JPS58176076A - Arc welding method - Google Patents

Abstract

PURPOSE:To stably form a bead having a good shape by following a variation of width of a groove, by controlling the rocking width of an electrode so that a difference of welding currents in case when a welding electrode is positioned in the center part of the groove and both the end parts becomes equal to a reference value. CONSTITUTION:In a method for arc-welding materials to be welded 3, 4 by rocking an electrode 1 installed to a welding torch 6, in the width direction of groove 2, moving it in the weld line direction and making a welding current flow from a welding power source 7, a Y axis motor 17 and an X axis motor 19 are controlled in accordance with a welding current detecting signal by a welding current detector 22, a distance between the electrode 1 and the materials to be welded 3, 4 is held in a set reference value, and the center of rocking of a torch shaft 10 is held in the center in the groove width direction. Also, the rocking width is controlled through a motor 13 of a rocking block 12 so that a difference of detecting signals of welding currents in the rocking center part and the end part becomes equal to a set reference value. Said method can be executed by detecting the welding voltage, as well.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arc welding method in which welding is performed while an electrode is oscillated 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.

The applicant has developed 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 weld metal according to the groove cross-sectional area. It has been developed 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. Gaps may occur.

When there is a gap in the groove like this,
If welding is performed while swinging the electrode at a constant width, the weld bead produced will not have a desirable shape, and the height of the bead will also vary. This makes it difficult to weld the next layer,
Eventually, welding defects such as insufficient penetration and undercuts occur.

FIG. 1(a) is a diagram showing 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, and 5 is a backing metal. , when the electrode 1 swings the groove 2 in the width direction with a constant width W, the welding current when the electrode 1 is located at the right end R1 center C1 left end of the groove 2 is the first
The waveform will be as shown in Figure (b).

In Fig. 1 (b), the vertical axis is the welding current value, and the horizontal axis is the electrode position.As shown in the drawing, the welding current has a waveform that is lowest at the center C of the groove 2 and higher at the right end R and left end. show. When the difference Δ■ between the highest current value 2 and the lowest current value at this time shows a predetermined value, the shape of the welded bead a is in the desired state shown in Figure 1 (c). It has become.

However, as shown in FIG.
When the electrode 1 swings the groove 2 in the width direction with the same constant width W as shown in Fig. 1 with a gap G existing between the grooves 2 and 4, the welding current at the right end R1 of the groove 2 and the right end of the center CI is , second
As shown in Figure (B), the difference Δ■' between the highest current value and the lowest current value I becomes a small value, which not only makes it difficult to detect as a control signal for groove tracing, etc., but also makes it difficult to detect the welded bead a'. If the shape is not convex as shown in Fig. 2(e), it will adversely affect 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 has occurred 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
The electrode is moved in the direction of the welding line while being oscillated in the width direction of the groove, the welding current flowing through the electrode or the welding voltage of the electrode is detected, and the detection signal causes the electrode to follow the groove surface. In an arc welding method in which welding is performed simultaneously, the difference between the detection signal when the electrode is located at the center of the groove and the detection signal when the electrode is located at the edge of the groove is the reference value. The present invention is characterized in that the swing width of the electrodes is controlled so as to match each other.

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

FIG. 3 is a schematic diagram showing an example of the torch 1 driving machine Sakaki used in the method of this invention. In the drawings, 1 is an electrode, 3,
4 is the material to be welded, 2 is the groove, 5 is the backing metal, 6 is the welding torch, 7 is the welding power source, 8j9 is the cable, 10 is the torch shaft,
11 is a torch shaft support block, 12 is a rocking block for the torch shaft 1o, 14 is a horizontal screw rod provided on the rocking block 12, and 13 is a portion of the support block 11 that holds the torch shaft 10 at a constant level by the horizontal screw rod 14. A motor 15 is a Y-axis block for swinging from side to side with a width W.

The Y-axis blocks 1 and 5 have vertical threaded rods 16 to which one end 12' of the swing block 12 is screwed to support the swing block 12.
A motor 17 for rotating a vertical threaded rod 16 is provided on the top of the torch, and the torch shaft 10 is moved up and down by the rotation of the vertical threaded rod 16 driven by the motor 17.

18 has a Y-axis block 15 fixed to one end thereof and 19, and the horizontal threaded rod 2o is screwed into a support block 21 provided on a welding cart (not shown). Therefore, when the horizontal screw rod 2o is rotated by the drive of the motor 9, 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 swing block 12 and the torch shaft 10 screwed into the horizontal threaded rod 14 of the swing block 12 move horizontally. As a result, the electrode 1 protruding from the welding torch 6 attached to the tip of the torch shaft 10 moves in the width direction of the groove 2, and thus the center of swing of the electrode 1 is set at the center of the groove 2. In addition, 22 is a welding current detector, 23 is a welding voltage detector, and the detection signal in this invention may be a welding current or a welding voltage inclination.

FIG. 4 shows an embodiment of the method of the present invention, which is based on the arc welding method using a method of detecting welding current or welding voltage (Japanese Patent Laid-Open No. 54-26261), which the present applicant previously applied for a patent.
It is a control block diagram when this invention is combined.

In the drawing, 22 is a current detector that detects the welding current of the electrode 1 (a voltage detector 23 that detects welding voltage may be used instead of the current detector 22), and 24 is a current detector 22.
Noise removal circuit for removing high frequency noise from the output of 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 a reference signal from a reference signal source 26 by a differential amplifier 27, and the integrator output ↓fTIat
The driving of the Y-axis motor 17 is controlled via the Y-axis motor driver 28 so that the period of one-cycle oscillation of (T: )-CH (OI: welding current) becomes a reference value. Reference numeral 29 denotes a trigger circuit that provides a periodic signal of the oscillation to the integrator 25 and a switching signal to the switch 30 every half period of the oscillation. The welding current detection output from the noise removal circuit 24 is
It is alternately distributed and fed to two integrators 31 and 32.

One integrator 31 integrates and bolds the detection output for the 0-T/20 half period of the oscillation, and the other integrator 32 integrates and bolds the detection output for the remaining half period of the oscillation from T/2 to T. , integrate the above detection output. Both types of differential amplifiers 33 compare the two types, and thereby, the drive of the X-axis motor 19 is controlled via the X-axis motor drive circuit 34 so that the output of the differential amplifier 33 becomes zero.

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 workpiece 3.4 is also set to the reference signal source 26. is held at the specified value.

In this 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'. Welding current I of the swinging end inputted to the swinging end switch circuit 35
R is temporarily stored in the memory 37. Similarly, the welding current IC 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 Δ■' of the differential amplifier 38 is input to the next differential amplifier 3.
9 is compared with the value Δ■ of the reference signal source 40, and the swing width controller 41 controls the swing motor 1 so that the deviation becomes zero.
3, and thus the torch shaft swings within the groove with an appropriate swing width depending on the width of the gap created between the materials to be welded.

42 is a potentiometer for detecting the swing width, and its signal is sent to the swing width controller 41 as the current swing width value, and is also sent to the pulse generator 43.

/F pulse generator 43 generates a swing end pulse signal 44 and a swing center pulse signal 45, and sends these signals to swing end switch circuit 35 and swing center switch circuit 35.
', and both circuits 35 and 35' are brought into conduction. The signal of the trench generator 43 is stored in the memories 37 and 3.
7' reset) It also acts as the ie pulse signal 46.47.

As another example of the method of the present invention, FIG. It is a control block diagram when combining.

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

The welding current detected by the current detector 22 and from which noise has been removed by the noise removal circuit is compared with the reference value of the reference signal source 49 by the differential amplifier 48, and the deviation is made zero by the Y-axis motor controller 50. The drive of the Y-axis motor 17 is controlled as follows. 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 welded materials 3, 4 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, and the voltage signal e is detected by the amplifier 52.
After being amplified by the trigger circuit 53, the half-cycle switching signal is applied to the integrators 55 and 56 by the switch 54 as a torch height signal every half-cycle.

One integrator 55 integrates and holds the voltage signal e for a half period of oscillation OT/2, and the other integrator 56 integrates and holds the voltage signal e for a half period of oscillation from T/2 to T. The above voltage signal e is integrated with respect to . Both types 2 T/2
2 T Outputs of dividers 55 and 56 T 10e d t and T f
T//2 edt is compared by the differential amplifier 57, and thereby the differential amplifier 5
The drive of the X-axis motor 19 is controlled so that the output of the X-axis motor 7 is always zero.

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

In this invention, the support block 12', that is, the torch shaft 10, which is detected as a stain pressure signal e by the potentiometer 51 in the control circuit described above and amplified by the amplifier 52,
is input into the swing end switch circuit 35 and the swing center switch circuit 35', and the swing width controller 41 controls the swing motor by the same operation as in the embodiment described with reference to FIG. 13 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.

Figures 6 to 8 are diagrams showing the oscillation state of the electrode and its displacement voltage waveform. Figure 6 (a) shows the oscillation of the electrode in the standard state with no gap between the welded materials 3 and 4. The figure (b) shows the moving state (Wo indicates the oscillation width) and the displacement waveform. ec is the voltage when the electrode is located at the center of the groove, and e8 is the voltage when the electrode is located at both ends of the groove. voltage when located at
Δe□ is the voltage difference between the two.

FIG. 7(a) shows the same state of oscillation of the electrode, which is the same as the standard state of FIG. Figure (b) shows the displacement waveforms, the voltage e when the electrode is located at the center of the groove, and the voltage e when the electrode is located at both ends of the groove.
'8 is smaller than the difference voltage Δeo in the reference state shown in FIG.

FIG. 8(A) shows a state in which the swing width of the electrode is expanded from Wo to W using the method of the present invention in the state shown in FIG. 7, and FIG. 8(B) shows the displacement waveform. Voltage e when the electrode is located at the center of the groove. The difference Δe between the voltage es and the voltage es at both ends of the groove is equal to the difference voltage Δe□ 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 equal to the voltage signal when the electrode is located at both ends of the groove,
The difference between the voltage signal and the voltage signal at the center of the groove is controlled to match the reference value, so even if a gap occurs between the welded materials and the groove width fluctuates, it will follow this. The swing width of the electrode is controlled, so the torch can be accurately traced in the width and height directions of the groove, making it possible to stably obtain a well-shaped bead, which is an industrial advantage. Excellent effects are brought about.

[Brief explanation of the drawing]

Figure 1 shows the swinging state of the electrode, the waveform of the welding current, and the bead shape when the groove is in a normal state, and Figure 2 shows the swing state of the electrode when the groove is in a normal state. FIG. 3 is a schematic diagram showing an example of a torch drive mechanism used in the method of the present invention; FIG. 4 is a diagram showing an embodiment of the method of the present invention. FIG. 5 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 drawing, ■...electrode, 2
... Bevel, 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 River swing block, 13... Motor 1' ,
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 threaded rod, 21... Support block, 22... Welding current detector, 23... Welding voltage detector, 24... Noise Elimination circuit, 25.31, 32, 55.56... Integrator, 26°40.49... Reference signal source, 28.50...
・Y-axis motor driver, 29.53...Trigger circuit, 3
0.54...Switcher, 27, 33, 38.39.48
．． 57... Differential amplifier, 34, 58... X-axis motor drive circuit, 35... Swinging end switch circuit, 35'.
... Swing center switch circuit, 37, 37'... Memory, 41... Swing width controller, 42... Potentiometer, 43.../9 Lux generator. Applicant: Japan Steel Tube Co., Ltd. r1 Agent: Keitabe Tsutsumi Ri11?1 Atsushi 1 (A) -W-1 (C) α Uma 2 (A) 2w-1 (C) 4'

Claims (1)

[Claims] An electrode is moved in the direction of the welding line while swinging in the width direction of the groove, a welding current flowing through the electrode or a welding voltage of the electrode is detected, and the detection signal is used to move the electrode. In an arc welding method in which welding is performed along the groove surface, a detection signal when the electrode is positioned at the center of the groove and a detection signal when the electrode is positioned at the edge of the groove are detected. An arc welding method characterized in that the swing width of the electrode is controlled so that the difference matches a reference value.