JPH09253847A - Automatic welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute stabilized and efficient welding by setting the time, at which pulse welding voltage is turned to smaller than threshold level voltage, to arc short circuiting width and adjusting welding condition corresponding to a size of width and/or arc short circuiting generating frequency. SOLUTION: Welding state of a welding power source 9 to weld a base metal 1 is measured and controlled by a controller 10. When base voltage is lowered than a threshold level 30, a comparator 12 discriminates that arc short circuiting is happened so as to generate a comparator output 31. The output 31 is counted by a counter 15 through a gate circuit 14, an interruption signal generating circuit 16 generates an interruption signal 22 corresponding to generation of the output 31, so as to be made to arc short circuiting frequency, A computer 11, on receiving the interruption signal 32, detects generation position of arc short circuiting and changes a mode of range, center, height, etc., of weaving and arc voltage. As a result, happening of arc short circuiting is reduced, welding efficiency is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention controls pulse welding current / voltage, weaving, etc. for the purpose of realizing high-speed welding while stabilizing arc generation through proper control of arc shorts in automatic welding equipment. The present invention relates to an automatic welding device. Here, the arc short-circuit is a state in which the gap between the welding wire (electrode) and the base material or the molten metal becomes too short, and a short circuit occurs between the two.

[0002]

2. Description of the Related Art In conventional butt arc welding of pipes, driving of weaving or the like is generally performed by a pulse motor for relatively low speed and by a servo motor for high speed. Further, in order to keep the torch at an optimum position with respect to the work, current and voltage during welding are monitored and the position of the torch is feedback controlled so that the values are appropriate.

As a patent document for pipe circumference welding,
JP-A-63-183776 and JP-A-4-284.
There is a 973 publication. The technique described in Japanese Patent Laid-Open No. 63-183776 relates to an arc rotary all-position welding device. In this method, the groove shape is narrow and high precision machining is required, and it is difficult to apply the method to a work having a wide groove width. The technique described in Japanese Patent Laid-Open No. 4-284973 relates to an automatic arc welding method in which welding of a groove portion is controlled in real time, but the point of measuring a pulse welding current / voltage waveform has not been solved. The pulsed mag welding is described in "Welding Technology", February 1989, pages 67-76.

[0004]

In order to perform optimum welding in pipe circumference welding, high-speed weaving, etc., more precise measurement of pulse welding current / voltage waveform is possible, arc output voltage control, pulse accent ( It is necessary to contribute to prevention control of the pulse width and the waveform of the pulse current.

As described above, the welding current and the welding voltage are measured and the position of the torch is feedback-controlled, but the pulse welding current / voltage, which is obtained in real time by using the information of the arc short width, No control such as weaving was performed.

In the present invention, the arc short circuit is detected at the same time as the arc short circuit is generated, the duration is measured, and the pulse welding current / voltage, weaving, etc. are controlled by the frequency and duration, the interrupt signal, and the like. The purpose of the present invention is to provide a good quality weld by adding and pulling up and down in accordance with the groove surface to recover and optimize the arc short circuit.

[0007]

In order to solve the above problems, an automatic welding apparatus of the present invention is a welding power source apparatus capable of controlling a pulse welding current / voltage, a driving apparatus for driving a welding torch, and controlling them. An automatic arc welding device equipped with a control device; the time when the base voltage of the pulse welding voltage of the work piece and the welding wire is compared with the threshold level voltage regarded as an arc short, and the former is below the latter. Is defined as the arc short width, and the pulse welding current and / or voltage, weaving, or the like is controlled according to the length of the arc short width.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In pulse automatic welding, information on pulse welding current / voltage waveforms is an important factor, and it is important to correctly recognize this information and perform welding under optimum conditions. Especially when an arc short occurs,
It is important to detect and control this arc short. To detect an arc short, a threshold level is set, and a detection circuit (comparator) that detects an arc short when the voltage falls below that voltage and a circuit (counter) that measures the arc short width are used to detect the arc short. A device for recovery and optimization can be provided.

A comparator, a gate, a counter, an interrupt signal generation circuit, etc. are provided. When an arc short circuit occurs, the interrupt signal generation circuit interrupts, the arc short width is measured, and a control command is issued based on these signals. It is applied to the welding power source and controls the pulse welding current / voltage and weaving.

In addition to the normal weaving in the left-right direction, the torch can be pulled up and down along the groove face to weave two-dimensionally. It is also possible to control the weaving conditions by measuring the presence or absence of arc shorts, the frequency, and the arc short width at the central portion of the weaving, the vicinity of the left and right, the groove surface, and the like.

The operation of each configuration of the above-described embodiment of the invention is as follows. When an arc short occurs in automatic pulse welding, the arc short occurrence frequency (the ratio of the number of arc shorts to the number of welding pulses) is determined by detecting the arc short, and the arc short width is measured to determine the length of the arc short. Ask for. Based on the result, the pulse welding current / voltage, weaving, etc. are controlled so that the frequency is reduced and the arc short width is shortened.

When an arc short circuit occurs, the interrupt signal generating circuit can interrupt and measure the arc short width, so that a control command can be given to the welding power supply device at high speed, and the pulse welding current / voltage can be obtained. , Weaving, etc. can be quickly controlled. In addition to normal left and right weaving, the welding wire can be pulled up and down along the groove surface to perform two-dimensional weaving, so ideal recovery and optimization of arc shorts can be performed. . Weaving conditions can be controlled by measuring the presence or absence of arc shorts, frequency, and arc short width at the center of weaving, around the left and right, and on the groove surface.
Welding is possible according to the ambient conditions.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a control device for detecting an arc short circuit and performing pulse welding current / voltage control in automatic pipe welding according to an embodiment of the present invention. FIG. 2 is a timing chart of main signals in this embodiment. FIG.
It is a figure which shows the detail of the weaving in the groove. 4 is a weaving locus, FIG. 5 is an output voltage control, FIG. 6 is a torch up / down control, FIG. 7 is a torch left / right control, FIG. 8 is a torch opening surface control, FIG. 9 is a weaving speed control according to a weaving width change, and FIG. The state of horizontal 3-division torch vertical control is shown.

In the drawings, reference numeral 1 is a body to be welded, 2 is a welding bead, 3 is a welding groove, 4 is a welding wire, and 5 is a torch for sending out the welding wire 4. Further, 6 is a locus of weaving, 7 is a welding advancing direction, 8 is a feed of the welding wire 4, and a pulling direction of the torch 5. Reference numeral 9 denotes a welding power supply device, which supplies a pulse welding current / voltage to the welding wire 4.

In FIG. 1 and the like, reference numeral 10 is a control device, 1
1 is a computer, 12 is a comparator, 13 is a clock signal, 14 is a gate, 15 is a counter, 16 is an interrupt signal generation circuit, 17, 18, 19 are D / A conversion circuits, 30
Is a threshold level, 31 is a comparator output, 3
2 and 33 are interrupt signals.

In FIG. 2 and the like, reference numeral 34 is an arc voltage for pulse welding, 35 is a base voltage, 36 is an arc short, and 37 is a pulse welding current. In FIG. 5 and the like, reference numeral 40 indicates the weave center. In FIGS. 7 and 8, reference numerals 41 and 42 are left end positions of weaving, 43 and 44 are right end positions of weaving, and 45 and 46 are weaving loci along the left and right groove faces.

First, the outline of welding in this embodiment will be described. As shown in FIG. 3, in the groove 3, the welding wire 4 is melted by the arc by the arc voltage of pulse welding to form the bead 2 and the body 1 to be welded is joined. FIG.
As shown in, the arc voltage 34 for pulse welding is supplied alternately with the base voltage 35 at a constant cycle. A pulse welding current 37 is also shown on the lower side of FIG. In pulse welding, the transfer of the deposited metal to the base material is so-called spray transfer, and droplet transfer such as 1 drop / 1 pulse is possible. Therefore, it becomes possible to easily control the deposited metal by controlling the pulse waveform.

Next, the arc short circuit will be described. In general, if the arc length is made long enough not to cause an arc short, the molten pool becomes large due to the expanded arc column, making it difficult to weld in all positions and at high speed. On the other hand, if the arc length is too short, the droplets at the tip of the wire come into contact with the surface of the molten pool, causing an arc short circuit and generating a large amount of spatter. Here is the need for proper control of arc shorts. When the base voltage 35 falls below the threshold level 30, the comparator 12 detects the occurrence of the arc short 36, and the arc short 36 is converted into the "0/1" signal of the comparator output 31. Therefore, the comparator 12 (FIG. 1) compares the base voltage 35 applied between the welding wire 4 and the body 1 to be welded with the threshold level 30, and when the voltage drops below the threshold level 30, the signal is regarded as an arc short. Generates comparator output 31. The threshold level 30 is set from the computer 11 via the D / A conversion circuit 17 to a voltage level lower than the base voltage 35 and regarded as an arc short circuit. The interrupt signal generation circuit 16 (FIG. 1) generates an interrupt signal 32 indicating the occurrence of an arc short and an interrupt signal 33 indicating recovery from the arc short, based on the rising and falling of the comparator output 31.

The output 31 of the comparator 12 is given to the gate circuit 14 together with the clock signal 13. The gate circuit 14 opens the gate and allows the clock signal 13 to pass while the output 31 of the comparator 12 is at a high level. The clock signal 13 is counted by the counter 15 and becomes a signal indicating the arc short width. Here, the clock signal 13 is supplied from the computer 11. From the operation of the counter 15, the arc short width (TAS) is obtained. Further, the frequency of arc short circuit is obtained from the interrupt signals 32 and 33. Basically, the pulse welding current / voltage and weaving are controlled so as to reduce the frequency and shorten the width according to these data. The details will be described later. The data such as the frequency of arc short circuit is stored in a memory (not shown) in the computer 11 and used for output and automatic control.

The interrupt signal generation circuit 16 is, as described above,
Interrupt signals 32 and 33 are generated from the rising and falling of the output 31 of the comparator 12 to inform the computer 11 that an arc short 36 has occurred and has recovered. Since the interrupt signal 32 can generate a signal at high speed,
The computer 11 receives the interrupt signal 32 for generating the arc short 36, accurately detects the position where the arc short occurs, and changes the mode such as the weaving range, center, and height from the position where the arc short occurs. The current position of the torch is determined by the current position of the torch. The current position of the torch is the output of the encoder (not shown) provided on each axis motor that controls the torch position (or the head position where the torch is attached). Obtained based on. By determining the current position at the timing of the interrupt signals 32 and 33 indicating the occurrence and recovery of the arc short, it is possible to recognize where the arc short occurred and where it was recovered. The details of the control based on the occurrence status of the arc short circuit will be described later.

Further, the computer 11 receives the interrupt signal 32 of the occurrence of the arc short 36, acts on the optimization of the arc voltage 34 in the cycle next to the cycle in which the arc short occurs, and optimizes the arc short. . In this way, the arc phenomenon is optimized at the same time as the occurrence of the arc short 36, or at least in the next cycle or the following cycle. Reference numerals 18 and 1 in FIG.
9 is a pulse welding current 37 / arc voltage 34 current command,
A D / A conversion circuit for setting a voltage command, which is set based on a command from the computer 11.

The weaving locus 6 in FIG. 3 shows one of the features of this embodiment. Conventional weaving was performed only in the left-right direction, but in the present embodiment, in left-right weaving, both ends are moved upward and downward by following the groove surface. Weaving is performed in the plane. Two-dimensional weaving is effective when an arc short circuit occurs due to contact with the groove surface. The pulling-up angle and pulling-up height are optimally set in advance. For details, refer to the application of the same applicant (filed on March 25, 1996, reference number KP46
See 0).

FIG. 4 shows a general weaving locus in this embodiment. W is the weaving width of the flat part,
Sl is the weaving width in the groove surface direction, θ is the slope angle, Zh is the weaving height, Fw is the weaving speed in the flat portion, Fs is the weaving speed in the groove surface direction,
F is the average speed. Weaving is done in two dimensions,
There are a flat part and a slope part. The weaving variables (W, Zh, θ, Fw, Fs) can be set arbitrarily.

FIG. 5 shows a weaving locus during output voltage control. The characteristics of the output voltage control of this embodiment are:
The voltage is controlled so that an appropriate arc short circuit (short circuit) occurs in the weaving central portion 40. Assuming that the arc short width is Tas, the reference time for determining a long short is Pl, and the voltage adjustment amount is ΔV, the arc short width T
The following relationship is established between as and the voltage adjustment amount ΔV. (A) Tas ≧ Pl → Increase voltage. (+ ΔV) (b) 0 <Tas <Pl → Hold as it is. (C) Tas = 0 → Reduce the voltage. (-△ V)

That is, in the case of (a), arc short circuit occurs too much, which is not preferable from the viewpoint of increase in spatter and deterioration of bead shape. Therefore, in order to avoid it, the voltage is raised. In the case of (c), it seems to be good at first glance, but if the arc short is 0, conversely, since the arc length is long, speeding up is hindered, and the bead shape in the standing upright posture deteriorates. Or undercut may occur. The voltage is raised to prevent this.

FIG. 6 shows a weaving locus in the torch vertical control. In the same figure, (a) shows the case where the center of the bead is high, and (b) shows the case where the center of the bead is low. At the weaving center 40,
Control the torch up and down so that a proper arc short (short circuit) occurs. When the torch vertical adjustment amount is ΔZ, the following relationship is established between the arc short width and the torch vertical adjustment amount. (A) Tas ≧ Pl → Raise the torch. (+ ΔZ) (b) 0 <Tas <Pl → Hold as it is. (C) Tas = 0 → Lower the torch. (-△ Z)

That is, in the case of (a), the arc short circuit occurs too much, and the torch is raised in order to shorten the arc short circuit time from the same viewpoint as described above. Also in the case of (c), the torch is lowered in order to flow the arc short time from the same viewpoint as described above.

FIG. 7 shows a weaving locus for torch control at both ends of the weaving. The left and right positions of the torch are controlled so that proper arc shorts (short shorts) occur at the left ends 41, 42 or the right ends 43, 44 of the weaving. Weaving adjustment range of the flat part △
When W is set, the following relationship is established between the arc short width at the left or right position and the lateral position adjustment amount of the torch. Taking the left side as an example, (a) The left side Tas ≧ Pl → the left position is narrowed inward. (-ΔW) (b) Left side 0 <Tas <Pl → Hold as it is. (C) Tas = 0 on the left side → Spread the left position outward. (+ ΔW) Do the same for the right side. The significance of doing this is the same as in the case of the torch up / down control described above. The Tas on the left side and the Tas on the right side are based on the values of the encoder added to the motor for controlling the position of the left-right axis, as described above.
The width of the arc short circuit generated in the predetermined left side position range and right side position range is detected.

FIG. 8 shows a weaving locus during control of the torch groove surface. The lateral position of the torch or the angle of the slope is controlled so that an appropriate arc short (short short circuit) occurs at the weaving loci 45 and 46 along the groove surface. Assuming that the weaving adjustment width of the flat part is ΔW and the slope adjustment angle is Δθ, the following relationships are established between the arc short width at the left or right position, the slope adjustment angle, and the torch horizontal position adjustment amount. To have. (A) Tas ≧ Pl on the left side → narrow the left position inward. (-ΔW) or increase the left angle. (+ Δθ) (b) Left side 0 <Tas <Pl → Hold as it is. (C) Tas = 0 on the left side → Spread the left position outward. (+ ΔW) Or decrease the left angle. (-△ θ) Do the same for the right side. The significance of doing this is the same as in the case of the torch up / down control described above.

FIG. 9 shows the situation of weaving speed control with changing the weaving width. Weaving width is W + △
When it becomes W, the weaving speed is corrected by obtaining the change coefficient KKf by the following equation (1). Change coefficient KKf = (W + ΔW + 2Sl) / (W + 2Sl) (1) The weaving speed after the change is represented by the following expressions (2) and (3). Weaving speed of flat part Fw ′ = KKf · Fw (2) Weaving speed of slope part Fs ′ = KKf · Fs (3) The significance of doing this is to improve the situation of arc short circuit as in the case described above. is there.

FIG. 10 shows the state of horizontal three-division torch vertical control. Horizontal part of weaving is left side A1, central part A
2, the right side A3 is divided into three, the arc short width of each is obtained, and the vertical position of the torch is controlled so that an appropriate arc short (short short) occurs. The significance of doing so is to improve the situation of arc short circuit, as in the case described above. The detection of Tas on the left side, Tas at the center, and Tas on the right side is the same as in the case of left and right division, except that the position range in the left and right direction is divided into three. In either case of two divisions or three divisions, a range in which an arc short is not detected or an arc short width is not calculated may be provided between the adjacent position ranges.

As described above, according to the present invention, the pulse welding current / voltage, weaving, etc. can be set to optimum values by measuring the arc short width, frequency, etc.
High quality welding is possible. Since a high-speed command signal can be issued at the position where the arc short circuit occurs or at the start of the arc short circuit, the weaving can be changed from that position and the pulse welding current / voltage can be increased or decreased from the next cycle. Also,
Two-dimensional weaving along the groove surface is possible, and arc short recovery and optimization can be achieved, which can make a large industrial contribution.

[0033]

As is apparent from the above description, the present invention exhibits the following effects. (1) By measuring the degree of arc short circuit in real time, it becomes possible to control the pulse welding current / voltage in real time with respect to changes in ambient conditions. As a result, it is possible to carry out welding which is stable and highly efficient with less occurrence of arc short circuit. (2) It can be applied to left and right copying of weaving. Therefore, proper weaving can be performed and welding performance can be improved. (3) The occurrence of a fine arc short can be detected according to the welding condition of the lower layer, and the optimum weaving locus can be generated based on this.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a control device for detecting an arc short circuit and performing pulse welding current / voltage control in automatic pipe welding according to an embodiment of the present invention.

FIG. 2 is a timing chart of main signals in this embodiment.

FIG. 3 is a diagram showing details of weaving in the groove.

FIG. 4 shows a general weaving locus in this embodiment.

FIG. 5 shows a weaving locus during output voltage control.

FIG. 6 shows a weaving locus in torch vertical control.

FIG. 7 shows a torch-controlled weaving locus at both ends of the weaving.

FIG. 8 shows a weaving locus during control of the torch groove surface.

FIG. 9 shows a situation of weaving speed control with changing weaving width.

FIG. 10 shows a state of horizontal three-division torch vertical control.

[Explanation of symbols]

1 ... Object to be welded, 2 ... Weld bead, 3 ... Weld groove, 4 ...
Welding wire, 5 ... torch, 6 ... weaving, 7 ... welding progress direction, 8 ... torch vertical direction, 9 ... welding power supply device,
10 ... Control device, 11 ... Computer, 12 ... Comparator, 13 ... Clock signal, 14 ... Gate, 15 ... Counter, 16 ... Interrupt signal generation circuit, 17, 18, 19 ... D
/ A conversion circuit, 30 ... Threshold level, 31 ... Comparator output, 32, 33 ... Interrupt signal, 34 ... Arc voltage for pulse welding, 35 ... Base voltage, 36 ... Arc short, 37 ... Pulse welding current, 40 ... Weave Center, 4
1, 42 ... Left end position, 43, 44 ... Right end position, 45, 4
6 ... Left and right groove surface positions

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Ikuo Mibu 2982-3 Sugaya, Naka-machi, Naka-gun, Ibaraki Prefecture (72) Kenichi Maeda 1225-47 Tenjinbayashi, Hitachiota-shi, Ibaraki Prefecture

Claims (9)

[Claims] 1. A welding power source device capable of controlling pulse welding current / voltage, a drive device for driving a welding torch, and an automatic arc welding device equipped with a control device for controlling these; an object to be welded and a welding wire. The base voltage of the pulse welding voltage between the two and the voltage of the threshold level which is regarded as an arc short are compared, the time when the former becomes the latter or less is defined as the arc short width, and the length of this arc short width and / or the occurrence of arc short occurs. An automatic welding device characterized in that it controls pulse welding current and / or voltage, weaving, or the like according to the frequency of. 2. A comparator for comparing a pulse welding voltage and a threshold voltage, a counter for measuring an arc short width, an interrupt signal generating circuit and the like are provided, and the comparator is used to prevent an arc short from occurring during an arc short period. Generating the output signal, and determining the arc short time by counting a predetermined clock signal by the counter during the output period of the output signal, and based on the output signal indicating the occurrence of the arc short, the control device. The automatic welding device according to claim 1, wherein the occurrence of an arc short circuit is notified to. 3. When an arc short occurs, the welding wire is two-dimensionally weaved by pulling up or down along the groove surfaces at the left and right ends to optimize the arc short. The automatic welding device described. 4. The automatic welding device according to claim 1, wherein the output voltage of the pulse welding power supply device is controlled so that a short arc short circuit occurs in the central portion of the horizontal portion of the weaving. 5. The automatic welding device according to claim 1, wherein the torch is moved up and down at the center of the weaving to control the drive device for the automatic welding device so that a short arc short circuit occurs. 6. The automatic welding device according to claim 1, wherein the drive device for the automatic welding device is controlled so that short arc shorts occur at the left and right ends of the weaving. 7. The automatic welding device according to claim 1, wherein the drive device for the automatic welding device is controlled so that a short arc short circuit occurs at the groove surface of the weaving. 8. The automatic welding device according to claim 1, wherein the speed is corrected in accordance with the change of the weaving width. 9. The horizontal part of the weaving is divided into left, center, and right parts into three parts, and the arc short width of each part is obtained.
9. The automatic welding device according to claim 1, wherein the vertical position of the torch is controlled so that a short arc short circuit occurs.