JPH0819863A - Automatic copying method for welding line - Google Patents

Abstract

PURPOSE:To precisely detect a groove shape of a base material by generating an arc with a minute current while oscillating a plasma arc torch, obtaining the positional information of a welding line from the change of the plasma voltage in this time, and copying the welding torch from the groove. CONSTITUTION:A welding detecting sensor is arranged at the front side of the welding advancing direction to the welding electrode, and the welding electrode is copied from the welding line detected with this sensor. A plasma arc torch 23 is installed at the front side of the welding torch 24, and a plasma arc 15 of a minute current of a degree so as not to melt a base material is generated toward the base material 16, 17 from the plasma torch 23. The plasma arc 15 is oscillated by a prescribed amplitude in the direction crossing the welding line of the base material and preceded to the welding line direction, the positional information of the welding line is detected from changing of the arc voltage of the plasma arc 15, and the welding electrode is corrected to the prescribed position to the welding line based on the detected positional information. Therefore, the precise copying of the welding line can be realized without receiving the disturbance of the light of welding, etc., even if it is installed nearby the welding torch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention proposes a welding line automatic copying method for satisfactorily following the welding line.

[0002]

[Prior art]

(Prior Art 1) As a welding line automatic copying method, a welding torch is oscillated at a constant amplitude in a direction orthogonal to the welding line, and a welding current and a torch are changed by a change in welding current generated when a welding arc crosses the welding line. Has been proposed that detects a difference from the center position of the oscillator. FIG.
2 and FIG. 2 are views for explaining a state when the welding line copying method as described above is performed.

In FIG. 1, 1 is a welding torch, 2 is a welding electrode, 3 and 4 are base materials, and FIG. 2 shows the position of the welding torch 1 when the welding torch 1 is oscillated as shown in FIG. And a change in welding current. The horizontal axis represents the oscillating position when the center of the oscillate is the center of the diagram, and the vertical axis represents the welding current value corresponding to the oscillating position.

In FIG. 1, when welding is performed while oscillating the welding torch 1 in the direction orthogonal to the welding line with respect to the welding line, the welding current is the welding electrode 2 and the base metal (3 and 4). ) Changes with the distance between. When the oscillating center position of the welding torch changes with respect to the welding line as shown in FIGS. 1 (a) to 1 (c), the detected welding current is as shown in FIGS. 2 (a) to 2 (c).

In FIG. 2, the welding current detected during welding is divided into right and left with respect to the center of the oscillation, the area on the left side that integrates the welding current is designated as S1, and the area on the right side that integrates the welding current is designated as S2. Let E be the detected value of the welding current at the center, and Eo be the signal corresponding to the reference position in the height direction of the welding electrode with respect to the base material.

During welding, the difference between S1 and S2 (S1 −
When S2) is zero, it is determined that welding is performed on the welding line, and when (S1 -S2) is not zero, it is determined that the welding line is displaced. If there is a deviation, (S1-S
The welding torch 1 is moved laterally according to the value of 2) and its sign, and the position is corrected so that (S1−S2 = 0).

When it is desired to set the position shifted by a predetermined distance in the oscillating direction with respect to the welding line as the target position of the welding torch 1, the value of (S1-S2) at the position shifted by a predetermined position from the welding line is set in advance. If the calculated value is So, the position may be corrected so that (S1−S2 = So).

Further, when the difference between E and Eo (E-Eo) is zero, it is judged to be the reference height, and when it is not zero, it is judged not to be the reference height, and (E-Eo) and its The welding torch 1 is moved in the height direction according to the symbols and (E-Eo =
The position is corrected so that it becomes 0).

(Prior Art 2) Further, as shown in FIG. 3 and FIG. 4, the welding torch 1 moving along the welding line is brought close to the welding torch 1 on both sides in the groove width direction and the tip thereof is provided. Generates a small current auxiliary arc by the two non-consumable auxiliary electrodes 5a and 5b arranged so as to face the tip of the welding electrode 2 and detects this arc voltage to detect the difference between the two arc voltages. Accordingly, the welding torch 1 and the auxiliary electrodes 5a, 5
By correcting the position of b in the groove line width direction and comparing the average value of the two arc voltages of the auxiliary electrodes 5a and 5b with the reference height signal, the welding torch 1 and the auxiliary electrode 5 are compared.
There is one that controls the height of a and 5b. (For example, Japanese Patent Laid-Open Publication No. Sho 60-29587)

In FIG. 3, the welding torch 1 welds to the base materials 3 and 4 regardless of the detection of the arc voltage.
The auxiliary electrodes 5a and 5b are different welding power sources 6a and 6 respectively.
Using b, with a small current value that does not dissolve the base material,
As shown in FIG. 4, arcs are generated at the positions 9 and 10 near the target position 8 of the welding torch 1, and the respective arc voltages are detected. Here, the arc voltage detected by the auxiliary electrode 5a is E1, and the arc voltage detected by the auxiliary electrode 5b is E2.

When the difference (E1-E2) between the two detected welding voltages E1 and E2 is zero, the welding torch 1 is on the welding line, and when (E1-E2) is not zero, the welding torch 1 deviates from the welding line. Determine that In this case, the welding torch 1 and the auxiliary electrodes 5a and 5b are moved in the groove width direction according to the value of (E1-E2) and its sign, and (E1-E2 =
Correct the position so that it becomes 0). Furthermore, detected 2
Average of two welding voltages E1 and E2 (E1 + E2) / 2
And the difference ((E1 + E2) / 2-Eo) between the preset reference height signal Eo and zero is determined to be the reference height, ((E1 + E2) / 2-Eo). When is not zero, it is judged that it is not the standard height, and ((E1 + E2) / 2
The welding torch 1 and the auxiliary electrodes 5a and 5b are moved in the height direction according to the value of −Eo) and its sign, and ((E
The position is corrected so that 1 + E2) / 2-Eo = 0).

(Prior Art 3) FIG. 5 is a view showing another prior art, in which the leading torch 1a is directed to the groove formed by the vertical plate 3 and the horizontal plate 4, and the leading electrode 2a is directed toward the leading torch 1a. To the groove by eccentric from the center line, supplied with the shield gas, while rotating the leading torch 1a, generate a leading arc between the leading electrode 2a and the groove to form the lower layer bead 7a, A trailing torch 1b is provided on the upstream side of the leading torch 1a in the welding advancing direction at a distance from the leading torch 1a, the trailing torch 1b is directed toward the lower bead 7a, and the trailing electrode 2b is offset from the centerline axis of the trailing torch 1b. And the shield gas is supplied to the lower bead 7a together with the shield gas, and the trailing electrode 2b and the lower bead 7 are rotated while rotating the trailing torch 1b.
It is a figure which shows the two-electrode rotary arc fillet welding method which produces | generates a trailing arc between a and a, and forms upper layer bead 7b on lower layer bead 7a. (For example, Japanese Patent Laid-Open Publication No. Sho 62-
(158568)

In the prior art of FIG. 5, the rotation speed of the leading arc, the rotation diameter of the leading arc, the rotation direction of the leading arc (right rotation or left rotation), the rotation speed of the trailing arc, the rotation diameter of the trailing arc, and the trailing arc. By setting the rotation direction (right rotation or left rotation) of the row arc and the interval between the leading torch 1a and the trailing torch 1b to optimal values, a weld bead cross section with a large leg length as shown in FIG. 6 can be obtained.

FIG. 6 is a diagram showing the movement loci of the electrodes 2a and 2b of the prior art shown in FIG. In the figure, Cf is the foremost point in the welding advancing direction of the rotating position of the leading electrode 2a, Cr is the rearmost point in the welding advancing direction of the leading electrode 2a,
R is the point when the leading electrode 2a comes closest to the vertical plate 3, L
Is the point when the leading electrode 2a comes closest to the horizontal plate 4, C
f'is the most forward point of the welding direction of the trailing electrode 2b, Cr '
Is the rearmost point in the welding direction of the trailing electrode 2b, R'is the point when the trailing electrode 2b comes closest to the vertical plate 3, and L'is the point when the trailing electrode 2b comes closest to the horizontal plate 4. It is a point.

FIGS. 8 and 9 are views for explaining the manner of welding line copying in the prior art of FIGS. 5 and 7. When the positions of the central axes of the leading torch 1a and the trailing torch 1b are changed with respect to the groove position as shown in FIGS. 8A to 8C, the relationship between the welding line, the torch, and the electrode is shown in FIG.
As shown in FIGS. 9A to 9C, the detected arc voltage becomes as shown in FIGS. 9D to 9F with respect to the rotation angle of the electrode.

During welding of the leading electrode 2a, the leading electrode 2a
Is detected and the left-side integrated value S1 and the right-side integrated value S2 (S1 -S2) obtained by integrating the left and right predetermined rotational angles centered on the rotational position Cf are zero. When, the leading torch 1a is placed on the welding line.
It is determined that there is a central axis line of the above, and when (S1 -S2) is not zero, it is determined that it is deviated from the welding line. In this case, the leading torch 1a is moved laterally according to the value of (S1 -S2) and its sign, and the position is corrected so that (S1 -S2 = 0). Further, when the difference (S1 + S2-Eo) between the sum (S1 + S2) of the left-side integrated value S1 and the right-side integrated value S2 and the preset reference signal Eo is zero,
It is the reference height, and when (S1 + S2-Eo) is not zero, it is determined that it is not the reference height, and the leading torch 1a is moved in the height direction by the value of (S1 + S2-Eo) and its sign, The position is corrected so that (S1 + S2-Eo = 0). Further, the trailing torch 1b also performs the same processing as the leading torch 1a, and corrects the position in the lateral direction and the height direction.

(Prior Art 4) In Prior Art 3,
When the rotation diameter of the trailing electrode 2b is increased, a two-layer bead as shown in FIG. 10 is obtained. (For example, Japanese Patent Laid-Open Publication No. Sho 62-230485)

In this case, the control method of the leading torch 1a in the groove width direction and the height direction is the same as that of the prior art 3,
The bead welded by the leading electrode 2a has a substantially averaged bead cross section as shown in FIG.
When the position of the trailing nozzle 2 with respect to the lower bead 7a is changed as in 1 (a) to (c), the relationship between the lower bead 7a of the welding line and the trailing electrode 2b is shown in FIGS. As shown in FIG. 12C, the arc voltage detected by the trailing electrode 2b is as shown in FIGS.

In FIGS. 12D to 12F, Sc
f'is an area obtained by integrating the trailing arc voltage by a preset predetermined rotation angle around the rotation position Cf 'of the trailing electrode 2b, and S1' is centered around the rotation position L'of the trailing electrode 2b. Is the area obtained by integrating the arc voltage of the trailing electrode by a predetermined rotation angle set in advance,
S2 'is the area obtained by integrating the arc voltage of the trailing electrode by a preset predetermined rotation angle around the rotational position R'of the trailing electrode 2b, and Scr' is the trailing electrode 2b.
This is an area obtained by integrating the trailing arc voltage by a predetermined rotation angle set in advance with the rotation position Cr ′ as the center.

During welding of the trailing electrode 2b, the lower integrated value S
The difference between 1'and the upper integrated value S2 '(S1'-S2
') Is the preset reference value So, there is the trailing torch 1b at the desired position, and when (S1'-S2') is not the reference value So, it is judged that it is displaced from the desired position. . In this case, the trailing torch 1b is moved laterally by the value of (S1 '-S2') and its sign,
The position is corrected so that (S1'-S2 '= So). Furthermore, when the difference (Scf′−Eo ′) between the front side integrated value Scf ′ and the preset reference signal Eo ′ is zero,
When the trailing torch 1b has a reference height with respect to the lower layer bead 7a and (Scf'-Eo ') is not zero, it is determined that the height is not the reference height, and the value of (Scf'-Eo') and its sign. By moving the trailing torch 1b in the height direction, (Sc
The position is corrected so that f'-Eo '= 0). In addition, instead of the front integrated value Scf ′, the rear integrated value Scr ′
May be used.

(Prior Art 5) Further, for the welding electrode,
There is also a method in which a contact type sensor such as a roller is provided in front of the welding advancing direction as a sensor capable of recognizing the welding line and the welding electrode is made to follow the welding line by the detection signal of the sensor.

(Prior Art 6) Furthermore, a CCD camera or the like is provided as a sensor for recognizing a welding line in the forward direction of welding, a video signal from this camera is processed to obtain a welding line position signal, and this welding is performed. There is also a method of causing the welding electrode to follow the welding line by the line position signal.

[0023]

In the prior art 1, since the electrode used for the arc sensor is the same as the welding electrode, the groove shape is changed because the base metal is melted by the welding electrode. The change in welding current makes it difficult to detect the groove position. In particular, in welding a lap joint of a thin plate, if the welding line is traced by the method of the prior art 1, the entire groove is completely melted, so that the shape of the groove cannot be detected. Further, the welding conditions and the characteristics of the welding power source have a great influence on the sensor signal, and if the welding conditions and the characteristics of the welding power source change, the copying operation becomes unstable.

Further, in the prior art 2, it is premised that the arcs generated by the two auxiliary electrodes have the same welding voltage under the same conditions. However, in reality, due to the characteristics of the welding power source and the consumption of the electrodes, even if the same conditions are set, the same welding voltage is extremely rare. In addition, the arc generated by the two auxiliary electrodes 5a and 5b is shown in FIG.
Since it arrives at the base materials 3 and 4 with a certain degree of spread as described above, even if there is a small shape change on the base material side, it enters the spread of the arc and is difficult to detect. Therefore, it was difficult to follow the welding line in the thin plate lap joint as shown in FIG.

Also in the prior art 3 and the prior art 4,
Since the actual welding electrode is used as a sensor, it has the same problem as the above-mentioned conventional technique 1.

In the prior art 5, the surface condition of the sensor contact portion on the welded plate has a large influence, and the scanning accuracy depends on the presence or absence of spatter. Further, since the contact portion is composed of a roller or the like, the smoothness of its mechanical movement also affects the copying accuracy.

In the prior art 6, the influence of intense arc light, heat, spatter, fumes, etc. at the time of welding was great, and the copying accuracy could not be improved.

[0028]

According to the welding line automatic copying method of the present invention, a plasma arc torch is arranged in front of a welding electrode in a welding advancing direction, and an oscillating operation is performed across the plasma arc torch. While generating, an arc is generated by a minute electric current that does not melt the base material,
This is a method of following the welding torch by obtaining the position information of the welding line from the change in the plasma arc voltage at this time.

According to a second aspect of the present invention, in the welding line automatic copying method according to the first aspect, the working gas necessary for generating the plasma arc used for detecting the position information of the welding line is the same as the shielding gas used for the welding electrode. It is a method using a kind or an inert gas or CO2 gas.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The automatic copying method of the present invention will be described below with reference to the drawings. The apparatus for generating a plasma arc used in the welding line copying method of the present invention is similar to the apparatus used for known plasma arc cutting or welding. FIG. 14 shows an example thereof. In FIG. 14, 11 is an electrode, 12 is a nozzle, 13 is a working gas, 14 is a liner, 1
Reference numeral 5 is a plasma arc, 16 and 17 are base materials, 18 is a plasma arc power supply device, 19 is a pilot arc power supply device, 20 is a high frequency generator, 21 is a pilot arc starting switch, and 22 is an arc voltage detector. is there. Here, as the power supply device 19 for the pilot arc and the power supply device 18 for the plasma arc, a power supply device having a drooping characteristic or a constant current characteristic is used.

In the apparatus shown in FIG. 14, first, the switch 21
And a working gas 13 is made to flow in the nozzle 12, a high frequency high voltage from the high frequency generator 20 is superimposed on the output of the pilot arc power supply device 19 and supplied between the electrode 11 and the nozzle 12. By doing so, the insulation between the electrode 11 and the nozzle 12 is destroyed and a pilot arc is generated between the electrode 11 and the nozzle 12, and then the high frequency generator 2
The high frequency caused by 0 is stopped. This pilot arc is blown out from a small hole opened in the nozzle 12 by the working gas 13 flowing in the nozzle 12, and the base materials 16, 17
At that point, the insulation between the electrode 11 and the base materials 16 and 17 is destroyed, and the plasma arc power supply device 18 causes a plasma to pass through a small hole formed in the nozzle 12 between the electrode 11 and the base materials 16 and 17. Arc 15 is generated. When the plasma arc 15 is generated, the switch 21 is released and the pilot arc is stopped. In addition, the electrode 11 and the base material 16,
The arc voltage of the plasma arc 15 generated between the arc voltage detector 17 and the plasma arc detector 17 is detected by the arc voltage detector 22.

Further, as another example of the apparatus for generating the plasma arc by the plasma arc system, there is one as shown in FIG. In the figure, 11 is an electrode, 12 is a nozzle, 13 is a working gas, 14 is a liner, 15 is a plasma arc, 16 and 17 are base materials, 18 is a plasma arc power supply,
20 is a high frequency generator and 22 is an arc voltage detector.
In the case of the apparatus of the same figure, unlike the apparatus of FIG. 14, there is no pilot arc power source 19, so first of all the nozzle 12 and the base material 1
6 and 17 are kept in contact with each other, and the working gas 13 is supplied to the nozzle 12
In the state of flowing inside, high frequency is supplied between the electrode 1 and the base materials 16 and 17 by the high frequency generator 20 to perform dielectric breakdown between the electrode 11 and the nozzle 12, and the plasma arc power supply device 18 is used. After inducing the plasma arc 15 between the electrode 11 and the base materials 16 and 17, the high frequency generated by the high frequency generator 20 is stopped. After this, the nozzle 2 is attached to the base material 1
When separated from Nos. 6 and 17, the plasma arc 15 grows through the small holes formed in the nozzle 12 between the electrode 11 and the base materials 16 and 17 by the action of the working gas 13. Also, the electrode 11
Plasma arc 15 generated between the base material and the base materials 16 and 17
The arc voltage of is detected by the arc voltage detector 22.

Further, in the present invention, as a plasma arc,
It is also possible to use an apparatus as shown in FIG. 16 that generates a plasma arc by a method that does not use a pilot arc.
In the figure, 11 is an electrode, 12 is a nozzle, 13 is a working gas, 14 is a liner, 15 is a plasma arc, 16 and 1.
Reference numeral 7 is a base material, 18 is a plasma arc power supply, 20 is a high frequency generator, and 22 is an arc voltage detector. First, with the working gas 13 flowing in the nozzle 12, the high frequency generator 20
Thereby, a high frequency is supplied between the electrode 11 and the nozzle 12 to cause a dielectric breakdown between the electrode 11 and the nozzle 12, and the plasma arc power supply device 18 causes the electrode 11 and the nozzle 12 to be discharged.
After the plasma arc 15 is generated between and, the high frequency generated by the high frequency generator 20 is stopped. The plasma arc 15 is generated by the action of the working gas 13 flowing in the nozzle 12 from a small hole formed in the nozzle 12 to the nozzle 1.
2 can be blown out to reach the base materials 16 and 17. Further, the arc voltage of the plasma arc 15 generated between the electrode 11 and the base materials 16 and 17 is detected by the arc voltage detector 22.

In general, the arc discharge column has a self-adjusting function that tries to minimize the dissipation of heat when it is forcibly cooled from the outside, which reduces its cross-sectional area and causes its temperature to rise rapidly. It has the property of doing (thermal pinch effect). In the case of the apparatus of FIGS. 14 to 16, the plasma arc 15 is cooled by the nozzle 12 and the flow of the working gas 13, and the arc cross-sectional area is reduced by the thermal pinch effect. It becomes plasma arc 15. The generated plasma arc 15 is suppressed to a spread of about 1/4 or less as compared with the arc of TIG welding. Therefore, the arc voltage detector 2
The arc voltage of the plasma arc 15 detected at 2 will indicate the voltage between the electrode 11 and the very local parts of the base materials 16,17. Further, the plasma arc 15 is strong against disturbance, and even if the plasma arc 15 is generated near the welded portion, it is hardly affected by welding arc light, spatter, fumes and the like.

Since the plasma arc used in the present invention is not intended to be welded by itself, it is necessary that the plasma arc current has a value as low as possible within a limit in which the plasma arc can be stably maintained. is there. The value depends on the structure of the plasma torch, but it is generally 1 to 1
It is about 5 amps and can be reduced to about 0.1 amps when using a specially made torch. Further, when the power source device for plasma arc is devised and a pulsed current is used, by sampling the voltage at the pulse peak current, it is possible to detect a stable voltage even at a lower average current.

In the device as shown in FIGS. 14 to 16, the electrode 1 is used.
When the plasma arc 15 is generated while changing the distance between 1 and the base materials 16 and 17, and the plasma arc voltage at that time is detected by the arc voltage detector 22, as shown in FIG.
The arc voltage increases in proportion to the distance between 1 and the base materials 16 and 17. Further, since the cross-sectional area of the arc column is extremely small due to the effect of the above-mentioned thermal pinch effect, it is possible to detect the arc voltage accurately proportional to the change in the groove shape of the base material.

For example, grooves A, B, as shown in FIG.
When the plasma arc 15 is generated while moving the electrode 11 across the groove in the direction of the arrow with respect to the base materials 16 and 17 having C, the output of the arc voltage detector 22 is as shown in FIG. As shown in, the arc voltage that changes corresponding to the shape of the base material is detected. 18B, A, B, and C correspond to the positions of the groove portions A, B, and C of the base materials 16 and 17 of FIG. 18A, respectively.

Further, when the plasma arc 15 is generated while the electrode 11 is moved across the groove in the direction of the arrow with respect to the base materials 16 and 17 for abutment having almost no gap as shown in FIG. As shown in FIG. 19B, a portion where the arc voltage suddenly changes appears at the groove position D, and this is determined to be the groove position.

In the present invention, in order to detect the position of the welding line in the oscillating direction from the arc voltage of the plasma arc 15 detected by the arc voltage detector 22 during the oscillating operation of the plasma electrode 11, the plasma arc 15 detected during the oscillating operation is used. The arc voltage is divided into right and left with respect to the center of the oscillation, and the position of the welding line in the oscillating direction is detected by comparing the area obtained by integrating the arc voltage on the left side with the area obtained by integrating the arc voltage on the right side. FIG. 20 is a diagram for explaining a method of detecting the position of the welding line as described above.

In FIG. 20, (a) to (e) show the positional relationship between the oscillating position of the plasma arc and the welding line of the base metal, and (f) to (j) of FIG. It is a diagram showing the relationship between the position of the electrode 11 and the change of the arc voltage when the plasma arc is oscillated in the positional relationship as shown in e), where the horizontal axis is the oscillating position and the vertical axis is the arc corresponding to the oscillating position. Indicates the voltage value.

Here, FIGS. 20 (a) and 20 (f) show that when the oscillating center position of the electrode 11 is on the welding line, FIG.
20 (b) and 20 (g), when the oscillating center position of the electrode 11 is between A and B and there is a welding line in the oscillating amplitude range, FIGS. 20 (c) and 20 (h) show the oscillating center of the electrode 11. When the position is between A and B and there is no welding line in the oscillating amplitude range, FIGS. 20 (d) and (i) show that the oscillating center position of the electrode 11 is between B and C, and When there is a welding line, FIGS. 20 (e) and (j) show the case where the oscillating center position of the electrode 11 is between B and C and there is no welding line in the oscillating amplitude range.

In FIG. 20, the arc voltage of the plasma arc 15 detected during welding is divided into the right and left with respect to the center of the oscillate, the area integrating the arc voltage on the left side is S1, and the area integrating the arc voltage on the right side is S2
When the plasma arc is on the welding line, the difference between the two areas (S
1-S2) becomes zero and shifts to the left with respect to the welding line, (S1-S2) <0, and when shifts to the right with respect to the welding line, (S1-S2)> 0. It turns out that

Here, there is a relationship as shown in FIG. 21 between the value of the area difference (S1 -S2) and the distance from the electrode to the welding line. In FIG. 21, the vertical axis represents the value of (S1-S2),
The horizontal axis shows the center position of the oscillate with respect to the welding line,
The range from point D to the left corresponds to the electrode position in FIG.
The range from point D to point B corresponds to the electrode position in FIG. 20 (b), the point B corresponds to the electrode position in FIG. 20 (a), and the range from point B to point E is the electrode in FIG. 20 (d). The position corresponds to the position, and the range from the point E to the right corresponds to the electrode position in FIG. Therefore, if this relationship is investigated in advance, (S1 −
The positional relationship between the electrode and the welding line can be known from the value of S2). Further, when the position displaced from the welding line by a predetermined distance in the oscillating direction is set as the target position and the distance between the electrode and the target position is to be obtained, the value So of (S1-S2) at the target position is obtained in advance. By the way, (S1-S2 =
If So), it may be determined that the electrode is on the target position.

The electrode 1 is detected by detecting the arc voltage at the center of the oscillation of the plasma arc 15 detected during the oscillating operation of the plasma electrode 11.
The height of one of the base materials 16 and 17 can be measured. In FIG. 20, when the arc voltage of the plasma arc 15 at the oscillating center is E, the height of the electrode 11 with respect to the arc voltage E with respect to the base material can be obtained from the relationship shown in FIG.

In FIG. 22, the position of the welding line is detected by the above method, and the welding torch installed after the plasma torch is made to follow the welding line based on the detected position information of the welding line. It is an example of the apparatus which implements the welding line copying method of this invention.

In FIG. 22, 23 is a plasma torch,
Reference numeral 24 is a welding torch, 25 is a driving device for driving the plasma torch, 26 is a detector of the oscillating position of the plasma torch, 27 is a plasma controller for controlling the plasma torch driving device, and 28 is a welding torch. Welding power source, 29 is a drive device for driving the welding torch, 30 is a welding control device for controlling the welding torch drive device and the welding power source for welding, and 31 is information on arc voltage and oscillating position. A memory, 32 is an arithmetic circuit for calculating the position of the welding line based on the data stored in the memory 31, and 33 is a memory for storing the position of the welding line obtained by the arithmetic circuit 32. Reference numeral 34 is a welding torch position detector, and 35 is a power supply device for generating a plasma arc.

The operation trajectory of the plasma torch 23 is taught in advance, and the teaching data is stored in the controller 27 for the plasma torch 23. During automatic operation, the plasma torch 23 operates on the taught operation locus, and generates the plasma arc 15 along the welding line while oscillating in the direction traversing the welding line with the operation locus as the oscillating center position. At that time, the arc voltage of the plasma arc 15 is detected by the arc voltage detector 22 and stored in the memory 31 at a preset sampling interval.

At this time, the oscillating position of the plasma torch 23 is simultaneously detected by the detector 26 and stored in the memory 31 as a pair of data together with the detected arc voltage value of the plasma arc 15. When the arc voltage and the oscillating position for one oscillation are stored in the memory 31, the position of the welding line is calculated by the arithmetic circuit 32 by the method described above. Here, since the position of the welding line obtained from the calculation result is the deviation amount with respect to the taught movement trajectory,
The position data corrected by the position data of the welding line calculated by detecting and calculating the position data of the taught motion locus as described above is taken as the actual position of the welding line, and this position data is stored in the memory 33.
I will remember.

The welding torch 24 is installed on a carriage (not shown) which moves in the welding line direction with a delay of a certain distance L from the plasma torch 23, and moves in the welding line direction at the same speed as the plasma torch 23 at the same speed. The control device 30 of the welding torch 24 reads the position data of the welding line stored in the memory 33 with a delay of the separation distance L from the plasma torch and compares it with the detected value of the welding torch position detector 34 to compare the welding torch 24 with the detected value. The position is controlled in the direction crossing the welding line so that the position is stored in the memory 33. At this time, if it is desired to position the welding torch 24 at a position that is offset by a desired distance from the welding line instead of the center of the welding line, the position data stored in the memory 33 is controlled by the welding torch 24. The correction may be made by the device 30 or may be programmed so as to obtain a desired displacement amount when the calculation is performed by the calculation circuit 32.

The plasma torch 23 and the welding torch 2
4 is too close to each other, the working gas of the plasma torch 23 disturbs the flow of the welding shield gas by the welding torch 24, which may deteriorate the shielding property for the welded portion necessary for the welding quality and deteriorate the welding quality. In order to prevent this, it is necessary to set the distance L between the plasma torch 23 and the welding torch 24 to a distance at which the working gas does not disturb the flow of the welding gas. The minimum distance between the plasma torch 23 and the welding torch 24 is determined by the flow rate of the working gas for plasma and the diameter (orifice diameter) of the outlet of the plasma arc of the plasma nozzle 12, but generally the flow rate of the working gas. As the number of holes increases and the diameter of the orifice decreases, the distance between the plasma torch 23 and the welding torch 24 must be increased.

If the working gas 13 used for the plasma torch 23 is the same type as the welding gas or an inert gas or CO2 gas, the shielding property is less likely to deteriorate even if the flow of the welding shield gas is disturbed. Since the deterioration of the welding quality can be prevented, the space between the plasma torch 23 and the welding torch 24 can be reduced.

In the apparatus shown in FIG. 22, the plasma torch 23 and the welding torch 24 are installed on the same carriage,
The plasma torch 23 and the welding torch 24 may be separated by a distance L and moved by separate moving means. In this case, the plasma torch 23 may once detect all the welding lines, and then the welding torch 24 may follow the detected welding lines to perform welding. In this case, two robot manipulators may be used to separately handle the plasma torch 23 and the welding torch 24. It is also possible to control the plasma arc control device 27 and the welding control device 30 by one.

[0053]

According to the automatic welding line copying method of the present invention, a plasma arc torch is disposed in front of the welding electrode in the welding advancing direction, and the plasma arc torch is oscillated while crossing the welding line. , It is a method of generating an arc by a minute current that does not melt the base metal, and obtaining position information of the welding line from the change in plasma voltage at this time to follow the welding torch, so the groove shape of the base metal is accurate It is possible to detect well, and it is possible to trace a welding line with a small groove or a butt welding line with almost no groove. Further, since no disturbance such as welding light is received, it is possible to accurately follow the welding line even if it is installed near the welding torch.

According to a second aspect of the present invention, in the welding line automatic copying method according to the first aspect, the working gas required to generate the plasma arc used for detecting the welding line information is the same type or the same as the gas used for the welding electrode. Since the method uses active gas or CO2 gas, the plasma torch can be installed closer to the welding torch.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example when a conventional welding line copying method is performed,

FIG. 2 is a diagram showing the relationship between the position of the welding torch 1 and the change in welding current when performing the welding line copying method of FIG.

FIG. 3 is a diagram for explaining an example when another method of conventional welding line copying is performed,

4 is a diagram for explaining the operation of the conventional method of FIG.

FIG. 5 is a diagram for explaining an example when another conventional welding line copying method is performed;

6 is a diagram showing a cross section of a weld obtained by the method of FIG.

FIG. 7 is a diagram for explaining the relationship between the movement trajectory of the electrode of the welding torch and the welding line when the method of FIG. 5 is carried out;

FIG. 8 is a diagram for explaining a situation when performing welding line copying by the method of FIG. 5;

FIG. 9 is a diagram showing how the arc voltage changes at positions (a) to (c) in FIG. 8 together with the relationship with the rotation angle of the electrode;

10 is a diagram showing a state where a large two-layer bead is obtained by increasing the radius of gyration of the trailing electrode in the method of FIG. 5,

FIG. 11 is a state when the positional relationship between the oscillating center of the welding electrode and the welding line changes when welding is performed by advancing the trailing electrode while rotating it with a larger radius of gyration than the leading electrode after welding the lower layer. Figure to explain,

FIG. 12 is a diagram showing how the arc voltage changes when it changes as shown in FIG. 11, together with the relationship with the rotation angle of the electrode,

FIG. 13 is a view for explaining a state when the conventional method shown in FIG. 3 is applied to lap welding of thin plates;

FIG. 14 is a diagram showing an example of a plasma arc generator used for welding line detection of the present invention;

FIG. 15 is a diagram showing another example of the plasma arc generator used for welding line detection of the present invention,

FIG. 16 is a diagram showing still another example of the plasma arc generator used for the welding line detection of the present invention,

FIG. 17 is a diagram showing the relationship between the arc voltage and the distance between the plasma arc electrode and the base material.

FIG. 18 is a diagram showing a relationship between a groove position and an arc voltage when a plasma torch is oscillated in a direction crossing a welding line of a base metal having a groove;

FIG. 19 is a diagram showing a relationship between a butt position and an arc voltage when a plasma torch is oscillated in a direction crossing a welding line of a base metal in a butt state having almost no groove;

FIG. 20 is a diagram showing the relationship between the groove position and the arc voltage when the oscillating center of the plasma torch is variously changed with respect to the welding line;

FIG. 21 is a diagram showing a relationship between a difference between left and right integrated values and a distance between an electrode and a welding line when integrating an arc voltage between left and right with a predetermined width centering on an oscillating center of a plasma torch;

FIG. 22 is a diagram showing an example of an apparatus for carrying out the welding line copying method of the present invention.

[Explanation of symbols]

1 Welding torch 2 Welding electrodes 3,4 Base materials 5a, 5b Auxiliary electrodes 6a, 6b Welding power source 8 Target position of welding torch 9,10 Arcing position of auxiliary electrode 1a Leading torch 1b Leading electrode 2a Trailing torch 2b Trailing electrode 7a Lower layer bead 7b Upper layer bead 11 Electrode 12 Nozzle 13 Plasma working gas 14 Liner 15 Plasma arc 16, 17 Base material 18 Plasma arc power supply device 19 Pilot arc power supply device 20 High frequency generator 21 Pilot arc starting switch 22 Arc voltage detection Unit 23 Plasma torch 24 Welding torch 25 Plasma torch drive device 26 Plasma torch sylate position detector 27 Plasma control device 28 Welding power supply device 29 Welding torch drive device 30 Welding control device 31 Memory 32 Arithmetic circuit 33 Memory 34 Welding torch position detector 35 Plasma arc power supply device E Detection output at the center of oscillation S1 A value obtained by integrating the detection output of a predetermined width to the left of the center of oscillation S2 A value obtained by integrating the detection output of a predetermined width to the right of the center of oscillation Cf, Cf 'electrode trajectory is the most forward point in the welding advancing direction Cr, Cr' Electrode trajectory is the rearmost point in the welding advancing direction R, R'electrode trajectory is the position L where the electrode is closest to the vertical plate 3 , L'position of the electrode closest to the horizontal plate 4 in the electrode trajectory

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigenori Matsuura 2-1-11, Tagawa, Yodogawa-ku, Osaka-shi, Osaka Daihen Co., Ltd. (72) Hidetaka Nohara 2-1-11, Tagawa, Yodogawa-ku, Osaka, Osaka No. Daihen Co., Ltd. (72) Inventor Koji Kurahashi 2-1-1 Tagawa, Yodogawa-ku, Osaka City, Osaka Prefecture Daihen Co., Ltd.

Claims (2)

[Claims] 1. A welding line automatic copying method for arranging a welding line detecting sensor in front of a welding electrode for welding a base material in a welding advancing direction and causing the welding electrode to follow the welding line detected by the sensor, A plasma arc torch is provided in front of the welding electrode, and a plasma arc of a minute current that does not melt the base metal is generated from the plasma arc torch toward the base metal, and the plasma arc is welded to the base metal. Leading in the welding line direction while oscillating with a predetermined amplitude in the direction crossing the line, position information of the welding line is detected from the arc voltage change of the plasma arc, and the welding electrode is welded based on the detected welding line information. A welding line automatic copying method that corrects the line to a predetermined position. 2. The working gas used for the plasma arc torch is the same gas as that used for welding the welding electrode, an inert gas or CO2 gas.
The automatic welding line copying method described in.