JPH11277234A - Short circuiting transfer type arc welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly restore the molten quantity of a consumable electrode up to a proper arc state by immediately varying the molten quantity of the consumable electrode even when a distance between the consumable electrode and an object to be welded is rapidly varied. SOLUTION: In a short circuiting transfer type arc welding method wherein a consumable electrode is used and welding is executed while repeating the generation of a short circuit and an arc, the length of an arc generating period at one time is detected, an output voltage of a welding power source in the next arc generating period is decreased in proportion to the detected length of the arc generating period, and a welding current in the next arc generating period is increased or decreased in inverse proportion to the length of the arc generating period at one time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a short-circuit transfer type arc welding method in which a consumable electrode is used and welding is performed while repeating a short circuit and an arc.

[0002]

2. Description of the Related Art In order to perform stable welding by consumable electrode type arc welding, a consumable electrode fed at a constant speed is controlled so as to be melted at a constant speed comparable to the feeding speed of the consumable electrode. There must be. In particular, in the short-circuit transfer type arc welding method, the phenomenon in which the consumable electrode and the workpiece are short-circuited or an arc is generated alternately is alternately repeated, so that it is difficult to control the amount of melting. Conventionally, the control of the melting amount of the consumable electrode in such welding is performed by keeping the average voltage during welding constant.

FIG. 6 shows an example of an apparatus for performing a conventional short-circuit transfer type arc welding method. In FIG. 1, reference numeral 1 denotes an AC power supply, and a commercial AC power supply is used. Reference numeral 2 denotes a power conversion circuit, which converts the power from the AC power supply 1 into a DC output having substantially constant voltage characteristics according to the output command signal Sw1. Reference numeral 3 denotes a DC reactor, which gives the output current of the power conversion circuit 2 a time constant of a current change suitable for short-circuit transfer type arc welding. Reference numeral 4 denotes a welding torch and a feed roll 6 driven by an electric motor 5.
Consumable electrode 8 fed toward workpiece 7 by
Is interpolated, and the power from the power conversion circuit 2 is supplied thereto. Reference numeral 9 denotes a motor control circuit for controlling the rotation speed of the motor 5 to be constant. Reference numeral 10 denotes a voltage detector for detecting an instantaneous value Vd of the welding voltage, 11 denotes a welding voltage smoothing circuit for smoothing the output of the voltage detector 10 to obtain an average value Vda of the welding voltage, and 12 denotes a welding voltage setting circuit. Set the voltage set value Vs. A comparator 13 compares a set value Vs of the welding voltage setting circuit 12 with an output signal Vda of the welding voltage smoothing circuit 11 and outputs a difference signal ΔV = Vs−Vda. An amplifier 14 amplifies the output signal ΔV of the comparator 13 as necessary. Reference numeral 15 denotes an arc period detector, which determines that an arc period has occurred when the output signal Vd of the voltage detector 10 is higher than a predetermined value, and outputs a high-level arc period signal Sad. Reference numeral 16 denotes an output voltage setting device for a short-circuit period, which outputs an output voltage setting signal Vss having a value lower than the output voltage during the arc period so that the output current of the power conversion circuit 2 during the short-circuit period does not become excessive. Reference numeral 17 denotes a signal switching circuit which switches the signal to the (a) side when the arc period signal Sad of the arc period detector 15 is at a high level, and switches to the (b) side when the arc period signal Sad is at a low level. An analog switch transmitting to the conversion circuit 2 is used.

In FIG. 6, a voltage during welding is detected by a voltage detector 10 and smoothed by a welding voltage smoothing circuit 11 to obtain a detected voltage smoothed signal Vda. The welding voltage setting signal Vs, which is an output from the welding voltage setting circuit 12, and the detection voltage smoothing signal V
da is compared by the comparator 13 and the difference signal ΔV = Vs−Vda
Is output. The output ΔV of the comparator 13 is then input to the amplifier 14 and amplified to a level corresponding to the output voltage of the output voltage setting device 16 for the short-circuit period to become the output voltage command signal Vud during the arc period. During welding, a short circuit and an arc occur alternately, so that the output of the voltage detector 10 is also supplied to the arc period detector 15 to output the arc period signal Sad when the instantaneous value Vd of the welding voltage is higher than a predetermined value. Output as a high level signal. While the arc period signal Sad is at the high level, that is, during the arc period, the signal switching circuit 17 sets the signal switching circuit 17 to the (a) side and selects the output signal Vud of the amplifier 14. During the period in which the arc period signal Sad is at the low level, that is, during the short circuit period, the signal switching circuit 17 is set to the (b) side to select the output signal Vss of the output voltage setting device 16 for the short circuit period. The output command signal Sw1 selected in this way is sent to the power conversion circuit 2.

FIG. 7 shows a timing chart of the operation of the apparatus shown in FIG. In FIG. 7, (a) is a detected voltage smoothing signal Vda obtained by smoothing the welding voltage instantaneous value Vd, which is an output signal of the voltage detector 10, and (b) is a welding voltage smoothing circuit 11 smoothing the welding voltage instantaneous value Vd. (C) is the output Δ of the comparator 13
V, (d) the output signal Vud of the amplifier 14, (e) the output signal Sad of the arc period detector 15, and (f) the output command signal Sw1 selected by the signal switching circuit 17, respectively. It is shown with the passage of time. 6 and 7, during welding, the consumable electrode 8 repeatedly generates an arc and short-circuits the workpiece 7 several tens of times per second. When a short-circuit occurs, the welding current rapidly increases, and the increased current flows to cut the short-circuit by the electromagnetic pinch force acting on the short-circuit, thereby promoting arc regeneration. At this time, if the current becomes excessively large, spatter will be generated during arc regeneration, so that the signal switching circuit 17 is switched to the side (b) during the short circuit period, and the output voltage of the power conversion circuit 2 is set to the output voltage for the short circuit period. Is reduced to a low value determined by the setting signal Vss of the detector 16. Usually, the lower limit and the upper limit of the welding current at the time of this short circuit are determined by the electromagnetic pinch force required to eliminate the short circuit and the allowable spatter amount at the time of arc regeneration.

[0006]

In the above-mentioned conventional method, since the average voltage is controlled to be constant, the welding voltage must be sufficiently smoothed and used as output control information of the welding power source. Because of this, the response speed of the control becomes slow,
Sufficient control could not be performed.

This point will be described in detail with reference to FIG. FIG. 8 shows a state in which the protruding length of the consumable electrode 8 from the welding torch 4 is suddenly shortened by climbing over a step during welding. FIG. 7A shows an instantaneous welding voltage Vd and a detected voltage smoothed signal Vda obtained by smoothing the instantaneous welding voltage Vd, and FIG.
a and the average arc current Ida, and (c) shows the average distance between the tip of the consumable electrode 8 and the workpiece 7, that is, the average arc length La and the state of the workpiece 7 at each time. is there.

The average arc length is L1 from the start of welding to time t1. When passing through the step of the workpiece 7 at time t1, the average arc length sharply decreases to L2, and the distance between the tip of the consumable electrode 8 and the workpiece 7 is short, so that a short circuit is likely to occur. Then, the output signal Vd of the voltage detector 10 immediately decreases, but as shown in (a), the output signal Vda of the welding voltage smoothing circuit 11 actually used for control is a sufficiently smoothed value, and the change is slow. And the output signal Vud of the amplifier 14
Does not change much. Further, as shown in (b), the welding current Ia increases with an increase in the number of short circuits, but a sufficient melting of the consumable electrode 8 cannot be obtained because the arc time itself is short. As a result, it takes time t2 to return to the original arc length after climbing over the step as shown in FIG.

FIG. 9 shows the appearance of a bead and the amount of spatter generated when the bead passes through a step as shown in FIG. As shown in the figure, the number of short-circuits sharply increases at the time t1, and the spatters generated also increase rapidly, and the heat input of the welded portion is reduced, so that the bead appearance is greatly disturbed.

[0010]

Means for Solving the Problems A first invention of the present invention is:
In order to solve the above problems of the conventional method, using a consumable electrode, in a short-circuit transition type arc welding method in which welding is performed while repeating a short circuit and arc generation, the length of one arc generation period is detected, The output voltage of the welding power source in the next arcing period is reduced in proportion to the length of the detected arcing period, and the welding current in the next arcing period is inversely proportional to the length of one arcing period. The present invention proposes a short-circuit transfer type arc welding method for increasing or decreasing the number.

Further, a second invention of the present invention provides a short-circuit transition type arc welding method for performing welding while repeatedly performing short-circuiting and arc generation using a consumable electrode. In addition to setting a constant voltage lower than the output voltage of the welding power source during the occurrence period, the length of one arc occurrence period is detected, and the welding in the next arc occurrence period is proportional to the detected arc occurrence period. The present invention proposes a short-circuit transfer type arc welding method that reduces the output voltage of a power supply and increases or decreases the welding current in the next arc generation period in inverse proportion to the length of one arc generation period.

[0012]

FIG. 1 is a connection diagram showing an example of an apparatus for carrying out a short-circuit transfer type arc welding method according to the present invention. In the figure, reference numeral 18 denotes an output voltage corrector which receives an arc period signal Sad output from the arc period detector 15 as an input and outputs an output voltage correction signal Vms for the next arc period according to the length of the arc period. . 19 is a subtractor, which is a comparator 1
3, the output Vms of the output voltage corrector 18 is subtracted from the output ΔV, and the result is amplified to a level corresponding to the signal level of the output voltage setting device 16 for short-circuit period. In the figure, the other elements having the same functions as those of the conventional apparatus shown in FIG.

In FIG. 1, a voltage during welding is detected by a voltage detector 10 and smoothed by a welding voltage smoothing circuit 11 to obtain a detected voltage smoothed signal Vda which becomes an average voltage. The comparator 13 compares the welding voltage setting signal Vs output from the welding voltage setting circuit 12 with the detected voltage smoothing signal Vda, and outputs a difference signal Δ
Output V. Since a short circuit and an arc occur alternately during welding, the determination is made by the arc period detector 15, and a high-level arc period signal Sad is output during the arc period. The arc period signal Sad is counted by the output voltage corrector 18 and outputs an output voltage correction signal Vms having a magnitude corresponding to the duration of the arc period signal Sad. The output of the amplifier 14 that amplifies the output ΔV of the comparator 13 and the output voltage corrector 18
The output Vms is input to the subtractor 19 and becomes Vuh = A ・ ΔV−Vms. (However, A is a constant determined by the amplification factor of the amplifier 14)

During the arc period, the arc period signal Sad of the arc period detector 15 becomes high level, the signal switching circuit 17 is set to the (a) side, and the output signal Vuh of the subtractor 19 is selected. Conversely, during the short-circuit period, the arc period signal Sad of the arc period detector 15 becomes low level, and the signal switching circuit 1
7 is switched to the (b) side, and the output voltage setting device 1
6. The output voltage setting signal Vss of No. 6 is selected. The output command signal Sw1 thus selected is supplied to the power conversion circuit 2.

FIG. 2 shows a specific example of the output voltage corrector 18. In FIG. 2, MM1 and MM2 are monomultivibrators, which are triggered when the input signal falls and output short-width pulses. IG1 is an integrating circuit that integrates the output signal Sad of the arc period detector 15 and outputs it as a signal Sig, and is reset by the output signal of the monomultivibrator MM2. SH1 is a sample and hold circuit, and the input signal S
The output signal Sig of the integrating circuit IG1 for integrating the ad is input and the input signal at that time is stored when the output signal of the monomultivibrator MM1 rises, and then held and output until the output signal of the monomultivibrator MM1 rises. Output as a voltage correction signal Vms.

FIG. 3 is a timing chart showing the operation when the output voltage corrector shown in FIG. 2 is used in the apparatus shown in FIG.
3A shows the output signal of the voltage detector 10, that is, the instantaneous value Vd of the welding voltage, and FIG. 2B shows the output signal Vda of the welding voltage smoothing circuit 11 obtained by smoothing the instantaneous value Vd of the welding voltage. Show. (C) shows the output of the amplifier 14 that amplifies the output signal ΔV of the comparator 13 that compares the detected voltage smoothing signal Vda with the welding voltage setting value Vs, which is the output signal of the welding voltage setting circuit 12. (D) shows the output signal Sad of the arc period detector 15, (e) shows the output signal of the monomultivibrator MM1 of the output voltage corrector 18, and (f) shows the output of the monomultivibrator MM2 of the output voltage corrector 18. (G) shows the output signal of the integration circuit IG1 of the output voltage corrector 18, and (h) shows the output signal of the sample and hold circuit SH1 of the output voltage corrector 18, that is, the output voltage correction signal Vms. (I) is an output signal Vu of the subtracter 19 for subtracting the output voltage correction signal Vms from the output signal A · ΔV of the amplifier 14.
h and (j) are output command signals Sw1 of the signal switching circuit 17 for switching the output voltage setting signal to Vuh or the output voltage setting signal Vss during the short circuit period between the short circuit period and the arc period by the output signal Sad of the arc period detector 15. Is shown.

1 to 3, the welding voltage Vd is detected by a voltage detector 10 and the welding voltage smoothing circuit 1 is detected.
The average value Vda is derived at 1 and is compared with the set value Vs of the welding voltage setting circuit 12 at the comparator 13 to calculate the difference signal ΔV. On the other hand, the output of the voltage detector 10 is also supplied to the arc period detector 15, and when the signal Vd is higher than a predetermined value, it is determined that the arc period is present, and a high-level arc period signal Sad is output. The high level arc period signal Sad is integrated by the integration circuit IG1 of the output voltage corrector 18 to become an integration signal Sig, which is a sample and hold circuit SH1.
Is output to The output Sad of the arc period detector 15 is also supplied to the monomultivibrator MM1 of the output voltage compensator 18, and the monomultivibrator MM1 receives the falling of the input signal Sad, that is, a short pulse immediately after the end of the arc period. Output a signal. The pulse output of the mono multivibrator MM1 is supplied to the mono multivibrator MM2 and the sample hold circuit SH1, and the sample hold circuit SH1 is supplied to the mono multivibrator MM1.
The input signal Sig at the moment of the rising edge of the output signal is stored and output as the output voltage correction signal Vms. The monomultivibrator MM2 is triggered by the rising edge of the output signal of the monomultivibrator MM1, and outputs a short-time pulse signal. The integration circuit IG1 is reset by the falling edge of the output pulse of the monomultivibrator MM2, and the output signal is Returns to zero.

On the other hand, the output of the arc period detector 15 is also supplied to a signal switching circuit 17 so that the signal switching circuit 17 is activated when the arc period signal Sad is at a high level.
On the (a) side, when the arc period signal Sad is at the low level, the signal switching circuit 17 is switched to the (b) side. As a result,
The arc period signal Sad is output from the output voltage corrector 18 from the beginning of the arc generation period when the arc period signal Sad becomes high level.
When the arc period signal Sad is inverted to a low level at the end of the arc period, the output signal of the integration circuit IG1 at that moment is stored in the sample-and-hold circuit SH1, and then the monomultivibrator M
The integration circuit IG1 is reset by the output of the monomultivibrator MM2 due to the fall of the output pulse of M1, the output signal Sig returns to zero, and the next arc period starts and waits until the arc period signal Sad becomes high level. As a result, the length of one arc period is calculated by the integration circuit IG1 of the output voltage corrector 18, and this is calculated by the sample-and-hold circuit S at the end of the arc period.
It is stored in H1, is held until the end of the next arc period, and is output to the subtractor 19 as the output voltage correction signal Vms. The subtractor 19 subtracts the output signal Vms of the sample and hold circuit SH1 from the output signal of the amplifier 14, and Vuh = A
Obtain ΔV−Vms and output it to the signal switching circuit 17 as an output command signal during the arc period.

As described above, when the arc period is long, the output voltage correction signal Vms increases, the output signal Vuh of the subtractor 19 in the next arc period decreases, and the output voltage of the power conversion circuit 2 decreases. Conversely, when the arc period is short, the output voltage correction signal Vms decreases, the output signal Vuh of the subtractor 19 in the next arc period increases, and the output voltage of the power conversion circuit 2 increases.

FIG. 4 is a view schematically showing a state in which when the welding method of the present invention is carried out using the apparatus shown in FIG. is there. FIG. 5A shows the instantaneous value Vd of the welding voltage and the detected voltage smoothing signal Vda. (B) shows the instantaneous value Ia of the welding current and the average arc current Ida. (C) shows the change in the distance between the consumable electrode 8 and the workpiece 7, that is, the change in the average arc length La and the state of the workpiece 7. The average arc length is L1 from the start of welding to time t1. When passing through the step of the workpiece 7 at time t1, the average arc length sharply decreases to L2, and the distance between the tip of the consumable electrode 8 and the workpiece 7 is short, so that a short circuit is likely to occur. Then, the instantaneous value Vd of the welding voltage decreases as shown in FIG. On the other hand, since the actual detection voltage smoothing signal Vda is a sufficiently smoothed value, the change is slow and does not change much. However, since the number of short circuits increases and the arc time is shortened, the output voltage correction signal Vms is small in the negative direction, and the output signal Vuh of the subtractor 19 in the next arc period is reduced.
Has a large value, and the output voltage during the arc period increases. As a result, the arc current increases rapidly, and a sufficient amount of the consumable electrode melted can be obtained. As a result, as shown in (c), the consumable electrode 8 is rapidly melted, and the time required to return to the original arc length after climbing over the step is significantly reduced as compared with the conventional case.

FIG. 5 shows the appearance of the weld bead when passing through the step of the workpiece and the amount of spatter generated. As shown in the figure, the number of short-circuits sharply increases at the time t1 and the number of short-circuits increases, but spatters increase.However, the welding current sharply increases in inverse proportion to the decrease in the arc period, and the melting rate of the consumable electrode rapidly increases. Since the arc length recovers immediately, the period during which spatter occurs and the period during which the bead appearance is disturbed are shorter than those obtained by the conventional method.

[0022]

As described above, the short-circuit transfer type arc welding method of the present invention comprises:
As described above, even when the distance between the consumable electrode and the work to be welded changes suddenly, the amount of melting of the consumable electrode can be changed immediately to quickly return to an appropriate arc state.

[Brief description of the drawings]

FIG. 1 is a connection diagram showing an example of an apparatus for performing a short-circuit transfer type arc welding method of the present invention.

FIG. 2 is a connection diagram showing an embodiment of an output voltage corrector 18 used in the device of FIG.

FIG. 3 is a timing chart for explaining an operation when the output voltage corrector of FIG. 2 is used in the device of FIG. 1;

FIG. 4 is a schematic diagram showing a welding voltage, a welding current, and a positional relationship between a consumable electrode and an object to be welded over time when the short-circuit transfer type arc welding method of the present invention is performed by the apparatus of FIG. is there.

FIG. 5 is a diagram showing the appearance of a welding bead and the amount of spatter generated when the workpiece passes through a step when a short-circuit transfer type arc welding method of the present invention is carried out.

FIG. 6 is a connection diagram showing an example of an apparatus for performing a conventional short-circuit transfer type arc welding method.

FIG. 7 is a diagram for explaining the operation of the conventional device of FIG. 6;

8 is a schematic diagram showing the welding voltage, welding current, and the positional relationship between a consumable electrode and a workpiece to be welded over time when a conventional short-circuit transfer type arc welding method is performed by the apparatus of FIG. 6; .

9 is a diagram showing the appearance of a weld bead and the amount of spatter when passing through a step of a workpiece when the conventional short-circuit transfer type arc welding method is performed by the apparatus of FIG. 6;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Power conversion circuit 3 DC reactor 4 Welding torch 5 Motor 6 Feeding roll 7 Workpiece 8 Consumable electrode 9 Motor control circuit 10 Voltage detector for detecting instantaneous value Vd of welding voltage 11 Welding voltage smoothing circuit 12 Welding voltage setting circuit 13 comparator 14 amplifier 15 arc period detector 16 output voltage setting device for short circuit period 17 signal switching circuit 18 output voltage corrector 19 subtractor MM1 mono multivibrator MM2 mono multivibrator IG1 integration circuit SH1 sample hold circuit Vd Instantaneous value of welding voltage Vs Welding voltage setting value ΔV Difference signal between welding voltage setting value Vs and detection voltage smoothing signal Vda Sad Arc period signal Vss Output voltage setting signal during short circuit period Vda Detection voltage smoothing signal Vms Output voltage correction signal Vud Output signal of amplifier 14 Vuh Output signal of subtracter 19 Signal Sw1 Output command signal Sig Output signal of integrator IG1

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Kosaku Yamaguchi, Inventor 2-1-1-11 Tagawa, Yodogawa-ku, Osaka-shi Daihen Corporation (72) Inventor Hiroyasu Mizutori 2-1-1, Tagawa 2-chome, Yodogawa-ku, Osaka Inside Daihen

Claims (2)

[Claims] In a short-circuit transition type arc welding method in which welding is performed using a consumable electrode while repeating a short circuit and arc generation, the length of one arc generation period is detected, and the length of the detected arc generation period is determined. Short-circuit transition type arc that reduces the output voltage of the welding power source in the next arcing period in proportion to the length, and increases or decreases the welding current in the next arcing period in inverse proportion to the length of one arcing period Welding method. 2. An arc welding method using a consumable electrode, wherein welding is performed while repeating short-circuiting and arc generation, wherein the output voltage of the welding power source during the short-circuiting period is changed to the output voltage of the welding power source during the arcing period. While setting to a lower constant value, the length of one arcing period is detected, and the output voltage of the welding power source in the next arcing period is reduced in proportion to the length of the detected arcing period, A short-circuit transfer type arc welding method in which the welding current in the next arc generation period is increased or decreased in inverse proportion to the length of one arc generation period.