lower plate 7, when the leading electrode 10L rotates, the distance Ex changes sinusoidally depending on the position of the wire 3.

FIGS. 6a and 6b show the waveforms of the arc voltage E and welding current I that change in accordance with the position of the wire 3 of the rotating leading electrode 10L, that is, the arc. In the figure, a is the waveform of arc voltage E, and b is the welding current I.
, and each waveform has an upside-down shape. Note that the waveform of welding current I shown in Figure b can be obtained only with a welding power source with constant voltage characteristics.
The fifth point is that the waveform of the arc voltage E can be obtained with either a welding power source with constant voltage characteristics or constant current characteristics.
It is clear from Figures a and b.

In FIGS. 6a and 6b, the waveforms indicated by broken lines indicate the case where the distance between the root 9 of the groove and the rotation axis 19 of the preceding electrode 10L is X ₁ , as shown in FIGS. 3 and 4, and the waveform indicated by the solid line The waveform shown in indicates the case where the distance between the root 9 and the rotation axis 19 is larger than _X1 .

The trailing electrode 10T has a similar relationship to the upright plate 8 as the preceding electrode 10L, and obtains the waveforms of the arc voltage E and welding current I shown in FIGS. 7a and 7b. In FIGS. 7a and 7b, the waveforms indicated by broken lines indicate the case where the distance between the root 9 of the groove and the axis of rotation of the trailing electrode 10T is _X1 , and the solid line indicates the case where this distance is smaller than _X1 .

Leading electrode 10L provided across groove route 9
Since the distance between the leading electrode 10L and the trailing electrode 10T is constant as shown in FIG. 1, if the distance between the rotation axis 19 of the leading electrode _10L and the groove root 9 is larger than and the root spacing is
ΔX is smaller than X ₁ , and Figure 6 a, b and 7
As shown by solid lines in FIGS. a and b, the levels of the arc voltage waveform or welding current waveform of the leading electrode 10L and the trailing electrode 10T change, respectively. That is, in this case, the level of the arc voltage waveform of the leading electrode 10L decreases, and the level of the arc voltage waveform of the trailing electrode 10T increases. Therefore, by detecting and correcting the amount of change in the level of the arc voltage waveform or welding voltage waveform of the leading electrode 10L and the trailing electrode 10T,
The amount of deviation ΔX in the axial direction can be corrected.

That is, as shown in FIGS. 6, 7, and 8, the waveform of the leading electrode 10L is taken out for a certain angle φ ₁ of 180° or less on the L side, which is the lower plate 7 side, with respect to the Cf point. Take out the waveform of the trailing electrode 10T from point Cf as a reference to the R side, which is the side of the standing plate 8, for a certain angle φ ₁ of 180° or less, and calculate the areas S _L and S _R of the waveform created between this angle φ ₁ . The deviation amount ΔX in the X-axis direction is corrected by the X-axis tracing mechanism 12 so that this area difference S _L −S _R becomes equal to a predetermined reference value Sx ₀ .

Here, the waveform extraction angle range is set at the leading electrode 10.
The reason why L is placed on the lower plate 7 side, the trailing electrode 10T is placed on the upright plate 8 side, and the angular range is within 180° is to make it easier to detect the lower plate 7 or the upright plate 8.

Next, distance control in the height direction, that is, the Y-axis direction, between the leading electrode 10L and the trailing electrode 10T will be explained.

Assuming the above-mentioned alignment in the X-axis direction, the positions of the leading electrode 10L and the trailing electrode 10T are the groove route 9.
When the arc voltage waveforms of the leading electrode 10L and the trailing electrode 10T are shifted by a distance ΔY so as to be separated from each other in the y-axis direction, the levels of the arc voltage waveforms of both the leading electrode 10L and the trailing electrode 10T become high, and the level of the welding current waveform becomes low. Therefore, as shown in FIG. 9, the waveforms of the leading electrode 10L and the trailing electrode 10T are
Take a certain angle φ ₂ from point Cf as the center, find the areas S _l and S _t of the waveform created by this angle, and adjust Y so that the sum of these areas S _l + S _t is equal to the predetermined reference value S _Y0 . Controls the axis tracing mechanism 13,
Correct the amount of deviation ΔY in the Y-axis direction. Here the angle φ ₂
shall be 180° or less.

In the above-mentioned tracing in the X-axis direction and tracing in the Y-axis direction, the reference values Sx ₀ and S _Y0 are set in advance corresponding to the appropriate positions of the leading electrode 10L and the trailing electrode 10T, but when the positions of the electrodes are at the appropriate positions. It is sufficient to store the values of the area difference S _L −S _R and the sum S _l +S _t of the waveforms.

Further, the values of the area difference Sx=S _L -S _R and the sum S _Y =S _l +S _t are the values of one rotation of the arc or an integral number n times.

The groove profile control method described above is shown in Figure 10.
Block diagram of axial profiling control circuit and 11th
The explanation will be made based on the block diagram of the profile control circuit in the Y-axis direction shown in the figure.

First, use the voltage detectors 50L and 50R to
The respective arc voltages E _L and E _R of L and trailing electrode 10T are detected. The detected arc voltage E _L of the leading electrode 10L is taken out by a certain angle φ ₁ on the L side by a switch 51L, and the arc voltage E _R of the trailing electrode 10T is taken out by a certain angle φ ₁ on the R side by a switch 51R.
The timing for taking out the angle φ ₁ in the switches 51L and 51R is determined by the switching logic circuit 52L,
This is done using a command signal from 52R. The switching logic circuits 52L, 52R are the rotational position detector 53L,
Leading electrode 10L and trailing electrode 10 detected by 53R
The rotation angle of T is compared with the output φ ₁ of the φ ₁ setters 54L, 54R, which are set at a predetermined constant angle φ ₁ of 180 degrees or less, for example, 90 degrees, and outputted as a command signal.

Each arc voltage output from the switches 51L and 51R is integrated over an angle φ ₁ by integrators 55L and 55R. The n setters 56L and 56R are set with the number of times n of these integrals are processed, and the integrator 55
L, 55R are respective switching logic circuits 52L, 5
Using n outputted through 2R, waveform integration is performed for n arc rotations, and the output S _L
and S _R are output to the memories 57L, 57R.
The memories 57L and 57R repeatedly store and hold the signals S _L and S _R input from the integrators 55L and 55R every n times, and output the signals S _L and S _R to the differential amplifier 58. The differential amplifier 58 calculates the difference between these signals Sx=S _L −
_{S _ _} The shaft motor 61 is driven.

On the other hand, as shown in FIG. 11, Y-axis direction tracing control also uses arc voltages E _L and E _R detected by voltage detectors 50L and 50R to be transferred to an integrator 75L via switches 71L and 71T, similar to the X-axis direction tracing control. ,75
T, the integral values S l and S t are integrated n times over a constant angle φ ₂ and each integral value S _l and S _t is stored in a memory. These S _l and S _t are added in an adder 78 to obtain S _Y = S _l + S _t , and this added value S _Y and the reference value S _Y0 set in advance in the reference value setter 80 are added in a differential amplifier 79. Compare this difference
The Y-axis motor 81 is driven so that S _Y −S _Y0 becomes zero, and the height in the Y-axis direction is controlled.

In the above embodiment, as shown in FIG. 1, the Y-axis direction of the profiling axis coincides with the rotational axis direction of each electrode, but as shown in FIG. The X axis parallel to
If it consists of a Y axis orthogonal to the axis, or the lower plate 7
Even in the case of an X-axis parallel to the axis of rotation and a Y-axis in the direction of the rotation axis, groove tracing control can be performed in the same manner as in the above embodiment.

Furthermore, although the control circuit of the above embodiment has been described for the case where the arc voltage waveform is detected, even when the welding current waveforms shown in FIGS. can be controlled.

〔Effect of the invention〕

As explained above, this invention detects the arc voltage waveform or welding current waveform of the rotating leading electrode and trailing electrode, and performs groove tracing control based on the detected waveforms, so the groove can be directly detected. This eliminates the need for a detector and enables the formation of beads with long legs with high precision.

In addition, since groove tracing control is performed based on the position of the arc itself, it is possible to correct the position of the arc in real time.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a welding apparatus according to an embodiment of the present invention, FIGS. 2a and 2b are explanatory diagrams of a bead formed by the above embodiment, and a is a front view;
b is a perspective view seen from the side, FIG. 3 is a side view showing the tip of the preceding electrode of the above embodiment, FIG. 4 is a wire arrangement diagram seen from the rotational axis direction of the preceding electrode shown in FIG. 3, Figure 5 a and b show the characteristics of the welding power source, a
is a constant voltage characteristic diagram, b is a constant current characteristic diagram, FIG. 6 a is an arc voltage waveform diagram of the leading electrode, b is a welding current waveform diagram of the leading electrode, FIG. 7 a is an arc voltage waveform diagram of the trailing electrode, b is a welding current waveform diagram of the trailing electrode, Fig. 8 is an explanatory diagram of the X-axis direction profiling control, Fig. 9 is an explanatory diagram of the Y-axis direction profiling control, and Fig. 10 is a block diagram of the X-axis direction profiling control circuit. , FIG. 11 is a block diagram of a Y-axis direction profiling control circuit, FIG. 12 is a schematic configuration diagram showing another embodiment, and FIG. 13 is a perspective view showing an outline of high-speed rotating arc fillet welding. 2... Rotating motor, 7... Lower plate, 8... Vertical plate, 9... Bevel root, 10L... Leading electrode, 10T... Trailing electrode, 12... X-axis tracing mechanism, 13... Y-axis tracing mechanism.

Claims (1)

[Claims] 1. Electrode nozzles of a leading electrode and a trailing electrode, which are arranged one behind the other at the bottom of the same groove tracing movement mechanism and are attached at regular intervals across the welding line, have rotational speed ranges within an arc. If the natural frequency of the molten pool due to the rotation of is No (Hz), then the lower limit is No (Hz) and the upper limit is No (Hz).
120 (Hz) range, and the rotating diameter of the wire tip of each electrode nozzle is in the range of 1 mm to 6 mm. In fillet welding, which is performed by rotating the arc at high speed, (a) the above-mentioned rotating leading electrode and Detect the arc voltage waveform or welding current waveform of the trailing electrode, and (b) move the voltage waveform or welding current waveform of the preceding electrode toward the lower plate at a constant angle φ1 of 180° or less with respect to the forward point Cf in the welding direction. (c) Divide the voltage waveform or welding current waveform of the trailing electrode mentioned above into a constant angle φ1 of 180° or less toward the vertical plate side from the forward point Cf in the welding direction, and (d) Lower plate side. The area created by the voltage waveform or welding current waveform of the preceding electrode divided into and the above constant angle φ1
Calculate the area SR created by the voltage waveform or welding current waveform of the trailing electrode divided into SL and the standing plate side and the above constant angle φ1, (e) Calculate the difference SL - SR between the above areas, and this difference is Correct the positions of the leading electrode and trailing electrode in a direction perpendicular to the welding line so that they are equal to the predetermined reference value; Divide into constant angles φ2 of 180° or less with point Cf as the center, (g) Area Sl, St created by each voltage waveform or welding current waveform of the leading electrode and trailing electrode and the above constant angle φ2.
(h) A two-electrode corner characterized in that the sum of the areas Sl+St is calculated, and the heights of the leading electrode and the trailing electrode are corrected so that this sum is equal to a predetermined reference value. Groove profile control method for meat welding.