JPH0249831B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arc welding method in which welding is performed while swinging an electrode in the width direction of a groove formed in a material to be welded.

When performing arc welding while swinging the electrode in the width direction of a groove formed in a welded material, the welding current or welding voltage varies depending on the shape of the groove. This application describes a method of detecting this fluctuating welding current or welding voltage, and using the detection signal to control the electrode to follow the groove surface, control the electrode height, and control the deposited metal according to the groove cross-sectional area. It was developed by humans and numerous patent applications have been filed.

However, when performing actual welding work using the above method, the groove shape of the welded materials is not necessarily constant in the welding line direction, and the welded materials that are butted are separated from each other and become grooves. A gap may occur.

If welding is performed while the electrode is oscillated within a certain width when there is a gap in the groove, the weld bead that is formed will not have the desired shape and the height of the bead will also fluctuate. . As a result, it becomes difficult to weld the next layer, resulting in insufficient penetration and
Welding defects such as undercuts occur.

Figure 1A shows the swinging state of the electrode 1 when there is no gap between the welded materials 3 and 4 that are butted together and the groove 2 is in a normal state. When electrode 1 swings the groove 2 in its width direction by a constant width W, the welding current when the electrode 1 is located at the right end R, the center C, and the left end L of the groove 2 has the waveform shown in Fig. 1B. .

In Figure 1B, the vertical axis is the welding current value, and the horizontal axis is the electrode position.As shown in the drawing, the welding current is
The waveform is the lowest at the center C, and the highest at the right end R and left end L. Maximum current value at this time
When the difference ΔI between I ₂ and the lowest current value I ₁ shows a predetermined value, the shape of the electrodeposited bead a is in the desired state shown in FIG. 1C.

However, as shown in Fig. 2A, when a gap G exists between the welded materials 3 and 4, and the electrode 1 swings in the width direction of the groove 2 with the same constant width W as in Fig. 1, , the welding current at the right end R ₁ center C ₁ right end L of the groove 2 is such that the difference ΔI' between the highest current value I ₃ and the lowest current value I ₁ is a small value, as shown in FIG.
Not only is it difficult to detect as a control signal for groove tracing, etc., but the shape of the welded bead a' becomes the convex shape shown in FIG. 2C, which adversely affects the welding of the next layer.

As a result of repeated research to solve the above-mentioned problems, the present inventors have determined that the width of the electrode that swings in the width direction within the groove can be changed according to the width of the gap that occurs between the materials to be welded. It has been found that the above-mentioned problem can be solved by controlling the difference between the highest and lowest values of welding current so that it always remains at a predetermined reference value.

This invention was made based on the above findings, and includes moving an electrode in the direction of the welding line while swinging it in the width direction of the groove, detecting the welding current flowing through the electrode or the welding voltage of the electrode, Based on the detection signal, in the arc welding method in which the electrode is welded by following the groove surface, a swinging block having a horizontal threaded rod for supporting and swinging the torch, and a swinging block that supports the swinging block are used. , a Y-axis block having a vertical threaded rod for vertically moving the swinging block; and a horizontal threaded rod for horizontally moving the Y-axis block and the swinging block, to which the Y-axis block is fixed at one end. A torch drive mechanism consisting of an X-axis block having an a swinging block having a horizontal threaded rod for supporting the swinging block, a Y-axis block having a vertical threaded rod for supporting the swinging block and moving the swinging block up and down, and the Y-axis block being fixed to one end. , using a torch drive mechanism consisting of the Y-axis block and an X-axis block having a horizontal threaded rod for horizontally moving the swinging block, and the detected welding current or welding voltage of the electrode is set in advance. to match the reference value set.
Controlling the Y-axis block to position the electrode at a predetermined height from the groove surface, detecting the detected welding current or welding voltage of one half cycle of the electrode based on the center of oscillation; The X-axis block is controlled such that the difference between the welding current or welding voltage detected in the other half cycle based on the center of swing is zero, and the center of swing of the electrode is moved to the center of the groove. a detection signal that is any one of welding current, welding voltage, and vertical displacement of the torch axis when the electrode is located at the center of the groove; so that the difference between the detection signal due to any one of the welding current, welding voltage, and vertical displacement of the torch axis when located at the end of the torch coincides with the reference value.
The present invention is characterized in that the swing width of the electrode is controlled by controlling the swing block.

Next, the present invention will be explained with reference to examples and drawings.

FIG. 3 is a schematic diagram showing an example of a torch drive mechanism used in the method of this invention. In the drawing, 1
are electrodes, 3 and 4 are materials to be welded, 2 is a groove, 5 is a backing metal, 6 is a welding torch, 7 is a welding power source, 8 and 9 are cables, 10 is a torch shaft, 11 is a torch shaft support block, 12 is a swinging block of the torch shaft 10, 1
4 is a horizontal threaded rod provided on the swing block 12;
Reference numeral 13 designates a motor for swinging the torch shaft 10 left and right at a constant width W by means of a horizontal threaded rod 14 in the support block 11, and reference numeral 15 designates a Y-axis block.

The Y-axis block 15 is located at one end 1 of the swing block 12.
2' has a vertical threaded rod 16 which is screwed to support the rocking block 12, and the vertical threaded rod 16 is attached to the upper part of the vertical threaded rod 16.
The torch shaft 10 is moved up and down by the rotation of the vertical threaded rod 16 driven by the motor 17.

Reference numeral 18 denotes an X-axis block to which a Y-axis block 15 is fixed to one end, and the X-axis block 18 has a horizontal screw rod 20 and a motor 19 for rotating the horizontal screw rod 20. is a support block 2 provided on a welding cart (not shown).
1 is screwed together. Therefore, when the horizontal screw rod 20 is rotated by the drive of the motor 19, the X-axis block 18 moves in the X direction, and is accordingly screwed into the Y-axis block 15 and the vertical screw rod 16 of the Y-axis block 15. The pivoting block 12 and the torch shaft 10 screwed into the horizontal threaded rod 14 of the pivoting block 12 move horizontally together. As a result, the welding torch 6 attached to the tip of the torch shaft 10
The electrode 1 protruding from the groove 2 moves in the width direction of the groove 2, and the swing center of the electrode 1 is thus set at the center of the groove 2. In addition, 22 is a welding current detector, 2
3 is a welding voltage detector, and the detection signal in this invention may be either welding current or welding voltage.

FIG. 4 shows an embodiment of the method of the present invention, which is an arc welding method using a method of detecting welding current or welding voltage, which the applicant previously applied for a patent (Japanese Unexamined Patent Publication No. 54
26261) is combined with the present invention.

In the drawing, 22 is a current detector that detects the welding current of the electrode 1 (a voltage detector 23 that detects the welding voltage may be used instead of the current detector 22);
24 is a noise removal circuit that removes high frequency noise from the output of the current detector 22, and 25 is an integrator that time-integrates the detected welding current in synchronization with the period of oscillation.

The output of the integrator 25 is compared with the reference signal from the reference signal source 26 by the differential amplifier 27, and the integrator output 1/T∫ ^T ₀ Idt (T: period of one cycle of torch oscillation, I: welding current ) is the reference value, the driving of the Y-axis motor 17 is controlled via the Y-axis motor driver 28. Reference numeral 29 denotes a trigger circuit that provides a periodic signal of oscillation to the integrator 25 and a switching signal for each half period of oscillation to the switch 30;
The welding current detection output from the noise removal circuit 24 is alternately distributed and given to the two integrators 31 and 32 every half cycle with the center of oscillation as the base point.

One integrator 31 integrates and holds the detection output for the half period from 0 to T/2 of the oscillation, and the other integrator 32 integrates and holds the detection output for the remaining half period of the oscillation T/2.
The above detection output is integrated for a half cycle of ~T. The outputs 2/T∫ ^T/2 ₀ Idt and 2/T∫ ^T _T/2 Idt of both integrators 31 and 32 are compared by the differential amplifier 33, so that The X-axis motor 1 is adjusted such that the output of the differential amplifier 33 is zero.
Controls the drive of 9.

In this way, by controlling the motors 17 and 19, the swing center of the torch shaft 10 is held at the center in the groove width direction, and the distance from the welded materials 3 and 4 is also adjusted to the reference signal source 26. Retains the set value.

In the present invention, the welding current detected by the welding current detector 22 and noise removed by the noise removal circuit 24 in the above-mentioned control circuit is transmitted to the swing end switch circuit 35 and the swing center switch circuit 35'. and enter it. Swing end switch circuit 35
The welding current I _R of the swinging end inputted to the memory 3
7 will be stored once. Similarly, the welding current I _C at the center of oscillation inputted to the center of oscillation switch circuit 35' is temporarily stored in the memory 37'.

38 is a differential amplifier for the output values of the memories 37 and 37', and the output value ΔI' of the differential amplifier 38 is compared with the value ΔI of the reference signal source 40 by the next differential amplifier 39, and the deviation is zero. The swing motor 13 is controlled by the swing width controller 41 so that the torch shaft swings within the groove at an appropriate swing width depending on the width of the gap created between the materials to be welded.

42 is a potentiometer that detects the swing width;
The signal is sent to the swing width controller 41 as the value of the current swing width.
and is also sent to the pulse generator 43. The pulse generator 43 generates a swing end pulse signal 4
4 and a swing center pulse signal 45, and sends these signals to the swing end switch circuit 35 and the swing center switch circuit 35'.
35' becomes conductive. Also, the pulse generator 43
The signals also act as reset pulse signals 46, 47 for the memories 37, 37'.

FIG. 5 shows another example of the method of the present invention, an arc welding method (Japanese Patent Application Laid-Open No. 18447-1883), which is a method with a long groove and constant arc length control, for which the present applicant previously applied for a patent.
FIG. 3 is a control block diagram when the present invention is combined with the above.

In the drawing, 22 is a current detector that detects the welding current of the electrode 1, 24 is a noise removal circuit, and the fact that a voltage detector 23 may be used instead of the current detector 22 is similar to the above embodiment. It is.

The welding current detected by the current detector 22 and having its noise removed by the noise removal circuit is transmitted to the differential amplifier 48.
is compared with the reference value of the reference signal source 49, and the Y-axis motor controller 50 controls the drive of the Y-axis motor 17 so that the deviation becomes zero. As a result, the support block 12' shown in FIG. 3 moves up and down, and the distance between the welding torch 6 and the workpieces 3, 4 to be welded is controlled to be constant.

The amount of movement of the support block 12' described above is detected as a voltage signal e by the potentiometer 51, amplified by the amplifier 52, and then sent to the trigger circuit 53.
A switch 54 outputs a half-cycle switching signal to integrators 55 and 56 as a torch height signal every half-cycle.

One integrator 55 integrates and holds the voltage signal e for a half period from 0 to T/2 of the oscillation, and the other integrator 56 integrates and holds the voltage signal e for the remaining half period of oscillation T/2.
The voltage signal e is integrated over a half cycle of ~T. The outputs 2/T∫ ^T/2 ₀ edt and 2/T∫ ^T _T/2 edt of both integrators 55 and 56 are compared in a differential amplifier 57, and thereby a differential signal is generated via an X-axis motor drive control circuit 58. The drive of the X-axis motor 19 is controlled so that the output of the amplifier 57 is always zero.

By controlling the motors 17 and 19 in this manner,
The center of swing of the torch shaft 10 is held at the center in the groove width direction.

In this invention, the support block 1 is detected as a voltage signal e by the potentiometer 51 in the control circuit described above and amplified by the amplifier 52.
2', that is, the amount of displacement of the torch shaft 10, is input to the swing end switch circuit 35 and the swing center switch circuit 35', and the swing width is controlled by the same operation as in the embodiment described with reference to FIG. The swing motor 13 is controlled by the device 41 to swing the torch shaft within the groove at an appropriate swing width depending on the width of the gap created between the materials to be welded.

6 to 8 are diagrams showing the oscillation state of the electrode and its displacement voltage waveform.
Figure 4 shows the oscillation state of the electrode in the reference state with no gap (W ₀ indicates the oscillation width), and Figure ₄ shows the displacement waveform. , e _s is the voltage when the electrode is located at both ends of the groove, and Δe _p is the voltage difference between the two.

Figure 7A shows the oscillation state of the electrode in which the electrode oscillates with a oscillation width of W ₀ , which is the same as the reference state in Fig. 6, when a gap G occurs between the materials to be welded 3 and 4. indicates the displacement waveform, and the difference Δe between the voltage e _c when the electrode is located at the center of the groove and the voltage e′ _s when the electrode is located at both ends of the groove is given by
This is smaller than the differential voltage Δe ₀ in the reference state shown in the figure.

Figure 8A shows a state in which the swing width of the electrode is expanded from W ₀ to W using the method of the present invention in the state shown in Figure 7, and Figure 8B shows the displacement waveform, with the electrode open. The difference Δe between the voltage e _c when located at the center of the tip and the voltage e _s when located at both ends of the groove is equal to the difference voltage Δe ₀ in the reference state shown in FIG.

As described above, according to the method of the present invention, the swing width of the electrode is such that the difference between the voltage signal when the electrode is positioned at both ends of the groove and the voltage signal when the electrode is positioned at the center of the groove is Since it is controlled to match the reference value, even if a gap occurs between the materials to be welded and the groove width fluctuates, the swing width of the electrode is controlled to follow this, and the torch can therefore be adjusted appropriately. Industrially excellent effects such as being able to reliably follow the groove in the width and height directions and stably obtaining beads of good shape are brought about.

[Brief explanation of drawings]

Figure 1 is a diagram showing the swinging state of the electrode, the waveform of the welding current, and the bead shape when the groove is in a normal state.
The figure shows the oscillation state of the electrode, the waveform of the welding current, and the bead shape when a gap exists between the materials to be welded. Figure 3 shows an example of the torch drive mechanism used in the method of this invention. FIG. 4 is a control block diagram showing an embodiment of the method of the present invention, and FIG.
The figure is a control block diagram showing another embodiment of the method of the present invention, and FIGS. 6 to 8 are diagrams showing the oscillation state of the electrode and its displacement voltage waveform. In the drawings, 1... electrode, 2... groove, 3, 4... material to be welded, 5... backing metal, 6... welding torch, 7... welding power source, 8, 9... cable, 10 ... Torch shaft, 11 ... Torch shaft support block, 12 ... Swing block, 13 ... Motor, 14 ... Horizontal threaded rod, 15 ... Y-axis block, 16 ... Vertical threaded rod, 17 ... Y Axis motor, 18...X-axis block, 19...X-axis motor, 20...Horizontal screw rod,
21... Support block, 22... Welding current detector, 23... Welding voltage detector, 24... Noise removal circuit, 25, 31, 32, 55, 56... Integrator, 26, 40, 49... Reference signal source, 28,5
0...Y-axis motor driver, 29,53...Trigger circuit, 30,54...Switcher, 27,33,3
8, 39, 48, 57... Differential amplifier, 34, 5
8... X-axis motor drive circuit, 35... Swing end switch circuit, 35'... Swing center switch circuit,
37, 37'...memory, 41...oscillation width controller,
42... Potentiometer, 43... Pulse generator.

Claims (1)

[Claims] 1. An electrode supported by a torch is moved in the direction of the welding line while swinging in the width direction of the groove, detects the welding current flowing through the electrode or the welding voltage of the electrode, and generates a detection signal thereof. In an arc welding method in which welding is performed by making the electrode follow a groove surface, as a drive mechanism for swinging the electrode,
a swinging block having a horizontal threaded rod for supporting and swinging the torch; a Y-axis block supporting said swinging block and having a vertical threaded rod for moving said swinging block up and down; using a torch drive mechanism consisting of a fixed Y-axis block and an X-axis block having a horizontal threaded rod for horizontally moving the oscillating block; The Y-axis block is controlled so that the current or welding voltage matches a preset reference value at a predetermined height of the electrode from the groove surface. The detected welding current or welding voltage of the electrode in one half cycle based on the center of oscillation and the detected welding current or welding voltage in the other half cycle based on the center of oscillation of the electrode. Control the X-axis block so that the difference with the voltage is zero, and position the center of swing of the electrode at the center in the width direction of the groove, and when the electrode is located at the center of the groove. a detection signal based on any one of the welding current, welding voltage, and vertical displacement of the torch axis, and the welding current, welding voltage, and vertical direction of the torch axis when the electrode is located at the end of the groove. By controlling the swing block so that the difference between the detection signal and the detection signal due to any one of the displacements matches the reference value when there is no gap in the groove or when there is a gap of a predetermined width. . An arc welding method, characterized in that the swinging width of the electrode is controlled, and thus the electrode is caused to swing in the width direction within the groove, following fluctuations in the groove width.